7,065 research outputs found
The electron thermal propagator at p>>T: An entire function of p_{0}
The retarded electron propagator S_{R}(p_{0},p) at high momentum p>>T was
shown by Blaizot and Iancu to be an entire function of complex p_{0}. In this
paper a specific form for S_{R}(p_{0},p) is obtained and checked by showing
that its temporal Fourier transform S_{R}(t, p) has the correct behavior at
large t. Potential infrared and collinear divergences from the emission of soft
photons do not occur.Comment: 8 page
Progress with PXIE MEBT Chopper
A capability to provide a large variety of bunch patterns is crucial for the
concept of the Project X serving MW-range beam to several experiments
simultaneously. This capability will be realized by the Medium Energy Beam
Transport's (MEBT) chopping system that will divert 80% of all bunches of the
initially 5mA, 2.1 MeV CW 162.5 MHz beam to an absorber according to a
pre-programmed bunch-by-bunch selection. Being considered one of the most
challenging components, the chopping system will be tested at the Project X
Injector Experiment (PXIE) facility that will be built at Fermilab as a
prototype of the Project X front end. The bunch deflection will be made by two
identical sets of travelling-wave kickers working in sync. Currently, two
versions of the kickers are being investigated: a helical 200 Ohm structure
with a switching-type 500 V driver and a planar 50 Ohm structure with a linear
250 V amplifier. This paper will describe the chopping system scheme and
functional specifications for the kickers, present results of electromagnetic
measurements of the models, discuss possible driver schemes, and show a
conceptual mechanical design.Comment: 3 pp. 3rd International Particle Accelerator Conference (IPAC 2012)
20-25 May 2012. New Orleans, Louisian
Comment on ``Damping of energetic gluons and quarks in high-temperature QCD''
Burgess and Marini have recently pointed out that the leading contribution to
the damping rate of energetic gluons and quarks in the QCD plasma, given by
, can be obtained by simple arguments obviating the need
of a fully resummed perturbation theory as developed by Braaten and Pisarski.
Their calculation confirmed previous results of Braaten and Pisarski, but
contradicted those proposed by Lebedev and Smilga. While agreeing with the
general considerations made by Burgess and Marini, I correct their actual
calculation of the damping rates, which is based on a wrong expression for the
static limit of the resummed gluon propagator. The effect of this, however,
turns out to be cancelled fortuitously by another mistake, so as to leave all
of their conclusions unchanged. I also verify the gauge independence of the
results, which in the corrected calculation arises in a less obvious manner.Comment: 5 page
The value of extended amygdala structures in emotive effects of narcogenic with diverse chemical structure
To clarify the value of the extended amygdala structures (bed nucleus, central nucleus of the amygdala and nucleus accumbens shell) in the mechanisms of unconditioned and conditioned reinforcement activated by various narcogenic, this paper carried out a neuropharmacological analysis of these effects, using blockade of dopamine receptors, GABA, opioids and CRF receptors within these brain structures, as well as an analysis of behavioral responses by self-stimulation (unconditioned reinforcement) and conditioned place preference (CPP) (conditioned reinforcement
Integrable hierarchy underlying topological Landau-Ginzburg models of D-type
A universal integrable hierarchy underlying topological Landau-Ginzburg
models of D-tye is presented. Like the dispersionless Toda hierarchy, the new
hierarchy has two distinct (``positive" and ``negative") set of flows. Special
solutions corresponding to topological Landau-Ginzburg models of D-type are
characterized by a Riemann-Hilbert problem, which can be converted into a
generalized hodograph transformation. This construction gives an embedding of
the finite dimensional small phase space of these models into the full space of
flows of this hierarchy. One of flat coordinates in the small phase space turns
out to be identical to the first ``negative" time variable of the hierarchy,
whereas the others belong to the ``positive" flows.Comment: 14 pages, Kyoto University KUCP-0061/9
The heavy fermion damping rate puzzle
: We examine again the problem of the damping rate of a moving heavy fermion
in a hot plasma within the resummed perturbative theory of Pisarski and
Braaten. The ansatz for its evaluation which relates it to the imaginary part
of the fermion propagator pole in the framework of a self-consistent approach
is critically analyzed. As already pointed out by various authors, the only way
to define the rate is through additional implementation of magnetic screening.
We show in detail how the ansatz works in this case and where we disagree with
other authors. We conclude that the self-consistent approach is not
satisfactory.Comment: 17 page
Singularity theory study of overdetermination in models for L-H transitions
Two dynamical models that have been proposed to describe transitions between
low and high confinement states (L-H transitions) in confined plasmas are
analysed using singularity theory and stability theory. It is shown that the
stationary-state bifurcation sets have qualitative properties identical to
standard normal forms for the pitchfork and transcritical bifurcations. The
analysis yields the codimension of the highest-order singularities, from which
we find that the unperturbed systems are overdetermined bifurcation problems
and derive appropriate universal unfoldings. Questions of mutual equivalence
and the character of the state transitions are addressed.Comment: Latex (Revtex) source + 13 small postscript figures. Revised versio
Dynamics of Two-Level System Interacting with Random Classical Field
The dynamics of a particle interacting with random classical field in a
two-well potential is studied by the functional integration method. The
probability of particle localization in either of the wells is studied in
detail. Certain field-averaged correlation functions for quantum-mechanical
probabilities and the distribution function for the probabilities of final
states (which can be considered as random variables in the presence of a random
field) are calculated. The calculated correlators are used to discuss the
dependence of the final state on the initial state. One of the main results of
this work is that, although the off-diagonal elements of density matrix
disappear with time, a particle in the system is localized incompletely
(wave-packet reduction does not occur), and the distribution function for the
probability of finding particle in one of the wells is a constant at infinite
time.Comment: 5 page
- …