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In this manuscript we consider the normal branch of DGP brane cosmological model in the presence of a ‎scalar field on the brane as the dark energy component. Using dynamical system approach we investigate ‎the stability properties of the system. We will see that one of the defined new variables lambda, that ‎depends on the potential function of the scalar field has a significant role in the evolution of the universe. ‎Therefore, we divide our discussion into two parts, the constant and the varying lambda. With a good ‎approximation we consider all the obtained critical points in the case of the constant lambda, as the ‎instantaneous critical points for the case of a varying lambda. We investigate two special scalar field ‎potential function: a double exponential potential and an inverse power law potential. In both of the cases we ‎study the evolution of the system and discuss the fate of the universe. We find that the inverse power law ‎potential function is in a good agreement with the current universe, but the double exponential potential ‎function can predict different future for the universe.‎

We investigate Friedmann–Lamaitre–Robertson–Walker (FLRW) models with modified Chaplygin gas and cosmological constant, using dynamical system methods. We assume $$p=(\gamma -1)\mu -\dfrac{A}{\mu ^\alpha }$$ p = ( γ - 1 ) μ - A μ α as equation of state where $$\mu$$ μ is the matter-energy density, p is the pressure, $$\alpha$$ α is a parameter which can take on values $$0 0 < α ≤ 1 as well as A and $$\gamma$$ γ are positive constants. We draw the state spaces and analyze the nature of the singularity at the beginning, as well as the fate of the universe in the far future. In particular, we address the question whether there is a solution which is stable for all the cases.

The black hole (b.h.) model based on the strong field treatment of the Newton potential is presented. The essential role of self energy both at the Planck level and for matter and radiation at later stages supports the picture of an expanding Universe necessarily accompanied by particle creation if energy conservation applies at every scale. This process is shown to provide a gravitational repulsive force which can counterbalance gravitational attraction thus allowing the possibility of a steady expansion. This black hole treatment of our Universe evolution, questions the necessity of inflation. The role of the critical density to dictate the fate of the Universe is replaced by the black hole condition which entails a different relation between Hubble parameter and density thus disposing of dark energy. Since its predictions provide a different time development of the Universe also the evidence for its acceleration is disputed. That seems to provide a coherent scheme for our picture of the Universe evolution, based on Hubble’s law and backed up by the consideration of inertial forces. Newtonian angular momentum is also not conserved at cosmological scales. Finally we consider two coordinates systems. The conformally flat coordinates are shown to disprove inflation and the relevance of the Painleve-Gullstrand metric in providing global coordinates is underlined. The combined effect of Hubble expansion and of proper time also questions the existence of missing mass.

Astrophysicist Katie Mack studies the birth, life and death of the cosmos. She shares her predictions for the fate of everything with Leah Crane

In this paper, we investigate the effects of torsion and shears within the framework of the gravitational field with torsion in early and late cosmology. General relativity and torsion field equations are constructed using absolute parallel geometry. The Big Rip model of the Universe has been presented using a special class of Riemann–Cartan geometry and the law of variation of Hubble’s parameter. The model does not depend on the curvature constant. The positive condition of the energy density of the matter is satisfied in this model. This cosmological model shows that the torsion and shear effect is strong at the beginning of the Big Bang and at the end of the universe. Through the examination of precise cases of the parameters and initial conditions, we can show that for suitable ranges of the parameters, the dynamic torsion scalar model can exhibit features similar to those of the currently observed accelerating universe. The relationship between the torsion and shear scalars is investigated, and their impact on the accelerating universe is addressed apart from the idea of dark energy.

The multimillennial philosophical discussion about life after death has received a recent boost in the prospect of immortality attained via technologies. In this newer version, humans generally are considered mortal but may develop means of making themselves immortal. If “immortal” means not mortal, thus existing for infinity, and if the proposed infinite-existing entity is material, it must inhabit an infinite material universe. If the proposed entity is not material, there must be means by which it can shed its material substance and exist nonmaterially. The article examines arguments for how an infinite life would be possible given current physical understanding. The paper considers a Pascalian-style wager weighing the likelihood of adjusting to existence wholly within a finite universe versus betting on there being some way to construe the universe(s) as a viable medium for infinite beings. Conclusion: the case for a finite being to exist infinitely has little viable support.

The aim of this article is to formulate the theological notions of the end and fulfilment of the universe before the background of relativity theory and cosmology, in particular the lack of a global passage of time. It argues that the “arrow” of time is a local phenomenon, linked essentially to recording objects. On this basis, it makes the case that the notions of a common end of all local times and of a final, timeless state of the universe are viable independently of a global direction of time.

To investigate the cosmic future of the universe, first, we obtain the particle and event horizons, and their evolution in time for three well-known varying cosmological constant models. We investigate the implications of these varying cosmological constant models on the particle and event horizons, and their time evolution during the universe history and future. We study the behaviours around the origin and at the far future of the universe for all cases. Finally, we obtained the general behaviours of the horizons and time evolution functions with respect to the general scale factor a for each of the three cases of varying cosmological constant. The results show that for two of our three cases, a big bounce scenario is inevitable for the universe starting from the big bang and ending up with a bouncing re-collapse to its initial state.

Distributions of the universe horizon distance and universe horizon volume were investigated in the light of five general cosmic models which were constructed in a previous study. Both distributions increase so slowly up to t \(\approx\) 21.5444 Myr, , then they start rising very fast up to t \(\approx\) 60 Gyr. Afterwards, they increase again very slowly until t \(\approx\) 124 Gyr. Distributions of mass of radiation, matter and dark energy within the horizon volume of the universe were also studied in the five general cosmic models. The masses of both radiation and matter decrease gradually with time to t \(\approx\) 34627.5 – 55916.2 yr, where it becomes equal to the mass of matter. Then the mass of matter dominated until t \(\approx\) 9.4525 – 10.0632 Gyr, where it becomes equal to the mass of dark energy. Thenceforward, the mass of dark energy prevails the universe. The cosmic space becomes approximately matter empty in the so far future of the universe.

We investigate a multi-field model of dark energy in this paper. We develop a model of dark energy with two multiple scalar fields: one we consider is a multi-field tachyon and the other is multi-field phantom tachyon scalars. We make an analysis of the system in phase space by considering inverse square potentials suitable for these models. Through the development of an autonomous dynamical system, the critical points and their stability analysis is performed. It has been observed that these stable critical points are satisfied by power-law solutions. Moving on toward the analysis, we can predict the fate of the universe. A special feature of this model is that it affects the equation of state parameter w to alter from being it greater than $$-\,1$$ to be less than it during the evolutionary phase of the universe. Thus, it’s all about the phantom divide which turns out to be decisive in the evolution of the cosmos in these models.

In this paper, we have considered a quadratic variation of the deceleration parameter ($q$) as a function of cosmic time ($t$) which describes a smooth transition from the decelerating phase of the Universe to an accelerating one and also show some distinctive feature from the standard model. The logical move of this article is against the behavior of the future Universe, \textit{i.e.} whether the Universe expands forever or ends with a Big Rip, and we observe that the outcome of the considered parametrization comes in favor of Big Rip future of the Universe. The whole set up of the parametrization and solution is taken in $f(R,T)$ theory of gravity for a spatially flat Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) geometry. Furthermore, we have considered the functional form of $f(R,T)$ function as $% f(R)+f(T)$, where a quadratic correction of the geometric term $R$ is adopted as the function $f(R)$, and a linear matter term $f(T)$. We have investigated some features of the model by examining the behavior of physical parameters. Our primary goal here is to discuss the physical dynamics of the model in $f(R,T)$ gravity. We have found, the EoS parameter also has the same singularity as that of the Hubble parameter \textit{i.e.} at the initial phase and at the Big Rip. The EoS parameter is explored in some detail for our choice of $f(R,T)$ function considered here. Different cases for $f(R,T)$ functional form for different values of the coupling parameters are discussed, and the evolution of the physical parameters is shown graphically., Comment: 14 pages, 3 figures with sub-figures

We construct a generalization of the standard $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model, wherein we simultaneously replace the spatially flat Robertson-Walker metric with its simplest anisotropic generalization (LRS Bianchi I metric), and couple the cold dark matter to the gravity in accordance with the energy-momentum squared gravity (EMSG) of the form $f({T}_{\ensuremath{\mu}\ensuremath{\nu}}{T}^{\ensuremath{\mu}\ensuremath{\nu}})\ensuremath{\propto}{T}_{\ensuremath{\mu}\ensuremath{\nu}}{T}^{\ensuremath{\mu}\ensuremath{\nu}}$. These two modifications---namely, two new stiff fluid-like terms of different nature---can mutually cancel out, i.e., the shear scalar can be screened completely, and reproduce mathematically exactly the same Friedmann equation of the standard $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model. This evades the BBN limits on the anisotropy, and thereby provides an opportunity to manipulate the cosmic microwave background quadrupole temperature fluctuation at the desired amount. We further discuss the consequences of the model on the very early times and far future of the Universe. This study presents also an example of that the EMSG of the form $f({T}_{\ensuremath{\mu}\ensuremath{\nu}}{T}^{\ensuremath{\mu}\ensuremath{\nu}})\ensuremath{\propto}{T}_{\ensuremath{\mu}\ensuremath{\nu}}{T}^{\ensuremath{\mu}\ensuremath{\nu}}$, as well as similar type other constructions, is not necessarily relevant only to very early Universe but may even be considered in the context of a major problem of the current cosmology related to the present-day Universe, the so-called ${H}_{0}$ problem.

The age of the Universe is given by \(t_0=13.8\times 10^9\;\text {yr}\) and will be derived in the next chapter. It may be taken as a reference point to compare the ratio of the expansion scale factor \(R(t)/R_0\) for different values of t, that is at different stages of the evolution of the Universe.

We review and discuss recent work exploring the implications of the Higgs field for early universe cosmology, and vice versa. Depending on the model under consideration the Higgs may be one of a few scalar fields determining the evolution and fate of the Universe, or the Higgs field may be connected to a rich sector of scalar moduli with complicated dynamics. In particular we look at the potential consequences of the Higgs field for inflation and its predictions, for the (meta)stability of the Standard Model vacuum, and for the existence of dynamical selection mechanisms in the landscape., Comment: 25 pages, no figures

In this work, we propose a scheme for cosmic evolution in a generalized Rastall gravity. In our approach, the role of dark energy is taken by the non-conserved sector of the stress energy-momentum tensor. The resultant cosmic evolution is found to naturally consists of three stages, namely, radiation dominated, ordinary matter dominated, as well as dark energy and dark matter dominated eras. Furthermore, for the present model, it is demonstrated that the eventual fate of the Universe is mostly insensitive to the initial conditions, in contrast to the standard $\Lambda$CDM model. In particular, the solution displays the properties of a dynamic attractor, which is reminiscent of quintessence and k-essence models. Subsequently, the cosmic coincidence problem is averted. The amount of deviation from a conserved stress energy-momentum tensor is shown to be more remarkable during the period when the dark energy evolves more rapidly. On the other hand, the conservation law is largely restored for the infinite past and future. The implications of the present approach are addressed., Comment: Accepted by the European Physical Journal C

No abstract available.

Big Bang theory postulates the red shift of light coming from distant galaxies is caused by the Doppler Effect. Like Plato’s astronomy, Big Bang theory has to be continuously propped up by countless patches in order to deal with new observations. Plato’s astronomy required countless epicycles within epicycles. Big Bang requires patches such as dark energy, dark matter, cosmic inflation, accelerating expansion of the Universe and countless revisions of Hubble’s constant. In addition, this theory and the fundamental law of mass and energy conservation are mutually exclusive; according to Big Bank all energy and mass appeared suddenly out of nothing. There are of course Big Bang versions that try not to contradict the conservation law. Such theories postulate a multi-verse populated by an infinite number of Universes or an infinite number of Universe instances. In other words, either the most basic law of physics or Occam’s razor must be rejected in the most outrageous manner possible because otherwise the Doppler Effect cannot be used to explain the cosmic red shift. For these reasons, some astronomers promoted the stationary Universe theory and assumed that photons lose a significant amount of energy while traversing intergalactic distances and therefore suffer a red shift. This assumption is the basis of all Tired Light theories. According to Tired Light, photon energy loss is caused by collisions with other objects such as gas molecules or dust. As a result, this theory was quickly dismissed, because this loss mechanism cannot explain the broadening of supernova spectra, the variable rate of photon frequency decay and the fact that the image of distant objects is not blurred. Subsequently other versions of Tired Light theories were ignored because supposedly any other loss mechanism is not compatible with GTR field equations. According to these equations, when the photon structure is ignored, the energy momentum-tensor of a photon moving freely through space is constant. Experiments with laser beams show this conclusion is not exactly true. Therefore even free photons actually lose some minute amount of energy. What physical mechanism may explain this loss? A simple experiment with a common object will immediately reveal this mechanism. Internal interactions are the main mechanism responsible for the gradual dampening of spring oscillations and loss of energy, not collisions with other objects. When damping of photon oscillations caused by internal friction is considered, a new version of Tired Light can be formulated; a version that is validated by all astronomic observations without recourse to any patches and without rejecting the law of energy and mass conservation or Occam’s razor.

The present paper embraces mainly the three-year period of 1966 to 1968 when the invariant integral of fracture mechanics appeared and became popular, and the last two years of 2015 to 2016 when the neoclassic cosmology based on the invariant integral came up. A mention is given to the previous works of Euler, Cauchy, Maxwell, Nother, Gunther and Eshelby who dealt with invariant integrals in mathematics, hydrodynamics, electrodynamics, and the theory of dislocations. A brief review is given of the creation of the invariant integral of fracture mechanics under static and dynamic conditions for a solid continuum including elastic, plastic and viscoelastic materials, as well as of some of its most important applications, ramifications and generalizations for other physical fields. The initial phase of the expansion and revolution of the large-scale universe is studied in the framework of the neoclassic approach, including the Big Bang and the Dark Energy; it is shown that the spheroidal shape of the universe assumed at the Big Bang retains its eccentricity constant in the initial phase. The assumption of a superphoton as a primordial universe was analyzed.

If the Standard Model (SM) Higgs is weakly coupled to the inflationary sector, the Higgs is expected to be universally in the form of a condensate towards the end of inflation. The Higgs decays rapidly after inflation - via non-perturbative effects - into an out-of-equilibrium distribution of SM species, which thermalize soon afterwards. If the post-inflationary equation of state of the universe is stiff, $w \simeq +1$, the SM species eventually dominate the total energy budget. This provides a natural origin for the relativistic thermal plasma of SM species, required for the onset of the `hot Big Bang' era. The viability of this scenario requires the inflationary Hubble scale $H_*$ to be lower than the instability scale for Higgs vacuum decay, the Higgs not to generate too large curvature perturbations at cosmological scales, and the SM dominance to occur before Big Bang Nucleosynthesis. We show that successful reheating into the SM can only be obtained in the presence of a non-minimal coupling to gravity $\xi \gtrsim 1$, with a reheating temperature of $T_{\rm RH} \gtrsim \mathcal{O}(10^{10})\xi^{3/2}(H_*/10^{14}{\rm GeV})^2~{\rm GeV}$., Comment: 6 pages, 2 figures, minor changes with new figures to match published version in PLB

The high-energy limit of Quantum Chromodynamics is generated by the contraction of its gauge groups. Contraction parameters are taken identical with those of the Electroweak Model and tend to zero when energy increases. At the infinite energy limit all quarks lose masses and have only one color degree of freedom. The limit model represents the development of Quantum Chromodynamics in the early Universe from the Big Bang up to the end of several milliseconds.

The accelerated expansion of our universe results from properties of dark matter particles deduced from Space-Time Quantization. This theory accounts for all possible elementary particles by considering a quantum of length a in addition to c and h. It appears that dark matter particles allow for fusion and fission processes. The resulting equilibrium enables the cosmic dark matter gas to produce dark energy in an adaptive way. It keeps the combined matter-energy density at a constant level, even when space is expanding. This accounts for the cosmological constant Λ and the accelerated expansion of space without requiring any negative pressure. The Big Bang is related to G, c, h and a. It started with a “primeval photon” and led to the cosmic matter-antimatter asymmetry as well as inflation.

We consider the implications of the swampland conjectures on scalar-tensor theories defined in the Einstein frame in which the scalar interaction is screened. We show that chameleon models are not in the swampland provided the coupling to matter is larger than unity and the mass of the scalar field is much larger than the Hubble rate. We apply these conditions to the inverse power law chameleon and the symmetron. We then focus on the dilaton of string theory in the strong coupling limit, as defined in the string frame. We show that solar system tests of gravity imply that viable dilaton models are not in the swampland. In the future of the Universe, if the low energy description with a single scalar is still valid and the coupling to matter remains finite, we find that the scalar field energy density must vanish for models with the chameleon and symmetron mechanisms. Hence in these models dark energy is only a transient phenomenon. This is not the case for the strongly coupled dilaton, which keeps evolving slowly, leading to a quasi de Sitter space-time., 24 pages

We argue that the modified Landau–Raychaudhuri equations should first be analysed in a large class of spacetimes and in dependence on various equations of states, before endorsing any conclusion about (non)singular Big Bang. From the corrected entropy-area law in a large class of metrics, the generalized uncertainty principle (GUP) and the modified dispersion relation (MDR) approaches, and various equations of states, the modified Friedmann equations are derived. They are applied on Landau–Raychaudhuri equations in emergence of cosmic space framework from fixed point method. We show that any conclusion about (non)singular Big Bang is simply badly model-dependent, especially when utilizing GUP and MDR approaches, which can not replace a good theory for quantum gravity. We conclude that the various quantum gravity approaches, metrics and equations of state lead to different modifications in Friedmann and Landau–Raychaudhuri equations and thus to different (non)singular solutions for Big Bang theory.

Similarities in the birth and development of cosmic and biologic systems provide unexpected proof for the major theories of formation of the universe - the Big Bang and the String theories. They include similarities in the theory of their formation, one unit origin, preexisting states, conception, fertilization, gestation, information, basic units, flatness, fluctuations, smoothness, lumpiness, reproductive and excretive organs, differentiation, composition, organization, function, expansion and homeostasis. Based on these similarities, alternative suggestions are proposed to explain various past and present cosmic events and phenomena, and to predict the future of the universe. The relevance of these predictions could be far reaching, and could revolutionize major concepts in cosmology. Key words: Cosmology, universe, big bang, string theory, biology, hypothesis, similarities, birth, evolution, fate, predictions.

This paper studied the revisions to Einstein’s theory of relativity, introduced the concept of “size mass” and put forward the new relativity mass-velocity formula; and then it put forward Liu’s Cosmological Model, analyzed the nascence, birth and development of the universe, obtained the Universe Moving Equations, and calculated the present universe’s parameters; and it analyzed the conditions that a celestial body occurs the similar big bang and the model that the Galaxy occurred the second big bang. The results show that at its nascence, the universe was a big neutron of which the temperature was 8.876×1012℃, the radius was r0=4.84×1011m and that was at rest, under the action of temperature energy (heat energy) releasing, the center of this big neutron generated repulsive force to the surrounding. Under the common action of the repulsive force and gravitation, at the moment tb=6.77×10-5s, the Big Bang occurred. Since the Big Bang, most celestial bodies have been leaving the center of the universe and spreading around with velocities above 0.47c, and the universe is constantly expanding. When an object moves relative to the absolute frame of reference, its three-dimensional size will shrink by the same proportion. The four-dimensional Minkowski space-time is meaningless. The size mass of a system is reduced, if its temperature is maintained unchangeable, then its energy will be correspondingly reduced, and the other system accepts an increase of size mass, if its temperature is maintained unchangeable, then its energy is correspondingly increased.

This paper presents a mathematical proposition based on zero point energy of the creation of singularity in the current Hot Bing Bang theory of the origin of the universe. The observable universe we live in and can see is finite and is defined by the speed of light. The entire universe is infinite and the observable universe is part of it. Zero point energy exists in the entire universe and at all frequencies up to the Planck frequency. Zero point energy was calculated by Planck. The Casimir effect, predicted by Hendrick Casimir, is caused by zero point energy and has been experimentally proven by S. Lamoreux and U. Mohideen. The author has mathematically calculated that the zero point energy waves up to Planck frequency can combine to create an energy source of colossal amount similar to the singularity of Hot Big Bang theory.

There are many ways that the universe could come to an end. A book that explores them is a fascinating tour of physics

We construct a FLRW universe considering an anisotropic scaling between space and time at extremely high and low energies only. In this context, Friedmann equations contain an additional term arising from spatial curvature which implements nonsingular bounces in the early Universe. The matter content of the model is a nonrelativistic pressureless perfect fluid and radiation. By breaking covariance diffeomorphism also at extreme large scales, an additional term furnishes late-time acceleration due to spatial curvature so that a cosmological constant is not needed. In order to probe the final fate of the universe we also introduce a lower order curvature term which dominates in deep IR. Given the observational parameters we obtain a concrete model in eternal recurrence in which the end of late-time acceleration takes place at a redshift $z \simeq -0.14$ and the universe recollapses at $z\simeq - 0.32$., 8 pages, 6 figures. arXiv admin note: text overlap with arXiv:1710.06911

The Big Freeze: The end of cosmology as an observational science in a cosmological-constant dominated universe. Eternal expansion? Big Crunch?

In a four dimensional manifold formalism we study the evolutionary behavior as well as the ultimate fate of the universe, in the course of which the contribution of dark energy in these phases are investigated. At one stage we get a situation (a condition) where the dark energy contained dominates other types of energies available in this universe. In the model universes we obtain here the dark energy is found to be of $\Lambda$CDM and quintessence types-which bear testimony to being real universes. In one of the cases where the equation of state between the fluid pressure and density is of the type of the van der Waals equation, it is found that our universe may end in dust. And, also, it is seen that the behavior of the deceleration parameter is almost compatible with the recent observation., Comment: 13 pages, 6 figures, Accepted in New Astronomy. arXiv admin note: text overlap with arXiv:1701.00748 by other authors

In this paper, we propose a new pressure parametric model of the total cosmos energy components in a spatially flat Friedmann-Robertson-Walker (FRW) universe and then reconstruct the model into quintessence and phantom scenarios, respectively. By constraining with the datasets of the type Ia supernova (SNe Ia), the baryon acoustic oscillation (BAO) and the observational Hubble parameter data(OHD), we find that $\Omega_{m0}=0.270^{+0.039}_{-0.034}$ at the 1$\sigma$ level and our universe slightly biases towards quintessence behavior. Then we use two diagnostics including $Om(a)$ diagnostic and statefinder to discriminate our model from the cosmology constant cold dark matter ($\Lambda$CDM) model. From $Om(a)$ diagnostic, we find that our model has a relatively large deviation from the $\Lambda$CDM model at high redshifts and gradually approaches the $\Lambda$CDM model at low redshifts and in the future evolution, but they can be easily differentiated from each other at the 1$\sigma$ level all along. By the statefinder, we find that both of quintessence case and phantom case can be well distinguished from the $\Lambda$CDM model and will gradually deviate from each other. Finally, we discuss the fate of universe evolution (named the rip analysis) for the phantom case of our model and find that the universe will run into a little rip stage., Comment: 13 pages, 7 figures and 4 tables

The discovery of the Standard Model Higgs boson opens up a range of speculative cosmological scenarios, from the formation of structure in the early universe immediately after the big bang, to relics from the electroweak phase transition one nanosecond after the big bang, on to the end of the present-day universe through vacuum decay. Higgs physics is wide-ranging, and gives an impetus to go beyond the Standard Models of particle physics and cosmology to explore the physics of ultra-high energies and quantum gravity., Comment: 15 pages, 7 figures

The present work deals with the accretion of two interacting fluids: dark matter and a hypothetical fluid as the holographic dark energy components onto wormhole in a non-flat FRW universe. First of all, following Cruz et al. (Phys. Lett. B 669, 271 2008), we obtained an exact solution of the Einstein’s field equations. Solution describes effectively the actual acceleration and indicates a big rip type future singularity of the universe. After that we have studied the evolution of the mass of wormhole embedded in this FRW universe in order to reproduce a stable universe protected against future-time singularity. We found that the accretion of these dark components leads to a gradual increase of wormhole mass. It is also observed that contrary to the case as shown by Cruz et al. (Phys. Lett. B 669, 271 2008), the big rip singularity of the universe with a divergent Hubble parameter of this dark energy model may be avoided by a big trip. We have established a correspondence between the holographic dark energy with the polytropic gas dark energy model and obtained the potential as well as dynamics of the scalar field which describes the polytropic cosmology.

It is shown that inclusion of the shear stresses to the cosmological evolution can stabilize the Friedmann Big Bang. This results in the existence of the generic solution with isotropic cosmological singularity.

In this paper, we have considered the closed FRW universe filled with two interacting fluids; dark matter and holographic dark energy components. Under certain conditions, this dark energy model is characterised by a big rip type future singularity and therefore a finite life time of the universe (Cruz et al., 2008). As the universe passes through a significant time when the matter and the dark energy densities are roughly comparable between the matter and the dark energy dominated era. So, we calculated the fraction of total life time of the universe when the universe passes through the coincidental stage for this future singularity by considering 1 r o r = ρ M ρ DE r o , where r 0 is any fixed ratio. It has been found that the time for the future singularity t s is very large when the value of the constant c is much closed to zero and the fraction is smaller for smaller values of r 0 . Comparison of the results with the observational data and its importance has also been discussed.

This article is an application of the theory of discrete spaces to cosmology. Its conclusions are necessarily speculative. An interesting aspect is that it gives possible solutions to many pending problems within a unique framework. Let us cite a scenario for the Big-Bang that avoids any initial mathematical singularity, an interpretation of dark matter that does not involve any hadronic matter, a description of the formation of stellar and galactic black holes and, for the later, a description of quasars, their characteristics and their source of energy. Finally dark energy is also given an interpretation through modifications of the laws of gravity.

This paper posits that the Big Bang was started by the creation of the reverse Higgs field as the massless particle-generating field derived from the absorption of the interuniversal void outside of the universe in the reversible multiverse. The interuniversal void surrounding every universe is to prevent the collision of expanding universes which have the inexhaustible resources of space-time to expand. The collision of expanding universes is permanently irreversible, forbidden in the reversible multiverse. To prevent the collision, the interuniversal void detaches the incoming mass-energy in the interuniversal void to keep expanding universes apart without collision. Inside of the universe, the absorbed interuniversal void with the property of the detachment of mass-energy was transformed into the reverse Higgs field that detached adjacent mass-energy in the universe, resulting in the conversion of rest mass (massive particles) into kinetic energy (massless particles) starting the Big Bang. During the Big Bang, the creation of the reverse Higgs field was followed by the conversion of massless particles except photons into massive particles through the absorption of the Higgs bosons. The absorption of the interuniversal void with zero vacuum energy also started the inflation by converting the high vacuum energy universe into the zero vacuum energy universe. The inflation followed by the Big Bang is a part of the reversible cyclic universe which explains the four force fields (the strong force, gravity, the electromagnetic force, and the weak force) and dark energy. During the Big Bang, the Higgs field and the reverse Higgs field produced the digital space structure consisting of attachment space (the Higgs field) denoted as 1 and detachment space (the reverse Higgs field) denoted as 0.

As astronomers further develop an understanding of the fate of the Universe, it is essential to study students’ ideas on the fate of the Universe so that instructors can communicate the field’s current status more effectively. In this study, we examine undergraduate students’ preinstruction ideas of the fate of the Universe in ten semester-long introductory astronomy course sections (ASTRO 101) at three institutions. We also examine students’ postinstruction ideas about the fate of the Universe in ASTRO 101 over five semester-long course sections at one institution. The data include precourse surveys given during the first week of instruction (N=264), postinstruction exam questions (N=59), and interviews. We find that, preinstruction, more than a quarter of ASTRO 101 students either do not respond or respond with “I don’t know” when asked what the long-term fate of the Universe is. We also find that, though the term was not necessarily used, students tend to describe a “big chill” scenario in the preinstruction surveys, among a wide variety of other scenarios. A fraction of students describe the fate of smaller-scale systems, possibly due to confusion of the hierarchical nature of structure in the Universe. Preinstruction, students mention the Universe’s expansion when describing how astronomers know the fate of the Universe but do not discuss how we know the Universe is expanding or the relationship between expansion and the fate of the Universe. Postinstruction, students’ responses shift toward greater degrees of completeness and correctness.

In cyclic theory of universe the scenario is just inverse of the theory of inflation. The cyclic theory model almost solves the problem of homogeneity, isotropy and flatness. It also has relevant cause and effect scenarios of different phenomenon like reheating, contraction of branes and it also shows the thermodynamic relevance. The basic approach of the paper is to satisfy the thermodynamics laws and to formulate the situation of ultimate fate of universe. Each and every phenomena that has been described in cyclic theory of universe has been taken into account while drawing the hypothetical graphs of thermodynamics. While treating thermodynamics with cosmology and astrophysics, many factors have been neglected like shape of universe, the cosmological constant, invariant scalar factor and factors related to the depth of cosmology. The paper also shows the behaviour of pressure, volume and temperature by using arbitrary values. The time and space has been neglected in graphical representation.

We investigate the classical and quantum behavior of a Bianchi I model in the presence of a stiff matter contribution when the Vilenkin interpretation of the wave function of the Universe is taken into account. We study its evolution in the so-called polymer representation of quantum mechanics, in order to characterize the modifications that a discrete nature in the isotropic variable of the Universe induces on the morphology of the cosmological singularity. We demonstrate that in such a model the Big-Bang singularity is removed at a semiclassical level in favor of a Big-Bounce when a lattice on the isotropic variable is considered. Furthermore, the analysis of the mean values on the quantum degrees of freedom, \textit{i.e} the variables $\beta_{+},\beta_{-}$ in the Misner picture, and the investigation on the evolution of the wave packets show how the typical diverging behavior associated to the anisotropies of the Universe in proximity of the initial singularity disappears in our polymer modified scheme. Indeed, the anisotropies remain finite across the Big-Bounce and they assume a value that depends on the initial conditions fixed far from the turning point. Finally, we demonstrate that the proposed scenario can be extended, with a suitable choice of the configuration parameters, to the Bianchi IX cosmology and therefore it can be regarded as a paradigm for the generic cosmological model., Comment: 20 pages, 7 figures

Will the universe continue to expand forever, or will it eventually halt and start to collapse?

The theory of the birth of the Universe in the frame of nonlocal quantum hydrodynamics is considered. The transport equations for the physical vacuum (PV) are delivered. The calculations demonstrate that PV equations for “empty” space have the traveling wave solutions belonging, in particular, to the soliton class. The possible influence and reaction of the background microwave radiation is taken into account. These results lead to the principal correction of the inflation theory and serve as the explanation for the recently discovered Universe's cosmic microwave background anomalies. The simple analytical particular cases and numerical calculations are delivered. The analogue of the Hubble effect in the PV boxes is demonstrated.

We show that Big Bang Nucleosynthesis (BBN) significantly constrains axion-like dark matter. The axion acts like an oscillating QCD $\theta$ angle that redshifts in the early universe, increasing the neutron-proton mass difference at neutron freeze-out. An axion-like particle that couples too strongly to QCD results in the underproduction of 4He during BBN and is thus excluded. The BBN bound overlaps with much of the parameter space that would be covered by proposed searches for time-varying neutron EDMs. The QCD axion does not couple strongly enough to affect BBN., Comment: 5 pages, 2 figures; v2 typos corrected, numerical values for quark masses updated

We discuss problems arising in three very different physical processes: an electron scattering on a nucleus, an experiment with delayed choice, and the cosmological Big Bang. We describe the role of soft and supersoft photons in solutions of the arising problems.

The present work deals with the accretion of two minimally interacting fluids: dark matter and a hypothetical isotropic fluid as the holographic dark energy components onto black hole and wormhole in a spatially homogeneous and anisotropic Bianchi type-V universe. To obtain an exact solution of the Einstein’s field equations, we use the assumption of linearly varying deceleration parameter. Solution describes effectively the actual acceleration and indicates a big rip type future singularity of the universe. We have studied the evolution of the mass of black hole and the wormhole embedded in this anisotropic universe in order to reproduce a stable universe protected against future-time singularity. It is observed that the accretion of these dark components leads to a gradual decrease and increase of black hole and wormhole mass respectively. Finally, we have found that contrary to our previous case (Sarkar in Astrophys. Space. Sci. 341:651, 2014a), the big rip singularity of the universe with a divergent Hubble parameter of this dark energy model may be avoided by a big trip.