arXiv subjects
Publications and source records attributed to Agnes Mocsy.
We study the quarkonia correlators above deconfinement using the potential model with screened temperature-dependent potentials. We find that while the qualitative features of the spectral functions, such as the survival of the 1S state, can be reproduced by potential models, the temperature dependence of the correlators disagree with the recent lattice data.
We compare the quarkonia correlators from potential models and from lattice QCD.
We discuss different aspects of the quark mass dependence of the chiral and deconfinement transitions. We make predictions for locating the deconfining critical point, by analyzing the $m_q$ dependence of the ratio of imaginary and real mass of the Polyakov loop. We then present an effective theory that allows the extraction of coupling constants from available lattice data for the temperature dependence of the chiral and Polyakov loop condensates at different quark masses.
We investigate the quarkonia correlators in QCD with no light quarks within a potential model with different screened potentials. Our results for the temperature dependence of the charmonium and bottomonium correlators are qualitatively consistent with existing and preliminary lattice results. We identify however, a much reacher structure in the correlators than the one seen on the lattice.
We construct an effective Lagrangian which illustrates why color deconfines when chiral symmetry is restored in hot gauge theories with quarks in the fundamental representation. For quarks in the adjoint representation we show that while deconfinement and the chiral transition do not need to coincide, entanglement between them is still present. Extension to the chemical potential driven transition is discussed.
Effective Lagrangians for Quantum Chromodynamics (QCD) especially suited for understanding deconfinement and chiral symmetry restoration at nonzero temperature and matter density are reviewed. These effective theories allow one to study generic properties of phase transitions using non-order parameter fields without loosing the information encoded in the true order parameter. {}For the pure gauge theory we demonstrate that, near the deconfining phase transition, the center group symmetry is naturally linked to the conformal anomaly. Another relevant outcome is that when the theory contains also quarks we can explain the intertwining of chiral symmetry restoration and deconfinement for QCD with matter fields either in the fundamental or in the adjoint representation of the gauge group. As a test of our general approach we show our results to be applicable also at non zero baryon chemical potential. We also predict new testable substructures to be present in the phase diagram of quarks in the adjoint representation of the gauge group. Here we provide some new insights on the large $N$ limit of gauge theories by investigating the hadronic world. We propose that the world of infinite $N$ should already be well described when N=6 for QCD with two and three light flavors. Finally, we suggest possible future applications of our results for heavy ions collisions.
The Polyakov loop is the appropriate deconfinement order parameter for Yang-Mills theories without quarks or with quarks in the adjoint representation of the gauge group. However it is not a physical state of the theory so the information regarding the center group symmetry must be transferred to the physical states. We briefly review how this transfer of information takes place. When adding quarks the center group is no longer a symmetry for matter in the fundamental representation. This feature allows us to explain why color deconfines when chiral symmetry is restored in hot gauge theories with massless quarks. For quarks in the adjoint representation we show that while deconfinement and the chiral transition do not coincide, entanglement between them is still present. Finally, we discuss also the chemical potential driven phase transition.
The critical behavior of non-order parameter fields is discussed. We show that relevant features of the deconfining phase transition can be determined by monitoring universal properties induced by the order parameter on the physical excitations. Some of the behaviors we uncover are already supported by lattice results.
We propose a general strategy to determine universal properties induced by a nearby phase transition on a non-order parameter field. A general renormalizable Lagrangian is used, which contains the order parameter and a non-order parameter field, and respects all the symmetries present. We investigate the case in which the order parameter field depends only on space coordinates and the case in which this field is also time dependent. We find that the spatial correlators of the non-order parameter field, in both cases, are infrared dominated and can be used to determine properties of the phase transition. We predict a universal behavior for the screening mass of a generic singlet field, and show how to extract relevant information from such a quantity. We also demonstrate that the pole mass of the non-order parameter field is not infrared sensitive. Our results can be applied to any continuous phase transition. As an example we consider the deconfining transition in pure Yang-Mills theory, and show that our findings are supported by lattice data. Our analysis suggests that monitoring the spatial correlators of different hadron species, more specifically the derivatives of these, provides an efficient and sufficient way to experimentally uncover the deconfining phase transition and its features.
We show that all of the relevant features of a phase transition can be determined using a non order parameter field which is a physical state of the theory. This fact allows us to understand the deconfining transition of the pure Yang-Mills theory via the physical excitations rather than using the Polyakov loop.
We set up a framework for field theoretical studies of systems out of thermal equilibrium and zoom in on the dissipation of disoriented chiral condensates. Short relaxation times are obtained in the phase transition region, jeopardizing the definiteness of a DCC signal.
A simple and consistent real time analysis of the long-wavelength chiral condensate fields in the background of hard thermal modes is presented in the framework of the linear sigma model. Effective evolution equations are derived for the inhomogeneous condensate fields coupled to a heat bath. Multiple effects of the thermal background on the disoriented chiral condensate are studied using linear response theory. We determine the temperature dependence of the equilibrium condensate, and examine the modification of the sigma and pion dispersion relations as these mesons traverse a hot medium. We calculate the widths by determining the dissipative coefficients at nonzero temperature at one- and two-loop order with resummed meson masses. Our results show that not only decay processes, but elastic scattering processes are significant at high temperatures, yielding to short relaxation times in the phase transition region. The relaxation times obtained are shorter than in previous estimates, making the observation of DCC signals questionable. Throughout this work Goldstone's Theorem is fulfilled when chiral symmetry is spontaneously broken.
The number of hydrogen-like atoms produced when heavy nuclei collide is estimated for central collisions at the Relativistic Heavy Ion Collider using the sudden approximation of Baym et al. As first suggested by Schwartz, a simultaneous measurement of the hydrogen and hadron spectra will allow an inference of the electron or muon spectra at low momentum where a direct experimental measurement is not feasible.