A global picture of quantum de Sitter space

Giddings, Steven B.; Marolf, Donald

doi:10.1103/physrevd.76.064023

Cited by 49 publications

(84 citation statements)

References 71 publications

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“…Here there is a space of states that we expect to be well-described in perturbative gravity. These are the states satisfying the de Sitter locality bound [8]. This is an analog of the bound (4.2), and takes the form…”

Section: Aspects Of Nonlocal Mechanics For Cosmologymentioning

confidence: 97%

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Universal quantum mechanics

Giddings

2008

Phys. Rev. D

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If gravity respects quantum mechanics, it is important to identify the essential postulates of a quantum framework capable of incorporating gravitational phenomena. Such a construct likely requires elimination or modification of some of the "standard" postulates of quantum mechanics, in particular those involving time and measurement. This paper proposes a framework that appears sufficiently general to incorporate some expected features of quantum gravity. These include the statement that space and time may only emerge approximately and relationally. One perspective on such a framework is as a sort of generalization of the S-matrix approach to dynamics. Within this framework, more dynamical structure is required to fully specify a theory; this structure is expected to lack some of the elements of local quantum field theory. Some aspects of this structure are discussed, both in the context of scattering of perturbations about a flat background, and in the context of cosmology. *

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Section: Aspects Of Nonlocal Mechanics For Cosmologymentioning

confidence: 97%

“…As an example consider de Sitter space, which is discussed from a related viewpoint in [8]. Here there is a space of states that we expect to be well-described in perturbative gravity.…”

Section: Aspects Of Nonlocal Mechanics For Cosmologymentioning

confidence: 99%

Universal quantum mechanics

Giddings

2008

Phys. Rev. D

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“…It has been proposed that local observables are approximately recovered from certain relational protolocal observables; initial exploration of them in effective field theory is described in [43,69,70]. However, as yet no sharp criterion for locality can be formulated in terms of these observables, and indeed it has been argued [25,43] that there are fundamental obstacles to such precise locality.…”

Section: Locality Vs Nonpolynomialitymentioning

confidence: 99%

The gravitationalSmatrix

Giddings

Porto

2010

Phys. Rev. D

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We investigate the hypothesized existence of an S matrix for gravity and some of its expected general properties. We first discuss basic questions regarding the existence of such a matrix, including those of infrared divergences and description of asymptotic states. Distinct scattering behavior occurs in the Born, eikonal, and strong gravity regimes, and we describe aspects of both the partial wave and momentum space amplitudes, and their analytic properties, from these regimes. Classically the strong gravity region would be dominated by the formation of black holes, and we assume its unitary quantum dynamics is described by corresponding resonances. Masslessness limits some powerful methods and results that apply to massive theories, though a continuation path implying crossing symmetry plausibly still exists. Physical properties of gravity suggest nonpolynomial amplitudes, although crossing and causality constrain (with modest assumptions) this nonpolynomial behavior, particularly requiring a polynomial bound in complex s at fixed physical momentum transfer. We explore the hypothesis that such behavior corresponds to a nonlocality intrinsic to gravity, but consistent with unitarity, analyticity, crossing, and causality.

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“…Now we need a suitable solution to the measure problem to cure the putative catastrophe of Boltzmann brains. There are by now quite a number of other proposed solutions to the Boltzmann brain paradox, 48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74 but all of them, including my own suggestions, seem to me rather unnatural. The main problem seems to arise from the rather plausible deduction that there should be an infinite number of Boltzmann brains that arise in any spacetime that lasts forever, especially if it also expands by an unbounded amount.…”

Section: Introductionmentioning

confidence: 99%

Cosmological Measures With Volume Averaging

Page

2011

Int. J. Mod. Phys. Conf. Ser.

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It has been common for cosmologists to advocate volume weighting for the cosmological measure problem, weighting spatial hypersurfaces by their volume. However, this often leads to the Boltzmann brain problem, that almost all observations would be by momentary Boltzmann brains that arise very briefly as quantum fluctuations in the late universe when it has expanded to a huge size, so that our observations (too ordered for Boltzmann brains) would be highly atypical and unlikely. Here it is suggested that volume weighting may be a mistake. Volume averaging is advocated as an alternative. One consequence may be a loss of the argument that eternal inflation gives a nonzero probability that our universe now has infinite volume.

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A global picture of quantum de Sitter space

Cited by 49 publications

References 71 publications

Universal quantum mechanics

Universal quantum mechanics

The gravitationalSmatrix

Cosmological Measures With Volume Averaging

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