37 research outputs found
Spectral functions of charmonium with 2+1 flavours of dynamical quarks
Finite temperature charmonium spectral functions in the pseudoscalar(PS) and
vector(V) channels are studied in lattice QCD with 2+1 flavours of dynamical
Wilson quarks, on fine isotropic lattices (with a lattice spacing of 0.057fm),
with a non-physical pion mass of 545MeV. The highest temperature studied is
approximately 1.4Tc. Up to this temperature no significant variation of the
spectral function is seen in the PS channel. The V channel shows some
temperature dependence, which seems to be consistent with a temperature
dependent low frequency peak related to heavy quark transport, plus a
temperature independent term at omega > 0. These results are in accord with
previous calculations using the quenched approximation.Comment: Conference proceedings: The 32nd International Symposium on Lattice
Field Theory - Lattice 2014 June 23-28, 2014 Columbia University, New York,
New York This conference contribution draws heavily from the paper:
arXiv:1401.5940 [hep-lat
Geometry of W-algebras from the affine Lie algebra point of view
To classify the classical field theories with W-symmetry one has to classify
the symplectic leaves of the corresponding W-algebra, which are the
intersection of the defining constraint and the coadjoint orbit of the affine
Lie algebra if the W-algebra in question is obtained by reducing a WZNW model.
The fields that survive the reduction will obey non-linear Poisson bracket (or
commutator) relations in general. For example the Toda models are well-known
theories which possess such a non-linear W-symmetry and many features of these
models can only be understood if one investigates the reduction procedure. In
this paper we analyze the SL(n,R) case from which the so-called W_n-algebras
can be obtained. One advantage of the reduction viewpoint is that it gives a
constructive way to classify the symplectic leaves of the W-algebra which we
had done in the n=2 case which will correspond to the coadjoint orbits of the
Virasoro algebra and for n=3 which case gives rise to the Zamolodchikov
algebra. Our method in principle is capable of constructing explicit
representatives on each leaf. Another attractive feature of this approach is
the fact that the global nature of the W-transformations can be explicitly
described. The reduction method also enables one to determine the ``classical
highest weight (h. w.) states'' which are the stable minima of the energy on a
W-leaf. These are important as only to those leaves can a highest weight
representation space of the W-algebra be associated which contains a
``classical h. w. state''.Comment: 17 pages, LaTeX, revised 1. and 7. chapter
Spectral functions of charmonium with 2+1 flavours of dynamical quarks
Finite temperature charmonium spectral functions in the
pseudoscalar(PS) and vector(V) channels are studied in lattice
QCD with 2+1 flavours of dynamical Wilson quarks, on fine
isotropic lattices (with a lattice spacing of 0.057fm), with a
non-physical pion mass of 545MeV. The highest temperature
studied is approximately 1.4Tc. Up to this temperature no
significant variation of the spectral function is seen in the PS
channel. The V channel shows some temperature dependence, which
seems to be consistent with a temperature dependent low
frequency peak related to heavy quark transport, plus a
temperature independent term at omega > 0. These results are in
accord with previous calculations using the quenched
approximation
More Results on Finite Temperature QCD with Wilson Fermions
We investigate 2 + 1 flavour QCD thermodynamics using dynamical Wilson fermions in thefixed scale approach. Our previous study at a pion mass of 545 MeV is extended with twoadditional pion masses, approximately 440 MeV and 280 MeV. We perform simulations using3 or 4 lattice spacings at each fixed pion mass and measure the renormalised chiral condensate,strange quark number susceptibility and Polyakov loop as a function of the temperature. Weobserve a decrease in the light chiral pseudo-critical temperature as the pion mass is loweredwhile the pseudo-critical temperature associated with the strange quark number susceptibilityor the Polyakov loop is only mildly sensitive to the pion mass. These findings are in agreementwith previous results obtained in the staggered formulation
Lattice QCD as a video game
The speed, bandwidth and cost characteristics of today’s PC graphics cards make them an attractive target as general purpose computational platforms. High performance can be achieved also for lattice simulations but the actual implementation can be cumbersome. This paper outlines the architecture and programming model of modern graphics cards for the lattice practitioner with the goal of exploiting these chips for Monte Carlo simulations. Sample code is also given.