522 research outputs found
Two-parametric PT-symmetric quartic family
We describe a parametrization of the real spectral locus of the
two-parametric family of PT-symmetric quartic oscillators. For this family, we
find a parameter region where all eigenvalues are real, extending the results
of Dorey, Dunning, Tateo and Shin.Comment: 23 pages, 15 figure
Generalized Faddeev equations in the AGS form for deuteron stripping with explicit inclusion of target excitations and Coulomb interaction
Theoretical description of reactions in general, and the theory for
reactions, in particular, needs to advance into the new century. Here deuteron
stripping processes off a target nucleus consisting of nucleons are
treated within the framework of the few-body integral equations theory. The
generalized Faddeev equations in the AGS form, which take into account the
target excitations, with realistic optical potentials provide the most advanced
and complete description of the deuteron stripping. The main problem in
practical application of such equations is the screening of the Coulomb
potential, which works only for light nuclei. In this paper we present a new
formulation of the Faddeev equations in the AGS form taking into account the
target excitations with explicit inclusion of the Coulomb interaction. By
projecting the -body operators onto target states, matrix three-body
integral equations are derived which allow for the incorporation of the excited
states of the target nucleons. Using the explicit equations for the partial
Coulomb scattering wave functions in the momentum space we present the AGS
equations in the Coulomb distorted wave representation without screening
procedure. We also use the explicit expression for the off-shell two-body
Coulomb scattering -matrix which is needed to calculate the effective
potentials in the AGS equations. The integrals containing the off-shell Coulomb
T-matrix are regularized to make the obtained equations suitable for
calculations. For and nucleon-target nuclear interactions we assume the
separable potentials what significantly simplifies solution of the AGS
equations.Comment: 34 pages, 13 figure
The Effect of Random Surface Inhomogeneities on Microresonator Spectral Properties: Theory and Modeling at Millimeter Wave Range
The influence of random surface inhomogeneities on spectral properties of
open microresonators is studied both theoretically and experimentally. To solve
the equations governing the dynamics of electromagnetic fields the method of
eigen-mode separation is applied previously developed with reference to
inhomogeneous systems subject to arbitrary external static potential. We prove
theoretically that it is the gradient mechanism of wave-surface scattering
which is the highly responsible for non-dissipative loss in the resonator. The
influence of side-boundary inhomogeneities on the resonator spectrum is shown
to be described in terms of effective renormalization of mode wave numbers
jointly with azimuth indices in the characteristic equation. To study
experimentally the effect of inhomogeneities on the resonator spectrum, the
method of modeling in the millimeter wave range is applied. As a model object
we use dielectric disc resonator (DDR) fitted with external inhomogeneities
randomly arranged at its side boundary. Experimental results show good
agreement with theoretical predictions as regards the predominance of the
gradient scattering mechanism. It is shown theoretically and confirmed in the
experiment that TM oscillations in the DDR are less affected by surface
inhomogeneities than TE oscillations with the same azimuth indices. The DDR
model chosen for our study as well as characteristic equations obtained
thereupon enable one to calculate both the eigen-frequencies and the Q-factors
of resonance spectral lines to fairly good accuracy. The results of
calculations agree well with obtained experimental data.Comment: 17+ pages, 5 figure
Photoproduction of Long-Lived Holes and Electronic Processes in Intrinsic Electric Fields Seen through Photoinduced Absorption and Dichroism in Ca_3Ga_{2-x}Mn_xGe_3O_{12} Garnets
Long-lived photoinduced absorption and dichroism in the
Ca_3Ga_{2-x}Mn_xGe_3O_{12} garnets with x < 0.06 were examined versus
temperature and pumping intensity. Unusual features of the kinetics of
photoinduced phenomena are indicative of the underlying electronic processes.
The comparison with the case of Ca_3Mn_2Ge_3O_{12}, explored earlier by the
authors, permits one to finally establish the main common mechanisms of
photoinduced absorption and dichroism caused by random electric fields of
photoproduced charges (hole polarons). The rate of their diffusion and
relaxation through recombination is strongly influenced by the same fields,
whose large statistical straggling is responsible for a broad continuous set of
relaxation components (observed in the relaxation time range from 1 to about
1000 min). For Ca_3Ga_{2-x}Mn_xGe_3O_{12}, the time and temperature dependences
of photoinduced absorption and dichroism bear a strong imprint of structure
imperfection increasing with x.Comment: 20 pages, 10 figure
Spectral dependence of photoinduced spin precession in DyFeO3
Spin precession was nonthermally induced by an ultrashort laser pulse in
orthoferrite DyFeO3 with a pump-probe technique. Both circularly and linearly
polarized pulses led to spin precessions; these phenomena are interpreted as
the inverse Faraday effect and the inverse Cotton-Mouton effect, respectively.
For both cases, the same mode of spin precession was excited; the precession
frequencies and polarization were the same, but the phases of oscillations were
different. We have shown theoretically and experimentally that the analysis of
phases can distinguish between these two mechanisms. We have demonstrated
experimentally that in the visible region, the inverse Faraday effect was
dominant, whereas the inverse Cotton-Mouton effect became relatively prominent
in the near-infrared region.Comment: 27 pages, 8 figure
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