arXiv subjects

Giuseppe Gaetano Luciano

Publications and source records attributed to Giuseppe Gaetano Luciano.

At least 55 records · Page 3Linked to original sources

arXiv2023

Saez-Ballester gravity in Kantowski-Sachs Universe: a new reconstruction paradigm for Barrow Holographic Dark Energy

We reconstruct Barrow Holographic Dark Energy (BHDE) within the framework of Saez-Ballester Scalar Tensor Theory. As a specific background, we consider a homogeneous and anisotropic Kantowski-Sachs Universe filled up with BHDE and dark matter. By assuming the Hubble radius as an IR cutoff, we investigate both the cases of non-interacting and interacting dark energy scenarios. We analyze the evolutionary behavior of various model parameters, such as skewness parameter, Equation-of-State parameter, deceleration parameter, jerk parameter and squared sound speed. We also draw the trajectories of $ω_D-ω'_D$ phase plane and examine statefinder diagnosis. Observational consistency is discussed by inferring the current value of Hubble's parameter through the best fit curve of data points from Differential Age (DA) and Baryon Acoustic Oscillations (BAO) and commenting on cosmological perturbations and growth rate of matter fluctuations in BHDE. We show that our model satisfactorily retraces the history of the Universe, thus providing a potential candidate explanation for dark energy. Comparison with other reconstructions of BHDE is finally analyzed.

gr-qc↗

arXiv2023

Constraining Barrow entropy-based Cosmology with power-law inflation

We study the inflationary era of the Universe in a modified cosmological scenario based on the gravity-thermodynamics conjecture with Barrow entropy instead of the usual Bekenstein-Hawking one. The former arises from the effort to account for quantum gravitational effects on the horizon surface of black holes and, in a broader sense, of the Universe. First, we extract modified Friedmann equations from the first law of thermodynamics applied to the apparent horizon of a Friedmann- Robertson-Walker Universe in (n + 1)-dimensions. Assuming a power-law behavior for the scalar inflaton field, we then investigate how the inflationary dynamics is affected in Barrow cosmological setup. We find that the inflationary era may phenomenologically consist of the slow-roll phase, while Barrow entropy is incompatible with kinetic inflation. By demanding observationally consistency of the scalar spectral index and tensor-to-scalar ratio with recent Planck data, we finally constrain Barrow exponent to $Δ\lesssim10^{-4}$.

gr-qc↗

arXiv2022

On the flavor/mass dichotomy for mixed neutrinos: a phenomenologically motivated analysis based on lepton charge conservation in neutron decay

Flavor/mass dichotomy} for mixed fields is one of the most controversial issues in Quantum Field Theory. In this work we approach the problem by considering mixing of neutrinos and computing the transition amplitude for the paradigmatic neutron $β$-decay $n\,\rightarrow\, p \,+\,e^ \,+\,\barν$. Calculations are developed by utilizing the following different representations of neutrino states: \emph{i}) Pontecorvo states, \emph{ii}) mass states and \emph{iii}) exact QFT flavor states, which are defined as eigenstates of the flavor charge. As a guiding principle, we invoke the conservation of lepton charge in the interaction vertex, which is fundamentally inbuilt into the Standard Model at tree level. In the short-time limit, we show that the only fully consistent scenario is that based on QFT states, whereas the other two frameworks contradict the underlying theory. This result provides a crucial step towards understanding the rôle of neutrino mixing in weak decays and contributes to elucidate the flavor/mass controversy in QFT.

hep-ph↗

arXiv2022

Generalized interacting Barrow Holographic Dark Energy: cosmological predictions and thermodynamic considerations

We construct a generalized interacting model of Barrow Holographic Dark Energy (BHDE) with infrared cutoff being given by the Hubble horizon. We analyze the cosmological evolution of a flat Friedmann-Lemaître-Robertson-Walker Universe filled by pressureless dark matter, BHDE and radiation fluid. The interaction between the dark sectors of the cosmos is assumed of non-gravitational origin and satisfying the second law of thermodynamics and Le Chatelier-Braun principle. We study the behavior of various model parameters, such as the BHDE density parameter, the equation of state parameter, the deceleration parameter, the jerk parameter and the square of sound speed. We show that our model satisfactorily retraces the thermal history of the Universe and is consistent with current observations for certain values of parameters, providing an eligible candidate to describe dark energy. We finally explore the thermodynamics of our framework, with special focus on the validity of the generalized second law.

gr-qc↗

arXiv2022

Cosmic evolution and thermal stability of Barrow holographic dark energy in nonflat Friedmann-Robertson-Walker Universe

We study the cosmological evolution of a nonflat Friedmann-Robertson-Walker Universe filled by pressureless dark matter and Barrow Holographic Dark Energy (BHDE). The latter is a dark energy model based on the holographic principle with Barrow entropy instead of the standard Bekenstein-Hawking one. By assuming the apparent horizon of the Universe as IR cutoff, we explore both the cases where a mutual interaction between the dark components of the cosmos is absent/present. We analyze the behavior of various model parameters, such as the BHDE density parameter, the equation of state parameter, the deceleration parameter, the jerk parameter and the square of sound speed. We also comment on the observational consistency of our predictions, showing that the interacting model turns out to be favored by recent experimental constraints from Planck+WP+BAO, SNIa+CMB+LSS and Union2 SNIa joint analysis over the non-interacting one. The thermal stability of our framework is finally discussed by demanding the positivity of the heat capacities and compressibilities of the cosmic fluid.

gr-qc↗

arXiv2022

Dark Matter as an effect of a minimal length

In this work, we consider the implications of a phenomenological model of quantum gravitational effects related to a minimal length, implemented via the Generalized Uncertainty Principle. Such effects are applied to the Bekenstein-Hawking entropy to derive a modified law of gravity through Verlinde's conjecture. Implications on galactic scales, and in particular on the shape of rotational curves, are investigated, exploring the possibility to mimic dark matter-like effects via a minimal length.

gr-qc↗

arXiv2022

Baryogenesis in non-extensive Tsallis Cosmology

Non-extensive Tsallis thermostatistics is a widespread paradigm to describe large-scale gravitational systems. In this work we use Tsallis Cosmology to study thermodynamic gravity and derive modified Friedmann equations. We show that corrections induced by non-extensivity affect the Hubble function evolution during the radiation-dominated epoch. In turn, this leads to non-trivial modifications of the mass density and pressure content of the Universe, which provide a viable mechanism allowing for baryogenesis, even in the presence of the standard interaction between the Ricci scalar and baryon current. By demanding consistency with current observational bounds on baryogenesis, we constrain Tsallis $δ$ parameter to be $|δ-1| \simeq 10^{-3}$. Based on the recently established connection between Tsallis thermostatistics and the quantum gravitational generalization of the uncertainty principle at Planck scale (GUP), we finally show that this bound is in agreement with the estimation of the GUP parameter predicted by many quantum gravity models.

gr-qc↗

arXiv2022

Baryon asymmetry from Barrow entropy: theoretical predictions and observational constraints

We investigate the generation of baryon asymmetry from the corrections brought about in the Friedman equations due to Barrow entropy. In particular, by applying the gravity-thermodynamics conjecture one obtains extra terms in the Friedmann equations that change the Hubble function evolution during the radiation-dominated epoch. Hence, even in the case of standard coupling between the Ricci scalar and baryon current they can lead to a non-zero baryon asymmetry. In order to match observations we find that the Barrow exponent should lie in the interval $0.005 \lesssim Δ\lesssim 0.008$, which corresponds to a slight deviation from the standard Bekenstein-Hawking entropy. The upper bound is tighter than the one of other observational constraints, however the interesting feature is that in the present analysis we obtain a non-zero lower bound. Nevertheless this lower bound would disappear if the baryon asymmetry in Barrow-modified cosmology is generated by other mechanisms, not related to the Barrow modification.

gr-qc↗

arXiv2022

Decoherence limit of quantum systems obeying generalized uncertainty principle: new paradigm for Tsallis thermostatistics

The generalized uncertainty principle (GUP) is a phenomenological model whose purpose is to account for a minimal length scale (e.g., Planck scale or characteristic inverse-mass scale in effective quantum description) in quantum systems. In this Letter, we study possible observational effects of GUP systems in their decoherence domain. We first derive coherent states associated to GUP and unveil that in the momentum representation they coincide with Tsallis' probability amplitudes, whose non-extensivity parameter $q$ monotonically increases with the GUP deformation parameter $β$. Secondly, for $β< 0$ (i.e., $q < 1$), we show that, due to Bekner-Babenko inequality, the GUP is fully equivalent to information-theoretic uncertainty relations based on Tsallis-entropy-power. Finally, we invoke the Maximal Entropy principle known from estimation theory to reveal connection between the quasi-classical (decoherence) limit of GUP-related quantum theory and non-extensive thermostatistics of Tsallis. This might provide an exciting paradigm in a range of fields from quantum theory to analog gravity. For instance, in some quantum gravity theories, such as conformal gravity, aforementioned quasi-classical regime has relevant observational consequences. We discuss some of the implications.

hep-th↗

arXiv2021

Bekenstein bound and uncertainty relations

The non zero value of Planck constant $h$ underlies the emergence of several inequalities that must be satisfied in the quantum realm, the most prominent one being Heisenberg Uncertainty Principle. Among these inequalities, Bekenstein bound provides a universal limit on the entropy that can be contained in a localized quantum system of given size and total energy. In this Letter, we explore how Bekenstein bound is affected when Heisenberg uncertainty relation is deformed so as to accommodate gravitational effects close to Planck scale (Generalized Uncertainty Principle). By resorting to general thermodynamic arguments, and in regimes where the equipartition theorem still holds, we derive in this way a "generalized Bekenstein bound". Physical implications of this result are discussed for both cases of positive and negative values of the deformation parameter.

hep-th↗

arXiv2021

Primordial Big Bang Nucleosynthesis and Generalized Uncertainty Principle

The Generalized Uncertainty Principle (GUP) naturally emerges in several quantum gravity models, predicting the existence of a minimal length at Planck scale. Here, we consider the quadratic GUP as a semiclassical approach to thermodynamic gravity and constrain the deformation parameter by using observational bounds from Big Bang Nucleosynthesis and primordial abundances of the light elements 4He,D,7Li. We show that our result fits with most of existing bounds on βderived from other cosmological studies.

astro-ph.CO↗

arXiv2021

Gravitational effects on the Heisenberg Uncertainty Principle: a geometric approach

The Heisenberg Uncertainty Principle (HUP) limits the accuracy in the simultaneous measurements of the position and momentum variables of any quantum system. This is known to be true in the context of non-relativistic quantum mechanics. Based on a semiclassical geometric approach, here we propose an effective generalization of this principle, which is well-suited to be extended to general relativity scenarios as well. We apply our formalism to Schwarzschild and de Sitter space-time, showing that the ensuing uncertainty relations can be mapped into well-known deformations of the HUP. We also infer the form of the perturbed metric that mimics the emergence of a discrete spacetime structure at Planck scale, consistently with the predictions of the Generalized Uncertainty Principle. Finally, we discuss our results in connection with other approaches recently appeared in the literature.

gr-qc↗

arXiv2021

Gravitational effects on neutrino decoherence in Lense-Thirring metric

We analyze gravity effects on neutrino wave packet decoherence. As a specific example, we consider the gravitational field of a spinning spherical body described by the Lense-Thirring metric. By working in the weak-field limit and employing Gaussian wave packets, we show that the characteristic coherence length of neutrino oscillation processes is nontrivially affected, the corrections being dependent on the mass and angular velocity of the gravity source. Possible experimental implications are finally discussed.

hep-th↗

arXiv2021

Generalized Uncertainty Principle: from the harmonic oscillator to a QFT toy model

Several models of quantum gravity predict the emergence of a minimal length at Planck scale. This is commonly taken into consideration by modifying the Heisenberg Uncertainty Principle into the Generalized Uncertainty Principle. In this work, we study the implications of a polynomial Generalized Uncertainty Principle on the harmonic oscillator. We revisit both the analytic and algebraic methods, deriving the exact form of the generalized Heisenberg algebra in terms of the new position and momentum operators. We show that the energy spectrum and eigenfunctions are affected in a non-trivial way. Furthermore, a new set of ladder operators is derived which factorize the Hamiltonian exactly. The above formalism is finally exploited to construct a quantum field theoretic toy model based on the Generalized Uncertainty Principle.

hep-th↗

arXiv2021

Nonextensive Tsallis statistics in Unruh effect for Dirac neutrinos

Flavor mixing of quantum fields was found to be responsible for the breakdown of the thermal Unruh effect. Recently, this result was revisited in the context of nonextensive Tsallis thermostatistics, showing that the emergent vacuum condensate can still be featured as a thermal-like bath, provided that the underlying statistics is assumed to obey Tsallis prescription. This was analyzed explicitly for bosons. Here we extend this study to Dirac fermions and in particular to neutrinos. Working in the relativistic approximation, we provide an effective description of the modified Unruh spectrum in terms of the q-generalized Tsallis statistics, the q-entropic index being dependent on the mixing parameters sin θ and Δm. As opposed to bosons, we find q > 1, which is indicative of the subadditivity regime of Tsallis entropy. An intuitive understanding of this result is discussed in relation to the nontrivial entangled structure exhibited by the quantum vacuum for mixed fields, combined with the Pauli exclusion principle.

hep-th↗

arXiv2021

q-generalized Tsallis thermostatistics in Unruh effect for mixed fields

It was shown that the particle distribution detected by a uniformly accelerated observer in the inertial vacuum (Unruh effect) deviates from the pure Planckian spectrum when considering the superposition of fields with different masses. Here we elaborate on the statistical origin of this phenomenon. In a suitable regime, we provide an effective description of the emergent distribution in terms of the nonextensive q-generalized statistics based on Tsallis entropy. This picture allows us to establish a nontrivial relation between the q-entropic index and the characteristic mixing parameters sinθ and Δm. In particular, we infer that q < 1, indicating the superadditive feature of Tsallis entropy in this framework. We discuss our result in connection with the entangled condensate structure acquired by the quantum vacuum for mixed fields.

hep-th↗

arXiv2021

Flavor vacuum entanglement in boson mixing

Mixing transformations in quantum field theory are non-trivial, since they are intimately related to the unitary inequivalence between Fock spaces for fields with definite mass and fields with definite flavor. Considering the superposition of two neutral scalar (spin-0) bosonic fields, we investigate some features of the emerging condensate structure of the flavor vacuum. In particular, we quantify the flavor vacuum entanglement in terms of the von Neumann entanglement entropy of the reduced state. Furthermore, in a suitable limit, we show that the flavor vacuum has a structure akin to the thermal vacuum of Thermo Field Dynamics, with a temperature dependent on both the mixing angle and the particle mass difference.

hep-th↗

arXiv2020

Quantum nonlocality in extended theories of gravity

We investigate how pure-state Einstein-Podolsky-Rosen correlations in the internal degrees of freedom of massive particles are affected by a curved spacetime background described by extended theories of gravity. We consider models for which the corrections to the Einstein-Hilbert action are quadratic in the curvature invariants and we focus on the weak-field limit. We quantify nonlocal quantum correlations by means of the violation of the Clauser-Horne-Shimony-Holt inequality, and show how a curved background suppresses the violation by a leading term due to general relativity and a further contribution due to the corrections to Einstein gravity. Our results can be generalized to massless particles such as photon pairs and can thus be suitably exploited to devise precise experimental tests of extended models of gravity.

gr-qc↗