3,552 research outputs found
Critical behavior of 3D Z(N) lattice gauge theories at zero temperature
Three-dimensional lattice gauge theories at zero temperature are
studied for various values of . Using a modified phenomenological
renormalization group, we explore the critical behavior of the generalized
model for . Numerical computations are used to simulate
vector models for for lattices with linear extension up
to . We locate the critical points of phase transitions and establish
their scaling with . The values of the critical indices indicate that the
models with belong to the universality class of the three-dimensional
model. However, the exponent derived from the heat capacity is
consistent with the Ising universality class. We discuss a possible resolution
of this puzzle. We also demonstrate the existence of a rotationally symmetric
region within the ordered phase for all at least in the finite
volume.Comment: 25 pages, 4 figures, 8 table
Interactions suppress Quasiparticle Tunneling at Hall Bar Constrictions
Tunneling of fractionally charged quasiparticles across a two-dimensional
electron system on a fractional quantum Hall plateau is expected to be strongly
enhanced at low temperatures. This theoretical prediction is at odds with
recent experimental studies of samples with weakly-pinched
quantum-point-contact constrictions, in which the opposite behavior is
observed. We argue here that this unexpected finding is a consequence of
electron-electron interactions near the point contact.Comment: 4 page
TMD PDF's: gauge invariance, RG properties and Wilson lines
The UV divergences associated with transverse-momentum dependent (TMD) parton
distribution functions (PDF) are calculated together with the ensuing one-loop
anomalous dimensions in the light-cone gauge. Time-reversal-odd effects in the
anomalous dimensions are observed and the role of Glauber gluons is discussed.
A generalized renormalization procedure of TMD PDFs is proposed, relying upon
the renormalization of contour-dependent operators with obstructions.Comment: 4 pages, 1 figure. Talk presented at the International Workshop on
Diffraction in High Energy and Nuclear Physics, La Londe-les-Maures, France,
9-14 Sept 2008. v2: 5 pages, preprint number and e-mail addresses adde
Perforated Duodenal Ulcer in Pregnancy—A Rare Cause of Acute Abdominal Pain in Pregnancy: A Case Report and Literature Review
Medical and surgical disorders in pregnancy can be can be quite challenging for the obstetrician gynaecologist even in resource rich countries. Reaching an accurate diagnosis and admininstering appropriate management can be difficult in the presence of an on-going pregnancy. The importance of involving specialist from other disciplines (multidisciplinary care) cannot be overemphasized. We present an interesting case of perforated duodenal ulcer in a pregnant patient, review the literature ,discuss the differential diagnosis and evaluate the management principles for this rare condition
Exclusive quasielastic production of dijets at hadronic colliders
We critically re-examine the calculation of central production of dijets in
quasi-elastic hadronic collisions. We find that the process is not dominated by
the perturbative contribution, and discuss several sources of uncertainties in
the calculation.Comment: 4 pages, talk given at Diffraction-2008, La Londe-les-Maures, France,
9-14 Sept 200
gamma* -> rhoT impact factor with twist three accuracy
We evaluate the impact factor of the transition gamma* -> rhoT taking into
account the twist 3 contributions. We show that a gauge invariant expression is
obtained with the help of QCD equations of motion. Our results are free of
end-point singularities. This opens the way to a consistent treatment of
factorization for exclusive processes with a transversally polarized vector
meson.Comment: 4 pages, 1 figure; To appear in the proceedings of Diffraction 2008:
International Workshop on Diffraction in High-Energy Physics, La
Londe-les-Maures, France, September 9-14, 200
Tails of probability density for sums of random independent variables
The exact expression for the probability density for sums of a
finite number of random independent terms is obtained. It is shown that the
very tail of has a Gaussian form if and only if all the random
terms are distributed according to the Gauss Law. In all other cases the tail
for differs from the Gaussian. If the variances of random terms
diverge the non-Gaussian tail is related to a Levy distribution for
. However, the tail is not Gaussian even if the variances are
finite. In the latter case has two different asymptotics. At small
and moderate values of the distribution is Gaussian. At large the
non-Gaussian tail arises. The crossover between the two asymptotics occurs at
proportional to . For this reason the non-Gaussian tail exists at finite
only. In the limit tends to infinity the origin of the tail is shifted
to infinity, i. e., the tail vanishes. Depending on the particular type of the
distribution of the random terms the non-Gaussian tail may decay either slower
than the Gaussian, or faster than it. A number of particular examples is
discussed in detail.Comment: 6 pages, 4 figure
Scaling Exponents in the Incommensurate Phase of the Sine-Gordon and U(1) Thirring Models
In this paper we study the critical exponents of the quantum sine-Gordon and
U(1) Thirring models in the incommensurate phase. This phase appears when the
chemical potential exceeds a critical value and is characterized by a
finite density of solitons. The low-energy sector of this phase is critical and
is described by the Gaussian model (Tomonaga-Luttinger liquid) with the
compactification radius dependent on the soliton density and the sine-Gordon
model coupling constant .
For a fixed value of , we find that the Luttinger parameter is
equal to 1/2 at the commensurate-incommensurate transition point and approaches
the asymptotic value away from it. We describe a possible phase
diagram of the model consisting of an array of weakly coupled chains. The
possible phases are Fermi liquid, Spin Density Wave, Spin-Peierls and Wigner
crystal.Comment: 10pages; Improved version; Submitted to Physical Review
Edge State Tunneling in a Split Hall Bar Model
In this paper we introduce and study the correlation functions of a chiral
one-dimensional electron model intended to qualitatively represent narrow Hall
bars separated into left and right sections by a penetrable barrier. The model
has two parameters representing respectively interactions between top and
bottom edges of the Hall bar and interactions between the edges on opposite
sides of the barrier. We show that the scaling dimensions of tunneling
processes depend on the relative strengths of the interactions, with repulsive
interactions across the Hall bar tending to make breaks in the barrier
irrelevant. The model can be solved analytically and is characterized by a
difference between the dynamics of even and odd Fourier components. We address
its experimental relevance by comparing its predictions with those of a more
geometrically realistic model that must be solved numerically.Comment: 13 pages, including 4 figures,final version as publishe
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