A mass surveillance operation has been unveiled as AT&T has been colluding with the NSA in actively tracking citizens. A detailed post by The Intercept on June 25th outlined the details of the operation, and the significance of the findings cannot be understated. The AT&T/NSA scandal could go down in history as one of the most extensive recorded incidences of mass surveillance. While previously reported, it has not been examined in detail or brought to the public attention on a widespread basis.
The story makes for grim reading. Essentially, AT&T has eight strategic buildings in the USA designed to spy on US civilians. The cooperation between AT&T and the NSA has been going on for many years and has only recently been uncovered. The infrastructure of AT&T made it ideal for the collection of data. A declassified 2011 court case indicated that the NSA had acquired 13 million internet transactions illegally in a single six month period. The issue is that the NSA is collecting data on everybody instead of collecting data on suspected individuals for national security, which is its intended purpose.
99% of the internet communication is transported through cables underneath the world's oceans, and a large proportion of this data is routed through the US. This is due to its geographic location. The reality is that much of the world's communication – phone calls, email, or chat – go through the USA.
Once on US soil, it is processed by American communications companies, AT&T is one of the largest and most accommodating to the NSA. The operation deployed by the NSA to use AT&T facilities for spying was called 'SAGURO'. AT&T helped the NSA to eavesdrop on internet data using the eight sites, which were connected to the major data routes of the world's communications.
AT&T communications were made accessible to the NSA through the XKEYSCORE tool. NSA employees use the tool to examine skype sessions, emails, instant messenger chats, web-browsing histories, web downloads and webcam photos.
The AT&T/NSA scandal is exactly the type that DLT intends to rectify. AT&T had access to data they should not have had, colluding with the NSA, a government entity. It is a prime example of a centralized corporation colluding with a centralized government agency. A violation of privacy and civil liberties seems to be the price paid for being a US citizen and a natural consequence of centralization. And there is the larger issue of the NSA spying on global citizens with this data, not just the USA.
A large segment of the world's communications runs through the AT&T infrastructure who feed this data directly to the NSA for the purposes of spying. Additionally, there is nothing more centralized than the underground internet cables that run underneath the world's oceans. A single point of failure for the world's technology has to be examined sooner rather than later.
Time and time again, centralization leads to catastrophe for citizens. There are countless examples of corruption, and decentralization of authority across all sectors remains the only alternative. We cannot continue to let both corporations and government infringe on civil liberties, and a decentralized economy powered by blockchain remains the only viable solution. It is a simple, obvious, and historically evident truth that the more power is centralized, the more it is abused.


where every week there'll be a topic to take a pic of yourself in.
My Boots are Sandler 'Studio' style ... 2011 Myers.
I only wear flats, so they're perfect for me with their gorge flat heel.
I have the same style in black suede, grey suede and black leather.
When I like something I tend to stock up.
These boots are all I wear, all winter long.
Bag = Made by Moi from my found object stash!
a large Tee shirt + cotton elastic waisted pants + a printed shirt!!
it was all there was other than trackies all day every day!!
I fell hard for TS too. It makes dressing soooo easy!
pretty!!!! The boots really pull the whole outfit together!


I found some fabulous treasures but my great heartbreak was that these colorful short boots were only a size 6.
Of course I had to try to fit my size 8 foot in to these but no luck. I did, however, find these amazing pointy toe Keds in my size and in nearly new condition for $3!
My favorite store of all was The Fine Art of Design – one of the most impressive vintage shops I have ever seen!
Those Ralph Lauren western palazzo pants ended up coming home with me. This shop was better than any candy store and I could have easily spent the rest of the day in there and forgotten all about the Coachella festival. They also have a great website for those of you who don't live close enough to visit the store.
These morning trips for coffee and thrift shopping made my whole Coachella trip much more fun. One of the things I love most about LA is that you can take a day or weekend trip to many different areas and feel like you are far away on vacation – the mountains, ocean and desert are all so close.


text:
Cooperative ImpactThe school for worldbuilders.
Social Innovation Conference
Sustainable solutions to social problems
This social innovation conference encourages New Jersey stakeholders to collaborate
We are a passionate movement of innovators, entrepreneurs, teachers, doctors, lawyers, government officials, and community members.
Why should you attend?
Liz Lempert
Mayor of Princeton, NJ
Liz has a collaborative leadership style that results in people working together to affect meaningful change. She builds on a movement of civic participation to reshape government.
Morgan Berman
MilkCrate
Forbes "30 Under 30", Top 10 Women to Watch by the United Nations Foundation, named a "Global Shaper" by the World Economic Forum, and the list goes on.
Christine Symington
Sustainable Princeton
Christine spent a decade climbing the ranks in the financial tech industry. Learn how she transitioned to the community, and secured funding to create employment for herself.
Mahan Rishi Singh
Mahan Rishi is an international teacher who has been leading retreats and yatras (spiritual pilgrimages) to India, Nepal and
Tibet over the past 25 years.
Jane Reagan
Jane is the co-founder of Along the Way, an organization providing informal services to women. Learn how she transitioned after 30 years in the pharmaceutical industry.
Laura Jordan
Laura is a recognized leader in cutting edge social enterprise and sustainability policy. She registered the first-ever benefit corporation in 2010, and is a "B Corp Champion" by B Labs.
Allison Sosna
Allison is the food entrepreneur known for "bringing more to the table". She is the founder of the MicroGreens nonprofit, and Principal of the Allison Sosna Group Benefit LLC.
Tineke Thio, PhD
Princeton Climate Change
Tineke is a climate communicator working to raise awareness of climate change and of solutions leading to climate resilience. She holds Ph.D. in physics from MIT.
Gery Juleff
Green Hour Radio
Gery served 25 years as a British diplomat where he led a team in London dealing with Climate Change, Renewable Energy Technology and Energy Security policy issue.
Nikki Rappaport
Cava Grill
Nikki is the creative director for the fast-casual restaurant from D.C. making its way to new cities. They partner with local nonprofits, food producers, and sustainable farms.
Leslie Burger
Executive Director, Princeton Public Library
Learn how she positions the library as the backbone of a civically engaged community and a place where social entrepreneurs find what they need to succeed.
Aria McKenna
The Global Cooling Project
Aria is an actress who figured out a way to use her art to make an impact on the world. Learn how she used a failed crowdfunding campaign to launch a social enterprise.
Joel Hammon
Princeton Learning Cooperative
Joel quit his stable and secure teaching job to co-found Princeton Learning Cooperative. He is helping to lead an international movement to re-imagine how we educate young people.
Devon Financial
James is a financial advisor specializing in managing assets through socially responsible investing. His clients are entrepreneurs and
the people who fund them.
Daniel DAlonzo
Cooperative Impact, Founder
Daniel is building a playbook for cultivating collaborative ecosystems in new cities across the nation. He brings creators and organizations together in a meaningful way.
Location of Conference
1200 Old Trenton Road West Windsor, NJ 08550
What is social innovation?
Social innovation is when we all work together to make the world a better place. It's that simple. We believe business can be used as a powerful vehicle for impact. We take a future-facing approach to change that comes from a place of possibility. We speak, act, and dream from the world we are creating. This empowers us to shape the emerging future with intention. Here's how we do it...
Cultivate empathy to deepen the relationship with yourself & others.
Sew yourself into the cultural fabric to identify unmet needs.
Co-create value to serve those unmet needs.
Attach a business model to the value to maximize impact.
Princeton Garden Theater

redpajama_set_name: RedPajamaCommonCrawl


text:
module.exports = shuffleArray;

function shuffleArray(array) {
  var currentIndex = array.length,
      temporaryValue,
      randomIndex;

  // While there remain elements to shuffle...
  while (0 !== currentIndex) {
    //Pick a remaining element
    randomIndex = Math.floor(Math.random() * currentIndex);
    currentIndex -= 1;
    // And swap it with the current element
    temporaryValue = array[currentIndex];
    array[currentIndex] = array[randomIndex];
    array[randomIndex] = temporaryValue;
  }

  return array;
}

redpajama_set_name: RedPajamaGithub


text:
Eucolpocephalum femorale är en insektsart som först beskrevs av Piaget 1880.  Eucolpocephalum femorale ingår i släktet Eucolpocephalum och familjen spolätare. Inga underarter finns listade i Catalogue of Life.

Källor

Spolätare
femorale

redpajama_set_name: RedPajamaWikipedia


Bot's creator Russel Neiss told IBTimes UK that Trump's tweets should take on "a greater importance".
As President Donald Trump's Twitter habits continue to raise eyebrows around the world, a new parody account is re-imagining the US leader's 140-character messages as official White House statements. Created by Jewish educator, technologist and coder Russel Neiss, the new Twitter bot - @RealPressSecBot - scans Trump's @realDonaldTrump account for new tweets every five minutes.
It then grabs a new direct quote and edits it to look like more traditional, official statements from the White House. After churning out the first 'statement' on Sunday (4 June), the account gained over 50,000 followers in less than 24 hours and has attracted more than 79,000 followers so far.
The bot's inaugural tweet featured Trump's tweet in which he called on lawmakers to "stop being politically correct and get down to the business of security for our people".
Since then, it has grabbed 12 tweets including one in which he criticised London Mayor Sadiq Khan and took one of his statements out of context.
"Pathetic excuse by London Mayor Sadiq Khan who had to think fast on his 'no reason to be alarmed' statement," Trump tweeted. "[Main Stream Media] is working hard to sell it."
Other tweets captured and refashioned as official tweets include his posts on the legal challenges against his controversial travel ban.
Neiss said the inspiration initially came from a viral tweet by Patrick Cunnane, an aide to former president Barack Obama, who tweeted a mockup of one of Trump's controversial tweets following the terror attacks in London as a statement from the Office of the Press Secretary.
"For context – because he's president – all of Trump's Tweets should be mocked up in the correct presidential statement format. It's telling," Cunnane tweeted on Sunday.
A tweet from Maggie Haberman, a White House correspondent for the New York Times, that said Trump's messages should be called statements also inspired him to create the bot.
Neiss said he wrote up a simple Python script to call Twitter's data tool REST API for the latest tweets from the account, check if it has been seen before and then take the text of the tweet to be reformatted into the 'statement' image. The image is then uploaded using more Python code and the twitter API.
The new Twitter bot also comes as White House aide Kellyanne Conway draws fierce criticism for characterising the media's coverage of Trump's tweets as an "obsession".
"It's become clear that the statements by the president's surrogates and press secretary don't always seem to jive with what he himself articulates publicly via his statements on Twitter," Neiss told IBTimes UK.
"As more folks realize that Twitter is the only platform that the President seems willing and able to share his unfiltered views, the statements from that platform ought to take on a greater importance. The bot merely gives them the platform that is befitting the highest office in the land."
This isn't first Twitter bot for Neiss either.
His previously viral, haunting Twitter bot tweeted the names, photos and heartbreaking fates of refugees who fled Nazi Germany in 1939 on the MS Louis - the German transatlantic liner that was denied entry into Cuba and the US and was forced to return to Europe.
The @Stl_Manifest Twitter account came after Trump signed the controversial travel ban barring travellers from six Muslim-majority countries from entering the US, suspending the entire US refugee programme and banning refugees fleeing the war in Syria from entering.
Many social media users praised the account as a great idea for presenting Trump's tweets as presidential tweets and giving them gravity. Others said they decided to unfollow Trump and White House Press Secretary Sean Spicer's account in lieu of @RealPressSecBot.
Some Twitter users even dubbed the bot a better alternative to Spicer.
"Given that the Press Secretary's formal statements from the podium are often contradicted mere hours afterward by POTUS's tweets, I don't think that's completely unfair," Neiss said.
He added that he would like to see people stop referring to Trump's posts on Twitter as mere tweets, but rather as "presidential statements on Twitter."
"Anecdotally that seems to now be happening with greater frequency," he said.
He knows words, he has the best words. This bot is the best ever.
Yes, @RealPressSecBot is the press secretary that America deserves & the one it needs right now!
It's such a great idea, because it gives the proper weight and context to what he says. It isn't "just Twitter" it's statements by POTUS.


text:
Gwrych Castle: the history of the new home of I'm A Celebrity, Get Me Out Of Here
Save 50% on a BBC History Magazine or BBC History Revealed subscription
We caught up with Dr Mark Baker, chairperson of the Gwrych Castle Preservation Trust, to find out more about the new UK home of the TV series I'm A Celebrity, Get Me Out Of Here, from royal ties to its haunted past…
By Elinor Evans
Gwrych Castle, a 19th-century country house near Abergele in North Wales, might be about to become one of the most famous historical sites of 2020, thanks to its new role as the home of ITV's I'm A Celebrity Get Me Out Of Here. But in the 1990s, the castle was fading fast, stripped of its wealth, crumbling and forgotten.
It was in this state that the site first caught the attention of Mark Baker, when he was 11 years old. His curiosity would lead him to establish the Gwrych Castle Preservation Trust – a charity dedicated to protecting the castle's heritage and history – all the more remarkable considering Baker was still just 12 years old.
"I used to pass it every day to and from school, and I would look up at the castle from my parents' car," explains Baker. "I witnessed it slowly disappearing into the hillside, into a mass of overgrowth. I began to notice there was light coming through parts of the building that hadn't done so before; the roof had been stolen, windows smashed and anything of value taken away." When Baker ventured up to the site, he found "a scene of devastation". The place had been ransacked by asset strippers, who took everything from its artwork to its fireplaces.
"I could see remnants of what had been there in terms of its former glory," Baker says. "There were still vestiges of the past, and it caught my imagination to try and rescue it."
From magnificent ruins to imposing forts: 10 must-visit British castles
Undaunted and helped by what Baker calls "the naivete of youth", he started to research the castle at the libraries at school and in the town of Abergele. "I came across so many discrepancies in the castle's narrative that no one really knew who owned it, or how old it was."
Curiosity in full gear, Baker wrote to Prime Minister Tony Blair and Prince Charles about the castle, ultimately meeting them to discuss what actions could be taken. "The Prince of Wales was most supportive and made an off-the-cuff comment that I should write a book about the castle and its history. So that's what I ended up doing, and I set up a charitable trust at the same time. That is how it all started."
Since his work setting up the trust, Baker completed his doctoral thesis on The Development of the Welsh Country House in 2015, and has worked with the National Trust and Welsh government agency Cadw on the preservation of historical sites.
Mark Baker was 12 when he set up the Gwrych Castle Preservation Trust – a charity dedicated to protecting the castle's heritage and history. (Image by Alamy)
The history of Gwrych Castle
The 19th-century castle embodies what has happened to many country houses in the 20th and early part of the 21st century, says Baker. "It was a private house that was requisitioned in the Second World War and then sold, as the family could not afford to repair it. Fortunately, the next owner was an entrepreneur who it opened as a tourist attraction. Sadly, like many of these vast properties, maintenance slipped and then it fell into disrepair."
There have been forts on the site since the Iron Age, when the hills around the castle were mined for lead and silver, also used by the Romans. During the 11th and 12th centuries, at a time when Wales was still a collection of different kingdoms, according to legend, Gwrych played its part in the defence against invading Norman and English forces. Owain ap Gruffydd(c1100–70), the king of Gwynedd and the first ruler known to have experimented with the title 'Prince of Wales', fortified Gwrych against the forces of King Henry II of England in the mid-12th century.
History explorer: The conquest of Wales
8 must-visit castles with Tudor connections
Later, during the 14th-century power struggle between ruling monarch Richard II and Henry Bolingbroke (whose father was John of Gaunt, fourth son of Edward III), the site would play a part in the royal history of the British Isles. Richard had refused to grant Bolingbroke the lands left to him by his father, and when the king returned to England following a campaign in Ireland in 1399, he was captured by Bolingbroke in the area near Gwrych Castle. Richard was forced to abdicate, and Bolingbroke assumed the throne, styling himself Henry IV.
The castle itself, completed in the 1820s by Lloyd Hesketh Bamford-Hesketh, has since been through many iterations. In the 1939, the castle housed 200 Jewish refugees from (then) Czechoslovakia during WW2. "They were on one of the last trains out of Nazi Germany before trains were diverted to go to the concentration camps," says Baker. "Gwrych really was a lifeline for all of those children. Most of them never saw their families again; you can't really underestimate how pivotal a role Gwrych Castle played in safeguarding their lives."
Remembering the Kindertransport
Operations such as the Kindertransport brought children (such as those pictured) out of countries occupied by the Nazis and to safe havens such as Gwrych. (Photo by Fox Photos/Getty Images)
In the 1970s, the castle became a medieval entertainment centre with attractions including jousting and banquets. "And then," says Baker, "it became a cause célèbre on how not to look after a historic building, when it became a ruin. It has hit these different points in the national consciousness. It's got an amazing story to tell, and amazing people attached to that story."
One of these figures in Gwrych's past is the Countess of Dundonald (1859–1924), a key player in a personal dispute that had a significant impact on the castle's history. Winifred, Countess of Dundonald, inherited Gwrych, the seat of the Bamford-Hesketh family on the death of her father in 1894. "Her family had lived there nearly a thousand years, in the earlier house," explains Baker. "And then Winifred's grandfather built the castle as a monument to their ancestors, the Lloyds of Gwrych."
A brief history of Wales: the resilient nation
The countess was, says Baker, "very ahead of her time". She was involved in the suffrage movement and a prominent patron of Welsh art, music and literature during the early 20th century, as well as an owner and manager of her own land at a time when this was rare for women.
"Unfortunately, she had quite an unhappy marriage," says Baker. This became significant when she tried to leave the castle to the nation in her will; when the countess died in 1924, Gwrych was left to King George V and the Prince of Wales.
"She was very publicly-minded and thought about what could be done to help the preservation of the castle in the long term. It was a great tragedy that her plans fell apart; her husband came out of the woodwork, not very pleased with how his wife had disinherited him, and he ultimately bought the castle back, which ruined her vision."
Countess of Dundonald (1859–1924), who inherited her grandfather's estate, had a significant impact on the castle's history. (Image by Wikimedia Commons)
Is Gwrych Castle haunted?
As the celebrities signed on for this year's series of I'm A Celebrity might be encouraged to discover, there are plenty of legends connected to the castle.
"In Wales, tales of myth and legend go back to the Mabinogion and Iron Age Wales," Baker explains, referring to the tales of Celtic mythology that were written in the 12th–13th centuries and based on older oral stories. "Gwrych Castle has all of these references in its history, as well as its own storytelling and myths," says Baker. "It's set of caves," he explains, "were often referred to as being 'the home of the fairy folk', and a way to access 'the Celtic other world'."
Ghosts and spirits are said to haunt the forests surrounding Gwrych. One 'Lady in Red', seen by champion boxer Randolph Turpin in the early 1950s whilst he was out training in the park, is said to be the ghost of the Countess of Dundonald. "The castle is a palimpsest – the ghosts add another layer to its rich history," says Baker. "There are people who are interested in life after death and whether there is another world beyond ours. This is part of mystique of Gwrych where the past merges with the present."
I'm A Celebrity, and the future of Gwrych Castle
The castle's new role as the UK home of ITV's I'm A Celebrity, says Baker, is "the next chapter in the thousand years of the castle's story.
"It is all about engaging people in new and innovative ways with their heritage. The filming demonstrates that historic places do not necessarily need to remain static as the narrative is constantly evolving with time. I really hope that I'm A Celebrity is an enabler for this process, so we can get more people coming to visit, to enjoy the place and also to learn to respect our historic assets.
In a world affected by the Covid-19 pandemic, it is a particularly welcome spotlight as many heritage properties in the UK struggle to adjust and survive. "We're in the middle of putting together a phase 1 application to the Heritage Lottery for a £10,000,000," says Baker, "The plan is that the castle will be reroofed and brought back into use, because what's really important to us as a grass roots charity is to provide opportunities for local people." The castle has a part to play, says Baker, in stemming the so-called "Brain Drain" from North Wales. "It would be amazing if we can play a role in preventing this. The estate has provided employment and fostered local talent for hundreds of years; we want to continue that trend and take it to the next chapter of history." Baker is even optimistic that the enhanced publicity and extra income for the site could lead to some of the assets that were stripped in the 1990s being identified and returned.
Gwrych Castle is the new UK home of ITV's 'I'm A Celebrity, Get Me Out Of Here'. (Image by ITV Studios)
The celebrities will be the first guests in a while to stay in the castle, and Baker is excited to see how they interact with the place (and also whether they get to see ghosts as well, adding that he hopes they will have a "nice time"). When its suggested that 'nice' isn't always what the producers of the show might have in mind, he laughs and says, "Okay, hopefully they will survive, and have fond memories".
Whatever the celebrities make of their stay at Gwrych, the opportunity presented by the show is a huge one. "A casual visit to historic sites such as the castle can often be an opportunity for people to become more engaged by igniting an interest," says Baker. "To know that's going to happen, through the prism of I'm A Celebrity, showing that we've got such a rich history every night on the TV for two or three weeks in November and December. It's incredibly exciting."
The new series of I'm A Celebrity, Get Me Out Of Here, is airing on ITV from Sunday 15 November 2020
Find out more about the Gwrych Castle Preservation Trust
How oceans shaped human civilisation
The real story of Bridgerton's Queen Charlotte: from glittering courts to tragic decline
A brief history of sea shanties
More on: Wales
Learn more about this subject
Save a huge 50% off a subscription to your favourite history magazine
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The 8 most famous royal weddings in British history
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Retaining the royals: why has the British monarchy survived – and thrived?


Below are forms that are required for enrolment in our programs.
For children entering child care, forms 1 and 2 must be completed with #4 as an option.
For FDK or Before and/or After child care, forms 1 and 3 must be completed with #4 as an option.
Please also visit our "Fees" and "Parent Handbook" tabs for further information.
Summer Camp registration is now open. The camp runs from July 2, 2019 through to August 23, 2019. Camp does not operate the last week of August as we prepare for our school age programs in September. Our camp allows you to pay for only the weeks you want to attend. FDK Summer Camp is $215/week. School Age Summer Camp is $205/week.
Once forms are completed, they can be emailed to rhouston@yorkchild.ca, faxed to 905-830-1454 or dropped off at our head office: 17310 Yonge Street, Unit 6, Newmarket (behind Ontario Early Years Centre).


text:
Лески () — село на Украине, находится в Хорошевском районе Житомирской области.

Население по переписи 2001 года составляет 63 человека. Почтовый индекс — 12125. Телефонный код — 4145. Занимает площадь 2,94 км².

Адрес местного совета
12125, Житомирская область, Хорошевский р-н, с. Зубринка, ул. Пушкина, тел.: 3-37-41

Ссылки
 Лески на сайте Верховной рады Украины

Населённые пункты Хорошевского района


text:
\section{Introduction}
\label{Introduction}

Due to the demands of modern electronics, semiconductor devices are
becoming smaller and faster, which means that applied external
fields cause strongly inhomogeneous and nonequilibrium processes in
such systems. A powerful approach to study dynamical properties of
potentially useful devices is to apply short (femto- or picosecond)
electric field pulses and to measure the response of the system.
Recent progress in ultrafast laser pulse experimental techniques
allows one to study the physical processes in such systems with a
very high precision (for a review, see e.g.
Refs.~\onlinecite{Onida,Rossi}). For example, with this technique
one can measure nonequilibrium energy and momentum distributions, or
the dynamics of excited states. Therefore, it is necessary to
develop theoretical tools to describe these experiments, as well as
to understand ultrafast processes in small semiconductor devices in
general.

The theoretical description of ultrafast phenomena triggered by
short-pulse laser fields is a complicated problem due to several
reasons. One of the most difficult tasks is to take into account
many-particle correlation effects properly. An external pulse field
causes the following main effects in the system: i) direct electron
photoemission; ii) inverse electron photoemission, and iii)
absorption processes. The first two phenomena can be described in
terms of free quasi-particles, which makes the problem relatively
simple. A proper description of optical absorption spectra is a much
more complicated task due to quasi-particle correlation effects. In
particular, external laser pulses can create excitons, or coupled
electron-hole pairs. The problem of correctly describing optical
absorption spectra with excitonic features in the case of applied
short-time laser pulses is one of the great challenges in condensed
matter physics.

For small devices in the presence of a short-pulse field typical
time scales are shorter than the Coulomb scattering time (see, for
example, Ref.~\onlinecite{Chemla}), which means that one cannot
treat the Coulomb interaction effects by using a simple Boltzmann
equation approach, where all the Coulomb effects are "hidden" in a
scattering time parameter $\tau$. Similarly, the semiconductor Bloch
equation (SBE) approach, \cite{Haug} based on the Hartree-Fock (HF)
approximation, and other mean-field methods have difficulties under
these circumstances, because of the presence of strong fluctuations.
In principle, Coulomb interaction effects can be taken into account
in a systematic way by using non-equilibrium Green function
techniques, \cite{Kadanoff_Baym,Keldysh} similar to the equilibrium
case. Unfortunately, this technique becomes numerically very
complicated in a strongly nonequilibrium situation, since in this
case the Green functions depend on two or more time arguments, which
puts high requirements on the computer memory size and makes the
numerical analysis very time-consuming.\cite{Onida,Dahlen}

In this paper, we discuss an alternative and potentially very
powerful approach to study these kinds of problems, based on
density-functional theory (DFT),\cite{Kohn} and in particular its
time-dependent generalization
(TDDFT).\cite{Runge_Gross,Gross,TDDFT_book} In this approach,
numerical calculations should be much less time-consuming compared
to the Green's function method. TDDFT has been successfully applied
to describe molecular excitations;\cite{Elliott} however, this
approach has some difficulties in describing extended
systems.\cite{Botti2} It is known that the standard local-density
approximation (LDA) and generalized gradient approximation (GGA) for
the DFT exchange-correlation (xc) potential cannot be applied to
describe some effects beyond the ground state properties in extended
systems, like the energy band gaps and excitonic effects in the
optical absorption spectra. Therefore, in order to apply TDDFT to
study ultrafast processes, and in particular to describe correctly
the optical absorption spectra in such systems, it is necessary to
find suitable xc potentials.

For weak and smooth external fields, such a potential can
constructed by using the many-body Bethe-Salpeter equation (BSE)
approach \cite{Reining,Marini,Botti}. In fact, in this case TDDFT
calculations with an xc potential extracted from the BSE give very
good results for the optical absorption spectra in a set of bulk
semiconductors. Unfortunately, the BSE-TDDFT approach cannot be used
directly to construct an xc potential for excitation with strong
short pulses, since here the linear response theory cannot be
applied, and the equations in time domain depend on many time
variables, which makes numerical solution extremely difficult to
obtain (similar to non-equilibrium Green's functions). Therefore, it
would be extremely useful to find a simple xc potential which will
allow one to use TDDFT straightforwardly to study the optical
response of a system in the time domain. It was shown in
Refs.~\onlinecite{Kim1,Kim2} that for smooth and weak fields such a
potential exists. Namely, the exact-exchange approximation for the
time-dependent optimized effective potential (XX-TDOEP) results in
optical absorption spectra with pronounced excitonic features, by
solving the problem in the frequency domain. Kim and
G\"orling~\cite{Kim1,Kim2} showed that the main reason for this was
the presence of $1/q^2$ Coulomb singularity in the exchange energy
kernel. The XX-TDOEP has recently been extended into the nonlinear,
real-time domain for simple quasi-one-dimensional quantum well
systems.\cite{Wijewardane2}

The purpose of this paper is twofold: 1) we will formulate a general
TDDFT approach to study optical interband excitations in terms of
the Kohn-Sham density matrix. The corresponding system of equations
has the formal simplicity of the SBEs, which allows one to solve it
directly in the time domain, contrary to the many-body Green
function approach, where it is difficult to treat the problem
numerically. At the same time, this approach has a great formal
advantage in comparison with the SBE formalism, since in TDDFT the
Coulomb interaction effects are treated in principle exactly. 2) We
will show that by using simple exchange-only functionals, the
essence of excitonic features can be captured in a relatively simple
manner. As an example, we consider the model of a three-dimensional
two-band bulk insulator for different local xc potentials and show
that its optical absorption spectra contain qualitatively correct
excitonic features, whenever the xc energy kernel has a $1/q^{2}$
singularity.

The paper is organized as follows: We introduce a general TDDFT-SBE
formalism in terms of the Kohn-Sham density matrix in
Section~\ref{Formalism}. In Section~\ref{3D}, we derive the
TDDFT-SBE formalism and in Section~\ref{Results} we apply this
formalism to study the optical absorption spectra for a
three-dimensional two-band model insulator with different xc
potentials and compare the results with HF. Conclusions are
presented in Section~\ref{Conclusions}. Some technical details are
given in Appendix.

We use Hartree atomic units ($e^2=m=\hbar =1$) throughout the paper.

\section{General formalism}
\label{Formalism}

The general DFT Hamiltonian for a many-electron system in a solid
(in the Born-Oppenheimer approximation) can be written in the
following form:
\begin{equation}
{\hat H}=-\frac{{\bf \nabla}^{2}}{2}+V_{nucl}({\bf r})+V_{H}[n]({\bf
r}) +V_{xc}[n]({\bf r}), \label{Hamiltonian}
\end{equation}
where $V_{nucl}({\bf r})$ is the nuclear potential for the electrons
and
\begin{equation}
V_{H}[n]({\bf r})=\int d{\bf r}'\frac{n({\bf r}')}{|{\bf r}-{\bf
r}'|} \label{VH}
\end{equation}
is the Hartree potential, where $n({\bf r})$ is the density of
electrons. All many-body effects beyond Hartree are described by the
scalar xc potential $V_{xc}[n]({\bf r})$. In particular, in the LDA
exchange-only case:
\begin{equation}
V_{xLDA}(n({\bf r})) = -\left(\frac{3}{\pi}
\right)^{1/3}n^{1/3}({\bf r}). \label{VLDA}
\end{equation}

In order to describe the ground-state properties of the system
governed by the Hamiltonian Eq.~(\ref{Hamiltonian}), one solves the
stationary Kohn-Sham (KS) equation
\begin{equation}
{\hat H}({\bf r})\psi_{{\bf k}}^{l_{i}}({\bf r})=\varepsilon_{{\bf
k}}^{l_{i}}\psi_{{\bf k}}^{l_{i}}({\bf r}), \label{Schroedinger}
\end{equation}
and find bands $l_{i}$ with spectra $\varepsilon_{{\bf k}}^{l_{i}}$,
where ${\bf k}$ is the crystal momentum and $l_{i}=v_{i},c_{i}
(i=1,2,...)$ are the labels for the valence ($v$) and conduction
($c$) bands. The electron density can be found self-consistently:
\begin{equation}
n({\bf r})=2\sum_{i,{\bf k}}|\psi_{{\bf k}}^{v_{i}}({\bf
r})|^{2}\theta (\varepsilon_{F}-\varepsilon_{{\bf k}}^{v_{i}}),
\label{n2}
\end{equation}
where $\varepsilon_{F}$ is the Fermi energy and the summation is
performed over the occupied (valence) band states.
Equation~(\ref{n2}) is valid in the case of zero temperature, which
we consider in this paper. Finite temperatures would require
introduction of the Fermi distribution function into Eq.~(\ref{n2}).

In order to study the nonequilibrium case when an external electric
field ${\bf E}(t)$ is switched on at time $t=t_{0}$, the Hamiltonian
Eq.~(\ref{Hamiltonian}) must be modified in the standard way: an
external electromagnetic vector potential ${\bf A}_{ext}({\bf r},t)$
should be added by making the usual substitution ${\bf
\nabla}\rightarrow {\bf \nabla}-(i/c){\bf A}_{ext}({\bf r},t)$ and
by adding a scalar potential term $\varphi_{ext}({\bf r},t)$ to the
Hamiltonian. The electric field is connected with $\varphi_{ext}
({\bf r},t)$ and ${\bf A}_{ext} ({\bf r},t)$ in the following way:
\begin{equation}
{\bf E}({\bf r},t)=-{\bf \nabla}\varphi_{ext}({\bf r},t)
-\frac{1}{c}\frac{\partial {\bf A}_{ext}({\bf r},t)}{\partial t}.
\label{E}
\end{equation}
For an extended system one needs to preserve the periodicity,
therefore the vector external potential must be used. This makes the
problem technically more complicated in comparison to scalar
potentials. However, it can be shown that in situations when the
characteristic field frequency is bigger than the level spacing, one
can work with scalar potentials instead of vector potentials (see,
for example, Ref.~\onlinecite{Schafer}). Therefore, we shall
consider the case when ${\bf A}_{ext}({\bf r},t)=0$, and for
simplicity assume that the electric field is space-independent.
Strictly speaking, for external homogeneous fields one needs to use
current-TDDFT in order to study the response of the
system.\cite{Maitra,vanFaassen} One then gets the macroscopic
current, which allows one to satisfy the periodicity condition. In
this paper, however, we use the usual approximation\cite{Haug} where
the external homogeneous electric field is described by the
following scalar potential:
\begin{equation}
\varphi_{ext}({\bf r},t)=-{\bf E}(t){\bf r}. \label{varphiext}
\end{equation}

Due to the presence of an electric field, the Hamiltonian is
explicitly time-dependent. Moreover, the Hartree and xc potential
terms in the Hamiltonian become also time-dependent. Such a
time-dependent problem is described by the time-dependent KS
equation:
\begin{equation}
i\frac{\partial }{\partial t}\Psi ({\bf r},t)={\hat H}({\bf
r},t)\Psi ({\bf r},t). \label{Schroedinger2}
\end{equation}
In the adiabatic approximation, which we use in this paper, the xc
potential can be formally obtained from the stationary potentials by
assuming that the electron density becomes time-dependent, $n({\bf
r})\rightarrow n({\bf r},t)$. Eq.~(\ref{Schroedinger2}) must be
solved self-consistently together with the corresponding
time-dependent particle number equation (\ref{n2}). Since the
initially occupied states are the valence states $\psi_{{\bf
k}}^{v_{i}}({\bf r})$, described by the band index $v^{i}$ and the
momentum ${\bf k}$, the evolution of the system can be completely
described by the time-evolution of these states, i.e. by finding the
corresponding time-dependent wave functions $\Psi_{{\bf
k}}^{v_{i}}({\bf r},t)$, such that $\Psi_{{\bf k}}^{v_{i}}({\bf
r},t_{0})=\psi_{{\bf k}}^{v_{i}}({\bf r})$, from
Eq.~(\ref{Schroedinger2}) and a time-dependent generalization of
Eq.~(\ref{n2}):
\begin{equation}
n({\bf r},t)=2\sum_{i,{\bf k}}|\Psi_{{\bf k}}^{v_{i}}({\bf
r},t)|^{2}\theta (\varepsilon_{F}-\varepsilon_{{\bf k}}^{v_{i}}).
\label{n3}
\end{equation}

In the following, we express the time-dependent wave functions as
linear combinations of the ground-state wave functions:
\begin{eqnarray}
\Psi_{{\bf k}}^{v_{i}}({\bf r},t)=\sum_{j,{\bf q}}\left[ c_{{\bf
k}{\bf q}}^{v_{i}v_{j}}(t)\psi_{{\bf q}}^{v_{j}}({\bf r}) +c_{{\bf
k}{\bf q}}^{v_{i}c_{j}}(t)\psi_{{\bf q}}^{c_{j}}({\bf r}) \right] ,
\label{psi}
\end{eqnarray}
where $c_{{\bf k}{\bf q}}^{v_{i}l_{j}}(t)$ are momentum and
time-dependent complex coefficients, which satisfy the following
initial condition: $c_{{\bf k}{\bf q}}^{v_{i}l_{j}}(t_{0})=\delta_
{{\bf k}{\bf q}}\delta_{v_{i}l_{j}}e^{-i\varepsilon_{{\bf
k}}^{v_{i}}t_{0}}$. The time evolution of the system can thus be
found by determining the coefficients $c_{{\bf k}{\bf
q}}^{v_{i}v_{j}}(t)$ and $c_{{\bf k}{\bf q}}^{v_{i}c_{j}}(t)$ for
Eq.~(\ref{psi}). However, in order to solve the problem, it is more
convenient to introduce the density matrix: $\rho_{{\bf k};{\bf
q}{\bf p}}^{v_{i};l_{m}{\bar l}_{n}}(t)=c_{{\bf k}{\bf
q}}^{v_{i}l_{m}}(t) \left[ c_{{\bf k}{\bf p}}^{v_{i}{\bar
l}_{n}}(t)\right] ^{*}$, which is useful for defining physical
quantities like occupation of the states and optical transitions
(see next Section). TDDFT in the density-matrix representation is a
method which allows one to solve the problem in principle exactly,
since it is an exact reformulation of the time-dependent Kohn-Sham
formalism. This method was already introduced to study intersubband
processes in quantum wells\cite{Wijewardane} and the electrical
conductivity in dissipative models of molecular devices\cite{Burke}
(see also Ref.~\onlinecite{Berman}, where a similar approach was
discussed). Here we develop a technique which can be applied in more
general cases with a continuous electron spectrum, including
interband transitions in solids.

The density matrix satisfies the following equation of motion:
\begin{equation}
i\frac{\partial}{\partial t}\rho_{{\bf k};{\bf q}{\bf
p}}^{v_{i};l_{m}l_{n}'}(t)=[H(t),\rho ]_{{\bf k};{\bf q}{\bf
p}}^{v_{i};l_{m}l_{n}'} = \sum_{l_{j}'',{\bf q}'}\left[ H_{{\bf
q}{\bf q}'}^{l_{m}l_{j}''}(t)\rho_{{\bf k};{\bf q}'{\bf
p}}^{v_{i};l_{j}''l_{n}'}(t) - \rho_{{\bf k};{\bf q}{\bf
q}'}^{v_{i};l_{m}l_{j}''}(t)H_{{\bf q}'{\bf p}}^{l_{j}''l_{n}'}(t)
 \right] , \label{Liouville}
\end{equation}
where the Hamiltonian matrix elements $H_{{\bf k}{\bf
q}}^{l_{m}{\bar l}_{n}}(t)$ are
\begin{equation}
H_{{\bf k}{\bf q}}^{l_{m}l_{n}'}(t)=\int_{cell} d{\bf r} \psi_{{\bf
k}}^{l_{m}*}({\bf r}) H(t)\psi_{{\bf q}}^{l_{n}'}({\bf r})
=\varepsilon_{{\bf k}}^{l_{m}}\delta_{l_{m}l_{n}'}+{\bf E}(t){\bf
d}_{{\bf k}{\bf q}}^{l_{m}l_{n}'} +V_{H{\bf k}{\bf
q}}^{l_{m}l_{n}'}(t)+V _{xc{\bf k}{\bf q}}^{l_{m}l_{n}'}(t),
\label{Hamiltonianme}
\end{equation}
and the space integration is performed over a unit cell. In
Eq.~(\ref{Hamiltonianme}),
\begin{equation}
{\bf d}_{{\bf k}{\bf q}}^{l_{m}l_{n}'} = \int_{cell} d{\bf r}
\psi_{{\bf k}}^{l_{m}*}({\bf r}) {\bf r}\psi_{{\bf q}}^{l_{n}'}({\bf
r}) \label{dipole}
\end{equation}
are the dipole matrix elements, and $V_{H{\bf k}{\bf q}}^{l_{m}
l_{n}'}(t)$ and $V _{xc{\bf k}{\bf q}}^{l_{m}l_{n}'}(t)$ are the
matrix elements for the difference between the time-dependent and
ground state (at $t\leq t_{0}$) Hartree and xc potentials:
\begin{equation}
V_{H{\bf k}{\bf q}}^{l_{m}l_{n}'}(t) = \int_{cell} d{\bf r}
\psi_{{\bf k}}^{l_{m}*}({\bf r}) \left[ V_{H}[n]({\bf r},t)
-V_{H}[n]({\bf r},t_{0})\right]\psi_{{\bf q}}^{l_{n}'}({\bf
r}),\label{VHlm}
\end{equation}
and similar for $ V_{xc{\bf k}{\bf q}}^{l_{m}l_{n}'}(t)$. The
density matrix satisfies the following initial condition:
\begin{equation}
\rho_{{\bf k};{\bf q}{\bf p}}^{v_{i};l_{m}l_{n}'}(t_{0})=
\delta_{{\bf k}{\bf q}}\delta_{{\bf k}{\bf
p}}\delta_{v_{i}l_{m}}\delta_{v_{i}l_{n}'}, \label{Liouvillet0}
\end{equation}
which corresponds to the situation where all states in the valence
bands are initially occupied. The particle density (\ref{n3}) has
the following form in terms of the density matrix elements:
\begin{equation}
n({\bf r},t)=2\sum_{i,l_{m},l_{n}',{\bf k},{\bf q},{\bf p}}
\rho_{{\bf k},{\bf q},{\bf p}}^{v_{i};l_{m}l_{n}'}(t) \psi_{{\bf
p}}^{l_{n}'*}({\bf r}) \psi_{{\bf q}}^{l_{m}}({\bf r}) \theta
(\varepsilon_{F}-\varepsilon_{{\bf k}}^{v_{i}}). \label{nrho}
\end{equation}
Solution of the Liouville-von Neumann equation (\ref{Liouville})
allows one to study physical properties of the system. In
particular, one can find the polarization as
\begin{equation}
{\bf D}(t)=\sum_{i,l_{m},l_{n}',{\bf k},{\bf q},{\bf p}} \rho_{{\bf
k};{\bf q}{\bf p}}^{v_{i};l_{m}l_{n}'}(t) {\bf d}_{{\bf p}{\bf
q}}^{l_{n}'l_{m}}.
 \label{polarization}
\end{equation}

Below, we shall use this formalism to study the optical response of
a three-dimensional two-band insulator, by solving
Eqs.~(\ref{Liouville}) and (\ref{Liouvillet0}) using different xc
potentials.

\section{Three-dimensional two-band model}
\label{3D}

In general, it is very difficult to find the solution of the density
matrix equation (\ref{Liouville}) and one needs to make some
approximations. For simplicity, we shall consider the optical
absorption spectra of systems composed of one valence and one
conduction band: $l_{1}=v$, $l_{2}=c$. This approximation can be
used if one assumes that the dominant optical transitions in the
system take place from the highest occupied valence band to the
lowest conduction band. Since the main aim of this paper is a {\it
proof of principle} that TDDFT can describe excitonic effects in
semiconductors triggered by short laser pulses, such an
approximation is sufficient. However, for real systems one needs to
take into account the band structure of the materials more
accurately. Another simplification comes from the fact that in the
dipole approximation for the external field, the optical transitions
in the system take place with zero photon momentum. The coefficients
$c$, defined in Eq.~(\ref{psi}), then depend on one momentum
variable only:
\begin{eqnarray}
c_{{\bf k}{\bf q}}^{vv}(t)=\delta_{{\bf k}{\bf q}}c_{{\bf
k}}^{vv}(t), \ \ \ \ c_{{\bf k}{\bf q}}^{vc}(t)=\delta_{{\bf k}{\bf
q}}c_{{\bf k}}^{vc}(t).
 \label{clm}
\end{eqnarray}
The problem is thus reduced to finding the density matrix of rank 2,
with elements $\rho_{{\bf k}}^{vv}(t)$, $\rho_{{\bf
 k}}^{vc}(t)$, $\rho_{{\bf k}}^{cv}(t)$ and $\rho_{{\bf
 k}}^{cc}(t)$, which are functions of momentum and time.
The elements $\rho_{{\bf k}}^{vv}(t)$ and $\rho_{{\bf
 k}}^{cc}(t)$ describe the occupancy of the valence and conduction band states, and
$\rho_{{\bf
 k}}^{vc}(t)$ and $\rho_{{\bf k}}^{cv}(t)$ describe the polarization in
 the system. These four elements are not independent.
 Particle conservation number requires $\rho_{{\bf k}}^{vv}(t)+\rho_{{\bf
 k}}^{cc}(t)=1$, and by definition, $\rho_{{\bf
 k}}^{cv}(t)=\rho_{{\bf k}}^{vc*}(t)$.

From Eq.~(\ref{Liouville}), one can obtain the following system of
equations for
 two independent components $\rho_{{\bf k}}^{vv}(t)$ and $\rho_{{\bf
 k}}^{vc}(t)$:
\begin{eqnarray}
\frac{\partial}{\partial t}\rho_{{\bf k}}^{vv}(t) = &-&2{\rm
Im}\left[ (E(t)d_{\bf k}^{cv}+V_{H{\bf k}}^{cv}+V_{xc{\bf k}}^{cv} )
\rho_{{\bf k}}^{vc}(t)\right] , \label{rhovv}
\\
\frac{\partial}{\partial t}\rho_{{\bf k}}^{vc}(t)=
&-&i[\varepsilon_{\bf k}^{v}-\varepsilon_{\bf k}^{c}] \rho_{{\bf
k}}^{vc}(t) -i [\rho_{{\bf k}}^{cc}(t)-\rho_{{\bf k}}^{vv}(t)]
E(t)d_{\bf k}^{vc}
\nonumber \\
&-i&[\rho_{{\bf k}}^{cc}(t)-\rho_{{\bf k}}^{vv}(t)] (V_{H{\bf
k}}^{vc}(t)+V_{xc{\bf k}}^{vc}(t)) -i[V_{H{\bf k}}^{vv}(t)+V_{xc{\bf
k}}^{vv}(t) -V_{H{\bf k}}^{cc}(t)-V_{xc{\bf k}}^{cc}(t) ]\rho_{{\bf
k}}^{vc}(t).\nonumber \\
\label{rhovc}
\end{eqnarray}
This system represents the TDDFT version of the well-known
SBEs,\cite{Haug} which are used to study the optical properties of
bulk semiconductors subject to external electric fields.
Equations~(\ref{rhovv}), (\ref{rhovc}) have a more general form,
since here the Coulomb interaction effects are taken into account in
principle exactly by means of the matrix elements of $V_{xc}[n]({\bf
r},t)$. As mentioned in the Introduction, this is important in the
case of small systems and sharp pulses, where the characteristic
times in the system are shorter than the Coulomb scattering time,
and where it is difficult to treat the Coulomb interaction effects
properly within the BSE approach.

We shall study the solution of Eqs.~(\ref{rhovv}) and (\ref{rhovc})
for the simple but instructive example of a two-band model on a
cubic lattice. We assume that the solution of
Eq.~(\ref{Schroedinger}) with the Hamiltonian
Eq.~(\ref{Hamiltonian}) gives the following simple dispersions:
\begin{equation}
\varepsilon_{{\bf k}}^{v} =\varepsilon_{0}^{v}+2t^{v} [\cos
(a_{0}k_{x})+\cos (a_{0}k_{y})+\cos (a_{0}k_{z})],
 \label{epskv}
\end{equation}
\begin{equation}
\varepsilon_{{\bf k}}^{c} =\varepsilon_{0}^{c}-2t^{c} [\cos
(a_{0}k_{x})+\cos (a_{0}k_{y})+\cos (a_{0}k_{z})],
 \label{epskc}
\end{equation}
where $a_{0}$ is the lattice constant. For definiteness, we consider
a model of solid hydrogen and assume that the difference of
$\varepsilon_{0}^{c}$ and $\varepsilon_{0}^{v}$ can be set
proportional to the first two hydrogen energy levels
$E=-1/[2a_{B}n^{2}], n=1,2$. In the last equation,
$a_{B}=\hbar^{2}/me^{2}=1$ is the Bohr radius, which is used as the
length unit in this paper. It is assumed that the band parameters
$t_{v}$ and $t_{c}$ are much smaller than
$\varepsilon_{0}^{c}-\varepsilon_{0}^{v}$, i.e. the bands are
non-overlapping.

The valence and conduction band wave functions in the Bloch
representation
\begin{eqnarray}
\psi_{{\bf k}}^{v}({\bf
r})=e^{i{\bf k}{\bf r}}u_{{\bf k}}^{v}({\bf r})
, \label{psiv_Bloch} \\
\psi_{{\bf k}}^{c}({\bf r})=e^{i{\bf k}{\bf r}}u_{{\bf k}}^{c}({\bf
r}), \label{psic_Bloch}
\end{eqnarray}
can be represented as linear combinations of Wannier functions
$w^{v}({\bf r})$ and $w^{c}({\bf r})$. In fact, one can use for
spatially periodic Bloch functions $u_{{\bf k}}^{v}({\bf r})$ and
$u_{{\bf k}}^{v}({\bf r})$ the following representation:
\begin{eqnarray}
u_{{\bf k}}^{v}({\bf r})=\sum_{{\bf L}}e^{i{\bf k}({\bf r}-{\bf L})}
w^{v}({\bf r}-{\bf L}) \label{psiv}
\end{eqnarray}
and similar for $u_{{\bf k}}^{c}({\bf r})$, where ${\bf
L}=a_{0}(n_{x},n_{y},n_{z})$ are the cell vectors.

Unfortunately, it is difficult to find the exact expressions for the
Wannier functions, and hence for the Bloch functions, even for such
a simple three-dimensional system. For simplicity, we choose the
Wannier functions to be equal to the $1s^{0}$ and $2p^{0}$ hydrogen
wave functions:
\begin{eqnarray}
w^{v}({\bf r})&=&\frac{1}{\sqrt{\pi}} e^{-r}
, \label{wv} \\
w^{c}({\bf r})&=&\frac{1}{4\sqrt{2\pi}} e^{-r/2}z. \label{wc}
\end{eqnarray}
This choice of the Wannier functions is an approximation, since the
orthogonality condition on different sites $\int d{\bf r}w^{l*}({\bf
r}-{\bf L}_{1}) w^{m}({\bf r}-{\bf L}_{2})=\delta^{lm}\delta_{{\bf
L}_{1}{\bf L}_{2}}$ is violated. However, when the lattice parameter
$a_{0}$ is much larger than the Bohr radius, $a_{B}<<a_{0}$, the
requirement of orthogonality is satisfied with a very high
precision, since the overlap between different sites becomes
negligible. In our calculations, we shall use the lattice constant
values $a_{0}=10$ and $20$.

In the next section, we shall study the solution of
Eqs.~(\ref{rhovv}) and (\ref{rhovc}) when an external short pulse
field
\begin{eqnarray}
{\bf E}(t)={\bf E}_{0}e^{-t^{2}/\tau^{2}} \label{electricfield}
\end{eqnarray}
with $\tau\sim 1-10{\rm fs}$ is applied. This will allow us to find
the optical absorption spectrum $A(\omega )$ of the system, which is
defined by the real part of the ratio of the Fourier transforms of
the total polarization
\begin{eqnarray}
P(\omega )=i(4\pi
/\sqrt{\epsilon_{b}})(\varepsilon_{0}^{c}-\varepsilon_{0}^{v})|d^{cv}|^{2}a_{0}^{3}\int
\frac{d{\bf k}}{(2\pi )^3}\int dt e^{i\omega t}\rho_{{\bf k}}^{vc}
(t) \label{P}
\end{eqnarray}
 and the pulse field
$E(\omega )$:
\begin{equation}
A(\omega)=-2{\rm Re}[P(\omega )/E(\omega)] .
 \label{Absorption}
\end{equation}

\section{Results and discussion}
\label{Results}

\subsection{Hartree-Fock}
\label{Hartree-Focksection}

Before proceeding with the solution of the TDDFT equations
(\ref{rhovv}), (\ref{rhovc}) for different xc potentials, we briefly
discuss the case of the Hartree-Fock potential for the two-band
model presented above. Hartree-Fock is the most widely used
approximation in the SBE theory\cite{Haug} for the study of optical
absorption spectra in bulk systems and heterostructures subject to
both smooth and pulsed external fields (see, for example,
Refs.~\onlinecite{Maslov1,Maslov2}).

In the time-dependent Hartree-Fock approximation, the total electron
wave function satisfies the following equation:
\begin{eqnarray}
i\frac{\partial \Psi_{{\bf k}}^{v}({\bf r},t)}{\partial t}
=&~&\left[ -\frac{{\bf \nabla}^{2}}{2}-{\bf E}(t){\bf r}+\int d{\bf
r}'\frac{\sum_{{\bf q}}\Psi_{{\bf q}}^{v*}({\bf r}',t)\Psi_{{\bf
q}}^{v}({\bf r}',t)}{|{\bf r}-{\bf r}'|}\right] \Psi_{{\bf
k}}^{v}({\bf r},t)
\nonumber \\
&-&\int d{\bf r}'\frac{\sum_{{\bf q}}\Psi_{{\bf q}}^{v*}({\bf
r}',t)\Psi_{{\bf q}}^{v}({\bf r},t)}{|{\bf r}-{\bf r}'|} \Psi_{{\bf
k}}^{v}({\bf r}',t). \label{HF}
\end{eqnarray}
Applying the analysis presented in Section \ref{Formalism} [see
Eqs.~(\ref{psi})-(\ref{nrho})], it is possible to show that
Eq.~(\ref{HF}) is equivalent to the system of TDDFT density-matrix
equations (\ref{rhovv}), (\ref{rhovc}) with corresponding matrix
elements for the Hartree and Hartree-Fock potentials. Namely, the
Hartree potential matrix elements are:
\begin{eqnarray}
V_{H{\bf k}}^{lm}(t)=\sum_{n,s=v,c;{\bf q}}I_{H}^{lmns}({\bf k},{\bf
q})\rho_{{\bf q}}^{sn}(t), \label{VH}
\end{eqnarray}
where
\begin{eqnarray}
I_{H}^{lmns}({\bf k},{\bf q})=\int d{\bf r}\int d{\bf r}' \psi_{{\bf
k}}^{l*}({\bf r})\psi_{{\bf k}}^{m}({\bf r}) \frac{\psi_{{\bf
q}}^{n*}({\bf r}')\psi_{{\bf q}}^{s}({\bf r}')}{|{\bf r}-{\bf r}'|}.
\label{IH}
\end{eqnarray}
From Eqs.~(\ref{VH}), (\ref{IH}), one can find the following
approximate expression for the Hartree matrix elements:
\begin{eqnarray}
V_{H{\bf k}}^{lm}(t)= \delta^{lm}V({\bf G}\rightarrow {\bf 0}) +
\sum_{n,s=v,c;{\bf q}} A^{lmns}a_{0}^{3}\int \frac{d{\bf q}}{(2\pi
)^{3}}\rho_{{\bf q}}^{sn}(t)+..., \label{VH2}
\end{eqnarray}
where $V({\bf q})$ is the Fourier transform of the Coulomb potential
$1/|{\bf r}-{\bf r}'|$, ${\bf G}$ is a reciprocal lattice vector and
\begin{eqnarray}
A^{lmns}=\sum_{{\bf G}\not= {\bf 0}}V({\bf G}) \int d{\bf r}
w^{l*}({\bf r})e^{-i{\bf G}{\bf r}}w^{m}({\bf r}) \int d{\bf r}'
w^{n}({\bf r}')e^{i{\bf G}{\bf r}'}w^{s}({\bf r}') \label{A}
\end{eqnarray}
(details of a similar analysis can be found in
Ref.~\onlinecite{Schafer}). In Eq.~(\ref{VH2}), the dots correspond
to the terms proportional to integrals over products of Wannier
functions which reside on different sites [$\sim \int d{\bf r}
w^{l*}({\bf r})w^{m}({\bf r}-{\bf L})$]. These terms are negligible
due to a small overlap of the Wannier functions on different sites
[when $a_{B}\ll a_{0}$, see Eqs.~(\ref{wv}) and (\ref{wc})].
Moreover, the presence of oscillating functions $\exp [-i{\bf G}{\bf
r}]$ and $\exp [i{\bf G}{\bf r}']$ under the integrals in the
expression for the coefficients $A^{lmns}$, Eq.~(\ref{A}), makes the
terms proportional to $A^{lmns}$ much smaller than the first term in
Eq.~(\ref{VH2}). Therefore, the second term in Eq.~(\ref{VH2}) can
be also neglected. Substitution of the remaining term
$\delta^{lm}V({\bf G}\rightarrow {\bf 0})$ into
Eqs.~({\ref{rhovv}}),(\ref{rhovc}) simply causes a constant shift of
the overall potential and can be ignored. Therefore, the Hartree
term does not contribute to the density-matrix equations
({\ref{rhovv}}),(\ref{rhovc}) in this approximation, and we shall
ignore it from now on. It is possible to show \cite{Schafer} that
higher order terms in Eq.~(\ref{VH2}), which we neglect, lead to a
small renormalization of the energy bands and the electric field
time dependence.

In a similar way, one can find an approximate expression for the
matrix elements of the nonlocal Fock exchange potential:
\begin{eqnarray}
V_{HF{\bf k}}^{lm}(t)=-a_{0}^{3}\int \frac{d{\bf q}}{(2\pi
)^{3}}V({\bf k}-{\bf q})\rho_{{\bf q}}^{lm}(t). \label{VHF}
\end{eqnarray}
Substitution of the expression (\ref{VHF}) into Eqs.~(\ref{rhovv}),
(\ref{rhovc}) leads to the following density-matrix equations in the
Hartree-Fock approximation:
\begin{eqnarray}
\frac{\partial}{\partial t}\rho_{{\bf k}}^{vv}(t) = &-&2{\rm
Im}\left[ \left( E(t)d_{\bf k}^{cv}+a_{0}^{3}\int \frac{d{\bf
q}}{(2\pi )^{3}}V({\bf k}-{\bf q})\rho_{{\bf q}}^{cv}(t)\right)
\rho_{{\bf k}}^{vc}(t)\right] , \label{rhovvBloch}
\\
\frac{\partial}{\partial t}\rho_{{\bf k}}^{vc}(t)=
&-&i[\varepsilon_{\bf k}^{v}-\varepsilon_{\bf k}^{c} -a_{0}^{3}\int
\frac{d{\bf q}}{(2\pi )^{3}}V({\bf k}-{\bf q})(\rho_{{\bf
q}}^{vv}(t)-\rho_{{\bf q}}^{cc}(t)) ]\rho_{{\bf k}}^{vc}(t)
\nonumber \\
&-&i [\rho_{{\bf k}}^{cc}(t)-\rho_{{\bf k}}^{vv}(t)] \left(
E(t)d_{\bf k}^{vc}-a_{0}^{3}\int \frac{d{\bf q}}{(2\pi)^{3}}V({\bf
k}-{\bf q})\rho_{{\bf q}}^{vc}(t)\right) . \label{rhovcBloch}
\end{eqnarray}
These equations are equivalent to the standard SBEs.\cite{Haug}) The
solution of the system of Eqs.~(\ref{rhovvBloch}),
(\ref{rhovcBloch}) in the presence of an external field ${\bf E}(t)$
allows one to calculate the optical polarization in the system by
means of Eq.~(\ref{Absorption}).

In Fig.~\ref{fig:1}, we present the frequency dependence of the
optical absorption spectra at different values of the amplitude of
the external field in Hartree-Fock approximation, when an external
short-time electric pulse Eq.~(\ref{electricfield}) is applied.
\begin{figure}[h]
\centering{
\includegraphics[width=8.0cm]{Fig1.eps}}
\caption{Optical absorption spectra in Hartree-Fock approximation at
different values of the valence bandwidth (divided by $\pi^{2}$).
Here and in the Figures below, we consider external pulses
Eq.~(\ref{electricfield}) of duration $\tau$. For this Figure,
$\tau=0.05$. The conduction bandwidth and the band gap are
$W^{c}=0.4\pi^{2}$ and $\omega_{g}=5$. The amplitude of the electric
field is $E_{0}=2.0$. We consider the case of parabolic bands.}
\label{fig:1}
\end{figure}
Here and in other Figures, we introduce screening $\lambda=1$ in the
Coulomb kernel $1/({\bf q}^{2}+\lambda^{2})$ and in order to reach a
steady state more quickly we introduced a decoherence terms $\Gamma
(1+\alpha |{\bf k}|/\pi ) \rho^{lm}$ on the right hand side of the
density matrix equations. Here $\Gamma =0.2,\alpha =7.5$. In this
paper, in the numerical results for the absorption spectra we set
the prefactor $(8\pi
/\sqrt{\epsilon_{b}})(\varepsilon_{0}^{c}-\varepsilon_{0}^{v})|d^{cv}|^{2}$
to be equal 1 [see Eqs.~(\ref{P}) and (\ref{Absorption})]. The
absorption spectra demonstrate a pronounced excitonic feature with a
shape and a peak position that depend on the external field
amplitude parameters.

The SBE approach was successfully applied to study optical
properties of different bulk materials in the case of weak external
fields, when linear response theory can be applied. Recently, this
formalism was used to study the nonlinear response of different
quantum-well systems,\cite{Maslov1,Maslov2} and some other effects,
like the sideband generation, Franz-Keldysh effect, four-wave
mixing, and higher correlation effects, in particular, biexcitons
etc (see, for example Ref.~\onlinecite{Chemla}). As discussed in the
Introduction, the main shortcoming of the SBE approach for small
(nano-) systems and short pulses is that the Coulomb interaction
effects are treated the mean-field theory level. All the fluctuation
effects are hidden in the inverse scattering (decoherence) time
parameters $\Gamma_{{\bf k}}^{lm}$ , which are usually introduced
into the system of the SBEs (\ref{rhovvBloch}), (\ref{rhovcBloch})
by means of the terms $\Gamma_{{\bf k}}^{lm}\rho_{{\bf k}}^{lm}$.
However, the characteristic times in this case are shorter than the
Coulomb scattering time; therefore, fluctuation effects are very
important and can not be neglected. It is extremely difficult to
include the higher Coulomb terms in the SBEs in a controllable way,
since in this case one needs to consider additional equations for
higher order correlation functions. The TDDFT approach allows one to
treat the Coulomb effects in principle exactly, which should make
this approach favorable in the case of small systems and short-time
pulses, provided one can find a suitable xc functional to account
for correlations. In the following two Subsections, we shall
consider the optical properties of the two-band insulator by means
of the TDDFT formalism developed in Section \ref{Formalism}. We
limit ourselves here to exchange-only functionals.

\subsection{Adiabatic LDA and GGA}
\label{LDAsection}

The LDA is a standard approximation used in DFT to study the ground
state properties of many materials. In the time-dependent case,
there exists a generalization of this approximation - the adiabatic
LDA (ALDA). In the adiabatic approximation it is assumed that the xc
potential at time $t$ depends on the time-dependent particle density
$n({\bf r},t)$ at the same time $t$ only. In other words, all memory
effects are neglected, and the TDDFT equations remain local in time,
which allows one to solve the problem numerically relatively easily.
In ALDA, the x-only potential matrix elements have the following
momentum and time dependence:
\begin{eqnarray}
V_{xLDA{\bf k}}^{lm}(t)=-\left(\frac{3}{\pi}
\right)^{1/3}\int_{cell} d{\bf r} \psi_{{\bf k}}^{l*}({\bf r})
n^{1/3}({\bf r},t) \psi_{{\bf k}}^{m}({\bf r}).
\label{VLDAapproximation}
\end{eqnarray}

Our numerical analysis confirms the previous observation (see, e.g.
Ref.~\onlinecite{Onida}) that the optical absorption spectra do not
demonstrate excitonic features with the ALDA exchange potential
(\ref{VLDAapproximation}) at various values of the model parameters
(Fig.~\ref{fig:2}). Actually, there is a very wide peak in the
absorption spectra at rather large values of the quasiparticle
masses (or very narrow energy bands); however, this wide absorption
spectra weight cannot be related to a well-defined excitonic energy
value, and hence it does not correspond to an exciton formation. For
details of the numerical calculations in ALDA and other potentials
used in this paper (see below), we refer the reader to
Appendix~\ref{appendix_density}.

\begin{figure}[h]
\centering{
\includegraphics[width=8.0cm]{Fig2.eps}}
\caption{Absorption spectra in ALDA at different values of the
electric field amplitude and the free electron bands $W^{v}=0.15,
W^{c}=0.06$. The other parameters are $\omega_{g}=0.375, a_{0}=20,
\tau =10 ,\Gamma =0.0025$  and $\alpha =7.5$.} \label{fig:2}
\end{figure}

Similar results can be obtained for standard adiabatic GGAs, for
example the van Leeuwen-Baerends\cite{vanLeeuwen} (LB) potential. In
the LB approximation, the xc potential has the following form:
\begin{eqnarray}
V_{LB}({\bf r},t)=V_{LDA}({\bf r},t)-\beta n^{1/3}({\bf r},t)
\frac{x^{2}}{1+3\beta x\ln (x+\sqrt{x^{2}+1})}, \ \ \ \
x=\frac{|\nabla n({\bf r},t)|}{n^{4/3}({\bf r},t)},
\label{VLBapproximation}
\end{eqnarray}
where $\beta$ is a parameter, which depends on the material. This
potential has an important feature for finite systems, namely, a
correct ($\sim 1/r$) asymptotic behavior at long distances (The ALDA
potential decreases exponentially at $r\rightarrow\infty$). In spite
of this, no excitonic features are produced.

Thus, we have seen that the standard adiabatic LDA+GGAs for the xc
potentials does not allow one to reproduce the excitonic features in
the optical absorption spectra within the TDDFT formalism developed
above. One needs to go beyond this approximation and to find another
class of simple TDDFT potentials which demonstrate excitonic peaks
in the absorption spectra. As shown by Kim and G\" orling
\cite{Kim1,Kim2} such potentials exist. The main requirement is a
$1/q^{2}$ singularity in the exchange energy kernel. In the
following Subsection, we shall consider the optical absorption
spectra for classes of functionals where the underlying exchange
energy has such a singularity.

\subsection{The Slater and KLI potentials}
\label{SlaterKLIsection}

As shown above, the ALDA cannot describe excitonic effects in the
optical absorption spectra. A fundamental shortcoming of the LDA
approximation is that it contains a self-interaction error. In order
to reduce this error, several approximations for self-interaction
corrected (SIC) potentials, were proposed. Probably the most often
used SIC potential is due to Perdew and Zunger.\cite{Perdew}
However, in their scheme one must deal with orbital-dependent
potentials, which makes the calculations difficult, especially in
the time-dependent case. To make a computational procedure simpler,
the method of the optimized effective potential (OEP) was proposed
(for overview and references, see for example Ref.~\cite{Ullrich}).
In this approximation, all the wave functions for different orbitals
satisfy a Schroedinger equation with a common, orbital-independent,
xc potential $v_{xc\sigma}^{OEP}({\bf r})$. A time-dependent
generalization of the OEP approximation was given in
Refs.~\onlinecite{Ullrich2,Gross}. Unfortunately, this method is
computationally very demanding in the time-dependent case. Krieger,
Li, and Iafrate\cite{Krieger} proposed a simplified method (the KLI
scheme) for the OEP in the equilibrium exact-exchange case with
$v_{xc\sigma}^{OEP}({\bf r})$ depending explicitly on the orbital
functions $\varphi_{j\sigma}$. In the equilibrium case, the KLI
potential is defined by the following integral equation:
\begin{eqnarray}
v_{xc\sigma}^{KLI}({\bf r})=\sum_{j}\frac{n_{j\sigma}({\bf
r})}{n_{\sigma}({\bf r})}\left\{ u_{xcj\sigma ({\bf r})} + \int
d^{3}r' |\varphi_{j\sigma} ({\bf r}')|^{2} [v_{xc\sigma}^{KLI}({\bf
r}')-u_{xcj\sigma ({\bf r}')}]\right\}, \label{VKLI}
\end{eqnarray}
were the orbital-dependent potentials $u_{xcj\sigma}({\bf r})$ are
obtained from the xc energy $E_{xc}$ as follows:
\begin{eqnarray}
u_{xcj\sigma}({\bf r})=[f_{j\sigma}\varphi_{j\sigma}^{*}({\bf
r})]^{-1}\delta E_{xc}[\{\varphi_{j\sigma}\}]/\delta
\varphi_{j\sigma}({\bf r}). \label{uKLI}
\end{eqnarray}
This approximation was generalized to the time dependent case in the
adiabatic approximation ($n({\bf r})\rightarrow n({\bf r},t)$) in
Ref.~\onlinecite{Ullrich2}.

In the linear regime, the optical absorption spectra of insulators
show excitonic peaks, when an OEP approximation with the exchange
energy with a kernel that contains a $1/q^{2}$ singularity is
used.\cite{Kim1,Kim2} However, it is much more difficult to use this
approach for short and strong pulses, when one needs to go beyond
linear response.

Here, we consider simplified OEPs with a Coulomb singularity in the
exchange energy kernel, which are approximate solutions of
Eqs.~(\ref{VKLI}), (\ref{uKLI}), and solve the problem in the
time-domain by using the TDDFT formalism developed in the previous
Sections. This approach can be applied for external fields of
arbitrary strength and duration.

We consider the KLI potential and  the Slater potential
\cite{Krieger}, which can be obtained if one neglects the
orbital-dependent constants on the right hand side of
Eq.~(\ref{VKLI}):
\begin{eqnarray}
v_{xc\sigma}^{Slater}({\bf r},t)=\sum_{j}\frac{n_{j\sigma}({\bf
r},t)}{n_{\sigma}({\bf r},t)}u_{xcj\sigma ({\bf r},t)}.
\label{VSlater}
\end{eqnarray}
We use the Fock exchange energy for our two-band model in
Eq.~(\ref{uKLI}). Optical absorption spectra obtained with the
Slater and KLI exchange potentials at different values of the model
parameters are presented in Figs.~\ref{Slater} and \ref{KLI}.

\begin{figure}[h]
\centering{
\includegraphics[width=8.0cm]{Fig3.eps}}
\caption{Optical absorption spectra in Slater approximation at
different values of the valence bandwidth (divided by $\pi^{2}$).
The other parameters are $W^{c}=0.025\pi^{2}, \omega_{g}=0.2,
a_{0}=10,\tau=4, E=0.0166,\Gamma =0.012$ and $\alpha =7.5$.}
\label{Slater}
\end{figure}

As can be seen from these Figures, the absorption spectra
demonstrate a significant excitonic peak. In particular, the
excitonic peak amplitude and the exciton binding energy decrease
with increasing valence bandwidth in the Slater case
(Fig.~\ref{Slater}). This effect takes place because the increase of
the bandwidth is equivalent to a reduction of the effective mass of
electron-hole pairs. A similar behavior can be found in the case of
the KLI potential. Fig.~\ref{KLI} shows the KLI absorption spectrum
at different values of the electric field. Here, the spectrum
demonstrates nonlinear effects when the pulse amplitude is large.

There is a significant quantitative difference between different xc
potentials. In particular, we find that the excitonic features
become more pronounced as one passes from KLI to Slater. The
excitonic effects are defined mainly by the ratio of the Coulomb
interaction energy to the typical energy of the free system. Since
in our case the valence and conduction bands and the gap have the
same order of magnitude, we can consider the ratio of the Coulomb
energy to the valence bandwidth. In the Slater approximation, the
amplitude of the Coulomb interaction energy appears to be bigger
compared to KLI. In fact, as follows from the Appendix, the Coulomb
interaction matrix elements are much larger in the Slater
approximation (see Eqs.~(\ref{A_approximation}), (\ref{B1}) and
(\ref{B2})). In the strongly localized case, considered in this
paper, the Slater results are closer to HF (Fig.~\ref{comparison}).
For less localized electrons, when $a_{0}\sim 1$ and the momentum
dependence of the xc potential matrix elements can not be neglected,
we expect to get closer agreement between Slater and KLI. Another
important conclusion from our numerical results is a decrease of the
excitonic binding energy in Slater and KLI compared to HF. In fact,
it is known that the HF approximation gives an overestimated binding
energy of excitons (for a discussion, see
Ref.~\onlinecite{Bruneval}).

\begin{figure}[h]
\centering{
\includegraphics[width=8.0cm]{Fig4.eps}}
\caption{Optical absorption spectra in KLI approximation at
different values of the electric field. The other parameters are
$W^{v}=0.0416\pi^{2}, W^{c}=0.0208\pi^{2}, \omega_{g}=0.166,
a_{0}=10,\tau=4.8,\Gamma =0.012,$ and $\alpha =7.5$.} \label{KLI}
\end{figure}

\begin{figure}[h]
\centering{
\includegraphics[width=8.0cm]{Fig5.eps}}
\caption{Optical absorption spectra in different approximations at
the same values of the model parameters.  The valence bandwidth is
equal to $0.05\pi^{2}$ and the other parameters are given in the
caption to Fig.~\ref{Slater}. The Hartree-Fock result is obtained
using a Bloch function approximation for the xc potential matrix
elements (see Appendix).} \label{comparison}
\end{figure}

Thus, we have shown that TDDFT can describe excitonic effects in the
optical absorption spectra triggered by short-time laser pulses,
when the exchange energy kernel contains a long-range Coulomb
singularity.

\section{Conclusions}
\label{Conclusions}

In this paper, a density-matrix TDDFT formalism to describe
ultrafast processes in semiconductor structures has been developed.
We have shown that the corresponding system of equations for the
matrix elements is a generalization of the SBEs, since it allows one
to take into account Coulomb effects in principle exactly. This is
very important in the case of short pulses and when the system is
very small, such as for nanostructures. Another important advantage
of this formalism is that it can be applied directly in the time
domain, which makes the calculation much faster. As an example, we
studied the optical absorption spectra of a two-band model bulk
insulator. We have shown that the optical absorption spectra include
excitonic effects when the xc energy kernel contains a $1/q^{2}$
singularity. The exciton binding energy within the Slater and KLI
approaches is much smaller compared to HF, which often gives too
large value for the binding energy.

This TDDFT approach should be useful for studying ultrafast
processes in real semiconductor and polymer nanostructures, for
example for short-time laser pulse experiments. In particular, it
gives access to a variety of nonlinear effects, which will be the
subject of future studies.

\section*{Acknowledgements}
We thank Paul de Boeij for useful discussions. We acknowledge
financial support from NSF under Grant No. DMR-0553485.

redpajama_set_name: RedPajamaArXiv


Homicide is justifiable if committed by any person while resisting any attempt to murder such person, or to harm the unborn child of such person in a manner and to a degree that is unlawful and likely to result in the death of the unborn child, or to commit any felony upon him or her, or upon or in any dwelling house in which such person is.
The bolded part would be the new part, and the upshot, per Sargent is this "would make it clear that 'justifiable homicide' can only apply in response to an unlawful act, which would obviously not include abortion, which is legal."
A law under consideration in South Dakota would expand the definition of "justifiable homicide" to include killings that are intended to prevent harm to a fetus -- a move that could make it legal to kill doctors who perform abortions. The Republican-backed legislation, House Bill 1171, has passed out of committee on a nine-to-three party-line vote, and is expected to face a floor vote in the state's GOP-dominated House of Representatives soon.
The bill, sponsored by state Rep. Phil Jensen, a committed foe of abortion rights, alters the state's legal definition of justifiable homicide by adding language stating that a homicide is permissible if committed by a person "while resisting an attempt to harm" that person's unborn child or the unborn child of that person's spouse, partner, parent, or child. If the bill passes, it could in theory allow a woman's father, mother, son, daughter, or husband to kill anyone who tried to provide that woman an abortion -- even if she wanted one.
Says Vicki Saporta, the head of the National Abortion Federation, "The bill in South Dakota is an invitation to murder abortion providers."
Phil Jensen did not return Sheppard's calls, but he did speak to The Plum Line's Greg Sargent this morning, and guess what? He feels his law is being badly misinterpreted! "This has nothing to do with abortion," he says.
Since the original outcry, a change has been made to the bill: it only allows the "justifiable homicide" defense in cases of self-defense. It's no longer applicable to fathers, mothers, sons, daughters, or husbands.
UPDATE: Sorry for the confusion, there was no change to the bill. The bill, in its current form, can be seen here.
So what does this law seek to do?
"Say an ex-boyfriend who happens to be father of a baby doesn't want to pay child support for the next 18 years, and he beats on his ex-girfriend's abdomen in trying to abort her baby. If she did kill him, it would be justified. She is resisting an effort to murder her unborn child."
Jensen was dismissive of the notion that this law could be seen as an invitation to kill abortion providers: "Never say never, but if some loony did what you're suggesting, then this law wouldn't apply to them. It wouldn't be justifiable homicide."
I guess I'm pretty hung up on that whole "never say never" part.


text:
https://www.mrt.com/news/article/City-council-members-to-decide-fate-of-Hillcrest-14968745.php
City council members to decide fate of Hillcrest Village
Officials expect heavy opposition regarding a west Midland apartment complex being built to provide less expensive housing for taxing entity employees
By Stewart Doreen, MRT.com/Midland Reporter-Telegram
Published 10:10 pm CST, Saturday, January 11, 2020
FILE PHOTO: The new Midland City Council on Tuesday will determine the fate of a 200-unit development expected to provide affordable housing for employees of Midland ISD and Midland Memorial Hospital and first-responders.
FILE PHOTO: The new Midland City Council on Tuesday will determine the fate of a 200-unit development expected to provide affordable housing for employees of Midland ISD and Midland Memorial Hospital and
Photo: MRT File Photo
The new Midland City Council on Tuesday will determine the fate of a 200-unit development expected to provide affordable housing for employees of Midland ISD and Midland Memorial Hospital and first-responders.
Hillcrest Village is a proposed multi-family development located on nearly 20 acres on Midland Drive, just west of Doug Russell pool.
The applicant, the Midland Community Development Corp., is requesting a rezone of the property to a "low-density apartment complex." City documents show the proposed site plan calls for 20, two-story buildings, a clubhouse and dog park. The city also reports that "adequate parking is provided with a total of 488 spaces, 246 surface spaces and 242 garage spaces."
Sixty percent of the units would be one-bedroom, 30 percent would be two-bedroom, and the rest three-bedroom, officials said previously.
The city's Planning and Zoning Commission approved the rezoning request during a November meeting, but some Midlanders are not in favor of the addition to west Midland. City documents show staff has received 100 written objection letters as of Jan. 8; 30.9 percent of those objecting within the 200-foot notification area. Staff also received a petition.
The petition, dated Oct. 9 was to the Planning and Zoning Commission, the mayor and the rest of the Midland City Council. Homeowners and residents of the Hillcrest Acres, Alamo Heights, Bel Air, West Cliff and Westgate subdivisions stated 17 reasons for their opposition. These include:
--Residents favor single-family homes in that area.
--There are no city water lines and no nearby sewer lines.
All houses between Princeton and Cuthbert avenues on the north and south between Midland Drive and almost to Woodcrest Drive on the east and west are on water wells and septic systems.
--The neighborhood is not economically depressed and does not fit the mission statement of the MCDC.
--These apartments would be tax-exempt because the MCDC retains ownership.
--Traffic will be increased, and safety will be decreased in the neighborhood.
The petition also states that some residents near the proposed development have lived there since the 1960s and that all but one home in the block of Princeton Avenue between Midland Drive and Woodcrest Drive are occupied by the property owner.
City officials expect a full house for the council meeting.
If a previous presentation in front of the Midland Development Corp. is any indication, city leaders will hear that the Hillcrest Village lease rates for a single-bedroom is expected to be 30 to 50 percent less than current rates "at other Class A properties." Project officials said at the commission's October meeting that already there are non-binding agreements for as many as 120 total units with Midland Memorial and MISD.
Hillcrest Village carries a total development cost of $41.7 million. Project officials said during the October meeting that much of that money will come from banks but an estimated equity of $14 million is needed to keep rents lower. Project officials also said they would be asking for additional money from the MDC.
Meeting notes: The Midland City Council typically meets on the second and fourth Tuesdays of the month. Tuesday's meeting will begin at 10 a.m. … This will be the first meeting of the new City Council, which includes Mayor-elect Patrick Payton. Also expected to attend their first meetings are Jack Ladd Jr. of District 3 and Lori Blong of District 4. All three were elected in November. Other members of the council will be current District 1 representative Scott Dufford, District 2 representative John B. Love III and at-large representatives Spencer Robnett and Michael Trost.


Anemia occurs when your blood has an insufficient number of red-blood cells. This condition also can develop if your red-blood cells don't contain enough of the iron-fortified protein hemoglobin that helps red blood cells move oxygen from the lungs to the rest of the body.
Anemia can be short-lived or chronic and may be caused by a variety of factors.A healthy diet may enough to prevent and even treat anemia.
According to the Mayo Clinic, anemia may be asymptomatic when it first develops. As the condition progresses, some of its signs may include tiredness and a quick or sporadic heartbeat. Other symptoms associated with anemia are chest pain, shortness of breath, dizziness, headache, cold hands and feet, and pale skin.
The Mayo Clinic reports anemia that is caused by an iron deficiency is common, striking up to 2 percent of adults in the U.S.
A diet low in folate and vitamin B-12 also make conditions ripe for anemia to develop. A deficiency of these nutrients can lead to a decline in the creation of red-blood cells.
People of all ages who regularly eat a diet lacking in adequate amounts of iron and vitamins are in danger of becoming anemic. Your doctor may recommend dietary changes in addition to taking vitamins or iron supplements. Vitamin C helps the body soak up iron.
The National Institutes of Health says red meats, especially beef or liver can help treat anemia. Chicken, pork, turkey, fish and shellfish may also be beneficial because they too are good sources of vitamin B12. Dairy products including eggs, milk yogurt and cheese are also full of B12.
The NIH recommends eating plenty of dried fruits such as raisins along with apricots, bananas, oranges and peaches to counteract the effects of anemia. Other dietary remedies for anemia include dark leafy vegetables such as spinach, as well as peas and white, red and baked beans. These foods are rich in folic acid, a form of vitamin B, and vitamin C.
According to the NIH, iron is added to bread, cereal and pasta. The nutritional information label on the item will say exactly how much iron it contains. The amount is given as a percentage of the recommended daily intake of iron.
Many types of anemia can't be prevented. However, you can help avoid iron-deficiency anemia and vitamin-deficiency-induced anemias by eating a healthy and varied diet.
The Mayo Clinic reports no treatment for anemia that develops as a result of chronic disease. In cases of aplastic (bone-marrow failure) anemia, a blood transfusion may be necessary to increase red-blood cell levels.


text:
Freight access in flood-impacted regions
Written by: Mitchel Hanlon
In the aftermath of the flooding disaster across NSW, the priority is to ensure accessibility, safety and the continuation of business in affected areas. As outlined by Roads & Infrastructure Australia there is increased road access being granted to higher priority vehicles in NSW in order to keep up supply to areas impacted by flood. So why can't we move freight on the rail network?
Nationwide, the rail network in Australia is outdated and unable to keep up with Australia's increasing national freight volume. Deputy Premier John Barilaro said "the flooding has impacted a number of our rail lines and we are working to get them back up and running as soon as possible. In the interim, we are ensuring we can move essential goods by road in safe modern transport vehicles." But, as surveyors, we are aware that the rail network has been insufficient for sometime, without the impact of flooding, and our road network does not have the required capacity to meet increasing levels of freight.
As technology increases, new trains are entering the market, stretching our existing rail network. The Inland Rail project, once completed, is expected to more than double the movement of freight by rail in Australia by 2050, reducing reliance on roads and creating opportunities for regional Australia. In addition to freeing up the roads and improving road safety, the Inland Rail will reduce congestion on existing rail on the eastern coast, largely used for transporting passengers.
In terms of access, the new network will provide an alternative route to travel south of Queensland. This will make the nation's freight network less vulnerable to weather events like the recent floods. With more reliable freight, the economy is set to benefit greatly from faster transit times and better connection.
What's the renewables sector and how does it affect me?
We're at the start of a major transformation.
The need for Regional Infrastructure Partnerships
The regions are experiencing a growth surge.
Weeds and their categories
Weeds – invasive, exotic or noxious?
Vale Bill Gilchrist
This week, Hanlons lost one of our family members.
Identification Surveys - Why are they important?
Sand - A Limited Commodity
Important Insects
Gorgeous Geology
The Global Food Shortage and Intensive Agriculture
Regional Feedlots at Hanlons Consulting
No more paper land titles and digital plans
Soil Identification Matters


Your network contains one Active Directory domain named contoso.com. All domain controllers run Windows Server 2012 R2.
You have a custom administrative template file named App1.admx. App1.admx contains application settings for an application named App1.
You copy App1.admx to the central store. You create a new Group Policy object (GPO) named App1.Settings.
When you edit App1.Settings, you receive the warning message shown in the following exhibit.
You need to ensure that you can edit the settings for App1 from the app1_settings GPO.
Modify the permissions of the ADMX file.
Copy an ADML file to the central store.
Add an administrative Template to the App1_settings GPO.
Move the DAMX file to the local Policy definitions folder.
Not A: The Get-ADGroupMember cmdlet gets the members of an Active Directory group. Members can be users, groups, and computers.
You need to ensure that you can clone DC6. What should you do?
Transfer the schema master to DC6.
Transfer the PDC emulator to DC5.
Transfer the schema master to DC4.
Transfer the PDC emulator to DC2.
You need to update the PATH variable on all of the client computers. Which Group Policy preference should you configure?