Future singularities if the universe underwent Starobinsky inflation in the past

Carlson, Eric D.; Anderson, Paul R.; Einhorn, John R.; Hicks, Bradley; Lundeen, Andrew J.

doi:10.1103/physrevd.95.044012

Cited by 28 publications

(9 citation statements)

References 87 publications

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“…Moreover, also due to the long period of accelerated expansion, we treat the Universe as empty when entering into the contraction phase. Therefore we call this phase of the cycle -a ripping phase, with the crucial difference with respect to the previously proposed Big rip scenarios [64,97,98] that the scale factor remains always finite. This means that the contribution of the effective energy density contained in the modified terms needs to increase with time, in order to become significantly large to destroy all bounded systems in the Universe.…”

Section: Phase Of Standard Cosmology and The Rip Phasementioning

confidence: 93%

“…characterized by equation of state (EOS) parameter w = p/ρ < −1, with ρ dark energy density and p dark energy pressure, also played a significant role in cyclic models. If dark energy is characterized by w < −1 then its energy density becomes so dominant that it destroys every gravitationally bounded system until it diverges in the Big Rip singularity [64] (for a recent discussion on the effects of quantum fields and second-order curvature correction in the gravitational Lagrangian on future singularities see [65]). Using this fact, together with some mechanism that could start a contraction before the Big Rip singularity is reached, the Universe could be treated as essentially empty at contraction, and then also black holes can disappear due to the failing of the Hawking area theorem [66].…”

Section: Models Of Cyclic Cosmologymentioning

confidence: 99%

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Cyclic cosmology in modified gravity

Pavlović

Sossich

2017

Phys. Rev. D

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In this work we propose a new general model of eternal cyclic Universe. We start from the assumption that quantum gravity corrections can be effectively accounted by the addition of higher order curvature terms in the Lagrangian density for gravity. It is also taken into account that coefficients associated with these curvature corrections will in general be dependent on a curvature regime. We therewith assume no new ingredients, such as extra dimensions, new scalar fields, phantom energy or special space-time geometries. Evolution of the Universe in this framework is studied and general properties of each phase of the cycle -cosmological bounce, low curvature (ΛCDM) phase, destruction of bounded systems and contracting phase -are analysed in detail. Focusing on some simple special cases, we obtain analytical and numerical solutions for the each phase confirming our analysis.

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Section: Phase Of Standard Cosmology and The Rip Phasementioning

confidence: 93%

Section: Models Of Cyclic Cosmologymentioning

confidence: 99%

Cyclic cosmology in modified gravity

Pavlović

Sossich

2017

Phys. Rev. D

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“…The quasi-GPDs H T,Q(0) and H T,Q(3) corresponding to two different Dirac structures are related through Eq. (38). This is the only quasi-GPD whose two different projections have such a simple relation.…”

Section: B Results For Quasi-gpdsmentioning

confidence: 87%

Studying twist-2 GPDs through quasi-distributions in a scalar diquark model

Bhattacharya¹,

Cocuzza²,

Metz³

2019

Proceedings of XXVII International Workshop on Deep-Inelastic Scattering and Related Subjects — PoS(DIS2019)

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Quasi parton distributions (quasi-PDFs) are currently under intense investigation. Quasi-PDFs are defined through spatial correlation functions and are thus accessible in lattice QCD. They gradually approach their corresponding standard (light-cone) PDFs as the hadron momentum increases. Recently, we investigated the concept of quasi-distributions in the case of generalized parton distributions (GPDs) by calculating the twist-2 vector GPDs in the scalar diquark spectator model. In the present work, we extend this study to the remaining six leading-twist GPDs. For large hadron momenta, all quasi-GPDs analytically reduce to the corresponding standard GPDs. We also study the numerical mismatch between quasi-GPDs and standard GPDs for finite hadron momenta. Furthermore, we present results for quasi-PDFs, and explore higher-twist effects associated with the parton momentum and the longitudinal momentum transfer to the target. We study the dependence of our results on the model parameters as well. Finally, we discuss the lowest moments of quasi distributions, and elaborate on the relation between quasi-GPDs and the total angular momentum of quarks. The moment analysis suggests a preferred definition of several quasi-distributions. I. INTRODUCTIONParton distribution functions (PDFs) are important objects encoding information about the quark and gluon structure of hadrons [1]. They can be extracted from data for a large class of hard scattering processes, where the key underlying tool is factorization theorems in quantum chromodynamics (QCD) that separate the perturbatively calculable short distance part of a cross section from the long-distance part described by PDFs and other potential non-perturbative quantities [2]. On the other hand, first-principles calculations of PDFs using lattice QCD have remained challenging due to their explicit time-dependence. As a result, in the past almost all related studies in lattice QCD focused on moments of PDFs which are defined through time-independent local operators, while the full dependence of PDFs on the parton momentum fraction x remained elusive.The recently proposed quasi parton distributions (quasi-PDFs) offer a way to directly access the x-dependence of the PDFs in lattice QCD [3,4]. Quasi-PDFs are defined through spatial equal-time operators that can be computed on four-dimensional Euclidean lattices. They reduce to their corresponding standard (light-cone) PDFs if the hadron momentum P 3 = | P | → ∞, prior to renormalization. However, for lattice calculations one first renormalizes, and P 3 is finite. This leads to two sources of discrepancies between quasi-PDFs and standard PDFs: higher-twist corrections that are suppressed by powers of 1 P 3 , and a different ultraviolet (UV) behavior for these two types of PDFs. The UV disparities can be cured order by order in perturbative QCD through a so-called matching procedure -see for instance . Other approaches for computing the x-dependence of PDFs and related quantities have also been suggested [8][9][10][11][12][13][14][15...

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“…(A rather complex classification of different possible future singularities is given in, e.g., Ref. [122] Sec. IA. )…”

Section: Big Crunch With Dark Energy In Semiclassical Cosmologymentioning

confidence: 99%

“…IA. ) Assuming that the dark energy which causes these singularities to behave like a perfect fluid, Carlson et al [122] studied the effects which quantum fields and an α 0 R 2 term in the gravitational Lagrangian have on future singularities. Special emphasis was placed on those values of α 0 which are compatible with the universe having undergone Starobinsky inflation [123] in the past, the same values which allow for stable solutions to the semiclassical backreaction equations in the present universe.…”

Section: Big Crunch With Dark Energy In Semiclassical Cosmologymentioning

confidence: 99%

Weyl Curvature Hypothesis in Light of Quantum Backreaction at Cosmological Singularities or Bounces

2021

Universe

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The Weyl curvature constitutes the radiative sector of the Riemann curvature tensor and gives a measure of the anisotropy and inhomogeneities of spacetime. Penrose’s 1979 Weyl curvature hypothesis (WCH) assumes that the universe began at a very low gravitational entropy state, corresponding to zero Weyl curvature, namely, the Friedmann–Lemaître–Robertson–Walker (FLRW) universe. This is a simple assumption with far-reaching implications. In classical general relativity, Belinsky, Khalatnikov and Lifshitz (BKL) showed in the 70s that the most general cosmological solutions of the Einstein equation are that of the inhomogeneous Kasner types, with intermittent alteration of the one direction of contraction (in the cosmological expansion phase), according to the mixmaster dynamics of Misner (M). How could WCH and BKL-M co-exist? An answer was provided in the 80s with the consideration of quantum field processes such as vacuum particle creation, which was copious at the Planck time (10−43 s), and their backreaction effects were shown to be so powerful as to rapidly damp away the irregularities in the geometry. It was proposed that the vaccum viscosity due to particle creation can act as an efficient transducer of gravitational entropy (large for BKL-M) to matter entropy, keeping the universe at that very early time in a state commensurate with the WCH. In this essay I expand the scope of that inquiry to a broader range, asking how the WCH would fare with various cosmological theories, from classical to semiclassical to quantum, focusing on their predictions near the cosmological singularities (past and future) or avoidance thereof, allowing the Universe to encounter different scenarios, such as undergoing a phase transition or a bounce. WCH is of special importance to cyclic cosmologies, because any slight irregularity toward the end of one cycle will generate greater anisotropy and inhomogeneities in the next cycle. We point out that regardless of what other processes may be present near the beginning and the end states of the universe, the backreaction effects of quantum field processes probably serve as the best guarantor of WCH because these vacuum processes are ubiquitous, powerful and efficient in dissipating the irregularities to effectively nudge the Universe to a near-zero Weyl curvature condition.

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Future singularities if the universe underwent Starobinsky inflation in the past

Cited by 28 publications

References 87 publications

Cyclic cosmology in modified gravity

Cyclic cosmology in modified gravity

Studying twist-2 GPDs through quasi-distributions in a scalar diquark model

Weyl Curvature Hypothesis in Light of Quantum Backreaction at Cosmological Singularities or Bounces

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