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Non-Hermitian classical and open quantum systems near an exceptional point (EP) are known to undergo strong deviations in their dynamical behavior under small perturbations or slow cycling of parameters as compared to Hermitian systems.…

Quantum Physics · Physics 2021-02-19 Stefano Longhi

A diagonalizable non-Hermitian Hamiltonian having a real spectrum may be used to define a unitary quantum system, if one modifies the inner product of the Hilbert space properly. We give a comprehensive and essentially self-contained review…

Quantum Physics · Physics 2015-05-13 Ali Mostafazadeh

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

Pseudo-Hermitian field theories possess a global continuous ``similarity'' symmetry, interconnecting the theories with the same physical particle content and an identical mass spectrum. In their regimes with real spectra, within this family…

High Energy Physics - Theory · Physics 2024-01-12 Maxim N. Chernodub , Peter Millington

Suppressing the reflection from material interfaces or entire layer stacks across an extended spectral range is important for various applications. While many approaches have been described for this purpose, we look at the problem here from…

The physical aspects of partially coherent radiation interacting with deterministic non-Hermitian periodic materials remain largely unexplored in the statistical optics literature. Here, we consider the scattering of partially coherent…

Optics · Physics 2019-10-02 Paulo A. Brandão , S. B. Cavalcanti

Two conditions on symmetries are identified as necessary for a linear scattering system to be able to rotate the linear polarisation of light: Lack of at least one mirror plane of symmetry and electromagnetic duality symmetry. Duality…

We study symmetries of open bosonic systems in the presence of laser pumping. Non-Hermitian Hamiltonians describing these systems can be parity-time (${\cal{PT}}$) symmetric in special cases only. Systems exhibiting this symmetry are…

Quantum Physics · Physics 2020-11-23 Ewelina Lange , Grzegorz Chimczak , Anna Kowalewska-Kudłaszyk , Karol Bartkiewicz

The relation between symmetries and local conservation laws, known as Noether's theorem, plays an important role in modern theoretical physics. As a discrete analog of the differentiable physical system, a good numerical scheme should admit…

Computational Physics · Physics 2019-04-09 Qiang Chen , Xiaojun Hao , Chuanchuan Wang , Xiaoyang Wang , Xiang Chen , Lifei Geng

Two alternative scenarios are shown possible in Quantum Mechanics working with non-Hermitian $PT-$symmetric form of observables. While, usually, people assume that $P$ is a self-adjoint indefinite metric in Hilbert space (and that their…

Quantum Physics · Physics 2007-05-23 Miloslav Znojil

We investigate conservation laws in the quantum mechanics of closed systems. We review an argument showing that exact decoherence implies the exact conservation of quantities that commute with the Hamiltonian including the total energy and…

General Relativity and Quantum Cosmology · Physics 2009-10-22 James B. Hartle , Raymond Laflamme , Donald Marolf

Recently, it was established that there exists a direct relation between the non-Hermitian skin effects, -strong dependence of spectra on boundary conditions for non-Hermitian Hamiltonians-, and boundary zero modes for Hermitian topological…

Mesoscale and Nanoscale Physics · Physics 2020-07-10 Nobuyuki Okuma , Masatoshi Sato

Pseudo-Hermitian operators generalize the concept of Hermiticity. This class of operators includes the quasi-Hermitian operators, which reformulate quantum theory while retaining real-valued measurement outcomes and unitary time evolution.…

Quantum Physics · Physics 2023-06-08 Jacob L. Barnett

Non-Hermitian disordered systems have emerged as a central arena in modern physics, with ramifications spanning condensed matter, quantum, statistical, and high energy contexts. The same principles also underlie phenomena beyond physics,…

Mesoscale and Nanoscale Physics · Physics 2026-03-24 Kohei Kawabata , Shinsei Ryu

The forward and backward scattering off linear systems with discrete rotational symmetries R_z (2{\pi} /n) with n $\ge$ 3 are shown to be restricted by symmetry reasons. Along the symmetry axis, forward scattering can only be helicity…

Optics · Physics 2013-11-28 Ivan Fernandez-Corbaton

Spectra of bulk or edges in topological insulators are often made complex by non-Hermiticity. Here, we show that symmetry protection enables entirely real spectra for both bulk and edges even in non-Hermitian topological insulators. In…

Mesoscale and Nanoscale Physics · Physics 2020-09-11 Kohei Kawabata , Masatoshi Sato

This study investigates pseudo-Hermitian quantum mechanics, where the Hamiltonian satisfies a modified Hermiticity condition. We extend the uncertainty relation for such systems, demonstrating its equivalence to the standard Hermitian case…

Quantum Physics · Physics 2025-08-11 Boubakeur Khantoul , Bilel Hamil , Amar Benchikha

We prove that $p $-harmonic systems with antisymmetric potentials can be written in divergence form as a conservation law. This extends to the $p$-harmonic framework the original work from 2006 of the second author for $p=2$…

Analysis of PDEs · Mathematics 2023-11-08 Francesca Da Lio , Tristan Rivière

Pseudo-Hermitian (including $\mathcal{PT}$-symmetric) field theories support phenomenology that cannot be replicated in standard Hermitian theories. We describe a concrete example in which the vortex solutions that are realised in a…

High Energy Physics - Theory · Physics 2025-11-19 R. A. Battye , S. J. Cotterill , P. Millington

Usually duality process keeps energy spectrum invariant. In this paper, we provide a duality, which keeps entanglement spectrum invariant, in order to diagnose quantum entanglement of non-Hermitian non-interacting fermionic systems. We…

Mesoscale and Nanoscale Physics · Physics 2021-07-13 Li-Mei Chen , Shuai A. Chen , Peng Ye