2,518 research outputs found
Gravity on an extended brane in six-dimensional warped flux compactifications
We study linearized gravity in a six-dimensional Einstein-Maxwell model of
warped braneworlds, where the extra dimensions are compactified by a magnetic
flux. It is difficult to construct a strict codimension two braneworld with
matter sources other than pure tension. To overcome this problem we replace the
codimension two defect by an extended brane, with one spatial dimension
compactified on a Kaluza-Klein circle. Our background is composed of a warped,
axisymmetric bulk and one or two branes. We find that weak gravity sourced by
arbitrary matter on the brane(s) is described by a four-dimensional
scalar-tensor theory. We show, however, that the scalar mode is suppressed at
long distances and hence four-dimensional Einstein gravity is reproduced on the
brane.Comment: 20 pages, 7 figures; v2: references and comments added; v3: version
published in Physical Review
S-matrices for spinor particles on Reissner-Nordstr\"{o}m black holes
The scattering problems arising when considering the contribution of the
topologically inequivalent configurations of the spinors on
Reissner-Nordstr\"{o}m black holes to the Hawking radiation are correctly
stated. The corresponding -matrices are described and presented in the form
convenient to numerical computations.Comment: 11 pages, LaTe
Color Superconductivity in N=2 Supersymmetric Gauge Theories
We study vacuum structure of N=2 supersymmetric (SUSY) QCD, based on the
gauge group SU(2) with N_f=2 flavors of massive hypermultiplet quarks, in the
presence of non-zero baryon chemical potential (\mu). The theory has a
classical vacuum preserving baryon number symmetry, when a mass term, which
breaks N=2 SUSY but preserves N=1 SUSY, for the adjoint gauge chiral multiplet
(m_{ad}) is introduced. By using the exact result of N=2 SUSY QCD, we analyze
low energy effective potential at the leading order of perturbation with
respect to small SUSY breaking parameters, \mu and m_{ad}. We find that the
baryon number is broken as a consequence of the SU(2) strong gauge dynamics, so
that color superconductivity dynamically takes place at the non-SUSY vacuum.Comment: 15 pages, 9 figures, a figure and discussions added in Sec. 4,
version to appear in Phys. Rev.
Cosmological evolution of regularized branes in 6D warped flux compactifications
We study the cosmological evolution of extended branes in 6D warped flux
compactification models. The branes are endowed with the three ordinary spatial
dimensions, which are assumed to be homogeneous and isotropic, as well as an
internal extra dimension compactified on a circle. We embed these codimension 1
branes in a static bulk 6D spacetime, whose geometry is a solution of 6D
Einstein-Maxwell or Einstein-Maxwell-dilaton theories, corresponding to a
warped flux compactification. The brane matter consists of a complex scalar
field which is coupled to the bulk U(1) gauge field. In both models, we show
that there is critical point which the brane cannot cross as it moves in the
bulk. We study the cosmological behaviour, especially when the brane approaches
this critical point or one of the two conical singularities. In the present
setup where the bulk geometry is fixed, we find that the brane cosmology does
not coincide with the standard one in the low energy limit.Comment: 14 pages, 4 figures, references and discussions added, to appear in
PR
Static and symmetric wormholes respecting energy conditions in Einstein-Gauss-Bonnet gravity
Properties of -dimensional static wormhole solutions are
investigated in Einstein-Gauss-Bonnet gravity with or without a cosmological
constant . We assume that the spacetime has symmetries corresponding
to the isometries of an -dimensional maximally symmetric space with the
sectional curvature . It is also assumed that the metric is at
least and the -dimensional maximally symmetric subspace is
compact. Depending on the existence or absence of the general relativistic
limit , solutions are classified into general relativistic (GR)
and non-GR branches, respectively, where is the Gauss-Bonnet coupling
constant. We show that a wormhole throat respecting the dominant energy
condition coincides with a branch surface in the GR branch, otherwise the null
energy condition is violated there. In the non-GR branch, it is shown that
there is no wormhole solution for . For the matter field with
zero tangential pressure, it is also shown in the non-GR branch with
and that the dominant energy condition holds at the
wormhole throat if the radius of the throat satisfies some inequality. In the
vacuum case, a fine-tuning of the coupling constants is shown to be necessary
and the radius of a wormhole throat is fixed. Explicit wormhole solutions
respecting the energy conditions in the whole spacetime are obtained in the
vacuum and dust cases with and .Comment: 10 pages, 2 tables; v2, typos corrected, references added; v3,
interpretation of the solution for n=5 in section IV corrected; v4, a very
final version to appear in Physical Review
Bulk scalar emission from a rotating black hole pierced by a tense brane
We study the emission of scalar fields into the bulk from a six-dimensional
rotating black hole pierced by a 3-brane. We determine the angular eigenvalues
in the presence of finite brane tension by using the continued fraction method.
The radial equation is integrated numerically, giving the absorption
probability (graybody factor) in a wider frequency range than in the
preexisting literature. We then compute the power and angular momentum emission
spectra for different values of the rotation parameter and brane tension, and
compare their relative behavior in detail. As is expected from the earlier
result for a nonrotating black hole, the finite brane tension suppresses the
emission rates. As the rotation parameter increases, the power spectra are
reduced at low frequencies due to the smaller Hawking temperature and are
enhanced at high frequencies due to superradiance. The angular momentum spectra
are enhanced over the whole frequency range as the rotation parameter
increases. The spectra and the amounts of energy and angular momentum radiated
away into the bulk are thus determined by the interplay of these effects.Comment: 10 pages, 7 figures; v2: references added; v3: Figs. 4, 5, 6
corrected. Numerical results changed; v4: references added, minor
clarification, accepted for publication in Physical Review
Field localization on a brane intersection in anti-de Sitter spacetime
We discuss the localization of scalar, fermion, and gauge field zero modes on
a brane that resides at the intersection of two branes in
six-dimensional anti-de Sitter space. This set-up has been introduced in the
context of brane world models and, higher-dimensional versions of it, in string
theory. In both six- and ten-dimensional cases, it has been shown that
four-dimensional gravity can be reproduced at the intersection, due to the
existence of a massless, localized graviton zero-mode. However, realistic
scenarios require also the Standard Model to be localized on the brane. In
this paper, we discuss under which conditions a higher-dimensional field
theory, propagating on the above geometry, can have a zero-mode sector
localized at the intersection and find that zero modes can be localized only if
masses and couplings to the background curvature satisfy certain relations. We
also consider the case when other 4-branes cut the bulk at some distance from
the intersection and argue that, in the probe brane approximation, there is no
significant effect on the localization properties at the brane. The case of
bulk fermions is particularly interesting, since the properties of the geometry
allow localization of chiral modes independently.Comment: 13 pages, 3 figures, the version to be published in PR
Cold collisions of heavy molecules with alkali-metal atoms in a magnetic field: Ab initio analysis and prospects for sympathetic cooling of SrOH by Li(S)
We use accurate ab initio and quantum scattering calculations to explore the
prospects for sympathetic cooling of the heavy molecular radical
SrOH() by ultracold Li atoms in a magnetic trap. A two-dimensional
potential energy surface (PES) for the triplet electronic state of Li-SrOH is
calculated ab initio using the partially spin-restricted coupled cluster method
with single, double and perturbative triple excitations and a large
correlation-consistent basis set. The highly anisotropic PES has a deep global
minimum in the skewed Li-HOSr geometry with cm and saddle
points in collinear configurations. Our quantum scattering calculations predict
low spin relaxation rates in fully spin-polarized Li+SrOH collisions with the
ratios of elastic to inelastic collision rates well in excess of 100 over a
wide range of magnetic fields (1-1000 G) and collision energies
(10~K) suggesting favorable prospects for sympathetic cooling of
SrOH molecules with spin-polarized Li atoms in a magnetic trap. We find that
spin relaxation in Li+SrOH collisions occurs via a direct mechanism mediated by
the magnetic dipole-dipole interaction between the electron spins of Li and
SrOH, and that the indirect (spin-rotation) mechanism is strongly suppressed.
The upper limit to the Li+SrOH reaction rate coefficient calculated for the
singlet PES using adiabatic capture theory is found to decrease from ~cm/s to a limiting value of cm/s with
decreasing temperature from 0.1 K to 1 K
Enumeration of bigrassmannian permutations below a permutation in Bruhat order
In theory of Coxeter groups, bigrassmannian elements are well known as
elements which have precisely one left descent and precisely one right descent.
In this article, we prove formulas on enumeration of bigrassmannian
permutations weakly below a permutation in Bruhat order in the symmetric
groups. For the proof, we use equivalent characterizations of bigrassmannian
permutations by Lascoux-Schutzenberger and Reading.Comment: 7 pages
- …