Phenomenology in type-I minimally modified gravity

Aoki, Katsuki; Felice, Antonio De; Lin, C.; Mukohyama, Shinji; Oliosi, Michele

doi:10.1088/1475-7516/2019/01/017

Cited by 57 publications

(81 citation statements)

References 24 publications

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“…In the presence of matter, these equations have to be supplemented with source terms. However, describing explicitly how matter is coupled to the (modified) gravitational field is subtle and has been analyzed in great details in [25,27]. A "naive" minimal coupling 3 of the matter fields, for 3 If the matter is minimally coupled (with no derivative couplings) and is described by a action SM associated to an energy-momentum tensor T µν , then the equation for hij (3.29) is unchanged, the deformed Hamiltonian constraint becomes f (Hgr) + 16πGN N 2 T 00 ≈ 0 , (3.32) and the equation for the momenta πij contains a source terṁ…”

Section: )mentioning

confidence: 99%

Minimally modified gravity: a Hamiltonian construction

Mukohyama

Noui

2019

J. Cosmol. Astropart. Phys.

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Minimally modified gravity theories are modifications of general relativity with two local gravitational degrees of freedom in four dimensions. Their construction relies on the breaking of 4D diffeomorphism invariance keeping however the symmetry under 3D diffeomorphisms. Here, we construct these theories from a Hamiltonian point of view. We start with the phase space of general relativity in the ADM formalism. Then, we find the conditions that the Hamiltonian must satisfy for the theory to propagate (up to) two gravitational degrees of freedom with the assumptions that the lapse and the shift are not dynamical, and the theory remains invariant under 3D diffeomorphisms. This construction enables us to recover the well-known "cuscuton" class of scalar-tensor theories in the unitary gauge. We also exhibit a new class of interesting theories, that we dubb f (H) theories, where the usual Hamiltonian constraint H of general relativity is replaced by f (H) where f is an arbitrary function.

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Section: )mentioning

confidence: 99%

Minimally modified gravity: a Hamiltonian construction

Mukohyama

Noui

2019

J. Cosmol. Astropart. Phys.

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“…This issue is entangled with the nature of the identically conserved pieces that can be added to the stress-energy tensor. Disregarding higher-derivative interactions becomes more questionable due to the existence of higher-derivative theories with just two degrees of freedom that reduce to gravitons at the linear level [31,32] (see also [33,34]).…”

Section: General Relativity As a Constructible Theorymentioning

confidence: 99%

Taming higher-derivative interactions and bootstrapping gravity with soft theorems

Carballo-Rubio

Filippo

Moynihan

2019

J. Cosmol. Astropart. Phys.

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On-shell constructibility is redefining our understanding of perturbative quantum field theory.The tree-level S-matrix of constructible theories is completely determined by a set of recurrence relations and a reduced number of scattering amplitudes. In this paper, we revisit the on-shell constructibility of gravitational theories making use of new results on soft theorems and recurrence relations. We show that using a double complex shift and an all-line soft deformation allows us to relax the technical conditions for constructibility, in order to include more general propagators and higher-derivative interactions that prevent using conventional Britto-Cachazo-Feng-Witten (BCFW) shifts. From this result we extract a set of criteria that guarantee that a given gravitational action has the same tree-level S-matrix in Minkowski spacetime as general relativity, which implies the equivalence at all orders in perturbation theory between these classical field theories on asymptotically flat spacetimes. As a corollary we deduce that the scattering amplitudes of general relativity and unimodular gravity are the same for an arbitrary number of external particles (as long as the S-matrix of the latter is unitary), thus extending previous works that were able to deal only with n = 4 and n = 5 amplitudes.

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“…Thus one needs to impose further constraints on the form of the theory in order to reduce the number of DoFs, i.e., to eliminate the scalar type DoF. A class of "minimally modified gravity" was proposed in [32,33] (see also [34]), which studied the Lagrangian that is linear in the lapse function and derived the conditions for having two tensorial DoFs at the level of Lagrangian. The conditions were also studied directly at the level of the Hamiltonian [35].…”

Section: Introductionmentioning

confidence: 99%

Spatially covariant gravity theories with two tensorial degrees of freedom: The formalism

Gao

Yao

2020

Phys. Rev. D

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Within the general framework of spatially covariant theories of gravity, we study the conditions for having only the two tensorial degrees of freedom. Generally, there are three degrees of freedom propagating in the theory, of which two are tensorial and one is of the scalar type. Through a detailed Hamiltonian analysis, we find two necessary and sufficient conditions to evade the scalar type degree of freedom. The first condition implies that the lapse-extrinsic curvature sector must be degenerate. The second condition ensures that the dimension of the phase space at each spacetime point is even, so that the scalar type degree of freedom is eliminated completely. We also compare our results with the previous studies, and apply our formalism to a simple example, in which the Lagrangian is quadratic in the extrinsic curvature. *

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Phenomenology in type-I minimally modified gravity

Cited by 57 publications

References 24 publications

Minimally modified gravity: a Hamiltonian construction

Minimally modified gravity: a Hamiltonian construction

Taming higher-derivative interactions and bootstrapping gravity with soft theorems

Spatially covariant gravity theories with two tensorial degrees of freedom: The formalism

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