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Disformal transformations on the CMB

Burrage, Clare; Cespedes, Sebastian; Davis, Anne-Christine


Sebastian Cespedes

Anne-Christine Davis


In this work we study the role of disformal transformation on cosmological backgrounds and its relation to the speed of sound for tensor modes. A speed different from one for tensor modes can arise in several contexts, such as Galileons theories or massive gravity, nevertheless the speed is very constrained to be one by observations of gravitational wave emission. It has been shown that in inflation a disformal trans- formation allows to set the speed for tensor modes to one without making changes to the curvature power spectrum. Here we show that this invariance does not hold when considering the CMB anisotropy power spectrum. It turns out that the after doing the transformation there is an imprint on the acoustic peaks and the diffusion damping. This has interesting consequences; here we explore quartic galileon theories which allow a modified speed for tensor modes. For these theories the transformation can be used to constraint the parameter space in different regimes


Burrage, C., Cespedes, S., & Davis, A. (2016). Disformal transformations on the CMB. Journal of Cosmology and Astroparticle Physics, 2016,

Journal Article Type Article
Acceptance Date Jul 26, 2016
Publication Date Aug 11, 2016
Deposit Date Jan 3, 2017
Publicly Available Date Jan 3, 2017
Journal Journal of Cosmology and Astroparticle Physics
Electronic ISSN 1475-7516
Publisher IOP Publishing
Peer Reviewed Peer Reviewed
Volume 2016
Public URL
Publisher URL


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