Many-body wavefunctions for quantum impurities out of equilibrium

Hypergeometric resummation of self-consistent sunset diagrams for steady-state electron-boson quantum many-body systems out of equilibrium

Héctor Mera,1,2,* Thomas G. Pedersen,2,3 and Branislav K. Nikolić1 1Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716-2570, USA 2Department of Physics and Nanotechnology, Aalborg University, DK-9220 Aalborg East, Denmark 3Center for Nanostructured Graphene (CNG), DK-9220 Aalborg East, Denmark (Received 20 December 2015; revised manuscript received 21 August 201...

Rotation of Quantum Impurities in the Presence of a Many-Body Environment.

We develop a microscopic theory describing a quantum impurity whose rotational degree of freedom is coupled to a many-particle bath. We approach the problem by introducing the concept of an "angulon"-a quantum rotor dressed by a quantum field-and reveal its quasiparticle properties using a combination of variational and diagrammatic techniques. Our theory predicts renormalization of the impurit...

Thermal Equilibrium Distribution of Wavefunctions

It is well known that in quantum theory, thermal equilibrium at inverse temperature β corresponds to the density matrix (1/Z) exp(−βH). But a density matrix that is not pure can arise from many different distributions of the wavefunction. We address in this paper the question which distribution of the wavefunction corresponds to thermal equilibrium, or, in other words, which distribution of the...

Many–body Theory of Non–equilibrium Systems

Many–Body Aspects of Approach to Equilibrium

In 1956 Mark Kac [5] invented a microscopic, linear model, from which the nonlinear Boltzmann equation describing the evolution of the velocity distribution for a system of colliding particles could be rigorously derived. Consider N particles in one dimension that interact through random collisions. We consider the spatially homogeneous case only, i.e., the case where the particles are uniforml...