Quantization of Higher Spin Superfields in the anti-de Sitter Superspace

We describe a Lagrangian quantization of the free massless gauge superfield theories of higher superspins both in the anti-de Sitter and flat global superspaces.Comment: 9 pages, LaTe

MSLED, Neutrino Oscillations and the Cosmological Constant

We explore the implications for neutrino masses and mixings within the minimal version of the supersymmetric large-extra-dimensions scenario (MSLED). This model was proposed in {\tt hep-ph/0404135} to extract the phenomenological implications of the promising recent attempt (in {\tt hep-th/0304256}) to address the cosmological constant problem. Remarkably, we find that the simplest couplings between brane and bulk fermions within this approach can lead to a phenomenologically-viable pattern of neutrino masses and mixings that is also consistent with the supernova bounds which are usually the bane of extra-dimensional neutrino models. Under certain circumstances the MSLED scenario can lead to a lepton mixing (PMNS) matrix close to the so-called bi-maximal or the tri-bimaximal forms (which are known to provide a good description of the neutrino oscillation data). We discuss the implications of MSLED models for neutrino phenomenology.Comment: 38 pages, 1 figure; Reposted with a few additional reference

TIME-SYMMETRIC INITIAL DATA SETS IN 4--D DILATON GRAVITY

I study the time--symmetric initial--data problem in theories with a massless scalar field (dilaton), free or coupled to a Maxwell field in the stringy way, finding different initial--data sets describing an arbitrary number of black holes with arbitrary masses, charges and asymptotic value of the dilaton. The presence of the scalar field gives rise to a number of interesting effects. The mass and charges of a single black hole are different in its two asymptotically flat regions across the Einstein--Rosen bridge. The same happens to the value of the dilaton at infinity. This forbids the identification of these asymptotic regions in order to build (Misner) wormholes in the most naive way. Using different techniques, I find regular initial data for stringy wormholes. The price payed is the existence singularities in the dilaton field. The presence of a single--valued scalar seems to constrain strongly the allowed topologies of the initial space--like surface. Other kinds of scalar fields (taking values on a circle or being defined up to an additive constant) are also briefly considered.Comment: latex file, 38 pages

Running Spectral Index and Formation of Primordial Black Hole in Single Field Inflation Models

A broad range of single field models of inflation are analyzed in light of all relevant recent cosmological data, checking whether they can lead to the formation of long-lived Primordial Black Holes (PBHs). To that end we calculate the spectral index of the power spectrum of primordial perturbations as well as its first and second derivatives. PBH formation is possible only if the spectral index increases significantly at small scales, i.e. large wave number $k$. Since current data indicate that the first derivative $\alpha_S$ of the spectral index $n_S(k_0)$ is negative at the pivot scale $k_0$, PBH formation is only possible in the presence of a sizable and positive second derivative ("running of the running") $\beta_S$. Among the three small-field and five large-field models we analyze, only one small-field model, the "running mass" model, allows PBH formation, for a narrow range of parameters. We also note that none of the models we analyze can accord for a large and negative value of $\alpha_S$, which is weakly preferred by current data.Comment: 26 pages, 5 figures, Refs. added, Minor textual change; version to appear in JCA

Quintessence Restrictions on Negative Power and Condensate Potentials

We study the cosmological evolution of scalar fields that arise from a phase transition at some energy scale \Lm_c. We focus on negative power potentials given by V=c\Lm_c^{4+n}\phi^{-n} and restrict the cosmological viable values of \Lm_c and $n$. We make a complete analysis of $V$ and impose $SN1a$ conditions on the different cosmological parameters. The cosmological observations ruled out models where the scalar field has reached its attractor solution. For models where this is not the case, the analytic approximated solutions are not good enough to determine whether a specific model is phenomenologically viable or not and the full differential equations must be numerically solved. The results are not fine tuned since a change of 45% on the initial conditions does not spoil the final results. We also determine the values of $N_c, N_f$ that give a condensation scale \Lm_c consistent with gauge coupling unification, leaving only four models that satisfy unification and SN1a constraints.Comment: 15 pages, LaTeX, 8 Figures. Minor changes in text, a discussion on initial conditions added (accepted in Phys.Rev.D

DBI Inflation in the Tip Region of a Warped Throat

Previous work on DBI inflation, which achieves inflation through the motion of a $D3$ brane as it moves through a warped throat compactification, has focused on the region far from the tip of the throat. Since reheating and other observable effects typically occur near the tip, a more detailed study of this region is required. To investigate these effects we consider a generalized warp throat where the warp factor becomes nearly constant near the tip. We find that it is possible to obtain 60 or more e-folds in the constant region, however large non-gaussianities are typically produced due to the small sound speed of fluctuations. For a particular well-studied throat, the Klebanov-Strassler solution, we find that inflation near the tip may be generic and it is difficult to satisfy current bounds on non-gaussianity, but other throat solutions may evade these difficulties.Comment: 26 pages, 1 figure. v1. references added, typos corrected v2. clarifications mad

Observational consequences of the Standard Model Higgs inflation variants

We consider the possibility to observationally differentiate the Standard Model (SM) Higgs driven inflation with non-minimal couplingto gravity from other variants of SM Higgs inflation based on the scalar field theories with non-canonical kinetic term such as Galileon-like kinetic term and kinetic term with non-minimal derivative coupling to the Einstein tensor. In order to ensure consistent results, we study the SM Higgs inflation variants by using the same method, computing the full dynamics of the background and perturbations of the Higgs field during inflation at quantum level. Assuming that all the SM Higgs inflation variants are consistent theories, we use the MCMC technique to derive constraints on the inflationnoary parameters and the Higgs boson mass from their fit to WMAP7+SN+BAO data set. We conclude that a combination of a Higgs mass measurement by the LHC and accurate determination by the PLANCK satellite of the spectral index of curvature perturbations and tensor-to-scalar ratio will enable to distinguish among these models. We also show that the consistency relations of the SM Higgs inflation variants are distinct enough to differentiate the models.Comment: 22 pages, 4 figure

Potential-driven Galileon inflation

For the models of inflation driven by the potential energy of an inflaton field $\phi$, the covariant Galileon Lagrangian $(\partial\phi)^2\Box \phi$ generally works to slow down the evolution of the field. On the other hand, if the Galileon self-interaction is dominant relative to the standard kinetic term, we show that there is no oscillatory regime of inflaton after the end of inflation. This is typically accompanied by the appearance of the negative propagation speed squared $c_s^2$ of a scalar mode, which leads to the instability of small-scale perturbations. For chaotic inflation and natural inflation we clarify the parameter space in which inflaton oscillates coherently during reheating. Using the WMAP constraints of the scalar spectral index and the tensor-to-scalar ratio as well, we find that the self coupling $\lambda$ of the potential $V(\phi)=\lambda \phi^4/4$ is constrained to be very much smaller than 1 and that the symmetry breaking scale $f$ of natural inflation cannot be less than the reduced Planck mass $M_{\rm pl}$. We also show that, in the presence of other covariant Galileon Lagrangians, there are some cases in which inflaton oscillates coherently even for the self coupling $\lambda$ of the order of 0.1, but still the instability associated with negative $c_s^2$ is generally present.Comment: 22 pages, 15 figure

Static quantities of the W boson in the SU_L(3) X U_X(1) model with right-handed neutrinos

The static electromagnetic properties of the $W$ boson, $\Delta \kappa$ and $\Delta Q$, are calculated in the SU_L(3)} \times U_X(1) model with right-handed neutrinos. The new contributions from this model arise from the gauge and scalar sectors. In the gauge sector there is a new contribution from a complex neutral gauge boson $Y^0$ and a singly-charged gauge boson $Y^\pm$. The mass of these gauge bosons, called bileptons, is expected to be in the range of a few hundreds of GeV according to the current bounds from experimental data. If the bilepton masses are of the order of 200 GeV, the size of their contribution is similar to that obtained in other weakly coupled theories. However the contributions to both $\Delta Q$ and $\Delta \kappa$ are negligible for very heavy or degenerate bileptons. As for the scalar sector, an scenario is examined in which the contribution to the $W$ form factors is identical to that of a two-Higgs-doublet model. It is found that this sector would not give large corrections to $\Delta \kappa$ and $\Delta Q$.Comment: New material included. Final version to apppear in Physical Review