1,650 research outputs found
Representations and Properties of Generalized Statistics
A generalization of statistics is proposed and developed. The
generalized quantum statistics is completely specified by a set of
Jacobson generators satisfying a set of triple algebraic relations.
Fock-Hilbert representations and Bargmann-Fock realizations are derived.Comment: 12 pages, to appear in IJMPA (2006
A Generalized Jaynes-Cummings Model: Nonlinear dynamical superalgebra and Supercoherent states
The generalization of the Jaynes-Cummings (GJC) Model is proposed. In this
model, the electromagnetic radiation is described by a Hamiltonian generalizing
the harmonic oscillator to take into account some nonlinear effects which can
occurs in the experimental situations. The dynamical superalgebra and
supercoherent states of the related model are explicitly constructed. A
relevant quantities (total number of particles, energy and atomic inversion)
are computed.Comment: 12 page
On the solution of non linear systems.
SIGLEAvailable from British Library Document Supply Centre- DSC:D37560/81 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Phase operators, temporally stable phase states, mutually unbiased bases and exactly solvable quantum systems
We introduce a one-parameter generalized oscillator algebra A(k) (that covers
the case of the harmonic oscillator algebra) and discuss its finite- and
infinite-dimensional representations according to the sign of the parameter k.
We define an (Hamiltonian) operator associated with A(k) and examine the
degeneracies of its spectrum. For the finite (when k < 0) and the infinite
(when k > 0 or = 0) representations of A(k), we construct the associated phase
operators and build temporally stable phase states as eigenstates of the phase
operators. To overcome the difficulties related to the phase operator in the
infinite-dimensional case and to avoid the degeneracy problem for the
finite-dimensional case, we introduce a truncation procedure which generalizes
the one used by Pegg and Barnett for the harmonic oscillator. This yields a
truncated generalized oscillator algebra A(k,s), where s denotes the truncation
order. We construct two types of temporally stable states for A(k,s) (as
eigenstates of a phase operator and as eigenstates of a polynomial in the
generators of A(k,s)). Two applications are considered in this article. The
first concerns physical realizations of A(k) and A(k,s) in the context of
one-dimensional quantum systems with finite (Morse system) or infinite
(Poeschl-Teller system) discrete spectra. The second deals with mutually
unbiased bases used in quantum information.Comment: Accepted for publication in Journal of Physics A: Mathematical and
Theoretical as a pape
Two-Photon Spectroscopy Between States of Opposite Parities
Magnetic- and electric-dipole two-photon absorption (MED-TPA), recently
introduced as a new spectroscopic technique for studying transitions between
states of opposite parities, is investigated from a theoretical point of view.
A new approximation, referred to as {\it weak quasi-closure approximation}, is
used together with symmetry adaptation techniques to calculate the transition
amplitude between states having well-defined symmetry properties. Selection
rules for MED-TPA are derived and compared to selection rules for
parity-forbidden electric-dipole two-photon absorption (ED-TPA).Comment: 7 pages, Revtex File, to be published in Physical Review
Origin and stability of the dipolar response in a family of tetragonal tungsten bronze relaxors
A new family of relaxor dielectrics with the tetragonal tungsten bronze
structure (nominal composition Ba6M3+Nb9O30, M3+ = Ga, Sc or In) were studied
using dielectric spectroscopy to probe the dynamic dipole response and
correlate this with the crystal structure as determined from powder neutron
diffraction. Independent analyses of real and imaginary parts of the complex
dielectric function were used to determine characteristic temperature
parameters, TVF, and TUDR, respectively. In each composition both these
temperatures correlated with the temperature of maximum crystallographic
strain, Tc/a determined from diffraction data. The overall behaviour is
consistent with dipole freezing and the data indicate that the dipole stability
increases with increasing M3+ cation size as a result of increased
tetragonality of the unit cell. Crystallographic data suggests that these
materials are uniaxial relaxors with the dipole moment predominantly restricted
to the B1 cation site in the structure. Possible origins of the relaxor
behaviour are discussed.Comment: Main article 32 pages, 8 figures; Supplementary data 24 pages, 4
figure
Star-Like Micelles with Star-Like Interactions: A quantitative Evaluation of Structure Factor and Phase Diagram
PEP-PEO block copolymer micelles offer the possibility to investigate phase
behaviour and interactions of star polymers (ultra-soft colloids). A star-like
architecture is achieved by an extremely asymmetric block ratio (1:20).
Micellar functionality f can be smoothly varied by changing solvent composition
(interfacial tension). Structure factors obtained by SANS can be quantitatively
described in terms of an effective potential developed for star polymers. The
experimental phase diagram reproduces to a high level of accuracy the predicted
liquid/solid transition. Whereas for intermediate f a bcc phase is observed,
for high f the formation of a fcc phase is preempted by glass formation.Comment: 5 pages, 4 figures, PRL in pres
Electronic, mechanical, thermodynamic and optical properties of CdS under pressure
We report high pressure study of CdS using the full-potential linear augmented plane wave (FP-LAPW) method based on density functional theory approach. In this approach, generalized gradient approximation (GGA) and Engel- Vosko generalized gradient approximation (EV-GGA) have been used for the exchange correlation potential in the calculations. The equilibrium lattice constant, electronic band structure, elastic constants, Debye temperature and melting temperature of binary solid CdS have been calculated under ambient and high pressure. Furthermore, the linear optical properties such as dielectric function, absorption, optical conductivity reflectivity, refractive index and energy loss are computed and analyzed in detail within the energy range up to 14 eV. The obtained results are in good agreement with earlier reported experimental and other theoretical results
The Moyal Bracket in the Coherent States framework
The star product and Moyal bracket are introduced using the coherent states
corresponding to quantum systems with non-linear spectra. Two kinds of coherent
state are considered. The first kind is the set of Gazeau-Klauder coherent
states and the second kind are constructed following the Perelomov-Klauder
approach. The particular case of the harmonic oscillator is also discussed.Comment: 13 page
Statistical properties of Klauder-Perelomov coherent states for the Morse potential
We present in this paper a realistic construction of the coherent states for
the Morse potential using the Klauder-Perelomov approach . We discuss the
statistical properties of these states, by deducing the Q- and P-distribution
functions. The thermal expectations for the quantum canonical ideal gas of the
Morse oscillators are also calculated
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