316 research outputs found
Suppression of inhomogeneous broadening in rf spectroscopy of optically trapped atoms
We present a novel method for reducing the inhomogeneous frequency broadening
in the hyperfine splitting of the ground state of optically trapped atoms. This
reduction is achieved by the addition of a weak light field, spatially
mode-matched with the trapping field and whose frequency is tuned in-between
the two hyperfine levels. We experimentally demonstrate the new scheme with Rb
85 atoms, and report a 50-fold narrowing of the rf spectrum
Oscillation of the tunnel splitting in nanospin systems within the particle mapping formalism
The oscillation of tunnel splitting in the biaxial spin system within
magnetic field along the anisotropy axis is analyzed within the particle
mapping approach, rather than in the (\theta-\phi) spin coherent-state
representation. In our mapping procedure, the spin system is transformed into a
particle moving in the restricted geometry whose wave function subjects
to the boundary condition involving additional phase shift. We obtain the new
topological phase that plays the same role as the Wess-Zumino action in spin
coherent-state representation. Considering the interference of two possible
trajectories, instanton and anti-instanton, we get the identical condition for
the field at which tunneling is quenched, with the previous result within spin
coherent-state representation.Comment: 11 pages, 1 figure; Some typographical errors have been correcte
Close encounters of a rotating star with planets in parabolic orbits of varying inclination and the formation of Hot Jupiters
(abbreviated) We extend the theory of close encounters of a planet on a
parabolic orbit with a star to include the effects of tides induced on the
central rotating star. Orbits with arbitrary inclination to the stellar
rotation axis are considered. We obtain results both from an analytic treatment
and numerical one that are in satisfactory agreement. These results are applied
to the initial phase of the tidal circularisation problem. We find that both
tides induced in the star and planet can lead to a significant decrease of the
orbital semi-major axis for orbits having periastron distances smaller than 5-6
stellar radii (corresponding to periods days after the
circularisation has been completed) with tides in the star being much stronger
for retrograde orbits compared to prograde orbits. We use the simple Skumanich
law for the stellar rotation with its rotational period equal to one month at
the age of 5Gyr. The strength of tidal interactions is characterised by
circularisation time scale, defined as a time scale of evolution of
the planet's semi-major axis due to tides considered as a function of orbital
period after the process of tidal circularisation has been completed.
We find that the ratio of the initial circularisation time scales corresponding
to prograde and retrograde orbits is of order 1.5-2 for a planet of one Jupiter
mass and four days. It grows with the mass of the planet, being
of order five for a five Jupiter mass planet with the same . Thus, the
effect of stellar rotation may provide a bias in the formation of planetary
systems having planets on close orbits around their host stars, as a
consequence of planet-planet scattering, favouring systems with retrograde
orbits. The results may also be applied to the problem of tidal capture of
stars in young stellar clusters.Comment: to be published in Celestial Mechanics and Dynamical Astronom
Relativistic Models for Binary Neutron Stars with Arbitrary Spins
We introduce a new numerical scheme for solving the initial value problem for
quasiequilibrium binary neutron stars allowing for arbitrary spins. The coupled
Einstein field equations and equations of relativistic hydrodynamics are solved
in the Wilson-Mathews conformal thin sandwich formalism. We construct sequences
of circular-orbit binaries of varying separation, keeping the rest mass and
circulation constant along each sequence. Solutions are presented for
configurations obeying an n=1 polytropic equation of state and spinning
parallel and antiparallel to the orbital angular momentum. We treat stars with
moderate compaction ((m/R) = 0.14) and high compaction ((m/R) = 0.19). For all
but the highest circulation sequences, the spins of the neutron stars increase
as the binary separation decreases. Our zero-circulation cases approximate
irrotational sequences, for which the spin angular frequencies of the stars
increases by 13% (11%) of the orbital frequency for (m/R) = 0.14 ((m/R) = 0.19)
by the time the innermost circular orbit is reached. In addition to leaving an
imprint on the inspiral gravitational waveform, this spin effect is measurable
in the electromagnetic signal if one of the stars is a pulsar visible from
Earth.Comment: 21 pages, 14 figures. A few explanatory sentences added and some
typos corrected. Accepted for publication in Phys. Rev.
Nonadiabatic approach to dimerization gap and optical absorption coefficient of the Su-Schrieffer-Heeger model
An analytical nonadiabatic approach has been developed to study the
dimerization gap and the optical absorption coefficient of the
Su-Schrieffer-Heeger model where the electrons interact with dispersive quantum
phonons. By investigating quantitatively the effects of quantum phonon
fluctuations on the gap order and the optical responses in this system, we show
that the dimerization gap is much more reduced by the quantum lattice
fluctuations than the optical absorption coefficient is. The calculated optical
absorption coefficient and the density of states do not have the
inverse-square-root singularity, but have a peak above the gap edge and there
exist a significant tail below the peak. The peak of optical absorption
spectrum is not directly corresponding to the dimerized gap. Our results of the
optical absorption coefficient agree well with those of the experiments in both
the shape and the peak position of the optical absorption spectrum.Comment: 14 pages, 7 figures. to be published in PR
Nonlinear atom optics and bright gap soliton generation in finite optical lattices
We theoretically investigate the transmission dynamics of coherent matter
wave pulses across finite optical lattices in both the linear and the nonlinear
regimes. The shape and the intensity of the transmitted pulse are found to
strongly depend on the parameters of the incident pulse, in particular its
velocity and density: a clear physical picture for the main features observed
in the numerical simulations is given in terms of the atomic band dispersion in
the periodic potential of the optical lattice. Signatures of nonlinear effects
due the atom-atom interaction are discussed in detail, such as atom optical
limiting and atom optical bistability. For positive scattering lengths, matter
waves propagating close to the top of the valence band are shown to be subject
to modulational instability. A new scheme for the experimental generation of
narrow bright gap solitons from a wide Bose-Einstein condensate is proposed:
the modulational instability is seeded in a controlled way starting from the
strongly modulated density profile of a standing matter wave and the solitonic
nature of the generated pulses is checked from their shape and their
collisional properties
Various features of quasiequilibrium sequences of binary neutron stars in general relativity
Quasiequilibrium sequences of binary neutron stars are numerically calculated
in the framework of the Isenberg-Wilson-Mathews (IWM) approximation of general
relativity. The results are presented for both rotation states of synchronized
spins and irrotational motion, the latter being considered as the realistic one
for binary neutron stars just prior to the merger. We assume a polytropic
equation of state and compute several evolutionary sequences of binary systems
composed of different-mass stars as well as identical-mass stars with adiabatic
indices gamma=2.5, 2.25, 2, and 1.8. From our results, we propose as a
conjecture that if the turning point of binding energy (and total angular
momentum) locating the innermost stable circular orbit (ISCO) is found in
Newtonian gravity for some value of the adiabatic index gamma_0, that of the
ADM mass (and total angular momentum) should exist in the IWM approximation of
general relativity for the same value of the adiabatic index.Comment: Text improved, some figures changed or deleted, new table, 38 pages,
31 figures, accepted for publication in Phys. Rev.
A ballistic motion disrupted by quantum reflections
I study a Lindblad dynamics modeling a quantum test particle in a Dirac comb
that collides with particles from a background gas. The main result is a
homogenization theorem in an adiabatic limiting regime involving large initial
momentum for the test particle. Over the time interval considered, the particle
would exhibit essentially ballistic motion if either the singular periodic
potential or the kicks from the gas were removed. However, the particle behaves
diffusively when both sources of forcing are present. The conversion of the
motion from ballistic to diffusive is generated by occasional quantum
reflections that result when the test particle's momentum is driven through a
collision near to an element of the half-spaced reciprocal lattice of the Dirac
comb.Comment: 54 pages. I rewrote the introduction and simplified some of the
presentatio
Theory of Coexistence of Superconductivity and Ferroelectricity : A Dynamical Symmetry Model
We propose and investigate a model for the coexistence of Superconductivity
(SC) and Ferroelectricity (FE) based on the dynamical symmetries for
the pseudo-spin SC sector, for the displaced oscillator FE sector, and
for the composite system. We assume a minimal
symmetry-allowed coupling, and simplify the hamiltonian using a double mean
field approximation (DMFA). A variational coherent state (VCS) trial
wave-function is used for the ground state: the energy, and the relevant order
parameters for SC and FE are obtained. For positive sign of the SC-FE coupling
coefficient, a non-zero value of either order parameter can suppress the other
(FE polarization suppresses SC and vice versa). This gives some support to
"Matthias' Conjecture" [1964], that SC and FE tend to be mutually exclusive.
For such a Ferroelectric Superconductor we predict: a) the SC gap
(and ) will increase with increasing applied pressure when pressure
quenches FE as in many ferroelectrics, and b) the FE polarization will increase
with increaesing magnetic field up to . The last result is equivalent to
the prediction of a new type of Magneto-Electric Effect in a coexistent SC-FE
material. Some discussion will be given of the relation of these results to the
cuprate superconductors.Comment: 46 page
Enlightened or Delusional?: Differentiating Religious, Spiritual, and Transpersonal Experiences from Psychopathology
Psychological diagnosis faces unique challenges when used to differentiate nonpsychopathological religious/spiritual/transpersonal (R/S/T) experiences from those that might evidence psychopathology, particularly considering the diversity of such experiences and the value-laden assumptions inherent in most diagnostic practices. Theoretical and pragmatic problems related to the diagnostic category, Religious and Spiritual Problem, as contained in the Diagnostic and Statistical Manual of Mental Disorders are discussed. Attention is paid to identifying potential biases and errors in using, or failing to use, this diagnostic category, particularly as related to developing culturally sensitive diagnoses. Specific methods, including psychometric approaches, for evaluating R/S/T experiences that may range from healthy to psychopathological are reviewed and recommendations are presented for improving current diagnostic practices and furthering needed research.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
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