The nature of the finite temperature QCD transition as a function of the quark masses

The finite temperature QCD transition for physical quark masses is a crossover. For smaller quark masses a first-order phase transition is expected. Using Symanzik improved gauge and stout improved fermion action for 2+1 flavour staggered QCD we give estimates/bounds for the phase line separating the first-order region from the crossover one. The calculations are carried out on two different lattice spacings. Our conclusion for the critical mass is $m_0 \lesssim 0.07 \cdot m_{phys}$ for $N_T=4$ and $m_0 \lesssim 0.12 \cdot m_{phys}$ for $N_T=6$ lattices.Comment: Talk presented at the XXV International Symposium on Lattice Field Theory, July 30 - August 4 2007, Regensburg, Germany. 7 pages, 6 figure

Calculation of evapotranspiration from potatoes.

Data from sprinkler irrigation experiments with potatoes were used to calculate the actual and potential evapotranspiration from the crop during the growing season, using standard meteorologie data. During the experiments the moisture extraction from the effective root zone was determined by soil sampling. The water-use by the crop for the different periods was also derived from the water balance and both values were in good agreement in periods without extreme conditions of precipitation, this showing that the derived relations between crop height and surface roughness, between soil cover, light intensity, crop characteristics, soil characteristics and diffusion resistance, and between maturation and internal plant resistance were reasonably established. F.s.-A.G.G.H. (Abstract retrieved from CAB Abstracts by CABI’s permission

The equation of state at high temperatures from lattice QCD

We present results for the equation of state upto previously unreachable, high temperatures. Since the temperature range is quite large, a comparison with perturbation theory can be done directly.Comment: 7 pages, 5 figures, Lattice 200

Lattice SU(3) thermodynamics and the onset of perturbative behaviour

We present the equation of state (pressure, trace anomaly, energy density and entropy density) of the SU(3) gauge theory from lattice field theory in an unprecedented precision and temperature range. We control both finite size and cut-off effects. The studied temperature window ($0.7... 1000 T_c$) stretches from the glueball dominated system into the perturbative regime, which allows us to discuss the range of validity of these approaches. From the critical couplings on fine lattices we get T_c/\Lambdamsbar=1.26(7) and use this ratio to express the perturbative free energy in $T_c$ units. We also determine the preferred renormalization scale of the Hard Thermal Loop scheme and we fit the unknown $g^6$ order perturbative coefficient at extreme high temperatures $T>100T_c$. We furthermore quantify the nonperturbative contribution to the trace anomaly using two simple functional forms.Comment: 7 pages, Contribution to the The XXVIII International Symposium on Lattice Field Theory; June 14 - 19, 2010, Villasimius, Sardinia, Ital

Local CP-violation and electric charge separation by magnetic fields from lattice QCD

We study local CP-violation on the lattice by measuring the local correlation between the topological charge density and the electric dipole moment of quarks, induced by a constant external magnetic field. This correlator is found to increase linearly with the external field, with the coefficient of proportionality depending only weakly on temperature. Results are obtained on lattices with various spacings, and are extrapolated to the continuum limit after the renormalization of the observables is carried out. This renormalization utilizes the gradient flow for the quark and gluon fields. Our findings suggest that the strength of local CP-violation in QCD with physical quark masses is about an order of magnitude smaller than a model prediction based on nearly massless quarks in domains of constant gluon backgrounds with topological charge. We also show numerical evidence that the observed local CP-violation correlates with spatially extended electric dipole structures in the QCD vacuum.Comment: 19 pages, 7 figures. Additional lattice results about the induced electric dipole structure, extended model description, specified terminology. Version published in JHE

Determination of Freeze-out Conditions from Lattice QCD Calculations

Freeze-out conditions in Heavy Ion Collisions are generally determined by comparing experimental results for ratios of particle yields with theoretical predictions based on applications of the Hadron Resonance Gas model. We discuss here how this model dependent determination of freeze-out parameters may eventually be replaced by theoretical predictions based on equilibrium QCD thermodynamics.Comment: presented at the International Conference "Critical Point and Onset of Deconfinement - CPOD 2011", Wuhan, November 7-11, 201

Thermal momentum distribution from path integrals with shifted boundary conditions

For a thermal field theory formulated in the grand canonical ensemble, the distribution of the total momentum is an observable characterizing the thermal state. We show that its cumulants are related to thermodynamic potentials. In a relativistic system for instance, the thermal variance of the total momentum is a direct measure of the enthalpy. We relate the generating function of the cumulants to the ratio of (a) a partition function expressed as a Matsubara path integral with shifted boundary conditions in the compact direction, and (b) the ordinary partition function. In this form the generating function is well suited for Monte-Carlo evaluation, and the cumulants can be extracted straightforwardly. We test the method in the SU(3) Yang-Mills theory and obtain the entropy density at three different temperatures.Comment: 4 pages, 1 figure, minor revisions; version accepted in PR

Model analysis of thermal UV-cutoff effects on the chiral critical surface at finite temperature and chemical potential

We study the effects of temporal UV-cutoff on the chiral critical surface in hot and dense QCD using a chiral effective model. Recent lattice QCD simulations indicate that the curvature of the critical surface might change toward the direction in which the first order phase transition becomes stronger on increasing the number of lattice sites. To investigate this effect on the critical surface in an effective model approach, we use the Nambu-Jona-Lasinio model with finite Matsubara frequency summation. We find that qualitative feature of the critical surface does not alter appreciably as we decrease the summation number, which is unlike the case what is observed in the recent lattice QCD studies. This may either suggest the dependence of chemical potential on the coupling strength or due to some additional interacting terms such as vector interactions which could play an important role at finite density.Comment: 7 pages, 8 figure

QCD-Thermodynamics using 5-dim Gravity

We calculate the critical temperature and free energy of the gluon plasma using the dilaton potential arXiv:0911.0627[hep-ph] in the gravity theory of AdS/QCD. The finite temperature observables are calculated in two ways: first, from the Page-Hawking computation of the free energy, and secondly using the Bekenstein-Hawking proportionality of the entropy with the area of the horizon. Renormalization is well defined, because the T=0 theory has asymptotic freedom. We further investigate the change of the critical temperature with the number of flavours induced by the change of the running coupling constant in the quenched theory. The finite temperature behaviour of the speed of sound, spatial string tension and vacuum expectation value of the Polyakov loop follow from the corresponding string theory in AdS_5.Comment: 38 pages, 12 figure

Thermodynamic properties of QCD in external magnetic fields

We consider the effect of strong external electromagnetic fields on thermodynamic observables in QCD, through lattice simulations with 1+1+1 flavors of staggered quarks at physical quark masses. Continuum extrapolated results are presented for the light quark condensates and for their tensor polarizations, as functions of the temperature and the magnetic field. We find the light condensates to undergo inverse magnetic catalysis in the transition region, in a manner that the transition temperature decreases with growing magnetic field. We also compare the results to other approaches and lattice simulations. Furthermore, we relate the tensor polarization to the spin part of the magnetic susceptibility of the QCD vacuum, and show that this contribution is diamagnetic.Comment: 13 pages, 9 figures, talks presented by FB and GE at Xth Quark Confinement and the Hadron Spectrum, 8-12 October 2012, TUM Campus Garching, Munich, German