1,520 research outputs found
Where is the chiral critical point in 3-flavor QCD?
We determine the location of the second order endpoint of the line of first
order chiral phase transition in 3-flavor QCD at vanishing chemical potential.
Using Ferrenberg-Swendsen reweighting for two values of the quark mass we
determine the dependence of the transition line on the chemical potential and
locate the chiral critical point. For both quantities we find a significant
quark mass dependence.Comment: 3 pages, Lattice2003(nonzero), one reference exchange
The QCD phase transition at high temperature and low density
We study the thermal properties of QCD in the presence of a small quark
chemical potential . Derivatives of the phase transition point with
respect to are computed at for 2 and 3 flavors of p-4 improved
staggered fermions on a lattice. Moreover we contrast the case of
isoscalar and isovector chemical potentials, quantify the effect of
on the equation of state, and comment on the screening effect by dynamical
quarks and the complex phase of the fermion determinant in QCD with
.Comment: Lattice2002(nonzerot), 3 pages, 2 figure
The quark mass and dependence of the QCD chiral critical point
In order to study the QCD chiral critical point we investigate Binder
Cumulants of the chiral condensate. The results were obtained from simulations
of 3 and 2+1 flavors of standard staggered fermions and 3 flavors of p4
improved staggered fermions. The quark masses used are close to the physical
quark mass. To extract the dependence on quark mass and chemical potential we
apply a new reweighting technique based on a Taylor expansion of the action.
The reweighting accuracy is for the standard and ,
for the p4 action.Comment: 3 pages, 6 figures, Lattice2002(nonzerot
Diphoton production in gluon fusion at small transverse momentum
We discuss the production of photon pairs in gluon-gluon scattering in the
context of the position-space resummation formalism at small transverse
momentum. We derive the remaining unknown coefficients that arise at
, as well as the remaining coefficient that occurs
in the Sudakov factor. We comment on the impact of these coefficients on the
normalization and shape of the resummed transverse momentum distribution of
photon pairs, which comprise an important background to Higgs boson production
at the LHC.Comment: 11 pages, 3 figures; minor changes, additional referenc
QCD at non-zero temperature and density from the lattice
The study of systems as diverse as the cores of neutron stars and heavy-ion
collision experiments requires the understanding of the phase structure of QCD
at non-zero temperature, T, and chemical potential, mu_q. We review some of the
difficulties of performing lattice simulations of QCD with non-zero mu_q, and
outline the re-weighting method used to overcome this problem. This method is
used to determine the critical endpoint of QCD in the (mu_q,T) plane. We study
the pressure and quark number susceptibility at small mu_q.Comment: 5 pages, talk presented by C.R. Allton at the QCD Downunder
Conference, Barossa Valley and Adelaide, March 200
First experiences with Personal Networks as an enabling platform for service providers
By developing demonstrators and performing small-scale user trials, we found various opportunities and pitfalls for deploying personal networks (PNs) on a commercial basis. The demonstrators were created using as many as possible legacy devices and proven technologies. They deal with applications in the health sector, home services, tourism, and the transportation sector. This paper describes the various architectures and our experiences with the end users and the technology. We conclude that context awareness, service discovery, and content management are very important in PNs and that a personal network provider role is necessary to realize these functions under the assumptions we made. The PNPay Travel demonstrator suggests that PN service platforms provide an opportunity to develop true trans-sector services
The Equation of State for Two Flavor QCD at Non-zero Chemical Potential
We present results of a simulation of QCD on a 4x16^3 lattice with 2
continuum flavors of p4-improved staggered fermion with mass m/T=0.4.
Derivatives of the thermodynamic grand potential with respect to quark chemical
potential mu_q up to fourth order are calculated, enabling estimates of the
pressure, quark number density and associated susceptibilities as functions of
mu_q via Taylor series expansion. Discretisation effects associated with
various staggered fermion formulations are discussed in some detail. In
addition it is possible to estimate the radius of convergence of the expansion
as a function of temperature. We also discuss the calculation of energy and
entropy densities which are defined via mixed derivatives of the thermodynamic
grand potential with respect to the bare couplings and quark masses.Comment: 30 pages, LaTeX2e File, 17 Postscript figure
Remarks on the multi-parameter reweighting method for the study of lattice QCD at non-zero temperature and density
We comment on the reweighting method for the study of finite density lattice
QCD. We discuss the applicable parameter range of the reweighting method for
models which have more than one simulation parameter. The applicability range
is determined by the fluctuations of the modification factor of the Boltzmann
weight. In some models having a first order phase transition, the fluctuations
are minimized along the phase transition line if we assume that the pressure in
the hot and the cold phase is balanced at the first order phase transition
point. This suggests that the reweighting method with two parameters is
applicable in a wide range for the purpose of tracing out the phase transition
line in the parameter space. To confirm the usefulness of the reweighting
method for 2 flavor QCD, the fluctuations of the reweighting factor are
measured by numerical simulations for the cases of reweighting in the quark
mass and chemical potential directions. The relation with the phase transition
line is discussed. Moreover, the sign problem caused by the complex phase
fluctuations is studied.Comment: 20 page, 6 figure
Isolation and structure of rolliniastatin 2 : a new cell growth inhibitory acetogenin from Rollinia mucosa
Un nouvel inhibiteur de la croissance cellulaire, dénommé Rolliniastatine 2 a été isolé des graines de #Rollinia mucosa$ et sa structure déterminée. (Résumé d'auteur
CP Nonconservation in
CP violation effects in are examined. CP-odd,
-odd and -even observables can both be used to extract information on
the real and imaginary parts of Feynman amplitudes. Two Higgs doublet model
with CP violating phase from neutral Higgs exchange is used to estimate
possible effects.Comment: 9 pages, 4 Figures, Late
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