3,532 research outputs found
Q-stars and charged q-stars
We present the formalism of q-stars with local or global U(1) symmetry. The
equations we formulate are solved numerically and provide the main features of
the soliton star. We study its behavior when the symmetry is local in contrast
to the global case. A general result is that the soliton remains stable and
does not decay into free particles and the electrostatic repulsion preserves it
from gravitational collapse. We also investigate the case of a q-star with
non-minimal energy-momentum tensor and find that the soliton is stable even in
some cases of collapse when the coupling to gravity is absent.Comment: Latex, 19pg, 12 figures. Accepted in Phys. Rev.
Turing jumps through provability
Fixing some computably enumerable theory , the
Friedman-Goldfarb-Harrington (FGH) theorem says that over elementary
arithmetic, each formula is equivalent to some formula of the form
provided that is consistent. In this paper we give various
generalizations of the FGH theorem. In particular, for we relate
formulas to provability statements which
are a formalization of "provable in together with all true
sentences". As a corollary we conclude that each is
-complete. This observation yields us to consider a recursively
defined hierarchy of provability predicates which look a lot
like except that where calls upon the
oracle of all true sentences, the recursively
calls upon the oracle of all true sentences of the form . As such we obtain a `syntax-light' characterization of
definability whence of Turing jumps which is readily extended
beyond the finite. Moreover, we observe that the corresponding provability
predicates are well behaved in that together they provide a
sound interpretation of the polymodal provability logic
Chromofields of Strings and Baryons
We calculate color electric fields of quark/antiquark () and 3
quark () systems within the chromodielectric model (CDM). We explicitly
evaluate the string tension of flux tubes in the --system and analyze
their profile. To reproduce results of lattice calculations we use a bag
pressure from which an effective strong coupling constant
follows. With these parameters we get a shaped
configuration for large --systems.Comment: Contributions to QNP 2002, Quarks and Nuclear Physics, Juelich,
Germany 3 pages, 10 eps figure
Extended bound states and resonances of two fermions on a periodic lattice
The high- cuprates are possible candidates for d-wave superconductivity,
with the Cooper pair wave function belonging to a non-trivial irreducible
representation of the lattice point group. We argue that this d-wave symmetry
is related to a special form of the fermionic kinetic energy and does not
require any novel pairing mechanism. In this context, we present a detailed
study of the bound states and resonances formed by two lattice fermions
interacting via a non-retarded potential that is attractive for nearest
neighbors but repulsive for other relative positions. In the case of strong
binding, a pair formed by fermions on adjacent lattice sites can have a small
effective mass, thereby implying a high condensation temperature. For a weakly
bound state, a pair with non-trivial symmetry tends to be smaller in size than
an s-wave pair. These and other findings are discussed in connection with the
properties of high- cuprate superconductors.Comment: 21 pages, RevTeX, 4 Postscript figures, arithmetic errors corrected.
An abbreviated version (no appendix) appeared in PRB on March 1, 199
A Dynamical Model of Color Confinement
A dynamical model of confinement based on a transport theoretical description
of the Friedberg-Lee model is extended to explicit color degrees of freedom.
The string tension is reproduced by an adiabatic string formation from the
nucleon ground state. Color isovector oscillation modes of a -system
are investigated for a wide range of relative -momenta and the
dynamical impact of color confinement on the quark motion is shown.Comment: 12 pages plus 5 figure
Q-stars in extra dimensions
We study q-stars with global and local U(1) symmetry in extra dimensions in
asymptotically anti de Sitter or flat spacetime. The behavior of the mass,
radius and particle number of the star is quite different in 3 dimensions, but
in 5, 6, 8 and 11 dimensions is similar to the behavior in 4.Comment: 18 pages, to appear in Phys. Rev.
Nuclear and Particle Physics applications of the Bohm Picture of Quantum Mechanics
Approximation methods for calculating individual particle/ field motions in
spacetime at the quantum level of accuracy (a key feature of the Bohm Picture
of Quantum Mechanics (BP)), are studied. Modern textbook presentations of
Quantum Theory are used throughout, but only to provide the necessary, already
existing, tested formalisms and calculational techniques. New coherent
insights, reinterpretations of old solutions and results, and new (in principle
testable) quantitative and qualitative predictions, can be obtained on the
basis of the BP that complete the standard type of postdictions and
predictions.Comment: 41 page
EYM equations in the presence of q-stars
We study Einstein-Yang-Mills equations in the presence of gravitating
non-topological soliton field configurations, of q-ball type. We produce
numerical solutions, stable with respect to gravitational collapse and to
fission into free particles, and we study the effect of the field strength and
the eigen-frequency to the soliton parameters. We also investigate the
formation of such soliton stars when the spacetime is asymptotically anti de
Sitter.Comment: 11 pages, to appear in Phys. Rev.
Large metric perturbations from rescattering
We study numerically evolution of metric perturbations during reheating in a
model with two fields and a strong parametric resonance. Our calculation is
fully nonlinear and includes gravity but is restricted to spherical symmetry.
In this model, super-Hubble metric perturbations can grow during reheating only
due to effects nonlinear in fluctuations of the fields. We find that they
indeed grow and, soon after the growth begins, dominate variances of the metric
functions. Thus, the metric functions become smooth but varying significantly
over large scales. Their profiles at late times are interpreted as signalling a
gravitational instability and formation of a black hole.Comment: 9 pages, revtex, 4 figures; corrected typo in eq. (1). Time variable
in the plots was slightly messed up: fixed in v3 (a cosmetic change
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