Including stream crossing in Lagrangian perturbation theory

I will discuss the path integral formalism for the clustering of the large-scale structure of the Universe (arXiv:1709.02834). This perturbative approach includes ab initio the stream crossing effects, i.e. multiple velocities for mass elements at a single position. Starting from a functional integral of displacement field, novel perturbative expansion is constructed by expansion in deviations from renormalized Zel'dovich evolution, obtaining terms that can be computed exactly including the displacements that have crossed streams. I will also discuss current results and implications in the context of ongoing and upcoming large-scale structure surveys.