The Physics of Microwave Background Anisotropies

We review the current status of the cosmic microwave background (CMB) radiation, including a brief discussion of some basic theoretical aspects as well as a summary of anisotropy detections and CMB experiments. We focus on the description of some relevant characteristics of the microwave foregrounds, on the discussion of the different estimators proposed in the literature to detect non-Gaussianity and on outlining the bases of different reconstruction methods that have been a...

Long-wavelength gravitational waves can induce significant temperature anisotropy in the cosmic microwave background. Distinguishing this from anisotropy induced by energy density fluctuations is critical for testing inflationary cosmology and theories of large-scale structure formation. We describe full radiative transport calculations of the two contributions and show that they differ dramatically at angular scales below a few degrees. We show how anisotropy experiments pro...

Observations of the cosmic microwave background (CMB), especially of its frequency spectrum and its anisotropies, both in temperature and in polarization, have played a key role in the development of modern cosmology and our understanding of the very early universe. We review the underlying physics of the CMB and how the primordial temperature and polarization anisotropies were imprinted. Possibilities for distinguishing competing cosmological models are emphasized. The curre...

Observational results from several experiments such as COBE, SP, Saskatoon, PYTHON, ARGO, MAX, MSAM, Tenerife and CAT are considered and a comparison is made with predictions from several models. Conclusions are reached about the viability of current structure formation models.

This lecture is a sketch of the physics of the cosmic microwave background. The observed anisotropy can be divided into four main contributions: variations in the temperature and gravitational potential of the primordial plasma, Doppler effect from its motion, and a net red/blueshift the photons accumulate from traveling through evolving gravitational potentials on their way from the primordial plasma to here. These variations are due to primordial perturbations, probably cau...

This is a course on cosmic microwave background (CMB) anisotropies in the standard cosmological model, designed for beginning graduate students and advanced undergraduates. ``Standard cosmological model'' in this context means a Universe dominated by some form of cold dark matter (CDM) with adiabatic perturbations generated at some initial epoch, e.g., Inflation, and left to evolve under gravity alone (which distinguishes it from defect models). The course is primarily theore...

If the large-angular-scale anisotropy in the cosmic microwave background radiation is caused by the long-wavelength cosmological perturbations of quantum mechanical origin, they are, most likely, gravitational waves, rather than density perturbations or rotational perturbations.

This paper presents a complete analysis of the effects of second order gravitational perturbations on Cosmic Microwave Background anisotropies, taking explicitly into account scalar, vector and tensor modes. We also consider the second order perturbations of the metric itself obtaining them, for a universe dominated by a collision-less fluid, in the Poisson gauge, by transforming the known results in the synchronous gauge. We discuss the resulting second order anisotropies in...

While the major contribution to the Cosmic Microwave Background (CMB) anisotropies are the sought-after primordial fluctuations produced at the surface of last scattering, other effects produce secondary fluctuations at lower redshifts. These secondary fluctuations must be carefully accounted for, in order to isolate primordial fluctuations. In addition, they are interesting in their own right, since they provide a wealth of information on the geometry and local properties of...

The standard inflationary model presents a simple scenario within which the homogeneity, isotropy and flatness of the universe appear as natural outcomes and, in addition, fluctuations in the energy density are originated during the inflationary phase. These seminal density fluctuations give rise to fluctuations in the temperature of the Cosmic Microwave Background (CMB) at the decoupling surface. Afterward, the CMB photons propagate almost freely, with slight gravitational i...