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Castorina E.,International School for Advanced Studies | Franca U.,University of Valencia | Lattanzi M.,University of Milan Bicocca | Lesgourgues J.,CERN | And 5 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

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 θ 13, and show that for large θ 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 θ 13. Finally, we perform a forecast for Cosmic Origins Explorer, taken as an example of a future cosmic microwave background experiment, and find that it could improve the limits on the total lepton asymmetry approximately by up to a factor 6.6. © 2012 American Physical Society. Source


Capozziello S.,University of Naples Federico II | Capozziello S.,Complesso Universitario Monte gelo | Saez-Gomez D.,Institute Of Ciencies Of Lespai Ice Csic Ieec
Annalen der Physik | Year: 2012

Birkhoff's theorem is discussed in the frame of f(R) gravity by using its scalar-tensor representation. Modified gravity has become very popular in recent times as it is able to reproduce the unification of inflation and late-time acceleration with no need of a dark energy component or an inflation field. Here, another aspect of modified f(R) gravity is studied, specifically the range of validity of Birkhoff's theorem, compared with another alternative to general relativity, the well-known Brans-Dicke theory. As a novelty, here both theories are studied using a conformal transformation and writing the actions in the Einstein frame, where spherically symmetric solutions are studied using perturbation techniques. The differences between both theories are analyzed as well as the validity of the theorem within the Jordan and Einstein frames, where interesting results are obtained. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Bouhmadi-Lopez M.,University of Lisbon | Capozziello S.,University of Naples Federico II | Capozziello S.,Complesso Universitario Monte gelo | Cardone V.F.,University of Naples Federico II | Cardone V.F.,University of Molise
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

Cosmography is a useful tool to constrain cosmological models, in particular, dark energy models. In the case of modified theories of gravity, where the equations of motion are generally quite complicated, cosmography can contribute to select realistic models without imposing arbitrary choices apriori. Indeed, its reliability is based on the assumptions that the universe is homogeneous and isotropic on large scale and luminosity distance can be "tracked" by the derivative series of the scale factor a(t). We apply this approach to induced gravity brane-world models where an f(R) term is present in the brane effective action. The virtue of the model is to self-accelerate the normal and healthy Dvali-Gabadadze-Porrati branch once the f(R) term deviates from the Hilbert-Einstein action. We show that the model, coming from a fundamental theory, is consistent with the ΛCDM scenario at low redshift. We finally estimate the cosmographic parameters fitting the Union2 TypeIa Supernovae data set and the distance priors from baryon acoustic oscillations and then provide constraints on the present day values of f(R) and its second and third derivatives. © 2010 The American Physical Society. Source


Bloino J.,Normal School of Pisa | Bloino J.,Complesso Universitario Monte gelo | Biczysko M.,Complesso Universitario Monte gelo | Santoro F.,CNR Institute for Chemical and Physical Processes | Barone V.,Normal School of Pisa
Journal of Chemical Theory and Computation | Year: 2010

An effective time-independent approach to compute vibrationally resolved optical spectra from first principles is generalized toward the computation of one-photon electronic spectra induced by either electric or magnetic transition dipoles or by their mutual interaction. These encompass absorption, emission, and circular dichroism spectra. Additionally, the proposed computational scheme is extended to cover a broad range of approximations to evaluate vibronic transitions within both vertical and adiabatic frameworks and to be able to take into account the effects of the temperature. The presented computational tool is integrated into a general purpose computational chemistry package and offers a simple and an easy-to-use way to evaluate one-photon electronic spectra, starting from electronic structure calculations chosen according to the system under study, from fully quantum mechanical descriptions to discrete/continuum quantum mechanical/MM/polarizable continuum models. © 2010 American Chemical Society. Source


Mangano G.,Complesso Universitario Monte gelo | Lizzi F.,Complesso Universitario Monte gelo | Lizzi F.,University of Naples Federico II | Lizzi F.,University of Barcelona | Porzio A.,CNR Institute of Neuroscience
International Journal of Modern Physics A | Year: 2015

Motivated by the Dirac idea that fundamental constants are dynamical variables and by conjectures on quantum structure of space-time at small distances, we consider the possibility that Planck constant h is a time depending quantity, undergoing random Gaussian fluctuations around its measured constant mean value, with variance σ2 and a typical correlation timescale Δt. We consider the case of propagation of a free particle and a one-dimensional harmonic oscillator coherent state, and show that the time evolution in both cases is different from the standard behavior. Finally, we discuss how interferometric experiments or exploiting coherent electromagnetic fields in a cavity may put effective bounds on the value of τ = σ2Δt. © 2015 World Scientific Publishing Company. Source

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