Exact Results in Quantum Theory & Gravity

I will consider an integrable model of a mobile impurity propagating in a one-dimensional gas of free fermions. It is the simplest yet fundamental model capturing the peculiar physics and mathematics of the non-equilibrium processes. The integrability allows one to obtain a complete nonperturbative solution and express physical quantities in terms of the Fredholm determinants.
After a detailed analysis of these determinants, I will discuss several striking physical phenomena, such as incomplete relaxation and momentum-dependent impurity statistics. The universal properties of such one-dimensional systems can be described by the nonlinear Luttinger liquid (nLL). I will explain the microscopic derivation of nLL from the form factors and discuss the generalization to finite temperatures.