Neutrino Mass Patterns within the See-saw Model from Multi-localization along Extra Dimensions

We study a multi-localization model for charged leptons and neutrinos, including the possibility of a see-saw mechanism. This framework offers the opportunity to allow for realistic solutions in a consistent model without fine-tuning of parameters, even if quarks are also considered. Those solutions predict that the large Majorana mass eigenvalues for right-handed neutrinos are of the same order of magnitude, although this almost common mass can span a large range (bounded from above by $\sim 10^{12}{\rm GeV}$). The model also predicts Majorana masses between $\sim 10^{-2}{\rm eV}$ and $\sim 5 \ 10^{-2}{\rm eV}$for the left-handed neutrinos, both in the normal and inverted mass hierarchy cases. This mass interval corresponds to sensitivities which are reachable by proposed neutrinoless double$\beta$decay experiments. The preferred range for leptonic mixing angle$\theta_{13}$is:$10^{-2} \lesssim \sin \theta_{13} \lesssim 10^{-1}$, but smaller values are not totally excluded by the model.Comment: 36 pages, 8 figure

Heavy-meson physics and flavour violation with a single generation

We study flavour-violating processes which involve heavy B- and D-mesons and are mediated by Kaluza-Klein modes of gauge bosons in a previously suggested model where three generations of the Standard Model fermions originate from a single generation in six dimensions. We find the bound on the size R of the extra spatial dimensions 1/R>3.3 TeV, which arises from the three-body decay B_s to K mu e. Due to the still too low statistics this bound is much less stringent than the constraint arising from K to mu e, 1/R>64 TeV, which was found in a previous work (Frere et al., JHEP, 2003). Nevertheless, we argue that a clear signature of the model would be an observation of K to mu e and B_s to K mu e decays without observations of other flavour and lepton number changing processes at the same precision level.Comment: 15 page

Fermions in the vortex background on a sphere

In 5+1 dimensions, we construct a vortex-like solution on a two-dimensional sphere. We study fermionic zero modes in the background of this solution and relate them to the replication of fermion families in the Standard Model. In particular, using a compactified space removes the need for the difficult localisation of gauge fields, while the present procedure (rather than naive compactification on a disk) also removes spurious fermionic modes.Comment: 13 pages, 1 eps figure, JHEP3 style required, references adde

Towards Z_2-protected gauge--Higgs unification

In theories with flux compactification in eight or higher dimensions, the extra-dimensional components of the gauge field may be regarded as the Higgs field candidates. We suggest a way to protect these components from getting large tree-level masses by imposing a $Z_2$-symmetry acting on compact manifolds and background fields on them. In our scheme the infinite series of heavy KK modes naturally decouples from the light Higgs candidates, whose number is generically larger than one. We also present toy models with three families of leptons, illustrating that the Yukawa sector in our scheme is fairly strongly constrained. In one of these models, one fermion gets a tree-level mass after electroweak symmetry breaking, while two others remain naturally massless at the tree level.Comment: A few points clarified. Journal versio

Fermionic zero modes in self-dual vortex background

We study fermionic zero modes in the background of self-dual vortex on a two-dimensional non-compact extra space in 5+1 dimensions. In the Abelian Higgs model, we present an unified description of the topological and non-topological self-dual vortex on the extra two dimensions. Based on it, we study localization of bulk fermions on a brane with inclusion of Yang-Mills and gravity backgrounds in six dimensions. Through two simple cases, it is shown that the vortex background contributes a phase shift to the fermionic zero mode, this phase is actually origin from the Aharonov-Bohm effect.Comment: 11 pages, no figures, to appear in MPL

Neutrinos and the matter-antimatter asymmetry in the Universe

The discovery of neutrino oscillations provides a solid evidence for nonzero neutrino masses and leptonic mixing. The fact that neutrino masses are so tiny constitutes a puzzling problem in particle physics. From the theoretical viewpoint, the smallness of neutrino masses can be elegantly explained through the seesaw mechanism. Another challenging issue for particle physics and cosmology is the explanation of the matter-antimatter asymmetry observed in Nature. Among the viable mechanisms, leptogenesis is a simple and well-motivated framework. In this talk we briefly review these aspects, making emphasis on the possibility of linking neutrino physics to the cosmological baryon asymmetry originated from leptogenesis.Comment: 8 pages, 1 table, 1 figure; Based on talk given at the Symposium STARS2011, 1 - 4 May 2011, Havana, Cuba; to be published in the Proceeding

Flowing to four dimensions

We analyze the properties of a model with four-dimensional brane-localized Higgs type potential of a six dimensional scalar field satisfying the Dirichlet boundary condition on the boundary of a transverse two-dimensional compact space. The regularization of the localized couplings generates classical renormalization group running. A tachyonic mass parameter grows in the infrared, in analogy with the QCD gauge coupling in four dimensions. We find a phase transition at a critical value of the bare mass parameter such that the running mass parameter becomes large in the infrared precisely at the compactification scale. Below the critical coupling, the theory is in symmetric phase, whereas above it spontaneous symmetry breaking occurs. Close to the phase transition point there is a very light mode in the spectrum. The massive Kaluza-Klein spectrum at the critical coupling becomes independent of the UV cutoff.Comment: 22 pages, LaTe

Contrasting patterns of selection between MHC I and II across populations of Humboldt and Magellanic penguins

Indexación: Web of ScienceThe evolutionary and adaptive potential of populations or species facing an emerging infectious disease depends on their genetic diversity in genes, such as the major histocompatibility complex (MHC). In birds, MHC class I deals predominantly with intracellular infections (e.g., viruses) and MHC class II with extracellular infections (e.g., bacteria). Therefore, patterns of MHC I and II diversity may differ between species and across populations of species depending on the relative effect of local and global environmental selective pressures, genetic drift, and gene flow. We hypothesize that high gene flow among populations of Humboldt and Magellanic penguins limits local adaptation in MHC I and MHC II, and signatures of selection differ between markers, locations, and species. We evaluated the MHC I and II diversity using 454 next-generation sequencing of 100 Humboldt and 75 Magellanic penguins from seven different breeding colonies. Higher genetic diversity was observed in MHC I than MHC II for both species, explained by more than one MHC I loci identified. Large population sizes, high gene flow, and/or similar selection pressures maintain diversity but limit local adaptation in MHC I. A pattern of isolation by distance was observed for MHC II for Humboldt penguin suggesting local adaptation, mainly on the northernmost studied locality. Furthermore, trans species alleles were found due to a recent speciation for the genus or convergent evolution. High MHC I and MHC II gene diversity described is extremely advantageous for the long term survival of the species.http://onlinelibrary.wiley.com/doi/10.1002/ece3.2502/epd