1,116 research outputs found
Spacetime Fluctuations in AdS/CFT
We compute fluctuations in the modular energy of the vacuum associated with a
Rindler-wedge in AdS spacetime in the context of AdS/CFT. We discuss the
possible effect of these energy fluctuations on the spacetime geometry, and on
the traversal time of a light beam propagating from the boundary to the bulk
and back.Comment: 25 pages, 1 figur
Observational Signatures of Quantum Gravity in Interferometers
We consider the uncertainty in the arm length of an interferometer due to
metric fluctuations from the quantum nature of gravity, proposing a concrete
microscopic model of energy fluctuations in holographic degrees of freedom on
the surface bounding a causally connected region of spacetime. In our model,
fluctuations longitudinal to the beam direction accumulate in the infrared and
feature strong long distance correlation in the transverse direction. This
leads to a signal that could be observed in a gravitational wave
interferometer. We connect the positional uncertainty principle arising from
our calculations to the 't Hooft gravitational S-matrix.Comment: 6 pages, 1 figur
On the partition sum of the NS five-brane
We study the Type IIA NS five-brane wrapped on a Calabi-Yau manifold X in a
double-scaled decoupling limit. We calculate the euclidean partition function
in the presence of a flat RR 3-form field. The classical contribution is given
by a sum over fluxes of the self-dual tensor field which reduces to a
theta-function. The quantum contributions are computed using a T-dual IIB
background where the five-branes are replaced by an ALE singularity. Using the
supergravity effective action we find that the loop corrections to the free
energy are given by B-model topological string amplitudes. This seems to
provide a direct link between the double-scaled little strings on the
five-brane worldvolume and topological strings. Both the classical and quantum
contributions to the partition function satisfy (conjugate) holomorphic anomaly
equations, which explains an observation of Witten relating topological string
theory to the quantization of three-form fields.Comment: 35 page
New perspective on space and time from Lorentz violation
I present a brief review on space and time in different periods of physics,
and then talk on the nature of space and time from physical arguments. I
discuss the ways to test such a new perspective on space and time through
searching for Lorentz violation in some physical processes. I also make an
introduce to a newly proposed theory of Lorentz violation from basic
considerations.Comment: 10 latex pages. Plenary talk at First LeCosPA Symposium: Towards
Ultimate Understanding of the Universe (LeCosPA2012), National Taiwan
University, Taipei, Taiwan, February 6-9, 201
On RG-flow and the Cosmological Constant
The AdS/CFT correspondence implies that the effective action of certain
strongly coupled large gauge theories satisfy the Hamilton-Jacobi equation
of 5d gravity. Using an analogy with the relativistic point particle, I
construct a low energy effective action that includes the Einstein action and
obeys a Callan-Symanzik-type RG-flow equation. It follows from the flow
equation that under quite general conditions the Einstein equations admit a
flat space-time solution, but other solutions with non-zero cosmological
constant are also allowed. I discuss the geometric interpretation of this
result in the context of warped compactifications.Comment: 11 pages, 1 figure, contribution to the proceedings of Strings '99,
misprint correcte
Entropic gravity, minimum temperature, and modified Newtonian dynamics
Verlinde's heuristic argument for the interpretation of the standard
Newtonian gravitational force as an entropic force is generalized by the
introduction of a minimum temperature (or maximum wave length) for the
microscopic degrees of freedom on the holographic screen. With the simplest
possible setup, the resulting gravitational acceleration felt by a test mass m
from a point mass M at a distance R is found to be of the form of the modified
Newtonian dynamics (MOND) as suggested by Milgrom. The corresponding MOND-type
acceleration constant is proportional to the minimum temperature, which can be
interpreted as the Unruh temperature of an emerging de-Sitter space. This
provides a possible explanation of the connection between local MOND-type
two-body systems and cosmology.Comment: 12 pages, v6: published versio
Matrix Theory, AdS/CFT and Higgs-Coulomb Equivalence
We discuss the relation between the Matrix theory definitions of a class of decoupled theories and their AdS/CFT description in terms of the corresponding near-horizon geometry. The near horizon geometry, naively part of the Coulomb branch, is embedded in the Higgs branch via a natural change of variables. The principles of the map apply to all DLCQ descriptions in terms of hyper-Kähler quotients, such as the ADHM quantum mechanics for the D1-D5 system. We then focus the (2,0) field theory, and obtain an explicit mapping from all states in the momentum sector of M5-branes to states in (a DLCQ version of) . We show that, even for a single D0-brane, the space-time coordinates become non-commuting variables, suggesting an inherent non-commutativity of space-time in the presence of field strengths even for theories with gravity
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