23 research outputs found
Counter-examples to the correlated stability conjecture
We demonstrate explicit counter-examples to the Correlated Stability
Conjecture (CSC), which claims that the horizon of a black brane is unstable
precisely if that horizon has a thermodynamic instability, meaning that its
matrix of susceptibilities has a negative eigenvalue. These examples involve
phase transitions near the horizon. Ways to restrict or revise the CSC are
suggested. One of our examples shows that N=1* gauge theory has a second order
chiral symmetry breaking phase transition at a temperature well above the
confinement scale.Comment: 18 pages, 5 figures. v2: minor improvements, reference adde
The stress tensor of a quark moving through N=4 thermal plasma
We develop the linear equations that describe graviton perturbations of
AdS_5-Schwarzschild generated by a string trailing behind an external quark
moving with constant velocity. Solving these equations allows us to evaluate
the stress tensor in the boundary gauge theory. Components of the stress tensor
exhibit directional structures in Fourier space at both large and small
momentum. We comment on the possible relevance of our results to relativistic
heavy ion collisions.Comment: 33 pages, 5 figures. v2: improved low K discussion; other minor
improvement
String creation in cosmologies with a varying dilaton
FRW solutions of the string theory low-energy effective actions are
described, yielding a dilaton which first decreases and then increases. We
study string creation in these backgrounds and find an exponential divergence
due to an initial space-like singularity. We conjecture that this singularity
may be removed by the effects of back-reaction, leading to a solution which at
early times is de Sitter space.Comment: 15 pages, latex, one figur
Stability of strings binding heavy-quark mesons
We investigate the stability against small deformations of strings dangling
into AdS_5-Schwarzschild from a moving heavy quark-anti-quark pair. We
speculate that emission of massive string states may be an important part of
the evolution of certain unstable configurations.Comment: 14 pages, 4 figure
Dissipation from a heavy quark moving through N=4 super-Yang-Mills plasma
Using AdS/CFT, we compute the Fourier space profile of generated by
a heavy quark moving through a thermal plasma of strongly coupled N=4
super-Yang-Mills theory. We find evidence of a wake whose description includes
gauge fields with large momenta. We comment on the possible relevance of our
results to relativistic heavy ion collisions.Comment: 17 pages, 2 figures. v2: reference added, other minor improvements.
v3: improved the phrasing describing directional structure
TeV String State Excitation via High Energy Cosmic Neutrinos
We construct the open-string scattering amplitudes for neutrino-gluon
collisions and evaluate the high energy neutrino-nucleon scattering cross
section via string state excitations in the TeV string-scale scenario. We find
that the neutrino-gluon scattering is the dominant contribution, 5-10 times
larger than neutrino-quark processes, though black hole production may be
larger than the string contribution at higher energies. We illustrate the
observability of the string signal at the Auger Observatory and the IceCube
neutrino telescope for a string scale about 1 TeV.Comment: version to appear in PL
Non-linear sigma models with anti-de Sitter target spaces
We present evidence that there is a non-trivial fixed point for the AdS_{D+1}
non-linear sigma model in two dimensions, without any matter fields or
additional couplings beyond the standard quadratic action subject to a
quadratic constraint. A zero of the beta function, both in the bosonic and
supersymmetric cases, appears to arise from competition between one-loop and
higher loop effects. A string vacuum based on such a fixed point would have
string scale curvature. The evidence presented is based on fixed-order
calculations carried to four loops (corresponding to O(\alpha'^3) in the
spacetime effective action) and on large D calculations carried to O(D^{-2})
(but to all orders in \alpha'). We discuss ways in which the evidence might be
misleading, and we discuss some features of the putative fixed point, including
the central charge and an operator of negative dimension. We speculate that an
approximately AdS_5 version of this construction may provide a holographic dual
for pure Yang-Mills theory, and that quotients of an AdS_3 version might stand
in for Calabi-Yau manifolds in compactifications to four dimensions.Comment: 44 pages, 4 figures. v2: references adde