296 research outputs found
Antiferromagnetic S=1/2 Heisenberg Chain and the Two-flavor Massless Schwinger Model
An antiferromagnetic S=1/2 Heisenberg chain is mapped to the two-flavor
massless Schwinger model at \theta=\pi. The electromagnetic coupling constant
and velocity of light in the Schwinger model are determined in terms of the
Heisenberg coupling and lattice spacing in the spin chain system.Comment: 3 pages. LaTex2
About the holographic pseudo-Goldstone boson
Pseudo-Goldstone bosons in 4D strongly coupled theories have a dual
description in terms of 5D gauge theories in warped backgrounds. We introduce
systematic methods of computing the pseudo-Goldstone potential for an arbitrary
warp factor in 5D. When applied to electroweak symmetry breaking, our approach
clarifies the relation of physical observables to geometrical quantities in
five dimensions.Comment: 16 page
Aspects of Confinement and Chiral Dynamics in 2-d QED at Finite Temperature
We evaluate the Polyakov loop and string tension at zero and finite
temperature in Using bozonization the problem is reduced to solving
the Schr\"odinger equation with a particular potential determined by the ground
state. In the presence of two sources of opposite charges the vacuum angle
parameter changes by , independent of the number of
flavors. This, in turn, alters the chiral condensate. Particularly, in the one
flavor case through a simple computer algorithm, we explore the chiral dynamics
of a heavy fermion.Comment: 4 pages, 2 ps files, uses sprocl.sty. To appear in Proceedings of
DPF96 (August, Minnesota
Confinement and Chiral Dynamics in the Multi-flavor Schwinger Model
Two-dimensional QED with flavor fermions is solved at zero and finite
temperature with arbitrary fermion masses to explore QCD physics such as chiral
condensate and string tension. The problem is reduced to solving a
Schr\"odinger equation for degrees of freedom with a specific potential
determined by the ground state of the Schr\"odinger problem itself.Comment: 9 pages. 3 ps files and sprocl.sty attached. To appear in the
Proceedings of the QCD 96 workshop (March, Minnesota
Non-local symmetry breaking in Kaluza-Klein theories
Scherk-Schwarz gauge symmetry breaking of a D-dimensional field theory model
compactified on a circle is analyzed. It is explicitly shown that forbidden
couplings in the unbroken theory appear in the one-loop effective action only
in a non-local way, implying that they are finite at all orders in perturbation
theory. This result can be understood as a consequence of the local gauge
symmetry, but it holds true also in the global limit.Comment: v2: Wilson loop contributions and generalization to SU(N) included;
references added. v3: version to appear in Phys. Rev. Let
Effective theories of gauge-Higgs unification models in warped spacetime
We derive four-dimensional (4D) effective theories of the gauge-Higgs
unification models in the warped spacetime. The effective action can be
expressed in a simple form by neglecting subleading corrections to the wave
functions. We have shown in our previous works that some Higgs couplings to the
other fields are suppressed by factors that depend on from the
values in the standard model. Here is the Wilson line phase
along the fifth dimension, which characterizes the electroweak symmetry
breaking. The effective action derived here explicitly shows a nonlinear
structure of the Higgs sector, which clarifies the origins of those suppression
factors.Comment: 36 pages, 1 figur
Renormal-order improvement of the Schwinger mass
The massive Schwinger model may be analysed by a perturbation expansion in
the fermion mass. However, the results of this mass perturbation theory are
sensible only for sufficiently small fermion mass. By performing a
renormal-ordering, we arrive at a chiral perturbation expansion where the
expansion parameter remains small even for large fermion mass. We use this
renormal-ordered chiral perturbation theory for a computation of the Schwinger
mass and compare our results with lattice computations.Comment: Latex file, 13 pages, 3 figures, needed macro: psbox.te
Gauge-Higgs Dark Matter
When the anti-periodic boundary condition is imposed for a bulk field in
extradimensional theories, independently of the background metric, the lightest
component in the anti-periodic field becomes stable and hence a good candidate
for the dark matter in the effective 4D theory due to the remaining accidental
discrete symmetry. Noting that in the gauge-Higgs unification scenario,
introduction of anti-periodic fermions is well-motivated by a phenomenological
reason, we investigate dark matter physics in the scenario. As an example, we
consider a five-dimensional SO(5)\timesU(1)_X gauge-Higgs unification model
compactified on the with the warped metric. Due to the structure of
the gauge-Higgs unification, interactions between the dark matter particle and
the Standard Model particles are largely controlled by the gauge symmetry, and
hence the model has a strong predictive power for the dark matter physics.
Evaluating the dark matter relic abundance, we identify a parameter region
consistent with the current observations. Furthermore, we calculate the elastic
scattering cross section between the dark matter particle and nucleon and find
that a part of the parameter region is already excluded by the current
experimental results for the direct dark matter search and most of the region
will be explored in future experiments.Comment: 16 pages, 2 figure
Boundary Effects in 2+1 Dimensional Maxwell-Chern-Simons Theory
The boundary effects in the screening of an applied magnetic field in a
finite temperature 2+1 dimensional model of charged fermions minimally coupled
to Maxwell and Chern-Simons fields are investigated. It is found that in a
sample with only one boundary -a half-plane- a total Meissner effect takes
place, while in a sample with two boundaries -an infinite strip- the external
magnetic field partially penetrates the material.Comment: revte
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