arXiv subjects

Mauricio Bellini

Publications and source records attributed to Mauricio Bellini.

At least 19 recordsLinked to original sources

arXiv2025

Quantum Gravity and Inflation as an Open System: A New Paradigm

As part of our program to develop a general theory of relativity for open systems, we introduce a covariant theory that incorporates the effects of classical and quantum spacetime alterations in a new metric tensor that effectively includes these alterations, thereby generating a Riemannian manifold from a new varied action without boundary terms. We illustrate the theory by studying an inflationary model which incorporates the quantum feedback effects of spacetime on the dynamics of the inflaton field $\hat{\varphi}$, enabling the simultaneous quantization of $\hat{\varphi}$ and the fluctuating gravitational field $\hat{\Omega}$ without relying on perturbative theory. We obtain an exact solution for the modes of both fields, $\hat{\varphi}$ and $\hat{\Omega}$, which comply with different quantum algebras. The normalization of the inflaton field modes that is obtained is intrinsically related to the geometric field modes, in such a way that the quantization of the fields results from an expression that links the geometric fields with the physical fields. Finally, the quadratic fluctuations of spacetime are calculated, and its spectrum is analyzed.

gr-qc↗

arXiv2025

Spectral dimensionality of spacetime around a radiating Schwarzschild black-hole

In this work we study the spectral dimensionality of spacetime around a radiating Schwarzschild black hole using a recently introduced formalism of quantum gravity, where the alterations of the gravitational field produced by the radiation are represented on an extended manifold, and describe a non-commutative and non-linear algebra. The ration between classical and quantum perturbations of spacetime can be measured by the parameter $z \geq 0$. When $z=(1+\sqrt{3})/2\simeq 1.3660$, a relativistic observer approaching the Schwarzschild horizon perceives a spectral dimension $N(z)=4\left[\theta(z)-1\right]\simeq 2.8849$. Under these conditions, all studied Schwarzschild black holes with masses ranging from the Planck mass to $10^{46}$ times the Planck mass, present the same stability configuration which suggests the existence of an universal property of these objects under those particular conditions. The difference from the spectral dimension previously obtained at cosmological scales leads to the conclusion that the dimensionality of spacetime is scale-dependent. Another important result presented here, is the fundamental alteration of the effective gravitational potential near the horizon due to Hawking radiation. This quantum phenomenon prevents the potential from diverging to negative infinity as the observable approaches the Schwarzschild horizon.

gr-qc↗

arXiv2024

Geometric Hawking radiation of Schwarzschild Black Hole with novel quantum algebra

In the context of an extended General Relativity theory with boundary terms included, we introduce a new nonlinear quantum algebra involving a quantum differential operator, with the aim to calculate quantum geometric alterations when a particle is created in the vicinity of a Schwarzschild black-hole by the Hawking radiation mechanism. The boundary terms in the varied action give rise to modifications in the geometric background, which are investigated by analyzing the metric tensor and the Ricci curvature within the framework of a renormalized quantum theory of gravity.

gr-qc↗

arXiv2023

Seminal Electromagnetic fields from preinflation

We investigate the geometric dynamics of the primordial electric and magnetic fields during the early stages of the universe by extending a recently introduced quantum algebra \cite{BMM,BMAS}. We work on an extended model of gravity that considers the boundary terms from the Einstein-Hilbert action as geometric quantum fluctuations of the spacetime. We propose that the extended Riemann manifold is generated by a new connection ${\hat{\delta\Gamma}}^{\mu}_{\alpha\beta}$. This connection contains geometric information about the fluctuations of gravitational and electromagnetic fields in the vacuum, which could have been crucial during the primordial stages of the universe's evolution. We revisit a preinflationary cosmological model \cite{mb} with a variable time scale and negative spatial curvature, such that the universe begins with a null initial background energy density. We observed the emergence of large scale magnetic fields starting from small values during the early phases of the universe's evolution. Subsequently, these fields decrease to reach present day values on the order of $\left<\hat{\delta B}\right> \simeq 10^{-12}\,{\rm G}$ on cosmological scales (between $10^{24}$ and $10^{26}$ meters). This significant deviation from inflationary models eliminates the need to impose excessively large initial values on these fields.

gr-qc↗

arXiv2022

Cosmological Boundary Flux Parameter

The {\it{Cosmological Boundary Flux Parameter}} is a novel proposal that attempts to explain the origin of the cosmological parameter $Λ$ purely by geometric nature. Then we implement this new approach to a flat FLRW universe along with a barotropic fluid. We present an ansatz in which $Λ$ is straightforwardly coupled to the matter sector; therefore, only one additional parameter was introduced: $λ$. Also, through a statistical analysis, using late-time data of observational Hubble and type Ia Supernovae, we computed the joint best-fit value of the free parameters by means of the affine-invariant MCMC. We want to emphasise that the joint analysis produces a smaller $H_{0}^{\rm CBFP}=69.80\rm\,\, Km \,s^{-1}\,Mpc^{-1}$ in contrast to the flat $Λ$CDM result $H_{0}^{Λ\rm CDM}=70.53\rm\,\, Km \,s^{-1}\,Mpc^{-1}$. The work presented here seeks to contribute to the discussion of the possible explanation for the cosmos' acceleration, together with tackling other important questions in modern cosmology.

gr-qc↗

arXiv2021

Space-time waves from a collapsing universe with a gravitational attractor

We study a collapsing system attracted by a spherically symmetric gravitational source, with an increasing mass, that generates back-reaction effects that are the source of space-time waves. As an example, we consider an exponential collapse and the space-time waves emitted during this collapse due to the back-reaction effects, originated by geometrical deformation driven by the increment of the gravitational attracting mass during the collapse.

gr-qc↗

arXiv2020

Quantum thermodynamics in the interior of a Reissner-Nordström black-hole

We study the interior of a Reissner-Nordström Black-Hole (RNBH) using Relativistic Quantum Geometry, which was introduced in some previous works. We found discrete energy levels for a scalar field from a polynomial condition for the Heun Confluent functions expanded around the effective causal radius $r_*$. From the solutions it is obtained that the uncertainty principle is valid for each energy level of space-time, in the form: $E_n\, r_{*,n}=\hbar/2$, and the charged mass is discretized and distributed in a finite number of states. The classical RNBH entropy is recovered as the limit case where the number of states is very large, and the RNBH quantum temperature depends on the number of states in the interior of the RNBH. This temperature, depending of the number of states of the RNBH, is related with the Bekeinstein-Hawking (BH) temperature: $T_{BH} \leq T_{N} < 2\,T_{BH}$.

gr-qc↗

arXiv2020

Quantum magnetic monopoles at the Planck era from unified spinor fields

I use Unified Spinor Fields (USF), to discuss the creation of magnetic monopoles during preinflation, as excitations of the quantum vacuum coming from a condensate of massive charged vector bosons. For a primordial universe with total energy $M_p$, and for magnetic monopoles created with a total Planck magnetic charge $q_M=q_P=\pm e/\sqrtα$ and a total mass $m_M$, it is obtained after quantisation of the action that the fine-structure constant is given by: $α= \frac{5}{6} \left(1- \frac{16 \,m_M}{5 \,M_p}\right) \,\left(\frac{e}{q_M}\right)^2$. If these magnetic monopoles were with total magnetic charge $q_M=\pm e$ and a small mass $m=m_M/n$, there would be a large number of small quantum magnetic monopoles which could be candidates to explain the presence of dark matter with a $30.97\,\%$ of the energy in the primordial universe at the Planck era. The case of milli-magnetically charged particles is also analysed. We demonstrate that magnetic monopoles (MM) with masses less than $3.6\times 10^3$ GeV, can exist with a very small charges of up to $10^{-14}\,e$, which are quantities of interest for searches to be performed in the ATLAS and MoEDAL experiments.

gr-qc↗

arXiv2020

Large scales space-time waves from inflation with time dependent cosmological parameter

We study the emission of large-scales wavelength space-time waves during the inflationary expansion of the universe, produced by back-reaction effects. As an example, we study an inflationary model with variable time scale, where the scale factor of the universe grows as a power of time. The coarse-grained field to describe space-time waves is defined by using the Levy distribution, on the wavenumber space. The evolution for the norm of these waves on cosmological scales is calculated, and it is shown that decreases with time.

gr-qc↗

arXiv2019

Space-time waves from a collapse with a time dependent cosmological parameter

We study the emission of space-time waves produced by back-reaction effects during a collapse of a spherically symmetric universe with a time dependent cosmological parameter, which is driven by a scalar field. As in a previous work the final state avoids the final singularity due to the fact the co-moving relativistic observer never reaches the center, because the physical time evolution $dτ=U_{0}\,dx^0$, decelerates for a co-moving observer which falls with the collapse. The equation of state of the system depends on the rate of the collapse, but always is positive: $0 < ω(p) < 0.25$.

gr-qc↗

arXiv2019

Quantum thermodynamics in the interior of a Schwarzschild B-H

We study the interior of a Schwarzschild Black-Hole (B-H) using Relativistic Quantum Geometry described in \cite{rb} and \cite{rb1}. We found discrete energy levels for a scalar field from a polynomial condition for Heun Confluent functions expanded around the Schwarzschild radius. From the solutions it is obtained that the uncertainty principle is valid for each energy level of space-time, in the form: $E_n\, r_{sh,n}=\hbar/2$. Temperature, entropy and the B-H mass are dependent on the number of states in the B-H, such that the Bekenstein-Hawking (BH) results are obtained in a limit case.

gr-qc↗

arXiv2019

Fermionic origin of dark energy in the inflationary universe from Unified Spinor Fields

In this work we explore the boundary conditions in the Einstein-Hilbert action, by considering a displacement from the Riemannian manifold to an extended one. The latter is characterized by including spinor fields into the quantum geometric description of a noncommutative spacetime. These fields are defined on the background spacetime, emerging from the expectation value of the quantum structure of spacetime generated by matrices that comply with a Clifford algebra. We demonstrate that spinor fields are candidate to describe all known interactions in physics, with gravitation included. In this framework we demonstrate that the cosmological constant $Λ$, is originated exclusively by massive fermion fields that would be the primordial components of dark energy, during the inflationary expansion of an universe that describes a de Sitter expansion.

physics.gen-ph↗

arXiv2019

Waves of space-time from a collapsing compact object

We study the partial time dependent collapse of a spherically symmetric compact object with initial mass $M_1+M_2$ and final mass $M_2$ and the waves of space-time emitted during the collapse via back-reaction effects. We obtain exact analytical solutions for the waves of space-time in an example in which $M_1=M_2=(M_1+M_2)/2$. The wavelengths of the space-time emitted waves during the collapse have the cut (we use natural units $c=\hbar=1$): $λ< (2/b)$, $(1/b)$-being the time scale that describes the decay of the compact object.

gr-qc↗

arXiv2019

Quantum thermodynamics in a static de Sitter space-time and initial state of the universe

Using Relativistic Quantum Geometry we study back-reaction effects of space-time inside the causal horizon of a static de Sitter metric, in order to make a quantum thermodynamical description of space-time. We found a finite number of discrete energy levels for a scalar field from a polynomial condition of the confluent hypergeometric functions expanded around $r=0$. As in the previous work, we obtain that the uncertainty principle is valid for each energy level on sub-horizon scales of space-time. We found that temperature and entropy are dependent on the number of sub-states on each energy's level and the Bekenstein-Hawking temperature of each energy level is recovered when the number of sub-states of a given level tends to infinity. We propose that the primordial state of the universe could be described by a de Sitter metric with Planck energy $E_p=m_p\,c^2$, and a B-H temperature: $T_{BH}=\left(\frac{\hbar\,c}{2π\,l_p\,K_B}\right)$.

gr-qc↗

arXiv2019

Exponential collapse with variable time scale driven by a scalar field

We study the dynamic collapse driven by a scalar field, when a relativistic observer falls co-moving with the collapse and cross the horizon of a Schwarzschild black-hole (BH), at $t=t_0$. During the collapse the scale of time is considered as variable. Back-reaction effects and gravitational waves produced during the exponential collapse are studied. We demonstrate that back-reaction effects act as the source of gravitational waves emitted during the collapse, and wavelengths of gravitational waves (GW) are in the range: $λ\ll r_s\equiv {e^{-2h_0t_0}\over 2 h_0}$, that is, smaller than the Schwarzschild radius. We demonstrate that during all the collapse the global topology of the space-time remains hyperbolic when the observer cross the horizon.

gr-qc↗

arXiv2019

Towards unified spinor fields: confinement of gravitons on a dS background

We propose an unified theory for spinor fields on extended Weyl manifolds taking into account self-interactions to obtain the Relativistic dynamics on a general curved Riemannian background as continuation of the Relativistic Quantum Geometry program, recently introduced. We focuss our attention separately on both, massless and matter fields. We study an example of confined gravitons on a de Sitter (dS) background at Planckian scales.

hep-th↗

arXiv2019

Particle-antiparticle duality from an extra time-like dimension

It is a well known fact that the usual complex structure on the real Clifford Algebra (CA) of Minkowski spacetime can be obtained by adding an extra time-like dimension, instead of the usual complexification of the algebra. In this article we explore the consequences of this approach and reinterpret known results in this new context. We observe that Dirac particles and antiparticles at rest can be interpreted as eigenstates of the generator of rotations in the plane formed by the two time-like coordinates and find an effective finite scale for the extra dimension when no EM fields are present (without postulating compactness). In the case of non-vanishing EM fields, we find a gauge condition to preserve such a scale.

hep-th↗

arXiv2019

Traversable wormhole magnetic monopoles from Dymnikova Metric

We study a traversable wormhole originated by a transformation over the 4D Dymnikova metric which describes analytic Black-Holes (BH). By using a transformation of coordinates which is adapted from the used in the Einstein-Rosen bridge, we study a specific family of geodesics in which a test particle with non-zero electric charge induces an effective magnetic monopole, that is perceived by observers outside the wormhole. Because the Riemannian geometry cannot explain the presence of magnetic monopoles, then we propose a torsional geometry in order to explore the possibility that magnetic monopoles can be geometrically induced. We obtain an expression that relates torsion and magnetic fields jointly with a Dirac-like expression for magnetic and electric charges, such that torsion makes possible define a fundamental length that provides a magnetic field and a spacetime discretization.

gr-qc↗