827 research outputs found
Conformal Symmetry for Black Holes in Four Dimensions
We show that the asymptotic boundary conditions of general asymptotically
flat black holes in four dimensions can be modified such that a conformal
symmetry emerges. The black holes with the asymptotic geometry removed in this
manner satisfy the equations of motion of minimal supergravity in five
dimensions. We develop evidence that a two dimensional CFT dual of general
black holes in four dimensions account for their black hole entropy.Comment: 24 pages, minor correction
Brane-world Kaluza-Klein reductions and Branes on the Brane
We present a systematic study of a new type of consistent ``Brane-world
Kaluza-Klein Reduction,'' which describe fully non-linear deformations of
co-dimension one objects that arise as solutions of a large class of gauged
supergravity theories in diverse dimensions, and whose world-volume theories
are described by ungauged supergravities with one half of the original
supersymmetry. In addition, we provide oxidations of these Ansatze which are in
general related to sphere compactified higher dimensional string theory or
M-theory. Within each class we also provide explicit solutions of brane
configurations localised on the world-brane. We show that at the Cauchy horizon
(in the transverse dimension of the consistently Kaluza-Klein reduced
world-brane) there is a curvature singularity for any configuration with a
non-null Riemann curvature or a non-vanishing Ricci scalar that lives in the
world-brane. Since the massive Kaluza-Klein modes can be consistently
decoupled, they cannot participate in regulating these singularities.Comment: latex, 30 page
Conformal Symmetry for General Black Holes
We show that the warp factor of a generic asymptotically flat black hole in
five dimensions can be adjusted such that a conformal symmetry emerges. The
construction preserves all near horizon properties of the black holes, such as
the thermodynamic potentials and the entropy. We interpret the geometry with
modified asymptotic behavior as the "bare" black hole, with the ambient flat
space removed. Our warp factor subtraction generalizes hidden conformal
symmetry and applies whether or not rotation is significant. We also find a
relation to standard AdS/CFT correspondence by embedding the black holes in six
dimensions. The asymptotic conformal symmetry guarantees a dual CFT description
of the general rotating black holes.Comment: 26 page
Phenomenology of A Three-Family Standard-like String Model
We discuss the phenomenology of a three-family supersymmetric Standard-like
Model derived from the orientifold construction, in which the ordinary chiral
states are localized at the intersection of branes at angles. In addition to
the Standard Model group, there are two additional U(1)' symmetries, one of
which has family non-universal and therefore flavor changing couplings, and a
quasi-hidden non-abelian sector which becomes strongly coupled above the
electroweak scale. The perturbative spectrum contains a fourth family of exotic
(SU(2)- singlet) quarks and leptons, in which, however, the left-chiral states
have unphysical electric charges. It is argued that these decouple from the low
energy spectrum due to hidden sector charge confinement, and that anomaly
matching requires the physical left-chiral states to be composites. The model
has multiple Higgs doublets and additional exotic states. The moduli-dependent
predictions for the gauge couplings are discussed. The strong coupling agrees
with experiment for reasonable moduli, but the electroweak couplings are too
small.Comment: 22 pages, 4 figure
Microstates of Four-Dimensional Rotating Black Holes from Near-Horizon Geometry
We show that a class of four-dimensional rotating black holes allow
five-dimensional embeddings as black rotating strings. Their near-horizon
geometry factorizes locally as a product of the three-dimensional anti-deSitter
space-time and a two-dimensional sphere (AdS_3 x S^2), with angular momentum
encoded in the global space-time structure. Following the observation that the
isometries on the AdS_3 space induce a two-dimensional (super)conformal field
theory on the boundary, we reproduce the microscopic entropy with the correct
dependence on the black hole angular momentum.Comment: 11 pages, revte
Bottonium mass - evaluation using renormalon cancellation
We present a method of calculating the bottonium mass M[Upsilon(1S)] = [2 mb
+ E(b barb)]. The binding energy is separated into the soft and ultrasoft
components E(b barb)=[E(s)+E(us)] by requiring the reproduction of the correct
residue parameter value of the renormalon singularity for the renormalon
cancellation in the sum [2 mb + E(s)]. The Borel resummation is then performed
separately for (2 mb) and E(s), using the infrared safe MSbar mass [bar mb] as
input. E(us) is estimated. Comparing the result with the measured value of
M[Upsilon(1S)], the extracted value of the quark mass is [bar mb](mu=[bar mb])
= 4.241 +- 0.068 GeV (for the central value alphas(MZ)=0.1180). This value of
[bar mb] is close to the earlier values obtained from the QCD spectral sum
rules, but lower than from pQCD evaluations without the renormalon structure
for heavy quarkonia.Comment: 4 pages, uses espcrc2.sty, presented at QCD0
A K-theory Anomaly Free Supersymmetric Flipped SU(5) Model from Intersecting Branes
We construct an N=1 supersymmetric three-family flipped SU(5) model from type
IIA orientifolds on with D6-branes intersecting at
general angles. The model is constrained by the requirement that Ramond-Ramond
tadpoles cancel, the supersymmetry conditions, and that the gauge boson coupled
to the factor does not get a string-scale mass via a generalised
Green-Schwarz mechanism. The model is further constrained by requiring
cancellation of K-theory charges. The spectrum contains a complete grand
unified and electroweak Higgs sector, however the latter in a non-minimal
number of copies. In addition, it contains extra matter both in bi-fundamental
and vector-like representations as well as two copies of matter in the
symmetric representation of SU(5).Comment: 17 Pages, LaTe
General Rotating Black Holes in String Theory: Greybody Factors and Event Horizons
We derive the wave equation for a minimally coupled scalar field in the
background of a general rotating five-dimensional black hole. It is written in
a form that involves two types of thermodynamic variables, defined at the inner
and outer event horizon, respectively. We model the microscopic structure as an
effective string theory, with the thermodynamic properties of the left and
right moving excitations related to those of the horizons. Previously known
solutions to the wave equation are generalized to the rotating case, and their
regime of validity is sharpened. We calculate the greybody factors and
interpret the resulting Hawking emission spectrum microscopically in several
limits. We find a U-duality invariant expression for the effective string
length that does not assume a hierarchy between the charges. It accounts for
the universal low-energy absorption cross-section in the general non-extremal
case.Comment: 33 pages, latex; minor typos corrected; version to appear in PR
Dynamical Supersymmetry Breaking in Standard-like Models with Intersecting D6-branes
We address dynamical supersymmetry breaking within a N=1 supersymmetric
Standard-like Model based on a Z_2 x Z_2 Type IIA orientifold with intersecting
D6-branes. The model possesses an additional, confining gauge sector with the
USp(2)_A x USp(2)_B x USp(4) gauge group, where the gaugino condensation
mechanism allows for the breaking of supersymmetry and stabilizes moduli. We
derive the leading contribution to the non-perturbative effective
superpotential and determine numerically the minima of the supergravity
potential. These minima break supersymmetry and fix two undetermined moduli,
which in turn completely specify the gauge couplings at the string scale. For
this specific construction the minima have a negative cosmological constant. We
expect that for other supersymmetric Standard-like models with intersecting
D6-branes, which also possess confining gauge sectors, the supersymmetry
breaking mechanism would have qualitatively similar features.Comment: 19 pages, 1 figur
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