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We present a fermionic description of non-equilibrium multi-level systems. Our approach uses the Keldysh path integral formalism and allows us to take into account periodic drives, as well as dissipative channels. The technique is based on…

Current studies about the continuous-variable systems in non-Hermitian quantum mechanics heavily revolved around the singularities in the eigenspectrum by mimicking their discrete-variable counterparts. Discussions over the nonunitary…

Quantum Physics · Physics 2026-04-28 Zhu-yao Jin , Jun Jing

Recently, apparent nonphysical implications of non-Hermitian quantum mechanics (NHQM) have been discussed in the literature. In particular, the apparent violation of the no-signaling theorem, discrimination of nonorthogonal states, and the…

Quantum Physics · Physics 2019-12-25 Chia-Yi Ju , Adam Miranowicz , Guang-Yin Chen , Franco Nori

In these lectures we introduce the functional renormalization group out of equilibrium. While in thermal equilibrium typically a Euclidean formulation is adequate, nonequilibrium properties require real-time descriptions. For quantum…

High Energy Physics - Phenomenology · Physics 2015-06-04 Jürgen Berges , David Mesterházy

In an amended version of non-Hermitian interaction picture we propose to work with the states $\psi(t)$ in a dyadic representation. The control of evolution via two conjugate Schr\"{o}diner equations then renders the usual necessity of the…

Quantum Physics · Physics 2023-06-29 Miloslav Znojil

Deformations of the canonical commutation relations lead to non-Hermitian momentum and position operators and therefore almost inevitably to non-Hermitian Hamiltonians. We demonstrate that such type of deformed quantum mechanical systems…

High Energy Physics - Theory · Physics 2014-11-20 Bijan Bagchi , Andreas Fring

Standard quantum mechanics predicts the non-conservation of state norms and probability when the fundamental requirement of the Hermiticity of the Hamiltonian is relaxed. Biorthogonal quantum mechanics, or the more general metric formalism,…

Quantum Physics · Physics 2025-07-18 Mario Gonzalez , Karin Sim , R. Chitra

A discussion is given of the quantisation of a physical system with finite degrees of freedom subject to a Hamiltonian constraint by treating time as a constrained classical variable interacting with an unconstrained quantum state. This…

General Relativity and Quantum Cosmology · Physics 2009-11-10 Charles Wang

We develop a general theory of non-equilibrium states based on the Keldysh formalism, in particular, for charged-particle systems under static uniform electromagnetic fields. The Dyson equation for the uniform stationary state is rewritten…

Statistical Mechanics · Physics 2009-11-11 Shigeki Onoda , Naoyuki Sugimoto , Naoto Nagaosa

In this article we give an overview of the concept of universal dynamics near non-thermal fixed points in isolated quantum many-body systems. We outline a non-perturbative kinetic theory derived within a Schwinger-Keldysh closed-time…

Quantum Gases · Physics 2019-11-13 Christian-Marcel Schmied , Aleksandr N. Mikheev , Thomas Gasenzer

The accurate simulation of real--time quantum transport is notoriously difficult, requiring a consistent scheme to treat incoming and outgoing fluxes at the boundary of an open system. We demonstrate a method to converge non--equilibrium…

Mesoscale and Nanoscale Physics · Physics 2015-10-02 Justin E. Elenewski , Yanxiang Zhao , Hanning Chen

We survey some of the main conceptual developments in the study of PT-symmetric and pseudo-Hermitian Hamiltonian operators that have taken place during the past ten years or so. We offer a precise mathematical description of a quantum…

Quantum Physics · Physics 2015-05-19 Ali Mostafazadeh

This is a review paper concerned with the global consistency of the quantum dynamics of non-commutative systems. Our point of departure is the theory of constrained systems, since it provides a unified description of the classical and…

High Energy Physics - Theory · Physics 2015-05-13 F. S. Bemfica , H. O. Girotti

We study the classical and quantum oscillator in the context of a non-additive (deformed) displacement operator, associated with a position-dependent effective mass, by means of the supersymmetric formalism. From the supersymmetric partner…

Quantum Physics · Physics 2021-09-15 Bruno G. da Costa , Genilson A. C. da Silva , Ignacio S. Gomez

Extended quantum mechanics using non-Hermitian, pseudo-Hermitian Hamiltonians is briefly reviewed. Supersymmetric regularizations, solvable simulations and large-N expansion techniques are recollected as suitable means for the study of…

Quantum Physics · Physics 2009-11-10 Miloslav Znojil

Describing open quantum systems in terms of effective non-Hermitian Hamiltonians gives rise to non-unitary time evolution. In this paper, we study the impact of non-unitary dynamics on the emergent hydrodynamics in quantum systems with a…

Statistical Mechanics · Physics 2024-10-10 Dylan E. Mahoney , Jonas Richter

As an unusual type of anomalous diffusion behavior, superballistic transport is not well known but has been experimentally simulated recently. Quantum superballistic transport models to date are mainly based on connected sublattices which…

Chaotic Dynamics · Physics 2015-06-19 Qifang Zhao , Cord A. Muller , Jiangbin Gong

A $\mathcal{PT}$-symmetric, non-Hermitian Hamiltonian in the $\mathcal{PT}$-unbroken regime can lead to unitary dynamics under the appropriate choice of the Hilbert space. The Hilbert space is determined by a Hamiltonian-compatible inner…

Quantum Physics · Physics 2025-03-19 Himanshu Badhani , Subhashish Banerjee , C. M. Chandrashekar

We provide a reviewlike introduction into the quantum mechanical formalism related to non-Hermitian Hamiltonian systems with real eigenvalues. Starting with the time-independent framework we explain how to determine an appropriate domain of…

Quantum Physics · Physics 2015-06-26 Carla Figueira de Morisson Faria , Andreas Fring

Supmech, which is noncommutative Hamiltonian mechanics \linebreak (NHM) (developed in paper I) with two extra ingredients : positive observable valued measures (PObVMs) [which serve to connect state-induced expectation values and classical…

Mathematical Physics · Physics 2016-02-16 Tulsi Dass