arXiv subjects

Steven S. Gubser

Publications and source records attributed to Steven S. Gubser.

130 records · Page 8Linked to original sources

arXiv1997

Absorption by Branes and Schwinger Terms in the World Volume Theory

We study how coincident Dirichlet 3-branes absorb incident gravitons polarized along their world volume. We show that the absorption cross-section is determined by the central term in the correlator of two stress-energy tensors. The existence of a non-renormalization theorem for this central charge in four-dimensional N=4 supersymmetric Yang-Mills theories shows that the leading term at low energies in the absorption cross-section is not renormalized. This guarantees that the agreement of the cross-section with semiclassical supergravity, found in earlier work, survives all loop corrections. The connection between absorption of gravitons polarized along the brane and Schwinger terms in the stress-energy correlators of the world volume theory holds in general. We explore this connection to deduce some properties of the stress-energy tensor OPE's for 2-branes and 5-branes in 11 dimensions, as well as for 5-branes in 10 dimensions.

hep-th↗

arXiv1996

Emission of charged particles from four- and five-dimensional black holes

Recently Das and Mathur found that the leading order Hawking emission rate of neutral scalars by near-extremal $D=5$ black holes is exactly reproduced by a string theoretic model involving intersecting D-branes. We show that the agreement continues to hold for charged scalar emission. We further show that similar agreement can be obtained for a class of near-extremal $D=4$ black holes using a model inspired by M-theory. In this model, BPS saturated $D=4$ black holes with four charges are realized in M-theory as 5-branes triply intersecting over a string. The low-energy excitations are signals traveling on the intersection string.

hep-th↗

arXiv1994

A modified c=1 matrix model with new critical behavior

By introducing a $\int dt \, g\left(\Tr Φ^2(t)\right)^2$ term into the action of the $c=1$ matrix model of two-dimensional quantum gravity, we find a new critical behavior for random surfaces. The planar limit of the path integral generates multiple spherical ``bubbles'' which touch one another at single points. At a special value of $g$, the sum over connected surfaces behaves as $Δ^2 \logΔ$, where $Δ$ is the cosmological constant (the sum over surfaces of area $A$ goes as $A^{-3}$). For comparison, in the conventional $c=1$ model the sum over planar surfaces behaves as $Δ^2/ \logΔ$.

hep-th↗

arXiv1993

Scaling Functions for Baby Universes in Two-Dimensional Quantum Gravity

We apply the recently proposed transfer matrix formalism to 2-dimensional quantum gravity coupled to $(2, 2k-1)$ minimal models. We find that the propagation of a parent universe in geodesic (Euclidean) time is accompanied by continual emission of baby universes and derive a distribution function describing their sizes. The $k\to \infty~ (c\to -\infty)$ limit is generally thought to correspond to classical geometry, and we indeed find a classical peak in the universe distribution function. However, we also observe dramatic quantum effects associated with baby universes at finite length scales.

hep-th↗