Complete density perturbations in the Jordan-Fierz-Brans-Dicke theory
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2013
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American Physical Society
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Abstract
In the context of scalar-tensor theories we study the evolution of the density contrast for Jordan-Fierz-Brans-Dicke theories in a Friedmann-Lemaitre-Robertson-Walker universe. Calculations are performed in the Einstein frame with the cosmological background described as Lambda-cold dark matter (Lambda CDM) and supplemented by a Jordan-Fierz-Brans-Dicke field. By using a completely general procedure valid for all scalar-tensor theories, we obtain the exact fourth-order differential equation for the density contrast evolution in modes of arbitrary size. In the case of sub-Hubble modes, the expression reduces to a simpler but still fourth-order equation that is then compared with the standard (quasistatic) approximation. Differences with respect to the evolution as predicted by the standard concordance Lambda CDM model are observed depending on the value of the coupling.
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© 2013 American Physical Society. J. A. R. C. and A. d. l. C. D. acknowledge financial support from MINECO (Spain) Projects No. FIS2011-23000, No. FPA2011-27853-C02-01 and Consolider-Ingenio MULTIDARK CSD2009-00064. A. d. l. C. D. also acknowledges financial support from Marie Curie-Beatriu de Pinos Contract No. BP-B00195, Generalitat de Catalunya and ACGC, University of Cape Town. L. O. G. is indebted to the Theoretical Physics Department, Complutense University of Madrid for the use of technical resources. A. d. l. C. D acknowledges the hospitality of Kavli Institute for Theoretical Physics China (KITPC), Chinese Academy of Sciences, during the last stages of this manuscript.