General Modified Friedmann Equations in Rainbow Flat Universe, by Thermodynamics

We investigate the derivation of Friedmann equations in Rainbow gravity following Jacobson thermodynamic approach. We do not restrict the rainbow functions to be constant as is customarily used, and show that the first law of thermodynamics with a corresponding `classical' proportionality between entropy and surface area, supplemented eventually by a `quantum' logarithmic correction, are not in general sufficient to obtain the equations in flat FRW metrics.Comment: 7 pages, to appear in EPJ

The U(1) symmetry of the non-tribimaximal pattern in the degenerate mass spectrum case of the neutrino mass matrix

On account of the new neutrino oscillation data signalling a non-zero value for the smallest mixing angle ($\theta_z$), we present an explicit realization of the underlying U(1) symmetry characterizing the maximal atmospheric mixing angle ($\theta_y = \pi / 4$) pattern with two degenerate masses but now with generic values of $\theta_z$. We study the effects of the form invariance with respect to U(1), and/or $Z_3$, $Z_2$ subgroups, on the Yukawa couplings and the mass terms. Later on, we specify $\theta_z$ to its experimental best fit value ($\sim 8^o$), and impose the symmetry in an entire model which includes charged leptons, and many Higgs doublets or standard model singlet heavy scalars, to show that it can make room for the charged lepton mass hierarchies. In addition, we show for the non-tribimaximal value of $\theta_z \neq 0$ within type-I seesaw mechanism enhanced with flavor symmetry that neutrino mass hierarchies can be generated. Furthermore, lepton/baryogenesis can be interpreted via type-II seesaw mechanism within a setup meeting the flavor U(1)-symmetry.Comment: latex, 1 table, 20 pages. Typos are corrected, shortened version to appear in Phys. Rev.

Salvaging Power-Law Inflation through Warming

Power-Law inflation with scale factor $a \propto t^m$ is investigated in the context of warm inflation. The treatment is performed in the weak and strong dissipation limits. In addition, we discuss the common three cases for the thermal dissipation coefficient $\Gamma(T)$. We compare the theoretical results of the Power-Law model within warm inflation with the observational constraints from Planck $2018$ and BICEP/Keck 2018, as presented by the tensor-to-scalar ratio $r$ and spectral index $n_s$. The model results agree largely with the observations for most of the $\Gamma(T)$ cases. Furthermore, in order to addresses the problem of exiting the inflationary epoch, we suggest a perturbed modification to the power-law definition so that it becomes affine, and find that this small change is sufficient to provide a successful exit scenario with suitable e-foldings number. Finally, we examine this perturbation ansatz within the context of cold inflation with exponential potential, and we find that it can accommodate the observational data with sufficient e-foldings. Thus, the study successfully rescues the Power-Law inflation and the exponential potential in both warm and cold inflation contexts.Comment: pdflatex, 10 pages (epjc style), 5 tables, 6 figure

Dissipation of the sectored heliospheric magnetic field near the heliopause: a mechanism for the generation of anomalous cosmic rays

The recent observations of the anomalous cosmic ray (ACR) energy spectrum as Voyagers 1 and 2 crossed the heliospheric termination shock have called into question the conventional shock source of these energetic particles. We suggest that the sectored heliospheric magnetic field, which results from the flapping of the heliospheric current sheet, piles up as it approaches the heliopause, narrowing the current sheets that separate the sectors and triggering the onset of collisionless magnetic reconnection. Particle-in-cell simulations reveal that most of the magnetic energy is released and most of this energy goes into energetic ions with significant but smaller amounts of energy going into electrons. The energy gain of the most energetic ions results from their reflection from the ends of contracting magnetic islands, a first order Fermi process. The energy gain of the ions in contracting islands increases their parallel (to the magnetic field ${\bf B}$) pressure $p_\parallel$ until the marginal firehose condition is reached, causing magnetic reconnection and associated particle acceleration to shut down. The model calls into question the strong scattering assumption used to derive the Parker transport equation and therefore the absence of first order Fermi acceleration in incompressible flows. A simple 1-D model for particle energy gain and loss is presented in which the feedback of the energetic particles on the reconnection drive is included. The ACR differential energy spectrum takes the form of a power law with a spectral index slightly above 1.5. The model has the potential to explain several key Voyager observations, including the similarities in the spectra of different ion species.Comment: Submitted to ApJ; shortened abstract; degraded figure qualit

The (Z_2)^3 symmetry of the non-tri-bimaximal pattern for the neutrino mass matrix

In view of the recent neutrino oscillation data pointing to a non-vanishing value for the smallest mixing angle ($\theta_z$), we derive and find explicit realizations of the $(Z_2)^3$ flavor symmetry which characterizes, for the neutrino mass matrix, uniquely a variant of the tripartite form, originally conceived to lead to the tri-bimaximal mixing with $\theta_z=0$, so that to allow now for a non-tri-bimaximal pattern with non-zero $\theta_z$. We impose this flavor symmetry in a setting including the charged leptons and we see that it can make room, through higher order terms involving new SM-singlet scalars, for the mass hierarchy of charged leptons. Moreover, within type-I seesaw mechanism augmented with the flavor symmetry, certain patterns occurring in both the Dirac and the Majorana neutrino mass matrices can accommodate all types of mass hierarchies in the effective neutrino mass matrix, but no lepton/baryon asymmetry can be generated. Finally, we discuss how type-II seesaw mechanism, when supplemented with the flavor symmetry, could be used to interpret the observed baryon asymmetry through leptogenesis.Comment: 14 pages, 1 table, added references, version to appear in PRD. arXiv admin note: text overlap with arXiv:1008.406

Characterization of Viral Entry Inhibitors

Hepatitis C virus (HCV), Human Immunodeficiency virus (HIV) and Herpes Simplex virus (HSV) are pathogenic viruses known to cause liver disorder, acquired immunodeficiency and skin lesions, respectively. Although current therapies have played substantial roles in the fight against these pathogens, their use is limited and for the most part does not result in viral eradication. Moreover, most antivirals target viral encoded structures which overtime foster the development of resistant strains. Hence, antivirals aimed at preventing initial infection represent a promising strategy for viral combat. This dissertation focuses on the characterization of viral entry inhibitors and their potential use. The first compounds evaluated come from the phenothiazines family, widely used as antipsychotic drugs. Phenothiazines were shown to suppress HCV entry by intercalating into cholesterol-rich membrane domains of target cells thus reducing viral-host fusion. The second candidates studied are two members of the H1-anthistamines currently used for allergy treatment. Both compounds strongly reduce HCV entry, likely at the fusion step, and its inhibition was associated with cholesterol content in the virion and host cells, pointing to the use of an NPC1L1-receptor dependent mechanism. Lastly, we evaluated the antiviral activity of PD 404,182 (PD) as an alternate treatment for HCV-HIV coinfected patients as well as its potential use as an anti-HIV microbicide. PD is able to reduce viral entry of the three pathogens through physical disruption of virions releasing the nucleic acids into the surrounding medium. Moreover, PD possesses several qualities pointing to its use as a potential microbicide

Nielsen-Olesen vortex in varying-alpha theories

We consider soliton solutions to Bekenstein's theory, for which the fine structure constant $\alpha=e^2/(4\pi\hbar c)$ is allowed to vary due to the presence of a dielectric field pervading the vacuum. More specifically we investigate the effects of a varying $\alpha$ upon a complex scalar field with a U(1) electromagnetic gauge symmetry subject to spontaneous symmetry breaking. We find vortex solutions to this theory, similar to the Nielsen-Olesen vortex. Near the vortex core the electric charge is typically much larger than far away from the string, lending these strings a superconducting flavour. In general the dielectric field coats the usual local string with a global string envelope. We discuss the cosmological implications of networks of such strings, with particular emphasis on their ability to generate inhomogeneous recombination scenarios. We also consider the possibility of the dielectric being a charged free field. Even though the vacuum of such a field is trivial, we find that the dielectric arranges itself in the shape of a local string, with a quantized magnetic flux at the core -- presumably borrowing these topological features from the underlying Nielsen-Olesen vortex.Comment: 7 pages, 1 figur

Fermion Masses and Mixing in Four and More Dimensions

We give an overview of recent progress in the study of fermion mass and flavor mixing phenomena. Mass matrix ansatze are considered within the SM and SUSY GUTs where some predictive frameworks based on SU(5) and SO(10) are reviewed. We describe a variety of schemes to construct quark mass matrices in extra dimensions focusing on four major classes: models with the SM residing on 3-brane, models with universal extra dimensions, models with split fermions and models with warped extra dimensions. We outline how realistic patterns of quark mass matrices could be derived from orbifold models in heterotic superstring theory. Finally, we address the fermion mass problem in intersecting D-branes scenarios, and present models with D6-branes able to give a good quantitatively description of quark masses and mixing. The role of flavor/CP violation problem as a probe of new physics is emphasized.Comment: a review based on seminars presented by S.K. in different places, 34 pages, late