Publications (122)259.61 Total impact
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ABSTRACT: Dark Matter is essential for structure formation in the late Universe so it must be stable on cosmological time scales. But how stable exactly? Only assuming decays into relativistic particles, we report an otherwise model independent bound on the lifetime of Dark Matter using current cosmological data. Since these decays affect only the low$\ell$ multipoles of the CMB, the Dark Matter lifetime is expected to correlate with the tensortoscalar ratio $r$ as well as curvature $\Omega_k$. We consider two models, including $r$ and $r+\Omega_k$ respectively, versus data from Planck, WMAP, WiggleZ and Baryon Acoustic Oscillations, with or without the BICEP2 data (if interpreted in terms of primordial gravitational waves). This results in a lower bound on the lifetime of CDM given by 160Gyr (without BICEP2) or 200Gyr (with BICEP2) at 95% confidence level.07/2014;  [Show abstract] [Hide abstract]
ABSTRACT: Big Bang Nucleosynthesis (BBN) relates key cosmological parameters to the primordial abundance of light elements. In this paper, we point out that the recent observations of Cosmic Microwave Background anisotropies by the Planck satellite and by the BICEP2 experiment constrain these parameters with such a high level of accuracy that the primordial deuterium abundance can be inferred with remarkable precision. For a given cosmological model, one can obtain independent information on nuclear processes in the energy range relevant for BBN, which determine the eventual ^2H/H yield. In particular, assuming the standard cosmological model, we show that a combined analysis of Planck data and of recent deuterium abundance measurements in metalpoor damped Lymanalpha systems provides independent information on the cross section of the radiative capture reaction d(p,\gamma)^3He converting deuterium into helium. Interestingly, the result is higher than the values suggested by a fit of present experimental data in the BBN energy range (10  300 keV), whereas it is in better agreement with ab initio theoretical calculations, based on models for the nuclear electromagnetic current derived from realistic interactions. Due to the correlation between the rate of the above nuclear process and the effective number of neutrinos Neff, the same analysis points out a Neff>3 as well. We show how this observation changes when assuming a nonminimal cosmological scenario. We conclude that further data on the d(p,\gamma)^3He cross section in the few hundred keV range, that can be collected by experiments like LUNA, may either confirm the low value of this rate, or rather give some hint in favour of nexttominimal cosmological scenarios.04/2014;  [Show abstract] [Hide abstract]
ABSTRACT: The most general case of selfinduced neutrino flavor evolution is described by a set of kinetic equations for a dense neutrino gas evolving both in space and time. Solutions of these equations have been typically worked out assuming that either the time (in the corecollapse supernova environment) or space (in the early universe) homogeneity in the initial conditions is preserved through the evolution. In these cases one can gauge away the homogeneous variable and reduce the dimensionality of the problem. In this paper we investigate if small deviations from an initial postulated homogeneity can be amplified by the interacting neutrino gas, leading to a new flavor instability. To this end, we consider a simple two flavor isotropic neutrino gas evolving in time, and initially composed by only $\nu_e$ and $\bar\nu_e$ with equal densities. In the homogeneous case, this system shows a bimodal instability in the inverted mass hierarchy scheme, leading to the well studied flavor pendulum behavior. This would lead to periodic pair conversions $\nu_e \bar\nu_e \leftrightarrow \nu_x \bar\nu_x$. To break space homogeneity, we introduce small amplitude spacedependent perturbations in the matter potential. By Fourier transforming the equations of motion with respect to the space coordinate, we then numerically solve a set of coupled equations for the different Fourier modes. We find that even for arbitrarily tiny inhomogeneities, the system evolution runs away from the stable pendulum behavior: the different modes are excited and the system evolves towards flavor equilibrium. We finally comment on the role of a time decaying neutrino background density in weakening these results.Physical Review D 03/2014; 89(073017). · 4.69 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The PTOLEMY experiment (Princeton Tritium Observatory for Light, EarlyUniverse, MassiveNeutrino Yield) aims to achieve the sensitivity required to detect the relic neutrino background through a combination of a large area surfacedeposition tritium target, MACE filter methods, cryogenic calorimetry, and RF tracking and timeofflight systems. A smallscale prototype is in operation at the Princeton Plasma Physics Laboratory with the goal of validating the technologies that would enable the design of a 100 gram PTOLEMY. With precision calorimetry in the prototype setup, the limitations from quantum mechanical and Doppler broadening of the tritium target for different substrates will be measured, including graphene substrates. Beyond relic neutrino physics, sterile neutrinos contributing to the dark matter in the universe are allowed by current constraints on partial contributions to the number of active neutrino species in thermal equilibrium in the early universe. The current PTOLEMY prototype is expected to have unique sensitivity in the search for sterile neutrinos with electronflavor content for masses of 0.11keV, where less stringent, 10eV, energy resolution is required. The search for sterile neutrinos with electronflavor content with the 100g PTOLEMY is expected to reach the level $U_{e4}^2$ of $10^{4}$$10^{6}$, depending on the sterile neutrino mass.07/2013;  [Show abstract] [Hide abstract]
ABSTRACT: We perform a study of the flavor evolution in the early universe of a multiflavor activesterile neutrino system with parameters inspired by the shortbaseline neutrino anomalies. In a neutrinosymmetric bath a “thermal” population of the sterile state would quickly grow, but in the presence of primordial neutrino asymmetries a selfsuppression as well as a resonant sterile neutrino production can take place, depending on temperature and chosen parameters. In order to characterize these effects, we go beyond the usual average momentum and singlemixing approximations and consider a multimomentum and multiflavor treatment of the kinetic equations. We find that the enhancement obtained in this case with respect to the average momentum approximation is significant, up to ∼20% of a degree of freedom. Such a detailed and computationally demanding treatment further raises the asymmetry values required to significantly suppress the sterile neutrino production, up to Lν≳O(102). For such asymmetries, however, the activesterile flavor conversions happen so late that significant distortions are produced in the electron (anti)neutrino spectra. The larger Lν, the more the impact of these distortions takes over as a dominant cosmological effect, notably increasing the 4He abundance in primordial nucleosynthesis. The standard expression of the primordial yields in terms of the effective number of neutrinos and asymmetries is also greatly altered. We numerically estimate the magnitude of such effects for a few representative cases and comment on the implications for current cosmological measurements.Physical Review D 04/2013; 87(7). · 4.69 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The cosmic energy density in the form of radiation before and during Big Bang Nucleosynthesis is typically parameterized in terms of the effective number of neutrinos NeffNeff, and it is a key parameters in cosmological models slightly more general than the successful minimal ΛCDM scenario. This quantity, in case of no extra degrees of freedom, depends upon the chemical potential and the temperature characterizing the three active neutrino distributions, as well as by their possible nonthermal features. We summarize here the results of a recent analysis to determine the BBN bound on NeffNeff from primordial neutrino–antineutrino asymmetries, with a careful treatment of the dynamics of neutrino oscillations, and considering quite a wide range for the total lepton number in the neutrino sector, ην=ηνe+ηνμ+ηντην=ηνe+ηνμ+ηντ and the initial electron neutrino asymmetry ηνein. Comparing these results with the forthcoming measurement of NeffNeff by the Planck satellite will give insight on the nature of the radiation content of the universe.Nuclear Physics B  Proceedings Supplements 04/2013; s 237–238:253–255. · 0.88 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Light sterile neutrinos can be excited by oscillations with active neutrinos in the early universe. Their properties can be constrained by their contribution as extraradiation, parameterized in terms of the effective number of neutrino species N_ eff, and to the universe energy density today \Omega_\nu h^2. Both these parameters have been measured to quite a good precision by the Planck satellite experiment. We use this result to update the bounds on the parameter space of (3+1) sterile neutrino scenarios, with an activesterile neutrino mass squared splitting in the range (10^{5}  10^2 ) eV^2. We consider both normal and inverted mass orderings for the active and sterile states. For the first time we take into account the possibility of two nonvanishing activesterile mixing angles. We find that the bounds are more stringent than those obtained in laboratory experiments. This leads to a strong tension with the shortbaseline hints of light sterile neutrinos. In order to relieve this disagreement, modifications of the standard cosmological scenario, e.g. large primordial neutrino asymmetries, are required.Physics Letters B 03/2013; 726(1). · 4.57 Impact Factor 
Article: Neutrino Cosmology
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ABSTRACT: Preface; 1. The basics of neutrino physics; 2. Overview of the standard cosmological model; 3. Neutrino in the early ages; 4. Neutrinos in the MeV age; 5. Neutrinos in the CMB epoch; 6. The recent times: neutrinos and structure formation; 7. Cosmological neutrinos today; Index.Neutrino Cosmology, by Julien Lesgourgues , Gianpiero Mangano , Gennaro Miele , Sergio Pastor, Cambridge, UK: Cambridge University Press, 2013. 02/2013;  [Show abstract] [Hide abstract]
ABSTRACT: We study symmetry of spacetime in the presence of a minimally coupled scalar field interacting with a Kalb–Ramond tensor fields in a homogeneous but initially anisotropic universe. The analysis is performed for the two relevant cases of a pure cosmological constant and a minimal quadratic, renormalizable, interaction term. In both cases, due to expansion, a complete spatial symmetry restoration is dynamically obtained.Modern Physics Letters A 05/2012; 20(08). · 1.11 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: 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.Physical review D: Particles and fields 04/2012;  [Show abstract] [Hide abstract]
ABSTRACT: In the framework of a novel approach to the dynamics of nuclei and large collections of nucleons, which fully exploits the coherent interaction among π’s, nucleons and Δ’s, we derive a new equation of state for neutronic matter. By introducing it in the TolmanOppenheimerVolkof equations we derive the masses and radii of neutron stars as a function of the central density. We obtain a maximum mass Mmax≃2.7 Mʘ and a minimum period of rotation Tmin=0.8 msec.International Journal of Modern Physics D 01/2012; 04(04). · 1.03 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: In the framework of the ConnesLott model based on noncommutative geometry, the basic features of a gauge theory in the presence of gravity are reviewed, in order to show the possible physical relevance of this scheme for inflationary cosmology. These models naturally contain at least two scalar fields, interacting with each other whenever more than one fermion generation is assumed. In this paper we propose to investigate the behavior of these two fields (one of which represents the distance between the copies of a twosheeted spacetime) in the early stages of the universe evolution. In particular the simplest Abelian model, which preserves the main characteristics of more complicate gauge theories, is considered and the corresponding inflationary dynamics is studied. We find that a chaotic inflation is naturally favored, leading to a field configuration in which no symmetry breaking occurs and the final distance between the two sheets of spacetime is smaller the greater the number of e fold in each sheet.International Journal of Modern Physics A 01/2012; 11(16). · 1.13 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We report on the status of primordial nucleosynthesis in light of recent results on CMB anisotropies from WMAP experiment. Theoretical estimates for nuclei abundances, along with the corresponding uncertainties, are evaluated using a new numerical code, where all nuclear rates usually considered have been updated using the most recent available data. Moreover, additional processes neglected in previous calculations have been included. The combined analysis of CMB and primordial nucleosynthesis prediction for Deuterium gives an effective number of relativistic degrees of freedom in good agreement with the simplest scenario of three nondegenerate neutrinos. Our findings seem to point out possible systematics affecting 4He mass fraction measurements, or the effect of exotic physics, like a slightly degenerate relic neutrino background.International Journal of Modern Physics A 01/2012; 19(26). · 1.13 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A method to measure the low energy nuclear recoils induced by weakly interactive massive particles (WIMPs) has been achieved by means of an ultra pure Liquid Argon detector. The simultaneous observation of scintillation and ionization occurring in the liquid Argon allow to obtain a very high rejection power against background sources. The first preliminary upper bounds on WIMP parameters obtained with a small 2.3 liter test chamber with an accumulated fiducial exposure of about 100 kg⋅day at the Gran Sasso Underground Laboratory is reported. This supports the validity of this method for a larger detector presently under construction with correspondingly increased sensitivities.Nuclear Physics B  Proceedings Supplements 12/2011; 221:53–56. · 0.88 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We analyze the possibility to extend the Connes and Lott reformulation of the standard model to larger unified gauge groups. Noncommutative geometry imposes very stringent constraints on the possible theories, and remarkably, the analysis seems to suggest that no larger gauge groups are compatible with the noncommutative structure, unless one enlarges the fermionic degrees of freedom, namely the number of particles.Modern Physics Letters A 11/2011; 11(32n33). · 1.11 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We extend a previous analysis concerning cosmological fluids with generalized equations of state in order to study inflationary scenarios. In the framework of the slowroll approximation we find the expressions for the perturbation parameters ε, η and the density perturbation spectra in terms of the adiabatic index γ(a) as a function of the universe scale factor. This connection allows one to find straightforwardly γ(a) corresponding, for example, to the simplest chaotic model and to the HarrisonZeldovich potential and shows its capability to be applied to more complicated situations. Finally, we use this description to develop a new approach to the early universe dynamics, based on a 1/N expansion, where N is the efold number. To this end, we introduce a set of suitable dimensionless variables and show that at the zeroth order in /1N, an improved slowroll approximation is obtained.Modern Physics Letters A 11/2011; 10(27). · 1.11 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: In a recent paper we pointed out the presence of extra fermionic degrees of freedom in a chiral gauge theory based on Connes' noncommutative geometry. Here we propose a mechanism which provides a high mass to these mirror states, so that they decouple from low energy physics.Modern Physics Letters A 11/2011; 13(03). · 1.11 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We consider radiative electromagnetic corrections, at order α, to the process at finite density and temperature. This process represents one of the main contributions to the cooling of stellar environments in the late stages of star evolution. We find that these corrections affect the energy loss rate by a factor (41)% with respect to the tree level estimate, in the temperature and density ranges where the neutrino pair production via e+e annihilation is the most efficient cooling mechanism.Modern Physics Letters A 11/2011; 17(08). · 1.11 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We consider a model of interacting cosmological constant/quintessence, where dark matter and dark energy behave as, respectively, two coexisting phases of a fluid, a thermally excited Bose component and a condensate, respectively. In a simple phenomenological model for the dark components interaction we find that their energy density evolution is strongly coupled during the universe evolution. This feature provides a possible way out for the coincidence problem affecting many quintessence models.Modern Physics Letters A 11/2011; 18(12). · 1.11 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: In the curvaton scenario, residual isocurvature perturbations can be imprinted in the cosmic neutrino component after the decay of the curvaton field, implying in turn a nonzero chemical potential in the neutrino distribution. We study the constraints that future experiments like Planck, SPIDER or CMBPol will be able to put on the amplitude of isocurvature perturbations in the neutrino component. We express our results in terms of the square root \gamma of the nonadiabaticity parameter \alpha and of the extra relativistic degrees of freedom \Delta N_eff. Assuming a fiducial model with purely adiabatic fluctuations, we find that Planck (SPIDER) will be able to put the following upper limits at the 1sigma level: \gamma < 5.3x10^3 (1.2x10^2) and \Delta N_eff < 0.16 (0.40) . CMBPol will further improve these constraints to \gamma < 1.5x10^3 and \Delta N_eff < 0.043. Finally, we recast these bounds in terms of the background neutrino degeneracy parameter \xi\ and the corresponding perturbation amplitude \sigma_\xi, and compare with the bounds on \xi\ that can be derived from Big Bang Nucleosynthesis.Physical review D: Particles and fields 11/2011; 85(4).
Publication Stats
3k  Citations  
259.61  Total Impact Points  
Top Journals
Institutions

1992–2014

INFN  Istituto Nazionale di Fisica Nucleare
Frascati, Latium, Italy


1991–2012

University of Naples Federico II
 Department of Physical Sciences
Napoli, Campania, Italy


2006

Università degli Studi dell'Aquila
 Department of Chemistry, Chemical Engineering and Materials
Aquila, Abruzzo, Italy 
Syracuse University
Syracuse, New York, United States


2004

University of Pavia
 Department of Physics
Pavia, Lombardy, Italy


1997–2004

Policlinico Federico II di Napoli
Napoli, Campania, Italy


2000

University of Oxford
 Department of Physics
Oxford, ENG, United Kingdom


1994

University of Cambridge
 Department of Applied Mathematics and Theoretical Physics
Cambridge, England, United Kingdom
