arXiv subjects

Cláudio Nassif Cruz

Publications and source records attributed to Cláudio Nassif Cruz.

8 recordsLinked to original sources

arXiv2024

Lorentz violation with an invariant minimum speed as foundation of the uncertainty principle in Minkowski, dS and AdS spaces

This research aims to provide the geometrical foundation of the uncertainty principle within a new causal structure of spacetime so-called Symmetrical Special Relativity (SSR), where there emerges a Lorentz violation due to the presence of an invariant minimum speed $V$ related to the vacuum energy. SSR predicts that a dS-scenario occurs only for a certain regime of speeds $v$, where $v 0$. For $v=v_0$, Minkowski (pseudo-Euclidian) space is recovered for representing the flat space ($Λ=0$), and for $v>v_0$ ($Φ>0$), Anti-de Sitter (AdS) scenario prevails ($Λ<0$). The fact that the current universe is flat as its average density of matter distribution ($ρ_m$ given for a slightly negative curvature $R$) coincides with its vacuum energy density ($ρ_Λ$ given for a slightly positive curvature $Λ$), i.e., the {\it cosmic coincidence problem}, is now addressed by SSR. SSR provides its energy-momentum tensor of perfect fluid, leading to the EOS of vacuum ($p=-ρ_Λ$). Einstein equation for vacuum given by such SSR approach allows us to obtain $ρ_Λ$ associated with a scalar curvature $Λ$, whereas the solution of Einstein equation only in the presence of a homogeneous distribution of matter $ρ_m$ for the whole universe presents a scalar curvature $R$, in such a way that the presence of the background field $Λ$ opposes the Riemannian curvature $R$, thus leading to a current effective curvature $R_{eff}=R+Λ\approx 0$ according to observations.

gr-qc↗

arXiv2024

Background gravitational waves as signature of the adiabatic expansion of a black body that represents the dark universe

We propose a toy model of a spherical universe made up of an exotic dark gas with temperature $T$ in thermal equilibrium with a black-body in adiabatic expansion. Each particle of this exotic gas mimics a kind of particle of dark energy represented by the vacuum energy, being quantized into virtual particles with extremely small masses that form such gas representng the own tissue of the expanding space-time governed by a negative pressure whose origin is the equation of state (EOS) of vacuum, i.e., $p=-ρ$, where $ρ$ is the vacuum energy density. So, each vacuum particle occupies a tiny area of space so-called Planck area $L_p^{2}$, which represents the minimum area of the whole space-time given by the spherical surface with area $4πR_H^2$, where $R_H$ is the Hubble radius. We realize that such spherical surface is the surface of the black-body for representing the dark universe as if it were the surface of an expanding balloon. Thus, we are able to derive the law of universal gravitation, thus leading us to understand the cosmological anti-gravity. We estimate the very small order of magnitude of the cosmological constant and the acceleration of expansion of the dark sphere. In this toy model, as the dark universe can be thought of as a large black body, when we obtain its power and frequency of emission of radiation, we find very low values. We conclude that such radiation and frequency of the black body made up of dark energy is a background gravitational wave with very low frequency in the order of $10^{-17}$Hz due to the slight stretching of the fabric of space-time.

gr-qc↗

arXiv2023

A brief review of a modified relativity that explains cosmological constant

The present review aims to show that a modified space-time with an invariant minimum speed provides a relation with Weyl geometry in the Newtonian approximation of weak-field. The deformed Special Relativity so-called Symmetrical Special Relativity (SSR) has an invariant minimum speed $V$, which is associated with a preferred reference frame $S_V$ for representing the vacuum energy, thus leading to the cosmological constant ($Λ$). The equation of state (EOS) of vacuum energy for $Λ$, i.e., $ρ_Λ=ε=-p$ emerges naturally from such space-time, where $p$ is the pressure and $ρ_Λ=ε$ is the vacuum energy density. With the aim of establishing a relationship between $V$ and $Λ$ in the modified metric of the space-time, we should consider a dark spherical universe with Hubble radius $R_H$, having a very low value of $ε$ that governs the accelerated expansion of universe. In doing this, we aim to show that SSR-metric has an equivalence with a de-Sitter (dS)-metric ($Λ>0$). On the other hand, according to the Boomerang experiment that reveals a slightly accelerated expansion of the universe, SSR leads to a dS-metric with an approximation for $Λ<<1$ close to a flat space-time, which is in the $ΛCDM$ scenario where the space is quasi-flat, so that $Ω_{m}+Ω_Λ\approx 1$. We have $Ω{cdm}\approx 23\%$ by representing dark cold matter, $Ω_m\approx 27\%$ for matter and $Ω_Λ\approx 73\%$ for the vacuum energy. Thus, the theory is adjusted for the redshift $z=1$. This corresponds to the time $τ_0$ of transition between gravity and anti-gravity, leading to a slight acceleration of expansion related to a tiny value of $Λ$, i.e., we find $Λ_0=1.934\times 10^{-35}s^{-2}$. This result is in agreement with observations.

gr-qc↗

arXiv2023

Deformed Special Relativity with a minimum speed as explanation of the tiny value of the cosmological constant based on the Boomerang experiment in the $ΛCDM$ scenario

In this paper we will show that a new structure of space-time with a minimum speed reveals a connection with Weyl geometry in the approximation of weak-field Newtonian limit. Symmetrical Special Relativity (SSR) has a minimum speed $V$ that plays the role of a preferred reference frame $S_V$ of vacuum that leads to the cosmological constant $Λ$. In order to realize such a connection between $V$ and $Λ$ within a scenario of space-time metric, we will use a model of spherical universe with Hubble radius $R_H$ filled by a low vacuum energy density $ρ_Λ$ that governs the accelerated expansion of the universe. In doing this, we will show that SSR-metric plays the role of a de-Sitter (dS)-metric with a positive cosmological constant ($Λ>0$). On the other hand, according to the Boomerang experiment as it is shown that the three-dimensional space of the universe is Euclidean and with a slightly accelerated expansion, SSR leads to a dS-metric with an approximation for $Λ<<1$ close to a flat space-time, which is in the $ΛCDM$ scenario where the space is quasi-flat, so that $Ω_{m}+Ω_Λ\approx 1$. We have $Ω{cdm}\approx 23\%$ by representing dark cold matter, $Ω_m\approx 27\%$ for matter and $Ω_Λ\approx 73\%$ for the vacuum energy. Thus, the theory is adjusted for redshift $z=1$, i.e., the time $τ_0$ at which the universe goes over from a decelerating to an accelerating expansion by obtaining the numerical value $Λ_0=1.934\times 10^{-35}s^{-2}$, being in good agreement with measurements.

physics.gen-ph↗

arXiv2022

Deformed Special Relativity with an invariant minimum speed as an explanation of the cosmological constant

This paper shows the need of the emergence of a universal minimum speed in the space-time by means of a more thorough investigation of Dirac's large number hypothesis (LNH). We will realize that there should be a minimum speed $V$ with the same status of the invariance of the speed of light $c$, however $V$ has gravitational origin. Hence, such a minimum speed forms a new kinematic basis in the space-time, thus leading to a new Deformed Special Relativity (DSR) for the quantum world so-called Symmetrical Special Relativity (SSR). Furthermore, we will show that such a new structure of space-time (SSR) reveals a connection between $V$ and a preferred reference frame $S_V$ of background field that leads to the cosmological constant $Λ$, which can be associated with a cosmological anti-gravity. We will also investigate the effect of the number of baryons $N$ (Eddington number) of the observable universe on the Hydrogen atom. Finally, we will show that SSR-metric plays the role of a de-Sitter (dS)-metric with a positive cosmological constant, which could assume a tiny value.

gr-qc↗

arXiv2021

Variation of the speed of light with temperature of the expanding universe

From an extended relativistic dynamics for a particle moving in a cosmic background field with temperature T, we aim to obtain the speed of light with an explicit dependence on the background temperature of the universe. Although finding the speed of light in the early universe much larger than its current value, our approach does not violate the postulate of special relativity. Moreover, it is shown that the high value of the speed of light in the early universe was drastically decreased before the beginning of the inflationary period. So we are led to conclude that the theory of varying speed of light should be questioned as a possible solution of the horizon problem.

gr-qc↗

arXiv2020

Lorentz violation with an invariant minimum speed as foundation of the tachyonic inflation within a Machian scenario

We show the relationship between the scalar kinematics potential of Symmetrical Special Relativity (SSR) and the ultra-referential of vacuum connected to an invariant minimum speed postulated by SSR. The property of the conformal metric of SSR is showed, from where we deduce a kind of de Sitter metric. The negative curvature of spacetime is calculated from the conformal property of the metric. Einstein equation provides an energy-momentum tensor which is proportional to SSR-metric. We also realize that SSR leads to a deformed kinematics with quantum aspects directly related to the delocalization of the particle and thus being connected to the uncertainty principle. We finish this work by identifying the lagrangian of SSR with the so-called tachyonic models (slow-roll), where the tachyonic potential is a function depending on the conformal factor, thus allowing the SSR-lagrangian to be able to mimic a tachyonic lagrangian related to the so-called Dirac-Born-Infeld lagrangian, where the superluminal effects are interpreted as being a large stretching of spacetime due to new relativistic effects close to the invariant minimum speed as being the foundation of the inflationary vacuum connected to a variable cosmological parameter that recovers the cosmological constant for the current universe.

physics.gen-ph↗

arXiv2020

Cosmology of the Symmetrical Relativity versus Spontaneous Creation of the Universe Ex Nihilo

The cosmology of "Spontaneous Creation of the Universe Ex Nihilo" and the cosmology of the Symmetrical Relativity offer proposals to explain the creation and evolution of the universe. In essence they are still very distinct. However, we will argue that there was an antecedent to the big bang. Thus, we will penetrate a trans-Planckian regime, where we find an effective Planck length $L_P^{\prime}\rightarrow 0$. This will lead to more fundamental physical reflections about {\it nothing} in the cosmology of spontaneous creation. From the point of view of spontaneous creation, the step backwards went back to another principle, based on the {\it information}, which led to the big bang. While the spontaneous creation refers to the virtual pre-existence of {\it information}, which would have emerged randomly from {\it nothing}, the cosmology of Symmetrical Relativity does not stop there: we go back to one's own origin by projecting it before the creation of one's own time. From the present perspective, {\it nothing} is a primordial vacuum, whose {\it information} has made the universe by condensing and igniting. It was not randomly created, since the entropy had to vary from infinite (chaos) to zero (big bang) by violating the 2nd.law of thermodynamics in a trans-Planckian regime. {\it Nothing} or chaos with infinite entropy precedes the big bang (null entropy) within a trans-Planckian scenario and it determines the whole plot until the total extinction of the universe. We will show that {\it information}, besides not being born of the universe, also does not develop from it like the computational idea of Artificial Intelligence (AI). Thus, the universe is not simply self-taught as defended by the spontaneous creation. This could shed light on the problem of Penrose's Weyl curvature hypothesis, which considers a null Weyl curvature due to a null entropy in the big bang.

physics.gen-ph↗