45 research outputs found
The sky is the limit: free boundary conditions in AdS Chern-Simons theory
We test the effects of new diffeomorphism invariant boundary terms in
SL(2,R)SL(2,R) Chern-Simons theory. The gravitational interpretation
corresponds to free AdS boundary conditions, without restrictions on the
boundary geometry. The boundary theory is the theory of a string in a target
AdS. Its Virasoro conditions can eliminate ghosts. Generalisations to
SL(N,R)SL(N,R) higher spin theories and many other questions are still
unexplored.Comment: 10 pages, Contribution to the Proceedings of the International
Workshop on Higher Spin Gauge Theories, Institute for Advanced Studies, NTU,
Singapore, November 4-6, 201
High-Energy Gravitational Scattering and Bose-Einstein Condensates of Gravitons
Quantum black holes are difficult to describe. We consider two seemingly
divergent approaches, high-energy scattering and the proposal to regard black
holes as Bose-Einstein condensates of gravitons, and establish a connection
between them. High-energy scattering is studied in the eikonal approximation,
which is processed further by a saddle-point approximation. The dominant
contribution to the scattering amplitude comes from a ladder diagram with the
exchange of N gravitons, and the number of gravitons follows a Poisson
distribution. This approximation supports the picture of a graviton
Bose-Einstein condensate with an extent equal the Schwarzschild radius, which
grows with N in a way determined by the saddle point. The approach permits
calculations of 1 / N corrections from the fluctuations around the saddle
points and we comment on these. Scattering methods might be useful probes of
quantum black holes, especially when interpreted in terms of condensates.Comment: 8 pages, 1 figur
Strings from 3D gravity: asymptotic dynamics of AdS gravity with free boundary conditions
Pure three-dimensional gravity in anti-de Sitter space can be formulated as
an SL(2,R) SL(2,R) Chern-Simons theory, and the latter can be reduced
to a WZW theory at the boundary. In this paper we show that AdS gravity
with free boundary conditions is described by a string at the boundary whose
target spacetime is also AdS. While boundary conditions in the standard
construction of Coussaert, Henneaux, and van Driel are enforced through
constraints on the WZW currents, we find that free boundary conditions are
partially enforced through the string Virasoro constraints.Comment: 21 pages; v2: typos corrected, published versio
Free Large N Supersymmetric Yang-Mills Theory as a String Theory
The strong version of Maldacena's AdS/CFT conjecture implies that the large N
expansion of free N=4 super-YM theory describes an interacting string theory in
the extreme limit of high spacetime curvature relative to the string length.
String states may then be understood as composed of SYM string bits. We
investigate part of the low-lying spectrum of the tensionless (zero-coupling)
limit and find a large number of states that are not present in the infinite
tension (strong-coupling) limit, notably several massless spin two particles.
We observe that all conformal dimensions are N-independent in the free SYM
theory, implying that masses in the corresponding string theory are unchanged
by string interactions. Degenerate string states do however mix in the
interacting string theory because of the complicated N-dependence of general
CFT two-point functions. Finally we verify the CFT crossing symmetry, which
corresponds to the dual properties of string scattering amplitudes. This means
that the SYM operator correlation functions define AdS dual models analogous to
the Minkowski dual models that gave rise to string theory.Comment: LaTeX2e, 15 pages, 3 figures, uses youngtab.sty; v2: references on
tensionless strings adde
D-particle Dynamics and Bound States
We study the low energy effective theory describing the dynamics of
D-particles. This corresponds to the quantum mechanical system obtained by
dimensional reduction of dimensional supersymmetric Yang-Mills theory to
dimensions and can be interpreted as the non relativistic limit of the
Born-Infeld action. We study the system of two like-charged D-particles and
find evidence for the existence of non-BPS states whose mass grows like
over the BPS mass. We give a string interpretation of this
phenomenon in terms of a linear potential generated by strings stretching from
the two D-particles. Some comments on the possible relations to black hole
entropy and eleven dimensional supergravity are also given.Comment: 16 pages, Latex. References and footnote adde