Cosmology and Local Physics

Ellis, George

doi:10.1142/s0217751x02011588

Cited by 30 publications

(41 citation statements)

References 43 publications

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“…As regards the arrow of time problem [16,85], if the EBU view is correct, the Wheeler-Feynman prescription for introducing the arrow of time by integration over the far future [84], and associated views comparing the far future with the distant past [62,31,23], are invalid approaches to solving the arrow of time problem, for it is not possible to do integrations over future time domains if they do not yet exist. Indeed the use of half-advanced and half-retarded Feynman propagators in quantum field theory then becomes a calculational tool representing a local symmetry of the underlying physics that does not reflect the nature of emergent physical reality, in which that symmetry is broken.…”

Section: The Arrow Of Timementioning

confidence: 99%

Spacetime and the Passage of Time

Ellis

Goswami

2014

Springer Handbook of Spacetime

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This paper examines the various arguments that have been put forward suggesting either that time does not exist, or that it exists but it's flow is not real. I argue that (i) time both exists and flows; (ii) an Evolving Block Universe ('EBU') model of spacetime adequately captures this feature, emphasizing the key differences between the past, present, and future; (iii) the associated surfaces of constant time are uniquely geometrically and physically determined in any realistic spacetime model based in General Relativity Theory; (iv) such a model is needed in order to capture the essential aspects of what is happening in circumstances where initial data does not uniquely determine the evolution of spacetime structure because quantum uncertainty plays a key role in that development. Assuming that the functioning of the mind is based in the physical brain, evidence from the way that the mind apprehends the flow of time prefers this evolving time model over those where there is no flow of time. Space time and the Block UniverseIn this section I briefly summarize the usual representation in relativity theory of space-time as an unchanging block universe, and the associated view that the change of time is an illusion.The nature of spacetime in both special and general relativity has lead some to a view that the passage of time is an illusion [72,12,39,40]. Given data at an arbitrary time, it is claimed that everything occurring at any later or earlier time can be uniquely determined from that data, evolved according to deterministic local physical laws (this is formalized in standard existence and uniqueness theorems [49]). Consequently, nothing can be special about any particular moment; there is no special "now" which can be called the present. Past, present and future are equal to each other, for there is no surface which can uniquely be called the present.Such a view can be formalized in the idea of a Block Universe [59,70,17]: space and time are represented as merged into an unchanging spacetime entity, with no particular space sections identified as the present and no evolution of spacetime taking place. The universe just is: a fixed spacetime block, representing all events that have happened and that will happen. This representation implicitly embodies the idea that time is an illusion: time does not "roll on" in this picture. All past and future times are equally present, and the present "now" is just one of an infinite number. Price [67] and Barbour [7] in particular advocate such a position. Underlying this, as emphasized by Barbour, is the idea that time-reversible Hamiltonian dynamics provides the foundation for physical theory in general and gravitation in particular. Occasionally cosmology or astrophysics takes into account time-irreversible physics, for example nucleosynthesis in the early universe or the late phases of gravitational collapse, but the notion of the present as a special time remains absent.The problem with this view is that it is profound contradiction with our experiences in e...

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Section: The Arrow Of Timementioning

confidence: 99%

Spacetime and the Passage of Time

Ellis

Goswami

2014

Springer Handbook of Spacetime

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“…[3] for more historical material). It is related to the general problem of assessing the influence of global physics on local physics [4,5] and to the Machian local inertia (see, e.g., Refs. [6,7]).…”

Section: Introductionmentioning

confidence: 99%

Separating expansion and collapse in general fluid models with heat flux

et al. 2013

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In this paper we consider spherically symmetric general fluids with heat flux, motivated by causal thermodynamics, and give the appropriate set of conditions that define separating shells defining the divide between expansion and collapse. To do so we add the new requirement that heat flux and its evolution vanish at the separating surface. We extend previous works with a fully nonlinear analysis in the 1+3 splitting, and present gauge-invariant results. The definition of the separating surface is inspired by the conservation of the Misner-Sharp mass, and is obtained by generalizing the Tolman-Oppenheimer-Volkoff equilibrium and turnaround conditions. We emphasize the nonlocal character of these conditions as found in previous works and discuss connections to the phenomena of spacetime cracking and thermal peeling.Comment: 5pp. Updated to match published versio

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“…The possibility of determining these tight limits arises precisely because global cosmological variables have significant effects on the local physical processes of structure formation. Just like nucleosynthesis, this is a top-down effect from global variables to local physical effects [120], because global parameters (density ρ, expansion rate θ ) enter as parameters in the differential equations (32), (33) above for the growth of perturbations. That is why the growth is power law [1,2] and not exponential [37], as pointed out by Lifshitz [1,2].…”

Section: Cosmography: Cosmological Parametersmentioning

confidence: 99%

Editorial note to: E. Lifshitz, On the gravitational stability of the expanding universe

Ellis

2017

Gen Relativ Gravit

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The major stepsThe dynamics of standard cosmology has two parts: firstly, the dynamics of the background spatially homogeneous and isotropic Friedmann-Lemaître-Robertson-Walker ('FLRW') model; and secondly, the dynamics of inhomogeneous perturbations about that model that lead to structure formation in the expanding universe. Understanding each has taken place in two phases: before inflation theory, and after inflation theory. The 1946 Lifshitz paper reprinted here "On the gravitational stability of the expanding universe" [1,2] was the pioneer paper investigating the development of generic linearised inhomogeneities, and provided the basis for all further developments in this regard.Cosmological models must of course be related to astronomical observations. One can observationally directly test the geometry of the background model, and can observe the structures that form in this model. However additionally, observational studies of large scale structures on the one hand, and of Cosmic Microwave Background Radiation ('CMB') anisotropies on the other, provide strong observational constraints on the background model [3,4].The republication of the original paper can be found in this issue following the editorial note and online via doi:10.1007/s10714-016-2165-8.

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Cosmology and Local Physics

Cited by 30 publications

References 43 publications

Spacetime and the Passage of Time

Spacetime and the Passage of Time

Separating expansion and collapse in general fluid models with heat flux

Editorial note to: E. Lifshitz, On the gravitational stability of the expanding universe

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