Melting of scalar mesons and black-hole quasinormal modes in a holographic QCD model

A holographic model for QCD is employed to investigate the effects of the gluon condensate on the spectrum and melting of scalar mesons. We find the evolution of the free energy density with the temperature, and the result shows that the temperature of the confinement/deconfinement transition is sensitive to the gluon-condensate parameter. The spectral functions (SPFs) are also obtained and show a series of peaks in the low-temperature regime, indicating the presence of quasiparticle states associated to the mesons, while the number of peaks decreases with the increment of the temperature, characterizing the quasiparticle melting. In the dual gravitational description, the scalar mesons are identified with the black-hole quasinormal modes (QNMs). We obtain the spectrum of QNMs and the dispersion relations corresponding to the scalar-field perturbations of the gravitational background, and find their dependence with the gluon-condensate parameter.Comment: 30 pages, 12 figures, 5 table

Vector meson quasinormal modes in a finite-temperature AdS/QCD model

We study the spectrum of vector mesons in a finite temperature plasma. The plasma is holographically described by a black hole AdS/QCD model. We compute the boundary retarded Green's function using AdS/CFT prescriptions. The corresponding thermal spectral functions show quasiparticle peaks at low temperatures. Then we calculate the quasinormal modes of vector mesons in the soft-wall black hole geometry and analyse their temperature and momentum dependences.Comment: 27 pages, 9 figure

Melting of heavy vector mesons and quasinormal modes in a finite density plasma from holography

In this work, we investigate the melting of charmonium states within a holographic QCD model in the context of Einstein-Maxwell-Dilaton (EMD) theory. In the dual field theory, the model describes the heavy mesons inside a finite temperature and density medium. First, we calculate the spectrum at zero temperature. Then, at finite temperature, we obtain the spectral functions, where the heavy vector meson are represented by peaks. We show that the charmonium melts down at temperatures above the confinement/deconfinement temperature of the quark-gluon plasma. We also observe that the chemical potential speeds up the melting process. This finding is in agreement with results previously reported in the literature. In the gravitational side of the theory, we solve the perturbation equations in the hydrodynamics limit. From this result, we read off the diffusion coefficient by comparing the dispersion relation against the corresponding result obtained in the dual field theory. We also investigate the behavior of the diffusion coefficient as a function of the temperature. The perturbation equations are solved numerically, in order to get the quasinormal frequencies. We report the emergence of a new mode whose real part increases rapidly at a certain value of the chemical potential while its imaginary part decreases with the increasing of the chemical potential. Finally, by comparing against results obtained in the conformal plasma, we observe that the real part of the frequency increases, while the imaginary part decreases when we consider the non-conformal plasma.Comment: 39 pages, 15 figures, 5 table

A dynamical holographic QCD model for spontaneous chiral symmetry breaking and confinement

In this paper, we present a holographic realization of spontaneous chiral symmetry breaking and confinement. The latter is realized by building a solution of 5d Einstein-dilaton gravity leading to a confining quark antiquark potential. The 4d currents and the quark mass operator associated with chiral symmetry breaking and creation of meson states are mapped to 5d fields whose dynamics is given by a non-Abelian Higgs action. We introduce a non-minimal dilaton coupling to the tachyon potential which has two parameters, one of them controlling the presence or absence of spontaneous chiral symmetry breaking and the other controlling the sign of the chiral condensate as the quark mass grows. We calculate the masses of vector, scalar, axial-vector and pseudoscalar mesons, focusing on the effect of chiral symmetry breaking on the spectrum. In the chiral limit we identify the emergence of a massless state in the pseudoscalar meson spectrum, i.e., the pion. We calculate all meson decay constants and confirm that the pion satisfies the Gell-Mann-Oakes relation in the light quark regime.Comment: 36 pages, 20 figure

Reflexiones en torno a la relación de los arqueólogos y bioarqueólogos con las comunidades indígenas: el caso Hornillos (Qda. de Humahuaca, Jujuy)

Este trabajo tiene por finalidad reflexionar en torno al trabajo realizado con las comunidades indígenas a partir de la exhumación de un conjunto de restos humanos prehispánicos (PDR II-1350-1460 d.C.). El conjunto que se compone de un entierro múltiple, uno simple y dos en urna; fueron rescatados del yacimiento arqueológico de Hornillos en el marco del Proyecto "Puesta en Valor del Patrimonio Cultural de Hornillos". Considerando que los entierros humanos en su conjunto son parte de la historia y del patrimonio de los pueblos, el análisis bioarqueológico no debería circunscribirse al mero análisis de los restos óseos sino que tendría que contemplar e involucrar de alguna manera la participación de diferentes actores sociales, en este caso, las comunidades indígenas. Los restos óseos humanos han despertado siempre gran interés por parte de los diferentes actores sociales (arqueólogos, coleccionistas, comunidad en general). En este caso se pudo generar un espacio de reflexión sobre el destino de los restos óseos humanos en el que participaron aquellas personas interesadas en la temática. A partir de la consulta de las partes intervinientes se decidió que los restos óseos recuperados fueran primeramente analizados por los arqueólogos y bioarqueólogos, para luego ser enterrados nuevamente en el lugar de origen de acuerdo a las costumbres y creencias de las comunidades indígenas.Asociación de Antropología Biológica de la República Argentin