The cosmological constant problem

Weinberg, Steven

doi:10.1103/revmodphys.61.1

Cited by 6,934 publications

(8,010 citation statements)

References 93 publications

Supporting

118

Mentioning

7,815

Contrasting

Unclassified

Order By: Relevance

“…Taking traces of the Einstein terms (2.17), we can construct a one-parameter family of linear combinations of traces in whichR does not appear. 5 One member of this family is precisely the combination that defines the SEC. The 00-component of the SEC involves the combination…”

Section: A Simple Example -The Breathing Mode Casementioning

confidence: 99%

“…Observations of type Ia supernovae (SNIa) [1,2,3], the cosmic microwave background (CMB) [4], and other measurements indicate that the universe is currently undergoing a period of accelerated expansion [5,6,7,8,9]. The inflationary paradigm uses a period of nearly-de Sitter acceleration early in cosmic history to explain the flatness of the present universe, and to predict a nearly scale-invariant spectrum of primordial density perturbations.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Oxidised cosmic acceleration

Wesley

2009

J. Cosmol. Astropart. Phys.

View full text Add to dashboard Cite

Abstract:We give detailed proofs of several new no-go theorems for constructing flat fourdimensional accelerating universes from warped dimensional reduction. These new theorems improve upon previous ones by weakening the energy conditions, by including time-dependent compactifications, and by treating accelerated expansion that is not precisely de Sitter. We show that de Sitter expansion violates the higher-dimensional null energy condition (NEC) if the compactification manifold M is one-dimensional, if its intrinsic Ricci scalarR vanishes everywhere, or ifR and the warp function satisfy a simple limit condition. If expansion is not de Sitter, we establish threshold equation-of-state parameters w below which accelerated expansion must be transient. Below the threshold w there are bounds on the number of e-foldings of expansion. If M is one-dimensional orR everywhere vanishing, exceeding the bound implies the NEC is violated. IfR does not vanish everywhere on M, exceeding the bound implies the strong energy condition (SEC) is violated. Observationally, the w thresholds indicate that experiments with finite resolution in w can cleanly discriminate between different models which satisfy or violate the relevant energy conditions.

show abstract

Section: A Simple Example -The Breathing Mode Casementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Oxidised cosmic acceleration

Wesley

2009

J. Cosmol. Astropart. Phys.

View full text Add to dashboard Cite

show abstract

“…The cosmic acceleration can be caused by a repulsive dark energy component that has a negative equation of state, or, a modification to gravity at cosmological scales, see for example the reviews [2]. The cosmic acceleration and the dark energy associated with it constitute one of the most important and challenging current problems in cosmology and all physics.…”

Section: Introductionmentioning

confidence: 99%

A minimal set of invariants as a systematic approach to higher order gravity models

Ishak¹,

Moldenhauer²

2009

J. Cosmol. Astropart. Phys.

View full text Add to dashboard Cite

Higher-order gravity models have been recently the subject of much attention in the context of cosmic acceleration. These models are derived by adding various curvature invariants to the EinsteinHilbert action. Several studies showed that these models can have late-time self-acceleration and could, in some cases, fit various observational constraints. In view of the infinite spectrum of invariants that could be built from curvature tensors, we propose here a method based on minimal sets of independent invariants as a possible route for a systematic approach to these models. We explore a connection made between theorems on bases in invariants theory in relativity and higher-order cosmological models. A dynamical system analysis is performed and some models with accelerating attractors are discussed. The asymptotic behavior of the models is also studied using analytical calculations.PACS numbers: 98.80.-k, 95.36.+x

show abstract

“…This model suffers from fine tuning and coincidence problems [4]. As an alternative to cosmological constant, the dynamical models have been introduced.…”

Section: Introductionmentioning

confidence: 99%

“…The first candidate which has been introduced for dark energy is a cosmological constant Λ of order (10 −3 eV) 4 , with equation of state parameter ω = p/ρ = −1. This model suffers from fine tuning and coincidence problems [4].…”

Section: Introductionmentioning

confidence: 99%