4,213 research outputs found
Closed String Tachyons, AdS/CFT, and Large N QCD
We find that tachyonic orbifold examples of AdS/CFT have corresponding
instabilities at small radius, and can decay to more generic gauge theories. We
do this by computing a destabilizing Coleman-Weinberg effective potential for
twisted operators of the corresponding quiver gauge theories, generalizing
calculations of Tseytlin and Zarembo and interpreting them in terms of the
large-N behavior of twisted-sector modes. The dynamically generated potential
involves double-trace operators, which affect large-N correlators involving
twisted fields but not those involving only untwisted fields, in line with
large-N inheritance arguments. We point out a simple reason that no such small
radius instability exists in gauge theories arising from freely acting
orbifolds, which are tachyon-free at large radius. When an instability is
present, twisted gauge theory operators with the quantum numbers of the
large-radius tachyons aquire VEVs, leaving a gauge theory with fewer degrees of
freedom in the infrared, analogous to but less extreme than ``decays to
nothing'' studied in other systems with broken supersymmetry. In some cases one
is left with pure glue QCD plus decoupled matter and U(1) factors in the IR,
which we thus conjecture is described by the corresponding (possibly strongly
coupled) endpoint of tachyon condensation in the M/String-theory dual.Comment: 28 pages, harvmac big. v2: references added; improved discussion of
RG improvemen
Holographic turbulence
We construct turbulent black holes in asymptotically AdS_4 spacetime by
numerically solving Einstein equations. Both the dual holographic fluid and
bulk geometry display signatures of an inverse cascade with the bulk geometry
being well approximated by the fluid/gravity gradient expansion. We argue that
statistically steady-state black holes dual to d dimensional turbulent flows
have horizons which are approximately fractal with fractal dimension D=d+4/3.Comment: 6 pages, 3 figure
Holographic Vortex Liquids and Superfluid Turbulence
Superfluid turbulence, often referred to as quantum turbulence, is a
fascinating phenomenon for which a satisfactory theoretical framework is
lacking. Holographic duality provides a systematic new approach to studying
quantum turbulence by mapping the dynamics of certain quantum theories onto the
dynamics of classical gravity. We use this gravitational description to
numerically construct turbulent flows in a holographic superfluid in two
spatial dimensions. We find that the superfluid kinetic energy spectrum obeys
the Kolmogorov -5/3 scaling law, as it does for turbulent flows in normal
fluids. We trace this scaling to a direct energy cascade by injecting energy at
long wavelengths and watching it flow to a short-distance scale set by the
vortex core size, where dissipation by vortex annihilation and vortex drag
becomes efficient. This is in sharp contrast with the inverse energy cascade of
normal fluid turbulence in two dimensions. We also demonstrate that the
microscopic dissipation spectrum has a simple geometric interpretation.Comment: 23 pages, 7 figures. Minor corrections made. Movies and supplementary
material available at http://turbulent.lns.mit.edu/Superflui
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