Adiabatic and entropy perturbations with interacting fluids and fields

K. Malik, David Wands

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We develop a gauge-invariant formalism for the study of density perturbations in a Friedmann–Robertson–Walker universe with multiple interacting fluids and/or scalar fields. We show how N scalar fields may be described by N kinetic fluids (with maximally stiff equation of state) interacting with a non-dynamical potential (with vacuum equation of state). We split generic perturbations into adiabatic and entropic parts, and give the coupled first-order evolution equations on all scales, including energy and momentum exchange. We identify the non-adiabatic effects on large scales, and define adiabatic initial conditions in the presence of multiple fluids and fields.
Original languageEnglish
Pages (from-to)007-007
Number of pages1
JournalJournal of Cosmology and Astroparticle Physics
Issue number02
Publication statusPublished - 2005


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