Degeneracy, matter coupling, and disformal transformations in scalar-tensor theories
| Autor: | Cédric Deffayet, Sebastian Garcia-Saenz |
|---|---|
| Přispěvatelé: | Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut des Hautes Etudes Scientifiques (IHES), IHES |
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
High Energy Physics - Theory
Cosmology and Nongalactic Astrophysics (astro-ph.CO) General relativity scalar tensor Degrees of freedom (statistics) FOS: Physical sciences alternative theories of gravity General Relativity and Quantum Cosmology (gr-qc) derivative: high spinor: coupling coupling: minimal 01 natural sciences General Relativity and Quantum Cosmology Gravitation Theoretical physics matter: coupling 0103 physical sciences field theory: spinor 010306 general physics metric: time dependence Minimal coupling Physics Spinor 010308 nuclear & particles physics [PHYS.HTHE]Physics [physics]/High Energy Physics - Theory [hep-th] Degenerate energy levels Equations of motion field equations 16. Peace & justice ghost High Energy Physics - Theory (hep-th) gravitation Degeneracy (mathematics) Astrophysics - Cosmology and Nongalactic Astrophysics |
| Zdroj: | Physical Review D Physical Review D, American Physical Society, 2020, 102 (6), pp.064037. ⟨10.1103/PhysRevD.102.064037⟩ Physical Review |
| ISSN: | 1550-7998 1550-2368 |
| Popis: | Degenerate scalar-tensor theories of gravity extend general relativity by a single degree of freedom, despite their equations of motion being higher than second order. In some cases, this is a mere consequence of a disformal field redefinition carried out in a non-degenerate theory. More generally, this is made possible by the existence of an additional constraint that removes the would-be ghost. It has been noted that this constraint can be thwarted when the coupling to matter involves time derivatives of the metric, which results in a modification of the canonical momenta of the gravitational sector. In this note we expand on this issue by analyzing the precise ways in which the extra degree of freedom may reappear upon minimal coupling to matter. Specifically, we study examples of matter sectors that lead either to a direct loss of the special constraint or to a failure to generate a pair of secondary constraints. We also discuss the recurrence of the extra degree of freedom using the language of disformal transformations in particular for what concerns "veiled" gravity. On the positive side, we show that the minimal coupling of spinor fields is healthy and does not spoil the additional constraint. We argue that this virtue of spinor fields to preserve the number of degrees of freedom in the presence of higher derivatives is actually very general and can be seen from the level decomposition of Grassmann-valued classical variables. 29 pages; v2: references added, matches published version |
| Databáze: | OpenAIRE |
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