127 research outputs found
New symmetry current for massive spin-3/2 fields
We present several new results which will be of value to theorists working
with massive spin-3/2 vector-spinor fields as found, for example, in low and
intermediate energy hadron physics and also linearized supergravity. The
general lagrangian and propagator for a vector-spinor field in d-dimensions is
given. It is shown that the observables of the theory are invariant under a
novel continuous symmetry group which is also extended to an algebra. A new
technique is developed for exploring the consequences of the symmetry and a
previously unknown conserved vector current and charge are found. The current
leads to new interactions involving spin-3/2 particles and may have important
experimental consequences.Comment: 9 pages, references updated and minor change
Possible types of the evolution of vacuum shells around the de Sitter space
All possible evolution scenarios of a thin vacuum shell surrounding the
spherically symmetric de Sitter space have been determined and the
corresponding global geometries have been constructed. Such configurations can
appear at the final stage of the cosmological phase transition, when isolated
regions (islands) of the old vacuum remain. The islands of the old vacuum are
absorbed by the new vacuum, expand unlimitedly, or form black holes and
wormholes depending on the sizes of the islands as well as on the density and
velocity of the shells surrounding the islands.Comment: 3 pages, 1 figur
Dynamics of a thin shell in the Reissner-Nordstrom metric
We describe the dynamics of a thin spherically symmetric gravitating shell in
the Reissner-Nordstrom metric of the electrically charged black hole. The
energy-momentum tensor of electrically neutral shell is modelled by the perfect
fluid with a polytropic equation of state. The motion of a shell is described
fully analytically in the particular case of the dust equation of state. We
construct the Carter-Penrose diagrams for the global geometry of the eternal
black hole, which illustrate all possible types of solutions for moving shell.
It is shown that for some specific range of initial parameters there are
possible the stable oscillating motion of the shell transferring it
consecutively in infinite series of internal universes. We demonstrate also
that this oscillating type of motion is possible for an arbitrary polytropic
equation of state on the shell.Comment: 17 pages, 7 figure
Photoproduction and Radiative Decay of Spin 1/2 and 3/2 Pentaquarks
We study photoproduction and radiative decays of pentauqarks paying
particular attention to the differences between spin-1/2 and spin-3/2, positive
and negative parities of pentaquarks. Detailed study of these processes can not
only give crucial information about the spin, but also the parity of
pentaquarks.Comment: 14 pages, 7 figure
Protective role of natural and semi-synthetic tocopherols on TNFα-induced ros production and ICAM-1 and Cl-2 expression in ht29 intestinal epithelial cells
Vitamin E, a fat-soluble compound, possesses both antioxidant and non-antioxidant properties. In this study we evaluated, in intestinal HT29 cells, the role of natural tocopherols, α-Toc and δ-Toc, and two semi-synthetic derivatives, namely bis-δ-Toc sulfide (δ-Toc)2S and bis-δ-Toc disulfide (δ-Toc)2S2, on TNFα-induced oxidative stress, and intercellular adhesion molecule-1 (ICAM-1) and claudin-2 (Cl-2) expression. The role of tocopherols was compared to that of N-acetylcysteine (NAC), an antioxidant precursor of glutathione synthesis. The results show that all tocopherol containing derivatives used, prevented TNFα-induced oxidative stress and the increase of ICAM-1 and Cl-2 expression, and that (δ-Toc)2S and (δ-Toc)2S2 are more effective than δ-Toc and α-Toc. The beneficial effects demonstrated were due to tocopherol antioxidant properties, but suppression of TNFα-induced Cl-2 expression seems not only to be related with antioxidant ability. Indeed, while ICAM-1 expression is strongly related to the intracellular redox state, Cl-2 expression is TNFα-up-regulated by both redox and non-redox dependent mechanisms. Since ICAM-1 and Cl-2 increase intestinal bowel diseases, and cause excessive recruitment of immune cells and alteration of the intestinal barrier, natural and, above all, semi-synthetic tocopherols may have a potential role as a therapeutic support against intestinal chronic inflammation, in which TNFα represents an important proinflammatory mediator
Evolution of a vacuum shell in the Friedman-Schwarzschild world
The method of an effective potential is used to investigate the possible
types of evolution of vacuum shells in the Friedman-Schwarzschild world. Such
shells are assumed to emerge during phase transitions in the early Universe.
The possible global geometries are constructed for the Friedman- Schwarzschild
worlds. Approximate solutions to the equation of motion of a vacuum shell have
been found. The conditions under which the end result of the evolution of the
vacuum shells under consideration is the formation of black holes and wormholes
with baby universes inside have been found. The interior of this world can be a
closed, flat, or open Friedman universe.Comment: 12 pages, 4 figure
Dynamical measure and field theory models free of the cosmological constant problem
Summary of abstract Field theory models including gauge theories with SSB are
presented where the energy density of the true vacuum state (TVS) is zero
without fine tuning. The above models are constructed in the gravitational
theory where a measure of integration \Phi in the action is not necessarily
\sqrt{-g} but it is determined dynamically through additional degrees of
freedom. The ratio \Phi/\sqrt{-g} is a scalar field which can be solved in
terms of the matter degrees of freedom due to the existence of a constraint. We
study a few explicit field theory models where it is possible to combine the
solution of the cosmological constant problem with: 1) possibility for
inflationary scenario for the early universe; 2) spontaneously broken gauge
unified theories (including fermions). The models are free from the well known
problem of the usual scalar-tensor theories in what is concerned with the
classical GR tests. The only difference of the field equations in the Einstein
frame from the canonical equations of the selfconsistent system of Einstein's
gravity and matter fields, is the appearance of the effective scalar field
potential which vanishes in TVS without fine tuning.Comment: Extended version of the contribution to the fourth Alexander
Friedmann International Seminar on Gravitation and Cosmology; accepted for
publication in Phys. Rev. D; 31 page
Cosmological Time in Quantum Supergravity
The version of supergravity formulated by Ogievetsky and Sokatchev is almost
identical to the conventional theory, except that the cosmological
constant appears as a dynamical variable which is constant only by
virtue of the field equations. We consider the canonical quantisation of this
theory, and show that the wave function evolves with respect to a dynamical
variable which can be interpreted as a cosmological time parameter. The square
of the modulus of the wave function obeys a set of simple conservation
equations and can be interpreted as a probability density functional. The usual
problems associated with time in quantum gravity are avoided.Comment: 12 pages, LaTe
The QCD Membrane
In this paper we study spatially quenched, SU(N) Yang-Mills theory in the
large-N limit. The resulting reduced action shows the same formal look as the
Banks-Fischler-Shenker-Susskind M-theory action. The Weyl-Wigner-Moyal symbol
of this matrix model is the Moyal deformation of a p(=2)-brane action. Thus,
the large-N limit of the spatially quenched SU(N) Yang-Mills is seen to
describe a dynamical membrane. By assuming spherical symmetry we compute the
mass spectrum of this object in the WKB approximation.Comment: 14 pages, LaTeX, non figures; accepted for publication in
Class.Quant. Gra
Towards a solution of the cosmological constant problem
The standard model of elementary particle physics and the theory of general
relativity can be extended by the introduction of a vacuum variable which is
responsible for the near vanishing of the present cosmological constant (vacuum
energy density). The explicit realization of this vacuum variable can be via a
three-form gauge field, an aether-type velocity field, or any other field
appropriate for the description of the equilibrium state corresponding to the
Lorentz-invariant quantum vacuum. The extended theory has, without fine-tuning,
a Minkowski-type solution of the field equations with spacetime-independent
fields and provides, therefore, a possible solution of the main cosmological
constant problem.Comment: 7 pages; v6: published versio
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