Modifications of Einstein's theory of gravitation have been extensively considered in the past years, in connection to both cosmology and quantum gravity. Higher-curvature and higher-derivative gravity theories constitute the main examples of such modifications. These theories exhibit, in general, more degrees of freedom than those found in standard general relativity; counting, identifying, and retrieving the description/representation of such dynamical variables is currently an open problem, and a decidedly nontrivial one. In this work we review, via both formal arguments and custom-made examples, the most relevant methods to unveil the gravitational degrees of freedom of a given model, discussing the merits, subtleties and pitfalls of the various approaches.
Higher-order theories of gravity: diagnosis, extraction and reformulation via non-metric extra degrees of freedom-a review / Belenchia, Alessio; Letizia, Marco; Liberati, Stefano; Di Casola, Eolo. - In: REPORTS ON PROGRESS IN PHYSICS. - ISSN 0034-4885. - 81:3(2018), pp. 1-34.
Titolo: | Higher-order theories of gravity: diagnosis, extraction and reformulation via non-metric extra degrees of freedom-a review |
Autori: | Belenchia, Alessio; Letizia, Marco; Liberati, Stefano; Di Casola, Eolo |
Rivista: | |
Data di pubblicazione: | 2018 |
Digital Object Identifier (DOI): | http://dx.doi.org/10.1088/1361-6633/aaa4ab |
URL: | https://arxiv.org/abs/1612.07749 |
Appare nelle tipologie: | 1.2 Review in journal |
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