Quantum particle production at sudden singularities

Barrow, John D.; Batista, A. B.; Fabris, J. C.; Houndjo, S. J. M.

doi:10.1103/physrevd.78.123508

Cited by 52 publications

(43 citation statements)

References 32 publications

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“…This means that the sudden singularity cannot be avoided from conformal anomaly contribution. This results perfectly agrees with that found in [35,40], where in the framework of GR it has been shown that sudden singularity cannot be avoided both from particle production and conformal anomaly. However, it appears that the avoidance of the sudden singularity could come from the matter contribution, due to the same exponent for R and g T .…”

Section: Conformal Anomaly Near the Sudden Singularitysupporting

confidence: 92%

Finite-time singularities in f(R, T) gravity and the effect of conformal anomaly

et al. 2013

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We investigate f (R, T ) gravity models (where R is the curvature scalar and T is the trace of the stress-energy tensor of ordinary matter) that are able to reproduce the four known types of future finite-time singularities. We choose a suitable expression for the Hubble parameter in order to realise the cosmic acceleration and we introduce two parameters, α and H s , which characterise each type of singularity. We address conformal anomaly and we observe that it cannot remove the Sudden Singularity or the Big Brake, but, for some values of α, the Big Rip and the Big Freeze may be avoided. We also find that, even without taking into account conformal anomaly, the Big Rip and the Big Freeze may be removed thanks to the presence of the T contribution of the f (R, T ) theory.Pacs numbers: 04.50. Kd, 95.35.+d, 95.36.+x, 98.80.Qc

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Section: Conformal Anomaly Near the Sudden Singularitysupporting

confidence: 92%

Finite-time singularities in f(R, T) gravity and the effect of conformal anomaly

et al. 2013

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“…They can also be shown to be stable to small perturbations using standard perturbation theory [11], and one can adapt the arguments above to show they form in expanding, homogeneous universes with large anisotropies. They are even stable to quantum corrections since one can construct examples where the divergence only occurs at an arbitrarily high order of the scale factor derivative [12,13]. This is in contrast to most other examples of weak singularities discovered so far.…”

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confidence: 85%

New singularities in unexpected places

Barrow

Graham

2015

Int. J. Mod. Phys. D

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Spacetime singularities have been discovered which are physically much weaker than those predicted by the classical singularity theorems. Geodesics evolve through them and they only display infinities in the derivatives of their curvature invariants. So far, these singularities have appeared to require rather exotic and unphysical matter for their occurrence. Here we show that a large class of singularities of this form can be found in a simple Friedmann cosmology containing only a scalar-field with a power-law self-interaction potential. Their existence challenges several preconceived ideas about the nature of spacetime singularities and impacts upon the end of inflation in the early universe.A striking feature of relativistic cosmology is the prediction that past and future singularities can occur. Originally, singularities were defined by the existence of incomplete geodesics, and a variety of sufficient conditions for geodesic incompleteness were established by a series of important theorems from 1965-1972 [1]. More recently, by using the Einstein equations, new types of physical singularities have been identified which can occur at finite time and are unaccompanied by geodesic incompleteness [2,3,4]. Many quantities, such as the density and the expansion rate, which diverge at traditional 'big bang' singularities, remain finite whilst other physical quantities, like the pressure, diverge in finite proper time. The simplest example of what is termed a 'sudden' singularity occurs in the zerocurvature Friedmann universe with scale factor a(t) and Hubble rate H =ȧ/a, containing matter with density ρ and pressure p. The field equations are (8πG = 1 = c)These equations permit there to be a finite time, t s , at which a, H, and ρ all remain finite, in accord with Eq. (1), but where p,ρ andä all become infinite, in accord with Eqs. (2)-(3). The key to their existence is in not assuming any functional link between p and ρ, nor any boundedness condition on p, and this freedom allows an acceleration singularityä → ∞ to arise at finite time as t → t s because of a divergence in the matter pressure, p → ∞. Here is an explicit example. On the time interval 0 ≤ t ≤ t s , we can choose a solution for the scale factor a(t) of the formwhere a s ≡ a(t s ), q and n are positive constants. If t → t s from below then a → a s , H → H s and ρ → ρ s > 0, where a s , H s , and ρ s are all finite, but p → ∞ andä → −∞ whenever 1 < n < 2 and 0 < q ≤ 1. As t → 0 we *

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“…[12][13][14][15][16][17][18] and for discussions of quantum effects see Refs. [19,20]. Sudden singularities stand in stark contrast to big rip singularities as they are much weaker.…”

Section: Introductionmentioning

confidence: 99%

Singular inflation

Barrow

Graham

2015

Phys. Rev. D

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We prove that a homogeneous and isotropic universe containing a scalar field with a power-law potential, V (φ) = Aφ n , with 0 < n < 1 and A > 0 always develops a finite-time singularity at which the Hubble rate and its first derivative are finite, but its second derivative diverges. These are the first examples of cosmological models with realistic matter sources that possess weak singularities of 'sudden' type. We also show that a large class of models with even weaker singularities exist for noninteger n > 1. More precisely, if k < n < k + 1 where k is a positive integer then the first divergence of the Hubble rate occurs with its (k + 2)th derivative. At early times these models behave like standard large-field inflation models but they encounter a singular end-state when inflation ends. We term this singular inflation.

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Quantum particle production at sudden singularities

Cited by 52 publications

References 32 publications

Finite-time singularities in f(R, T) gravity and the effect of conformal anomaly

Finite-time singularities in f(R, T) gravity and the effect of conformal anomaly

New singularities in unexpected places

Singular inflation

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