25 research outputs found
Non-Hermitian oscillator Hamiltonian and su(1,1): a way towards generalizations
The family of metric operators, constructed by Musumbu {\sl et al} (2007 {\sl
J. Phys. A: Math. Theor.} {\bf 40} F75), for a harmonic oscillator Hamiltonian
augmented by a non-Hermitian -symmetric part, is re-examined in the
light of an su(1,1) approach. An alternative derivation, only relying on
properties of su(1,1) generators, is proposed. Being independent of the
realization considered for the latter, it opens the way towards the
construction of generalized non-Hermitian (not necessarily -symmetric)
oscillator Hamiltonians related by similarity to Hermitian ones. Some examples
of them are reviewed.Comment: 11 pages, no figure; changes in title and in paragraphs 3 and 5;
final published versio
Metric Operators for Quasi-Hermitian Hamiltonians and Symmetries of Equivalent Hermitian Hamiltonians
We give a simple proof of the fact that every diagonalizable operator that
has a real spectrum is quasi-Hermitian and show how the metric operators
associated with a quasi-Hermitian Hamiltonian are related to the symmetry
generators of an equivalent Hermitian Hamiltonian.Comment: 6 pages, published versio
Calculation of the metric in the Hilbert space of a PT-symmetric model via the spectral theorem
In a previous paper (arXiv:math-ph/0604055) we introduced a very simple
PT-symmetric non-Hermitian Hamiltonian with real spectrum and derived a closed
formula for the metric operator relating the problem to a Hermitian one. In
this note we propose an alternative formula for the metric operator, which we
believe is more elegant and whose construction -- based on a backward use of
the spectral theorem for self-adjoint operators -- provides new insights into
the nature of the model.Comment: LaTeX, 6 page
Quasi-Hermitian supersymmetric extensions of a non-Hermitian oscillator Hamiltonian and of its generalizations
A harmonic oscillator Hamiltonian augmented by a non-Hermitian \pt-symmetric
part and its su(1,1) generalizations, for which a family of positive-definite
metric operators was recently constructed, are re-examined in a supersymmetric
context. Quasi-Hermitian supersymmetric extensions of such Hamiltonians are
proposed by enlarging su(1,1) to a
superalgebra. This allows the construction of new non-Hermitian Hamiltonians
related by similarity to Hermitian ones. Some examples of them are reviewed.Comment: 15 pages, no figure; published versio
Milne quantization for non-Hermitian systems
We generalize the Milne quantization condition to non-Hermitian systems. In the general case the underlying nonlinear Ermakov–Milne–Pinney equation needs to be replaced by a nonlinear integral differential equation. However, when the system is PT-symmetric or/and quasi/pseudo-Hermitian the equations simplify and one may employ the original energy integral to determine its quantization. We illustrate the working of the general framework with the Swanson model and two explicit examples for pairs of supersymmetric Hamiltonians. In one case both partner Hamiltonians are Hermitian and in the other a Hermitian Hamiltonian is paired by a Darboux transformation to a non-Hermitian one
Instabilities, nonhermiticity and exceptional points in the cranking model
A cranking harmonic oscillator model, widely used for the physics of fast
rotating nuclei and Bose-Einstein condensates, is re-investigated in the
context of PT-symmetry. The instability points of the model are identified as
exceptional points. It is argued that - even though the Hamiltonian appears
hermitian at first glance - it actually is not hermitian within the region of
instability.Comment: 4 pages, 1 figur
PT-symmetric deformations of Calogero models
We demonstrate that Coxeter groups allow for complex PT-symmetric deformations across the boundaries of all Weyl chambers. We compute the explicit deformations for the A2 and G2-Coxeter group and apply these constructions to Calogero–Moser–Sutherland models invariant under the extended Coxeter groups. The eigenspectra for the deformed models are real and contain the spectra of the undeformed case as subsystems
Hermitian versus non-Hermitian representations for minimal length uncertainty relations
We investigate four different types of representations of deformed canonical variables leading to generalized versions of Heisenberg's uncertainty relations resulting from noncommutative spacetime structures. We demonstrate explicitly how the representations are related to each other and study three characteristically different solvable models on these spaces, the harmonic oscillator, the manifestly non-Hermitian Swanson model and an intrinsically noncommutative model with Pöschl-Teller type potential. We provide an analytical expression for the metric in terms of quantities specific to the generic solution procedure and show that when it is appropriately implemented expectation values are independent of the particular representation. A recently proposed inequivalent representation resulting from Jordan twists is shown to lead to unphysical models. We suggest an anti PT-symmetric modification to overcome this shortcoming
The Quantum Effective Mass Hamilton-Jacobi Problem
In this article, the quantum Hamilton- Jacobi theory based on the position
dependent mass model is studied. Two effective mass functions having different
singularity structures are used to examine the Morse and Poschl- Teller
potentials. The residue method is used to obtain the solutions of the quantum
effective mass- Hamilton Jacobi equation. Further, it is shown that the
eigenstates of the generalized non-Hermitian Swanson Hamiltonian for Morse and
Poschl-Teller potentials can be obtained by using the Riccati equation without
solving a differential equation