Figure 4

Toy model simulations for k and \(-k\) modes in a uniform gas initially in the Bogoliubov ground state. (a) Behaviour after a “caricature” quench to half-density, as per Eq. (16) for modes with \(k\xi =0.02,0.04,\dots ,0.18\). The remaining panels concern the better toy model of Eqs. (S10, S17) with parameters like the full simulation with \(\omega =902 \times 895 \times 71\) Hz, \(N=455852\), \(n_0=43.66/\upmu \text {m}^3\) peak density, and \(\tau _{\mathrm{release}}=38\,\upmu \hbox {s}\), and show the mode occupation evolution relative to the initial value (the survival rate). (b) For different initial locations in the condensate in the narrow direction: \(R_0=y/R_{\perp }\) where \(R_{\perp }=(1/\omega _y)\sqrt{2gn_0/m}\), and initial \(k=1.5/\upmu \hbox {m}\). (c) Evolution of the relative occupation for different ramp speeds \(\tau _{\mathrm{release}}\). Cycles of reabsorption are seen for the slow ramps. (d) Final survival rate for the same parameters. (e) Shows the dependence of the final survival rate on the trap aspect ratio \(\lambda\), when initial central density \(n_0\) is kept constant. The magenta dashed line indicates the experimental \(\lambda =12\) (like CE simulations), the black dashed line a spherical trap \(\lambda =1\) (like SE simulations).