Topology, chiral and screening transitions at finite density in two colour QCD

The behaviour of the topological susceptibility in QCD with two colours and 8 flavours of quarks is studied at nonzero temperature on the lattice across the finite density transition. It is shown that its signal drops at a (pseudo-)critical chemical potential mu_c. The Polyakov loop and the chiral condensate undergo their transitions at the same value. Pauli blocking supervenes at a value of the chemical potential larger than mu_c.Comment: Latex file (uses espcrc2.sty), 4 pages, 4 ps figures; talk presented at QCD-06, Montpellier, July 200

Radiatively Induced Breaking of Conformal Symmetry in a Superpotential

Radiatively induced symmetry breaking is considered for a toy model with one scalar and one fermion field unified in a superfield. It is shown that the classical quartic self-interaction of the superfield possesses a quantum infrared singularity. Application of the Coleman-Weinberg mechanism for effective potential leads to the appearance of condensates and masses for both scalar and fermion components. That induces a spontaneous breaking of the initial classical symmetries: the supersymmetry and the conformal one. The energy scales for the scalar and fermion condensates appear to be of the same order, while the renormalization scale is many orders of magnitude higher. A possibility to relate the considered toy model to conformal symmetry breaking in the Standard Model is discussed.Comment: Improved final version with new references and misprints corrected, 9 pages , no figure

Vector spectrum and color screening in two color QCD at nonzero T and \mu

We discuss a few aspects of the phase diagram of two color lattice QCD: we investigate the long distance screening analyzing the behavior of the interquark potential at large distances; we present a first set of results for vector mesons and diquarks; we note similarities and differences between features at high temperature and high baryon density.Comment: 9 pages, 4 figures; talk at the GISELDA Meeting held in Frascati, Italy, 14-18 January 200

Neural endophenotypes of social behaviour in autism spectrum conditions

Autism is characterized by qualitative impairments in social interaction, communication, and stereotyped repetitive behaviors and/or restricted interests. Beyond these diagnostic criteria, autism is viewed as a neurodevelopmental condition with possibly several etiologies that manifest in complex patterns of atypical structural and functional brain development, cognition, and behavior. Despite the multidimensional nature of and substantial variation within the autism spectrum, impairments in social interaction remain among the most visible hallmarks of the condition. It is this profound developmental deficit in the social domain that makes autism a unique case in the field of social neuroscience. This chapter contributes to the dialogue amongst both the fields of autism research and social neuroscience by deliberately taking the stance of asking how we can understand more about the etiological mechanisms underlying social behavior in autism. It presents a multi-level overview of the literature on the behavioral, neural, and genetic underpinnings of social functioning in autism spectrum conditions (ASC). The main objective is to highlight the current state of the field regarding theory of mind/empathy difficulties in ASC, and then to suggest distinct candidate neural endophenotypes that can bridge the gap between social behavior and genetic mechanisms

Screening Effects in Superfluid Nuclear and Neutron Matter within Brueckner Theory

Effects of medium polarization are studied for $^1S_0$ pairing in neutron and nuclear matter. The screening potential is calculated in the RPA limit, suitably renormalized to cure the low density mechanical instability of nuclear matter. The selfenergy corrections are consistently included resulting in a strong depletion of the Fermi surface. All medium effects are calculated based on the Brueckner theory. The $^1S_0$ gap is determined from the generalized gap equation. The selfenergy corrections always lead to a quenching of the gap, which is enhanced by the screening effect of the pairing potential in neutron matter, whereas it is almost completely compensated by the antiscreening effect in nuclear matter.Comment: 8 pages, 6 Postscript figure

Charge without charge, regular spherically symmetric solutions and the Einstein-Born-Infeld theory

The aim of this paper is to continue the research of JMP 46, 042501 (2005) of regular static spherically symmetric spacetimes in Einstein-Born-Infeld theories from the point of view of the spacetime geometry and the electromagnetic structure. The energy conditions, geodesic completeness and the main features of the horizons of this spacetime are explicitly shown. A new static spherically symmetric dyonic solution in Einstein-Born-Infeld theory with similar good properties as in the regular pure electric and magnetic cases of our previous work, is presented and analyzed. Also, the circumvention of a version of "no go" theorem claiming the non existence of regular electric black holes and other electromagnetic static spherically configurations with regular center is explained by dealing with a more general statement of the problem.Comment: Figures in Int J Theor Phys (Online First

The nature of the continuum limit in strongly coupled quenched QED

We review the results of large scale simulations of noncompact quenched $QED$ which use spectrum and Equation of State calculations to determine the theory's phase diagram, critical indices, and continuum limit. The resulting anomalous dimensions are in good agreement with Schwinger-Dyson solutions of the ladder graphs of conventional $QED$ and they satisfy the hyperscaling relations expected of a relativistic renormalizable field theory. The spectroscopy results satisfy the constraints of the Goldstone mechanism and PCAC, and may be indicative of Technicolor versions of the Standard Model which are strongly coupled at short distances.Comment: (talk given at the XXVI ICHEP, Dallas, TX, Aug 6-12 92), 6 pp., ILL-(TH)-92-#2

SU(2) Glueballs, diquarks and mesons in dense matter

We present preliminary results from a high statistics study of 2-color QCD at low temperature and non-zero baryon density. The simulations are carried out on a 6^3*12 lattice and use a standard hybrid molecular dynamics algorithm for staggered fermions for two values of quark mass. Observables include glueball correlators evaluated via a multi-step smearing procedure as well as scalar and vector mesons and diquarks.Comment: Poster presented at Lattice 2003 (Non zero temperature and density), 3 pages, 4 figure

Glueballs and mesons in the superfluid phase of two-color QCD

QCD with two colors undergoes a transition to a superfluid phase with diquark condensate when the quark chemical potential equals half the pion mass. We investigate the gluonic aspects of the transition by inspecting the behavior of the glueball correlators evaluated via a multi-step smearing procedure for several values of chemical potential ranging between zero and the saturation threshold. The results are based on an analysis of 0++ glueball correlators, on a sample of 40000 independent configurations on each parameter set. The amplitudes of the correlators peak for \mu = m_\pi/2,indicating that the superfluid phase transition affects the gluonic sector as well. The mass of the fundamental state decreases in the superfluid phase, and the amplitude of the propagators drops, suggesting a reduction of the gluon condensate, in agreement with model calculations. The analysis of the smearing dependence of the results helps disentangling the role of long and short distance phenomena at the superfluid transition.Comment: 7 pages, 5 figures, talk presented at the XXV International Symposium on Lattice Field Theory, July 30 - August 4, 2007, Regensburg,German