# Tarek

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A PhD student in Germany. physics.reality@gmail.com

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|           | 149 reputation | website |          | member for  | 1 year, 7 months |
| 19 badges | location       | Germany | seen     | 7 hours ago |                  |

# 15 Comments

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| May1  | comment | English translation of Helmholtz' paper: “On the Physical Significance of the Principle of Least Action”Looking at the contents of this book, it does not contain the paper in the question.                                                                                                                                                                                                                                                                                                                                                                                           |
| Mar13 | comment | Hamiltonian of a simple graph$\Sigma_z=S_1^z+S_2^z$ The first matrix you wrote for $\Sigma_z$ is consistent with the definitions for$S_1^z$ and $S_2^z$. What is the problem in $S_1^z |ZZ\rangle=-0.5|ZZ\rangle$ ? Isn't this expected?                                                                                                                                                                                                                                                                                                                                               |
| Feb12 | comment | Nuclear Magnetic Resonance (NMR) Conceptual Questions                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| Jan6  | comment | Simulating the evolution of a wavepacket through a crystal lattice@hwlau I am not an expert in either of them. For sufficiently small systems, direct evolution with a simple 4th order Runge Kutta algorithm is sufficient. This amounts to using a truncated Taylor expansion of the time evolution operator. The Hamiltonian is represented as a sparse matrix.                                                                                                                                                                                                                     |
| Dec31 | comment | Simulating the evolution of a wavepacket through a crystal latticeHave you thought of using numerical algorithms, such as tDMRG, TEBD ?                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| Oct26 | comment | What is the spin rotation operator for spin > 1/2?Of course I am asking about the analogous formula for the expansion of the exponential in terms of cosines and sines not about the spin matrix !                                                                                                                                                                                                                                                                                                                                                                                     |
| Oct5  | comment | Scale invariance symmetry as a simple argument in an electrostatics problemThis is a valid proof, but I doubt that it is the scale invariance symmetry meant by Prof. Preskill. He wrote: "Actually, this problem can also be solved by a symmetry argument, though the symmetry used is less obvious than rotational invariance. Readers may enjoy constructing this symmetry argument, which (in keeping with the theme of this post) I find more elegant than the argument using concentric rings suggested by your hint."  Please read the discussion in the post in the question. |
| Sep12 | comment | Driving a solution of optical isomer molecules with the resonant frequencyI am indeed interested in the simulation details of this. If you wish, you can send to [my email]. In order to understand the theory behind this, we should first know how the chiral states are stabilized in the first place. One famous stabilization mechanism is [decoherence] (prl.aps.org/abstract/PRL/v103/i2/e023202). It seems to me that the predictions of this paper can be tested based on the setup in the question.                                                                          |
| Sep12 | comment | Driving a solution of optical isomer molecules with the resonant frequencyAren't $\psi_{L/R}$ the chiral states which are not eigenstates of the Hamiltonian, (and hence the paradox of Hund), while $\psi_\pm$ are the true eigenstates (which are not degenerate)?                                                                                                                                                                                                                                                                                                                   |
| Sep12 | comment | Driving a solution of optical isomer molecules with the resonant frequencyThe left and right-handed states are in fact degenerate. The two level system should be thought of as composed of the eigenstates of the hamiltonian/parity operator. Each of these eigenstates is either a sysmmetric or anti-symmetric superposition of the chirality states (left and right handed).                                                                                                                                                                                                      |
| Jul29 | comment | How are quantum phenomena in atoms and molecules protected against decoherence?Is there a proof that the pointer states are energy eigenstates?                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| Jul12 | comment | Are there devices which convert thermal energy to electric energy?I am seeking an effect which does not require temperature gradient. Can a device be built which captures "flying" phonons and convert them to electric energy without the need for a colder surface? I am aware that such an idea may violate the 2nd law of thermodynamics, but I wish to know from a technological perspective why this is (not) feasible.                                                                                                                                                         |
| Apr20 | comment | Partially filled orbitals and strongly correlated electronsI think you are using the term screening here in a different sense than the usual one, where electrons closer to the nucleus screen the positive nuclear charge from electrons at a larger distance, and hence those later electrons feels a smaller nuclear charge.                                                                                                                                                                                                                                                        |
| Apr18 | comment | Partially filled orbitals and strongly correlated electrons                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| Feb10 | comment | Electrodynamics textbook that emphasizes applicationsThanks Chris. I didn't mean engineering applications like transmission lines and waveguides, but simply applications from everyday life for the curious students.                                                                                                                                                                                                                                                                                                                                                                 |
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