Showing papers on "Big Rip published in 2022"

Did the Universe experience a pressure non-crushing type cosmological singularity in the recent past?

Abstract: In the recent literature it has been shown that the H 0 tension may be eliminated if an abrupt physics transition changed the Cepheid parameters in the near past of the Universe, nearly 70–150 Myrs ago. In this letter we stress the possibility that this abrupt transition was caused by the smooth passage of our Universe through a pressure finite-time cosmological singularity. Being a non-crushing type singularity the pressure singularity can leave its imprints in the Universe, since it occurs globally and literally everywhere. We discuss how this scenario could easily be realized by F(R) gravity, with the strong energy conditions being satisfied without the need for a scalar field or specific matter fluids. We also stress the fact that the pressure singularity can affect the effective gravitational constant of F(R) gravity. Moreover, we stress the fact that pressure singularities can disrupt the trajectories of bound objects in the Universe, which is also pointed out in the literature, even in the context of general relativity. We also show numerically in a general relativistic framework that elliptic trajectories are distorted and changed to different elliptic trajectories when the Universe passes through the pressure singularity. Such a disruption of the trajectories could have tidal effects on the surface of the Earth, for example on sea waters and oceans, regarding the distortion of Moon's elliptic trajectory. Accordingly, the distortion of Earth's trajectory around the Sun could have affected climatologically the Earth 70–150 Myrs ago.

A Peek Outside Our Universe

Abstract: According to general relativity (GR), a universe with a cosmological constant Λ, like ours, is trapped inside an event horizon, r<3/Λ. What is outside? We show, using Israel (1967) junction conditions, that there could be a different universe outside. Our universe looks like a black hole for an outside observer. Outgoing radial null geodesics cannot escape our universe, but incoming photons can enter and leave an imprint on our CMB sky. We present a picture of such a fossil record from the analysis of CMB maps that agrees with the black hole universe predictions but challenges our understanding of the origin of the primordial universe.

Bianchi-I anisotropic universe with Barrow holographic dark energy

Abstract: Abstract In this paper, we study Bianchi type-I universe in the presence of Barrow holographic dark energy and matter. Anisotropic cosmological model is explored here using the recently proposed holographic principle by Barrow where the standard Bekenstein–Hawking entropy is a special case. The holographic dark energy is employed to investigate the evolution of matter density and the dark energy density in an anisotropic Bianchi-I universe. The equation of state parameter of the dark energy is found to lie in the quintessence or in the phantom regime at the present epoch depending on the value of the new exponent and anisotropy in the universe. We found that an anisotropic universe with higher anisotropy transits to a late accelerating phase before a universe with lower anisotropy. It is also observed that the new exponent plays an important role to identify the nature of the universe.

Stasis in an expanding universe: A recipe for stable mixed-component cosmological eras

Abstract: One signature of an expanding universe is the time-variation of the cosmological abundances of its different components. For example, a radiation-dominated universe inevitably gives way to a matter-dominated universe, and critical moments such as matter-radiation equality are fleeting. In this paper, we point out that this lore is not always correct, and that it is possible to obtain a form of "stasis" in which the relative cosmological abundances $\Omega_i$ of the different components remain unchanged over extended cosmological epochs, even as the universe expands. Moreover, we demonstrate that such situations are not fine-tuned, but are actually global attractors within certain cosmological frameworks, with the universe naturally evolving towards such long-lasting periods of stasis for a wide variety of initial conditions. The existence of this kind of stasis therefore gives rise to a host of new theoretical possibilities across the entire cosmological timeline, ranging from potential implications for primordial density perturbations, dark-matter production, and structure formation all the way to early reheating, early matter-dominated eras, and even the age of the universe.

Bianchi-I anisotropic universe with Barrow holographic dark energy

Abstract: Abstract In this paper, we study Bianchi type-I universe in the presence of Barrow holographic dark energy and matter. Anisotropic cosmological model is explored here using the recently proposed holographic principle by Barrow where the standard Bekenstein–Hawking entropy is a special case. The holographic dark energy is employed to investigate the evolution of matter density and the dark energy density in an anisotropic Bianchi-I universe. The equation of state parameter of the dark energy is found to lie in the quintessence or in the phantom regime at the present epoch depending on the value of the new exponent and anisotropy in the universe. We found that an anisotropic universe with higher anisotropy transits to a late accelerating phase before a universe with lower anisotropy. It is also observed that the new exponent plays an important role to identify the nature of the universe.

Quintom Fields from Chiral K-Essence Cosmology

Abstract: In this paper, we present an analysis of a chiral cosmological scenario from the perspective of K-essence formalism. In this setup, several scalar fields interact within the kinetic and potential sectors. However, we only consider a flat Friedmann–Robertson–Lamaître–Walker universe coupled minimally to two quintom fields: one quintessence and one phantom. We examine a classical cosmological framework, where analytical solutions are obtained. Indeed, we present an explanation of the “big-bang” singularity by means of a “big-bounce”. Moreover, having a barotropic fluid description and for a particular set of parameters, the phantom line is in fact crossed. Additionally, for the quantum counterpart, the Wheeler–DeWitt equation is analytically solved for various instances, where the factor-ordering problem has been taken into account (measured by the factor Q). Hence, this approach allows us to compute the probability density of the previous two classical subcases. It turns out that its behavior is in effect damped as the scale factor and the scalar fields evolve. It also tends towards the phantom sector when the factor ordering constant Q≪0.

Emergence of space and expansion of Universe

Abstract: According to the principle of emergence, the expansion of the universe can be explained as the emergence of space with the progress of cosmic time. We have analytically solved the equation of emergence proposed by Padmanabhan by assuming the Komar energy density $\rho+3P$ as a function of the Hubble parameter. The resulting model describes the evolution of the universe, which proceeds towards a final de Sitter state. Model parameters have been extracted using the cosmological observational data. Further, the horizon entropy evolution of the model has been studied. The model predicts a universe having a transition from a prior decelerated epoch to a late accelerated epoch and reasonably predicts the cosmological constant.

A Heuristic Approach to the Far-Future State of a Universe Dominated by Phantom Energy

Abstract: This work is based on a cosmological scenario of a universe dominated by phantom energy with equation of state parameter w < − 1 and the analysis of its asymptotic behaviour in the far-future. The author discusses whether a Big Rip singularity could be reached in the future. Working in the context of general relativity, it is argued that the Big Rip singularity could be avoided due to the gravitational Schwinger pair-production, even if no other particle-creating contribution takes place. In this model, the universe is described in its far-future by a state of a constant but large Hubble rate and energy density, as well as of a constant but low horizon entropy. Similar conditions existed at the beginning of the universe. Therefore, according to this analysis, not only the Big Rip singularity could be avoided in the far-future but also the universe could asymptotically be led to a new inflationary phase, after which more and more universes could be created.

Reconstruction of modified Gauss–Bonnet gravity for emergent universe

Abstract: We present a flat emergent universe model in modified Gauss–Bonnet gravity in four dimensions. The emergent universe model is free from a big-bang singularity and also describes the observed universe fairly well. It is assumed that the present universe emerged from a static Einstein universe phase that exists in the infinite past. To obtain the flat emergent universe model, we reconstruct mimetic modified [Formula: see text]-gravity ([Formula: see text] representing Gauss–Bonnet terms). The functional form of [Formula: see text]-gravity is determined with or without matter, and can accommodate the early inflation and late accelerating phases satisfactorily. In contrast, in Einstein’s general theory of relativity, a flat emergent universe was obtained within the modified matter sector.

CMB Power Spectrum in the Emergent Universe with K-Essence

Abstract: The emergent universe provides a possible method to avoid the Big Bang singularity by considering that the universe stems from a stable Einstein static universe rather than the singularity. Since the Einstein static universe exists before inflation, it may leave some relics in the CMB power spectrum. In this paper, we analyze the stability condition for the Einstein static universe in general relativity with k-essence against both the scalar and tensor perturbations. Furthermore, we find the emergent universe can be successfully realized by constructing a scalar potential and an equation of state parameter. Solving the curved Mukhanov–Sasaki equation, we obtain the analytical approximation for the primordial power spectrum, and then depict the TT-spectrum of the emergent universe. The results show that both the primordial power spectrum and CMB TT-spectrum are suppressed on large scales.

New futures for cosmological models

Abstract: The discovery of accelerated expansion of the Universe opened up the possibility of new scenarios for the doom of our space-time, besides eternal expansion and a final contraction. In this paper, we review the chances that may await our universe. In particular, there are new possible singular fates (sudden singularities, big rip, etc.), but there also other evolutions that cannot be considered as singular. In addition to this, some of the singular fates are not strong enough in the sense that the space-time can be extended beyond the singularity. For deriving our results, we make use of generalized power and asymptotic expansions of the scale factor of the Universe. This article is part of the theme issue 'The future of mathematical cosmology, Volume 1'.

Clarifying some common misconceptions about the expansion of the universe

Abstract: Abstract Modern cosmology is based on a 6-parameter model, called Lambda-CDM, which provides an accurate description of the expansion of the Universe on the basis of measured parameters. However, there are attempts to give ‘phenomenological’ descriptions of the dynamics of the Universe that are inconsistent with this model and sometimes lead to misconceptions. They stem from a Newtonian approach that interprets the expansion as due to an ‘initial kick’ that placed all matter and energy in the Universe on ‘inertial trajectories’. These descriptions do not conform to the relativistic approach. Here we show that the Einstein field equations trace the expansion of cosmic space directly to the increase in the energy content of the observable universe caused by the additional space entering it as a consequence of the forward motion of its horizon. We derive here the connection between variations in the scale factor and the corresponding variations in the energy of the observable universe, in the case of the most general cosmological model. We then obtain explicit closed-form expressions of this relationship both in the case of the Universe of any curvature and containing matter and radiation, and in the case of the de Sitter universe, characterized by the cosmological constant only. Some interesting features are pointed out, both in terms of the energy growth rate of the observable universe in the various cosmological models, and in terms of the dynamics of the scale factor. Finally our demonstration is corroborated by an analogy between the expansion of cosmic space and the gravitational stretching of space at the center of a sphere of uniform density whose radius increases with time. This analogy, which allowed us to obtain the novel closed-form expression of the stretching of space at the centre of such a sphere, confirmed that the paradigm that ‘gravity expands space’ is valid in both systems.

Big rip in shift-symmetric Kinetic Gravity Braiding theories

Abstract: We revise the future fate of a group of scalar-tensor theories known as kinetic gravity braiding models. As it is well-known, these theories can safely drive the expansion of the universe towards a future de Sitter state if the corresponding Lagrangian is invariant under constant shifts in the scalar field. However, this is not the only possible future state of these shift-symmetric models as we show in this letter. In fact, future cosmic singularities characterized by a divergence of the energy density can also appear in this framework. We present an explicit example where a big rip singularity is the only possible future fate of the cosmos.

On the Fundamental Particles and Reactions of Nature

Abstract: There are unsolved problems related to inflation, gravity, dark matter, dark energy, missing antimatter, and the birth of the universe. Some of them can be better answered by assuming the existence of aether and hypoatoms. Both were created during the inflation in the very early universe. While aether forms vacuum, hypoatoms, composed of both matter and antimatter and believed to be neutrinos, form all observable matter. In vacuum, aether exists between the particle-antiparticle dark matter form and the dark energy form in a dynamic equilibrium: A + A-bar = gamma + gamma. The same reaction stabilizes hypoatoms and generates a 3-dimensional sink flow of aether that causes gravity. Based on the hypoatom structure, the singularity does not exist inside a black hole; the core of the black hole is a hypoatom star or neutrino star. By gaining enough mass, ca. 3 X 1022 Msun, to exceed neutrino degeneracy pressure, the black hole collapses or annihilates into the singularity, thus turning itself into a white hole or a Big Bang. The universe is anisotropic. Its center, or where the Big Bang happened, is at 0.66+0.03-0.01 times the radius of the observable universe at Galactic coordinates (l, b) = (286+10-10, -43+7-6). If we look from the Local Group to the center of the universe, the universe is rotating clockwise.

The Energy of Space

Abstract: Abstract We discuss the effect of the Big Bang as origin of the universe on the concept of energy conservation. In particular, it leads to a non-static universe, an effect which Einstein had tried to avoid by the introduction of the cosmological constant. The advent of Hubble’s law confirmed an expansion of the universe, and the subsequent observation of continued acceleration led to the introduction of the idea of dark energy. In this context, the idea of a universe emerging from nothing was introduced.

On the Fundamental Particles and Reactions of Nature

Abstract: There are unsolved problems related to inflation, gravity, dark matter, dark energy, missing antimatter, and the birth of the universe. Some of them can be better answered by assuming the existence of aether and hypoatoms. Both were created during the inflation in the very early universe. While aether forms vacuum, hypoatoms, composed of both matter and antimatter and believed to be neutrinos, form all observable matter. In vacuum, aether exists between the particle-antiparticle dark matter form and the dark energy form in a dynamic equilibrium: A + A-bar = gamma + gamma. The same reaction stabilizes hypoatoms and generates a 3-dimensional sink flow of aether that causes gravity. Based on the hypoatom structure, the singularity does not exist inside a black hole; the core of the black hole is a hypoatom star or neutrino star. By gaining enough mass, ca. 3 X 1022 Msun, to exceed neutrino degeneracy pressure, the black hole collapses or annihilates into the singularity, thus turning itself into a white hole or a Big Bang. The universe is anisotropic. Its center, or where the Big Bang happened, is at 0.66+0.03-0.01 times the radius of the observable universe at Galactic coordinates (l, b) = (286+10-10, -43+7-6). If we look from the Local Group to the center of the universe, the universe is rotating clockwise.

Type V singularities with inhomogeneous equations of state

Abstract: Interest in cosmological singularities has remarkably grown in recent times, particularly on future singularities with the discovery of late-time acceleration of the universe and dark energy. Recent work has seen a proper classification of such singularities into strong and weak based on their strength, with weak singularities being the likes of sudden, w and big freeze singularities and strong singularities like the big rip. This has led to a classification of such singularities in various types like Big rip is Type 1, w-singularity is type V etc. While singularities of type I-type IV have been discussed vividly by taking into account inhomogeneous equations of state (EOS), the same has not been attempted for type V singularities. So in this work we have discussed in detail about the formation of type V singularities in various cosmologies after considering inhomogeneous equations of state. We consider two inhomogeneous forms of the EOS in the context of four different cosmological backgrounds ; standard general relativistic cosmology, an asymptotically safe cosmology, a cosmology inspired by modified area-entropy relations, generalized uncertainty principles, holographic renormalization and Chern-Simons gravity( all of which can be coincidentally described by the same form of the modified Friedmann equation) and an f(R) gravity cosmology. We show in detail that one sees some very big differences in the occurence conditions of type V singularities when one makes such considerations. In the particular case of the f(R) gravity cosmology, we see that the type V singularities get completely removed. This work goes to show that the creation and formation of type V singularities is influenced most strongly by the form of the equation of state that one considers, way more so than what background cosmology one chooses.

Calculation of the Moment of the Beginning of the Existence of Light in the Universe

Abstract: The apparent age of the universe is about T » 13.56´109 years. Light is part of our everyday life, but it has not always existed. According to physicists, it began to exist about ~360 000 to 380 000 years after the Big Bang. We calculated the exact moment of the appearance of light based on a new cosmological model shown in 2019. In this model, we make the following hypotheses: 1) The apparent radius of curvature of the universe increases at the velocity of light. 2) Our universe is in rotation on itself. 3) The tangential speed of the universe’s periphery is the same as an electron. 4) Our universe is made of a ″material universe″ imbricated in a ″luminous universe″. With Einstein’s laws of relativity for spinning disks and the addition of speeds, we can establish the moment where the universe became transparent and emitted light. We evaluate that moment to ~361 108 years after the Big Bang. The assumptions used for the calculations reveal some interesting facts about the structure and characteristics of our universe. This article may be a step-stone for other analyses.

Riemann and Big Bang Hypotheses

Abstract: In this study, we suggest an alternative to the well-known Big Bang theory. The hypothesis that the universe began as a collision between two or more dense fireballs is discussed. Universe expansion and shrinkage are considered consequences of species creation and death. Moreover, the concept of real versus the virtual existence of the universe is evoked. Furthermore, we posit the existence of a Mega universe that bounds two or more parallel universes. Possible scenarios for the end of the universe are also investigated. The study considers a mathematical model of Bing Bang associated with the famous Riemann hypothesis.

The Once and Future Universe

Abstract: Abstract The Once and Future Universe begins with the discovery that the universe is expanding. Not only are galaxy clusters and superclusters moving away from one another, but they are being carried apart by the expansion of spacetime caused by the Big Bang 13.8 billion years ago. The Big Bang theory, combined with cosmic inflation, describe the beginning of the universe, an idea confirmed by the discovery of the predicted 3 K microwave background. However, our models are handicapped by the lack of a complete theory of quantum gravity. Recent observations have demonstrated that not only is the universe expanding, but contrary to intuition it is accelerating, leading to the conclusion that spacetime includes some form of dark energy that science has yet to understand. Fittingly, the chapter and the textbook end with a look at how our universe might end.

&lt;strong&gt; &lt;/strong&gt;A Quantum Space Model of Cosmic Evolution: Dark Energy and the Fate of the Universe

Abstract: We present a Quantum Space Model (QSM) of cosmic evolution based on the theory that space consists of energy quanta which participates in the evolution of the universe. It shows that Dark Energy is the energy of space which causes its accelerating expansion. We used the Friedmann equations to trace the history of the cosmos from a time before the Big Bang to its ultimate end. The universe started from a quantum size volume of space with high energy density.Quantum fluctuations triggered the release of energy in a Big Bang at very high temperature and pressure. It then expanded and cooled undergoing phase transitions to radiation, fundamental particles, and matter. Matter grew into galaxies, and was further consolidated by gravity into Dark Energy Stars/Black Holes, ending in a Big Crunch at about 1.380 trillion years, thus bringing the universe back to its initial state. It can stay in a Deep Feeeze inside a Black Hole and through fluctuations or other mechanism may start a new cycle in its life with a new Bang. If the Law of Conservation of Energy is universal, then the cosmos is eternal. Space and energy are equivalent just as matter and energy are. This is well founded in Planck&rsquo;s energy equation. They are the two most fundamental quantities in the universe that govern cosmic evolution. The two principal long range forces are the gravitational force and the space force.The latter could be the fifth force in the universe. They may provide the clockwork mechanism that operates our eternal cyclic universe.