8,986 research outputs found
Universal four-component Fermi gas in one dimension
A four-component Fermi gas in one dimension with a short-range four-body
interaction is shown to exhibit a one-dimensional analog of the BCS-BEC
crossover. Its low-energy physics is governed by a Tomonaga-Luttinger liquid
with three spin gaps. The spin gaps are exponentially small in the weak
coupling (BCS) limit where they arise from the charge-density-wave instability,
and become large in the strong coupling (BEC) limit because of the formation of
tightly-bound tetramers. We investigate the ground-state energy, the sound
velocity, and the gap spectrum in the BCS-BEC crossover and discuss exact
relationships valid in our system. We also show that a one-dimensional analog
of the Efimov effect occurs for five bosons while it is absent for fermions.
Our work opens up a very rich new field of universal few-body and many-body
physics in one dimension.Comment: 9 pages, 3 figures; (v2) Efimov effect for 5 bosons in 1D is
discussed; (v3) expanded versio
On the sign of the dilaton in the soft wall models
We elaborate on the existence of a spurious massless scalar mode in the
vector channel of soft-wall models with incorrectly chosen sign of the
exponential profile defining the wall. We re-iterate the point made in our
earlier paper and demonstrate that the presence of the mode is robust,
depending only on the infra-red asymptotics of the wall. We also re-emphasize
that desired confinement properties can be realized with the correct sign
choice.Comment: 10 page
Shear viscosity from R-charged AdS black holes
We compute the shear viscosity in the supersymmetric Yang-Mills theory dual
to the STU background. This is a thermal gauge theory with a chemical
potential. The quotient of the shear viscosity over the entropy density
exhibits no deviation from the well known result 1/4\pi.Comment: 9 pages, some references updated, abstract and some typos correcte
Viscosity Bound and Causality in Superfluid Plasma
It was argued by Brigante et.al that the lower bound on the ratio of the
shear viscosity to the entropy density in strongly coupled plasma is translated
into microcausality violation in the dual gravitational description. Since
transport properties of the system characterize its infrared dynamics, while
the causality of the theory is determined by its ultraviolet behavior, the
viscosity bound/microcausality link should not be applicable to theories that
undergo low temperature phase transitions. We present an explicit model of
AdS/CFT correspondence that confirms this fact.Comment: 27 pages, 5 figures. References added, typos fixe
A Phenomenological Description of the Non-Fermi-Liquid Phase of MnSi
In order to understand the non-Fermi-liquid behavior of MnSi under pressure
we propose a scenario on the basis of the multispiral state of the magnetic
moment.
This state can describe the recent critical experiment of the Bragg sphere in
the neutron scattering which is the key ingredient of the non-Fermi-liquid
behavior.Comment: 3 page
Bogoliubov-de Gennes study of trapped spin-imbalanced unitary Fermi gases
It is quite common that several different phases exist simultaneously in a
system of trapped quantum gases of ultra-cold atoms. One such example is the
strongly-interacting Fermi gas with two imbalanced spin species, which has
received a great amount of attention due to the possible presence of exotic
superfluid phases. By employing novel numerical techniques and algorithms, we
self-consistently solve the Bogoliubov de-Gennes equations, which describe
Fermi superfluids in the mean-field framework. From this study, we investigate
the novel phases of spin-imbalanced Fermi gases and examine the validity of the
local density approximation (LDA), which is often invoked in the extraction of
bulk properties from experimental measurements within trapped systems. We show
how the validity of the LDA is affected by the trapping geometry, number of
atoms and spin imbalance.Comment: 15 pages, 5 figures, to be published in New J. Phys. (focus issue on
"Strongly Correlated Quantum Fluids: From Ultracold Quantum Gases to QCD
Plasmas"
The Sound of Topology in the AdS/CFT Correspondence
Using the gauge/gravity correspondence, we study the properties of 2-point
correlation functions of finite-temperature strongly coupled gauge field
theories, defined on a curved space of general spatial topology with a dual
black hole description. We derive approximate asymptotic expressions for the
correlation functions and their poles, supported by exact numerical
calculations, and study their dependence on the dimension of spacetime and the
spatial topology. The asymptotic structure of the correlation functions depends
on the relation between the spatial curvature and the temperature, and is
noticeable when they are of the same order. In the case of a hyperbolic
topology, a specific temperature is identified for which exact analytical
solutions exist for all types of perturbations. The asymptotic structure of the
correlation functions poles is found to behave in a non-smooth manner when
approaching this temperature.Comment: 65 pages, LaTeX, 21 figures, 1 table; fixed a small error in
subsection 3.
Hydrodynamics at RHIC -- how well does it work, where and how does it break down?
I review the successes and limitations of the ideal fluid dynamic model in
describing hadron emission spectra from Au+Au collisions at the Relativistic
Heavy Ion Collider (RHIC).Comment: 8 pages, 4 figures. Invited talk presented at Strange Quark Matter
2004 (Cape Town, Sep. 15-20, 2004). Proceedings to appear in Journal of
Physics
Quarkonium from the Fifth Dimension
Adding fundamental matter of mass m_Q to N=4 Yang Mills theory, we study
quarkonium, and "generalized quarkonium" containing light adjoint particles. At
large 't Hooft coupling the states of spin<=1 are anomalously light (Kruczenski
et al., hep-th/0304032). We examine their form factors, and show these hadrons
are unlike any known in QCD. By a traditional yardstick they appear infinite in
size (as with strings in flat space) but we show that this is a failure of the
yardstick. All of the hadrons are actually of finite size ~ \sqrt{g^2N}/m_Q,
regardless of their radial excitation level and of how many valence adjoint
particles they contain. Certain form factors for spin-1 quarkonia vanish in the
large-g^2N limit; thus these hadrons resemble neither the observed J/Psi
quarkonium states nor rho mesons.Comment: 57 pages, LaTeX, 5 figure
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