Massive scalar fields in the early Universe

We discuss the role of gravitational excitons/radions in different cosmological scenarios. Gravitational excitons are massive moduli fields which describe conformal excitations of the internal spaces and which, due to their Planck-scale suppressed coupling to matter fields, are WIMPs. It is demonstrated that, depending on the concrete scenario, observational cosmological data set strong restrictions on the allowed masses and initial oscillation amplitudes of these particles.Comment: 6 pages, Latex2e, talk presented at the 1st International Workshop on Astronomy and Relativistic Astrophysics, 12-16 October, 2003, (IWARA2003), Olinda-PE, Brazi

Sterile neutrino dark matter in warped extra dimensions

We consider a (long-lived) sterile neutrino dark matter scenario in a five dimensional (5D) warped extra dimension model where the fields can live in the bulk, which is partly motivated from the absence of the absolutely stable particles in a simple Randall-Sundrum model. The dominant production of the sterile neutrino can come from the decay of the radion (the scalar field representing the brane separation) around the electroweak scale. The suppressions of the 4D parameters due to the warp factor and the small wave function overlaps in the extra dimension help alleviate the exceeding fine-tunings typical for a sterile neutrino dark matter scenario in a 4D setup.Comment: Typos corrected and references adde

Pseudo-Dirac Bino Dark Matter

While the bino-dominated lightest neutralino of the minimal supersymmetric Standard Model (MSSM) is an interesting and widely-studied candidate of the dark matter, the p-wave suppression of its annihilation cross section requires fine-tunings of the MSSM spectra to be consistent with WMAP observations. We propose pseudo-Dirac bino that arises in theories with D-type supersymmetry-breaking as an intriguing alternative candidate of dark matter. The pseudo-Dirac nature of the bino gives a natural mechanism of enhanced co-annihilation because these two states are degenerate in the absence of electroweak symmetry breaking. In addition, the lightest state can be consistent with limits of direct detection experiments because of the lack of vector interactions, as with the case of the MSSM bino.Comment: 18 pages, 2 figures, REVTEX, to be published in PRD, made minor changes and added comments to match the published versio

Constraints on parameters of models with extra dimension from primordial nucleosynthesis

5D models with one 3D brane and one infinite extra dimension are studied. Matter is confined to the brane, gravity extends to the bulk. Models with positive and negative tension of the brane are studied. Cosmological solutions on the brane are obtained by solving the generalized Friedmann equation. As the input in cosmological solutions we use the present-time observational cosmological parameters. We find constraints on dimensionless combinations of scales of 5D models which follow from the requirement that the models reproduce the data on production of ${}^4 He$ in primordial nucleosynthesis.Comment: 12 page

The small mixing angle θ13\theta_{13} and the lepton asymmetry

We present the correlation of low energy CP phases, both Dirac and Majorana, and the lepton asymmetry for the baryon asymmetry in the universe, with a certain class of Yukawa matrices that consist of two right-handed neutrinos and include one texture zero in themselves. For cases in which the amount of the lepton asymmetry $Y_L$ turns out to be proportional to $\theta_{13}^2$, we consider the relation between two types of CP phases and the relation of $Y_L$ versus the Jarlskog invariant or the amplitude of neutrinoless double beta decay as $\theta_{13}$ varies.Comment: 17 pages, 14 figures, information for figures added, version published in PR

Interaction of cosmic background neutrinos with matter of periodic structure

We study coherent interaction of cosmic background neutrinos(CBNs) with matter of periodic structure. The mixing and small masses of neutrinos discovered in neutrino oscillation experiments indicate that CBNs which have very low energy today should be in mass states and can transform from one mass state to another in interaction with electrons in matter. We show that in a coherent scattering process a periodic matter structure designed to match the scale of the mass square difference of neutrinos can enhance the conversion of CBNs from one mass state to another. Energy of CBNs can be released in this scattering process and momentum transfer from CBNs to electrons in target matter can be obtained.Comment: 6 pages, 5 figures, publication versio

Singlino dominated LSP as CDM candidate in supersymmetric models with an extra U(1)

We consider a singlino dominated neutralino in supersymmetric models with an extra U(1). In case both the $\mu$ term and also the $Z^\prime$ mass are generated by the vacuum expectation value of the scalar component of the same singlet chiral superfield, generically the lightest neutralino is not expected to be dominated by the singlino. However, if the gaugino corresponding to the extra U(1) is sufficiently heavy, the lightest neutralino can be dominated by the singlino and still satisfy the constraints resulting from the $Z^\prime$ phenomenology. We assume a supersymmetry breaking scenario in which the extra U(1) gaugino can be much heavier than other gauginos. In that framework we show that the singlino dominated lightest neutralino may be a good candidate for dark matter in a parameter space where various phenomenological constraints are satisfied.Comment: 25 pages, 6 figures, title is changed, introduction is extended, sec.2 is moved to appendix, some references are added, published versio

Nonthermal Supermassive Dark Matter

We discuss several cosmological production mechanisms for nonthermal supermassive dark matter and argue that dark matter may be elementary particles of mass much greater than the weak scale. Searches for dark matter should not be limited to weakly interacting particles with mass of the order of the weak scale, but should extend into the supermassive range as well.Comment: 11 page LaTeX file. No major changes. Version accepted by PR

GUT baryogenesis after preheating: numerical study of the production and decay of X-bosons

We perform a fully non-linear calculation of the production of supermassive Grand Unified Theory (GUT) $X$ bosons during preheating, taking into account the fact that they are unstable with a decay width $\Gamma_X$. We show that parametric resonance does not develop if $\Gamma_X$ is larger than about $10^{-2} m_X$. We compute the nonthermal number density of superheavy bosons produced in the preheating phase and demonstrate that the observed baryon asymmetry may be explained by GUT baryogenesis after preheating if $\Gamma_X$ is smaller than about $10^{-3} m_X$.Comment: 13 pages, LaTeX file, 3 figures. One reference added and minor change

How heavy can the Fermions in Split Susy be? A study on Gravitino and Extradimensional LSP

In recently introduced Split Susy theories, in which the scale of Susy breaking is very high, the requirement that the relic abundance of the Lightest SuperPartner (LSP) provides the Dark Matter of the Universe leads to the prediction of fermionic superpartners around the weak scale. This is no longer obviously the case if the LSP is a hidden sector field, such as a Gravitino or an other hidden sector fermion, so, it is interesting to study this scenario. We consider the case in which the Next-Lightest SuperPartner (NLSP) freezes out with its thermal relic abundance, and then it decays to the LSP. We use the constraints from BBN and CMB, together with the requirement of attaining Gauge Coupling Unification and that the LSP abundance provides the Dark Matter of the Universe, to infer the allowed superpartner spectrum. As very good news for a possible detaction of Split Susy at LHC, we find that if the Gravitino is the LSP, than the only allowed NLSP has to be very purely photino like. In this case, a photino from 700 GeV to 5 TeV is allowed, which is difficult to test at LHC. We also study the case where the LSP is given by a light fermion in the hidden sector which is naturally present in Susy breaking in Extra Dimensions. We find that, in this case, a generic NLSP is allowed to be in the range 1-20 TeV, while a Bino NLSP can be as light as tens of GeV.Comment: 29 pages, 12 figures. v2: modified conclusions for bino NLSP. v3: corrected small mistake in Gauge Coupling Unification, conclusions unchange