English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We study a generic problem of dissipative quantum mechanics, a small localquantum system with discrete states coupled in an arbitrary way (i.e. notnecessarily linear) to several infinitely large particle or heat reservoirs.For both bosonic or fermionic reservoirs we develop a quantum field-theoreticaldiagrammatic formulation in Liouville space by expanding systematically in thereservoir-system coupling and integrating out the reservoir degrees of freedom.As a result we obtain a kinetic equation for the reduced density matrix of thequantum system. Based on this formalism, we present a formally exactperturbative renormalization group (RG) method from which the kernel of thiskinetic equation can be calculated. It is demonstrated how the nonequilibriumstationary state (induced by several reservoirs kept at different chemicalpotentials or temperatures), arbitrary observables such as the transportcurrent, and the time evolution into the stationary state can be calculated.Most importantly, we show how RG equations for the relaxation and dephasingrates can be derived and how they cut off generically the RG flow of thevertices. The method is based on a previously derived real-time RG techniquebut formulated here in Laplace space and generalized to arbitraryreservoir-system couplings. Furthermore, for fermionic reservoirs with flatdensity of states, we make use of a recently introduced cutoff scheme on theimaginary frequency axis which has several technical advantages. We demonstratethe method by applying it to the nonequilibrium isotropic Kondo model in1-loop. We present a systematic way to solve the RG equations analytically inthe weak-coupling limit and provide an outlook of the applicability to thestrong-coupling case.

A perturbative nonequilibrium renormalization group method for dissipative quantum mechanics: Real-time RG in frequency space (RTRG-FS)