Signals of new physics in global event properties in pp collisions in the TeV energy domain: rapidity intervals

The study of possible new physics signals in global event properties in pp collisions in the TeV energy domain is extended from full phase-space to rapidity intervals experimentally accessible at LHC. The elbow structure in the total multiplicity distribution predicted in full phase-space is clearly present also in restricted rapidity intervals, leading to very strong charged particle correlations. It is also found that energy densities comparable to those reached in heavy ion collisions at RHIC could be attained in pp collisions at LHC.Comment: 10 pages, 4 figure

On Statistical Mechanics Developments of Clan Concept in Multiparticle Production

Clan concept has been introduced in multiparticle dynamics in order to interpret the wide occurrence of negative binomial (NB) regularity in n-charged particle multiplicity distributions (MDs) in various high energy collisions. The centrality of clan concept led to the attempt to justify its occurrence within a statistical model of clan formation and evolution. In this framework all thermodynamical potentials have been explicitly calculated in terms of NB parameters. Interestingly it was found that NB parameter k corresponds to the one particle canonical partition function. The goal of this paper is to explore a possible temperature and volume dependence of parameter k in various classes of events in high energy hadron-hadron collisions. It is shown that the existence of a phase transition at parton level from the ideal clan gas associated to the semihard component with k>1 to the ideal clan gas of the hard component with k<1 implies a discontinuity in the average number of particles at hadron level.Comment: 20 pages, latex, no figures; v2: the description of the framework has been considerably expanded, and the main body has been reorganized for clarit

B2 1144+35B, a giant low power radio galaxy with superluminal motion. Orientation and evidence for recurrent activity

The goal of this work is a detailed study of the nearby, low power radio galaxy B2 1144+35B. For this purpose, we performed new Very Long Baseline Array (VLBA) and Very Large Array (VLA) observations. This source has several properties (bright, nearby, large range of spatial structures, visible counterjet, etc.) that make it an excellent astrophysical laboratory for the study of the evolution of radio jets. Here we report the detection of motion in the counterjet at 0.23 $\pm$ 0.07 c, which allows us to estimate the orientation of the parsec-scale jet at 33$^\circ \pm 7^\circ$ from the line of sight, with an intrinsic velocity of (0.94$^{+0.06}_{-0.11}$)c. We also report on a brightening of the core at high frequencies which we suggest could be the result of a new component emerging from the core. High dynamic range VLBA observations at 5 GHz reveal, for the first time, extended emission connecting the core with the bright complex of emission that dominates the flux density of the parsec scale structure at frequencies below 20 GHz. The evolution of this bright complex is considered and its slow decline in flux density is interpreted as the result of an interaction with the interstellar medium of the host galaxy.Comment: 7 pages, 6 b&w figures. A&A in pres

Post-inflationary phases stiffer than radiation and Palatini formulation

If the inflaton and the quintessence fields are identified, the background geometry evolves through a stiff epoch undershooting the expansion rate of a radiation-dominated plasma. For some classes of inflationary potentials this scenario is at odds with the current observational evidence since the corresponding tensor-to-scalar ratio is too large. Quintessential inflation is analyzed when the gravitational action is supplemented by a contribution quadratic in the Einstein-Hilbert term. In the Palatini formulation the addition such a term does not affect the scalar modes during the inflationary phase and throughout the course of the subsequent stiff epoch but it suppresses the tensor power spectrum and the tensor-to-scalar ratio. While in the Palatini formulation the power-law potentials leading to a quintessential inflationary dynamics are again viable, the high-frequency spike of the relic graviton spectrum is squeezed and the whole signal is suppressed at least when the higher-order contributions appearing in the action are explicitly decoupled from the inflaton.Comment: 25 page

Effective horizons, junction conditions and large-scale magnetism

The quantum mechanical generation of hypermagnetic and hyperlectric fields in four-dimensional conformally flat background geometries rests on the simultaneous continuity of the effective horizon and of the extrinsic curvature across the inflationary boundary. The junction conditions for the gauge fields are derived in general terms and corroborated by explicit examples with particular attention to the limit of a sudden (but nonetheless continuous) transition of the effective horizon. After reducing the dynamics to a pair of integral equations related by duality transformations, we compute the power spectra and deduce a novel class of logarithmic corrections which turn out to be, however, numerically insignificant and overwhelmed by the conductivity effects once the gauge modes reenter the effective horizon. In this perspective the magnetogenesis requirements and the role of the postinflationary conductivity are clarified and reappraised. As long as the total duration of the inflationary phase is nearly minimal, quasi-flat hypermagnetic power spectra are comparatively more common than in the case of vacuum initial data.Comment: 12 pages, 1 figur

Hypermagnetic knots and gravitational radiation at intermediate frequencies

The maximally gyrotropic configurations of the hypermagnetic field at the electroweak epoch can induce a stochastic background of relic gravitational waves with comoving frequencies ranging from the $\mu$Hz to the kHz. Using two complementary approaches we construct a physical template family for the emission of the gravitational radiation produced by the hypermagnetic knots. The current constraints and the presumed sensitivities of the advanced wide-band interferometers (both terrestrial and space-borne) are combined to infer that the lack of observations at intermediate frequencies may invalidate the premise of baryogenesis models based (directly or indirectly) on the presence of gyrotropic configurations of the hypermagnetic field at the electroweak epoch. Over the intermediate frequency range the spectral energy density of the gravitational waves emitted by the hypermagnetic knots at the electroweak scale can exceed the inflationary signal even by nine orders of magnitude without affecting the standard bounds applicable on the stochastic backgrounds of gravitational radiation. The signal of hypermagnetic knots can be disambiguated, at least in principle, since the the produced gravitational waves are polarized.Comment: 19 pages, 2 figures; to appear in Classical and Quantum Gravity as a regular articl

Regular Cosmological Examples of Tree-Level Dilaton-Driven Models

We construct some examples of analytic solutions of the low energy (i.e. tree-level) string cosmological effective action. We work with the ``minimal'' field content (i.e. graviton and dilaton) in the absence of any dilaton potential. Provided the metric is sufficiently inhomogeneous we find solutions whose curvature invariants are bounded and everywhere defined in time and space. The dilaton coupling and its associated energy density are regular and homogeneous. A phase of growing (and non-singular) dilaton coupling compatible with the regularity of the curvature invariants without the addition of higher curvature (or higher genus) corrections to the tree-level effective action. We discuss the symmetries of the obtained solutions.Comment: 30 pages in LaTex style, 6 Encapsulated Postscript figures.A new section with a regular (and parity invariant) class of solutions has been included. Accepted for publication in Physical Review

Count response model for the CMB spots

The statistics of the curvature quanta generated during a stage of inflationary expansion is used to derive a count response model for the large-scale phonons determining, in the concordance lore, the warmer and the cooler spots of the large-scale temperature inhomogeneities. The multiplicity distributions for the counting statistics are shown to be generically overdispersed in comparison with conventional Poissonian regressions. The generalized count response model deduced hereunder accommodates an excess of correlations in the regime of high multiplicities and prompts dedicated analyses with forthcoming data collected by instruments of high angular resolution and high sensitivity to temperature variations per pixel.Comment: 9 page

Assigning Quantum-Mechanical Initial Conditions to Cosmological Perturbations

Quantum-mechanical initial conditions for the fluctuations of the geometry can be assigned in excess of a given physical wavelength. The two-point functions of the scalar and tensor modes of the geometry will then inherit corrections depending on which Hamiltonian is minimized at the initial stage of the evolution. The energy density of the background geometry is compared with the energy-momentum pseudo-tensor of the fluctuations averaged over the initial states, minimizing each different Hamiltonian. The minimization of adiabatic Hamiltonians leads to initial states whose back-reaction on the geometry is negligible. The minimization of non-adiabatic Hamiltonians, ultimately responsible for large corrections in the two-point functions, is associated with initial states whose energetic content is of the same order as the energy density of the background.Comment: 29 pages in Latex styl