Details
| Original language | English |
|---|---|
| Article number | 037 |
| Journal | Journal of Cosmology and Astroparticle Physics |
| Volume | 2019 |
| Issue number | 12 |
| Early online date | 11 Dec 2019 |
| Publication status | Published - 2019 |
| Externally published | Yes |
Abstract
We discuss mimetic gravity theories with direct couplings between the curvature and higher derivatives of the scalar field, up to the quintic order, which were proposed to solve the instability problem for linear perturbations around the FLRW background for this kind of models. Restricting to homogeneous scalar field configurations in the action, we derive degeneracy conditions to obtain an effective field theory with three degrees of freedom. However, performing the Hamiltonian analysis for a generic scalar field we show that there are in general four or more degrees of freedom. The discrepancy is resolved because, for a homogeneous scalar field profile, iφ≈ 0, the Dirac matrix becomes singular, resulting in further constraints, which reduces the number of degrees of freedom to three. Similarly, in linear perturbation theory the additional scalar degree of freedom can only be seen by considering a non-homogeneous background profile of the scalar field. Therefore, restricting to homogeneous scalar fields these kinds of models provide viable explicitly Lorentz violating effective field theories of mimetic gravity.
Keywords
- dark energy theory, Modified gravity
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Astronomy and Astrophysics
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In: Journal of Cosmology and Astroparticle Physics, Vol. 2019, No. 12, 037, 2019.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Towards a viable effective field theory of mimetic gravity
AU - Ganz, Alexander
AU - Bartolo, Nicola
AU - Matarrese, Sabino
N1 - Acknowledgments We would like to thank G. Tasinato, P. Karmakar and especially D. Sorokin for useful discus- sions and comments on a preliminary version of this paper. This work is partially supported by ASI Grant No. 2016-24-H.0. Part of the computations are done using Mathematica,1 with the algebra package xAct.2
PY - 2019
Y1 - 2019
N2 - We discuss mimetic gravity theories with direct couplings between the curvature and higher derivatives of the scalar field, up to the quintic order, which were proposed to solve the instability problem for linear perturbations around the FLRW background for this kind of models. Restricting to homogeneous scalar field configurations in the action, we derive degeneracy conditions to obtain an effective field theory with three degrees of freedom. However, performing the Hamiltonian analysis for a generic scalar field we show that there are in general four or more degrees of freedom. The discrepancy is resolved because, for a homogeneous scalar field profile, iφ≈ 0, the Dirac matrix becomes singular, resulting in further constraints, which reduces the number of degrees of freedom to three. Similarly, in linear perturbation theory the additional scalar degree of freedom can only be seen by considering a non-homogeneous background profile of the scalar field. Therefore, restricting to homogeneous scalar fields these kinds of models provide viable explicitly Lorentz violating effective field theories of mimetic gravity.
AB - We discuss mimetic gravity theories with direct couplings between the curvature and higher derivatives of the scalar field, up to the quintic order, which were proposed to solve the instability problem for linear perturbations around the FLRW background for this kind of models. Restricting to homogeneous scalar field configurations in the action, we derive degeneracy conditions to obtain an effective field theory with three degrees of freedom. However, performing the Hamiltonian analysis for a generic scalar field we show that there are in general four or more degrees of freedom. The discrepancy is resolved because, for a homogeneous scalar field profile, iφ≈ 0, the Dirac matrix becomes singular, resulting in further constraints, which reduces the number of degrees of freedom to three. Similarly, in linear perturbation theory the additional scalar degree of freedom can only be seen by considering a non-homogeneous background profile of the scalar field. Therefore, restricting to homogeneous scalar fields these kinds of models provide viable explicitly Lorentz violating effective field theories of mimetic gravity.
KW - dark energy theory
KW - Modified gravity
UR - http://www.scopus.com/inward/record.url?scp=85080920336&partnerID=8YFLogxK
U2 - 10.48550/arXiv.1907.10301
DO - 10.48550/arXiv.1907.10301
M3 - Article
AN - SCOPUS:85080920336
VL - 2019
JO - Journal of Cosmology and Astroparticle Physics
JF - Journal of Cosmology and Astroparticle Physics
SN - 1475-7516
IS - 12
M1 - 037
ER -