Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Cosmological solutions in bimetric gravity and their observational tests
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Show others and affiliations
2012 (English)In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 3, 042- p.Article in journal (Refereed) Published
Abstract [en]

We obtain the general cosmological evolution equations for a classically consistent theory of bimetric gravity. Their analytic solutions are demonstrated to generically allow for a cosmic evolution starting out from a matter dominated FLRW universe and relaxing towards a de Sitter (anti-de Sitter) phase at late cosmic time. In particular, we examine a subclass of models which contain solutions that are able to reproduce the expansion history of the cosmic concordance model inspite of the nonlinear couplings of the two metrics. This is demonstrated explicitly by fitting these models to observational data from Type Ia supernovae, Cosmic Microwave Background and Baryon Acoustic Oscillations. In the appendix we comment on the relation to massive gravity.

Place, publisher, year, edition, pages
2012. no 3, 042- p.
Keyword [en]
modified gravity, dark energy theory
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Theoretical Physics
Identifiers
URN: urn:nbn:se:su:diva-83245DOI: 10.1088/1475-7516/2012/03/042ISI: 000302949600042OAI: oai:DiVA.org:su-83245DiVA: diva2:574777
Available from: 2012-12-06 Created: 2012-12-06 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Unravelling Consistent Spin-2 Interactions
Open this publication in new window or tab >>Unravelling Consistent Spin-2 Interactions
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Recently, a unique formulation of a classically consistent theory of massive spin-2 fields has emerged. In this thesis I address a few of the primary questions that arise once such a theory is available.

I will discuss cosmological solutions in a bimetric setup and show that, as far as the background evolution is concerned, a theory of interacting spin-2 fields remain a viable option to the mainstream ΛCDM concordance model. In general, the bimetric solutions are quite different from general relativistic solutions and hence in many situations will not be supported by observations. I highlight a particularly useful class of bimetric solutions which mimic general relativity exactly at the background level. This class of solutions is very special since it both uniquely provide the maximally symmetric vacuum solutions in the absence of matter sources as well as uniquely provide a massive Fierz-Pauli wave equation for perturbations of these backgrounds. This allow us a clear interpretation of the spectrum of perturbations in terms of mass eigenstates. I provide a nonlinear extension of these mass eigenstates into nonlinear fields which are not true mass eigenstates but still provide useful input into the theoretical understanding of the theory. These nonlinear extensions are particularly interesting both with respect to parameterizing generic deviations of the bimetric solutions to general relativistic solutions, as well as providing further insight into some unresolved questions related to ``massive gravity" in maximally symmetric backgrounds, such as the illusive nature of the Higuchi bound and its accompanying linear on-shell gauge invariance.

The special structure of the consistent interacting theory provides the basic tool to start to unravel some of the mysteries connected with spin-2 fields, with hope to reinvestigate many fundamental open questions explicitly related to the gravitational sector of field theory.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2012. 135 p.
Keyword
Modified Gravity, Massive Spin-2, Spin-2 Interactions
National Category
Physical Sciences
Research subject
Theoretical Physics
Identifiers
urn:nbn:se:su:diva-83258 (URN)978-91-7447-618-7 (ISBN)
Public defence
2013-01-28, FA32, AlbaNova University Center, Roslagstullsbacken 21, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Submitted. Paper 6: Submitted.

 

Available from: 2013-01-07 Created: 2012-12-06 Last updated: 2012-12-14Bibliographically approved
2. Consistent Nonlinear Interactions for the Graviton
Open this publication in new window or tab >>Consistent Nonlinear Interactions for the Graviton
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis investigates various aspects of massive gravity and bimetric gravity which be- long to a certain class of modifications of general relativity. It provides an introduction to linear massive gravity in flat backgrounds, before reviewing the construction of consistent nonlinear massive gravity that avoids the Boulware-Deser ghost instability. We discuss the structure of the ghost-free action and summarize the consistency proofs for massive gravity in arbitrary backgrounds, using two different formulations. Thereafter we reca- pitulate the generalization of massive gravity to consistent bimetric models of gravity, in which we then solve the equations of motion with a homogeneous, isotropic ansatz and discuss implications for cosmology.

Place, publisher, year, edition, pages
Department of Physis, Stockholm University, 2012. 63 p.
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-77173 (URN)
Available from: 2013-01-30 Created: 2012-06-01 Last updated: 2013-01-30Bibliographically approved
3. Classically Consistent Theories of Interacting Spin-2 Fields
Open this publication in new window or tab >>Classically Consistent Theories of Interacting Spin-2 Fields
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This doctoral thesis comprises a study of recently developed nonlinear theories for massive spin-2 fields that go by the names of Massive Gravity and Bimetric Theory. As we demonstrate in a Hamiltonian analysis, the construction of these theories avoids the notorious Boulware-Deser ghost instability that generically plagues nonlinear spin-2 interactions and renders their description inconsistent. We explore the mass spectrum of ghost-free Bimetric Theory and reformulate its action in terms of nonlinear mass eigenstates. A generalized version of the theory with multiple vielbein interactions is reviewed and then reexpressed in terms of metrics. Homogeneous and isotropic solutions to the equations of motion in Bimetric Theory are derived and discussed in the context of cosmology. We furthermore single out particular values for the parameters in the bimetric interaction potential for which the theory could potentially contain an additional gauge redundancy. This establishes a unique candidate for a nonlinear theory of a partially massless spin-2 field. Finally, we reveal a close connection of Bimetric Theory to a certain class of higher-curvature theories for gravity and offer a solution to their ghost problems. In particular we find that, in four space-time dimensions, the bimetric candidate for nonlinear partial masslessness is closely related to Conformal Gravity.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2013. 134 p.
National Category
Physical Sciences
Research subject
Theoretical Physics
Identifiers
urn:nbn:se:su:diva-96167 (URN)978-91-7447-791-7 (ISBN)
Public defence
2013-12-12, sal FA32, AlbaNova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:30 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 6: Submitted. Paper 8: Manuscript.

Available from: 2013-11-20 Created: 2013-11-12 Last updated: 2013-11-12Bibliographically approved
4. Cosmic tests of massive gravity
Open this publication in new window or tab >>Cosmic tests of massive gravity
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Massive gravity is an extension of general relativity where the graviton, which mediates gravitational interactions, has a non-vanishing mass. The first steps towards formulating a theory of massive gravity were made by Fierz and Pauli in 1939, but it took another 70 years until a consistent theory of massive gravity was written down. This thesis investigates the phenomenological implications of this theory, when applied to cosmology. In particular, we look at cosmic expansion histories, structure formation, integrated Sachs-Wolfe effect and weak lensing, and put constraints on the allowed parameter range of the theory. This is done by using data from supernovae, the cosmic microwave background, baryonic acoustic oscillations, galaxy and quasar maps and galactic lensing.

The theory is shown to yield both cosmic expansion histories, galactic lensing and an integrated Sachs-Wolfe effect consistent with observations. For the structure formation, however, we show that for certain parameters of the theory there exists a tension between consistency relations for the background and stability properties of the perturbations. We also show that a background expansion equivalent to that of general relativity does not necessarily mean that the perturbations have to evolve in the same way.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2015. 104 p.
Keyword
Modified gravity, massive gravity, cosmology, dark energy, dark matter
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-113076 (URN)978-91-7649-049-5 (ISBN)
Public defence
2015-02-20, sal FD5, AlbaNova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Manuscript. Paper 6: Manuscript.

Available from: 2015-01-29 Created: 2015-01-22 Last updated: 2015-08-24Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full texthttp://arxiv.org/abs/1111.1655

Search in DiVA

By author/editor
von Strauss, MikaelSchmidt-May, AngnisEnander, JonasMörtsell, EdvardHassan, S. Fawad
By organisation
Department of PhysicsThe Oskar Klein Centre for Cosmo Particle Physics (OKC)
In the same journal
Journal of Cosmology and Astroparticle Physics
Astronomy, Astrophysics and Cosmology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 82 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf