948 research outputs found
Wilson Loop and the Treatment of Axial Gauge Poles
We consider the question of gauge invariance of the Wilson loop in the light
of a new treatment of axial gauge propagator proposed recently based on a
finite field-dependent BRS (FFBRS) transformation. We remark that as under the
FFBRS transformation the vacuum expectation value of a gauge invariant
observable remains unchanged, our prescription automatically satisfies the
Wilson loop criterion. Further, we give an argument for {\it direct}
verification of the invariance of Wilson loop to O(g^4) using the earlier work
by Cheng and Tsai. We also note that our prescription preserves the thermal
Wilson loop to O(g^2).Comment: 8 pages, LaTex; some typos related to equation (18) correcte
Hepatocyte Growth Factor Receptor c-Met Instructs T Cell Cardiotropism and Promotes T Cell Migration to the Heart via Autocrine Chemokine Release
© 2015 The Authors. Published by Elsevier Inc.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)This study was funded by the British Heart Foundation (RG/09/002/2642 to F.M.M.-B.) and the Medical Research Council of the UK (G0901084 to F.M.M.-B.). ImageStream X was funded by the Wellcome Trust (101604/Z/13/Z). This work forms part of the research themes contributing to the translational research portfolio of Barts and the London Cardiovascular Biomedical Research Unit, which is supported and funded by the National Institute of Health Research
The non-Abelian Debye screening length beyond leading order
In quantum electrodynamics, static electric fields are screened at non-zero
temperatures by charges in the plasma. The inverse screening length, or Debye
mass, may be analyzed in perturbation theory and is of order at
relativistic temperatures. An analogous situation occurs when non-Abelian gauge
theories are studied perturbatively, but the perturbative analysis breaks down
when corrections of order are considered. At this order, the Debye mass
depends on the non-perturbative physics of confinement, and a perturbative
``definition'' of the Debye mass as the pole of a gluon propagator does not
even make sense. In this work, we show how the Debye mass can be defined
non-perturbatively in a manifestly gauge invariant manner (in vector-like gauge
theories with zero chemical potential). In addition, we show how the
correction could be determined by a fairly simple, three-dimensional, numerical
lattice calculation of the perimeter-law behavior of large, adjoint-charge
Wilson loops.Comment: 30 pages, revtex format, 9 postscript figures included using epsf.st
Non-perturbative dynamics of hot non-Abelian gauge fields: beyond leading log approximation
Many aspects of high-temperature gauge theories, such as the electroweak
baryon number violation rate, color conductivity, and the hard gluon damping
rate, have previously been understood only at leading logarithmic order (that
is, neglecting effects suppressed only by an inverse logarithm of the gauge
coupling). We discuss how to systematically go beyond leading logarithmic order
in the analysis of physical quantities. Specifically, we extend to
next-to-leading-log order (NLLO) the simple leading-log effective theory due to
Bodeker that describes non-perturbative color physics in hot non-Abelian
plasmas. A suitable scaling analysis is used to show that no new operators
enter the effective theory at next-to-leading-log order. However, a NLLO
calculation of the color conductivity is required, and we report the resulting
value. Our NLLO result for the color conductivity can be trivially combined
with previous numerical work by G. Moore to yield a NLLO result for the hot
electroweak baryon number violation rate.Comment: 20 pages, 1 figur
Spectral function of spinless fermions on a one-dimensional lattice
We study the spectral function of interacting one-dimensional fermions for an
integrable lattice model away from half-filling. The divergent power-law
singularity of the spectral function near the single-particle or single-hole
energy is described by an effective x-ray edge type model. At low densities and
for momentum near the zone boundary, we find a second divergent singularity at
higher energies which is associated with a two-particle bound state. We use the
Bethe ansatz solution of the model to calculate the exact singularity exponents
for any momentum and for arbitrary values of chemical potential and interaction
strength in the critical regime. We relate the singularities of the spectral
function to the long-time decay of the fermion Green's function and compare our
predictions with numerical results from the time-dependent density matrix
renormalization group (tDMRG). Our results show that the tDMRG method is able
to provide accurate time decay exponents in the cases of power-law decay of the
Green's function. Some implications for the line shape of the dynamical
structure factor away from half-filling are also discussed. In addition, the
spectral weight of the Luttinger liquid result for the dynamical structure
factor of the Heisenberg model at zero field is compared with the exact
two-spinon contribution.Comment: 30 pages, 18 figure
The Finite Temperature SU(2) Savvidy Model with a Non-trivial Polyakov Loop
We calculate the complete one-loop effective potential for SU(2) gauge bosons
at temperature T as a function of two variables: phi, the angle associated with
a non-trivial Polyakov loop, and H, a constant background chromomagnetic field.
Using techniques broadly applicable to finite temperature field theories, we
develop both low and high temperature expansions. At low temperatures, the real
part of the effective potential V_R indicates a rich phase structure, with a
discontinuous alternation between confined (phi=pi) and deconfined phases
(phi=0). The background field H moves slowly upward from its zero-temperature
value as T increases, in such a way that sqrt(gH)/(pi T) is approximately an
integer. Beyond a certain temperature on the order of sqrt(gH), the deconfined
phase is always preferred. At high temperatures, where asymptotic freedom
applies, the deconfined phase phi=0 is always preferred, and sqrt(gH) is of
order g^2(T)T. The imaginary part of the effective potential is non-zero at the
global minimum of V_R for all temperatures. A non-perturbative magnetic
screening mass of the form M_m = cg^2(T)T with a sufficiently large coefficient
c removes this instability at high temperature, leading to a stable
high-temperature phase with phi=0 and H=0, characteristic of a
weakly-interacting gas of gauge particles. The value of M_m obtained is
comparable with lattice estimates.Comment: 28 pages, 5 eps figures; RevTeX 3 with graphic
Pinning of a solid--liquid--vapour interface by stripes of obstacles
We use a macroscopic Hamiltonian approach to study the pinning of a
solid--liquid--vapour contact line on an array of equidistant stripes of
obstacles perpendicular to the liquid. We propose an estimate of the density of
pinning stripes for which collective pinning of the contact line happens. This
estimate is shown to be in good agreement with Langevin equation simulation of
the macroscopic Hamiltonian. Finally we introduce a 2--dimensional mean field
theory which for small strength of the pinning stripes and for small capillary
length gives an excellent description of the averaged height of the contact
line.Comment: Plain tex, 12 pages, 3 figures available upon reques
Gauge Dependence of the Resummed Thermal Gluon Self Energy
The gauge dependence of the hot gluon self energy is examined in the context
of Pisarski's method for resumming hard thermal loops. Braaten and Pisarski
have used the Ward identities satisfied by the hard corrections to the n-point
functions to argue the gauge fixing independence of the leading order resummed
QCD plasma damping rate in covariant and strict Coulomb gauges. We extend their
analysis to include all linear gauges that preserve rotational invariance and
display explicitly the conditions required for gauge fixing independence. It is
shown that in covariant gauges the resummed damping constant is gauge fixing
independent only if an infrared regulator is explicitly maintained throughout
the calculation.Comment: 29 pages, report BI-TP 92/19, LPTHE-Orsay 92/32, WIN-TH-92/02 (June
1992
Yields and energy spectra of light charged particles emitted in neutron induced fission of <SUP>235</SUP>U
The yields and energy spectra of light charged particles emitted in the fission of 235U have been measured in the neutron energy range of 100 keV to 1 MeV. The yield of long range alpha particles is found to increase around 200 keV neutron energy compared to thermal fission. A low energy component observed in the energy spectrum was assigned to the tritons emitted in fission. The yield of this triton component is seen to have a marked increase around 500 keV. These results indicate that LCP yield is influenced by the transition state level characteristics
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