13,226 research outputs found
Towards a holographic realization of the quarkyonic phase
Large-N_c QCD matter at intermediate baryon density and low temperatures has
been conjectured to be in the so-called quarkyonic phase, i.e., to have a quark
Fermi surface and on top of it a confined spectrum of excitations. It has been
suggested that the presence of the quark Fermi surface leads to a homogeneous
phase with restored chiral symmetry, which is unstable towards creating
condensates breaking both the chiral and translational symmetry. Motivated by
these exotic features, we investigate properties of cold baryonic matter in the
single flavor Sakai-Sugimoto model searching for a holographic realization of
the quarkyonic phase. We use a simplified mean-field description and focus on
the regime of parametrically large baryon densities, of the order of the square
of the 't Hooft coupling, as they turn out to lead to new physical effects
similar to the ones occurring in the quarkyonic phase. One effect, the
appearance of a particular marginally stable mode breaking translational
invariance and linked with the presence of the Chern-Simons term in the flavor
brane Lagrangian, is known to occur in the deconfined phase of the
Sakai-Sugimoto model, but turns out to be absent here. The other, completely
new phenomenon that we, preliminarily, study using strong simplifying
assumptions are density-enhanced interactions of the flavor brane gauge field
with holographically represented baryons. These seem to significantly affect
the spectrum of vector and axial mesons and might lead to approximate chiral
symmetry restoration in the lowest part of the spectrum, where the mesons start
to qualitatively behave like collective excitations of the dense baryonic
medium. We discuss the relevance of these effects for holographic searches of
the quarkyonic phase and conclude with a discussion of various subtleties
involved in constructing a mean-field holographic description of a dense
baryonic medium.Comment: 31 pages, 16 figures; v2: inset plot in Fig. 10 removed, coloring in
Fig. 13 fixed, typos fixed, matches published versio
Modelling the quark propagator
The quark propagator is at the core of lattice hadron spectrum calculations
as well as studies in other nonperturbative schemes. We investigate the quark
propagator with an improved staggered action (Asqtad) and an improved gluon
action, which provides good quality data down to small quark masses. This is
used to construct ans\"{a}tze suitable for model hadron calculations as well as
adding to our intuitive understanding of QCD.Comment: Lattice2002(spectrum
A hole-ographic spacetime
We embed spherical Rindler space -- a geometry with a spherical hole in its
center -- in asymptotically AdS spacetime and show that it carries a
gravitational entropy proportional to the area of the hole. Spherical
AdS-Rindler space is holographically dual to an ultraviolet sector of the
boundary field theory given by restriction to a strip of finite duration in
time. Because measurements have finite durations, local observers in the field
theory can only access information about bounded spatial regions. We propose a
notion of Residual Entropy that captures uncertainty about the state of a
system left by the collection of local, finite-time observables. For
two-dimensional conformal field theories we use holography and the strong
subadditivity of entanglement to propose a formula for Residual Entropy and
show that it precisely reproduces the areas of circular holes in AdS3.
Extending the notion to field theories on strips with variable durations in
time, we show more generally that Residual Entropy computes the areas of all
closed, inhomogenous curves on a spatial slice of AdS3. We discuss the
extension to higher dimensional field theories, the relation of Residual
Entropy to entanglement between scales, and some implications for the emergence
of space from the RG flow of entangled field theories.Comment: v3: minor typos correcte
Black brane entropy and hydrodynamics: the boost-invariant case
The framework of slowly evolving horizons is generalized to the case of black
branes in asymptotically anti-de Sitter spaces in arbitrary dimensions. The
results are used to analyze the behavior of both event and apparent horizons in
the gravity dual to boost-invariant flow. These considerations are motivated by
the fact that at second order in the gradient expansion the hydrodynamic
entropy current in the dual Yang-Mills theory appears to contain an ambiguity.
This ambiguity, in the case of boost-invariant flow, is linked with a similar
freedom on the gravity side. This leads to a phenomenological definition of the
entropy of black branes. Some insights on fluid/gravity duality and the
definition of entropy in a time-dependent setting are elucidated.Comment: RevTeX, 42 pages, 4 figure
Localization of Eigenfunctions in the Stadium Billiard
We present a systematic survey of scarring and symmetry effects in the
stadium billiard. The localization of individual eigenfunctions in Husimi phase
space is studied first, and it is demonstrated that on average there is more
localization than can be accounted for on the basis of random-matrix theory,
even after removal of bouncing-ball states and visible scars. A major point of
the paper is that symmetry considerations, including parity and time-reversal
symmetries, enter to influence the total amount of localization. The properties
of the local density of states spectrum are also investigated, as a function of
phase space location. Aside from the bouncing-ball region of phase space,
excess localization of the spectrum is found on short periodic orbits and along
certain symmetry-related lines; the origin of all these sources of localization
is discussed quantitatively and comparison is made with analytical predictions.
Scarring is observed to be present in all the energy ranges considered. In
light of these results the excess localization in individual eigenstates is
interpreted as being primarily due to symmetry effects; another source of
excess localization, scarring by multiple unstable periodic orbits, is smaller
by a factor of .Comment: 31 pages, including 10 figure
Modelling the quark propagator
Submitted to Cornell University’s online archive www.arXiv.org in 2003 by Patrick O. Bowman. Post-print sourced from www.arxiv.org.The quark propagator is at the core of lattice hadron spectrum calculations as well as studies in other nonperturbative schemes. We investigate the quark propagator with an improved staggered action (Asqtad) and an improved gluon action, which provides good quality data down to small quark masses. This is used to construct ans\"{a}tze suitable for model hadron calculations as well as adding to our intuitive understanding of QCD.Patrick O. Bowman, Urs M. Heller, Derek B. Leinweber and Anthony G. Williamshttp://www.elsevier.com/wps/find/journaldescription.cws_home/505717/description#descriptio
Microscopic eigenvalue correlations in QCD with imaginary isospin chemical potential
We consider the chiral limit of QCD subjected to an imaginary isospin
chemical potential. In the epsilon-regime of the theory we can perform precise
analytical calculations based on the zero-momentum Goldstone modes in the
low-energy effective theory. We present results for the spectral correlation
functions of the associated Dirac operators.Comment: 13 pages, 2 figures, RevTe
Hall of Mirrors Scattering from an Impurity in a Quantum Wire
This paper develops a scattering theory to examine how point impurities
affect transport through quantum wires. While some of our new results apply
specifically to hard-walled wires, others--for example, an effective optical
theorem for two-dimensional waveguides--are more general. We apply the method
of images to the hard-walled guide, explicitly showing how scattering from an
impurity affects the wire's conductance. We express the effective cross section
of a confined scatterer entirely in terms of the empty waveguide's Green's
function, suggesting a way in which to use semiclassical methods to understand
transport properties of smooth wires. In addition to predicting some new
phenomena, our approach provides a simple physical picture for previously
observed effects such as conductance dips and confinement-induced resonances.Comment: 19 pages, 8 figures. Accepted for publication in Physical Review B.
Minor additions to text, added reference
Divergence-type 2+1 dissipative hydrodynamics applied to heavy-ion collisions
We apply divergence-type theory (DTT) dissipative hydrodynamics to study the
2+1 space-time evolution of the fireball created in Au+Au relativistic
heavy-ion collisions at 200 GeV. DTTs are exact hydrodynamic
theories that do no rely on velocity gradient expansions and therefore go
beyond second-order theories. We numerically solve the equations of motion of
the DTT for Glauber initial conditions and compare the results with those of
second-order theory based on conformal invariants (BRSS) and with data. We find
that the charged-hadron minumum-bias elliptic flow reaches its maximum value at
lower in the DTT, and that the DTT allows for a value of
slightly larger than that of the BRSS. Our results show that the differences
between viscous hydrodynamic formalisms are a significant source of uncertainty
in the precise extraction of from experiments.Comment: v4: 29 pages, 12 figures, minor changes. Final version as published
in Phys. Rev.
Scattering Theory of Kondo Mirages and Observation of Single Kondo Atom Phase Shift
We explain the origin of the Kondo mirage seen in recent quantum corral
Scanning Tunneling Microscope (STM) experiments with a scattering theory of
electrons on the surfaces of metals. Our theory combined with experimental data
provides the first direct observation of a single Kondo atom phase shift. The
Kondo mirage at the empty focus of an elliptical quantum corral is shown to
arise from multiple electron bounces off the walls of the corral in a manner
analagous to the formation of a real image in optics. We demonstrate our theory
with direct quantitive comparision to experimental data.Comment: 13 pages; significant clarifications of metho
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