10,229 research outputs found
Universal properties of the U(1) current at deconfined quantum critical points: comparison with predictions from gauge/gravity duality
The deconfined quantum critical point of a two-dimensional SU(N)
antiferromagnet is governed by an Abelian Higgs model in spacetime
dimensions featuring complex scalar fields. In this context, we derive for
an exact formula for the central charge of the U(1) current in
terms of the gauge coupling at quantum criticality and compare it with the
corresponding result obtained using gauge-gravity duality. There is a
remarkable similarity precisely for . In this case the amplitude of the
current correlation function has the same form as predicted by the
gauge-gravity duality. We also compare finite temperature results for the
charge susceptibility in the large limit with the result predicted by the
gauge-gravity duality. Our results suggest that condensed matter systems at
quantum criticality may provide interesting quantitative tests of the
gauge-gravity duality even in absence of supersymmetry.Comment: 4.5 pages, 1 figure; v2: accepted in PRD, text restructured to make
presentation/discussion clearer, references adde
: three-body final state interactions and isospin states
Final state interactions are considered to formulate the meson decay
amplitude for the channel. The Faddeev decomposition of the
Bethe-Salpeter equation is used in order to build a relativistic three-body
model within the light-front framework. The S-wave scattering amplitude for the
system is considered in the and isospin channels with the
set of inhomogeneous integral equations solved perturbatively. In comparison
with previous results for the meson decay in the same channel, one has to
consider the different partonic processes, which build the source amplitudes,
and the larger absorption to other decay channels appears, that are important
features to be addressed. As in the decay case, the convergence of the
rescattering perturbative series is also achieved with two-loop contributions.Comment: 10 pages, 4 figure
Phase structure of Abelian Chern-Simons gauge theories
We study the effect of a Chern-Simons (CS) term in the phase structure of two
different Abelian gauge theories. For the compact Maxwell-Chern-Simons theory,
we obtain that for values of the CS coupling with ,
the theory is equivalent to a gas of closed loops with contact interaction,
exhibiting a phase transition in the universality class. We also employ
Monte Carlo simulations to study the noncompact U(1) Abelian Higgs model with a
CS term. Finite size scaling of the third moment of the action yields critical
exponents and that vary continuously with the strength of the CS
term, and a comparison with available analytical results is made.Comment: RevTex4, 4 pages, 1 figure; v3: improvements and corrections made in
the first part of the paper; references added. To be published in Europhysics
Letter
Compact U(1) gauge theories in 2+1 dimensions and the physics of low dimensional insulating materials
Compact abelian gauge theories in dimensions arise often as an
effective field-theoretic description of models of quantum insulators. In this
paper we review some recent results about the compact abelian Higgs model in
in that context.Comment: 5 pages, 3 figures; based on talk by F.S. Nogueira in the Aachen
HEP2003 conferenc
Ground State of the Hydrogen Atom via Dirac Equation in a Minimal Length Scenario
In this work we calculate the correction to the ground state energy of the
hydrogen atom due to contributions arising from the presence of a minimal
length. The minimal length scenario is introduced by means of modifying the
Dirac equation through a deformed Heisenberg algebra (kempf algebra). With the
introduction of the Coulomb potential in the new Dirac energy operator, we
calculate the energy shift of the ground state of the hydrogen atom in first
order of the parameter related to the minimal length via perturbation theory.Comment: 11 page
Color-suppression of non-planar diagrams in bosonic bound states
We study the suppression of non-planar diagrams in a scalar QCD model of a
meson system in space-time dimensions due to the inclusion of the color
degrees of freedom. As a prototype of the color-singlet meson, we consider a
flavor-nonsinglet system consisting of a scalar-quark and a scalar-antiquark
with equal masses exchanging a scalar-gluon of a different mass, which is
investigated within the framework of the homogeneous Bethe-Salpeter equation.
The equation is solved by using the Nakanishi representation for the manifestly
covariant bound-state amplitude and its light-front projection. The resulting
non-singular integral equation is solved numerically. The damping of the impact
of the cross-ladder kernel on the binding energies are studied in detail. The
color-suppression of the cross-ladder effects on the light-front wave function
and the elastic electromagnetic form factor are also discussed. As our results
show, the suppression appears significantly large for , which supports
the use of rainbow-ladder truncations in practical nonperturbative calculations
within QCD.Comment: 12 pages, 7 figures. To appear in Physics Letters
Solving the three-body bound-state Bethe-Salpeter equation in Minkowski space
The scalar three-body Bethe-Salpeter equation, with zero-range interaction,
is solved in Minkowski space by direct integration of the four-dimensional
integral equation. The singularities appearing in the propagators are treated
properly by standard analytical and numerical methods, without relying on any
ansatz or assumption. The results for the binding energies and transverse
amplitudes are compared with the results computed in Euclidean space. A fair
agreement between the calculations is found.Comment: 10 pages, 2 figures, version accepted for publication in Phys. Lett.
- …