674 research outputs found
Relativistic D-brane Scattering is Extremely Inelastic
We study the effects of quantum production of open strings on the
relativistic scattering of D-branes. We find strong corrections to the brane
trajectory from copious production of highly-excited open strings, whose
typical oscillator level is proportional to the square of the rapidity. In the
corrected trajectory, the branes rapidly coincide and remain trapped in a
configuration with enhanced symmetry. This is a purely stringy effect which
makes relativistic brane collisions exceptionally inelastic. We trace this
effect to velocity-dependent corrections to the open-string mass, which render
open strings between relativistic D-branes surprisingly light. We observe that
pair-creation of open strings could play an important role in cosmological
scenarios in which branes approach each other at very high speeds.Comment: 30 pages; added references and a comment about velocity-dependent
masse
Black Hole Cross Section at the Large Hadron Collider
Black hole production at the Large Hadron Collider (LHC) was first discussed
in 1999. Since then, much work has been performed in predicting the black hole
cross section. In light of the start up of the LHC, it is now timely to review
the state of these calculations. We review the uncertainties in estimating the
black hole cross section in higher dimensions. One would like to make this
estimate as precise as possible since the predicted values, or lower limits,
obtain for the fundamental Planck scale and number of extra dimensions from
experiments will depend directly on the accuracy of the cross section. Based on
the current knowledge of the cross section, we give a range of lower limits on
the fundamental Planck scale that could be obtained at LHC energies.Comment: 28 pages, 9 figures, LaTeX; added references, corrected typos,
expanded discussio
Flux Discharge Cascades in Various Dimensions
We study the dynamics of electric flux discharge by charged particle pair or
spherical string or membrane production in various dimensions. When electric
flux wraps at least one compact cycle, we find that a single "pair" production
event can initiate a cascading decay in real time that "shorts out" the flux
and discharges many units of it. This process arises from local dynamics in the
compact space, and so is invisible in the dimensionally-reduced truncation. It
occurs in theories as simple as the Schwinger model on a circle, and has
implications for any theory with compact dimensions and electric flux,
including string theories and the string landscape.Comment: 19+8 pages, 3 figures, 3 appendice
Transplanckian Collisions at the LHC and Beyond
Elastic collisions in the transplanckian region, where the center-of-mass
energy is much larger than the fundamental gravity mass scale, can be described
by linearized general relativity and known quantum-mechanical effects as long
as the momentum transfer of the process is sufficiently small. For larger
momentum transfer, non-linear gravitational effects become important and,
although a computation is lacking, black-hole formation is expected to dominate
the dynamics. We discuss how elastic transplanckian collisions can be used at
high-energy colliders to study, in a quantitative and model-independent way,
theories in which gravity propagates in flat extra dimensions. At LHC energies,
however, incalculable quantum-gravity contributions may significantly affect
the experimental signal.Comment: 45 pages, 9 figures. v2: added refs and expanded discussion of
fixed-angle string scatterin
A Gravity Dual of RHIC Collisions
In the context of the AdS/CFT correspondence we discuss the gravity dual of a
heavy-ion-like collision in a variant of SYM. We provide a gravity
dual picture of the entire process using a model where the scattering process
creates initially a holographic shower in bulk AdS. The subsequent
gravitational fall leads to a moving black hole that is gravity dual to the
expanding and cooling heavy-ion fireball. The front of the fireball cools at
the rate of , while the core cools as from a
cosmological-like argument. The cooling is faster than Bjorken cooling. The
fireball freezes when the dual black hole background is replaced by a confining
background through the Hawking-Page transition.Comment: 25 pages, 8 figures, Added references, Falling picture elucidate
D-brane scattering and annihilation
We study the dynamics of parallel brane-brane and brane-antibrane scattering
in string theory in flat spacetime, focusing on the pair production of open
strings that stretch between the branes. We are particularly interested in the
case of scattering at small impact parameter , where there is a
tachyon in the spectrum when a brane and an antibrane approach within a string
length. Our conclusion is that despite the tachyon, branes and antibranes can
pass through each other with only a very small probability of annihilating, so
long as is small and the relative velocity is neither too small nor
too close to 1. Our analysis is relevant also to the case of charged open
string production in world-volume electric fields, and we make use of this
T-dual scenario in our analysis. We briefly discuss the application of our
results to a stringy model of inflation involving moving branes.Comment: 25+7 pages, 5 figure
Black Hole Production at the Large Hadron Collider
Black hole production at the Large Hadron Collider (LHC) is an interesting
consequence of TeV-scale gravity models. The predicted values, or lower limits,
for the fundamental Planck scale and number of extra dimensions will depend
directly on the accuracy of the black hole production cross-section. We give a
range of lower limits on the fundamental Planck scale that could be obtained at
LHC energies. In addition, we examine the effects of parton electric charge on
black hole production using the trapped-surface approach of general relativity.
Accounting for electric charge of the partons could reduce the black hole
cross-section by one to four orders of magnitude at the LHC.Comment: CTP Symposium on Supersymmetry at LHC: Theoretical and Experimental
Perspectives at the British University in Egypt 11-14 March 200
Unwinding Inflation
Higher-form flux that extends in all 3+1 dimensions of spacetime is a source
of positive vacuum energy that can drive meta-stable eternal inflation. If the
flux also threads compact extra dimensions, the spontaneous nucleation of a
bubble of brane charged under the flux can trigger a classical cascade that
steadily unwinds many units of flux, gradually decreasing the vacuum energy
while inflating the bubble, until the cascade ends in the self-annihilation of
the brane into radiation. With an initial number of flux quanta Q_{0} \simgeq
N, this can result in N efolds of inflationary expansion while producing a
scale-invariant spectrum of adiabatic density perturbations with amplitude and
tilt consistent with observation. The power spectrum has an oscillatory
component that does not decay away during inflation, relatively large tensor
power, and interesting non-Gaussianities. Unwinding inflation fits naturally
into the string landscape, and our preliminary conclusion is that consistency
with observation can be attained without fine-tuning the string parameters. The
initial conditions necessary for the unwinding phase are produced automatically
by bubble formation, so long as the critical radius of the bubble is smaller
than at least one of the compact dimensions threaded by flux.Comment: 29+15 pages, 10 figures, published versio
Strongly Correlated Quantum Fluids: Ultracold Quantum Gases, Quantum Chromodynamic Plasmas, and Holographic Duality
Strongly correlated quantum fluids are phases of matter that are
intrinsically quantum mechanical, and that do not have a simple description in
terms of weakly interacting quasi-particles. Two systems that have recently
attracted a great deal of interest are the quark-gluon plasma, a plasma of
strongly interacting quarks and gluons produced in relativistic heavy ion
collisions, and ultracold atomic Fermi gases, very dilute clouds of atomic
gases confined in optical or magnetic traps. These systems differ by more than
20 orders of magnitude in temperature, but they were shown to exhibit very
similar hydrodynamic flow. In particular, both fluids exhibit a robustly low
shear viscosity to entropy density ratio which is characteristic of quantum
fluids described by holographic duality, a mapping from strongly correlated
quantum field theories to weakly curved higher dimensional classical gravity.
This review explores the connection between these fields, and it also serves as
an introduction to the Focus Issue of New Journal of Physics on Strongly
Correlated Quantum Fluids: from Ultracold Quantum Gases to QCD Plasmas. The
presentation is made accessible to the general physics reader and includes
discussions of the latest research developments in all three areas.Comment: 138 pages, 25 figures, review associated with New Journal of Physics
special issue "Focus on Strongly Correlated Quantum Fluids: from Ultracold
Quantum Gases to QCD Plasmas"
(http://iopscience.iop.org/1367-2630/focus/Focus%20on%20Strongly%20Correlated%20Quantum%20Fluids%20-%20from%20Ultracold%20Quantum%20Gases%20to%20QCD%20Plasmas
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