7 research outputs found
Phases and properties of quark matter
I review recent developments in finite temperature lattice QCD which are
useful for the study of heavy-ion collisions. I pay particular attention to
studies of the equation of state and the light they throw on conformal symmetry
and the large N_c limit, and to the structure of the phase diagram for N_f=2+1.Comment: Plenary talk at Quark Matter 2008, Jaipur, India (8 pages, 5 figures
Lattice QCD equation of state : improving the differential method
We propose an improvement of the differential method for the computation of
the equation of state of QCD from lattice simulations. In contrast to the
earlier differential method our technique yields positive pressure for all
temperatures including in the transition region. Employing it on temporal
lattices of 8, 10 and 12 sites and by extrapolating to zero lattice spacing we
obtained the pressure, energy density, entropy density, specific heat and speed
of sound in quenched QCD for 0.9 < T/Tc < 3. A comparison of our results is
made with those from the dimensional reduction approach and a conformal
symmetric theory at high-temperature.Comment: Version to be published in Pramana. Title modified. Explanatory
material added. Figure 6b redrawn with corrected normalization for the
AdS/CFT lin
Meson screening masses from lattice QCD with two light and the strange quark
We present results for screening masses of mesons built from light and
strange quarks in the temperature range of approximately between 140 MeV to 800
MeV. The lattice computations were performed with 2+1 dynamical light and
strange flavors of improved (p4) staggered fermions along a line of constant
physics defined by a pion mass of about 220 MeV and a kaon mass of 500 MeV. The
lattices had temporal extents Nt = 4, 6 and 8 and aspect ratios of Ns / Nt \geq
4. At least up to a temperature of 140 MeV the pseudo-scalar screening mass
remains almost equal to the corresponding zero temperature pseudo-scalar (pole)
mass. At temperatures around 3Tc (Tc being the transition temperature) the
continuum extrapolated pseudo-scalar screening mass approaches very close to
the free continuum result of 2 \pi T from below. On the other hand, at high
temperatures the vector screening mass turns out to be larger than the free
continuum value of 2 \pi T. The pseudo-scalar and the vector screening masses
do not become degenerate even for a temperature as high as 4Tc. Using these
mesonic spatial correlation functions we have also investigated the restoration
of chiral symmetry and the effective restoration of the axial symmetry. We have
found that the vector and the axial-vector screening correlators become
degenerate, indicating chiral symmetry restoration, at a temperature which is
consistent with the QCD transition temperature obtained in previous studies. On
the other hand, the pseudo-scalar and the scalar screening correlators become
degenerate only at temperatures larger than 1.3Tc, indicating that the
effective restoration of the axial symmetry takes place at a temperature larger
than the QCD transition temperature.Comment: Published versio
QCD Working Group Report
This is the report of the QCD working group at WHEPP 6. Discussions and work
on heavy ion collisions, polarised scattering, and collider phenomenology are
reported.Comment: Report of the QCD group at WHEPP-6, Chennai, January 2000. 7 page