909 research outputs found
Moyal Representation of the String Field Star Product in the Presence of a B-background
In this paper we show that in the presence of an anti-symmetric tensor
-background, Witten's star algebra for open string fields persists to
possess the structure of a direct product of commuting Moyal pairs. The
interplay between the noncommutativity due to three-string overlap and that due
to the -background is our main concern. In each pair of noncommutative
directions parallel to the -background, the Moyal pairs mix string modes in
the two directions and are labeled, in addition to a continuous parameter, by
{\it two} discrete values as well. However, the Moyal parameters are
-dependent only for discrete pairs. We have also demonstrated the large-
contraction of the star algebra, with one of the discrete Moyal pairs dropping
out while the other giving rise to the center-of-mass noncommutative function
algebra.Comment: minor notation chang
The mass gap and vacuum energy of the Gross-Neveu model via the 2PPI expansion
We introduce the 2PPI (2-point-particle-irreducible) expansion, which sums
bubble graphs to all orders. We prove the renormalizibility of this summation.
We use it on the Gross-Neveu model to calculate the mass gap and vacuum energy.
After an optimization of the expansion, the final results are qualitatively
good.Comment: 14 pages,19 eps figures, revtex
Renormalization Group Summation and the Free Energy of Hot QCD
Using an approach developed in the context of zero-temperature QCD to
systematically sum higher order effects whose form is fixed by the
renormalization group equation, we sum to all orders the leading log (LL) and
next-to-leading log (NLL) contributions to the thermodynamic free energy in hot
QCD. While the result varies considerably less with changes in the
renormalization scale than does the purely perturbative result, a novel
ambiguity arises which reflects the strong scheme dependence of thermal
perturbation theory.Comment: 7 pages REVTEX4, 2 figures; v2: typos correcte
Large N expansion of the 2-matrix model
We present a method, based on loop equations, to compute recursively all the
terms in the large topological expansion of the free energy for the
2-hermitian matrix model. We illustrate the method by computing the first
subleading term, i.e. the free energy of a statistical physics model on a
discretized torus.Comment: 41 pages, 9 figures eps
Spiral Multi-component Structure in Pade - Approximant QCD
We present a graphical method of analyzing the infra-red fixed point
structure of Pade approximant QCD. The analysis shows a spiral multi-component
couplant structure as well as an infra-red attractor behavior of PQCD couplant
for all flavors .Comment: 78 pages, 4 tables, 44 graph
Isotopic composition of fragments in multifragmentation of very large nuclear systems: effects of the chemical equilibrium
Studies on the isospin of fragments resulting from the disassembly of highly
excited large thermal-like nuclear emitting sources, formed in the ^{197}Au +
^{197}Au reaction at 35 MeV/nucleon beam energy, are presented. Two different
decay systems (the quasiprojectile formed in midperipheral reactions and the
unique source coming from the incomplete fusion of projectile and target in the
most central collisions) were considered; these emitting sources have the same
initial N/Z ratio and excitation energy (E^* ~= 5--6 MeV/nucleon), but
different size. Their charge yields and isotopic content of the fragments show
different distributions. It is observed that the neutron content of
intermediate mass fragments increases with the size of the source. These
evidences are consistent with chemical equilibrium reached in the systems. This
fact is confirmed by the analysis with the statistical multifragmentation
model.Comment: 9 pages, 4 ps figure
Scale setting for alpha_s beyond leading order
We present a general procedure for incorporating higher-order information
into the scale-setting prescription of Brodsky, Lepage and Mackenzie. In
particular, we show how to apply this prescription when the leading coefficient
or coefficients in a series in the strong coupling alpha_s are anomalously
small and the original prescription can give an unphysical scale. We give a
general method for computing an optimum scale numerically, within dimensional
regularization, and in cases when the coefficients of a series are known. We
apply it to the heavy quark mass and energy renormalization in lattice NRQCD,
and to a variety of known series. Among the latter, we find significant
corrections to the scales for the ratio of e+e- to hadrons over muons, the
ratio of the quark pole to MSbar mass, the semi-leptonic B-meson decay width,
and the top decay width. Scales for the latter two decay widths, expressed in
terms of MSbar masses, increase by factors of five and thirteen, respectively,
substantially reducing the size of radiative corrections.Comment: 39 pages, 15 figures, 5 tables, LaTeX2
Chiral and Gluon Condensates at Finite Temperature
We investigate the thermal behaviour of gluon and chiral condensates within
an effective Lagrangian of pseudoscalar mesons coupled to a scalar glueball.
This Lagrangian mimics the scale and chiral symmetries of QCD. (Submitted to Z.
Phys. C)Comment: 20 pages + 7 figures (uuencoded compressed postscript files),
University of Regensburg preprint TPR-94-1
Double-Scaling Limit of Heterotic Bundles and Dynamical Deformation in CFT
We consider heterotic string theory on Eguchi-Hanson space, as a local model
of a resolved A_1 singularity in a six-dimensional flux compactification, with
an Abelian gauge bundle turned on and non-zero torsion. We show that in a
suitable double scaling limit, that isolates the physics near the non-vanishing
two-cycle, a worldsheet conformal field theory description can be found. It
contains a heterotic coset whose target space is conformal to Eguchi-Hanson.
Starting from the blow-down limit of the singularity, it can be viewed as a
dynamical deformation of the near-horizon fivebrane background. We analyze in
detail the spectrum of the theory in particular examples, as well as the
important role of worldsheet non-perturbative effects.Comment: 45 pages, no figures; ver2: typos corrected, references added, an
extra tadpole-free model covere
Kreuth IV: European consensus proposals for treatment of haemophilia with coagulation factor concentrates
Introduction: This report summarizes recommendations relating to haemophilia therapy arising from discussions among experts from 36 European countries during the \ue2\u80\u98Kreuth IV\ue2\u80\u99 meeting in May 2016. Aim: The objective of the meeting was for experts in the field of haemophilia from across Europe to draft resolutions regarding current issues relating to the treatment of haemophilia. Results: Hospitals providing clinical care for people with haemophilia and related disorders are strongly recommended to seek formal designation as either European Haemophilia Treatment Centres (EHTC) or European Haemophilia Comprehensive Care Centres (EHCCC). There should be agreed national protocols or guidelines on management of the ageing patient with haemophilia. The minimum consumption of factor VIII and IX concentrate in any country should be 4 IU and 0.5 IU per capita of general population respectively. Treatment for hepatitis C with direct-acting antiviral agents should be provided to all people with haemophilia on a priority basis. Genotype analysis should be offered to all patients with severe haemophilia. Genetic counselling, when given, should encompass the recommendation that genetic relatives of the affected person be advised to seek genetic counselling. People with inhibitors should have access to bypassing agents, immune tolerance and elective surgery. National or regional tenders for factor concentrates are encouraged. Outcome data including health related quality of life should be collected. Treatment with extended half-life factors should be individualized and protection against bleeding should be improved by increasing trough levels. Steps should be taken to understand and minimize the risk of inhibitor development. Conclusion: It is hoped that these recommendations will help to foster equity of haemophilia care throughout Europe
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