4,571 research outputs found
LHC String Phenomenology
We argue that it is possible to address the deeper LHC Inverse Problem, to
gain insight into the underlying theory from LHC signatures of new physics. We
propose a technique which may allow us to distinguish among, and favor or
disfavor, various classes of underlying theoretical constructions using
(assumed) new physics signals at the LHC. We think that this can be done with
limited data , and improved with more data. This is because of
two reasons -- a) it is possible in many cases to reliably go from
(semi)realistic microscopic string construction to the space of experimental
observables, say, LHC signatures. b) The patterns of signatures at the LHC are
sensitive to the structure of the underlying theoretical constructions. We
illustrate our approach by analyzing two promising classes of string
compactifications along with six other string-motivated constructions. Even
though these constructions are not complete, they illustrate the point we want
to emphasize. We think that using this technique effectively over time can
eventually help us to meaningfully connect experimental data to microscopic
theory.Comment: 50 Pages, 13 Figures, 3 Tables, v2: minor changes, references adde
How Not to Construct an Asymptotically de Sitter Universe
Observational evidence suggests that our universe is currently evolving
towards an asymptotically de Sitter future. Unfortunately and in spite of much
recent attention, various quantum, holographic and cosmological aspects of de
Sitter space remain quite enigmatic. With such intrigue in mind, this paper
considers the ``construction'' of a toy model that describes an asymptotically
de Sitter universe. More specifically, we add fluid-like matter to an otherwise
purely de Sitter spacetime, formulate the relevant solutions and then discuss
the cosmological and holographic implications. If the objective is to construct
an asymptotically de Sitter universe that is free of singularities and has a
straightforward holographic interpretation, then the results of this analysis
are decidedly negative. Nonetheless, this toy model nicely illustrates the
pitfalls that might be encountered in a more realistic type of construction.Comment: 25 pages, Latex; references and footnotes added (other minor changes
Holography in Three-dimensional Kerr-de Sitter Space with a Gravitational Chern-Simons Term
The holographic description of the three-dimensional Kerr-de Sitter space
with a gravitational Chern-Simons term is studied, in the context of dS/CFT
correspondence. The space has only one (cosmological) event horizon and its
mass and angular momentum are identified from the holographic energy-momentum
tensor at the asymptotic infinity. The thermodynamic entropy of the
cosmological horizon is computed directly from the first law of thermodynamics,
with the usual Hawking temperature, and it is found that the usual
Gibbons-Hawking entropy is modified. It is remarked that, due to the
gravitational Chern-Simons term, (a) the results go beyond analytic
continuation from AdS, (b) the maximum-mass/N-bound conjecture may be violated,
and (c) the three-dimensional cosmology is chiral. A statistical mechanical
computation of the entropy, from a Cardy-like formula for a dual CFT at the
asymptotic boundary, is discussed. Some technical difference in the
Chern-Simons energy-momentum tensor, from literatures is remarked also.Comment: Typos corrected; Accepted in CQ
Time-dependent backgrounds from supergravity with gauged non-compact R-symmetry
We obtain a general class of time-dependent, asymptotically de Sitter
backgrounds which solve the first order bosonic equations that extremize the
action for supergravity with gauged non-compact -symmetry. These backgrounds
correspond only to neutral fields with the correct sign of kinetic energy.
Within N=2 five-dimensional supergravity with vector-superfields we provide
examples of multi-centered charged black holes in asymptotic de Sitter space,
whose spatial part is given by a time-dependent hyper-K\"ahler space. Reducing
these backgrounds to four dimensions yields asymptotically de Sitter
multi-centered charged black hole backgrounds and we show that they are related
to an instanton configuration by a massive T-duality over time. Within N=2
gauged supergravity in four (and five)-dimensions with hyper-multiplets there
could also be neutral cosmological backgrounds that are regular and correspond
to the different de Sitter spaces at early and late times.Comment: 28 pages, Latex; minor changes and add reference
Statistical Mechanics of Three-dimensional Kerr-de Sitter Space
The statistical computation of the (2+1)-dimensional Kerr-de Sitter space in
the context of the {\it classical} Virasoro algebra for an asymptotic isometry
group has been a mystery since first, the degeneracy of the states has the
right value only at the infinite boundary which is casually disconnected from
our universe, second, the analyses were based on the unproven Cardy's formula
for complex central charge and conformal weight. In this paper, I consider the
entropy in Carlip's "would-be gauge" degrees of freedom approach instead. I
find that it agree with the Bekenstein-Hawking entropy but there are no the
above problems. Implications to the dS/CFT are noted.Comment: Added comments about diffeomorphism generators and Wheeler-de Witt
equation; Added references; Accpected in CQ
Comparing Brane Inflation to WMAP
We compare the simplest realistic brane inflationary model to recent
cosmological data, including WMAP 3-year cosmic microwave background (CMB)
results, Sloan Digital Sky Survey luminous red galaxies (SDSS LRG) power
spectrum data and Supernovae Legacy Survey (SNLS) Type 1a supernovae distance
measures. Here, the inflaton is simply the position of a -brane which is
moving towards a -brane sitting at the bottom of a throat (a warped,
deformed conifold) in the flux compactified bulk in Type IIB string theory. The
analysis includes both the usual slow-roll scenario and the Dirac-Born-Infeld
scenario of slow but relativistic rolling. Requiring that the throat is inside
the bulk greatly restricts the allowed parameter space. We discuss possible
scenarios in which large tensor mode and/or non-Gaussianity may emerge. Here,
the properties of a large tensor mode deviate from that in the usual slow-roll
scenario, providing a possible stringy signature. Overall, within the brane
inflationary scenario, the cosmological data is providing information about the
properties of the compactification of the extra dimensions.Comment: 45 pages 11 figure
Renormalization Group Flows from Five-Dimensional Supergravity
The use of gauged supergravity as a tool in studying the
AdS/CFT correspondence for Yang-Mills theory is reviewed. The
supergravity potential implies a non-trivial, supersymmetric IR fixed point,
and the flow to this fixed point is described in terms of a supergravity kink.
The results agree perfectly with earlier, independent field theory results. A
supergravity inspired -function, and corresponding -theorem is discussed
for general flows, and the simplified form for supersymmetric flows is also
given. Flows along the Coulomb branch of the Yang-Mills theory are also
described from the five-dimensional perspective.Comment: 12 pages, 3 figures; Latex, ioplppt.sty, iopl12.sty, epsf.sty.
Contribution to Strings `9
Black Holes as Effective Geometries
Gravitational entropy arises in string theory via coarse graining over an
underlying space of microstates. In this review we would like to address the
question of how the classical black hole geometry itself arises as an effective
or approximate description of a pure state, in a closed string theory, which
semiclassical observers are unable to distinguish from the "naive" geometry. In
cases with enough supersymmetry it has been possible to explicitly construct
these microstates in spacetime, and understand how coarse-graining of
non-singular, horizon-free objects can lead to an effective description as an
extremal black hole. We discuss how these results arise for examples in Type II
string theory on AdS_5 x S^5 and on AdS_3 x S^3 x T^4 that preserve 16 and 8
supercharges respectively. For such a picture of black holes as effective
geometries to extend to cases with finite horizon area the scale of quantum
effects in gravity would have to extend well beyond the vicinity of the
singularities in the effective theory. By studying examples in M-theory on
AdS_3 x S^2 x CY that preserve 4 supersymmetries we show how this can happen.Comment: Review based on lectures of JdB at CERN RTN Winter School and of VB
at PIMS Summer School. 68 pages. Added reference
On Holomorphic Factorization in Asymptotically AdS 3D Gravity
This paper studies aspects of ``holography'' for Euclidean signature pure
gravity on asymptotically AdS 3-manifolds. This theory can be described as
SL(2,C) CS theory. However, not all configurations of CS theory correspond to
asymptotically AdS 3-manifolds. We show that configurations that do have the
metric interpretation are parameterized by the so-called projective structures
on the boundary. The corresponding asymptotic phase space is shown to be the
cotangent bundle over the Schottky space of the boundary. This singles out a
``gravitational'' sector of the SL(2,C) CS theory. It is over this sector that
the path integral has to be taken to obtain the gravity partition function. We
sketch an argument for holomorphic factorization of this partition function.Comment: 32+1 pages, no figures; (v2) one reference added, a statement
regarding priorities modified; (v3) presentational changes, an important sign
mistake correcte
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