Joyal's Suspension Functor on $\Theta $ and Kan's Combinatorial Spectra
In [Joyal] where the category $\Theta$ is first defined it is noted that the dimensional shift on $\Theta$ suggests an elegant presentation of the unreduced suspension on cellular sets. In this note we prove that the reduced suspension associated to that presentation is left Quillen with respect to the Cisinski model category structure presenting the $\left(\infty,1\right)$-category of pointed spaces and enjoys the correct universal property. More, we go on to describe how, in forthcoming work, inspired by the combinatorial spectra described in [Kan], this suspension functor entails a description of spectra which echoes the weaker form of the homotopy hypothesis, we describe the development of a presentation of spectra as locally finite weak $\mathbf{Z}$-groupoids.