12 research outputs found
Asymptotic estimates for bound states in quantum waveguides coupled laterally through a narrow window
Consider the Laplacian in a straight planar strip of width , with the
Neumann boundary condition at a segment of length of one of the
boundaries, and Dirichlet otherwise. For small enough this operator has
a single eigenvalue ; we show that there are positive
such that . An analogous conclusion holds for a pair of Dirichlet strips, of
generally different widths, with a window of length in the common
boundary.Comment: LaTeX file, 12 pages, no figure
Non-analyticity of the groud state energy of the Hamiltonian for Hydrogen atom in non-relativistic QED
We derive the ground state energy up to the fourth order in the fine
structure constant for the translation invariant Pauli-Fierz
Hamiltonian for a spinless electron coupled to the quantized radiation field.
As a consequence, we obtain the non-analyticity of the ground state energy of
the Pauli-Fierz operator for a single particle in the Coulomb field of a
nucleus
The CWKB approach to non-reflecting potential and cosmological implications
We discuss the method of calculating the reflection coefficient using complex
trajectory WKB (CWKB) approximation. This enables us to give an interpretation
of non-reflecting nature of the potential under certain conditions and clarify
some points, reported incorrectly elsewhere [vs:ejp] for the potential
. We show that the repeated reflectios between the
turning points are essential, which most authors overlooked, in obtaining the
non-reflecting c ondition. We find that the considered repeated reflection
paths are in conformity with Bogolubov transformation technique. We discuss the
implications of the results when applied to the particle production scenario,
considering as a time variable and also stress the cosmological
implications of the result with reference to radiation domonated and de Sitter
spacetime.Comment: 9 pages, late
Resonant scattering of spin waves from a region of inhomogeneous magnetic field in a ferromagnetic film
The transmission of a dipole-dominated spin wave in a ferromagnetic film
through a localised inhomogeneity in the form of a magnetic field produced by a
dc current through a wire placed on the film surface was studied experimentally
and theoretically. It was shown that the amplitude and phase of the transmitted
wave can be simultaneously affected by the current induced field, a feature
that will be relevant for logic based on spin wave transport.
The direction of the current creates either a barrier or well for spin wave
transmission. The main observation is that the current dependence of the
amplitude of the spin wave transmitted through the well inhomogeneity is
non-monotonic. The dependence has a minimum and an additional maximum. A theory
was constructed to clarify the nature of the maximum. It shows that the
transmission of spin waves through the inhomogeneity can be considered as a
scattering process and that the additional maximum is a scattering resonance