Cosmological perturbations for imperfect fluids

Abstract

Interacting fluids, endowed with bulk viscous stresses, are discussed in a unified perspective with the aim of generalizing the treatment of cosmological perturbation theory to the case where both fluctuating decay rates and fluctuating bulk viscosity coefficients are simultaneously present in the relativistic plasma. A gauge-invariant treatment of the qualitatively new phenomena arising in this context is provided. In a complementary approach, faithful gauge-fixed descriptions of the gravitational and hydrodynamical fluctuations are developed and exploited. To deepen the interplay between bulk viscous stresses and fluctuating decay rates, illustrative examples are proposed and discussed both analytically and numerically. Particular attention is paid to the coupled evolution of curvature and entropy fluctuations when, in the relativistic plasma, at least one of the interacting fluids possesses a fluctuating bulk viscosity coefficient. It is argued that this class of models may be usefully employed as an effective description of the decay of the inflaton as well as of other phenomena involving imperfect relativistic fluids.

37 pages, 6 included figures; references added, corrected typos, few details added on specific derivations; title slightly changed

References in corpus (7)

• Inhomogeneous Equation of State of the Universe: Phantom Era, Future Singularity and Crossing the Phantom Barrier
• Adiabatic and entropy perturbations with interacting fluids and fields
• Particle decay during inflation: self-decay of inflaton quantum fluctuations during slow roll
• Correlated isocurvature perturbations from mixed inflaton-curvaton decay
• Theoretical tools for CMB physics
• Vector Perturbations in a Contracting Universe
• Rotational inhomogeneities from pre-big bang?

Cited by in corpus (17)

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• Shear viscous effects on the primordial power spectrum from warm inflation
• Matter creation and cosmic acceleration
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• Magnetized CMB observables: a dedicated numerical approach
• Challenging bulk viscous unified scenarios with cosmological observations
• An extensive investigation of the Generalised Dark Matter model
• Stability analysis for the background equations for inflation with dissipation and in a viscous radiation bath
• Interacting viscous dark fluids
• Generalized CMB initial conditions with pre-equality magnetic fields
• Constraints on the generalized tachyon field models from latest observational data
• Why CMB physics?
• Non-linear curvature inhomogeneities and backreaction for relativistic viscous fluids
• Quasiadiabatic modes from viscous inhomogeneities
• Inflating without a flat potential: Viscous inflation
• Viscous modes, isocurvature perturbations and CMB initial conditions
• Covariant Evolution of Gravitoelectromagnetism