Theoretical Tools for CMB Physics

Giovannini, Massimo

doi:10.1142/s0218271805006687

Cited by 60 publications

(109 citation statements)

References 331 publications

(528 reference statements)

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“…If we consider N scalar fields with Lagrangian density 51) and minimal coupling to gravity, then the total energy, pressure and momentum perturbations are given by…”

Section: Multiple Fieldsmentioning

confidence: 99%

“…[88,70,86,93,84,77,17,174] and for cosmic microwave background anisotropies see, e.g., Refs. [67,82,42,51] Finally, for reviews on perturbation theory in the context of the higherdimensional brane-world scenario see, e.g., Refs. [68,24,135,100,23] and for perturbation theory in the context of the low-energy string effective action see, e.g., Refs.…”

Section: Introductionmentioning

confidence: 99%

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Cosmological perturbations

Malik¹,

Wands²

2009

Physics Reports

551

862

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We review the study of inhomogeneous perturbations about a homogeneous and isotropic background cosmology. We adopt a coordinate based approach, but give geometrical interpretations of metric perturbations in terms of the expansion, shear and curvature of constant-time hypersurfaces and the orthogonal timelike vector field. We give the gauge transformation rules for metric and matter variables at first and second order. We show how gauge invariant variables are constructed by identifying geometric or matter variables in physically-defined coordinate systems, and give the relations between many commonly used gauge-invariant variables. In particular we show how the Einstein equations or energy-momentum conservation can be used to obtain simple evolution equations at linear order, and discuss extensions to non-linear order. We present evolution equations for systems with multiple interacting fluids and scalar fields, identifying adiabatic and entropy perturbations. As an application we consider the origin of primordial curvature and isocurvature perturbations from field perturbations during inflation in the very early universe.

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“…If we consider N scalar fields with Lagrangian density 51) and minimal coupling to gravity, then the total energy, pressure and momentum perturbations are given by…”

Section: Multiple Fieldsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cosmological perturbations

Malik¹,

Wands²

2009

Physics Reports

551

862

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show abstract

“…There is also another physical quantity that plays an important rôle in our considerations, namely the curvature fluctuation on uniform density hypersurfaces (see, for instance, [52]). The fluctuations of the (total) curvature on uniform density hypersurfaces have a gauge-invariant interpretation and they can be defined as…”

Section: Curvature and Entropy Perturbationsmentioning

confidence: 99%

Cosmological perturbations for imperfect fluids

Giovannini

2005

Class. Quantum Grav.

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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.

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“…Although there are several different inflationary scenarios most of them predict a nearly gaussian and nearly scale invariant power spectrum of adiabatic fluctuations.For reviews see [5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…This simple, yet observationally supported inflationary scenario is referred to as slow-roll inflation [5][6][7][8][9]. Within this scenario wave vectors of cosmological relevance cross the Hubble radius during inflation with nearly constant amplitude leading to a nearly scale invariant power spectrum.…”

Section: Introductionmentioning

confidence: 99%

Pre-slow-roll initial conditions: Large scale power suppression and infrared aspects during inflation

2014

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If the large scale anomalies in the temperature power spectrum of the cosmic microwave background are of primordial origin, they may herald modifications to the slow roll inflationary paradigm on the largest scales. We study the possibility that the origin of the large scale power suppression is a modification of initial conditions during slow roll as a result of a pre-slow roll phase during which the inflaton evolves rapidly. This stage is manifest in a potential in the equations for the Gaussian fluctuations during slow roll and modify the power spectra of scalar perturbations via an initial condition transfer function T (k). We provide a general analytical study of its large and small scale properties and analyze the impact of these initial conditions on the infrared aspects of typical test scalar fields. The infrared behavior of massless minimally coupled test scalar field theories leads to the dynamical generation of mass and anomalous dimensions, both depend non-analytically on T (0). During inflation all quanta decay into many quanta even of the same field because of the lack of kinematic thresholds. The decay leads to a quantum entangled state of sub and superhorizon quanta with correlations across the horizon. We find the modifications of the decay width and the entanglement entropy from the initial conditions. In all cases, initial conditions from a "fast-roll" stage that lead to a suppression in the scalar power spectrum at large scales also result in a suppression of the dynamically generated masses, anomalous dimensions and decay widths.

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Theoretical Tools for CMB Physics

Cited by 60 publications

References 331 publications

Cosmological perturbations

Cosmological perturbations

Cosmological perturbations for imperfect fluids

Pre-slow-roll initial conditions: Large scale power suppression and infrared aspects during inflation

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