2,787 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.
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 New Approach to Solve the Low-lying States of the Schroedinger Equation
We review a new iterative procedure to solve the low-lying states of the
Schroedinger equation, done in collaboration with Richard Friedberg. For the
groundstate energy, the order iterative energy is bounded by a finite
limit, independent of ; thereby it avoids some of the inherent difficulties
faced by the usual perturbative series expansions. For a fairly large class of
problems, this new procedure can be proved to give convergent iterative
solutions. These convergent solutions include the long standing difficult
problem of a quartic potential with either symmetric or asymmetric minima.Comment: 54 pages, 3 figures given separatel
Gravity action on the rapidly varying metrics
We consider a four-dimensional simplicial complex and the minisuperspace
general relativity system described by the metric flat in the most part of the
interior of every 4-simplex with exception of a thin layer of thickness
along the every three-dimensional face where the metric
undergoes jump between the two 4-simplices sharing this face. At this jump would become discontinuity. Since, however, discontinuity of
the (induced on the face) metric is not allowed in general relativity, the
terms in the Einstein action tending to infinity at arise.
In the path integral approach, these terms lead to the pre-exponent factor with
\dfuns requiring that the induced on the faces metric be continuous, i. e. the
4-simplices fit on their common faces. The other part of the path integral
measure corresponds to the action being the sum of independent terms over the
4-simplices. Therefore this part of the path integral measure is the product of
independent measures over the 4-simplices. The result obtained is in accordance
with our previous one obtained from the symmetry considerations.Comment: 10 page
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
Confining potential in a color dielectric medium with parallel domain walls
We study quark confinement in a system of two parallel domain walls
interpolating different color dielectric media. We use the phenomenological
approach in which the confinement of quarks appears considering the QCD vacuum
as a color dielectric medium. We explore this phenomenon in QCD_2, where the
confinement of the color flux between the domain walls manifests, in a scenario
where two 0-branes (representing external quark and antiquark) are connected by
a QCD string. We obtain solutions of the equations of motion via first-order
differential equations. We find a new color confining potential that increases
monotonically with the distance between the domain walls.Comment: RevTex4, 5 pages, 1 figure; version to appear in Int. J. Mod. Phys.
One-dimensional Cooper pairing
We study electron pairing in a one-dimensional (1D) fermion gas at zero
temperature under zero- and finite-range, attractive, two-body interactions.
The binding energy of Cooper pairs (CPs) with zero total or center-of-mass
momentum (CMM) increases with attraction strength and decreases with
interaction range for fixed strength. The excitation energy of 1D CPs with
nonzero CMM display novel, unique properties. It satisfies a dispersion
relation with \textit{two} branches: a\ phonon-like \textit{linear }excitation
for small CP CMM; this is followed by roton-like \textit{quadratic} excitation
minimum for CMM greater than twice the Fermi wavenumber, but only above a
minimum threshold attraction strength. The expected quadratic-in-CMM dispersion
\textit{in vacuo }when the Fermi wavenumber is set to zero is recovered for
\textit{any% } coupling. This paper completes a three-part exploration
initiated in 2D and continued in 3D.Comment: 12 pages, 6 figure
Bogomol'nyi Equations of Maxwell-Chern-Simons vortices from a generalized Abelian Higgs Model
We consider a generalization of the abelian Higgs model with a Chern-Simons
term by modifying two terms of the usual Lagrangian. We multiply a dielectric
function with the Maxwell kinetic energy term and incorporate nonminimal
interaction by considering generalized covariant derivative. We show that for a
particular choice of the dielectric function this model admits both topological
as well as nontopological charged vortices satisfying Bogomol'nyi bound for
which the magnetic flux, charge and angular momentum are not quantized. However
the energy for the topolgical vortices is quantized and in each sector these
topological vortex solutions are infinitely degenerate. In the nonrelativistic
limit, this model admits static self-dual soliton solutions with nonzero finite
energy configuration. For the whole class of dielectric function for which the
nontopological vortices exists in the relativistic theory, the charge density
satisfies the same Liouville equation in the nonrelativistic limit.Comment: 30 pages(4 figures not included), RevTeX, IP/BBSR/93-6
Vortex solutions of a Maxwell-Chern-Simons field coupled to four-fermion theory
We find the static vortex solutions of the model of Maxwell-Chern-Simons
gauge field coupled to a (2+1)-dimensional four-fermion theory. Especially, we
introduce two matter currents coupled to the gauge field minimally: the
electromagnetic current and a topological current associated with the
electromagnetic current. Unlike other Chern-Simons solitons the N-soliton
solution of this theory has binding energy and the stability of the solutions
is maintained by the charge conservation laws.Comment: 7 pages, harvmac, To be published in Phys. Rev. D5
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