We consider a spin-1/2 particle in the external magnetic field which couples to a harmonic oscillator through some pseudo-hermitian interaction. We find that the energy eigenvalues for this system are real even though the interaction is not PT-invariant.
The non PT-symmetric exactly solvable Hamiltonian describing a system of a fermion in the external magnetic field which couples to a harmonic oscillator through some pseudo-hermitian interaction is considered. We point out all properties of both of the original Mandal and the original Jaynes-Cummings Hamitonians. It is shown that these Hamiltonians are respectively pseudo-hermitian and hermitian REF _Ref536606452 \r \h \* MERGEFORMAT [1] REF _Ref536606454 \r \h [2]. Like the direct approach to invariant vector spaces used in Refs. REF _Ref536606456 \r \h [3] REF _Ref536606457 \r \h [4], we reveal the exact solvability of both the Mandal and Jaynes-Cummings Hamiltonians after expressing them in the position operator and the impulsion operator.
The non PT− symmetric exactly solvable Hamiltonian describing a system of a fermion in the external magnetic field that couples to a harmonic oscillator via some pseudo-hermitian interaction is considered. We highlight all of the properties of both the original Mandal and Jaynes-Cummings Hamiltonians. We show that the Mandal Hamiltonian HM is non hermitian and non invariant under the combined action of the parity operator P and the time-reversal operator T Even if the previous properties are not satisfied, it has been proved that the Mandal Hamiltonian HM is pseudo-hermitian with respect to P and with respect to σ3 also [1,2]. Thus, we show that the original Jaynes-Cummings Hamiltonian is hermitian. We show the exact solvability of both the Mandal and Jaynes-Cummings Hamiltonians after expressing them in the position operator and the impulsion operator, similar to the direct approach to invariant vector spaces used in Refs [3,4].
Exploiting the intimate connection of the problem of a charged spin-1 particle in a homogeneous magnetic field to that of a harmonic oscillator, it is demonstrated that the eigenvalues of the matrix operator S. pi for spin-1 and for a constant magnetic field are governed by a Hermitian matrix defined on the space of the particle number n and spin and are thus constrained to be real for any intensity of the external magnetic field H, thereby contradicting a recent affirmation of Weaver (1978) that for n=0, complex eigenvalues are present for sufficiently intense magnetic fields. The errors in Weaver's analysis which have led to complex eigenvalues as well as to an excessive number of eigenvalues compared with that demanded by the spin degrees of freedom are pointed out.
The η pseudo PT symmetry theory, denoted by the symbol η, explores the conditions under which non-Hermitian Hamiltonians can possess real spectra despite the violation of PT symmetry, that is the adjoint of H, denoted H^{†} is expressed as H^{†}=PTHPT. This theory introduces a new symmetry operator, η=PTη, which acts on the Hilbert space. The η pseudo PT symmetry condition requires the Hamiltonian to commute with the η operator, leading to real eigenvalues. We discuss some general implications of our results for the coupled non hermitian harmonic oscillator.