56465034
The chiral and deconfinement crossover transitions: PNJL model beyond mean field ∗
Abstract The Polyakov loop extended Nambu and Jona-Lasinio model (PNJL model) in a mean field framework shows astonishingly good agreement with lattice QCD calculations which needs to be better understood. The present work reports on further developments concerning both Polyakov loop and mesonic fluctuations beyond mean field approximation. Corrections beyond mean field are of special interest for the thermal expectation values of the Polyakov loop 〈 Φ 〉 and its conjugate 〈 Φ ∗ 〉 , which differ once the quark chemical potential is non-zero. Mesonic fluctuations are also considered with emphasis on the role of pionic modes.
119220328
Polyakov Loop and Gluon Quasiparticles in Yang-Mills Thermodynamics
We study the interpretation of lattice data about the thermodynamics of the deconfinement phase of $SU(3)$ Yang-Mills theory, in terms of gluon quasiparticles propagating in a background of a Polyakov loop. A potential for the Polyakov loop, inspired by the strong coupling expansion of the QCD action, is introduced; the Polyakov loop is coupled to transverse gluon quasiparticles by means of a gaslike effective potential. This study is useful to identify the effective degrees of freedom propagating in the gluon medium above the critical temperature. A main general finding is that a dominant part of the phase transition dynamics is accounted for by the Polyakov loop dynamics; hence, the thermodynamics can be described without the need for diverging or exponentially increasing quasiparticle masses as $T\ensuremath{\rightarrow}{T}_{c}$, at variance respect to standard quasiparticle models.
18827525
Thermodynamics of two-color QCD and the Nambu Jona-Lasinio model
We investigate two-flavor and two-color QCD at finite temperature and chemical potential in comparison with a corresponding Nambu and Jona-Lasinio model. By minimizing the thermodynamic potential of the system, we confirm that a second-order phase transition occurs at a value of the chemical potential equal to half the mass of the chiral Goldstone mode. For chemical potentials beyond this value the scalar diquarks undergo Bose condensation and the diquark condensate is nonzero. We evaluate the behavior of the chiral condensate, the diquark condensate, the baryon charge density and the masses of scalar diquark, antidiquark and pion, as functions of the chemical potential. Very good agreement is found with lattice QCD (N{sub c}=2) results. We also compare with a model based on leading-order chiral effective field theory.
16051108
Mesonic correlation functions at finite temperature and density in the Nambu-Jona-Lasinio model with a Polyakov loop
We investigate the properties of scalar and pseudoscalar mesons at finite temperature and quark chemical potential in the framework of the Nambu-Jona-Lasinio (NJL) model coupled to the Polyakov loop (PNJL model) with the aim of taking into account features of both chiral symmetry breaking and deconfinement. The mesonic correlators are obtained by solving the Schwinger-Dyson equation in the RPA approximation with the Hartree (mean field) quark propagator at finite temperature and density. In the phase of broken chiral symmetry, a narrower width for the {sigma} meson is obtained with respect to the NJL case; on the other hand, the pion still behaves as a Goldstone boson. When chiral symmetry is restored, the pion and {sigma} spectral functions tend to merge. The Mott temperature for the pion is also computed.
15445984
Evaporation of the gluon condensate: a model for pure gauge SU(3)c phase transition
Abstract We interpret lattice data for the equation of state of pure gauge SU (3) c by an evaporation model. At low temperatures gluons are frozen inside the gluon condensate, whose dynamics is described in terms of a dilaton Lagrangian. Above the critical temperature quasi-free gluons evaporate from the condensate: a first order transition is obtained by minimizing the thermodynamical potential of the system. Within the model it is possible to reproduce lattice QCD results at finite temperature for thermodynamical quantities such as pressure and energy. The gluonic longitudinal mass can also be evaluated; it vanishes below the critical temperature, where it shows a discontinuity. At very large temperatures we recover the perturbative scenario and gluons are the only asymptotic degrees of freedom.
15026810
Stability of strange quark matter: MIT bag versus color dielectric model
Abstract We discuss the properties of strange matter, in particular the minimum of the energy per baryon number as a function of the strangeness fraction. We utilize both the MIT bag model and the color dielectric model and compare the energy per baryon with the masses of hyperons having the corresponding strangeness fraction, which are coherently calculated within both models. We also take into account the perturbative exchange of gluons. The results obtained in the two approaches allow to discuss the stability of strangelets. While the MIT bag model and the double minimum version of the color dielectric model allow the existence of strangelets, the single minimum version of the color dielectric model excludes this possibility.
118567905
Large spin expansion of the wrapping correction to Freyhult-Rej-Zieme twist operators
Twist operators in the closed $ \mathfrak{s}\mathfrak{l}(2) $ sector of planar $ \mathcal{N} = 4 $ SYM are characterized by their spin. The explicit dependence of anomalous dimensions on this important parameter is a source of interesting information. Wrapping corrections are a non trivial part of the calculation and are under control in the framework of thermodynamical Bethe Ansatz valid for the full theory and thoroughly checked in that sector. The extension to more general twist operators beyond $ \mathfrak{s}\mathfrak{l}(2) $ has been recently accomplished for the so-called 3-gluon operators that are a special case of the generalized twist operators introduced by Freyhult, Rej and Zieme. Such operators are dual to spinning strings configurations with two spins S1, S2 in AdS5 and charge in S5. We compute the expansion of the weak-coupling leading order wrapping correction in the gauge theory limit dual to large S1 and fixed S2. We present a simple algorithm for the calculation and provide explicit results illustrating the general structure of the expansion.
118612335
Wrapping corrections, reciprocity and BFKL beyond the sl(2) subsector in N=4 SYM
We consider N=4 SYM and a class of spin N, length-3, twist operators beyond the well studied sl(2) subsector. They can be identified at one-loop with three gluon operators. At strong coupling, they are associated with spinning strings with two spins in AdS5. We exploit the Y-system to compute the leading weak-coupling four loop wrapping correction to their anomalous dimension. The result is written in closed form as a function of the spin N. We combine the wrapping correction with the known four-loop asymptotic Bethe Ansatz contribution and analyze special limits in the spin N. In particular, at large N, we prove that a generalized Gribov-Lipatov reciprocity holds. At negative unphysical spin, we present a simple BFKL-like equation predicting the rightmost leading poles.
119250353
Leading quantum correction to energy of ‘short’ spiky strings
We consider semiclassical quantization of spiky strings spinning in the AdS3 part of AdS5 × S5 using an integrability-based (algebraic curve) method. In the ‘short-string’ (small-spin) limit the expansion of string energy starts with its flat-space expression. We compute the leading quantum string correction to ‘short’ spiky string energy and find the explicit form of the corresponding one-loop coefficient a01. It turns out to be rational and expressed in terms of the harmonic sums as functions of the number n of spikes. In the special case of n = 2 when the spiky string reduces to the single-folded spinning string, the coefficient a01 takes the value (−1/4) found in Gromov et al (2011 J. High Energy Phys. JHEP08(2011)046). We also consider a similar computation for the m-folded string and more general spiky string with an extra ‘winding’ number, finding similar expressions for a01. These results may be useful for a description of energies of higher excited states in the quantum AdS5 × S5 string spectrum, generalizing earlier discussions of the string counterparts of the Konishi operator.
122501875
On marginally deformed meson spectroscopy
We review the results of 0710.4292 [hep-th] where we study the embedding of spacetime filling D7-branes in β-deformed backgrounds. This corresponds to flavoring β-deformed = 4 super Yang–Mills. For the supersymmetric and the more general non-supersymmetric three parameter deformations, we study quadratic fluctuations of a probe D7-brane wrapped on a deformed three-sphere, which correspond to mesonic configurations of the dual field theory. We manage to solve their equations exactly in the presence of a non-trivial coupling between scalar and vector modes induced by the deformation. We find a mesonic mass spectrum which is discrete, with a mass gap and a Zeeman-like splitting occurs.
15615236
Mesons in marginally deformed AdS/CFT
We study the embedding of spacetime filling D7-branes in β-deformed backgrounds which, according to the AdS/CFT dictionary, corresponds to flavoring β-deformed = 4 super Yang-Mills. We consider supersymmetric and more general non-supersymmetric three parameter deformations. The equations of motion for quadratic fluctuations of a probe D7-brane wrapped on a deformed three-sphere exhibit a non-trivial coupling between scalar and vector modes induced by the deformation. Nevertheless, we manage to solve them analytically and find that the mesonic mass spectrum is discrete, with a mass gap and a Zeeman-like splitting occurs. Finally we propose the action for the dual field theory as obtained by -product deformation of super Yang-Mills with fundamental matter.