Clan structure analysis and new physics signals in pp collisions at LHC

The study of possible new physics signals in global event properties in pp collisions in full phase space and in rapidity intervals accessible at LHC is presented. The main characteristic is the presence of an elbow structure in final charged particle MD's in addition to the shoulder observed at lower c.m. energies.Comment: 9 pages, talk given at Focus on Multiplicity (Bari, Italy, June 2004

Magnetic field induced non-Fermi liquid to Fermi liquid crossover at the quantum critical point of YbCu5−x_{5-x}Aux_{x}

The temperature (T) dependence of the muon and $^{63}$Cu nuclear spin-lattice relaxation rates $1/T_1$ in YbCu4.4Au0.6 is reported over nearly four decades. It is shown that for $T\to 0$ $1/T_1$ diverges following the behaviour predicted by the self-consistent renormalization (SCR) theory developed by Moriya for a ferromagnetic quantum critical point. On the other hand, the static uniform susceptibility $\chi_s$ is observed to diverge as $T^{-2/3}$ and $1/T_1T\propto \chi_s^2$, a behaviour which is not accounted for by SCR theory. The application of a magnetic field $H$ is observed to induce a crossover to a Fermi liquid behaviour and for $T\to 0$ $1/T_1$ is found to obey the scaling law $1/T_1(H)= 1/T_1(0)[1+(\mu_BH/k_BT)^2]^{-1}$.Comment: 4 pages, 4 figure

Scenarios for multiplicity distributions in pp collisions in the TeV energy region

Possible scenarios based on available experimental data and phenomenological knowledge of the GeV energy region are extended to the TeV energy region in the framework of the weighted superposition mechanism of soft and semi-hard events. KNO scaling violations, forward-backward multiplicity correlations, Hq vs. q oscillations and shoulder structures are discussed.Comment: 10 pages, 10 figures, talk given at "Focus on Multiplicity" (Bari, Italy, June 2004

Gorkov equations for a pseudo-gapped high temperature superconductor

A theory of superconductivity based on the two-body Cooperon propagator is presented. This theory takes the form of a modified Gorkov equation for the Green's function and allows one to model the effect of local superconducting correlations and long range phase fluctuations on the spectral properties of high temperature superconductors, both above and below Tc. A model is proposed for the Cooperon propagator, which provides a simple physical picture of the pseudo-gap phenomenon, as well as new insights into the doping dependence of the spectral properties. Numerical calculations of the density of states and spectral functions based on this model are also presented, and compared with the experimental STM and ARPES data. It is found, in particular, that the sharpness of the peaks in the density of states is related to the strength and the range of the superconducting correlations and that the apparent pseudo-gap in STM and ARPES can be different, although the underlying model is the same.Comment: REVTEX 3.1, 8 pages, 5 EPS figures, submitted to Phys. Rev.

Bianchi type I universes with dilaton and magnetic fields

We consider the dynamics of a Bianchi type I spacetime in the presence of dilaton and magnetic fields. The general solution of the Einstein-Maxwell dilaton field equations can be obtained in an exact parametric form. Depending on the numerical values of the parameters of the model there are three distinct classes of solutions. The time evolution of the mean anisotropy, shear and deceleration parameter is considered in detail and it is shown that a magnetic-dilaton anisotropic Bianchi type I geometry does not isotropize, the initial anisotropy being present in the universe for all times.Comment: 10 pages, 4 figure

Possible scenarios for soft and semi-hard components structure in central hadron-hadron collisions in the TeV region

Possible scenarios in hh collisions in the TeV regions are discussed in full phase space. It is shown that at such high energies one should expect strong KNO scaling violation and a ln(s) increase of the average charged multiplicity of the semi-hard component, resulting in a huge mini-jet production.Comment: 20 pages, 9 PS figures included, LaTeX2e with AMSmath, epsfi

Diffuse radio emission from the Intracluster medium

An important aspect of the radio emission from galaxy clusters is represented by the diffuse radio sources associated with the intracluster medium: radio halos, relics and mini-halos. The radio halos and relics are indicators of cluster mergers, whereas mini-halos are detected at the center of cooling core clusters. SKA will dramatically improve the knowledge of these sources, thanks to the detection of new objects, and to detailed studies of their spectra and polarized emission. SKA will also provide the opportunity to investigate the presence of halos produced by radiation scattered by a powerful radio galaxy at the cluster centers.Comment: 8 pages, 6 figures, to appear in: "Science with the Square Kilometer Array", eds. C. Carilli & S. Rawlings, New Astronomy Reviews, (Elsevier, Amsterdam

e-EVN monitoring of M87

M87 is a privileged laboratory for a detailed study of the properties of jets, owing to its proximity (D=16.7 Mpc, 1 mas = 0.080 pc), its massive black hole (~6.0 x 10^9M) and its conspicuous emission at radio wavelengths and above. We started on November 2009 a monitoring program with the e-EVN at 5 GHz, in correspondence of the season of Very High Energy (VHE) observations. Indeed, two episodes of VHE activity have been reported in February and April 2010. We present here the main results of these multi-epoch observations: the inner jet and HST-1 are both detected and resolved in our datasets. We study the apparent velocity of HST-1, which seems to be increasing since 2005, and the flux density variability in the inner jet. All in all, the radio counterpart to this year’s VHE event seems to be different from the ones in 2005 and 2008, opening new scenario for the radio-high energy connection

The Jet in M87 from e-EVN Observations

One of the most intriguing open questions of today's astrophysics is the one concerning the location and the mechanisms for the production of MeV, GeV, and TeV gamma-rays in AGN jets. M87 is a privileged laboratory for a detailed study of the properties of jets, owing to its proximity, its massive black hole, and its conspicuous emission at radio wavelengths and above. We started on November 2009 a monitoring program with the e-EVN at 5 GHz, during which two episodes of activity at energy E > 100 GeV have occured. We present here results of these multi-epoch observations. The inner jet and HST-1 are both detected and resolved in our datasets. One of these observations was obtained at the same day of the first high energy flare. A clear change in the proper motion velocity of HST-1 is present at the epoch ~2005.5. In the time range 2003 -- 2005.5 the apparent velocity is subluminal, and superluminal (~ 2.7c) after 2005.5.Comment: Proceedings of the Workshop "Fermi meets Jansky - AGN in Radio and Gamma-Rays", Savolainen, T., Ros, E., Porcas, R.W. & Zensus, J.A. (eds.), MPIfR, Bonn, June 21-23 2010. 4 pages 4 figure

Fluid phonons and inflaton quanta at the protoinflationary transition

Quantum and thermal fluctuations of an irrotational fluid are studied across the transition regime connecting a protoinflationary phase of decelerated expansion to an accelerated epoch driven by a single inflaton field. The protoinflationary inhomogeneities are suppressed when the transition to the slow roll phase occurs sharply over space-like hypersurfaces of constant energy density. If the transition is delayed, the interaction of the quasi-normal modes related, asymptotically, to fluid phonons and inflaton quanta leads to an enhancement of curvature perturbations. It is shown that the dynamics of the fluctuations across the protoinflationary boundaries is determined by the monotonicity properties of the pump fields controlling the energy transfer between the background geometry and the quasi-normal modes of the fluctuations. After corroborating the analytical arguments with explicit numerical examples, general lessons are drawn on the classification of the protoinflationary transition.Comment: 30 pages, 3 figure