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Mauricio Bellini

Publications and source records attributed to Mauricio Bellini.

At least 73 records · Page 4Linked to original sources
arXiv2012

Gravitational waves during inflation from a 5D large-scale repulsive gravity model

We investigate, in the transverse traceless (TT) gauge, the generation of the relic background of gravitational waves, generated during an early inflationary stage, on the framework of a large-scale repulsive gravity model. We calculate the spectrum of the tensor metric fluctuations of an effective 4D Schwarzschild-de-Sitter metric, which is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution, in the context of a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is nearly scale invariant under certain conditions. One interesting aspect of this model is that is possible to derive dynamical field equations for the tensor metric fluctuations, valid not just at cosmological scales, but also at astrophysical scales, from the same theoretical model. The astrophysical and cosmological scales are determined by the gravity- antigravity radius, which is a natural length scale of the model, that indicates when gravity becomes repulsive in nature.

gr-qc↗
arXiv2012

Gravitational confinement of photons and matter from Induced Matter theory

Using an Extended Scharzschild-Anti de Sitter (ESAdS) metric here introduced, where the noncompact extra dimension is time-like, we study the gravitational confinement of matter and photons from a 5D vacuum. The important result here obtained is that the photon trajectories (in general, massless particles) are periodic. They are confined to a radius $r\leq 2 m G/c^2$ by the gravitational field. Massive test particles are also gravitationally confined, but their trajectories are not periodic.

gr-qc↗
arXiv2012

Dirac equation in a de Sitter expansion for massive neutrinos from modern Kaluza-Klein theory

Using the modern Kaluza-Klein theory of gravity (or the Induced Matter theory), we study the Dirac equation for massive neutrinos on a de Sitter background metric from a 5D Riemann-flat (and hence Ricci-flat) extended de Sitter metric, on which is defined the vacuum for test massless 1/2-neutral fields minimally coupled to gravity and free of any other interactions. We obtain that the effective 4D masses of the neutrinos can only take three possible values, which are related to the (static) foliation of the fifth and noncompact extra dimension.

hep-th↗
arXiv2012

Quantum origin of pre-big bang collapse from Induced Matter theory of gravity

We revisit a collapsing pre-big-bang model of the universe to study with detail the non-perturbative quantum dynamics of the dispersal scalar field whose dynamics becomes from the dynamical foliation of test massless scalar field $ϕ$ on a 5D Riemann-flat metric, such that the extra space-like coordinate is noncompact. The important result here obtained is that the evolution of the system, which is described thorough the equation of state has the unique origin in the quantum contributions of the effective 4D scalar field.

gr-qc↗
arXiv2011

Dirac equation for massive neutrinos in a Schwarzschild-de Sitter spacetime from a 5D vacuum

Starting from a Dirac equation for massless neutrino in a 5D Ricci-flat background metric, we obtain the effective 4D equation for massive neutrino in a Schwarzschild-de Sitter (SdS) background metric from an extended SdS 5D Ricci-flat metric. We use the fact that the spin connection is defined to an accuracy of a vector, so that the covariant derivative of the spinor field is strongly dependent of the background geometry. We show that the mass of the neutrino can be induced from the extra space-like dimension.

hep-th↗
arXiv2011

Pre-big bang collapsing universe from modern Kaluza-Klein theory of gravity

We study the collapse of the universe described by a scalar field spherically symmetric collapse of a system described by a massless scalar field from a 5D Riemann-flat canonical metric, on which we make a dynamical foliation on the extra space-like dimension. The asymptotic universe (absent of singularities) results to be finite in size and energy density, with an vacuum dominated equation of state. The important result here obtained is that the asymptotic back-reaction effects are given by a negative constant: $1/2 [\frac{1}{1+\dotψ^2}+\frac{1}{\dotψ^2}] <(\dot{δ\barϕ})^2>+{1\over 2a^2} <(\vec{\nabla}δϕ)^2>|_{t\rightarrow\infty} = {-8 Λ_0 \over 3 πG}$.

gr-qc↗
arXiv2011

Particles and gravitons creation after inflation from a 5D vacuum

We use the Bogoliubov formalism to study both, particles and gravitons creation at the reheating epoch, after a phase transition from inflation to a radiation dominated universe. The modes of the inflaton field fluctuations and the scalar fluctuations of the metric at the end of inflation are obtained by using a recently introduced formalism related to the Induced Matter theory of gravity. The interesting result is that the number of created particles is bigger than $10^{90}$ on cosmological scales. Furthermore, the number of gravitons are nearly $10^{-17}$ times smaller than the number of created particles. In both cases, these numbers rapidly increases on cosmological scales.

gr-qc↗
arXiv2011

Super exponential inflation from a dynamical foliation of a 5D vacuum state

We introduce super exponential inflation ($ω< -1$) from a 5D Riemann-flat canonical metric on which we make a dynamical foliation. The resulting metric describes a super accelerated expansion for the early universe well-known as super exponential inflation that, for very large times, tends to an asymptotic de Sitter (vacuum dominated) expansion. The scalar field fluctuations are analyzed. The important result here obtained is that the spectral index for energy density fluctuations is not scale invariant, and for cosmological scales becomes $n_s(k k_*) <0 $.

gr-qc↗
arXiv2011

Stochastic emergence of inflaton fluctuations in a SdS primordial universe with large-scale repulsive gravity from a 5D vacuum

We develop a stochastic approach to study scalar field fluctuations of the inflaton field in an early inflationary universe with a black-hole (BH), which is described by an effective 4D SdS metric. Considering a 5D Ricci-flat SdS static metric, we implement a planar coordinate transformation, in order to obtain a 5D cosmological metric, from which the effective 4D SdS metric can be induced on a 4D hypersurface. We found that at the end of inflation, the squared fluctuations of the inflaton field are not exactly scale independent and becomes sensitive with the mass of the BH.

gr-qc↗
arXiv2011

Analytical treatment of SUSY Quasi-normal modes in a non-rotating Schwarzschild black hole

We use the Fock-Ivanenko formalism to obtain the Dirac equation which describes the interaction of a massless 1/2-spin neutral fermion with a gravitational field around a Schwarzschild black hole (BH). We obtain approximated analytical solutions for the eigenvalues of the energy (quasi-normal frequencies) and their corresponding eigenstates (quasi-normal states). The interesting result is that all the excited states [and their supersymmetric (SUSY) partners] have a purely imaginary frequency, which can be expressed in terms of the Hawking temperature. Furthermore, as one expects for SUSY Hamiltonians, the isolated bottom state has a real null energy eigenvalue.

gr-qc↗
arXiv2010

Fierz-Pauli equation for massive gravitons from Induced Matter theory of gravity

Starting with a 5D physical vacuum described by a 5D Ricci-flat background metric, we study the emergence of gravitational waves (GW) from the Induce Matter (IM) theory of gravity. We obtain the equation of motion for GW on an 4D curved spacetime which has the form of a Fierz-Pauli one. In our model the mass of gravitons $m_g$ is induced by a static foliation on the noncompact space-like extra dimension and the source-term is originated in the interaction of the GW with the induced connections of the background 5D metric. Here, relies the main difference of this formalism with the original Fierz-Pauli one.

gr-qc↗
arXiv2010

Primordial SdS universe from a 5D vacuum: scalar field fluctuations on Schwarzschild and Hubble horizons

We study scalar field fluctuations of the inflaton field in an early inflationary universe on an effective 4D Schwarzschild-de Sitter (SdS) metric, which is obtained after make a planar coordinate transformation on a 5D Ricci-flat Schwarzschild-de Sitter (SdS) static metric. We obtain the important result that the spectrum of fluctuations at zeroth order is independent of the scalar field mass $M$ on Schwarzschild scales, while on cosmological scales it exhibits a mass dependence. However, in the first-order expansion, the spectrum depends of the inflaton mass and the amplitude is linear with the Black-Hole (BH) mass $m$.

gr-qc↗
arXiv2010

Coupled inflaton and electromagnetic fields from Gravitoelectromagnetic Inflation with Lorentz and Feynman gauges

Using a semiclassical approach to Gravitoelectromagnetic Inflation (GEMI), we study the origin and evolution of seminal inflaton and electromagnetic fields in the early inflationary universe from a 5D vacuum state. We use simultaneously the Lorentz and Feynman gauges. Our formalism is naturally not conformal invariant on the effective 4D de Sitter metric, which make possible the super adiabatic amplification of electric and magnetic field modes during the early inflationary epoch of the universe on cosmological scales. This is the first time that solutions for the electric field fluctuations are investigated in a systematic way as embeddings for inflationary models in 4D. An important and new result here obtained is that the spectrum of the electric field fluctuations depend with the scale, such that the spectral index increases quadratically as the scale decreases.

astro-ph.CO↗
arXiv2010

Semiclassical Gravitoelectromagnetic inflation in a Lorentz gauge: seminal inflaton fluctuations and electromagnetic fields from a 5D vacuum state

Using a semiclassical approach to Gravitoelectromagnetic Inflation (GEMI), we study the origin and evolution of seminal inflaton and electromagnetic fields in the early inflationary universe from a 5D vacuum state. The difference with other previous works is that in this one we use a Lorentz gauge. Our formalism is naturally not conformal invariant on the effective 4D de Sitter metric, which make possible the super adiabatic amplification of magnetic field modes during the early inflationary epoch of the universe on cosmological scales.

astro-ph.CO↗
arXiv2009

Entropy evolution in warm inflation from a 5D vacuum

Using some ideas of Modern Kaluza-Klein theory, we examine the evolution of entropy on a 4D Friedmann-Robertson-Walker (FRW) brane from a 5D vacuum state, which is defined on a 5D background Riemann-flat metric. We found that entropy production is sufficiently important during inflation: $S > 10^{90}$, for all the initial values of temperature $T_0 < T_{GU}$.

gr-qc↗