Cosmological constraints on Lorentz violating dark energy

The role of Lorentz invariance as a fundamental symmetry of nature has been lately reconsidered in different approaches to quantum gravity. It is thus natural to study whether other puzzles of physics may be solved within these proposals. This may be the case for the cosmological constant problem. Indeed, it has been shown that breaking Lorentz invariance provides Lagrangians that can drive the current acceleration of the universe without experiencing large corrections from ultraviolet physics. In this work, we focus on the simplest model of this type, called ThetaCDM, and study its cosmological implications in detail. At the background level, this model cannot be distinguished from LambdaCDM. The differences appear at the level of perturbations. We show that in ThetaCDM, the spectrum of CMB anisotropies and matter fluctuations may be affected by a rescaling of the gravitational constant in the Poisson equation, by the presence of extra contributions to the anisotropic stress, and finally by the existence of extra clustering degrees of freedom. To explore these modifications accurately, we modify the Boltzmann code CLASS. We then use the parameter inference code Monte Python to confront ThetaCDM with data from WMAP-7, SPT and WiggleZ. We obtain strong bounds on the parameters accounting for deviations from LambdaCDM. In particular, we find that the discrepancy between the gravitational constants appearing in the Poisson and Friedmann equations is constrained at the level 1.8%.Comment: 17 pages, 5 figure

Cosmological constraints on deviations from Lorentz invariance in gravity and dark matter

We consider a scenario where local Lorentz invariance is violated by the existence of a preferred time direction at every space-time point. This scenario can arise in the context of quantum gravity and its description at low energies contains a unit time-like vector field which parameterizes the preferred direction. The particle physics tests of Lorentz invariance preclude a direct coupling of this vector to the fields of the Standard Model, but do not bear implications for dark matter. We discuss how the presence of this vector and its possible coupling to dark matter affect the evolution of the Universe. At the level of homogeneous cosmology the only effect of Lorentz invariance violation is a rescaling of the expansion rate. The physics is richer at the level of perturbations. We identify three effects crucial for observations: the rescaling of the matter contribution to the Poisson equation, the appearance of an extra contribution to the anisotropic stress and the scale-dependent enhancement of dark matter clustering. These effects result in distinctive features in the power spectra of the CMB and density fluctuations. Making use of the data from Planck and WiggleZ we obtain the most stringent cosmological constraints to date on departures from Lorentz symmetry. Our analysis provides the first direct bounds on deviations from Lorentz invariance in the dark matter sector.Comment: 10 pages, 3 figures, revtex; footnote on isocurvature modes added, discussion on the decoupling of the Standard Model fields from the aether extended, a reference added; version to be published in JCA

Probing neutrino masses with CMB lensing extraction

We evaluate the ability of future cosmic microwave background (CMB) experiments to measure the power spectrum of large scale structure using quadratic estimators of the weak lensing deflection field. We calculate the sensitivity of upcoming CMB experiments such as BICEP, QUaD, BRAIN, ClOVER and PLANCK to the non-zero total neutrino mass M_nu indicated by current neutrino oscillation data. We find that these experiments greatly benefit from lensing extraction techniques, improving their one-sigma sensitivity to M_nu by a factor of order four. The combination of data from PLANCK and the SAMPAN mini-satellite project would lead to sigma(M_nu) = 0.1 eV, while a value as small as sigma(M_nu) = 0.035 eV is within the reach of a space mission based on bolometers with a passively cooled 3-4 m aperture telescope, representative of the most ambitious projects currently under investigation. We show that our results are robust not only considering possible difficulties in subtracting astrophysical foregrounds from the primary CMB signal but also when the minimal cosmological model (Lambda Mixed Dark Matter) is generalized in order to include a possible scalar tilt running, a constant equation of state parameter for the dark energy and/or extra relativistic degrees of freedom.Comment: 13 pages, 4 figures. One new figure and references added. Version accepted for publicatio

Cosmological lepton asymmetry with a nonzero mixing angle \theta_{13}

While the baryon asymmetry of the Universe is nowadays well measured by cosmological observations, the bounds on the lepton asymmetry in the form of neutrinos are still significantly weaker. We place limits on the relic neutrino asymmetries using some of the latest cosmological data, taking into account the effect of flavor oscillations. We present our results for two different values of the neutrino mixing angle \theta_{13}, and show that for large \theta_{13} the limits on the total neutrino asymmetry become more stringent, diluting even large initial flavor asymmetries. In particular, we find that the present bounds are still dominated by the limits coming from Big Bang Nucleosynthesis, while the limits on the total neutrino mass from cosmological data are essentially independent of \theta_{13}. Finally, we perform a forecast for COrE, taken as an example of a future CMB experiment, and find that it could improve the limits on the total lepton asymmetry approximately by up to a factor 6.6.Comment: 11 pages, 7 figures, 5 tables. v2: updated COrE specifications. v3: matches Phys. Rev. D accepted versio

On the Entropy and the Density Matrix of Cosmological Perturbations

We look at the transition to the semiclassical behaviour and the decoherence process for the inhomogeneous perturbations in the inflationary universe. Two different decoherence mechanisms appear: one dynamical, accompanied with a negligible, if at all, entropy gain, and the other, effectively irreversible dephasing, due to a rapid variation in time of the off-diagonal density matrix elements in the post-inflationary epoch. We thus settle the discrepancies in the entropy content of perturbations evaluated by different authors.Comment: LaTeX2e with the epsf packag

Constraints on the Neutrino Mass from SZ Surveys

Statistical measures of galaxy clusters are sensitive to neutrino masses in the sub-eV range. We explore the possibility of using cluster number counts from the ongoing PLANCK/SZ and future cosmic-variance-limited surveys to constrain neutrino masses from CMB data alone. The precision with which the total neutrino mass can be determined from SZ number counts is limited mostly by uncertainties in the cluster mass function and intracluster gas evolution; these are explicitly accounted for in our analysis. We find that projected results from the PLANCK/SZ survey can be used to determine the total neutrino mass with a (1\sigma) uncertainty of 0.06 eV, assuming it is in the range 0.1-0.3 eV, and the survey detection limit is set at the 5\sigma significance level. Our results constitute a significant improvement on the limits expected from PLANCK/CMB lensing measurements, 0.15 eV. Based on expected results from future cosmic-variance-limited (CVL) SZ survey we predict a 1\sigma uncertainty of 0.04 eV, a level comparable to that expected when CMB lensing extraction is carried out with the same experiment. A few percent uncertainty in the mass function parameters could result in up to a factor \sim 2-3 degradation of our PLANCK and CVL forecasts. Our analysis shows that cluster number counts provide a viable complementary cosmological probe to CMB lensing constraints on the total neutrino mass.Comment: Replaced with a revised version to match the MNRAS accepted version. arXiv admin note: text overlap with arXiv:1009.411

Forecasting neutrino masses from galaxy clustering in the Dark Energy Survey combined with the Planck Measurements

We study the prospects for detecting neutrino masses from the galaxy angular power spectrum in photometric redshift shells of the Dark Energy Survey (DES) over a volume of 20 (Gpc/h)^3 combined with the Cosmic Microwave Background (CMB) angular fluctuations expected to be measured from the Planck satellite. We find that for a Lambda-CDM concordance model with 7 free parameters in addition to a fiducial neutrino mass of M_nu = 0.24 eV, we recover from DES &Planck the correct value with uncertainty of +- 0.12 eV (95 % CL), assuming perfect knowledge of the galaxy biasing. If the fiducial total mass is close to zero, then the upper limit is 0.11 eV (95 % CL). This upper limit from DES &Planck is over 3 times tighter than using Planck alone, as DES breaks the parameter degeneracies in a CMB-only analysis. The analysis utlilizes spherical harmonics up to 300, averaged in bin of 10 to mimic the DES sky coverage. The results are similar if we supplement DES bands (grizY) with the VISTA Hemisphere Survey (VHS) near infrared band (JHK). The result is robust to uncertainties in non-linear fluctuations and redshift distortions. However, the result is sensitive to the assumed galaxy biasing schemes and it requires accurate prior knowledge of the biasing. To summarize, if the total neutrino mass in nature greater than 0.1eV, we should be able to detect it with DES &Planck, a result with great importance to fundamental Physics.Comment: Submitted to MNRAS, 9 pages, 10 figure

Cosmological measurement of neutrino mass in the presence of leptonic asymmetry

We show that even the smallest neutrino mass consistent with the Super--Kamiokande data is relevant for cosmological models of structure formation and cosmic microwave background (CMB) anisotropies, provided that a relic neutrino asymmetry exists. We calculate the precision with which a 0.07 eV neutrino mass could be extracted from CMB anisotropy and large-scale structure data by the future Planck satellite and Sloan Digital Sky Survey. We find that such a mass can be detected, assuming a large relic neutrino asymmetry still allowed by current experimental data. This measurement of the absolute value of the neutrino mass would be crucial for our understanding of neutrino models.Comment: 8 pages, 2 PS figures, version to be publishe

Constrained analytical interrelations in neutrino mixing

Hermitian squared mass matrices of charged leptons and light neutrinos in the flavor basis are studied under general additive lowest order perturbations away from the tribimaximal (TBM) limit in which a weak basis with mass diagonal charged leptons is chosen. Simple analytical expressions are found for the three measurable TBM-deviants in terms of perturbation parameters appearing in the neutrino and charged lepton eigenstates in the flavor basis. Taking unnatural cancellations to be absent and charged lepton perturbation parameters to be small, interrelations are derived among masses, mixing angles and the amount of CP-violation.Comment: To be published in the Springer Proceedings in the Physics Series under the heading of the XXI DAE-BRNS Symposium (Guwahati, India

From Wave Geometry to Fake Supergravity

The `Wave Geometry' equation of the pre-WWII Hiroshima program is also the key equation of the current `fake supergravity' program. I review the status of (fake) supersymmetric domain walls and (fake) pseudo-supersymmetric cosmologies. An extension of the domain-wall/cosmology correspondence to a triple correspondence with instantons shows that `pseudo-supersymmetry' has another interpretation as Euclidean supersymmetry.Comment: 14 pages. Minor Revisions to original. To appear in proceedings of the 5th International Symposium on Quantum Theory and Symmetries (QTS5), Vallodolid, July 2007. in version