On the rigorous derivation of the 2D cubic nonlinear Schr\"{o}dinger   equation from 3D quantum many-body dynamics
  We consider the 3D quantum many-body dynamics describing a dilute bose gas with strong confining in one direction. We study the corresponding BBGKY hierarchy which contains a diverging coefficient as the strength of the confining potential tends to $\infty$. We find that this diverging coefficient is counterbalanced by the limiting structure of the density matrices and establish the convergence of the BBGKY hierarchy. Moreover, we prove that the limit is fully described by a 2D cubic NLS and obtain the exact 3D to 2D coupling constant. 
Xuwen Chen, Justin Holmer
math.AP math-ph math.MP