473 research outputs found
Ground Rings and Their Modules in 2D Gravity with Matter
All solvable two-dimensional quantum gravity models have non-trivial BRST
cohomology with vanishing ghost number. These states form a ring and all the
other states in the theory fall into modules of this ring. The relations in the
ring and in the modules have a physical interpretation. The existence of these
rings and modules leads to nontrivial constraints on the correlation functions
and goes a long way toward solving these theories in the continuum approach.Comment: 13 page
Matrix Black Holes
Four and five dimensional extremal black holes with nonzero entropy have
simple presentations in M-theory as gravitational waves bound to configurations
of intersecting M-branes. We discuss realizations of these objects in matrix
models of M-theory, investigate the properties of zero-brane probes, and
propose a measure of their internal density. A scenario for black hole dynamics
is presented.Comment: 26 pages, harvmac; a few more references and additional comment
On the Boundary Dynamics of Chern-Simons Gravity
We study Chern-Simons theory with a complex G_C or a real G x G gauge group
on a manifold with boundary - this includes Lorentzian and Euclidean (anti-) de
Sitter (E/A)dS gravity for G=SU(2) or G=SL(2,R). We show that there is a
canonical choice of boundary conditions that leads to an unambiguous, fully
covariant and gauge invariant, off-shell derivation of the boundary action - a
G_C/G or G WZW model, coupled in a gauge invariant way to the boundary value of
the gauge field. In particular, for (E/A)dS gravity, the boundary action is a
WZW model with target space (E/A)dS_3, reminiscent of a worldsheet for
worldsheet mechanism. We discuss in some detail the properties of the boundary
theories that arise and we confront our results with various related
constructions in the literature.Comment: 22 pages, LaTeX2e, v2: JHEP3.cls, references and a footnote adde
Annulus Amplitudes in the Minimal Superstring
We study the annulus amplitudes in the (2,4) minimal superstring theory using
the continuum worldsheet approach. Our results reproduce the semiclassical
behavior of the wavefunctions of FZZT-branes recently studied in hep-th/0412315
using the dual matrix model. We also study the multi-point functions of neutral
FZZT-branes and find the agreement between their semiclassical limit and the
worldsheet annulus calculation.Comment: 15 pages, lanlma
Smooth Horizonless Geometries Deep Inside the Black-Hole Regime
This Letter has been highlighted by the editors as an Editor's Suggestion.This Letter has been highlighted by the editors as an Editor's Suggestion
Rolling Tachyons from Liouville theory
In this work we propose an exact solution of the c=1 Liouville model, i.e. of
the world-sheet theory that describes the homogeneous decay of a closed string
tachyon. Our expressions are obtained through careful extrapolation from the
correlators of Liouville theory with c > 25. In the c=1 limit, we find two
different theories which differ by the signature of Liouville field. The
Euclidean limit coincides with the interacting c=1 theory that was constructed
by Runkel and Watts as a limit of unitary minimal models. The couplings for the
Lorentzian limit are new. In contrast to the behavior at c > 1, amplitudes in
both c=1 models are non-analytic in the momenta and consequently they are not
related by Wick rotation.Comment: 22 page
ZZ brane amplitudes from matrix models
We study instanton contribution to the partition function of the one matrix
model in the k-th multicritical region, which corresponds to the (2,2k-1)
minimal model coupled to Liouville theory. The instantons in the one matrix
model are given by local extrema of the effective potential for a matrix
eigenvalue and identified with the ZZ branes in Liouville theory. We show that
the 2-instanton contribution in the partition function is universal as well as
the 1-instanton contribution and that the connected part of the 2-instanton
contribution reproduces the annulus amplitudes between the ZZ branes in
Liouville theory. Our result serves as another nontrivial check on the
correspondence between the instantons in the one matrix model and the ZZ branes
in Liouville theory, and also suggests that the expansion of the partition
function in terms of the instanton numbers are universal and gives
systematically ZZ brane amplitudes in Liouville theory.Comment: 29 pages, 4 figures; v2:how to scale x is generalized;
v3:introduction and the last section are revised, typos correcte
Evolving Spatially Aggregated Features from Satellite Imagery for Regional Modeling
Satellite imagery and remote sensing provide explanatory variables at
relatively high resolutions for modeling geospatial phenomena, yet regional
summaries are often desirable for analysis and actionable insight. In this
paper, we propose a novel method of inducing spatial aggregations as a
component of the machine learning process, yielding regional model features
whose construction is driven by model prediction performance rather than prior
assumptions. Our results demonstrate that Genetic Programming is particularly
well suited to this type of feature construction because it can automatically
synthesize appropriate aggregations, as well as better incorporate them into
predictive models compared to other regression methods we tested. In our
experiments we consider a specific problem instance and real-world dataset
relevant to predicting snow properties in high-mountain Asia
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