233 research outputs found
Magnetic susceptibility and equation of state of N_f = 2+1 QCD with physical quark masses
We determine the free energy of strongly interacting matter as a function of
an applied constant and uniform magnetic field. We consider N_f = 2+1 QCD with
physical quark masses, discretized on a lattice by stout improved staggered
fermions and a tree level improved Symanzik pure gauge action, and explore
three different lattice spacings. For magnetic fields of the order of those
produced in non-central heavy ion collisions (eB ~ 0.1 GeV^2) strongly
interacting matter behaves like a medium with a linear response, and is
paramagnetic both above and below the deconfinement transition, with a
susceptibility which steeply rises in the deconfined phase. We compute the
equation of state, showing that the relative increase in the pressure due to
the magnetic field gets larger around the transition, and of the order of 10 %
for eB ~ 0.1 GeV^2.Comment: 11 pages, 10 figures, 3 tables. Final version published in Physical
Review
Magnetic Susceptibility of Strongly Interacting Matter across the Deconfinement Transition
We propose a method to determine the total magnetic susceptibility of
strongly interacting matter by lattice QCD simulations, and present first
numerical results for the theory with two light flavors, which suggest a weak
magnetic activity in the confined phase and the emergence of strong
paramagnetism in the deconfined, Quark-Gluon Plasma phase.Comment: 6 pages, 6 figures, 2 tables. Final version published in Physical
Review Letter
Roberge-Weiss endpoint at the physical point of QCD
We study the phase diagram of QCD in the plane and
investigate the critical point corresponding to the onset of the Roberge-Weiss
transition, which is found for imaginary values of . We make use of
stout improved staggered fermions and of the tree level Symanzik gauge action,
and explore four different sets of lattice spacings, corresponding to , and different spatial sizes, in order to assess the universality
class of the critical point. The continuum extrapolated value of the endpoint
temperature is found to be MeV, i.e. , where is the chiral pseudocritical temperature
at zero chemical potential, while our finite size scaling analysis, performed
on and lattices, provides evidence for a critical point in
the Ising universality class.Comment: 10 pages, 14 eps figures, 2 tables, final version published in
Physical Review
Curvature of the chiral pseudo-critical line in QCD: continuum extrapolated results
We determine the curvature of the pseudo-critical line of strong interactions
by means of numerical simulations at imaginary chemical potentials. We consider
stout improved staggered fermions with physical quark masses and the
tree level Symanzik gauge action, and explore four different sets of lattice
spacings, corresponding to , in order to extrapolate results
to the continuum limit. Our final estimate is .Comment: 11 pages, 10 figures, 4 tables. Version to appear in Physical Review
Curvature of the chiral pseudo-critical line in QCD
We determine the curvature of the pseudo-critical line of strong interactions
by means of numerical simulations at imaginary chemical potentials. We consider
stout improved staggered fermions with physical quark masses and the
tree level Symanzik gauge action, and explore two different sets of lattice
spacings, corresponding to temporal extensions and . Both
the renormalized chiral condensate and the renormalized chiral susceptibility
are used to locate the transition. The determinations obtained from the two
quantities are in good agreement, a preliminary continuum extrapolation yields
. We also investigate the impact of a non-zero strange
quark chemical potential and compare our results to previous determinations in
the literature, discussing the possible sources of systematic errors affecting
the various procedures.Comment: 16 pages, 12 figures, 11 tables. Published versio
Anisotropy of the quark-antiquark potential in a magnetic field
We investigate the static -potential for QCD at
the physical point in the presence of a constant and uniform external magnetic
field. The potential is found to be anisotropic and steeper in the directions
transverse to the magnetic field than in the longitudinal one. In particular,
when compared to the standard case with zero background field, the string
tension increases (decreases) in the transverse (longitudinal) direction, while
the absolute value of the Coulomb coupling and the Sommer parameter show an
opposite behavior.Comment: 6 pages, 5 figures, 1 table. Final published versio
ArcVIEW: a LabVIEW-based astronomical instrument control system
To meet the needs of the SOAR 4.2-m telescope first-generation instrument suite, as well as new instruments for the Blanco 4-m telescope, we developed a new camera controller system called ArcVIEW. In order to provide a strong foundation and rapid development cycle, we decided to build the system using National Instrument's LabVIEW environment. The advantages of this approach centers on the tools available for rapid prototyping, integration and testing of components. Over the past 2 years, we have taken ArcVIEW from a design document to the point of controlling two new instruments being built at CTIO. The IR imager, ISPI, will complete final testing this semester and go into use on the Blanco telescope in September 2002. The second instrument, the SOAR Optical Imager, is due for completion this semester and will be the commissioning instrument for the SOAR telescope, for which first light is expected in early 2003
dependence in trace deformed Yang-Mills theory: a lattice study
In this paper we investigate, by means of numerical lattice simulations, the
topological properties of the trace deformed Yang-Mills theory defined
on . More precisely, we evaluate the topological
susceptibility and the coefficient (related to the fourth cumulant of the
topological charge distribution) of this theory for different values of the
lattice spacing and of the compactification radius. In all the cases we find
results in good agreement with the corresponding ones of the standard
Yang-Mills theory on .Comment: 6 pages, 4 figures, published versio
Screening masses in strong external magnetic fields
We present results for the (color)magnetic and (color)electric screening
masses of the Quark-Gluon Plasma in the presence of an external magnetic field.
The screening masses are extracted from the correlators of Polyakov loops,
determined by lattice QCD simulations at the physical point. We explore
temperatures in the range and magnetic field intensities up to . We find that both screening masses are increasing
functions of the magnetic field and that the dependence on becomes weaker
for larger temperatures. In the case of the magnetic screening mass a slight
anisotropy is also observable.Comment: 8 pages, 2 tables, 10 eps figures; This version matches the published
on
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