Dark energy in motion

Recent large-scale peculiar velocity surveys suggest that large matter volumes could be moving with appreciable velocity with respect to the CMB rest frame. If confirmed, such results could conflict with the Cosmological Principle according to which the matter and CMB rest frames should converge on very large scales. In this work we explore the possibility that such large scale bulk flows are due, not to the motion of matter with respect to the CMB, but to the flow of dark energy with respect to matter. Indeed, when dark energy is moving, the usual definition of the CMB rest frame as that in which the CMB dipole vanishes is not appropriate. We find instead that the dipole vanishes for observers at rest with respect to the cosmic center of mass, i.e. in motion with respect to the background radiation.Comment: 9 pages, 1 figure. Essay selected for "Honorable Mention" in the 2006 Awards for Essays on Gravitation (Gravity Research Foundation

Solution to the Isotropy Problem for Cosmological Hidden Vector Models

Gauge bosons associated to new gauge symmetries under which the standard model particles are not charged are predicted in many extensions of the standard model of particles and interactions. We show that under very general conditions, the average energy-momentum tensor of these rapidly oscillating vector fields is isotropic for any locally inertial observer. This result has a fundamental importance in order to consider coherent vector fields as a viable alternative to support models of dark matter, dark energy or inflation.Comment: 4 pages, 1 figure. Contributed to the 9th Patras Workshop on Axions, WIMPs and WISPs, Mainz, June 24-28, 201

Dark matter origin of the gamma ray emission from the galactic center observed by HESS

We show that the gamma ray spectrum observed with the HESS array of Cherenkov telescopes coming from the Galactic Center (GC) region and identified with the source HESS J1745-290, is well fitted by the secondary photons coming from dark matter (DM) annihilation over a diffuse power-law background. The amount of photons and morphology of the signal localized within a region of few parsecs, require compressed DM profiles as those resulting from baryonic contraction, which offer $\sim 10^3$ enhancements in the signal over DM alone simulations. The fitted background from HESS data is consistent with recent Fermi-LAT observations of the same region.Comment: 4 pages, 3 figures. Improved resolution analysi

Spectral Study of the HESS J1745-290 Gamma-Ray Source as Dark Matter Signal

We study the main spectral features of the gamma-ray fluxes observed by the High Energy Stereoscopic System (HESS) from the J1745-290 Galactic Center source during the years 2004, 2005 and 2006. In particular, we show that these data are well fitted as the secondary gamma-rays photons generated from dark matter annihilating into Standard Model particles in combination with a simple power law background. We present explicit analyses for annihilation in a single standard model particle-antiparticle pair. In this case, the best fits are obtained for the u and d quark-antiquark channels and for the WW and ZZ gauge bosons, with background spectral index compatible with the Fermi-Large Area Telescope (LAT) data from the same region. The fits return a heavy WIMP, with a mass above 10 TeV approximately, but well below the unitarity limit for thermal relic annihilation.Comment: 15 pages, 14 figures. arXiv admin note: text overlap with arXiv:1204.065

Branon dark matter: an introduction

This is a brief introduction to branon physics and its role in the dark matter problem. We pay special attention to the phenomenological consequences, both in high-energy particle physics experiments and in astrophysical and cosmological observations.Comment: 5 pages, 3 figures. To appear in the proceedings of the 10th international symposium on Particles, Strings and Cosmology, PASCOS 04, Boston, August 16-22, 200

Some model-independent phenomenological consequences of flexible brane worlds

In this work we will review the main properties of brane-world models with low tension. Starting from very general principles, it is possible to obtain an effective action for the relevant degrees of freedom at low energies (branons). Using the cross sections for high-energy processes involving branons, we set bounds on the different parameters appearing in these models. We also show that branons provide a WIMP candidate for dark matter in a natural way. We consider cosmological constraints on its thermal and non-thermal relic abundances. We derive direct detection limits and compare those limits with the preferred parameter region in the case in which the EGRET excess in the diffuse galactic gamma rays is due to dark matter annihilation. Finally we will discuss the constraints coming from the precision tests of the Standard Model and the muon anomalous magnetic moment.Comment: 10 pages, 6 figures. Contribution to the Proceedings of the Second International Conference on Quantum Theories and Renormalization Group in Gravity and Cosmology, IRGAC 2006, Barcelona, 11-15 July, 200

Phenomenological implications of brane world scenarios with low tension

The recent proposal of theories with compactified large extra dimensions is reviewed. We pay especial attention to brane world models with low tension where the only relevant degrees of freedom at low energies are the Standard Model (SM) particles and the branons, which are transversal brane oscillations. By using an effective Lagrangian, we study some phenomenological consequences of these scenarios in a model independent way.Comment: 8 pages, LaTeX uses aipproc, 2 figures. Talk given by A. Dobado in the X Mexican School of Particles and Fields, Playa del Carmen, Mexico, 200