Results for "Salvatore Capozziello"

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A bridge between unified cosmic history by $f(R)$-gravity and BIonic systemFeb 19 2015Recently, the cosmological deceleration-acceleration transition redshift in $f(R)$ gravity has been considered in order to address consistently the problem of cosmic evolution. It is possible to show that the deceleration parameter changes sign at a given ... More
Axially symmetric solutions in f(R)-gravityDec 29 2009May 29 2010Axially symmetric solutions for f (R)-gravity can be derived starting from exact spherically sym- metric solutions achieved by Noether symmetries. The method takes advantage of a complex coordi- nate transformation previously developed by Newman and Janis ... More
Scalar-Tensor Teleparallel Wormholes by Noether SymmetriesAug 12 2016A gravitational theory of a scalar field non-minimally coupled with torsion and boundary term is considered with the aim to construct Lorentzian wormholes. Geometrical parameters including shape and redshift functions are obtained for these solutions. ... More
Self-acceleration and matter content in bicosmology from Noether SymmetriesOct 24 2016We consider the existence of Noether symmetries in bigravity cosmologies in order to constrain the material content minimally coupled to the gravitational sector that we are not inhabiting. Interestingly, a Noether symmetry not only constrain the matter ... More
Newtonian limit of Extended Theories of GravityDec 17 2004Newtonian limit of Extended Theories of Gravity (in particular, higher--order and scalar--tensor theories) is theoretically discussed taking into account recent observational and experimental results.
Some aspects of the cosmological conformal equivalence between ``Jordan Frame'' and ``Einstein Frame''Dec 18 1996The conformal equivalence between Jordan frame and Einstein frame can be used in order to search for exact solutions in general theories of gravity in which scalar fields are minimally or nonminimally coupled with geometry. In the cosmological arena a ... More
A Time-dependent Cosmological Constant PhenomenologyMay 29 1996We construct a cosmological toy model in which a step-function ``cosmological constant'' is taken into consideration beside ordinary matter. We assume that $\Lambda$ takes two values depending on the epoch, and matter goes from a radiation dominated era ... More
Curvature QuintessenceJan 10 2002The issues of quintessence and cosmic acceleration can be discussed in the framework of higher order theories of gravity. We can define effective pressure and energy density directly connected to the Ricci scalar of curvature of a generic fourth order ... More
Noether symmetries in Symmetric Teleparallel CosmologyMay 22 2019We consider a general theory of all possible quadratic, first-order derivative terms of the non-metricity tensor in the framework of Symmetric Teleparallel Geometry. We apply the Noether Symmetry Approach to classify those models that are invariant under ... More
Solar system and equivalence principle constraints on f(R) gravity by chameleon approachDec 14 2007Mar 30 2008We study constraints on f(R) dark energy models from solar system experiments combined with experiments on the violation of equivalence principle. When the mass of an equivalent scalar field degree of freedom is heavy in a region with high density, a ... More
Dark energy from entanglement entropyMar 06 2013We show that quantum decoherence, in the context of observational cosmology, can be connected to the cosmic dark energy. The decoherence signature could be characterized by the existence of quantum entanglement between cosmological eras. As a consequence, ... More
Decoherence, Entanglement and Cosmic EvolutionJun 08 2013The possible imprint of quantum decoherence, in the framework of cosmology, is here investigated. Particular attention is paid to the observational fact that entanglement could lead to the interaction of different eras of cosmic evolution. The role played ... More
Astrophysical flows near $f(T)$ gravity black holesFeb 10 2016Apr 29 2016In this paper, we study the accretion process for fluids flowing near a black hole in the context of $f(T)$ teleparallel gravity. Specifically, by performing a dynamical analysis by a Hamiltonian system, we are able to find the sonic points. After that, ... More
Newtonian limit of String-Dilaton GravityJan 15 2003We study the weak-field limit of string-dilaton gravity and derive corrections to the Newtonian potential which strength directly depends on the self interaction potential and the nonminimal coupling of the dilaton scalar field. We discuss also possible ... More
The fate of Schwarzschild-de Sitter Black Holes in $f(R)$ gravityFeb 01 2016The semiclassical effects of antievaporating black holes can be discussed in the framework of $f(R)$ gravity. In particular, the Bousso-Hawking-Nojiri-Odinstov antievaporation instability of degenerate Schwarzschild-de Sitter black holes (the so called ... More
Hojman Symmetry Approach for Scalar-Tensor CosmologyFeb 28 2015Scalar-tensor Cosmologies can be dealt under the standard of the Hojman conservation theorem that allows to fix the form of the coupling $F(\phi)$, of the potential $V(\phi)$ and to find out exact solutions for related cosmological models. Specifically, ... More
Noether symmetries and duality transformations in cosmologyFeb 29 2016Aug 18 2016We discuss the relation between Noether (point) symmetries and discrete symmetries for a class of minisuperspace cosmological models. We show that when a Noether symmetry exists for the gravitational Lagrangian then there exists a coordinate system in ... More
The Weak Field Limit of Fourth Order GravitySep 17 2010We discuss Newtonian and the post-Newtonian limits of Fourth Order Gravity Theories pointing out, in details, their resemblances and differences with respect to General Relativity. Particular emphasis is placed on the exact solutions and methods used ... More
Dawn of the dark: unified dark sectors and the EDGES Cosmic Dawn 21-cm signalJul 10 2019While the origin and composition of dark matter and dark energy remains unknown, it is possible that they might represent two manifestations of a single entity, as occurring in unified dark sector models. On the other hand, advances in our understanding ... More
A cosmological independent calibration of the Ep,i-Eiso correlation for Gamma Ray BurstsMar 27 2010The relation connecting the emitted isotropic energy and the rest-frame peak energy of the \nuF\nu spectra of Gamma-Ray Bursts (the Amati relation), strictly depends on the cosmological model, so we need a method to obtain an independent calibration of ... More
On the well formulation of the Initial Value Problem of metric--affine $f(R)$-gravityJan 20 2009Apr 23 2009We study the well formulation of the initial value problem of f(R)-gravity in the metric-affine formalism. The problem is discussed in vacuo and in presence of perfect-fluid matter, Klein-Gordon and Yang-Mills fields. Adopting Gaussian normal coordinates, ... More
Noether Symmetry Approach in $f(T,B)$ teleparallel cosmologyDec 05 2016We consider the cosmology derived from $f(T,B)$ gravity where $T$ is the torsion scalar and $B=\frac{2}{e}\partial_{\mu}(e T^{\mu})$ a boundary term. In particular we discuss how it is possible to recover, under the same standard, the teleparallel $f(T)$ ... More
Cosmographic transition redshift in $f(R)$ gravityNov 10 2014We propose a strategy to infer the transition redshift $z_{da}$, which characterizes the passage through the universe decelerated to accelerated phases, in the framework $f(R)$ gravities. To this end, we numerically reconstruct $f(z)$, i.e. the corresponding ... More
Screening mechanisms in hybrid metric-Palatini gravityDec 08 2017Apr 11 2018We investigate the efficiency of screening mechanisms in the hybrid metric-Palatini gravity. The value of the field is computed around spherical bodies embedded in a background of constant density. We find a thin shell condition for the field depending ... More
External stability for Spherically Symmetric Solutions in Lorentz Breaking Massive GravityJul 17 2014Oct 22 2014We discuss spherically symmetric solutions for point-like sources in Lorentz-breaking massive gravity theories. This analysis is valid for St\"uckelberg's effective field theory formulation, for Lorentz Breaking Massive Bigravity and general extensions ... More
Extended Theories of Gravity and their Cosmological and Astrophysical ApplicationsJun 08 2007Jul 16 2007We review Extended Theories of Gravity in metric and Palatini formalism pointing out their cosmological and astrophysical application. The aim is to propose an alternative approach to solve the puzzles connected to dark components.
The emission of Gamma Ray Bursts as a test-bed for modified gravityApr 15 2015Sep 19 2015The extreme physical conditions of Gamma Ray Bursts can constitute a useful observational laboratory to test theories of gravity where very high curvature regimes are involved. Here we propose a sort of curvature engine capable, in principle, of explaining ... More
Chiral Structures Under the Standard of Orthogonal GroupsJan 19 2007General features of microscopic and macroscopic chiral structures can be discussed under the standard of orthogonal group theory. Configuration space of systems, not physical space, is taken into account. This change of perspective allows to overcome ... More
Spiral Galaxies as Enantiomers: Chirality, an Underlying Feature in Chemistry and AstrophysicsSep 16 2005Spiral galaxies are axi-symmetric objects showing 2D-chirality when projected onto a plane. Features in common with tetrahedral molecules are pointed out, in particular the existence of a preferred chiral modality for genetic galaxies as in aminoacids ... More
Spiral Galaxies as Chiral Objects?Sep 16 2005Spiral galaxies show axial symmetry and an intrinsic 2D-chirality. Environmental effects can influence the chirality of originally isolated stellar systems and a progressive loss of chirality can be recognised in the Hubble sequence. We point out a preferential ... More
Chiral Tetrahedrons as Unitary Quaternions: Molecules and Particles Under the Same Standard?Feb 17 2005Chiral tetrahedral molecules can be dealt under the standard of quaternionic algebra. Specifically, non-commutativity of quaternions is a feature directly related to the chirality of molecules. It is shown that a quaternionic representation naturally ... More
Current density and conductivity through modified gravity in the graphene with defectsJul 06 2016Feb 04 2017We propose a model describing the evolution of the free electron current density in graphene. Based on the concept of Mp-branes, we perform the analysis using the difference between curvatures of parallel and antiparallel spins. In such a framework an ... More
Information entropy and dark energy evolutionApr 01 2017The information entropy is here investigated in the context of early and late cosmology under the hypothesis that distinct phases of universe evolution are entangled between them. The approach is based on the \emph{entangled state ansatz}, representing ... More
Defocusing gravitational microlensingOct 21 1996We introduce the notion of defocusing gravitational lens considering a MACHO located behind a light source with respect to an observer. The consequence of defocusing effect is a temporal variability of star luminosity which produces a gap instead of a ... More
Higher order corrections to lensing parameters for extended gravitational lensesSep 28 2001We discuss the contribution to the characteristic lensing quantities, i.e. the deflection angle and Einstein radius, due to the higher order terms (e.g. the gravitomagnetic terms) considered in the lens potential. The cases we analyze are the singular ... More
The Chern-Simons Current in Time Series of Knots and Links in ProteinsApr 25 2018A superspace model of knots and links for DNA time series data is proposed to take into account the feedback loop from docking to undocking state of protein-protein interactions. In particular, the direction of interactions between the 8 hidden states ... More
Gravitational waves in modified teleparallel theories of gravityDec 16 2017Jun 01 2018Teleparallel theory of gravity and its modifications have been studied extensively in literature. However, gravitational waves has not been studied enough in the framework of teleparallelism. In the present study, we discuss gravitational waves in general ... More
Exact cosmological solutions from Hojman conservation quantitiesAug 19 2013We present a new approach to find exact solutions for cosmological models. By requiring the existence of a symmetry transformation vector for the equations of motion of the given cosmological model (without using either Lagrangian or Hamiltonian), one ... More
Observational constraints on Gauss-Bonnet cosmologyMar 02 2018We analyze a fully geometric approach to dark energy in the framework of $F(R,{\cal G})$ theories of gravity, where $R$ is the Ricci curvature scalar and ${\cal G}$ is the Gauss-Bonnet topological invariant. The latter invariant naturally exhausts, together ... More
A time--dependent Cosmological ConstantMay 14 1996Jun 17 1996We extend the Wald cosmic no-hair theorem to a general class of scalar-tensor nonminimally coupled theories of gravity where ordinary matter is also present in the form of a perfect fluid. We give a set of conditions for obtaining a de Sitter expansion ... More
Extended Theories of GravityAug 31 2011Sep 02 2011Extended Theories of Gravity can be considered a new paradigm to cure shortcomings of General Relativity at infrared and ultraviolet scales. They are an approach that, by preserving the undoubtedly positive results of Einstein's Theory, is aimed to address ... More
Quadrupolar gravitational radiation as a test-bed for f(R)-gravityApr 11 2011The debate concerning the viability of f(R)-gravity as a natural extension of General Relativity could be realistically addressed by using results coming from binary pulsars like PSR 1913+16. To this end, we develop a quadrupolar approach to the gravitational ... More
Unveiling the dark energy equation of state from cosmographyMay 11 2019Constraining the dark energy equation of state (EoS), $w_x(z)$, is one of the main issues of current and future cosmological surveys. In practice, this requires making assumptions about the evolution of $w_x$ with redshift $z$, which can be manifested ... More
Possible Gamma-Ray Burst radio detections by the Square Kilometre Array. New perspectivesJul 19 2016The next generation interferometric radio telescope, the Square Kilometre Array (SKA), which will be the most sensitive and largest radio telescope ever constructed, could greatly contribute to the detection, survey and characterization of Gamma Ray Bursts ... More
Stochastic Background of Relic Scalar Gravitational Waves tuned by Extended GravityJun 19 2009A stochastic background of relic gravitational waves is achieved by the so called adiabatically-amplified zero-point fluctuations process derived from early inflation. It provides a distinctive spectrum of relic gravitational waves. In the framework of ... More
Noether symmetries in extended gravity quantum cosmologyAug 06 2013We summarize the use of Noether symmetries in Minisuperspace Quantum Cosmology. In particular, we consider minisuperspace models, showing that the existence of conserved quantities gives selection rules that allow to recover classical behaviors in cosmic ... More
Conformal frames and the validity of Birkhoff's theoremFeb 12 2012Birkhoff's theorem is one of the most important statements of Einstein's general relativity, which generally can not be extended to modified theories of gravity. Here we study the validity of the theorem in scalar-tensor theories using a perturbative ... More
Asymptotic freedom from induced gravity cosmologyMay 23 1996We give conditions to obtain cosmological asymptotic freedom in scalar-tensor theories of gravity. We show that this feature can be achieved in FRW flat spacetimes since we obtain singularity free solutions where the effective gravitational constant $G_{eff}\rightarrow ... More
Bounces, turnarounds and singularities in bimetric gravityNov 01 2012Jan 18 2013In this letter, we consider cosmological solutions of bimetric theory without assuming that only one metric is coupled to gravity. We conclude that any cosmology can be described by fixing the matter content of the space that we are not inhabiting. On ... More
Gravitational waves from stellar encountersJun 25 2008Jul 25 2008The emission of gravitational waves from a system of massive objects interacting on elliptical, hyperbolic and parabolic orbits is studied in the quadrupole approximation. Analytical expressions are then derived for the gravitational wave luminosity, ... More
Extended Gravity: State of the Art and PerspectivesJul 17 2013We shortly review the state of art and perspectives of Extended Theories of Gravity.
Possible Gamma-Ray Burst radio detections by the Square Kilometre Array. New perspectivesJul 19 2016Sep 02 2017The next generation interferometric radio telescope, the Square Kilometre Array (SKA), which will be the most sensitive and largest radio telescope ever constructed, could greatly contribute to the detection, survey and characterization of Gamma Ray Bursts ... More
f(R) cosmology by Noether's symmetryApr 14 2008Feb 10 2010A general approach to find out exact cosmological solutions in f(R)-gravity is discussed. Instead of taking into account phenomenological models, we assume, as a physical criterium, the existence of Noether symmetries in the cosmological f(R) Lagrangian. ... More
Scalar-tensor representation of $f(R)$ gravity and Birkhoff's theoremJul 05 2011Dec 01 2011Birkhoff's theorem is discussed in the frame of f(R) gravity by using its scalar-tensor representation. Modified gravity has become very popular at recent times as it is able to reproduce the unification of inflation and late-time acceleration with no ... More
Noether Symmetries as a geometric criterion to select theories of gravityAug 10 2018Sep 02 2018We review the {\it Noether Symmetry Approach} as a geometric criterion to select theories of gravity. Specifically, we deal with Noether Symmetries to solve the field equations of given gravity theories. The method allows to find out exact solutions, ... More
Testing Quantum Gravity through Dumb HolesNov 27 2016We propose a method to test the effects of quantum fluctuations on black holes by analyzing the effects of thermal fluctuations on dumb holes, the analogues for black holes. The proposal is based on the Jacobson formalism, where the Einstein field equations ... More
Born-Infeld condensate as a possible origin of neutrino masses and dark energyJul 19 2016Jul 21 2016We discuss the possibility that a Born-Infeld condensate coupled to neutrinos can generate both neutrino masses and an effective cosmological constant. In particular, an effective field theory is provided capable of dynamically realizing the neutrino ... More
Cosmological inflation in $F(R,\mathcal{G})$ gravityMar 12 2015Apr 03 2015Cosmological inflation is discussed in the framework of $F(R,{\cal G})$ gravity where $F$ is a generic function of the curvature scalar $R$ and the Gauss-Bonnet topological invariant $\cal G$. The main feature that emerges in this analysis is the fact ... More
Higher-Order Gauss-Bonnet CosmologyApr 19 2013Oct 09 2013We study cosmological models derived from higher-order Gauss-Bonnet gravity $F(R,G)$ by using the Lagrange multiplier approach without assuming the presence of additional fields with the exception of standard perfect fluid matter. The presence of Lagrange ... More
Gravitational waves about curved backgrounds: a consistency analysis in de Sitter spacetimeMay 05 2008Dec 21 2008Gravitational waves are considered as metric perturbations about a curved background metric, rather than the flat Minkowski metric since several situations of physical interest can be discussed by this generalization. In this case, when the de Donder ... More
Equivalence between Palatini and metric formalisms of f(R)-gravity by divergence free currentJun 02 2010The equivalence between metric and Palatini formalisms in f(R)-gravity can be achieved in the general context of theories with divergence free current. This equivalence is a necessary result of a symmetry which is included in a particular conservation ... More
Constraining Generalized Non-local Cosmology from Noether SymmetriesAug 21 2017Oct 03 2017We study a generalized nonlocal theory of gravity which, in specific limits, can become either the curvature non-local or teleparallel non-local theory. Using the Noether Symmetry Approach, we find that the coupling functions coming from the non-local ... More
Thermodynamics and phase transitions of galactic clustering in higher-order Modified GravitySep 11 2018We study the thermodynamics of galactic clustering under the higher-order corrected Newtonian dynamics. The clustering of galaxies is considered as a gravitational phase transition. In order to study the effects of higher-order correction to the thermodynamics ... More
Cosmographic analysis with Chebyshev polynomialsDec 12 2017The limits of standard cosmography are here revised addressing the problem of error propagation during statistical analyses. To do so, we propose the use of Chebyshev polynomials to parameterize cosmic distances. In particular, we demonstrate that building ... More
Model-independent reconstruction of $f(T)$ teleparallel cosmologyJun 09 2017We propose a model-independent formalism to numerically solve the modified Friedmann equations in the framework of $f(T)$ teleparallel cosmology. Our strategy is to expand the Hubble parameter around the redshift $z=0$ up to a given order and to adopt ... More
Cosmological Black Holes as Seeds of Voids in Galaxy DistributionMar 18 2004Deep surveys indicate a bubbly structure of cosmological large scale which should be the result of evolution of primordial density perturbations. Several models have been proposed to explain origin and dynamics of such features but, till now, no exhaustive ... More
Chaos Removal in the $R+qR^2$ gravity: the Mixmaster modelNov 03 2014Nov 13 2014We study the asymptotic dynamics of the Mixmaster Universe, near the cosmological singularity, considering $f(R)$ gravity up to a quadratic corrections in the Ricci scalar $R$. The analysis is performed in the scalar-tensor framework and adopting Misner-Chitr\'e-like ... More
Tuning the stochastic background of gravitational waves with theory and observationsSep 13 2007In this this paper the stochastic background of gravitational waves (SBGWs) is analyzed with the auxilium of the WMAP data. We emphasize that, in general, in previous works in the literature about the SBGWs, old COBE data were used. After this, we want ... More
Noether Symmetry Approach for teleparallel-curvature cosmologyDec 03 2014May 04 2015We consider curvature-teleparallel $F(R,T)$ gravity, where the gravitational Lagrangian density is given by an arbitrary function of the Ricci scalar $R$ and the torsion scalar $T$. Using the Noether Symmetry Approach, we show that the functional form ... More
The quark chemical potential of QCD phase transition and the stochastic background of gravitational wavesAug 19 2018Jan 06 2019The detection of stochastic background of gravitational waves (GWs), produced by cosmological phase transitions (PTs), is of fundamental importance because allows to probe the physics related to PT energy scales. Motivated by the decisive role of non-zero ... More
Anomaly on Superspace of Time Series DataDec 28 2017We apply the G-Theory and anomaly of ghost and anti-ghost fields in the theory of supersymmetry to study a superspace over time series data for the detection of hidden general supply and demand equilibrium in the financial market. We provide a proof of ... More
Model independent constraints on dark energy evolution from low-redshift observationsJun 11 2018Jan 15 2019Knowing the late time evolution of the Universe and finding out the causes for this evolution are the important challenges of modern cosmology. In this work, we adopt a model-independent cosmographic approach and approximate the Hubble parameter considering ... More
Cosmographic applications of Gamma Ray BurstsNov 04 2010Nov 15 2010In this work we present some applications about the use of the so-called Cosmography with GRBs. In particular, we try to calibrate the Amati relation by using the luminosity distance obtained from the cosmographic analysis. Thus, we analyze the possibility ... More
Extended Gravity CosmographyApr 01 2019Cosmography can be considered as a sort of a model-independent approach to tackle the dark energy/modified gravity problem. In this review, the success and the shortcomings of the $\Lambda$CDM model, based on General Relativity and standard model of particles, ... More
Scaling Dark EnergyAug 05 2004Aug 06 2004We investigate the possibility of a dark energy component that is scaling with epochs. A phenomenological model is introduced whose energy density depends on the redshift in such a way that a smooth transition among the three dominant phases of the universe ... More
Noether Symmetry Approach for Dirac-Born-Infeld CosmologyNov 27 2014Feb 09 2015We consider the Noether Symmetry Approach for a cosmological model derived from a tachyon scalar field $T$ with a Dirac-Born-Infeld Lagrangian and a potential $V(T)$. Furthermore, we assume a coupled canonical scalar field $\phi$ with an arbitrary interaction ... More
Big-bounce cosmology from quantum gravity: The case of a cyclical Bianchi I universeJul 15 2016Sep 01 2016We analyse the classical and quantum dynamics of a Bianchi I model in the presence of a small negative cosmological constant characterizing its evolution in term of the dust-time dualism. We demonstrate that in a canonical metric approach, the cosmological ... More
Weak field limit and gravitational waves in higher-order gravityDec 30 2018Jan 12 2019We derive the weak field limit for a gravitational Lagrangian density $L_{g}=(R+a_{0}R^{2}+\sum_{k=1}^{p} a_{k}R\Box^{k}R)\sqrt{-g}$ where higher-order derivative terms in the Ricci scalar $R$ are taken into account. The interest for this kind of effective ... More
Magnetic black holes in Weitzenböck geometryMar 26 2019We derive magnetic black hole solutions using a general gauge potential in the framework of teleparallel equivalent general relativity. One of the solutions gives a non-trivial value of the scalar torsion. This non-triviality of the torsion scalar depends ... More
Cosmological perturbations in gravitational energy-momentum complexDec 28 2018Starting from the energy-momentum of matter and gravitational field in the framework of General Relativity and Teleparallel Gravity, we obtain the energy-momentum complex in flat FRW spacetime. We show that the complex vanishes at background level considering ... More
Cosmic acceleration from a single fluid descriptionDec 12 2017We here propose a new class of barotropic factor for matter, motivated by properties of isotropic deformations of crystalline solids. Our approach is dubbed Anton-Schmidt's equation of state and provides a non-vanishing, albeit small, pressure term for ... More
Rational approximations of $f(R)$ cosmography through Padé polynomialsSep 25 2017Apr 23 2018We consider high-redshift $f(R)$ cosmography adopting the technique of polynomial reconstruction. In lieu of considering Taylor treatments, which turn out to be non-predictive as soon as $z>1$, we take into account the Pad\'e rational approximations which ... More
Connecting early and late universe by $f(R)$ gravityOct 27 2014Inflation and dark energy are two of the most relevant aspects of modern cosmology. These different epochs provide the universe is passing through accelerated phases soon after the Big-Bang and at present stage of its evolution. In this review paper, ... More
Charged spherically symmetric black holes in $f(R)$ gravity and their stability analysisFeb 18 2019Apr 18 2019A new class of analytic charged spherically symmetric black hole solutions, which behave asymptotically as flat or (A)dS spacetimes, is derived for specific classes of $f(R)$ gravity, i.e., $f(R)=R-2\alpha\sqrt{R}$ and $f(R)=R-2\alpha\sqrt{R-8\Lambda}$, ... More
Weak Forces and Neutrino Oscillations under the standards of Hybrid Gravity with TorsionSep 16 2013Nov 06 2013We present a unifying approach where weak forces and neutrino oscillations are interpreted under the same standards of torsional hybrid gravity. This gravitational theory mixes metric and metric-affine formalism in presence of torsion and allows to derive ... More
Swampland conjecture in $f(R)$ gravity by the Noether Symmetry ApproachMay 14 2019Swampland conjecture has been recently proposed to connect early time cosmological models with the string landscape, and then to understand if related scalar fields and potentials can come from some fundamental theory in the high energy regime. In this ... More
Merging matter and geometry in the same LagrangianJun 10 2015Oct 19 2015We show that a Lagrangian density proportional to $\sqrt{-g} \L_m^2/R$ reduces to a pressuron theory of gravity that is indistinguishable from General Relativity in the dust limit. The combination of matter and geometry in the same Lagrangian density ... More
Transition redshift in $f(T)$ cosmology and observational constraintsMar 10 2015Jun 18 2015We extract constraints on the transition redshift $z_{tr}$, determining the onset of cosmic acceleration, predicted by an effective cosmographic construction, in the framework of $f(T)$ gravity. In particular, employing cosmography we obtain bounds on ... More
Kinematic model-independent reconstruction of Palatini $f(R)$ cosmologyJun 17 2018Nov 09 2018A kinematic treatment to trace out the form of $f(R)$ cosmology, within the Palatini formalism, is discussed by only postulating the universe homogeneity and isotropy. To figure this out we build model-independent approximations of the luminosity distance ... More
Charged spherically symmetric black holes in $f(R)$ gravityFeb 18 2019A new class of analytic charged spherically symmetric black hole solutions, which behave asymptotically as flat or (A)dS spacetimes, is derived for specific classes of $f(R)$ gravity, i.e., $f(R)=R-2\alpha\sqrt{R}$ and $f(R)=R-2\alpha\sqrt{R-8\Lambda}$, ... More
Correspondence between Jordan-Einstein frames and Palatini-metric formalismsSep 14 2010We discuss the conformal symmetry between Jordan and Einstein frames considering their relations with the metric and Palatini formalisms for modified gravity. Appropriate conformal transformations are taken into account leading to the evident connection ... More
Dark energy induced by neutrino mixingDec 05 2006Dec 11 2006The energy content of the vacuum condensate induced by the neutrino mixing is interpreted as dynamically evolving dark energy.
The gravitational energy-momentum pseudotensor: the cases of $f(R)$ and $f(T)$ gravityApr 23 2018Jun 03 2018We derive the gravitational energy-momentum pseudotensor $ \tau^{\sigma}_ {\phantom {\sigma} \lambda} $ in metric $ f\left (R \right) $ gravity and in teleparallel $ f\left (T\right) $ gravity. In the first case, $R$ is the Ricci curvature scalar for ... More
Comprehensive cosmographic analysis by Markov Chain MethodApr 15 2011Jan 26 2012We study the possibility to extract model independent information about the dynamics of the universe by using Cosmography. We intend to explore it systematically, to learn about its limitations and its real possibilities. Here we are sticking to the series ... More
The Weierstrass Criterion and the Lemaitre-Tolman-Bondi Models with Cosmological Constant λNov 03 2011We analyze Lemaitre-Tolman-Bondi models in presence of the cosmological constant \Lambda through the classical Weierstrass criterion. Precisely, we show that the Weierstrass approach allows us to classify the dynamics of these inhomogeneous spherically ... More
Gravitational Effective Action at Second Order in Curvature and Gravitational WavesAug 28 2017We consider the full effective theory for quantum gravity at second order in curvature including non-local terms. We show that the theory contains two new degrees of freedom beyond the massless graviton: namely a massive spin-2 ghost and a massive scalar ... More
Noether symmetries and boundary terms in extended Teleparallel gravity cosmologyJul 08 2018Jan 30 2019We discuss an extended Teleparallel gravity models comprising functions of scalar invariants constructed by torsion, torsion Gauss-Bonnet and boundary terms. We adopt the Noether Symmetry Approach to select the functional forms, the first integrals and, ... More
Can f(R) gravity contribute to (dark) radiation?Jul 07 2015Aug 27 2015We discuss the possibility that suitable modifications of gravity could account for some amount of the radiation we observe today, in addition to the possibility of explaining the present speed up of the universe. We start introducing and reviewing cosmological ... More
Qualitative behavior of cosmological models combining various matter fieldsMar 25 2018Jul 03 2018The late time accelerated expansion of the universe can be realized using scalar fields with given self-interacting potentials. Here we consider a straightforward approach where a three cosmic fluid mixture is assumed. The fluids are standard matter perfect ... More
Emergence and expansion of cosmic space as due to M0-branesDec 15 2015Recently, Padmanabhan [arXiv:1206.4916 [hep-th]] discussed that the difference between the number of degrees of freedom on the boundary surface and the number of degrees of freedom in a bulk region causes the accelerated expansion of the universe. The ... More