Quantum correlators in Friedmann spacetimes: The omnipresent de Sitter spacetime and the invariant vacuum noise

Lochan, Kinjalk; Rajeev, Karthik; Vikram, Amit; Padmanabhan, Τ.

doi:10.1103/physrevd.98.105015

Cited by 21 publications

(32 citation statements)

References 70 publications

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“…The cosmological event horizon is present in the empty de Sitter spacetime as well and it has thermal characteristics, see e.g. [15,16,17] and references therein for various aspects of de Sitter particle creation, vacuum states, thermodynamics and de Sitter holography.…”

Section: Introductionmentioning

confidence: 99%

Particle creation by de Sitter black holes revisited

Bhattacharya

2018

Phys. Rev. D

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Creation of thermal distribution of particles by a black hole is independent of the detail of gravitational collapse, making the construction of the eternal horizons suffice to address the problem in asymptotically flat spacetimes. For eternal de Sitter black holes however, earlier studies have shown the existence of both thermal and non-thermal particle creation, originating from the non-trivial causal structure of these spacetimes. Keeping this in mind we consider this problem in the context of a quasistationary gravitational collapse occurring in a (3 + 1)-dimensional eternal de Sitter, settling down to a Schwarzschild-or Kerr-de Sitter spacetime and consider a massless minimally coupled scalar field. There is a unique choice of physically meaningful 'in' vacuum here, defined with respect to the positive frequency cosmological Kruskal modes localised on the past cosmological horizon C − , at the onset of the collapse. We define our 'out' vacuum at a fixed radial coordinate 'close' to the future cosmological horizon, C + , with respect to positive frequency outgoing modes written in terms of the ordinary retarded null coordinate, u. We trace such modes back to C − along past directed null geodesics through the collapsing body. Some part of the wave will be reflected back without entering it due to the greybody effect. We show that these two kind of traced back modes yield the two temperature spectra and fluxes subject to the aforementioned 'in' vacuum. Since the coordinate u used in the 'out' modes is not well defined on a horizon, estimate on how 'close' we might be to C + is given by estimating backreaction. We argue no other reasonable choice of the 'out' vacuum would give rise to any thermal spectra. Our conclusions remain valid for all non-Nariai class black holes, irrespective of the relative sizes of the two horizons.

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Section: Introductionmentioning

confidence: 99%

Particle creation by de Sitter black holes revisited

Bhattacharya

2018

Phys. Rev. D

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“…To conclude, in this short note, we have studied several aspects of the massive and massless scalar fields in conformally flat space-times, in particular, the FRW geometries. We extended the previous work [3] to include spatially non-flat cases in arbitrary dimensions and with non-minimal couplings. We subsequently discussed the restrictions imposed by the energy conditions on the energy-momentum tensors.…”

Section: Discussionmentioning

confidence: 99%

“…It maps through (9) to a massive scalar field of mass m ′2 = (1 − q)(2 + q) on a deSitter space with Ω ′ (ξ) = ξ −2 where F = ξ q−1 . This result and it's further consequences thereof were recently analyzed in [3].…”

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confidence: 92%

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A note on quantum fields in conformally flat spacetimes

2019

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We develop a technique relating scalar fields with different masses in different conformally flat space-times. We apply this technique to the case of FRW space-times, with k = ±1, 0, and discuss several examples. We also study various energy conditions and discuss how they constrain the space-times related by this technique. We calculate the two point scalar correlator in the radiation dominated universe with a hyperbolic spatial section from the one in the Milne universe using the above mapping. Finally, we consider trace anomaly and renormalized stress tensor for conformally flat space-times, especially Milne and radiation dominated universe (with k = −1) using the transformation.

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“…Second, the high degree of homogeneity and isotropy of the current universe at large scales indicate that our early universe went through an inflationary phase described by a quasi de Sitter spacetime [1]. Being accelerated with expansion and endowed with a cosmological event horizon, the dS offers interesting thermal and other field theoretic properties, we refer our reader to e.g., [2,3,4,5,6] and also references therein.…”

Section: Introductionmentioning

confidence: 99%

Emergent $$\alpha $$-like fermionic vacuum structure and entanglement in the hyperbolic de Sitter spacetime

2019

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We report a non-trivial feature of the vacuum structure of free massive or massless Dirac fields in the hyperbolic de Sitter spacetime. Here we have two causally disconnected regions, say R and L separated by another region, C. We are interested in the field theory in R ∪ L to understand the long range quantum correlations between R and L. There are local modes of the Dirac field having supports individually either in R or L, as well as global modes found via analytically continuing the R modes to L and vice versa. However, we show that unlike the case of a scalar field, the analytic continuation does not preserve the orthogonality of the resulting global modes. Accordingly, we need to orthonormalise them following the Gram-Schmidt prescription, prior to the field quantisation in order to preserve the canonical anti-commutation relations. We observe that this prescription naturally incorporates a spacetime independent continuous parameter, θRL, into the picture. Thus interestingly, we obtain a naturally emerging one-parameter family of α-like de Sitter vacua. The values of θRL yielding the usual thermal spectra of massless created particles are pointed out. Next, using these vacua, we investigate both entanglement and Rényi entropies of either of the regions and demonstrate their dependence on θRL.

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Quantum correlators in Friedmann spacetimes: The omnipresent de Sitter spacetime and the invariant vacuum noise

Cited by 21 publications

References 70 publications

Particle creation by de Sitter black holes revisited

Particle creation by de Sitter black holes revisited

A note on quantum fields in conformally flat spacetimes

Emergent $$\alpha $$-like fermionic vacuum structure and entanglement in the hyperbolic de Sitter spacetime

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