4,291 research outputs found
Exact solutions to the time-dependent supersymmetric muliphoton Jaynes-Cummings model and the Chiao-Wu model
By using both the Lewis-Riesenfeld invariant theory and the invariant-related
unitary transformation formulation, the present paper obtains the exact
solutions to the time-dependent supersymmetric two-level multiphoton
Jaynes-Cummings model and the Chiao-Wu model that describes the propagation of
a photon inside the optical fiber. On the basis of the fact that the two-level
multiphoton Jaynes-Cummings model possesses the supersymmetric structure, an
invariant is constructed in terms of the supersymmetric generators by working
in the sub-Hilbert-space corresponding to a particular eigenvalue of the
conserved supersymmetric generators (i.e., the time-independent invariant). By
constructing the effective Hamiltonian that describes the interaction of the
photon with the medium of the optical fiber, it is further verified that the
particular solution to the Schr\"{o}dinger equation is the eigenfunction of the
second-quantized momentum operator of photons field. This, therefore, means
that the explicit expression (rather than the hidden form that involves the
chronological product) for the time-evolution operator of wave function is
obtained by means of the invariant theories.Comment: 14 pages, Latex. This is a revised version of the published paper:
Shen J Q, Zhu H Y 2003 Ann. Phys.(Leipzig) Vol.12 p.131-14
A unified approach to exact solutions of time-dependent Lie-algebraic quantum systems
By using the Lewis-Riesenfeld theory and the invariant-related unitary
transformation formulation, the exact solutions of the {\it time-dependent}
Schr\"{o}dinger equations which govern the various Lie-algebraic quantum
systems in atomic physics, quantum optics, nuclear physics and laser physics
are obtained. It is shown that the {\it explicit} solutions may also be
obtained by working in a sub-Hilbert-space corresponding to a particular
eigenvalue of the conserved generator ({\it i. e.}, the {\it time-independent}
invariant) for some quantum systems without quasi-algebraic structures. The
global and topological properties of geometric phases and their adiabatic limit
in time-dependent quantum systems/models are briefly discussed.Comment: 11 pages, Latex. accepted by Euro. Phys. J.
Gravitomagnetic Field and Time-Dependent Spin-Rotation Coupling
The Kerr metric of spherically symmetric gravitational field is analyzed
through the coordinate transformation from the rotating frame to fixing frame,
and consequently that the inertial force field (with the exception of the
centrifugal force field) in the rotating system is one part of its
gravitomagnetic field is verified. We investigate the spin-rotation coupling
and, by making use of Lewis-Riesenfeld invariant theory, we obtain exact
solutions of the Schr\"{o}dinger equation of a spinning particle in a
time-dependent rotating reference frame. A potential application of these exact
solutions to the investigation of Earths rotating frequency fluctuation
by means of neutron-gravity interferometry experiment is briefly discussed in
the present paper.Comment: 6 pages, 0 figures, Late
New observational constraints on cosmology from radio quasars
Using a new recently compiled milliarcsecond compact radio data set of 120
intermediate-luminosity quasars in the redshift range , whose
statistical linear sizes show negligible dependence on redshifts and intrinsic
luminosity and thus represent standard rulers in cosmology, we constrain three
viable and most popular gravity models, where is the torsion scalar
in teleparallel gravity. Our analysis reveals that constraining power of the
quasars data (N=120) is comparable to the Union2.1 SN Ia data (N=580) for all
three models. Together with other standard ruler probes such as Cosmic
Microwave Background and Baryon Acoustic Oscillation distance measurements, the
present value of the matter density parameter obtained by quasars is
much lager than that derived from other observations. For two of the models
considered (CDM and CDM) a small but noticeable deviation from
CDM cosmology is present, while in the framework of CDM the
effective equation of state may cross the phantom divide line at lower
redshifts. These results indicate that intermediate-luminosity quasars could
provide an effective observational probe comparable to SN Ia at much higher
redsifts, and gravity is a reasonable candidate for the modified gravity
theory
Testing and selecting cosmological models with ultra-compact radio quasars
In this paper, we place constraints on four alternative cosmological models
under the assumption of the spatial flatness of the Universe: CPL, EDE, GCG and
MPC. A new compilation of 120 compact radio quasars observed by
very-long-baseline interferometry, which represents a type of new cosmological
standard rulers, are used to test these cosmological models. Our results show
that the fits on CPL obtained from the quasar sample are well consistent with
those obtained from BAO. For other cosmological models considered, quasars
provide constraints in agreement with those derived with other standard probes
at confidence level. Moreover, the results obtained from other
statistical methods including Figure of Merit, and statefinder
diagnostics indicate that: (1) Radio quasar standard ruler could provide better
statistical constraints than BAO for all cosmological models considered, which
suggests its potential to act as a powerful complementary probe to BAO and
galaxy clusters. (2) Turning to diagnostics, CPL, GCG and EDE models
can not be distinguished from each other at the present epoch. (3) In the
framework of statefinder diagnostics, MPC and EDE will deviate from
CDM model in the near future, while GCG model cannot be
distinguished from CDM model unless much higher precision
observations are available.Comment: 12 pages, 8 figures, 1 tabl
Ultra-compact structure in intermediate-luminosity radio quasars: building a sample of standard cosmological rulers and improving the dark energy constraints up to
In this paper, we present a new compiled milliarcsecond compact radio data
set of 120 intermediate-luminosity quasars in the redshift range . These quasars show negligible dependence on redshifts and intrinsic
luminosity, and thus represents, in the standard model of cosmology, a fixed
comoving-length of standard ruler. We implement a new cosmology-independent
technique to calibrate the linear size of of this standard ruler as pc, which is the typical radius at which AGN jets become opaque
at the observed frequency GHz. In the framework of flat
CDM model, we find a high value of the matter density parameter,
, and a low value of the Hubble constant,
, which is in excellent
agreement with the CMB anisotropy measurements by \textit{Planck}. We obtain
, at 68.3% CL
for the constant of a dynamical dark-energy model, which demonstrates no
significant deviation from the concordance CDM model. Consistent
fitting results are also obtained for other cosmological models explaining the
cosmic acceleration, like Ricci dark energy (RDE) or Dvali-Gabadadze-Porrati
(DGP) brane-world scenario. While no significant change in with redshift is
detected, there is still considerable room for evolution in and the
transition redshift at which departing from -1 is located at .
Our results demonstrate that the method extensively investigated in our work on
observational radio quasar data can be used to effectively derive cosmological
information. Finally, we find the combination of high-redshift quasars and
low-redshift clusters may provide an important source of angular diameter
distances, considering the redshift coverage of these two astrophysical probes.Comment: 36 pages, 5 tables, 16 figures, A&A, in pres
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