Showing papers on "Big Rip published in 2003"
TL;DR: In this article, the authors explore the consequences that follow if the dark energy is phantom energy, in which the sum of the pressure and energy density is negative, and the positive phantom energy density becomes infinite in finite time, overcoming all other forms of matter, such that the gravitational repulsion rapidly brings our brief epoch of cosmic structure to a close.
Abstract: We explore the consequences that follow if the dark energy is phantom energy, in which the sum of the pressure and energy density is negative. The positive phantom-energy density becomes infinite in finite time, overcoming all other forms of matter, such that the gravitational repulsion rapidly brings our brief epoch of cosmic structure to a close. The phantom energy rips apart the Milky Way, solar system, Earth, and ultimately the molecules, atoms, nuclei, and nucleons of which we are composed, before the death of the Universe in a "big rip."
2,177 citations
TL;DR: The 95% confidence level lower limit on the age of the Universe of 11.2 billion years means that the three fundamental observables in cosmology now independently support the case for a dark energy–dominated Universe.
Abstract: Recent observations of stellar globular clusters in the Milky Way Galaxy, combined with revised ranges of parameters in stellar evolution codes and new estimates of the earliest epoch of globular cluster formation, result in a 95% confidence level lower limit on the age of the Universe of 11.2 billion years. This age is inconsistent with the expansion age for a flat Universe for the currently allowed range of the Hubble constant, unless the cosmic equation of state is dominated by a component that violates the strong energy condition. This means that the three fundamental observables in cosmology-the age of the Universe, the distance-redshift relation, and the geometry of the Universe-now independently support the case for a dark energy-dominated Universe.
335 citations
TL;DR: In this paper, the authors analyze the cosmological dynamics of phantom fields in a variety of potentials unbounded from above and demonstrate that the nature of future evolution generically depends upon the steepness of the phantom potential and discuss the fate of Universe accordingly.
Abstract: In this paper we analyze the cosmological dynamics of phantom field in a variety of potentials unbounded from above. We demonstrate that the nature of future evolution generically depends upon the steepness of the phantom potential and discuss the fate of Universe accordingly.
267 citations
TL;DR: In this paper, the authors show that there are certain unified models for dark energy which are stable to perturbations in matter density where the presence of phantom energy does not lead to such a cosmic doomsday.
Abstract: Phantom energy which violates the dominant-energy condition and is not excluded by current constraints on the equation of state may be dominating the evolution of the universe now. It has been pointed out that in such a case the fate of the universe may be a big rip where the expansion is so violent that all galaxies, planets and even atomic nuclei will be successively ripped apart in finite time. Here we show, however, that there are certain unified models for dark energy which are stable to perturbations in matter density where the presence of phantom energy does not lead to such a cosmic doomsday.
240 citations
TL;DR: In the last decade, a series of advances in both theory and technology have launched cosmology into its most exciting period of discovery yet as discussed by the authors, and promising ideas for understanding the basic features of the universe are being tested, and deep connections between physics on the smallest scales and on the largest scales are being revealed.
Abstract: Revolutionary advances in both theory and technology have launched cosmology into its most exciting period of discovery yet. Unanticipated components of the universe have been identified, promising ideas for understanding the basic features of the universe are being tested, and deep connections between physics on the smallest scales and on the largest scales are being revealed.
172 citations
TL;DR: In this paper, the authors focus on quintessence, a time-evolving, spatially inhomogeneous component with negative pressure, and how it may affect the overall cosmic history of the universe.
Abstract: Most of the energy in the Universe consists of some form of dark energy that is gravitationally self-repulsive and that is causing the expansion of the Universe to accelerate. The possible candidates are a vacuum energy density (or, equivalently, a cosmological constant) and quintessence, a time-evolving, spatially inhomogeneous component with negative pressure. In this review, we focus on quintessence and ideas on how it might solve the cosmic coincidence problem, how it might be distinguished observationally from a cosmological constant, and how it may affect the overall cosmic history of the Universe.
150 citations
TL;DR: In this paper, the properties of the behavior of classical cosmological perturbations when the universe experiences a bounce are investigated. But the authors focus on the case where gravity is described by general relativity and the matter content has a single component, namely a scalar field in a closed geometry.
Abstract: We clarify the properties of the behavior of classical cosmological perturbations when the Universe experiences a bounce. This is done in the simplest possible case for which gravity is described by general relativity and the matter content has a single component, namely, a scalar field in a closed geometry. We show in particular that the spectrum of scalar perturbations can be affected by the bounce in a way that may depend on the wave number, even in the large scale limit. This may have important implications for string motivated models of the early Universe.
117 citations
TL;DR: In this paper, the authors describe a class of models where the flatness of the universe can be resolved by fine-tuning the total number of e-folds to be sufficiently small.
Abstract: It is very difficult to obtain a realistic model of a closed inflationary universe. Even if one fine-tunes the total number of e-folds to be sufficiently small, the resulting universe typically has large density perturbations on the scale of the horizon. We describe a class of models where this problem can be resolved. The models are unattractive and fine-tuned, so the flatness of the universe remains a generic prediction of inflationary cosmology. Nevertheless one should keep in mind that with the fine-tuning at the level of about one percent one can obtain a semi-realistic model of a closed inflationary universe. The spectrum of density perturbations in this model may have a cut-off on the scale of the horizon. Similar approach may be valid in application to a compact inflationary universe with a nontrivial topology.
113 citations
TL;DR: In this article, the authors describe a class of models where the flatness of the universe can be resolved by fine-tuning the total number of e-folds to be sufficiently small.
Abstract: It is very difficult to obtain a realistic model of a closed inflationary universe. Even if one fine-tunes the total number of e-folds to be sufficiently small, the resulting universe typically has δρ/ρ~ΔT/T = O(1) on the scale of the horizon. We describe a class of models where this problem can be resolved. The models are unattractive and fine-tuned, so the flatness of the universe remains a generic prediction of inflationary cosmology. Nevertheless one should keep in mind that with the fine-tuning at the level of about one per cent one can obtain a semi-realistic model of an inflationary universe with Ω>1. The spectrum of density perturbations in this model may have a cut-off on the scale of the horizon. A similar approach may be valid in application to a compact inflationary universe with a nontrivial topology.
105 citations
TL;DR: In this paper, the role of the renormalization-group running of the cosmological constant (CC) in determining the ultimate fate of the universe was investigated for a generic quantum field theory.
Abstract: For a generic quantum field theory we study the role played by the renormalization-group (RG) running of the cosmological constant (CC) in determining the ultimate fate of the universe. We consider the running of the CC of generic origin (the vacuum energy of quantum fields and the potential energy of classical fields), with the RG scale proportional to the (total energy density$\rm{)^{1/4}}$ as the most obvious identification. Starting from the present-era values for cosmological parameters we demonstrate how the running can easily provide a negative cosmological constant, thereby changing the fate of the universe, at the same time rendering compatibility with critical string theory. We also briefly discuss the recent past in our scenario.
102 citations
TL;DR: In this article, the authors simulate the future evolution of the observed inhomogeneities in the local universe assuming that the global expansion rate is dominated by a cosmological constant, and they find that within two Hubble times (∼30 billion years) from the present epoch, large-scale structures will freeze in co-moving coordinates and the mass distribution of bound objects will stop evolving.
TL;DR: In this paper, it was shown that the data from SNAP and Planck satellites may extend the bound on the 'doomsday' time to 40 billion years at the 95% confidence level.
Abstract: Recently it was found, in a broad class of models, that the dark energy density may change its sign during the evolution of the universe. This may lead to a global collapse of the universe within the time tc ~ 1010–1011 years. Our goal is to find what bounds on the future lifetime of the universe can be placed by the next generation of cosmological observations. As an example, we investigate the simplest model of dark energy with a linear potential V() = V0(1 + α). This model can describe the present stage of acceleration of the universe if α is small enough. However, eventually the field rolls down, V() becomes negative, and the universe collapses. The existing observational data indicate that the universe described by this model will collapse not earlier than tc 10 billion years from the present moment. We show that the data from SNAP and Planck satellites may extend the bound on the `doomsday' time to tc 40 billion years at the 95% confidence level.
TL;DR: In this article, the authors examined the immediate and longer term consequences of dark energy (assumed here to have a constant density) and presented criteria for test bodies to remain bound to existing structures, showing that collapsed halos become spatially isolated and dynamically relax to a particular density profile with logarithmic slope steeper than -3 at radii beyond r200.
Abstract: Current cosmological data indicate that our universe contains a substantial component of dark vacuum energy that is driving the cosmos to accelerate. We examine the immediate and longer term consequences of this dark energy (assumed here to have a constant density). Using analytic calculations and supporting numerical simulations, we present criteria for test bodies to remain bound to existing structures. We show that collapsed halos become spatially isolated and dynamically relax to a particular density profile with logarithmic slope steeper than -3 at radii beyond r200. The asymptotic form of the spacetime metric is then specified. We develop this scenario further by determining the effects of the accelerating expansion on the background radiation fields and individual particles. In an appendix, we generalize these results to include quintessence.
TL;DR: In this paper, the authors studied the evolution of Born-Infeld-type phantom in the second Randall-Sundrum brane scenario, and found that there exists an attractor solution for the potential with a maximum, which implies a cosmological constant at the late time.
Abstract: We study the evolution of Born-Infeld-type phantom in the second Randall-Sundrum brane scenario, and find that there exists attractor solution for the potential with a maximum, which implies a cosmological constant at the late time. Especially, we discuss the BI model of constant potential without and with dust matter. In the weak tension limit of the brane, we obtain an exact solution for the BI phantom and scale factor and show that there is no big rip during the evolution of the brane.
TL;DR: In this paper, the future fate of the universe, for simple linear models of the dark energy equation-of-state, can vary between the extremes of (I) a divergence of the scale factor in as little as 7 Gyr, (II) an infinite lifetime with dark energy dominant for all future time, and (III) a disappearing dark energy where the universe asymptotes as t →∞ to a ( t )∼ t 2/3, i.e., matter domination.
TL;DR: In this paper, the authors studied the time evolution of the corresponding effective 4D cosmological model supplemented by cold dark matter and showed that it is marginally possible to describe observational data for the late-time cosmic acceleration in this model.
Abstract: Recently it was observed that the hyperbolic compactification of M/string theory related to S-branes may lead to a transient period of acceleration of the universe. We study time evolution of the corresponding effective 4d cosmological model supplemented by cold dark matter and show that it is marginally possible to describe observational data for the late-time cosmic acceleration in this model. However, investigation of the compactification 11d → 4d suggests that the Compton wavelengths of the KK modes in this model are of the same order as the size of the observable part of the universe. Assuming that this problem, as well as several other problems of this scenario, can be resolved, we propose a possible solution of the cosmological coincidence problem due to the relation between the dark energy density and the effective dimensionality of the universe.
TL;DR: In this article, a model of the universe in which dark energy is modelled explicitely with both a dynamical quintessence field and a cosmological constant is presented.
Abstract: In this work we present a model of the universe in which dark energy is modelled explicitely with both a dynamical quintessence field and a cosmological constant. Our results confirm the possibility of a future collapsing universe (for a given region of the parameter space), which is necessary for a consistent formulation of string theory and quantum field theory. We have also reproduced the measurements of modulus distance from supernovae with good accuracy.
TL;DR: In this paper, it was shown that in many models based on supergravity, the dark energy eventually becomes negative and the universe collapses within a time comparable to the present age of the universe.
Abstract: It is often assumed that in the course of the evolution of the Universe, the dark energy either vanishes or becomes a positive constant. However, recently it was shown that in many models based on supergravity, the dark energy eventually becomes negative and the Universe collapses within a time comparable to the present age of the Universe. We will show that this conclusion is not limited to the models based on supergravity: in many models describing the present stage of acceleration of the Universe the dark energy eventually becomes negative, which triggers the collapse of the Universe within the time t = 1010 –1011 years. Theories of this type have certain distinguishing features that can be tested by cosmological observations.
TL;DR: In this paper, a cosmological D bound on the entropy of matter in the universe was introduced, and the Friedmann equation was shown to coincide with the Cardy-Verlinde formula.
Abstract: We discuss the holographic principle in a radiation-dominated, closed Friedmann-Robertson-Walker universe with a positive cosmological constant. By introducing a cosmological D bound on the entropy of matter in the universe, we can write the Friedmann equation governing the evolution of the universe in the form of the Cardy formula. When the cosmological D bound is saturated, the Friedmann equation coincides with the Cardy-Verlinde formula describing the entropy of radiation in the universe. As a concrete model, we consider a brane universe in the background of Schwarzschild-de Sitter black holes. It is found that the cosmological D bound is saturated when the brane crosses the black hole horizon of the background. At that moment, the Friedmann equation coincides with the Cardy-Verlinde formula describing the entropy of radiation matter on the brane.
TL;DR: In this paper, the authors examined the possibility that thermal, rather than quantum, fluctuations are responsible for seeding the structure of our universe and found that while the thermalization condition leads to nearly Gaussian statistics, a Harrisson-Zeldovich spectrum for the primordial fluctuations can only be achieved in very special circumstances.
Abstract: We examine the possibility that thermal, rather than quantum, fluctuations are responsible for seeding the structure of our universe. We find that while the thermalization condition leads to nearly Gaussian statistics, a Harrisson-Zeldovich spectrum for the primordial fluctuations can only be achieved in very special circumstances. These depend on whether the universe gets hotter or colder in time, while the modes are leaving the horizon. In the latter case we find a no-go theorem which can only be avoided if the fundamental degrees of freedom are not particlelike, such as in string gases near the Hagedorn phase transition. The former case is less forbidding, and we suggest two potentially successful ``warming universe'' scenarios. One makes use of the Phoenix universe, the other of ``phantom'' matter.
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TL;DR: In this article, it was shown that inflation can occur in the core of a Q-ball and that it can occur even in the case of Q-balls with a fixed number of players.
Abstract: We show that inflation can occur in the core of a Q-ball.
TL;DR: In this article, a variational formalism of the gravitational field in a Weyl?Cartan spacetime is developed in the exterior form language and the existence of two points of inflection of the scale factor function is established, the first corresponds to the early stage of the universe and the second to the modern era.
Abstract: The perfect dilaton?spin fluid (as a model of the dilaton matter, the particles of which are endowed with intrinsic spin and dilaton charge) is considered as the source of the gravitational field in a Weyl?Cartan spacetime. The variational formalism of the gravitational field in a Weyl?Cartan spacetime is developed in the exterior form language. A homogeneous and isotropic universe filled with the dilaton matter as the dark matter is considered and one of the field equations is represented as the Einstein-like equation which leads to the modified Friedmann?Lema?tre equation. From this equation the absence of the initial singularity in the cosmological solution follows. Also the existence of two points of inflection of the scale factor function is established, the first of which corresponds to the early stage of the universe and the second to the modern era when the expansion with deceleration is replaced by the expansion with acceleration. Possible equations of state for the self-interacting cold dark matter are found on the basis of the modern observational data. An inflation-like solution is obtained.
TL;DR: In this article, the authors proposed a model in which the cosmic effective Yang-Mills condensate familiar in particle physics plays the role of the dark energy that causes the acceleration of the universe.
Abstract: Recent observations of large scale structure of the Universe, especially that of Type Ia supernovae, indicate that the Universe is flat and is accelerating, and that the dominant energy density in the Universe is the cosmic dark energy. We propose a model in which the cosmic effective Yang-Mills condensate familiar in particle physics plays the role of the dark energy that causes the acceleration of the Universe. Since the quantum effective Yang-Mills field in certain states has the equation of state py = −ρy, when employed as the cosmic matter source, it naturally results in an accelerating expansion of the Universe. With the matter components (Ωm ∼ 1/3) being added into the model, the composition of YM condensate and matter components can give rise to the desired equation of state w ∼ −2/3 for the Universe.
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TL;DR: In this paper, the scalar field Einstein equations with the negative kinetic field term were cut out, their boundaries being sewn together in such a way that neither the scale factor nor density or pressure will experience a jump.
Abstract: There exists a variety of exact solutions of the scalar field Einstein equations, allowing for ``phantom regions'' with the negative kinetic field term. These regions can be cut out, their boundaries being sewn together in such a way that neither the scale factor (along with its first two derivatives) nor density or pressure will experience a jump. Such a domain surgery eliminates the ``Big Rip'' scenario, substituting for it the standard inflation.
TL;DR: In this article, the back-reaction effect of the neutrino field at finite temperature in the background of the static Einstein universe is investigated, and a relationship between the temperature of the universe and its radius is found.
Abstract: The back-reaction effect of the neutrino field at finite temperature in the background of the static Einstein universe is investigated. A relationship between the temperature of the universe and its radius is found. As in previously studied cases of the massless scalar field and the photon field, this relation exhibits a minimum radius below which no self-consistent solution for the Einstein field equation can be found. A maximum temperature marks the transition from a vacuum-dominated state to the radiation-dominated state universe. In light of the results obtained for the scalar, neutrino and photon fields, the role of the back reaction of quantum fields in controlling the value of the cosmological constant is briefly discussed.
TL;DR: In this article, the time-varying density of D-branes and anti-Dbranes in an expanding universe is calculated and it is shown that small dimension Dbranes annihilate more slowly than high dimension branes, which leads to an attractive dynamical way to create a realistic braneworld scenario.
Abstract: The time-varying density of D-branes and anti-D-branes in an expanding universe is calculated. The D-brane anti-brane annihilation rate is shown to be too small to compete with the expansion rate of a FRW type universe and the branes over-close the universe. This brane problem is analogous to the old monopole problem. Interestingly however, it is shown that small dimension D-branes annihilate more slowly than high dimension branes. Hence, an initially brany universe may be filled with only low dimension branes at late times. When combined with an appropriate late inflationary theory this leads to an attractive dynamical way to create a realistic braneworld scenario.
TL;DR: In this paper, a spatially homogeneous and isotropic Robertson-Walker model with zero-curvature of the universe is studied in Saez-Ballester scalar-tensor theory.
Abstract: A spatially homogeneous and isotropic Robertson-Walker model with zero-curvature of the universe is studied in Saez-Ballester scalar-tensor theory. Exact solutions of the field equations are obtained for two different early phases of the universe viz. the inflationary and the radiation-dominated phases by using gamma-law equation of state p=(γ-1)ρ in the presence of perfect fluid. The γ-index describing the material content varies continuously with cosmic time so that in the course of its evolution, the universe goes through a transition from an inflationary phase to a radiation-dominated phase. The coupling parameterω is allowed to depend on the cosmic time. The nature of scalar field and other physical significance have also been discussed.
TL;DR: In this paper, a (4 + D)-dimensional Kaluza-Klein cosmology with a Robertson-Walker type metric having two scale factors a and R was studied, corresponding to a D-dimensional internal space and four-dimensional universe, respectively.
Abstract: We study a (4 + D)-dimensional Kaluza–Klein cosmology with a Robertson–Walker type metric having two scale factors a and R, corresponding to a D-dimensional internal space and four-dimensional universe, respectively. By introducing exotic matter as the spacetime part of the higher dimensional energy–momentum tensor, a four-dimensional decaying cosmological term appears as Λ ~ R−2, playing the role of an evolving dark energy in the universe. The resulting field equations yield the exponential solutions for the scale factors. These exponential behaviours may account for the dynamical compactification of extra dimensions and the accelerating expansion of the four-dimensional universe in terms of the Hubble parameter. The acceleration of the universe may be explained by the negative pressure of the exotic matter. It is shown that the rate of compactification of higher dimensions depends on the dimension, D. We then obtain the Wheeler–DeWitt equation and find the general exact solutions in D dimensions. A good correspondence between the classical solutions and the Wheeler–DeWitt solutions in any dimension, D, is obtained.
TL;DR: In this article, the instability against spatially homogeneous and anisotropic perturbations of the Kantowski-Sachs type during different cosmological epochs was analyzed and it was shown that the universe must be open or flat if it underwent a matter-dominated and/or radiation-dominated era in its past evolution.
Abstract: In this paper, by analyzing the instability against spatially homogeneous and anisotropic perturbations of the Kantowski-Sachs type during different cosmological epochs, we show that it is a theoretical consequence of general relativity that the KS universe must be open or flat if it underwent a matter-dominated and/or radiation-dominated era in its past evolution, which theoretically confirms the flatness of our observable Universe.