Effect of Priomordial non-Gaussianities on Galaxy Clusters Scaling Relations

Galaxy clusters are a valuable source of cosmological information. Their formation and evolution depends on the underlying cosmology and on the statistical nature of the primordial density fluctuations. In this work we investigate the impact of primordial non-gaussianities (PNG) on the scaling properties of galaxy clusters. We performed a series of cosmological hydrodynamic N-body simulations featuring adiabatic gas physics and different levels of non-Gaussian initial conditions within the $\Lambda$CDM framework. We focus on the T-M, S-M, Y-M and Yx-M scalings relating the total cluster mass with temperature, entropy and SZ cluster integrated pressure that reflect the thermodynamical state of the intra-cluster medium. Our results show that PNG have an impact on cluster scalings laws. The mass power-law indexes of the scalings are almost unaffected by the existence of PNG but the amplitude and redshift evolution of their normalizations are clearly affected. The effect is stronger for the evolution of the Y-M and Yx-M normalizations, which change by as much as 22% and 16% when $f_{NL}$ varies from -500 to 500, respectively. These results are consistent with the view that positive/negative $f_{NL}$ affect cluster profiles due to an increase/decrease of cluster concentrations. At low values of $f_{NL}$, as suggested by present Planck constraints on a scale invariant $f_{NL}$, the impact on the scalings normalizations is only a few percent, which is small when compared with the effect of additional gas physics and other cosmological effects such as dark energy. However if $f_{NL}$ is in fact a scale dependent parameter, PNG may have larger positive/negative amplitudes at clusters scales and therefore our results suggest that PNG should be taken into account when galaxy cluster data is used to infer cosmological parameters or to asses the constraining power of future cluster surveys.Comment: 10 pages, 3 figures and 2 tables, submitted to MNRA

On the Nonrelativistic Limit of the Scattering of Spin One-half Particles Interacting with a Chern-Simons Field

Starting from a relativistic quantum field theory, we study the low energy scattering of two fermions of opposite spins interacting through a Chern-Simons field. Using the Coulomb gauge we implement the one loop renormalization program and discuss vacuum polarization and magnetic moment effects. We prove that the induced magnetic moments for spin up and spin down fermions are the same. Next, using an intermediary auxiliary cutoff the scattering amplitude is computed up to one loop. Similarly to Aharonov-Bohm effect for spin zero particles, the low energy part of the amplitude contains a logarithmic divergence in the limit of very high intermediary cutoff. In our approach however the needed counterterm is automatically provided without any additional hypothesis.Comment: 12 pages, 2 figures, revtex; Minor correction

Dynamical Monte Carlo method for stochastic epidemic models

In this work we introduce a new approach to Dynamical Monte Carlo methods to simulate markovian processes. We apply this approach to formulate and study an epidemic generalized SIRS model. The results are in excellent agreement with the fourth order Runge-Kutta method in a region of deterministic solution. Introducing local stochastic interactions, the Runge-Kutta method is no longer applicable. Thus, we solve the system described by a set of stochastic differential equations by a Dynamical Monte Carlo technique and check the solutions self-consistently with a stochastic version of the Euler method. We also analyzed the results under the herd-immunity concept.Comment: 18 pages, 4 figures in ps format, regular article, Latex, written with Scientific WorkPlace 3.5

The R0 Approach to Epidemic-non-Epidemic Phases Revisited

In this work, we revisit the basic reproduction rate $\mathcal{R}_{0}$ definition for analysis of epidemic-non-epidemic phases describing the dynamics of the discrete stochastic version of the epidemic $SIR$ model based on the Master Equation formalism. One shows that it is a very precise and efficient way to determine the epidemic threshold; using its most primitive concept, we can find exact results.Comment: Submitted to PR

Stability and gravitational collapse of neutron stars with realistic equations of state

We discuss the stability and construct dynamical configurations describing the gravitational collapse of unstable neutron stars with realistic equations of state compatible with the recent LIGO-Virgo constraints. Unlike other works that consider the collapse of a stellar configuration without a priori knowledge if it is stable or unstable, we first perform a complete analysis on stellar stability for such equations of state. Negative values of the squared frequency of the fundamental mode indicate us radial instability with respect to the collapse of the unstable star to a black hole. We find numerical solutions corresponding to the temporal and radial behavior during the evolution of the collapse for certain relevant physical quantities such as mass, luminosity, energy density, pressure, heat flow, temperature and quantities that describe bulk viscous processes. Our results show that the equation of state undergoes abrupt changes close to the moment of event horizon formation as a consequence of dissipative effects. During the collapse process all energy conditions are respected, which implies that our model is physically acceptable.Comment: 13 pages, 11 figure

Causal thermodynamics of a gravitational collapse model for an anisotropic fluid with dissipative flows

This paper presents a hydrodynamic and thermodynamic treatment of a radiant star model that undergoes a dissipative gravitational collapse, from a certain initial configuration until it becomes a black hole. The collapsing star consists of a locally anisotropic non-perfect fluid, where we explore the consequences of including viscous pressures, both shear and bulk viscosities, as well as radial heat flow. We analyze the temporal evolution of the heat flux, mass function, luminosity perceived by an observer at infinity and the effective surface temperature. It is shown that this simple exact model, satisfying all the energy conditions throughout the interior region of the star and during all the collapse process, provides a physically reasonable behavior for the temperature profile in the context of the extended irreversible thermodynamics.Comment: 40 pages, 14 figures. To appear in General Relativity and Gravitatio

Meson decay in the Fock-Tani Formalism

The Fock-Tani formalism is a first principle method to obtain effective interactions from microscopic Hamiltonians. Usually this formalism was applied to scattering, here we introduced it to calculate partial decay widths for mesons.Comment: Presented at HADRON05 XI. "International Conference on Hadron Spectroscopy" Rio de Janeiro, Brazil, August 21 to 26, 200

Noncommutative Correction to the Aharonov-Bohm Scattering: a Field Theory Approach

We study a noncommutative nonrelativistic theory in 2+1 dimensions of a scalar field coupled to the Chern-Simons field. In the commutative situation this model has been used to simulate the Aharonov-Bohm effect in the field theory context. We verified that, contrarily to the commutative result, the inclusion of a quartic self-interaction of the scalar field is not necessary to secure the ultraviolet renormalizability of the model. However, to obtain a smooth commutative limit the presence of a quartic gauge invariant self-interaction is required. For small noncommutativity we fix the corrections to the Aharonov-Bohm scattering and prove that up to one-loop the model is free from dangerous infrared/ultraviolet divergences.Comment: 20 pages, 5 figure

Glueball decay in the Fock-Tani formalism

We investigate the two-meson decay modes for $f_0(1500)$. In this calculation we consider this resonance as a glueball. The Fock-Tani formalism is introduced to calculate the decay width.Comment: Presented at "Hadron05 XI. International Conference on Hadron Spectroscopy", Rio de Janeiro, Brazil, August 21 to 26, 200

Lorentz breaking supersymmetry and Horava-Lifshitz-like models

We present a Lorentz-breaking supersymmetric algebra characterized by a critical exponent $z$. Such construction requires a non trivial modification of the supercharges and superderivatives. The improvement of renormalizability for supersymmetric scalar QED is shown and the K\"ahlerian effective potentials are calculated in different cases. We also show how the theory flows naturally to the Lorentz symmetric case at low energies.Comment: 19 pages, 7 figures. Minor correction. Version to appear in PR