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The mean gauges in bimetric relativity
Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Stockholms universitet, Naturvetenskapliga fakulteten, Oskar Klein-centrum för kosmopartikelfysik (OKC).
Rekke forfattare: 12019 (engelsk)Inngår i: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 36, nr 23, artikkel-id 235010Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The choice of gauge in numerical relativity is crucial in avoiding coordinate and curvature singularities. In addition, the gauge can affect the well-posedness of the system. In this work, we consider the mean gauges, established with respect to the geometric mean metric in bimetric relativity. We consider three gauge conditions widely used in numerical relativity, and compute them with respect to the geometric mean: The gauge condition and the maximal slicing for the lapse function of , and the -driver gauge condition for the shift vector of . In addition, in the bimetric covariant BSSN formalism, there are other arbitrary choices to be made before evolving the system. We show that it is possible to make them by using the geometric mean metric, which is determined dynamically by the system, rather than using an arbitrary external metric, as in general relativity. These choices represent opportunities to recast the system in a well-posed form.

sted, utgiver, år, opplag, sider
2019. Vol. 36, nr 23, artikkel-id 235010
Emneord [en]
ghost-free bimetric theory, Hassan-Rosen bimetric theory, bimetric relativity, standard gauge, maximal slicing, geometric mean, numerical relativity, Quantum Science & Technology
HSV kategori
Forskningsprogram
teoretisk fysik
Identifikatorer
URN: urn:nbn:se:su:diva-176665DOI: 10.1088/1361-6382/ab4ccfISI: 000494692300001OAI: oai:DiVA.org:su-176665DiVA, id: diva2:1380240
Tilgjengelig fra: 2019-12-18 Laget: 2019-12-18 Sist oppdatert: 2022-03-23bibliografisk kontrollert
Inngår i avhandling
1. Theoretical and numerical bimetric relativity
Åpne denne publikasjonen i ny fane eller vindu >>Theoretical and numerical bimetric relativity
2020 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

General relativity (GR) is the standard physical theory describing gravitational interactions. All astrophysical and cosmological observations are compatible with its predictions, provided that unknown matter and energy components are included. These are called dark matter and dark energy.

In addition, GR describes the nonlinear self-interaction of a massless spin-2 field. In particle physics, there are both massless and massive fields having spin 0, 1 and 1/2. It is then well-justified to ask whether a mathematically consistent nonlinear theory describing a massive spin-2 field exists.

The Hassan–Rosen bimetric relativity (BR) is a mathematically consistent theory describing the nonlinear interaction between a massless and a massive spin-2 field. These fields are described by two metrics, out of which only one can be directly coupled to us and determines the geometry we probe.

Since it includes GR, BR is an extension of it and provides us with new astrophysical and cosmological solutions. These solutions, which may give hints about the nature of dark matter and dark energy, need to be tested against observations in order to support or falsify the theory. This requires predictions for realistic physical systems. One such system is the spherically symmetric gravitational collapse of a dust cloud, and its study is the overarching motivation behind the thesis.

Studying realistic physical systems in BR requires the solving of the nonlinear equations of motion of the theory. This can be done in two ways: (i) looking for methods that simplify the equations in order to solve them exactly, and (ii) solving the equations numerically.

The studies reviewed in the thesis provide results for both alternatives. In the first case, the results concern spacetime symmetries (e.g., spherical symmetry) and how they affect particular solutions in BR, especially those describing gravitational collapse. In the second case, inspired by the success of numerical relativity, the results initiate the field of numerical bimetric relativity. The simulations provide us with the first hints about how gravitational collapse works in BR.

sted, utgiver, år, opplag, sider
Stockholm: Department of Physics, Stockholm University, 2020. s. 187
Emneord
spin-2 fields, extension of general relativity, ghost-free bimetric theory, Hassan–Rosen bimetric relativity, numerical relativity
HSV kategori
Forskningsprogram
teoretisk fysik
Identifikatorer
urn:nbn:se:su:diva-178523 (URN)978-91-7911-004-8 (ISBN)978-91-7911-005-5 (ISBN)
Disputas
2020-03-18, sal FB52, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:15 (engelsk)
Opponent
Veileder
Merknad

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 8: Manuscript.

Tilgjengelig fra: 2020-02-24 Laget: 2020-01-31 Sist oppdatert: 2022-02-26bibliografisk kontrollert

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