Entropy Production During Hadronization of a Quark-Gluon Plasma

We revisit the physical pictures for the hadronization of quark-gluon plasma, concentrating on the problem of entropy production during processes where the number of degrees of freedom is seemingly reduced due to color confinement. Based on observations on Regge trajectories we propose not having an infinite tower of hadronic resonances. We discuss possible entropy production mechanisms far from equilibrium in terms of stochastic dynamics.Comment: Submitted to EPJ A Topical Issue on "Frontiers in nuclear, heavy ion and strong field physics", in memoriam Walter Greine

Illusory Flow in Radiation from Accelerating Charge

In this paper we analyze the classical electromagnetic radiation of an accelerating point charge moving on a straight line trajectory. Depending on the duration of accelerations, rapidity distributions of photons emerge, resembling the ones obtained in the framework of hydrodynamical models by Landau or Bjorken. Detectable differences between our approach and spectra obtained from hydrodynamical models occur at high transverse momenta and are due to interference

Dinamikus kvarkok és a topológikus töltés vizsgálata rácson = Dynamical quarks and the topological charge on the lattice

Kimutattuk, hogy magas hőmérsékleten az egyébként ekvivalens Polyakov hurok Z(N) szektorok közötti különbségért a Dirac operátor legalacsonyabb sajátértékei felelősek. A QCD magas hőmérsékletű fázisában vizsgáltuk a kvark spektrum alacsonyan fekvő állapotainak statisztikáját. Arra a meglepő következtetésre jutottunk, hogy a magas hőmérsékletű fázisban a Dirac operátor kis sajátértékei korrelálatlanok. Ezzel a kvark spektrum olyan egyszerű, jól használható leírását adtuk meg, amely új fejezetet nyithat a QCD magas hőmérsékletű fázisának vizsgálatában. Elsőként mutattuk ki a QCD alapelveiből kiindulva, hogy a Jaffe és Wilczek által javasolt dikvark-dikvark-antikvark hullámfüggvényű pentakvark állapotok létezése nagy valószínűséggel kizárható. Eredményünk összangban áll a későbbi, nagyobb statisztikájú kísérleti eredményekkel. Igazoltuk, hogy a szokásos Monte Carlo algoritmusok módosításával lehetőség nyílik a nagyenergiás nehézion ütközésekben feltételezett Tsallis eloszláson alapuló termodinamika rács szimulációjára. Sikerült kimutatnunk, hogy ebben az esetben is van a bezáró és nem bezáró fázis közötti átmenet. A Casimir a energia vizsgálatára fejlesztett módszerünket a dobozba zárt szabad skalártér esetén teszteltük, és megmutattuk, hogy zérus tömegű terekre periodikus határfeltételek esetén a rácstérelméleti szimuláció az analitikus számolásokkal kvalitatív összhangban van. | We showed that in the high temperature phase of QCD the difference between the path integral weight of different Polyakov loop sectors is mostly due to the low eigenvalues of the Dirac operator. We also looked at the statistics of low-lying eigenvalues of the Dirac operator and found that they are essentially uncorrelated. The resulting simple and convenient description of the spectrum can open the way to new advances in the study of strongly interacting matter at high temperatures. Starting from the basic principles of QCD we ruled out the existence of pentaquark states with the diquark-diquark-antiquark wave function proposed by Jaffe and Wilczek. We developed a Monte Carlo algorithm to study the thermodynamics of strongly interacting matter based on the unconventional Tsallis distribution. We showed the existence of a deconfinement transition in this framework. We developed a method to study the Casimir energy on the lattice. In the case of the massless free scalar field with periodic boundary condition our methods yields qualitative agreement with analytic computations

Identifying monopoles on a lattice

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Non-Extensive Entropic Distance Based on Diffusion: Restrictions on Parameters in Entropy Formulae

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Monopoles and instantons in SU(2) lattice gauge theory

We investigate the monopole-instanton correlation in SU(2) lattice gauge theory using a renormalisation group inspired smoothing technique. We look at the properties of monopole clusters and their correlation with instantons. Since the action of the smoothed configurations is dominated by instantons we compare the smoothed Monte Carlo lattices to artificially reconstructed configurations with the same instanton content but no other fluctuations. Both parallel and randomly rotated (in group space) instanton ensembles are considered.Comment: LATTICE98(confine

Some remarks on Abelian dominance

We use a renormalisation group based smoothing to address two questions related to Abelian dominance. Smoothing enables us to extract the Abelian heavy-quark potential from time-like Wilson loops on Polyakov gauge projected configurations. We obtained a very small string tension which is inconsistent with the string tension extracted from Polyakov loop correlators. This shows that the Polyakov gauge projected Abelian configurations do not have a consistent physical meaning. We also apply the smoothing on SU(2) configurations to test how sensitive Abelian dominance in the maximal Abelian gauge is to the short distance fluctuations. We find that on smoothed SU(2) configurations the Abelian string tension was about 30% smaller than the SU(2) string tension which was unaffected by smoothing. This suggests that the approximate Abelian dominance found with the Wilson action is probably an accident and it has no fundamental physical relevance.Comment: 3 pages, LaTeX, 1 figure, uses espcrc2.sty, Talk given at LATTICE9

Topology on the lattice; 2d Yang-Mills theories with a theta term

We study two-dimensional U($N$) and SU($N$) gauge theories with a topological term on arbitrary surfaces. Starting from a lattice formulation we derive the continuum limit of the action which turns out to be a generalisation of the heat kernel in the presence of a topological term. In the continuum limit we can reconstruct the topological information encoded in the theta term. In the topologically trivial cases the theta term gives only a trivial shift to the ground state energy but in the topologically nontrivial ones it remains to be coupled to the dynamics in the continuum. In particular for the U($N$) gauge group on orientable surfaces it gives rise to a phase transition at $\theta= \pi$, similar to the ones observed in other models. Using the equivalence of 2d QCD and a 1d fermion gas on a circle we rewrite our result in the fermionic language and show that the theta term can be also interpreted as an external magnetic field imposed on the fermions.Comment: 19 pages LaTe

Power-law tailed spectra from equilibrium

We propose that power-law tailed hadron spectra may be viewed as stemming from a matter in an unconventional equilibrium state typical for non-extensive thermodynamics. A non-extensive Boltzmann equation, which is able to form such spectra as a stationary solution, is utilized as a rough model of quark matter hadronization. Basic ideas about non-extensive simulation of the QCD equation of state on the lattice are presented.Comment: Talk given at QM2005, Budapest, uses espcrc1.st

Remarks on abelian dominance

We used a renormalisation group based smoothing to address two questions related to abelian dominance. Smoothing drastically reduces short distance fluctuations but it preserves the long distance physical properties of the SU(2) configurations. This enabled us to extract the abelian heavy-quark potential from time-like Wilson loops on Polyakov gauge projected configurations. We obtained a very small string tension which is inconsistent with the string tension extracted from Polyakov loop correlators. This shows that the Polyakov gauge projected abelian configurations do not have a consistent physical meaning. We also applied the smoothing on SU(2) configurations to test how sensitive abelian dominance in the maximal abelian gauge is to the short distance fluctuations. We found that on smoothed SU(2) configurations the abelian string tension was about 30% smaller than the SU(2) string tension which was unaffected by smoothing. This suggests that the approximate abelian dominance found with the Wilson action is probably an accident and it has no fundamental physical relevance.Comment: 13 pages, LaTeX, 3 eps figure