Distortion of the acoustic peaks in the CMBR due to a primordial magnetic field

In this paper we study the effect of a magnetic field on the fluctuation spectrum of the cosmic microwave background. We find that upcoming measurements might give interesting bounds on large scale magnetic fields in the early Universe. If the effects are seen, it might be possible to establish the presence of different fields in different patches of the sky. Absence of any effect, will provide by one order of magnitude a better limit for a primordial field, now given by nucleosynthesis.Comment: 10 pages, 2 .ps figures included, extra reference added and typographical errors correcte

Probing Neutrino low energy and mass scales

Low energy neutrino processes are ideal probes for new Physics beyond the Standard Model. Cosmological observations and rare nuclear processes can test neutrino mass scales and give definite answers to unsolved basic questions like the Majorana/Dirac nature of the neutrino.Comment: 6 Pages, summary of the ``Probing low energy and mass scales'' session during the Neutrino Oscillation Workshop NOW2006, Otranto, Italy, September 9-16 200

Limits on the Non-Standard Interactions of Neutrinos from e+e−e^+ e^- Colliders

We provide an effective Lagrangian analysis of contact non-standard interactions of neutrinos with electrons, which can be effectively mediated by extra particles, and examine the associated experimental limits. At present, such interactions are strongly constrained only for $\nu_\mu$: the bounds are loose for $\nu_e$ and absent for $\nu_\tau$. We emphasize the unique role played by the reaction $e^+e^-\to \nu \bar{\nu}\gamma$ in providing direct constraints on such non-standard interactions.Comment: 15 LaTeX pages, 6 postscript figures, uses epsfig. New discussion on bounds from reactor anti-neutrino scattering off electrons; minor changes. To appear on Phys. Lett.

Neutrino mass bounds from cosmology

Cosmology is at present one of the most powerful probes of neutrino properties. The advent of precision data from the cosmic microwave background and large scale structure has allowed for a very strong bound on the neutrino mass. Here, I review the status of cosmological bounds on neutrino properties with emphasis on mass bounds on light neutrinos.Comment: 6 pages, 3 figures, talk given at NOW2004 workshop, Conca Specchiulla, Italy, September 11-17, 200

Spontaneous baryogenesis in flat directions

We discuss a spontaneous baryogenesis mechanism in flat directions. After identifying the Nambu-Goldstone mode which derivatively couples to the associated $U$(1) current and rotates due to the A-term, we show that spontaneous baryogenesis can be naturally realized in the context of the flat direction. As applications, we discuss two scenarios of baryogenesis in detail. One is baryogenesis in a flat direction with a vanishing $B-L$ charge, especially, with neither baryon nor lepton charge, which was recently proposed by Chiba and the present authors. The other is a baryogenesis scenario compatible with a large lepton asymmetry.Comment: 10 pages, no figure, the version accepted to Phys. Rev. D; a few explanatory comments are adde

Probing oscillations into sterile neutrinos with cosmology, astrophysics and experiments

We perform a thorough analysis of oscillation signals generated by one extra sterile neutrino, extending previous analyses done in simple limiting cases and including the effects of established oscillations among active neutrinos. We consider the following probes: solar, atmospheric, reactor and beam neutrinos, Big-Bang Nucleosynthesis (helium-4, deuterium), Cosmic Microwave Background, Large Scale Structure, supernovae, neutrinos from other astrophysical sources. We find no evidence for a sterile neutrino in present data, identify the still allowed regions, and study which future experiments can best probe them: sub-MeV solar experiments, more precise studies of CMB or BBN, future supernova explosions, etc. We discuss how the LSND hint is strongly disfavoured by the constraints of (standard) cosmology.Comment: 50 pages, many (14) figures. The text is divided into "results" and "technical details" sections. Final updated versio

Constraining dynamical dark energy with a divergence-free parametrization in the presence of spatial curvature and massive neutrinos

In this paper, we report the results of constraining the dynamical dark energy with a divergence-free parameterization, $w(z) = w_{0} + w_{a}(\frac{\ln(2+z)}{1+z}-\ln2)$, in the presence of spatial curvature and massive neutrinos, with the 7-yr WMAP temperature and polarization data, the power spectrum of LRGs derived from SDSS DR7, the Type Ia supernova data from Union2 sample, and the new measurements of $H_0$ from HST, by using a MCMC global fit method. Our focus is on the determinations of the spatial curvature, $\Omega_k$, and the total mass of neutrinos, $\sum m_{\nu}$, in such a dynamical dark energy scenario, and the influence of these factors to the constraints on the dark energy parameters, $w_0$ and $w_a$. We show that $\Omega_k$ and $\sum m_{\nu}$ can be well constrained in this model; the 95% CL limits are: $-0.0153<\Omega_k<0.0167$ and $\sum m_{\nu}<0.56$ eV. Comparing to the case in a flat universe, we find that the error in $w_0$ is amplified by 25.51%, and the error in $w_a$ is amplified by 0.14%; comparing to the case with a zero neutrino mass, we find that the error in $w_0$ is amplified by 12.24%, and the error in $w_a$ is amplified by 1.63%.Comment: 5 pages, 2 figures; discussions added; accepted for publication in Physics Letters

Could Large CP Violation Be Detected at Colliders?

We argue that CP--violation effects below a few tenths of a percent are probably undetectable at hadron and electron colliders. Thus only operators whose contributions interfere with tree--level Standard Model amplitudes are detectable. We list these operators for Standard Model external particles and some two and three body final state reactions that could show detectable effects. These could test electroweak baryogenesis scenarios.Comment: 11pp, LaTeX, UM--TH--92--27(massaged to make TeX output cleaner), no picture

Fluids in cosmology

We review the role of fluids in cosmology by first introducing them in General Relativity and then by applying them to a FRW Universe's model. We describe how relativistic and non-relativistic components evolve in the background dynamics. We also introduce scalar fields to show that they are able to yield an inflationary dynamics at very early times (inflation) and late times (quintessence). Then, we proceed to study the thermodynamical properties of the fluids and, lastly, its perturbed kinematics. We make emphasis in the constrictions of parameters by recent cosmological probes.Comment: 34 pages, 4 figures, version accepted as invited review to the book "Computational and Experimental Fluid Mechanics with Applications to Physics, Engineering and the Environment". Version 2: typos corrected and references expande

New Signatures for a Light Stop at LEP2 in SUSY Models with Spontaneously Broken R-Parity

In a class of supersymmetric models with R-parity breaking the lightest stop can have new decay modes into third generation fermions, $\tilde{t}_1 \rightarrow b + \tau$. We show that this decay may be dominant or at least comparable to the ordinary R-parity conserving mode $\tilde{t}_1 \rightarrow c + \tilde{\chi}_1^0$, where $\tilde{\chi}_1^0$ denotes the lightest neutralino. The new R-parity violating decay mode could provide new signatures for stop production at LEP.Comment: uudecoded latex file, 12 pages with 3 figures included. The complete uudecoded ps paper is also available via anonymous ftp at ftp://neutrinos.uv.es/pub/papers/ps/stop1.u