43 research outputs found
Deep Inelastic Scattering and Gauge/String Duality
We study deep inelastic scattering in gauge theories which have dual string
descriptions. As a function of we find a transition. For small , the
dominant operators in the OPE are the usual ones, of approximate twist two,
corresponding to scattering from weakly interacting partons. For large ,
double-trace operators dominate, corresponding to scattering from entire
hadrons (either the original `valence' hadron or part of a hadron cloud.) At
large we calculate the structure functions. As a function of Bjorken
there are three regimes: of order one, where the scattering produces only
supergravity states; small, where excited strings are produced; and,
exponentially small, where the excited strings are comparable in size to the
AdS space. The last regime requires in principle a full string calculation in
curved spacetime, but the effect of string growth can be simply obtained from
the world-sheet renormalization group.Comment: 52 pages, 10 figure
Particle motion in the field of a five-dimensional charged black hole
In this paper, we have investigated the geodesics of neutral particles near a
five-dimensional charged black hole using a comparative approach. The effective
potential method is used to determine the location of the horizons and to study
radial and circular trajectories. This also helps us to analyze the stability
of radial and circular orbits. The radius of the innermost stable circular
orbits have also been determined. Contrary to the case of massive particles for
which, the circular orbits may have up to eight possible values of specific
radius, we find that the photons will only have two distinct values for the
specific radii of circular trajectories. Finally we have used the dynamical
systems analysis to determine the critical points and the nature of the
trajectories for the timelike and null geodesics.Comment: 15 pages, accepted for publication in Astrophysics and Space Scienc
How can the Odderon be detected at RHIC and LHC
The Odderon remains an elusive object, 33 years after its invention. The
Odderon is now a fundamental object in QCD and CGC and it has to be found
experimentally if QCD and CGC are right. In the present paper, we show how to
find it at RHIC and LHC. The most spectacular signature of the Odderon is the
predicted difference between the differential cross-sections for proton-proton
and antiproton-proton at high s and moderate t. The experiment can be done by
using the STAR detector at RHIC and by combining these future data with the
already present UA4/2 data. The Odderon could also be found by ATLAS
exeperiment at LHC by performing a high-precision measurement of the real part
of the hadron elastic scattering amplitude at small t.Comment: 14 pages, 16 figures, two typographical errors corrected and
acknowledgments adde
Disappearing Dark Matter in Brane World Cosmology: New Limits on Noncompact Extra Dimensions
We explore cosmological implications of dark matter as massive particles
trapped on a brane embedded in a Randall-Sundrum noncompact higher dimension
space. It is an unavoidable consequence of this cosmology that massive
particles are metastable and can disappear into the bulk dimension. Here, we
show that a massive dark matter particle (e.g. the lightest supersymmetric
particle) is likely to have the shortest lifetime for disappearing into the
bulk. We examine cosmological constraints on this new paradigm and show that
disappearing dark matter is consistent (at the 95% confidence level) with all
cosmological constraints, i.e. present observations of Type Ia supernovae at
the highest redshift, trends in the mass-to-light ratios of galaxy clusters
with redshift, the fraction of X-ray emitting gas in rich clusters, and the
spectrum of power fluctuations in the cosmic microwave background. A best concordance region is identified corresponding to a mean lifetime for
dark matter disappearance of Gyr. The implication
of these results for brane-world physics is discussed.Comment: 7 pages, 7 figures, new cosmological constraints added, accepted for
publication in PR
Quasinormal modes of Schwarzschild black holes in four and higher dimensions
We make a thorough investigation of the asymptotic quasinormal modes of the
four and five-dimensional Schwarzschild black hole for scalar, electromagnetic
and gravitational perturbations. Our numerical results give full support to all
the analytical predictions by Motl and Neitzke, for the leading term. We also
compute the first order corrections analytically, by extending to higher
dimensions, previous work of Musiri and Siopsis, and find excellent agreement
with the numerical results. For generic spacetime dimension number D the
first-order corrections go as . This means that
there is a more rapid convergence to the asymptotic value for the five
dimensional case than for the four dimensional case, as we also show
numerically.Comment: 12 pages, 5 figures, RevTeX4. v2. Typos corrected, references adde
Understanding the Non-Gaussian Nature of Linear Reactive Solute Transport in 1D and 2D
Entropic force approach to noncommutative Schwarzschild black holes signals a failure of current physical ideas
Recently, a new perspective of gravitational-thermodynamic duality as an
entropic force arising from alterations in the information connected to the
positions of material bodies is found. In this paper, we generalize some
aspects of this model in the presence of noncommutative Schwarzschild black
hole by applying the method of coordinate coherent states describing smeared
structures. We implement two different distributions: (a) Gaussian and (b)
Lorentzian. Both mass distributions prepare the similar quantitative aspects
for the entropic force. Our study shows, the entropic force on the smallest
fundamental unit of a holographic screen with radius vanishes. As a
result, black hole remnants are unconditionally inert even gravitational
interactions do not exist therein. So, a distinction between gravitational and
inertial mass in the size of black hole remnant is observed, i.e. the failure
of the principle of equivalence. In addition, if one considers the screen
radius to be less than the radius of the smallest holographic surface at the
Planckian regime, then one encounters some unusual dynamical features leading
to gravitational repulsive force and negative energy. On the other hand, the
significant distinction between the two distributions is conceived to occur
around , and that is worth of mentioning: at this regime either our
analysis is not the proper one, or non-extensive statistics should be employed.Comment: 15 pages, 2 figures, new references added, minor revision, Title
changed, to appear in EPJ Plu
The Dynamics of Brane-World Cosmological Models
Brane-world cosmology is motivated by recent developments in string/M-theory
and offers a new perspective on the hierarchy problem. In the brane-world
scenario, our Universe is a four-dimensional subspace or {\em brane} embedded
in a higher-dimensional {\em bulk} spacetime. Ordinary matter fields are
confined to the brane while the gravitational field can also propagate in the
bulk, leading to modifications of Einstein's theory of general relativity at
high energies. In particular, the Randall-Sundrum-type models are
self-consistent and simple and allow for an investigation of the essential
non-linear gravitational dynamics. The governing field equations induced on the
brane differ from the general relativistic equations in that there are nonlocal
effects from the free gravitational field in the bulk, transmitted via the
projection of the bulk Weyl tensor, and the local quadratic energy-momentum
corrections, which are significant in the high-energy regime close to the
initial singularity. In this review we discuss the asymptotic dynamical
evolution of spatially homogeneous brane-world cosmological models containing
both a perfect fluid and a scalar field close to the initial singularity. Using
dynamical systems techniques it is found that, for models with a physically
relevant equation of state, an isotropic singularity is a past-attractor in all
orthogonal spatially homogeneous models (including Bianchi type IX models). In
addition, we describe the dynamics in a class of inhomogeneous brane-world
models, and show that these models also have an isotropic initial singularity.
These results provide support for the conjecture that typically the initial
cosmological singularity is isotropic in brane-world cosmology.Comment: Einstein Centennial Review Article: to appear in CJ
Search for TeV-scale gravity signatures in high-mass final states with leptons and jets with the ATLAS detector at sqrt [ s ] = 13TeV
A search for physics beyond the Standard Model, in final states with at least one high transverse momentum charged lepton (electron or muon) and two additional high transverse momentum leptons or jets, is performed using 3.2 fb−1 of proton–proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015 at √s = 13 TeV. The upper end of the distribution of the scalar sum of the transverse momenta of leptons and jets is sensitive to the production of high-mass objects. No excess of events beyond Standard Model predictions is observed. Exclusion limits are set for models of microscopic black holes with two to six extra dimensions
Search for black holes and other new phenomena in high-multiplicity final states in proton-proton collisions at root s=13 TeV
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