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Lately I've seen many papers (for example "The galileon as a local modification of gravity"; 292 total hits on the arXiv) on types of field theories known as Galileons, and I'm wondering what the motivation for studying them is. I often hear of them in the context of "well-behaved" IR modifications of general relativity. For example, Galileons are known to arise from brane-localised theories of gravity as well as ghost-free massive gravity, which are themselves IR modifications of general relativity.

I understand that it is attractive to understand possible IR modifications of gravity for cosmological purposes (in particular, dark energy). My question is this: aside from being (or perhaps being closely related to) an IR modification of gravity (in general), what attractive feature do Galileons possess? Do they modify the IR of gravity in a way that could account for dark energy? Is it too early in the study of Galileons to tell?

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  • $\begingroup$ Example papers (picked at semi-random): arxiv.org/abs/0811.2197, arxiv.org/abs/1103.3260. 289 total hits on arXiv for "galileon". $\endgroup$
    – ACuriousMind
    Mar 17, 2015 at 19:11
  • $\begingroup$ Thanks, Curious. I was hoping to get a quick answer here before deciding if I was interested enough to start digging through the literature myself. $\endgroup$ Mar 17, 2015 at 19:22
  • $\begingroup$ I'm interested in the answer to this myself, and don't know much about them, either - I just wanted to post some examples to show other people what you are talking about. $\endgroup$
    – ACuriousMind
    Mar 17, 2015 at 19:24
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    $\begingroup$ Ah, very good. I got started on this because in addition to hearing about them for awhile, I read this recent paper arxiv.org/abs/1503.01024 which addresses the state-of-the-art in how to build galileons, but doesn't go into any detail of their attractive properties. $\endgroup$ Mar 17, 2015 at 19:28
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    $\begingroup$ I don't have time to write a full answer now, but basically galileons are scalar field theories with special derivative interactions. They arise as basically a high energy limit in various theories of modified (in the ir) gravity, for example in some limit they describe the helicity 0 mode of a massive graviton in dRGT massive gravity. They are attractive mostly because they exhibit the vainshtein screening mechanism. They also exhibit unwanted features such as superluminality around some backgrounds, which is the subject of much debate. $\endgroup$
    – Andrew
    Mar 17, 2015 at 21:00

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