4,803 research outputs found
Emergence of the fuzzy horizon through gravitational collapse
For a large enough Schwarzschild black hole, the horizon is a region of space
where gravitational forces are weak; yet it is also a region leading to
numerous puzzles connected to stringy physics. In this work, we analyze the
process of gravitational collapse and black hole formation in the context of
light-cone M theory. We find that, as a shell of matter contracts and is about
to reveal a black hole horizon, it undergoes a thermodynamic phase transition.
This involves the binding of D0 branes into D2's, and the new phase leads to
large membranes of the size of the horizon. These in turn can sustain their
large size through back-reaction and the dielectric Myers effect - realizing
the fuzzball proposal of Mathur and the Matrix black hole of M(atrix) theory.
The physics responsible for this phenomenon lies in strongly coupled 2+1
dimensional non-commutative dynamics. The phenomenon has a universal character
and appears generic.Comment: 24 pages, 4 figures; v2: minor clarifications, citations adde
Probing black holes in non-perturbative gauge theory
We use a 0-brane to probe a ten-dimensional near-extremal black hole with N
units of 0-brane charge. We work directly in the dual strongly-coupled quantum
mechanics, using mean-field methods to describe the black hole background
non-perturbatively. We obtain the distribution of W boson masses, and find a
clear separation between light and heavy degrees of freedom. To localize the
probe we introduce a resolving time and integrate out the heavy modes. After a
non-trivial change of coordinates, the effective potential for the probe agrees
with supergravity expectations. We compute the entropy of the probe, and find
that the stretched horizon of the black hole arises dynamically in the quantum
mechanics, as thermal restoration of unbroken U(N+1) gauge symmetry. Our
analysis of the quantum mechanics predicts a correct relation between the
horizon radius and entropy of a black hole.Comment: 30 pages, LaTeX, 8 eps figures. v2: references added. v3: more
reference
Expression of Interest ICES/KIS-3 : Thema 4: Hoogwaardig Ruimtegebruik Speerpunt 6
Hoofddoel van dit speerpunt is om zowel de Nederlandse overheid als het bedrijfsleven uit te rusten met een operationele kennisinfrastructuur die toegesneden is op de relatie tussen (antropogene en natuurlijke) klimaatverandering en meervoudig ruimtegebrui
Higher Loop Effects in M(atrix) Orbifolds
Scattering of zero branes off the fixed point in , as described by a
super-quantum mechanics with eight supercharges, displays some novel effects
relevant to Matrix theory in non-compact backgrounds. The leading long distance
behaviour of the moduli space metric receives no correction at one loop in
Matrix theory, but does receive a correction at two loops. There are no
contributions at higher loops. We explicitly calculate the two-loop term,
finding a non-zero result. We find a discrepancy with M(atrix)-theory. Although
the result has the right dependence on and for the scattering of zero
branes off the fixed point the factors of do not match. We also discuss
scattering in the orbifolds, and where we find the
predicted fractional charges.Comment: Discussion of the discrepancy with M(atrix)-theory is clarified. We
emphasize the fact that the main problem is not a numerical one but in the
factors of N. We also made minor corrections to the text, 24pp Te
Dynamical Decompactification and Three Large Dimensions
We study string gas dynamics in the early universe and seek to realize the
Brandenberger - Vafa mechanism - a goal that has eluded earlier works - that
singles out three or fewer spatial dimensions as the number which grow large
cosmologically. Considering wound string interactions in an impact parameter
picture, we show that a strong exponential suppression in the interaction rates
for d > 3 spatial dimensions reflects the classical argument that string
worldsheets generically intersect in at most four spacetime dimensions. This
description is appropriate in the early universe if wound strings are heavy -
wrapping long cycles - and diluted. We consider the dynamics of a string gas
coupled to dilaton-gravity and find that a) for any number of dimensions the
universe generically stays trapped in the Hagedorn regime and b) if the
universe fluctuates to a radiation regime any residual winding modes are
diluted enough so that they freeze-out in d > 3 large dimensions while they
generically annihilate for d = 3. In this sense the Brandenberger-Vafa
mechanism is operative.Comment: 20 pages, 2 figures, minor changes, updated figures, as will appear
in Phys.Rev.
Holographic Construction of Excited CFT States
We present a systematic construction of bulk solutions that are dual to CFT
excited states. The bulk solution is constructed perturbatively in bulk fields.
The linearised solution is universal and depends only on the conformal
dimension of the primary operator that is associated with the state via the
operator-state correspondence, while higher order terms depend on detailed
properties of the operator, such as its OPE with itself and generally involve
many bulk fields. We illustrate the discussion with the holographic
construction of the universal part of the solution for states of two
dimensional CFTs, either on or on . We compute the
1-point function both in the CFT and in the bulk, finding exact agreement. We
comment on the relation with other reconstruction approaches.Comment: 26 pages, 4 figures, v2: comments adde
Towards the lattice study of M-theory (II)
We present new results of the quenched simulations of the reduced D=4
supersymmetric Yang - Mills quantum mechanics for larger gauge groups SU(N),
2<N<9. The model, studied at finite temperature, reveals existence of the two
distinct regions which may be precursors of a black hole and the elementary D0
branes phases of M-theory conjectured in the literature. Present results for
higher groups confirm the picture found already for N=2. Similar behaviour is
observed in the preliminary simulations for the D=6 and D=10 models.Comment: Talk presented at XIX International Symposium on Lattice Field Theory
lattice2001(surfaces
Interaction of D-string with F-string: A Path-Integral Formalism
A path integral formalism is developed to study the interaction of an
arbitrary curved Dirichlet (D-) string with elementary excitations of the
fundumental (F-) string in bosonic string theory. Up to the next to leading
order in the derivative expansion, we construct the properly renormalized
vertex operator, which generalizes the one previously obtained for a D-particle
moving along a curved trajectory. Using this vertex, an attempt is further made
to quantize the D-string coordinates and to compute the quantum amplitude for
scattering between elementary excitations of the D- and F-strings. By studying
the dependence on the Liouville mode for the D-string, it is found that the
vertex in our approximation consists of an infinite tower of local vertex
operators which are conformally invariant on their respective mass-shell. This
analysis indicates that, unlike the D-particle case, an off-shell extension of
the interaction vertex would be necessary to compute the full amplitude and
that the realization of symmetry can be quite non-trivial when the dual
extended objects are simultaneously present. Possible future directions are
suggested.Comment: 23 pages, latex, no figure
Effects of precipitation uncertainty on discharge calculations for main river basins
This study quantifies the uncertainty in discharge calculations caused by uncertainty in precipitation input for 294 river basins worldwide. Seven global gridded precipitation datasets are compared at river basin scale in terms of mean annual and seasonal precipitation. The representation of seasonality is similar in all datasets, but the uncertainty in mean annual precipitation is large, especially in mountainous, arctic, and small basins. The average precipitation uncertainty in a basin is 30%, but there are strong differences between basins. The effect of this precipitation uncertainty on mean annual and seasonal discharge was assessed using the uncalibrated dynamic global vegetation and hydrology model Lund-Potsdam-Jena managed land (LPJmL), yielding even larger uncertainties in discharge (average 90%). For 95 basins (out of 213 basins for which measurements were available) calibration of model parameters is problematic because the observed discharge falls within the uncertainty of the simulated discharge. A method is presented to account for precipitation uncertainty in discharge simulations
Ultra--Planck Scattering in D=3 Gravity Theories
We obtain the high energy, small angle, 2-particle gravitational scattering
amplitudes in topologically massive gravity (TMG) and its two non-dynamical
constituents, Einstein and Chern--Simons gravity. We use 't Hooft's approach,
formally equivalent to a leading order eikonal approximation: one of the
particles is taken to scatter through the classical spacetime generated by the
other, which is idealized to be lightlike. The required geometries are derived
in all three models; in particular, we thereby provide the first explicit
asymptotically flat solution generated by a localized source in TMG. In
contrast to =4, the metrics are not uniquely specified, at least by naive
asymptotic requirements -- an indeterminacy mirrored in the scattering
amplitudes. The eikonal approach does provide a unique choice, however. We also
discuss the discontinuities that arise upon taking the limits, at the level of
the solutions, from TMG to its constituents, and compare with the analogous
topologically massive vector gauge field models.Comment: 20 pages, preprint BRX TH--337, DAMTP R93/5, ADP-93-204/M1
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