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Capozziello S.,University of Naples Federico II | Capozziello S.,Complesso Universitario Of Monte Sant Angelo | De Laurentis M.,University of Naples Federico II | De Laurentis M.,Complesso Universitario Of Monte Sant Angelo | And 4 more authors.
International Journal of Geometric Methods in Modern Physics | Year: 2012

We discuss in a critical way the physical foundations of geometric structure of relativistic theories of gravity by the so-called EhlersPiraniSchild formalism. This approach provides a natural interpretation of the observables showing how relate them to General Relativity and to a large class of Extended Theories of Gravity. In particular we show that, in such a formalism, geodesic and causal structures of space-time can be safely disentangled allowing a correct analysis in view of observations and experiment. As specific case, we take into account the case of f(R)-gravity. © 2012 World Scientific Publishing Company.


Giovanna Dainotti M.,Jagiellonian University | Willingale R.,University of Leicester | Capozziello S.,University of Naples Federico II | Capozziello S.,Complesso Universitario Of Monte Sant Angelo | And 3 more authors.
Astrophysical Journal Letters | Year: 2010

Gamma-ray bursts (GRBs) observed up to redshifts z > 8 are fascinating objects to study due to their still unexplained relativistic outburstmechanisms and their possible use to test cosmological models. Our analysis of 77 GRB afterglows with known redshifts revealed a physical subsample of long GRBs with the canonical plateau breaking to power-law light curves with a significant luminosity L X*-break time T a * correlation in the GRB rest frame. This subsample forms approximately the upper envelope of the studied distribution.We have also found a similar relation for a small sample of GRB afterglows that belong to the intermediate class between the short and the long ones. It proves that within the full sample of afterglows there exist physical subclasses revealed here by tight correlations of their afterglowproperties. The afterglowswith regular ("canonical") light curves obey not only the mentioned tight physical scaling, but-for a given T a * -the more regular progenitor explosions lead to preferentially brighter afterglows. © 2010. The American Astronomical Society. All rights reserved.


Basini G.,National Institute of Nuclear Physics, Italy | Capozziello S.,University of Naples Federico II | Capozziello S.,Complesso Universitario Of Monte Sant Angelo | De Laurentis M.,Goethe University Frankfurt | De Laurentis M.,Tomsk State Pedagogical University
International Journal of Geometric Methods in Modern Physics | Year: 2016

Further gravitational massive modes emerge by extending the geometrical sector of Hilbert-Einstein theory in the most general theory including curvature invariants. Besides massless spin-2, also spin-0 and spin-2 massive and ghost fields have to be considered. We investigate the possible detectability of such additional modes by the Large Hadron Collider and calculate the detectable energy density of the spectrum. © 2016 World Scientific Publishing Company.


Chruscinski D.,Nicolaus Copernicus University | Kossakowski A.,University of Naples Federico II | Aniello P.,University of Naples Federico II | Aniello P.,Complesso Universitario Of Monte Sant Angelo | And 4 more authors.
Open Systems and Information Dynamics | Year: 2010

We analyze a class of dynamics of open quantum systems which is governed by the dynamical map mutually commuting at different times. Such evolution may be effectively described via the spectral analysis of the corresponding time-dependent generators. We consider both Markovian and non-Markovian cases. © 2010 World Scientific Publishing Company.


Piedipalumbo E.,University of Naples Federico II | Piedipalumbo E.,Complesso Universitario Of Monte Sant Angelo | Della Moglie E.,University of Genoa | Cianci R.,University of Genoa
International Journal of Modern Physics D | Year: 2015

In the last dozen years, a wide and variegated mass of observational data revealed that the universe is now expanding at an accelerated rate. In the absence of a well-based theory to interpret the observations, cosmography provides information about the evolution of the universe from measured distances, only assuming that the geometry can be described by the Friedmann-Lemaitre-Robertson-Walker metric. In this paper, we perform a high-redshift analysis which allows us to put constraints on the cosmographic parameters up to the fifth-order, thus inducing indirect constraints on any gravity theory. Here, we are interested in the so-called teleparallel gravity theory, f(T). Actually, we use the analytical expressions of the present day values of f(T) and its derivatives as functions of the cosmographic parameters to map the cosmography region of confidences into confidence ranges for f(T) and its derivative. Moreover, we show how these can be used to test some teleparallel gravity models without solving the dynamical equations. Our analysis is based on the Union2 Type Ia supernovae (SNIa) data set, a set of 28 measurements of the Hubble parameter, the Hubble diagram constructed from some gamma ray bursts (GRB) luminosity distance indicators and Gaussian priors on the distance from the baryon acoustic oscillations (BAOs) and the Hubble constant h. To perform our statistical analysis and to explore the probability distributions of the cosmographic parameters, we use the Markov chain Monte Carlo (MCMC) method. © World Scientific Publishing Company.


Piedipalumbo E.,University of Naples Federico II | Piedipalumbo E.,Complesso Universitario Of Monte Sant Angelo | Della Moglie E.,University of Genoa | De Laurentis M.,University of Naples Federico II | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

The understanding of the accelerated expansion of the Universe poses one of the most fundamental questions in physics and cosmology today.Whether or not the acceleration is driven by some form of dark energy, and in the absence of a well-based theory to interpret the observations, many models have been proposed to solve this problem, both in the context of General Relativity and alternative theories of gravity. Actually, a further possibility to investigate the nature of dark energy lies in measuring the dark energy equation of state (EOS), ω, and its time (or redshift) dependence at high accuracy. However, since ω(ζ) is not directly accessible to measurement, reconstruction methods are needed to extract it reliably from observations. Here, we investigate different models of dark energy, described through several parametrizations of the EOS. Our high-redshift analysis is based on the Union2 Type Ia supernovae data set (Suzuki et al.), the Hubble diagram constructed from some gamma-ray bursts luminositydistance indicators, and Gaussian priors on the distance from the baryon acoustic oscillations, and the Hubble constant h (these priors have been included in order to help to break the degeneracies among model parameters). To perform our statistical analysis and to explore the probability distributions of the EOS parameters, we use the Markov Chain Monte Carlo Method. It turns out that, if exact flatness is assumed, the dark energy EOS is evolving for all the parametrizations that we considered.We finally compare our results with the ones obtained by previous cosmographic analyses performed on the same astronomical data sets, showing that the latter ones are sufficient to test and compare the new parametrizations. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.


Dainotti M.G.,Jagiellonian University | Cardone V.F.,University of Molise | Cardone V.F.,University of Naples Federico II | Capozziello S.,University of Naples Federico II | And 3 more authors.
Astrophysical Journal | Year: 2011

Gamma-ray bursts (GRBs) are the most energetic sources in the universe and among the farthest known astrophysical sources. These features make them appealing candidates as standard candles for cosmological applications such that studying the physical mechanisms for the origin of the emission and correlations among their observable properties is an interesting task. We consider here the luminosity L*X andbreak time T*a (hereafter LT) correlation and investigate whether there are systematics induced by selection effects or redshift-dependent calibration. We perform this analysis both for the full sample of 77 Swift GRBs with known redshift and for the subsample of GRBs having canonical X-ray light curves, hereafter called the U0095 sample. We do not find any systematic bias, thus confirming the existence of physical GRB subclasses revealed by tight correlations of their afterglow properties. Furthermore, we study the possibility of applying the LT correlation as a redshift estimator both for the full distribution and for the canonical light curves. The large uncertainties and the non-negligible intrinsic scatter make the results not so encouraging, but there are nevertheless some hints motivating a further analysis with an increased U0095 sample. © 2011. The American Astronomical Society. All rights reserved.


Demianski M.,University of Warsaw | Demianski M.,Williams College | Piedipalumbo E.,University of Naples Federico II | Piedipalumbo E.,Complesso Universitario Of Monte Sant Angelo | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

The explanation of the accelerated expansion of the Universe poses one of the most fundamental questions in physics and cosmology today. If the acceleration is driven by some form of dark energy (DE), and in the absence of a well-based theory to interpret the observations, one can try to constrain the parameters describing the kinematical state of the universe using a cosmographic approach, which is fundamental in that it requires only a minimal set of assumptions, namely to specify the metric, and it does not rely on the dynamical equations for gravity. Our high-redshift analysis allows us to put constraints on the cosmographic expansion up to the fifth order. It is based on the Union2 type Ia Supernovae (SNIa) data set, the Hubble diagram constructed from some gamma ray burst luminosity distance indicators, and Gaussian priors on the distance from the baryon acoustic oscillations, and the Hubble constant h (these priors have been included in order to help break the degeneracies among model parameters). To perform our statistical analysis and to explore the probability distributions of the cosmographic parameters, we use the Markov Chain Monte Carlo method (MCMC). We finally investigate implications of our results for the DE; in particular, we focus on the parametrization of the DE equation of state (EOS). Actually, a possibility of investigating the nature of DE lies in measuring the DE EOS, w, and its time (or redshift) dependence at high accuracy. However, since w(z) is not directly accessible to measurement, reconstruction methods are needed to extract it reliably from observations. Here we investigate different models of DE, described through several parametrizations of the EOS, by comparing the cosmographic and the EOS series. The main results are as follows: (a) even if relying on a mathematical approximate assumption such as the scale factor series expansion in terms of time, cosmography can be extremely useful in assessing dynamical properties of the Universe; (b) the deceleration parameter clearly confirms the present acceleration phase; (c) the MCMC method provides stronger constraints for parameter estimation, in particular for higher order cosmographic parameters (the jerk and the snap), with respect to those presented in the literature; (d) both the estimation of the jerk and the DE parameters reflect the possibility of a deviation from the ΛCDM cosmological model; (e) there are indications that the DE EOS is evolving for all the parametrizations that we considered; (f) the q(z) reconstruction provided by our cosmographic analysis allows for a transient acceleration. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.


Demianski M.,University of Warsaw | Demianski M.,Williams College | Piedipalumbo E.,University of Naples Federico II | Piedipalumbo E.,Complesso Universitario Of Monte Sant Angelo
Monthly Notices of the Royal Astronomical Society | Year: 2011

The correlation between the peak photon energy of the internal spectrum Ep, i and isotropic equivalent radiated energy Eiso (the Amati relation) is explored in a scalar field model of dark energy. Using an updated data set of 109 high-redshift gamma-ray bursts (GRBs), we show that the correlation parameters only weakly depend on the cosmological model. Once the parameters of the Amati relation have been determined, we use this relation to construct a fiducial GRB Hubble diagram (HD) that extends up to redshifts ~8. Moreover, we apply a local regression technique to estimate, in a model-independent way, the distance modulus from the recently updated Union Type Ia supernova (SNIa) sample, containing 557 SNIa spanning the redshift range of 0.015 ≤z≤ 1.55. The derived calibration parameters are used to construct an updated GRB HD, which we call the calibrated GRB HD. We also compare the fiducial and calibrated GRB HDs, which turned out to be fully statistically consistent, thus indicating that they are not affected by any systematic bias induced by the different calibration procedures. This means that the high-redshift GRBs can be used to test different models of dark energy settling the circularity problem. Furthermore, we investigate possible evolutionary effects that might have important influence on our results. Our analysis indicates that the presently available GRB data sets do not show statistically unambiguous evolutionary effect with the cosmological redshift. Finally, we propose another approach to calibrate the GRB relations, by using an approximate luminosity-distance relation, which holds in any cosmological model. We use this calibration of the Amati relation to construct an empirical approximate HD, which we compare with the calibrated GRB HD. We finally investigate the implications of this approach for the high-redshift cosmography. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.


Demianski M.,University of Warsaw | Demianski M.,Williams College | Demianski M.,Institute for Interdisciplinary Studies Artes Liberales | Piedipalumbo E.,University of Naples Federico II | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2011

It has been recently empirically established that some of the directly observed parameters of gamma-ray bursts (GRBs) are correlated with their important intrinsic parameters, such as the luminosity or the total radiated energy. These correlations were derived, tested and used to standardize GRBs, i.e. to derive their luminosity or radiated energy from one or more observables, in order to construct an estimated fiducial Hubble diagram (HD), assuming that radiation propagates in the standard Λ cold dark matter cosmological model. We extend these analyses by considering more general models of dark energy and an updated data set of high-redshift GRBs. We show that the correlation parameters only weakly depend on the cosmological model. Moreover we apply a local regression technique to estimate, in a model-independent way, the distance modulus from the recently updated Type Ia supernova (SNIa) sample containing 307 SNIa, in order to calibrate the GRBs 2D correlations, by considering only GRBs with z≤ 1.4. The derived calibration parameters are used to construct a new GRBs HD, which we call the calibrated GRBs HD. We also compare the estimated and calibrated GRBs HDs. It turns out that for the common GRBs they are fully statistically consistent, thus indicating that both of them are not affected by any systematic bias induced by the different standardizing procedures. We finally apply our methods to calibrate 95 long GRBs with the well-known Amati relation and construct the estimated and calibrated GRBs HD that extends to redshifts z∼ 8. Even in this case there is consistency between these data sets. This means that the high-redshift GRBs can be used to test different models of dark energy. We used the calibrated GRBs HD to constrain our quintessential cosmological model and derived the likelihood values of Ωm and w(0). © 2010 The Authors Monthly Notices of the Royal Astronomical Society © 2010 RAS.

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