Higher order gravities and the Strong Equivalence Principle

Ortı́n, Tomás

doi:10.1007/jhep09(2017)152

Cited by 5 publications

(6 citation statements)

References 80 publications

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“…A natural idea would be to first relate universal coupling of the (quantum) spin-2 field to universal coupling of g, and then argue that SEP-GR follows. Note, however, that universal coupling of g might indeed be viewed simply as one of the requirements for SEP-GR, but there may be other requirements as well (similarly, see Ortín (2017)). For example, one might want to additionally exclude certain types of (non-dynamical) fixed fields from the theory (e.g., fixed timelike vector fields), as they can violate Lorentz invariance.…”

Section: Lesson I: a Closer Look At The Equivalence Principlementioning

confidence: 99%

“…In particular, self-coupling is necessary if any coupling to matter is to be included. Accordingly, WEP-like statements in this context also encompass that "gravitational binding energy of massive bodies will not modify their free-fall motion" (Ortín, 2017). 45 This suggests that the universal coupling reformulation-irrespective of how WEP-like it is-is indeed the most general or strongest possible reinterpretation of the equivalence principles (i.e., UC-Strong).…”

Section: Lesson I: a Closer Look At The Equivalence Principlementioning

confidence: 99%

“…This can be interpreted as a WEP-like statement. However, since graviton self-coupling is a necessary requirement if any coupling to matter is to be allowed, it is suggested that it is in fact the most general (i.e., the strongest) version of the possible equivalence principles that obtains in this context: a 'microscopic version' (Ortín, 2017) of the SEP. 47 Accordingly, energy-momentum of gravitational fields is indistinguishable from energy-momentum of non-gravitational fields and the source for the gravitational field is the total energy-momentum tensor.…”

Section: Lesson I: a Closer Look At The Equivalence Principlementioning

confidence: 99%

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The dynamical approach to spin-2 gravity

Salimkhani

2020

Studies in History and Philosophy of Science Part B: Studies in

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This paper engages with the following closely related questions that have recently received some attention in the literature: (a) what is the status of the equivalence principle in general relativity (GR)?; (b) how does the metric field obtain its property of being able to act as a metric?; and (c) is the metric of GR derivative on the dynamics of the matter fields? The paper attempts to complement these debates by studying the spin-2 approach to (quantum) gravity. In particular, the paper argues that three lessons can be drawn from the spin-2 approach: (1) different from what is sometimes claimed in the literature, central aspects of the non-linear theory of GR are already derivable in classical spin-2 theory; in particular, 'universal coupling' can be considered a derived 'theorem' in both the classical and the quantum spin-2 approach; this provides new insights for the investigation of the equivalence principle; (2) the 'second miracle' that Read et al. argue characterises GR is explained in the classical as well as in the quantum version of the spin-2 approach; (3) the spin-2 approach allows for an ontological reduction of the metrical part of spacetime to the dynamics of matter fields.

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Section: Lesson I: a Closer Look At The Equivalence Principlementioning

confidence: 99%

Section: Lesson I: a Closer Look At The Equivalence Principlementioning

confidence: 99%

Section: Lesson I: a Closer Look At The Equivalence Principlementioning

confidence: 99%

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The dynamical approach to spin-2 gravity

Salimkhani

2020

Studies in History and Philosophy of Science Part B: Studies in

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“…Nevertheless, analysis like that of Butcher et al [16] do not seem to leave the room for other solutions to the self-coupling problem. Specially interesting are the recent works on the self-coupling of higher derivative theories [16,18,19]. Whereas in [16,19] it was found that higher-derivatives theories bootstrap in the same sense than GR does, in [18], by working in first-order formalism, the author concluded that they do not unless one enforces "by hand" the condition that the connection is the Levi-Civita connection associated with the full metric.…”

Section: Introductionmentioning

confidence: 99%

Bootstrapping gravity and its extension to metric-affine theories

Delhom,

García-Moreno,

Hohmann

et al. 2023

J. Cosmol. Astropart. Phys.

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In this work we study diffeomorphism-invariant metric-affine theories of gravity from the point of view of self-interacting field theories on top of Minkowski spacetime (or other background). We revise how standard metric theories couple to their own energy-momentum tensor, and discuss the generalization of these ideas when torsion and nonmetricity are also present. We review the computation of the corresponding currents through the Hilbert and canonical (Noether) prescriptions, emphasizing the potential ambiguities arising from both. We also provide the extension of this consistent self-coupling procedure to the vielbein formalism, so that fermions can be included in the matter sector. In addition, we clarify some subtle issues regarding previous discussions on the self-coupling problem for metric theories, both General Relativity and its higher derivative generalizations. We also suggest a connection between Lovelock theorem and the ambiguities in the bootstrapping procedure arising from those in the definition of conserved currents.

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“…Thus, we will study what are the minimal requirements to build a theory of massless gravitons and where the bifurcation appears. Additionally, we will answer two long standing questions about UG that are not well-understood in the literature yet -how does the equivalence principle arises in the theory [35] and what is the relation of its S-matrix with the one of GR.…”

Section: Introductionmentioning

confidence: 99%

What do gravitons say about (unimodular) gravity?

Herrero-Valea

2018

J. High Energ. Phys.

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We revisit the problem of constraining the weak field limit of the gravitational lagrangian from S-matrix properties. From unitarity and Lorentz invariance of the S-matrix of massless gravitons, we derive on-shell gauge invariance to consist on the transverse part of the linearised diffeomorphisms group. Moreover, by looking to the interaction between sources, we conclude that there exist only two possible lagrangians that lead to a well-defined covariant interaction, corresponding to the weak field limits of General Relativity and Unimodular Gravity. Additionally, this result confirms the equivalence of the S-matrix of both theories around flat space-time.

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Higher order gravities and the Strong Equivalence Principle

Cited by 5 publications

References 80 publications

The dynamical approach to spin-2 gravity

The dynamical approach to spin-2 gravity

Bootstrapping gravity and its extension to metric-affine theories

What do gravitons say about (unimodular) gravity?

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