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Emergent perspective of gravity and dark energy

Emergent perspective of gravity and dark energy
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摘要 There is sufficient amount of internal evidence in the nature of gravitational theories to indicate that gravity is an emergent phenomenon like, e.g, elasticity. Such an emergent nature is most apparent in the structure of gravitational dynamics. It is, however, possible to go beyond the field equations and study the space itseff as emer- gent in a well-defined manner in (and possibly only in) the context of cosmology. In the first part of this review, I describe various pieces of evidence which show that gravitational field equations are emergent. In the second part, I describe a novel way of studying cosmology in which I interpret the expansion of the universe as equivalent to the emergence of space itself. In such an approach, the dynamics evolves towards a state of holographic equipartition, characterized by an equality in the number of bulk and surface degrees of freedom in a region bounded by the Hubble radius. This prin- ciple correctly reproduces the standard evolution of a Friedmann universe. Further, (a) it demands the existence of an early inflationary phase as well as late time accelera- tion for its successful implementation and (b) allows us to link the value of late time cosmological constant to the e-folding factor during inflation. There is sufficient amount of internal evidence in the nature of gravitational theories to indicate that gravity is an emergent phenomenon like, e.g, elasticity. Such an emergent nature is most apparent in the structure of gravitational dynamics. It is, however, possible to go beyond the field equations and study the space itseff as emer- gent in a well-defined manner in (and possibly only in) the context of cosmology. In the first part of this review, I describe various pieces of evidence which show that gravitational field equations are emergent. In the second part, I describe a novel way of studying cosmology in which I interpret the expansion of the universe as equivalent to the emergence of space itself. In such an approach, the dynamics evolves towards a state of holographic equipartition, characterized by an equality in the number of bulk and surface degrees of freedom in a region bounded by the Hubble radius. This prin- ciple correctly reproduces the standard evolution of a Friedmann universe. Further, (a) it demands the existence of an early inflationary phase as well as late time accelera- tion for its successful implementation and (b) allows us to link the value of late time cosmological constant to the e-folding factor during inflation.
作者 T.Padmanabhan
机构地区 IUCAA
出处 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2012年第8期891-916,共26页 天文和天体物理学研究(英文版)
基金 supported by a J.C. Bose research grant of DST, India
关键词 cosmology: theory -- cosmology: cosmological parameters -- emergentgravity -- holographic principle cosmology: theory -- cosmology: cosmological parameters -- emergentgravity -- holographic principle
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