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Exceptional points are spectral degeneracies of non-Hermitian systems where both eigenfrequencies and eigenmodes coalesce. The eigenfrequency sensitivities near an exceptional point are significantly enhanced, whereby they diverge directly…

Computational Physics · Physics 2024-05-14 Felix Binkowski , Julius Kullig , Fridtjof Betz , Lin Zschiedrich , Andrea Walther , Jan Wiersig , Sven Burger

The exotic physics emerging at singularities has long attracted intense theoretical and experimental attention. In non-Hermitian systems, exceptional points (EPs), unique spectral singularities, have given rise to a host of intriguing wave…

Optics · Physics 2026-04-14 Kai Bai , Chen Lin , Jia-Zheng Li , Meng Xiao

Exceptional points (EPs) are remarkable spectral degeneracies in a non-Hermitian system's parameter space, where both eigenvalues and eigenstates coalesce. Here, we show that in non-Hermitian molecular chiral systems the position of EPs in…

Quantum Physics · Physics 2025-12-02 Nicola Mayer , Alexander Löhr , Nimrod Moiseyev , Misha Ivanov , Olga Smirnova

The first step when solving an infinite-dimensional eigenvalue problem is often to discretize it. We show that one must be extremely careful when discretizing nonlinear eigenvalue problems. Using examples, we show that discretization can:…

Numerical Analysis · Mathematics 2023-05-04 Matthew J. Colbrook , Alex Townsend

Exceptional points (EPs) are singularities in the parameter space of a non-Hermitian system where eigenenergies and eigenstates coincide. They hold promise for enhancing sensing applications, but this is limited by the divergence of shot…

Optics · Physics 2025-04-07 Xu Zheng , Y. D. Chong

Many novel properties of non-Hermitian systems are found at or near the exceptional points-branch points of complex energy surfaces at which eigenvalues and eigenvectors coalesce. In particular, higher-order exceptional points can result in…

Optics · Physics 2019-02-21 Shubo Wang , Bo Hou , Weixin Lu , Yuntian Chen , Z. Q. Zhang , C. T. Chan

Non-Hermitian Hamiltonians can give rise to exceptional points (EPs) which have been extensively explored with nominally identical coupled resonators. Here a non-Hermitian electromechanical system is developed which hosts vibration modes…

Mesoscale and Nanoscale Physics · Physics 2019-02-06 P. Renault , H. Yamaguchi , I. Mahboob

Understanding the linear response of any system is the first step towards analyzing its linear and nonlinear dynamics, stability properties, as well as its behavior in the presence of noise. In non-Hermitian Hamiltonian systems, calculating…

Resolutions of identity for certain non-Hermitian Hamiltonians constructed from biorthogonal sets of their eigen- and associated functions are given for the spectral problem defined on entire axis. Non-Hermitian Hamiltonians under…

Mathematical Physics · Physics 2011-12-06 Alexander A. Andrianov , Andrey V. Sokolov

We investigate indeterminate points in discrete integrable system. They appear in singularity confinement phenomenon naturally. We develop a method to analyse indeterminate points of dynamical maps and using this method we clarify behaviour…

Exactly Solvable and Integrable Systems · Physics 2017-05-03 Yuki Wakimoto

Exceptional points (EPs) are truly non-Hermitian (NH) degeneracies where matrices become defective. The order of such an EP is given by the number of coalescing eigenvectors. On the one hand, most work focuses on studying $N$th-order EPs in…

Mesoscale and Nanoscale Physics · Physics 2024-11-11 Julius T. Gohsrich , Jacob Fauman , Flore K. Kunst

We calculate the exceptional points of the eigenvalues of several parameter-dependent Hamiltonian operators of mathematical and physical interest. We show that the calculation is greatly facilitated by the application of the discriminant to…

Quantum Physics · Physics 2019-11-26 Paolo Amore , Francisco M. Fernández

Exceptional points are singularities of eigenvalues and eigenvectors for complex values of, say, an interaction parameter. They occur universally and are square root branch point singularities of the eigenvalues in the vicinity of level…

Quantum Physics · Physics 2007-05-23 W. D. Heiss

Theories in physics can provide a kind of map of the physical system under investigation, showing all of the possible types of behavior which may occur. Certain points on the map are of greater significance than others, because they…

Quantum Physics · Physics 2023-07-26 C. A. Downing , O. I. R. Fox

We conduct a numerical study of wave localization in disordered three-dimensional non-Hermitian systems featuring exceptional points. The energy spectrum of a disordered non-Hermitian Hamiltonian, exhibiting both parity-time and…

Disordered Systems and Neural Networks · Physics 2025-09-30 C. Wang , X. R. Wang

Experiments near the lock-in region in maximally dissipative non-Hermitian systems, e.g., conventional laser gyroscopes near the deadband, have run up against the Petermann limit, where excess noise exactly cancels any scale-factor…

Exceptional points facilitate peculiar dynamics in non-Hermitian systems. Yet, in photonics, they have mainly been studied in the classical realm. In this work, we reveal the behavior of two-photon quantum states in non-Hermitian systems…

The dynamics of spontaneous emission of an atomic system is studied in the framework of an open quantum system. The resulting quantum master equation for the atomic system is non hermitian. The generator $\mathcal{L}$ can possess…

Quantum Physics · Physics 2016-03-23 Morag Am-Shallem , Ronnie Kosloff , Nimrod Moiseyev

We propose an idea of eigenstate clustering in non-Hermitian systems. We show that non-orthogonal eigenstates can be clustered around exceptional points and illustrate our idea on some models. We discuss that exponential localization of…

Quantum Physics · Physics 2020-09-03 Cem Yuce

An interplay of an exotic quantum holonomy and exceptional points is examined in one-dimensional Bose systems. The eigenenergy anholonomy, in which Hermitian adiabatic cycle induces nontrivial change in eigenenergies, can be interpreted as…

Quantum Physics · Physics 2013-07-16 Atushi Tanaka , Nobuhiro Yonezawa , Taksu Cheon