Particle production by expanding in the future light cone scalar quantum field is studied assuming that initial state associated with quasiequilibrium statistical operator corresponding to fluid dynamics. We calculate particle from a longitudinally boost-invariant designed as simple but reliable model for central rapidity region of relativistic collision. Exact diagonalization performed introdu...

In these lecture notes, we present a pedagogical review of a number of related numerically exact approaches to quantum many-body problems. In particular, we focus on methods based on the exact diagonalization of the Hamiltonian matrix and on methods extending exact diagonalization using renormalization group ideas, i.e., Wilson’s Numerical Renormalization Group (NRG) and White’s Density Matrix ...

We demonstrate that quantum fluctuations suppress Bose-Einstein condensation of quasi-two-dimensional bosons in a rapidly rotating trap. Our conclusions rest in part on the derivation of an exact expression for the boson action in terms of vortex position coordinates, and in part on a solution of the weakly interacting boson Bogoliubov equations, which simplify in the rapid-rotation limit. We o...

Exact diagonalization is a powerful numerical technique to analyze static and dynamical quantities in quantum many-body lattice models. It provides unbiased information concerning quantum numbers, energies and wave-functions of the lowenergy eigenstates for almost any kind of microscopic model. The information about energies and quantum numbers is particularly useful to detect possible spontane...