Ghost‐Free Completion of An Effective Matter Coupling in Bimetric Theory

Lüben, Marvin; Schmidt-May, Angnis

doi:10.1002/prop.201800031

Cited by 11 publications

(6 citation statements)

References 60 publications

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“…1 To which metric the matter fields should couple led to a lot of discussion in the literature [29][30][31][32][33][34]. The result is that there are only two options which do not reintroduce the Boulwere-Deser ghost at unacceptable low energy scales.…”

Section: 6)mentioning

confidence: 99%

Physical parameter space of bimetric theory and SN1a constraints

Lüben,

Schmidt-May,

Weller

2020

Preprint

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Bimetric theory describes a massless and a massive spin-2 field with fully non-linear (self-)interactions. It has a rich phenomenology and has been successfully tested with several data sets. However, the observational constraints have not been combined in a consistent framework, yet. We propose a parametrization of bimetric solutions in terms of the effective cosmological constant Λ and the mass m FP of the spin-2 field as well as its coupling strength to ordinary matter ᾱ. This simplifies choosing priors in statistical analysis and allows to directly constrain these parameters with observational data not only from local systems but also from cosmology. By identifying the physical vacuum of bimetric theory these parameters are uniquely determined. We work out the new parametrization for various submodels and present the implied consistency constraints on the physical parameter space. As an application we derive observational constraints from SN1a on the physical parameters. We find that a large portion of the physical parameter space is in perfect agreement with current supernova data including self-accelerating models with a heavy spin-2 field.

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Section: 6)mentioning

confidence: 99%

Physical parameter space of bimetric theory and SN1a constraints

Lüben,

Schmidt-May,

Weller

2020

Preprint

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“…However, incorporating the non-linear effects keep their mass above Mp [25]. Moreover, for the bimetric extension of the composite coupling, a tri-metric theory can provide a ghost-free completion [39]. 6 Other contractions with higher powers of ∇φ do not produce any more independent terms.…”

Section: A Formalismmentioning

confidence: 99%

“…To summarise, combining the conditions for consistent background (33), avoiding ghost modes in the free theory (39), removing the Λ 5 cubic interactions (50) and Λ 4 quartic interactions (58), we obtain the following conditions:…”

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confidence: 99%

Generalizing the matter coupling in massive gravity: A search for new interactions

Gümrükçüoğlu¹,

Koyama²

2019

Phys. Rev. D

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Massive gravity theory introduced by de Rham, Gabadadze, Tolley (dRGT) is restricted by several uniqueness theorems that protect the form of the potential and kinetic terms, as well as the matter coupling. These restrictions arise from the requirement that the degrees of freedom match the expectation from Poincaré representations of a spin-2 field. Any modification beyond the dRGT form is known to invalidate a constraint that the theory enjoys and revive a dangerous sixth mode. One loophole is to exploit the effective nature of the theory by pushing the sixth mode beyond the strong coupling scale without completely removing it. In this paper, we search for modifications to dRGT action by coupling the matter sector to an arbitrary metric constructed out of the already existing degrees of freedom in the dRGT action. We formulate the conditions that such an extension should satisfy in order to prevent the sixth mode from contaminating the effective theory. Our approach provides a new perspective for the "composite coupling" which emerges as the unique extension up to four-point interactions. * Electronic address: emir.gumrukcuoglu@port.ac.uk † Electronic address: kazuya.koyama@port.ac.uk 1 In our formulation, we assume a universal matter coupling. In the case where weak equivalence principle is broken, different matter sectors can flow on different geometries. Justification for a restricted version of this scenario is presented in Section VI. 2 In Bekenstein's nomenclature, g is the gravitational metric whileg is the physical metric [1]. Since matter follows the geodesics ofg, the physical metric is uniquely defined. However, the interpretation of the gravitational metric is more ambiguous in modern modified gravity theories, where it is not always possible to define a field variable to reduce the vacuum action to general relativity and minimally coupled extra fields. 3 Although representations related by a change of variable are classically equivalent (see e.g. [2-4]), subtle differences arise in their interpretations [5], while quantum anomalies may invalidate the physical equivalence [6].

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“…To which metric the matter fields should couple led to a lot of discussion in the literature[29][30][31][32][33][34]. The result is that there are only two options which do not reintroduce the Boulwere-Deser ghost at unacceptable low energy scales.…”

mentioning

confidence: 99%

“…Alternatively, matter can minimally couple to an effective metric composed out of the two metric tensors[29]. This matter coupling lowers the cutoff of the theory but can be embedded into a trimetric setup[31]. Phenomenological aspects were discussed in e.g.…”

mentioning

confidence: 99%

Physical parameter space of bimetric theory and SN1a constraints

Lüben

Schmidt-May

Weller

2020

J. Cosmol. Astropart. Phys.

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Bimetric theory describes a massless and a massive spin-2 field with fully non-linear (self-)interactions. It has a rich phenomenology and has been successfully tested with several data sets. However, the observational constraints have not been combined in a consistent framework, yet. We propose a parametrization of bimetric solutions in terms of the effective cosmological constant Λ and the mass mFP of the spin-2 field as well as its coupling strength to ordinary matter ᾱ. This simplifies choosing priors in statistical analysis and allows to directly constrain these parameters with observational data not only from local systems but also from cosmology. By identifying the physical vacuum of bimetric theory these parameters are uniquely determined. We work out the new parametrization for various submodels and present the implied consistency constraints on the physical parameter space. As an application we derive observational constraints from SN1a on the physical parameters. We find that a large portion of the physical parameter space is in perfect agreement with current supernova data including self-accelerating models with a heavy spin-2 field.

show abstract

Ghost‐Free Completion of An Effective Matter Coupling in Bimetric Theory

Cited by 11 publications

References 60 publications

Physical parameter space of bimetric theory and SN1a constraints

Physical parameter space of bimetric theory and SN1a constraints

Generalizing the matter coupling in massive gravity: A search for new interactions

Physical parameter space of bimetric theory and SN1a constraints

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