4,701 research outputs found
SUSY-breaking Soft Terms in a MSSM Magnetized D7-brane Model
We compute the SUSY-breaking soft terms in a magnetized D7-brane model with
MSSM-like spectrum, under the general assumption of non-vanishing auxiliary
fields of the dilaton and Kahler moduli. As a particular scenario we discuss
SUSY breaking triggered by ISD or IASD 3-form fluxes.Comment: Latex, 27 pages, v2: added reference
Robustness of a high-resolution central scheme for hydrodynamic simulations in full general relativity
A recent paper by Lucas-Serrano et al. indicates that a high-resolution
central (HRC) scheme is robust enough to yield accurate hydrodynamical
simulations of special relativistic flows in the presence of ultrarelativistic
speeds and strong shock waves. In this paper we apply this scheme in full
general relativity (involving {\it dynamical} spacetimes), and assess its
suitability by performing test simulations for oscillations of rapidly rotating
neutron stars and merger of binary neutron stars. It is demonstrated that this
HRC scheme can yield results as accurate as those by the so-called
high-resolution shock-capturing (HRSC) schemes based upon Riemann solvers.
Furthermore, the adopted HRC scheme has increased computational efficiency as
it avoids the costly solution of Riemann problems and has practical advantages
in the modeling of neutron star spacetimes. Namely, it allows simulations with
stiff equations of state by successfully dealing with very low-density
unphysical atmospheres. These facts not only suggest that such a HRC scheme may
be a desirable tool for hydrodynamical simulations in general relativity, but
also open the possibility to perform accurate magnetohydrodynamical simulations
in curved dynamic spacetimes.Comment: 4 pages, to be published in Phys. Rev. D (brief report
D=6, N=1 String Vacua and Duality
We review the structure string vacua with emphasis on the
different connections due to T-dualities and S-dualities. The topics discussed
include: Anomaly cancellation; K3 and orbifold heterotic
compactifications; T-dualities between and
heterotic vacua; non-perturbative heterotic vacua and small instantons; N=2
Type-II/Heterotic duality in D=4 ; F-theory/heterotic duality in D=6; and
heterotic/heterotic duality in six and four dimensions.Comment: 52 pages, plain Latex. To appear in the proceedings of the APCTP
Winter School on Duality, Mt. Sorak (Korea), February 199
Higgsino mass matrix ansatz for MSSM
An ansatz, Det. for the Higgsino mass matrix in string
orbifold trinification is suggested toward the minimal supersymmetric standard
model(MSSM). Small instanton solutions effective around the GUT scale can
fulfil this condition. An argument that the couplings contain a moduli field is
given for a dynamical realization of this Higgsino mass matrix ansatz.Comment: 15 pages of LaTeX fil
Gauge Coupling Unification in Superstring Derived Standard--like Models
I discuss gauge coupling unification in a class of superstring standard--like
models, which are derived in the free fermionic formulation. Recent
calculations indicate that the superstring unification scale is at
while the minimal supersymmetric standard model is consistent
with LEP data if the unification scale is at . A generic feature
of the superstring standard--like models is the appearance of extra color
triplets , and electroweak doublets , in
vector--like representations, beyond the minimal supersymmetric standard model.
I show that gauge coupling unification at in the superstring
standard--like models can be consistent with LEP data. I present an explicit
standard--like model that can realize superstring gauge coupling unification.Comment: WIS--92/17/FEB--PH, 12 page
Numerical evolution of matter in dynamical axisymmetric black hole spacetimes. I. Methods and tests
We have developed a numerical code to study the evolution of self-gravitating
matter in dynamic black hole axisymmetric spacetimes in general relativity. The
matter fields are evolved with a high-resolution shock-capturing scheme that
uses the characteristic information of the general relativistic hydrodynamic
equations to build up a linearized Riemann solver. The spacetime is evolved
with an axisymmetric ADM code designed to evolve a wormhole in full general
relativity. We discuss the numerical and algorithmic issues related to the
effective coupling of the hydrodynamical and spacetime pieces of the code, as
well as the numerical methods and gauge conditions we use to evolve such
spacetimes. The code has been put through a series of tests that verify that it
functions correctly. Particularly, we develop and describe a new set of testbed
calculations and techniques designed to handle dynamically sliced,
self-gravitating matter flows on black holes, and subject the code to these
tests. We make some studies of the spherical and axisymmetric accretion onto a
dynamic black hole, the fully dynamical evolution of imploding shells of dust
with a black hole, the evolution of matter in rotating spacetimes, the
gravitational radiation induced by the presence of the matter fields and the
behavior of apparent horizons through the evolution.Comment: 42 pages, 20 figures, submitted to Phys Rev
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