Derivation of the Time Dependent Gross-Pitaevskii Equation in Two Dimensions

TL;DR

This paper rigorously derives the two-dimensional Gross-Pitaevskii equation from an interacting bosonic system, considering different interaction potentials, and emphasizes the importance of microscopic structure for accurate dynamics.

Contribution

It provides a microscopic derivation of the 2D Gross-Pitaevskii equation from many-body bosonic systems with novel interaction potential considerations.

Findings

Convergence of reduced density matrices to the nonlinear Schrödinger solution.

Validation of the mean field limit for different interaction potentials.

Highlighting the importance of microscopic structure in the dynamics.

Abstract

We present a microscopic derivation of the defocusing two-dimensional cubic nonlinear Schr\"odinger equation as a mean field equation starting from an interacting $N$-particle system of Bosons. We consider the interaction potential to be given either by $W_\beta(x)=N^{-1+2 \beta}W(N^\beta x)$, for any $\beta>0$, or to be given by $V_N(x)=e^{2N} V(e^N x)$, for some spherical symmetric, positive and compactly supported $W,V \in L^\infty(\mathbb{R}^2,\mathbb{R})$. In both cases we prove the convergence of the reduced density matrix corresponding to the exact time evolution to the projector onto the solution of the corresponding nonlinear Schr\"odinger equation in trace norm. For the latter potential $V_N$ we show that it is crucial to take the microscopic structure of the condensate into account in order to obtain the correct dynamics.