1,268 research outputs found
Wigner Oscillators, Twisted Hopf Algebras and Second Quantization
By correctly identifying the role of central extension in the centrally
extended Heisenberg algebra h, we show that it is indeed possible to construct
a Hopf algebraic structure on the corresponding enveloping algebra U(h) and
eventually deform it through Drinfeld twist. This Hopf algebraic structure and
its deformed version U^F(h) are shown to be induced from a more fundamental
Hopf algebra obtained from the Schroedinger field/oscillator algebra and its
deformed version, provided that the fields/oscillators are regarded as
odd-elements of the super-algebra osp(1|2n). We also discuss the possible
implications in the context of quantum statistics.Comment: 23 page
Pulse Profiles, Accretion Column Dips and a Flare in GX 1+4 During a Faint State
The Rossi X-ray Timing Explorer (RXTE) spacecraft observed the X-ray pulsar
GX 1+4 for a period of 34 hours on July 19/20 1996. The source faded from an
intensity of ~20 mCrab to a minimum of <~0.7 mCrab and then partially recovered
towards the end of the observation. This extended minimum lasted ~40,000
seconds. Phase folded light curves at a barycentric rotation period of
124.36568 +/- 0.00020 seconds show that near the center of the extended minimum
the source stopped pulsing in the traditional sense but retained a weak dip
feature at the rotation period. Away from the extended minimum the dips are
progressively narrower at higher energies and may be interpreted as
obscurations or eclipses of the hot spot by the accretion column. The pulse
profile changed from leading-edge bright before the extended minimum to
trailing-edge bright after it. Data from the Burst and Transient Source
Experiment (BATSE) show that a torque reversal occurred <10 days after our
observation. Our data indicate that the observed rotation departs from a
constant period with a Pdot/P value of ~-1.5% per year at a 4.5 sigma
significance. We infer that we may have serendipitously obtained data, with
high sensitivity and temporal resolution about the time of an accretion disk
spin reversal. We also observed a rapid flare which had some precursor
activity, close to the center of the extended minimum.Comment: 19 pages, 6 figures, accepted for publication in Astrophysical
Journal (tentatively scheduled for vol. 529 #1, 20 Jan 2000
Non-positivity of Groenewold operators
A central feature in the Hilbert space formulation of classical mechanics is
the quantisation of classical Liouville densities, leading to what may be
termed term Groenewold operators. We investigate the spectra of the Groenewold
operators that correspond to Gaussian and to certain uniform Liouville
densities. We show that when the classical coordinate-momentum uncertainty
product falls below Heisenberg's limit, the Groenewold operators in the
Gaussian case develop negative eigenvalues and eigenvalues larger than 1.
However, in the uniform case, negative eigenvalues are shown to persist for
arbitrarily large values of the classical uncertainty product.Comment: 9 pages, 1 figures, submitted to Europhysics Letter
Baryon charge transfer and production asymmetry between Lambda^0 and antiLambda^0 in hadron interactions
The predictions were done for asymmetry between production spectra of
Lambda^0 and antiLambda^0 at the energy of LHC experiments. The value of A(s)
should be situated in the band between two curves that are calculated in
Quark-Gluon String Model with two possible values of intercept
alpha_{SJ}(0)=0,5 and 0,9. Both curves describe the asymmetries measured at
lower energies up to RHIC experiments. The data of H1 experiment can be fitted
only with alpha_{SJ}(0)=0,9.Comment: LateX, 7 pages and 2 figures, poster presentation at PANIC'05, Santa
Fe, October 200
Exact Evolution Operator on Non-compact Group Manifolds
Free quantal motion on group manifolds is considered. The Hamiltonian is
given by the Laplace -- Beltrami operator on the group manifold, and the
purpose is to get the (Feynman's) evolution kernel. The spectral expansion,
which produced a series of the representation characters for the evolution
kernel in the compact case, does not exist for non-compact group, where the
spectrum is not bounded. In this work real analytical groups are investigated,
some of which are of interest for physics. An integral representation for the
evolution operator is obtained in terms of the Green function, i.e. the
solution to the Helmholz equation on the group manifold. The alternative series
expressions for the evolution operator are reconstructed from the same integral
representation, the spectral expansion (when exists) and the sum over classical
paths. For non-compact groups, the latter can be interpreted as the (exact)
semi-classical approximation, like in the compact case. The explicit form of
the evolution operator is obtained for a number of non-compact groups.Comment: 32 pages, 5 postscript figures, LaTe
Dynamical noncommutativity
The model of dynamical noncommutativity is proposed. The system consists of
two interrelated parts. The first of them describes the physical degrees of
freedom with coordinates q^1, q^2, the second one corresponds to the
noncommutativity r which has a proper dynamics. After quantization the
commutator of two physical coordinates is proportional to the function of r.
The interesting feature of our model is the dependence of nonlocality on the
energy of the system. The more the energy, the more the nonlocality. The
lidding contribution is due to the mode of noncommutativity, however, the
physical degrees of freedom also contribute in nonlocality in higher orders in
\theta.Comment: published versio
Hard diffraction in hadron--hadron interactions and in photoproduction
Hard single diffractive processes are studied within the framework of the
triple--Pomeron approximation. Using a Pomeron structure function motivated by
Regge--theory we obtain parton distribution functions which do not obey
momentum sum rule. Based on Regge-- factorization cross sections for hard
diffraction are calculated. Furthermore, the model is applied to hard
diffractive particle production in photoproduction and in
interactions.Comment: 13 pages, Latex, 13 uuencoded figure
Higher-Derivative Boson Field Theories and Constrained Second-Order Theories
As an alternative to the covariant Ostrogradski method, we show that
higher-derivative relativistic Lagrangian field theories can be reduced to
second differential-order by writing them directly as covariant two-derivative
theories involving Lagrange multipliers and new fields. Despite the intrinsic
non-covariance of the Dirac's procedure used to deal with the constraints, the
explicit Lorentz invariance is recovered at the end. We develop this new
setting on the grounds of a simple scalar model and then its applications to
generalized electrodynamics and higher-derivative gravity are worked out. For a
wide class of field theories this method is better suited than Ostrogradski's
for a generalization to 2n-derivative theoriesComment: 31 pages, Plain Te
Quark-Gluon String Model Description of Baryon Production in K^{\pm}N Interactions
The process of baryon production in K p collisions at high energies is
considered in the framework of the Quark-Gluon String Model. The contribution
of the string-junction mechanism to the strange baryon production is analysed.
The results of numerical calculations are in reasonable agreement with the data
on inclusive spectra of p, Lambda, bar{Lambda}, and on the bar{Lambda}/Lambda
asymmetry. The predictions for Xi and Omega baryons are presented.Comment: 19 pages, 7 figure
The Moyal-Lie Theory of Phase Space Quantum Mechanics
A Lie algebraic approach to the unitary transformations in Weyl quantization
is discussed. This approach, being formally equivalent to the
-quantization, is an extension of the classical Poisson-Lie formalism
which can be used as an efficient tool in the quantum phase space
transformation theory.Comment: 15 pages, no figures, to appear in J. Phys. A (2001
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