General Relativity and Cosmology: Unsolved Questions and Future Directions

Debono, Ivan; Smoot, George F.

doi:10.3390/universe2040023

Cited by 183 publications

(153 citation statements)

References 552 publications

(541 reference statements)

Supporting

Mentioning

128

Contrasting

Order By: Relevance

“…Often the field equation is justified partly with the observation that it is the simplest possible or even only one, as for example: "Under certain assumptions about the structure of physical theories, and of the properties of the gravitational field, General Relativity is the only theory that describes gravity. Alternative theories introduce additional interactions and fields [8]." This claim originated with Einstein and continues in the modern texts cited.…”

Section: Introductionmentioning

confidence: 95%

A family of metric gravities

Shuler

2018

Eur. Phys. J. Plus

View full text Add to dashboard Cite

Abstract. The goal of this paper is to take a completely fresh approach to metric gravity, in which the metric principle is strictly adhered to but its properties in local space-time are derived from conservation principles, not inferred from a global field equation. The global field strength variation then gains some flexibility, but only in the regime of very strong fields (2nd-order terms) whose measurement is now being contemplated. So doing provides a family of similar gravities, differing only in strong fields, which could be developed into meaningful verification targets for strong fields after the manner in which far-field variations were used in the 20th century. General Relativity (GR) is shown to be a member of the family and this is demonstrated by deriving the Schwarzschild metric exactly from a suitable field strength assumption. The method of doing so is interesting in itself because it involves only one differential equation rather than the usual four. Exact static symmetric field solutions are also given for one pedagogical alternative based on potential, and one theoretical alternative based on inertia, and the prospects of experimentally differentiating these are analyzed. Whether the method overturns the conventional wisdom that GR is the only metric theory of gravity and that alternatives must introduce additional interactions and fields is somewhat semantical, depending on whether one views the field strength assumption as a field and whether the assumption that produces GR is considered unique in some way. It is of course possible to have other fields, and the local space-time principle can be applied to field gravities which usually are weak-field approximations having only time dilation, giving them the spatial factor and promoting them to full metric theories. Though usually pedagogical, some of them are interesting from a quantum gravity perspective. Cases are noted where mass measurement errors, or distributions of dark matter, can cause one theory to mimic another implying that such estimates or distributions should be first obtained from weakfield measurements before being used to discriminate verification candidates. By this method theorists gain insight into the local constraints on space-time, and GR verification gains strong-field comparative objectives.

show abstract

Section: Introductionmentioning

confidence: 95%

A family of metric gravities

Shuler

2018

Eur. Phys. J. Plus

View full text Add to dashboard Cite

show abstract

“…The PPN parameter γ has been constrained to |γ − 1| ≤ 2.3 × 10 −5 using the Cassini spacecraft [57], β to |β − 1| ≤ 3 × 10 −5 thanks to planetary ephemeris [58] and α 1 and α 2 to |α 1 | ≤ 6 × 10 −6 and |α 2 | ≤ 3.5 × 10 −5 thanks to refined values of Solar System planetary precessions [59]. Many other constraints have been put on PPN parameters, and a summary of these constraints can be found in, e.g., [11,60].…”

Section: Ppn Metric Of An Isolated Axisymmetric Rotating Bodymentioning

confidence: 99%

Theoretical Tools for Relativistic Gravimetry, Gradiometry and Chronometric Geodesy and Application to a Parameterized Post-Newtonian Metric

Delva

Geršl

2017

Universe

View full text Add to dashboard Cite

show abstract

“…Analysis of the data resulted in a relative error of geodetic precessing rate less than 0.4%. With the cosmologically best-fit value 1 It measured also the gravitomagnetic spin precession induced in GR by the Earth's rotation; see, e.g., [58]. (21) and the mass of Earth (G M ⊕ 22487.9 eV −1 , with the gravitational constant G recovered), the relative modifications of our models are | ω I /ω GR | ≤ 3.005 × 10 −31 and ω II /ω GR = 2.152B × 10 −11 .…”

Section: Geodetic Effectmentioning

confidence: 99%

“…General relativity (GR), whose centenary was recently celebrated [1,2], uses the metric tensor as the fundamental dynamical variable, and chooses the torsionless Levi-Civitá connection to describe the gravitation field. In the teleparallel equivalent of general relativity (TEGR) [3][4][5], the curvatureless Weizenböck connection is chosen instead, and the tetrad field plays the role of fundamental variable.…”

Section: Introductionmentioning

confidence: 99%

Solar system tests for realistic f(T) models with non-minimal torsion–matter coupling

Lin

Zhai

2017

Eur. Phys. J. C

View full text Add to dashboard Cite

In the previous paper, we have constructed two f (T ) models with non-minimal torsion-matter coupling extension, which are successful in describing the evolution history of the Universe including the radiation-dominated era, the matter-dominated era, and the present accelerating expansion. Meantime, the significant advantage of these models is that they could avoid the cosmological constant problem of CDM. However, the non-minimal coupling between matter and torsion will affect the tests of the Solar system. In this paper, we study the effects of the Solar system in these models, including the gravitation redshift, geodetic effect and perihelion precession. We find that Model I can pass all three of the Solar system tests. For Model II, the parameter is constrained by the uncertainties of the planets' estimated perihelion precessions.

show abstract

General Relativity and Cosmology: Unsolved Questions and Future Directions

Cited by 183 publications

References 552 publications

A family of metric gravities

A family of metric gravities

Theoretical Tools for Relativistic Gravimetry, Gradiometry and Chronometric Geodesy and Application to a Parameterized Post-Newtonian Metric

Solar system tests for realistic f(T) models with non-minimal torsion–matter coupling

Contact Info

Product

Resources

About