686 research outputs found
Gauge Coupling Constant Unification With Planck Scale Values Of Moduli
Convergence of the standard model gauge coupling constants to a common value
at around GeV is studied in the context of orbifold theories
where the modular symmetry groups for and moduli are broken to
subgroups of . The values of the moduli required for this
unification of coupling constants are studied for this case and also for the
case where string unification is accompanied by unification to a gauge group
larger then Comment: Tex, 15 pages, minor typos corrected and some references adde
Modular Symmetries of Threshold Corrections for Abelian Orbifolds with Discrete Wilson Lines
The modular symmetries of string loop threshold corrections for gauge
coupling constants are studied in the presence of discrete Wilson lines for all
examples of abelian orbifolds, where the point group is realised by the action
of Coxeter elements or generalised Coxeter elements on the root lattices of the
Lie groups.Comment: 36 pages, Late
Background Symmetries In Orbifolds With Discrete Wilson Lines
Target space symmetries are studied for orbifold compactified string theories
containing Wilson line background fields. The symmetries determined are for
those moduli which contribute to the string loop threshold corrections of the
gauge coupling constants. The groups found are subgroups of the modular group
and depend on the choice of discrete Wilson lines and the shape of
the underlying six-dimensional lattice.Comment: 31 pages, QMW--TH--94/0
Duality Symmetries in Orbifold Models
We derive the duality symmetries relevant to moduli dependent gauge coupling
constant threshold corrections, in Coxeter orbifolds. We consider
those orbifolds for which the point group leaves fixed a 2-dimensional
sublattice , of the six dimensional torus lattice , where
cannot be decomposed as Comment: 13 pages, QMW--TH--93/21, SUSX--TH--93/1
Anisotropic Solutions For Orbifold Moduli From Duality Invariant Gaugino Condensates
The values of the and moduli are studied for those
Coxeter orbifolds with the property that some of the twisted sectors have fixed
planes for which the six-torus can not be decomposed into a direct
sum with the fixed plane lying in .
Such moduli in general transform under a subgroup of the modular group
The moduli are determined by minimizing the effective potential
derived from a duality invariant gaugino condensate.Comment: QMW--TH--94/11, SUSX--TH--94/11, 16 page
Modular Symmetries in Orbifold Compactified String Theories with Wilson lines
Target space modular symmetries relevant to string loop threshold corrections
are studied for orbifold compactified string theories containing Wilson
line background fields.Comment: SUSX--TH--93/17, QMW--TH--93/31, 12 page
Modular Symmetries, Threshold Corrections And Moduli For Orbifolds
Coxeter orbifolds are constructed with the
property that some twisted sectors have fixed planes for which the six-torus
can not be decomposed into a direct sum with the
fixed plane lying in . The string loop threshold corrections to the
gauge coupling constants are derived, and display symmetry groups for the
and moduli that are subgroups of the full modular group . The
effective potential for duality invariant gaugino condensate in the presence of
hidden sector matter is constructed and minimized for the values of the moduli.
The effect of Wilson lines on the modular symmetries is also studied.Comment: QMW--TH--94/18, 12 page
Inclination-Independent Galaxy Classification
We present a new method to classify galaxies from large surveys like the
Sloan Digital Sky Survey using inclination-corrected concentration,
inclination-corrected location on the color-magnitude diagram, and apparent
axis ratio. Explicitly accounting for inclination tightens the distribution of
each of these parameters and enables simple boundaries to be drawn that
delineate three different galaxy populations: Early-type galaxies, which are
red, highly concentrated, and round; Late-type galaxies, which are blue, have
low concentrations, and are disk dominated; and Intermediate-type galaxies,
which are red, have intermediate concentrations, and have disks. We have
validated our method by comparing to visual classifications of high-quality
imaging data from the Millennium Galaxy Catalogue. The inclination correction
is crucial to unveiling the previously unrecognized Intermediate class.
Intermediate-type galaxies, roughly corresponding to lenticulars and early
spirals, lie on the red sequence. The red sequence is therefore composed of two
distinct morphological types, suggesting that there are two distinct mechanisms
for transiting to the red sequence. We propose that Intermediate-type galaxies
are those that have lost their cold gas via strangulation, while Early-type
galaxies are those that have experienced a major merger that either consumed
their cold gas, or whose merger progenitors were already devoid of cold gas
(the ``dry merger'' scenario).Comment: Accepted for publication in ApJ. 7 pages in emulateap
The impact of baryons on the direct detection of dark matter
The spatial and velocity distributions of dark matter particles in the Milky
Way Halo affect the signals expected to be observed in searches for dark
matter. Results from direct detection experiments are often analyzed assuming a
simple isothermal distribution of dark matter, the Standard Halo Model (SHM).
Yet there has been skepticism regarding the validity of this simple model due
to the complicated gravitational collapse and merger history of actual
galaxies. In this paper we compare the SHM to the results of cosmological
hydrodynamical simulations of galaxy formation to investigate whether or not
the SHM is a good representation of the true WIMP distribution in the analysis
of direct detection data. We examine two Milky Way-like galaxies from the
MaGICC cosmological simulations (a) with dark matter only and (b) with baryonic
physics included. The inclusion of baryons drives the shape of the DM halo to
become more spherical and makes the velocity distribution of dark matter
particles less anisotropic especially at large heliocentric velocities, thereby
making the SHM a better fit. We also note that we do not find a significant
disk-like rotating dark matter component in either of the two galaxy halos with
baryons that we examine, suggesting that dark disks are not a generic
prediction of cosmological hydrodynamical simulations. We conclude that in the
Solar neighborhood, the SHM is in fact a good approximation to the true dark
matter distribution in these cosmological simulations (with baryons) which are
reasonable representations of the Milky Way, and hence can also be used for the
purpose of dark matter direct detection calculations.Comment: Minor changes to match JCAP version. 21 pages, 9 figure
Superconductors with two critical temperatures
We propose a simple model for superconductors endowed with two critical
temperatures, corresponding to two second-order phase transitions, in the
framework of the Ginzburg-Landau mean-field theory. For very large Cooper pair
self-interaction, in addition to the standard condensation occurring in the
Ginzburg-Landau theory, we find another phase transition at a lower temperature
with a maximum difference of 15% between the two critical temperatures.Comment: revtex, 3 pages, one eps figur
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