220 research outputs found
Black hole thermalization rate from brane anti-brane model
We develop the quasi-particle picture for Schwarzchild and far from extremal
black holes. We show that the thermalization equations of the black hole is
recovered from the model of branes and anti-branes. This can also be viewed as
a field theory explanation of the relationship between area and entropy for
these black holes. As a by product the annihilation rate of branes and
anti-branes is computed.Comment: 11 pages, late
Holographic U(1)_A and String Creation
We analyze the resolution of the U(1)_A problem in the Sakai-Sugimoto
holographic dual of large N_c QCD at finite temperature. It has been shown that
in the confining phase the axial symmetry is broken at order 1/N_c, in
agreement with the ideas of Witten and Veneziano. We show that in the
deconfined phase the axial symmetry remains unbroken to all orders in 1/N_c. In
this case the breaking is due to instantons which are described by spacelike
D0-branes, in agreement with 'tHooft's resolution. The holographic dual of the
symmetry breaking fermion condensate is a state of spacelike strings between
the D0-brane and the flavor D8-branes, which result from a spacelike version of
the string creation effect. In the intermediate phase of deconfinement with
broken chiral symmetry the instanton gas approximation is possibly regulated in
the IR, which would imply an eta' mass-squared of order exp(-N_c).Comment: 18 pages, 19 figures, minor change
Holographic representation of local bulk operators
The Lorentzian AdS/CFT correspondence implies a map between local operators
in supergravity and non-local operators in the CFT. By explicit computation we
construct CFT operators which are dual to local bulk fields in the
semiclassical limit. The computation is done for general dimension in global,
Poincare and Rindler coordinates. We find that the CFT operators can be taken
to have compact support in a region of the complexified boundary whose size is
set by the bulk radial position. We show that at finite N the number of
independent commuting operators localized within a bulk volume saturates the
holographic bound.Comment: 36 pages, LaTeX, 4 eps figure
Constructing local bulk observables in interacting AdS/CFT
Local operators in the bulk of AdS can be represented as smeared operators in
the dual CFT. We show how to construct these bulk observables by requiring that
the bulk operators commute at spacelike separation. This extends our previous
work by taking interactions into account. Large-N factorization plays a key
role in the construction. We show diagrammatically how this procedure is
related to bulk Feynman diagrams.Comment: 41 pages, LaTeX. v2: reference correcte
Local bulk operators in AdS/CFT: a boundary view of horizons and locality
We develop the representation of local bulk fields in AdS by non-local
operators on the boundary, working in the semiclassical limit and using AdS_2
as our main example. In global coordinates we show that the boundary operator
has support only at points which are spacelike separated from the bulk point.
We construct boundary operators that represent local bulk operators inserted
behind the horizon of the Poincare patch and inside the Rindler horizon of a
two dimensional black hole. We show that these operators respect bulk locality
and comment on the generalization of our construction to higher dimensional AdS
black holes.Comment: 28 pages, 4 figures, late
Striped instability of a holographic Fermi-like liquid
We consider a holographic description of a system of strongly-coupled
fermions in 2+1 dimensions based on a D7-brane probe in the background of
D3-branes. The black hole embedding represents a Fermi-like liquid. We study
the excitations of the Fermi liquid system. Above a critical density which
depends on the temperature, the system becomes unstable towards an
inhomogeneous modulated phase which is similar to a charge density and spin
wave state. The essence of this instability can be effectively described by a
Maxwell-axion theory with a background electric field. We also consider the
fate of zero sound at non-zero temperature.Comment: 16 pages, 9 figures; v2: added discussion and one figure. Typos
correcte
Quantum Hall Effect in a Holographic Model
We consider a holographic description of a system of strongly coupled
fermions in 2+1 dimensions based on a D7-brane probe in the background of
D3-branes, and construct stable embeddings by turning on worldvolume fluxes. We
study the system at finite temperature and charge density, and in the presence
of a background magnetic field. We show that Minkowski-like embeddings that
terminate above the horizon describe a family of quantum Hall states with
filling fractions that are parameterized by a single discrete parameter. The
quantization of the Hall conductivity is a direct consequence of the
topological quantization of the fluxes. When the magnetic field is varied
relative to the charge density away from these discrete filling fractions, the
embeddings deform continuously into black-hole-like embeddings that enter the
horizon and that describe metallic states. We also study the thermodynamics of
this system and show that there is a first order phase transition at a critical
temperature from the quantum Hall state to the metallic state.Comment: v2: 27 pages, 12 figures. There is a major revision in the
quantitative analysis. The qualitative results and conclusions are unchanged,
with one exception: we show that the quantum Hall state embeddings, which
exist for discrete values of the filling fraction, deform continuously into
metallic state embeddings away from these filling fraction
Decoherent Neutrino Mixing, Dark Energy and Matter-Antimatter Asymmetry
A CPT violating decoherence scenario can easily account for all the
experimental evidence in the neutrino sector including LSND. In this work it is
argued that this framework can also accommodate the Dark Energy content of the
Universe, as well as the observed matter-antimatter asymmetry.Comment: 6 pages, no figures, some typos corrected, and discussion modified
below eq (3), no effects on conclusion
Topologically induced local P and CP violation in QCD x QED
The existence of topological solutions and axial anomaly open a possibility
of P and CP violation in QCD. For a reason that has not yet been established
conclusively, this possibility is not realized in strong interactions - the
experimental data indicate that a global P and CP violation in QCD is absent.
Nevertheless, the fluctuations of topological charge in QCD vacuum, although
not observable directly, are expected to play an important role in the breaking
of symmetry and in the mass spectrum and other properties of hadrons.
Moreover, in the presence of very intense external electromagnetic fields
topological solutions of QCD can induce local P- and CP-odd effects in the
gauge theory that can be observed in experiment
directly. Here I show how these local parity-violating phenomena can be
described by using the Maxwell-Chern-Simons, or axion, electrodynamics as an
effective theory. Local P- and CP- violation in hot QCD matter can be observed
in experiment through the "chiral magnetic effect" - the separation of electric
charge along the axis of magnetic field. Very recently, STAR Collaboration
presented an observation of the electric charge asymmetry with respect to
reaction plane in relativistic heavy ion collisions at RHIC.Comment: 24 pages, 6 figures; prepared for the special issue of Annals of
Physic
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