111 research outputs found
Supersymmetric Dissipative Quantum Mechanics from Superstrings
Following the approach of Callan and Thorlacius applied to the superstring,
we derive a supersymmetric extension of the non-local dissipative action of
Caldeira and Leggett. The dissipative term turns out to be invariant under a
group of superconformal transformations. When added to the usual kinetic term,
it provides an example of supersymmetric dissipative quantum mechanics. As a
by-product of our analysis, an intriguing connection to the homeotic/hybrid
fermion model, proposed for CPT violation in neutrinos, appears.Comment: Latex, 16 page
Chiral 4d string vacua with D-branes and NSNS and RR fluxes
We discuss type IIB orientifolds with D-branes, and NSNS and RR field
strength fluxes. The D-brane sectors lead to open string spectra with
non-abelian gauge symmetry and charged chiral fermions. The closed string field
strengths generate a scalar potential stabilizing most moduli. We describe the
construction of N=1 supersymmetric models in the context of orientifolds of IIB
theory on T^6/Z_2 x Z_2, containing D9-branes with world-volume magnetic
fluxes, and illustrate model building possibilities with several explicit
examples. We comment on a T-dual picture with D8-branes on non-Calabi-Yau
half-flat geometries, and discuss some of the topological properties of such
configurations. We also explore the construction of models with fluxes and with
D3-branes at singularities and present a non-supersymmetric 3-family SU(5)
model.Comment: latex, 49 pages, 2 figure
Flux-induced SUSY-breaking soft terms on D7-D3 brane systems
We study the effect of RR and NSNS 3-form fluxes on the effective action of
the worldvolume fields of Type IIB D7/D3-brane configurations. The D7-branes
wrap 4-cycles on a local Calabi-Yau geometry. This is an extension of previous
work on hep-th/0311241, where a similar analysis was applied to the case of
D3-branes. Our present analysis is based on the D7- and D3-brane
Dirac-Born-Infeld and Chern-Simons actions, and makes full use of the
R-symmetries of the system, which allow us to compute explicitly results for
the fields lying at the D3-D7 intersections. A number of interesting new
properties appear as compared to the simpler case of configurations with only
D3-branes. As a general result one finds that fluxes stabilize some or all of
the D7-brane moduli. We argue that this is important for the problem of
stabilizing Kahler moduli through non-perturbative effects in KKLT-like vacua.
We also show that (0,3) imaginary self-dual fluxes, which lead to
compactifications with zero vacuum energy, give rise to SUSY-breaking soft
terms including gaugino and scalar masses, and trilinear terms. Particular
examples of chiral MSSM-like models of this class of vacua, based on D3-D7
brane systems at orbifold singularities are presented.Comment: 58 pages, no figures; v2: numerical factor in section 7.2 correcte
The causal boundary of wave-type spacetimes
A complete and systematic approach to compute the causal boundary of
wave-type spacetimes is carried out. The case of a 1-dimensional boundary is
specially analyzed and its critical appearance in pp-wave type spacetimes is
emphasized. In particular, the corresponding results obtained in the framework
of the AdS/CFT correspondence for holography on the boundary, are reinterpreted
and very widely generalized. Technically, a recent new definition of causal
boundary is used and stressed. Moreover, a set of mathematical tools is
introduced (analytical functional approach, Sturm-Liouville theory, Fermat-type
arrival time, Busemann-type functions).Comment: 41 pages, 1 table. Included 4 new figures, and some small
modifications. To appear in JHE
Urinary retention and the role of indwelling catheterization following total knee arthroplasty
Double-slit interference pattern from single-slit screen and its gravitational analogues
The double slit experiment (DSE) is known as an important cornerstone in the
foundations of physical theories such as Quantum Mechanics and Special
Relativity. A large number of different variants of it were designed and
performed over the years. We perform and discuss here a new verion with the
somewhat unexpected results of obtaining interference pattern from single-slit
screen. This outcome, which shows that the routes of the photons through the
array were changed, leads one to discuss it, using the equivalence principle,
in terms of geodesics mechanics. We show using either the Brill's version of
the canonical formulation of general relativity or the linearized version of it
that one may find corresponding and analogous situations in the framework of
general relativity.Comment: 51 pages, 12 Figures five of them contain two subfigures and thus the
number of figures is 17, 1 Table. Some minor changes introduced, especially,
in the reference
Open Strings in Exactly Solvable Model of Curved Spacetime and PP-Wave Limit
In this paper we study the superstring version of the exactly solvable string
model constructed by Russo and Tseytlin. This model represents superstring
theory in a curved spacetime and can be seen as a generalization of the Melvin
background. We investigate D-branes in this model as probes of the background
geometry by constructing the boundary states. We find that spacetime
singularities in the model become smooth at high energy from the viewpoint of
open string. We show that there always exist bulk (movable) D-branes by the
effect of electric flux. The model also includes Nappi-Witten model as the
Penrose limit and supersymmetry is enhanced in the limit. We examine this
phenomenon in the open string spectrum. We also find the similar enhancement of
supersymmetry can be occurred in several coset models.Comment: Latex, 32 pages, typos corrected, references added, to appear in
JHEP, eq.(2.22) correcte
Product-Group Unification in Type IIB String Thoery
The product-group unification is a model of unified theories, in which
masslessness of the two Higgs doublets and absence of dimension-five proton
decay are guaranteed by a symmetry. It is based on SU(5) x U(N) (N=2,3) gauge
group. It is known that various features of the model are explained naturally,
when it is embedded in a brane world. This article describes an idea of how to
accommodate all the particles of the model in Type IIB brane world. The
GUT-breaking sector is realized by a D3--D7 system, and chiral quarks and
leptons arise from intersection of D7-branes. The D-brane configuration can be
a geometric realization of the non-parallel family structure of quarks and
leptons, an idea proposed to explain the large mixing angles observed in the
neutrino oscillation. The tri-linear interaction of the next-to-minimal
supersymmetric standard model is obtained naturally in some cases.Comment: 33 pages, 5 figure
Anomalous dimensions in gauge theories from rotating strings in
Semi-classical soliton solutions for superstrings in are
used to predict the dimension of gauge theory operators in SU(N) SYM
theory. We discuss the possible origin of scaling violations on the gauge
theory side.Comment: 12 pages, harvmac. References added. [JHEP06(2002) 038
A High Statistics Search for Ultra-High Energy Gamma-Ray Emission from Cygnus X-3 and Hercules X-1
We have carried out a high statistics (2 Billion events) search for
ultra-high energy gamma-ray emission from the X-ray binary sources Cygnus X-3
and Hercules X-1. Using data taken with the CASA-MIA detector over a five year
period (1990-1995), we find no evidence for steady emission from either source
at energies above 115 TeV. The derived upper limits on such emission are more
than two orders of magnitude lower than earlier claimed detections. We also
find no evidence for neutral particle or gamma-ray emission from either source
on time scales of one day and 0.5 hr. For Cygnus X-3, there is no evidence for
emission correlated with the 4.8 hr X-ray periodicity or with the occurrence of
large radio flares. Unless one postulates that these sources were very active
earlier and are now dormant, the limits presented here put into question the
earlier results, and highlight the difficulties that possible future
experiments will have in detecting gamma-ray signals at ultra-high energies.Comment: 26 LaTeX pages, 16 PostScript figures, uses psfig.sty to be published
in Physical Review
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