1,950 research outputs found
Symmetric Points in the Landscape as Cosmological Attractors
In the landscape, if there is to be any prospect of scientific prediction, it
is crucial that there be states which are distinguished in some way. The
obvious candidates are states which exhibit symmetries. Here we focus on states
which exhibit discrete symmetries. Such states are rare, but one can speculate
that they are cosmological attractors. We investigate the problem in model
landscapes and cosmologies which capture some of the features of candidate flux
landscapes. In non-supersymmetric theories we find no evidence that such states
might be cosmologically favored. In supersymmetric theories, simple arguments
suggest that states which exhibit symmetries might be. Our considerations
lead us to raise questions about some popular models of eternal inflation.Comment: 27 pages, latex, minor typo correcte
Wilson Loops as Precursors
There is substantial evidence that string theory on AdS_5 x S_5 is a
holographic theory in which the number of degrees of freedom scales as the area
of the boundary in Planck units. Precisely how the theory can describe bulk
physics using only surface degrees of freedom is not well understood. A
particularly paradoxical situation involves an event deep in the interior of
the bulk space. The event must be recorded in the (Schroedinger Picture) state
vector of the boundary theory long before a signal, such as a gravitational
wave, can propagate from the event to the boundary. In a previous paper with
Polchinski, we argued that the "precursor" operators which carry information
stored in the wave during the time when it vanishes in a neighborhood of the
boundary are necessarily non-local. In this paper we argue that the precursors
cannot be products of local gauge invariant operators such as the energy
momentum tensor. In fact gauge theories have a class of intrinsically non-local
operators which cannot be built from local gauge invariant objects. These are
the Wilson loops. We show that the precursors can be identified with Wilson
loops whose spatial size is dictated by the UV-IR connection.Comment: 23 pages, no figure
The SU(N) Matrix Model at Two Loops
Multi-loop calculations of the effective action for the matrix model are
important for carrying out tests of the conjectured relationship of the matrix
model to the low energy description of M-theory. In particular, comparison with
N-graviton scattering amplitudes in eleven-dimensional supergravity requires
the calculation of the effective action for the matrix model with gauge group
SU(N). A framework for carrying out such calculations at two loops is
established in this paper. The two-loop effective action is explicitly computed
for a background corresponding to the scattering of a single D0-brane from a
stack of N-1 D0-branes, and the results are shown to agree with known results
in the case N=2.Comment: 30 pages, 1 figure; v2 - typos corrected, references update
Black Hole Complementarity vs. Locality
The evaporation of a large mass black hole can be described throughout most
of its lifetime by a low-energy effective theory defined on a suitably chosen
set of smooth spacelike hypersurfaces. The conventional argument for
information loss rests on the assumption that the effective theory is a local
quantum field theory. We present evidence that this assumption fails in the
context of string theory. The commutator of operators in light-front string
theory, corresponding to certain low-energy observers on opposite sides of the
event horizon, remains large even when these observers are spacelike separated
by a macroscopic distance. This suggests that degrees of freedom inside a black
hole should not be viewed as independent from those outside the event horizon.
These nonlocal effects are only significant under extreme kinematic
circumstances, such as in the high-redshift geometry of a black hole.
Commutators of space-like separated operators corresponding to ordinary
low-energy observers in Minkowski space are strongly suppressed in string
theory.Comment: 32 pages, harvmac, 3 figure
Testing Superstring Theories with Gravitational Waves
We provide a simple transfer function that determines the effect of an early
matter dominated era on the gravitational wave background and show that a large
class of compactifications of superstring theory might be tested by
observations of the gravitational wave background from inflation. For large
enough reheating temperatures > 10^9 \GeV the test applies to all models
containing at least one scalar with mass < 10^{12}\GeV that acquires a large
initial oscillation amplitude after inflation and has only gravitational
interaction strength, i.e., a field with the typical properties of a modulus.Comment: 5 pages 2 figures, v2: changes in presentation, refs revised, matches
version in print in PR
Number operator-annihilation operator uncertainty as an alternative of the number-phase uncertainty relation
We consider a number operator-annihilation operator uncertainty as a well
behaved alternative to the number-phase uncertainty relation, and examine its
properties. We find a formulation in which the bound on the product of
uncertainties depends on the expectation value of the particle number. Thus,
while the bound is not a constant, it is a quantity that can easily be
controlled in many systems. The uncertainty relation is approximately saturated
by number-phase intelligent states. This allows us to define amplitude
squeezing, connecting coherent states to Fock states, without a reference to a
phase operator. We propose several setups for an experimental verification.Comment: 8 pages including 3 figures, revtex4; v2: typos corrected,
presentation improved; v3: presentation considerably extended; v4: published
versio
D-Sitter Space: Causal Structure, Thermodynamics, and Entropy
We study the entropy of concrete de Sitter flux compactifications and
deformations of them containing D-brane domain walls. We determine the relevant
causal and thermodynamic properties of these "D-Sitter" deformations of de
Sitter spacetimes. We find a string scale correspondence point at which the
entropy localized on the D-branes (and measured by probes sent from an observer
in the middle of the bubble) scales the same with large flux quantum numbers as
the entropy of the original de Sitter space, and at which Bousso's bound is
saturated by the D-brane degrees of freedom (up to order one coefficients) for
an infinite range of times. From the geometry of a static patch of D-Sitter
space and from basic relations in flux compactifications, we find support for
the possibility of a low energy open string description of the static patch of
de Sitter space.Comment: 46 pages, harvmac big; 14 figure
Constraints for quantum logic arising from conservation laws and field fluctuations
We explore the connections between the constraints on the precision of
quantum logical operations that arise from a conservation law, and those
arising from quantum field fluctuations. We show that the conservation-law
based constraints apply in a number of situations of experimental interest,
such as Raman excitations, and atoms in free space interacting with the
multimode vacuum. We also show that for these systems, and for states with a
sufficiently large photon number, the conservation-law based constraint
represents an ultimate limit closely related to the fluctuations in the quantum
field phase.Comment: To appear in J. Opt. B: Quantum Semiclass. Opt., special issue on
quantum contro
Wrapped membranes, matrix string theory and an infinite dimensional Lie algebra
We examine the algebraic structure of the matrix regularization for the
wrapped membrane on in the light-cone gauge. We give a
concrete representation for the algebra and obtain the matrix string theory
having the boundary conditions for the matrix variables corresponding to the
wrapped membrane, which is referred to neither Seiberg and Sen's arguments nor
string dualities. We also embed the configuration of the multi-wrapped membrane
in matrix string theory.Comment: 19 pages, 1 figure, references added, minor change
On the Bekenstein-Hawking Entropy, Non-Commutative Branes and Logarithmic Corrections
We extend earlier work on the origin of the Bekenstein-Hawking entropy to
higher-dimensional spacetimes. The mechanism of counting states is shown to
work for all spacetimes associated with a Euclidean doublet
of electric-magnetic dual brane pairs of type II
string-theory or M-theory wrapping the spacetime's event horizon plus the
complete internal compactification space. Non-Commutativity on the brane
worldvolume enters the derivation of the Bekenstein-Hawking entropy in a
natural way. Moreover, a logarithmic entropy correction with prefactor 1/2 is
derived.Comment: 17 pages, 2 figures; refs. adde
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