If a primordial magnetic field (PMF) is present during photon decoupling and afterward, a finite neutrino mass can affect all modes of the CMB. In this work, we expand on earlier studies of the scalar mode effects by constructing the vector and tensor mode equations in the presence of massive neutrinos and a PMF. We compute the power spectrum of the various modes in an illustrative example and find that the neutrino mass can significantly affect the vector and tensor modes when a PMF exists, while the effects are negligible for no PMF. The most prominent result of the present analysis is the behavior of the EE component of the tensor mode at low multipoles. For massive neutrinos the EE mode can become comparable to the observed primary anisotropy. Therefore, if and when the EE mode power spectrum is measured at low multipoles the possibility exists to place a strong constraint on the sum of the neutrino masses.
A brief outline of the current status of CMB anisotropies and what they might mean, heavily biased towards the perspective of Berkeley theorists. Based on a talk presented at the 17th Texas Symposium on Relativistic Astrophysics held in Munich, December 1994.
Nonlinear gravitational effects of large-scale inhomogeneities on Cosmic Microwave Background (CMB) anisotropies are studied. based on the relativistic second-order theory of perturbations in nonzero-Lambda flat cosmological models, which has been analytically derived by the present author, and on the second-order formula of CMB anisotropies derived by Mollerach and Matarrese. In this paper we derive the components of the CMB anisotropy power spectra in the range of l = 1 -22 which are caused by asymmetric local inhomogeneities on scales of 300 Mpc. Using our results it is found that there is …
Possible signatures of primordial magnetic fields on the Cosmic Microwave Background (CMB) temperature and polarization anisotropies are reviewed. The signals that could be searched for include excess temperature anisotropies particularly at small angular scales below the Silk damping scale, B-mode polarization, and non-Gaussian statistics. A field at a few nG level produces temperature anisotropies at the 5 micro Kelvin level, and B-mode polarization anisotropies 10 times smaller, and is therefore potentially detectable via the CMB anisotropies. An even smaller field, with B_0 < 0.1 nG, could…
This is a review of the theory of CMB anisotropies, an updated version of a course given at the troisieme cycle de la Suisse Romande. An introduction to gauge invariant cosmological perturbation theory is given and the theory CMB anisotropies is develiped in this context. Simple analytical approximations for the acoustic peak positions for adiabatic and isocurvature perturbations are derived. Silk damping is discussed by an analytic approximation. A short description of the present status of observations and parameter estimation followed by a critical discussion terminate the review. The full …
The origin of CMB polarization is reviewed. Special emphasis is placed on the cosmological information encoded in it: the nature of primordial fluctuations, the connection with the inflation paradigm. Insights into more recent epochs are also discussed: early reionization and high redshift matter distribution from CMB lensing.
The ten's of micro-Kelvin variations in the temperature of the cosmic microwave background (CMB) radiation across the sky encode a wealth of information about the Universe. The full-sky, high-resolution maps of the CMB that will be made in the next decade should determine cosmological parameters to unprecedented precision and sharply test inflation and other theories of the early Universe.
We use numerical simulation of cosmological reionization to calculate the secondary CMB anisotropies in a representative flat low density cosmological model. We show that the kinetic Sunyaev-Zel'dovich effect (scattering off of moving electrons in the ionized intergalactic medium) is dominated by the nonlinear hydrodynamic and gravitational evolution of the density and velocity fields, rather than the detailed distribution of the ionization fraction (``patchy reionization'') on all angular scales. Combining our results with the recent calculation of secondary CMB anisotropies by Springel et al…
This article is a written and modified version of a talk presented at the conference `A Century of Cosmology' held at San Servolo, Venice, Italy, in August 2007. The talk focuses on some of the cosmology history leading to the discovery and exploitation of Cosmic Microwave Background (CMB) Radiation anisotropies. We have made tremendous advances first in the development of the techniques to observe these anisotropies and in observing and interpreting them to extract their contained cosmological information. CMB anisotropies are now a cornerstone in our understanding of the cosmos and our futur…
Thomson scattering of the Cosmic Microwave Background (CMB) on moving electrons in the outflows of Lyman Break Galaxies (LBGs) at redshifts 2-8 contributes to the small-scale CMB anisotropies. The net effect produced by each outflow depends on its level of deviation from spherical symmetry, caused either by an anisotropic energy injection from the nuclear starburst or quasar activity, or by an inhomogeneous intergalactic environment. We find that for plausible outflow parameters consistent with spectroscopic observations of LBGs, the induced CMB anisotropies on arcminute scales reach up to $\s…
We address the extended problem of component separation for CMB applications when a mixture of both astrophysical and instrumental components are present in the observations, and show how standard methods can be adapted to handle this more complex inversion problem.
The physics of the origin and evolution of CMB anisotropies is described. I explain the idea and status of cosmic parameter estimation and follow it up with critical comments on its dependence on model assumptions and initial conditions.
We investigate the cosmic variance of the skewness of the cosmic microwave background (CMB) anisotropies in an inflationary model which leads to the baryon isocurvature scenario for the cosmic structure formation. In this model, the baryon number fluctuations are given by a sinusoidal function of a random Gaussian field. We find that the skewness is very small in comparison with that of the fluctuations which obey Gaussian statistics.
We consider a network of topological defects which can partly decay into neutrinos, photons, baryons, or Cold Dark Matter. We find that the degree-scale amplitude of the cosmic microwave background (CMB) anisotropies as well as the shape of the matter power spectrum can be considerably modified when such a decay is taken into account. We conclude that present predictions concerning structure formation by defects might be unreliable.
We study the large scale power spectrum of gravitational wave perturbations of the microwave background in the context of single-bubble open inflation models. We compute the ratio of tensor to scalar contributions to the CMB anisotropies as a function of $Ω_0$, the spectral index $n_S$ and the tunneling parameter $2πGS_1/H$. We find that gravitational wave anisotropies can be very large at small values of this tunneling parameter. We also consider the contribution of supercurvature and bubble wall modes and find constraints on the parameters of open inflation models from the observed temperatu…
We examine the extent to which galactic and extragalactic foregrounds can hamper the detection of primordial Cosmic Microwave Background (CMB) anisotropies. We limit our discussion to intermediate angular scales, $10^{\prime}\lsim θ\lsim 2^{\circ}$, since many current as well as future experiments have been designed to map CMB anisotropies at these angular scales. In fact, scales of $\gsim 10^{\prime}$ are of crucial importance to test both the conditions in the early Universe and current theories of the gravitational collapse.
We study the CMB constraints on two Dark Energy models described by scalar fields with different Lagrangians, namely a Klein-Gordon and a Born-Infeld field. The speed of sound of field fluctuations are different in these two theories, and therefore the predictions for CMB and structure formation are different. Employing the WMAP data on CMB, we make a likelihood analysis on a grid of theoretical models. We constrain the parameters of the models and compute the probability distribution functions for the equation of state. We show that the effect of the different sound speeds affects the low mul…
We study the impact of a stochastic background of primordial magnetic fields on the scalar contribution of CMB anisotropies and on the matter power spectrum. We give the correct initial conditions for cosmological perturbations and the exact expressions for the energy density and Lorentz force associated to the stochastic background of primordial magnetic fields, given a power-law for their spectra cut at a damping scale. The dependence of the CMB temperature and polarization spectra on the relevant parameters of the primordial magnetic fields is illustrated.
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 universe. Here, I survey the different sources of secondary anisotropies and extragalactic foregrounds of the CMB. …
We consider cosmic microwave background (CMB) anisotropy in models with quintessence taking into account of isocurvature fluctuation in the quintessence. It is shown that, if the primordial fluctuation of the quintessence has a correlation with the adiabatic density fluctuations, CMB angular power spectrum $C_l$ at low multipoles can be suppressed without affecting $C_l$ at high multipoles. Possible scenario of generating correlated mixture of the quintessence and adiabatic fluctuations is also discussed.
We study scalar mode perturbations (magnetosonic waves) induced by a helical stochastic cosmological magnetic field and derive analytically the corresponding cosmic microwave background (CMB) temperature and polarization anisotropy angular power spectra. We show that the presence of a stochastic magnetic field, or an homogeneous magnetic field, influences the acoustic oscillation pattern of the CMB anisotropy power spectrum, effectively acting as a reduction of the baryon fraction. We find that the scalar magnetic energy density perturbation contribution to the CMB temperature anisotropy is sm…
I review the basic theory of the cosmic microwave background anisotropies in adiabatic cold dark matter cosmologies. The latest observational results on the CMB power spectrum are consistent with the simplest inflationary models and indicate that the Universe is close to spatially flat with a nearly scale invariant fluctuation spectrum. We are also beginning to see interesting constraints on the density of CDM, with a best fit value of omega_c = Omega_c h^2 of about 0.1. The CMB constraints, when combined with observations of distant Type Ia supernovae, are converging on a Lambda-dominated Uni…
We discuss ability of the harmonic pattern of peaks in the CMB angular power spectrum to test inflation. By studying robust features of alternate models, which must all be isocurvature in nature, we reveal signatures unique to inflation. Inflation thus could be validated by the next generation of experiments.
The 21-cm anisotropies from the neutral hydrogen distribution prior to the era of reionization is a sensitive probe of primordial non-Gaussianity. Unlike the case with cosmic microwave background, 21-cm anisotropies provide multi-redshift information with frequency selection and is not damped at arcminute angular scales. We discuss the angular trispectrum of the 21-cm background anisotropies and discuss how the trispectrum signal generated by the primordial non-Gaussianity can be measured with the three-to-one correlator and the corresponding angular power spectrum. We also discuss the separat…
We present the computation of the full system of Boltzmann equations at second-order describing the evolution of the photon, baryon and cold dark matter fluids. These equations allow to follow the time evolution of the Cosmic Microwave Background (CMB) anisotropies at second-order at all angular scales from the early epoch, when the cosmological perturbations were generated, to the present through the recombination era. This paper sets the stage for the computation of the full second-order radiation transfer function at all scales and for a a generic set of initial conditions specifying the le…
I describe briefly the Cosmic Microwave Background (hereafter CMB) physics which explains why high accuracy observations of its spatial structure are a unique observational tool both for the determination of the global cosmological parameters and to constrain observationally the physics of the early universe. I also briefly survey the many experiments which have measured the anisotropies of the CMB and led to crucial advances in observational Cosmology. The somewhat frantic series of new results has recently culminated with the outcome of the WMAP satellite which confirmed earlier results, set…
In a universe reionized in patches, the Doppler effect from Thomson scattering off free electrons generates secondary cosmic microwave background (CMB) anisotropies. For a simple model with small patches and late reionization, we analytically calculate the anisotropy power spectrum. Patchy reionization can, in principle, be the main source of anisotropies on arcminute scales. On larger angular scales, its contribution to the CMB power spectrum is a small fraction of the primary signal and is only barely detectable in the power spectrum with even an ideal, i.e. cosmic variance limited, experime…
The Cosmic Microwave Background fluctuations provide a powerful probe of the dark ages of the universe through the imprint of the secondary anisotropies associated with the reionisation of the universe and the growth of structure. We review the relation between the secondary anisotropies and and the primary anisotropies that are directly generated by quantum fluctuations in the very early universe. The physics of secondary fluctuations is described, with emphasis on the ionisation history and the evolution of structure. We discuss the different signatures arising from the secondary effects in …
By decomposing the damping tail of CMB anisotropies into a series of transfer functions representing individual physical effects, we provide ingredients that will aid in the reconstruction of the cosmological model from small-scale CMB anisotropy data. We accurately calibrate the model-independent effects of diffusion and reionization damping which provide potentially the most robust information on the background cosmology. Removing these effects, we uncover model-dependent processes such as the acoustic peak modulation and gravitational enhancement that can help distinguish between alternate …
Based on the second-order nonlinear theory of perturbations in non-zero Λflat cosmological models, we study the gravitational effects of local inhomogeneities on cosmic microwave background (CMB) anisotropies. As the local inhomogeneities we consider firstly large-scale dipole and quadruple distributions of galaxies around us and next an isolated cluster-scale matter distribution. It is found that, due to the second-order integral Sachs-Wolfe effect, the north-south asymmetry of CMB anisotropies and non-Gaussian signatures (in terms of scale-dependent estimators of kurtosis) in a spot-like obj…
Thomson scattering of CMBR temperature anisotropies will cause the spectrum of the CMBR to differ from blackbody even when one resolves all anisotropies. A formalism for computing the anisotropic and inhomogeneous spectral distortions of intensity and polarization is derived in terms of Lorentz invariant central moments of the temperature distribution. The formalism is non-perturbative, requiring neither small anisotropies nor small metric or matter inhomogeneities; but it does assume cold electrons. The low order moments are not coupled to the higher order moments allowing one to truncate the…
We generalize the total angular momentum method for computing Cosmic Microwave Background anisotropies to Friedman-Robertson-Walker (FRW) spaces with arbitrary geometries. This unifies the treatment of temperature and polarization anisotropies generated by scalar, vector and tensor perturbations of the fluid, seed, or a scalar field, in a universe with constant comoving curvature. The resulting formalism generalizes and simplifies the calculation of anisotropies and, in its integral form, allows for a fast calculation of model predictions in linear theory for any FRW metric.
We present preliminary results of an analysis into the effects of primordial voids on the cosmic microwave background (CMB). We show that an inflationary bubble model of void formation predicts excess power in the CMB angular power spectrum that peaks between 2000 < l < 3000. Therefore, voids that exist on or close to the last scattering surface at the epoch of decoupling can contribute significantly to the apparent rise in power on these scales recently detected by the Cosmic Background Imager (CBI).
We address the problem of map-making with data from the Planck Surveyor High Frequency Instrument, with an emphasis on the understanding and modelling of instrumental effects, and in particular that of sidelobe straylight. We propose a map-making method which takes advantage of the very special properties of the Planck scanning strategy along circular scans.
Second-order power spectra of Cosmic Microwave Background (CMB) anisotropies due to random primordial perturbations at the matter dominant stage are studied, based on the relativistic second-order theory of perturbations in flat cosmological models and on the second-order formula of CMB anisotropies derived by Mollerach and Matarrese. So far the second-order integrated Sachs-Wolfe effect has been analyzed using the three-point correlation or bispectrum. In this paper we derive the second-order term of power spectra given using the two-point correlation of temperature fluctuations. The second-o…
We present a new, more powerful and accurate, analytic treatment of cosmic microwave background (CMB) anisotropies in the weakly coupled regime. Three applications are presented: gravitational redshifts in a time dependent potential, the Doppler effect in reionized scenarios, and the Vishniac effect. The Vishniac effect can dominate primary anisotropies at small angles even in late and minimally reionized models in flat dark-matter dominated universes with Harrison-Zel'dovich initial conditions. The techniques developed here refine previous calculations yielding a larger coherence angle for th…
We implement the efficient line of sight method to calculate the anisotropy and polarization of the cosmic microwave background for scalar and tensor modes in almost-Friedmann-Robertson-Walker models with positive spatial curvature. We present new results for the polarization power spectra in such models.
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 theoretical and concerned with the physics of CMB anisotropies in this context and their relation to structure formation. Brie…
We discuss the hypotheses that cosmological baryon asymmetry and entropy were produced in the early Universe by phase transition of the scalar fields in the framework of spontaneous baryogenesis scenario. We show that annihilation of the matter-antimatter clouds during the cosmological hydrogen recombination could distort of the CMB anisotropies and polarization by delay of the recombination. After recombination the annihilation of the antibaryonic clouds (ABC) and baryonic matter can produce peak-like reionization at the high redshifts before formation of quasars and early galaxy formation. W…
The analysis of anisotropies in the cosmic microwave background (CMB) has become an extremely valuable tool for cosmology. We even have hopes that planned CMB anisotropy experiments may revolutionize cosmology. Together with determinations of the CMB spectrum, they represent the first cosmological precision measurements. This is illustrated in the talk by Anthony Lasenby. The value of CMB anisotropies lies to a big part in the simplicity of the theoretical analysis. Fluctuations in the CMB can be determined almost fully within linear cosmological perturbations theory and are not severely influ…
Anisotropies in the cosmic microwave background radiation due to gravity waves are investigated. An initial spectrum of gravity waves may have been induced during an epoch of inflation. We study the propagation of such a spectrum in a Friedmann background of hot and cold dark matter, radiation and (possibly) a cosmological constant. We finally calculate its imprint as anisotropies on the cosmic microwave background. We also take into account that massless particles can source gravity waves by their anisotropic stresses. We consider general mixed dark matter models with and without cosmological…
We are now beginning to learn detailed information about cosmological parameters from the shapes of the matter and radiation power spectra, together with their relative normalization. As more high quality data are gathered from galaxy surveys and from microwave anisotropies, the range of allowed models is expected to get incrementally smaller. The amount of information potentially available from a high-resolution satellite experiment should allow a determination of essentially {\it all} currently discussed cosmological parameters to less than ~10%.
Australia Telescope Compact Array (ATCA) observations in sky regions selected to be low in foreground confusion have been used to infer limits on arcmin-scale CMB anisotropy in total intensity and polarization. These deep searches have, hitherto, been made using the East-West ATCA in an ultra-compact 1-D array configuration and in the highest available frequency band at 3-cm wavelength. The ATCA is being upgraded for operation at mm wavelengths and in 2-D array configurations: the enhanced capabilities present a new opportunity for pursuing CMB anisotropy related observations with reduced fore…
We discuss the polarization signature of primordial gravitational waves imprinted in cosmic microwave background (CMB) anisotropies. The high-energy physics motivated by superstring theory or M-theory generically yield parity violating terms, which may produce a circularly polarized gravitational wave background (GWB) during inflation. In contrast to the standard prediction of inflation with un-polarized GWB, circularly polarized GWB generates non-vanishing TB and EB-mode power spectra of CMB anisotropies. We evaluate the TB and EB-mode power spectra taking into account the secondary effects a…
It is well known that processes of first order phase transitions may have occurred in the inflationary era. If one or more occurred well before the end of inflation, the nucleated bubbles are stretched to large scales and the primordial power spectrum contains a scale dependent non-Gaussian component provided by the remnants of the bubbles. We predict the anisotropies in the cosmic microwave background (CMB) induced by inflationary bubbles. We build a general analytic model for describing a bubbly perturbation; we evolve each Fourier mode using the linear theory of perturbations from reheating…
The cross-correlation between cosmic microwave background (CMB) temperature anisotropies and the large scale structure (LSS) traced by the galaxy distribution, or sources at different wavelengths, is now well known. This correlation results from the integrated Sachs-Wolfe (ISW) effect in CMB anisotropies generated at late times due to the dark energy component of the Universe. In a reionized universe, the ISW quadrupole rescatters and contributes to the large-scale polarization signal. Thus, in principle, the large-scale polarization bump in the E-mode should also be correlated with the galaxy…
Phase transitions taking place during the inflationary epoch give rise to bubbles of true vacuum embedded in the false vacuum. These bubbles can imprint a distinctive signal on the Cosmic Microwave Background (CMB). We evaluate the feasibility of detecting these signatures with waveletsin CMB maps, such as those that will be made available by the European Space Agency's (ESA) Planck mission.
The non-Gaussianity of initial perturbations provides information on the mechanism that generated primordial density fluctuations. The expected non-Gaussianity for slow-roll inflationary models is well below the ultimate detection level with cosmic microwave background (CMB) anisotropies or large-large structure at low redshifts. We find that 21-cm background anisotropies of the low-frequency radio sky due to inhomogeneous neutral Hydrogen distribution at redshifts between 30 and 100 captures information on primordial non-Gaussianity better than any other cosmological probe. An all-sky 21-cm e…
We study the contribution of a stochastic background (SB) of primordial magnetic fields (PMF) on the anisotropies in temperature and polarization of the cosmic microwave background radiation (CMB). A SB of PMF modelled as a fully inhomogeneous component induces non-gaussian scalar, vector and tensor metric linear perturbations. We give the exact expressions for the Fourier spectra of the relevant energy-momentum components of such SB, given a power-law dependence parametrized by a spectral index $n_B$ for the magnetic field power spectrum cut at a damping scale $k_D$. For all the values of $n_…
We consider the problem of numerical computation of the Kolmogorov complexity and the fractal dimension of the anisotropy spots of Cosmic Microwave Background (CMB) radiation. Namely, we describe an algorithm of estimation of the complexity of spots given by certain pixel configuration on a grid and represent the results of computations for a series of structures of different complexity. Thus, we demonstrate the calculability of such an abstract descriptor as the Kolmogorov complexity for CMB digitized maps. The correlation of complexity of the anisotropy spots with their fractal dimension is …
Most of the cosmological information extracted from the CMB has been obtained through the power spectrum, however there is much more to be learnt from the statistical distribution of the temperature random field. We review some recent developments in the study of the Cosmic Microwave Background (CMB) anisotropies and present a description of the novel tools developed to analyse the properties of the CMB anisotropies beyond the power spectrum.
We consider the effects of photon diffusion on the small-angle microwave background anisotropies due to active source models. We find that fluctuations created just before the time of last scattering allow anisotropy to be created on scales much smaller than allowed by standard Silk damping. Using simple models for string and texture structure functions as examples, we illustrate the differences in the angular power spectrum at scales of order a few arcminutes. In particular, we find that the Doppler peak heights are modified by 10-50% and the small-angle fall-off is power law rather than expo…
Archeops is a balloon-borne instrument dedicated to measuring cosmic microwave background (CMB) temperature anisotropies at high angular resolution (8 arcminutes) over a large fraction (25%) of the sky in the millimetre domain. Based on Planck High Frequency Instrument (HFI) technology, cooled bolometers (0.1 K) scan the sky in total power mode with large circles at constant elevation. During the course of a 24-hour Arctic-night balloon flight, Archeops will observe a complete annulus on the sky in four frequency bands centered at 143, 217, 353 and 545 GHz with an expected sensitivity to CMB f…
We discuss three recent developments in the calculation of CMB anisotropies. First, we consider relativistic corrections to the Sunyaev-Zel'dovich effect. By extending the Kompaneets equation to the relativistic domain we are able to derive simple analytic forms for the SZ spectral distortion. Second, we discuss covariant kinetic theory methods for the gauge-invariant calculation of CMB anisotropies. We present a covariant version of the Boltzmann equation which we use to derive covariant and gauge-invariant equations describing a CDM model, which are independent of background curvature and ty…
We present an analytic model, based on previous works which tackled the reionization history of the universe, which allows us to describe the generation of the secondary CMB anisotropies due to the kinetic SZ effect. We take into account the "patchy pattern" of reionization (HII bubbles), the cross-correlations of these ionized regions, the small-scale fluctuations of the matter density field and the contribution from collapsed objects. For an open universe, we find that the power-spectrum $l(l+1)C_l/(2π)$ exhibits a plateau of height $10^{-13}$ in the range $10^3 < l < 10^6$. We find that for…
We review the theoretical implications of the past decade of CMB anisotropy measurements, which culminated in the recent detection of the first feature in the power spectrum, and discuss the tests available to the next decade of experiments. The current data already suggest that density perturbations originated in an inflationary epoch, the universe is spatially flat, and baryonic dark matter is required. We discuss the underlying assumptions of these claims and outline the tests required to ensure they are robust. The most critical test - the presence of a second feature at the predicted loca…
The linear anisotropies in the temperature of the cosmic microwave background (CMB) radiation and its polarization provide a clean picture of fluctuations in the universe some 370 kyr after the big bang. Simple physics connects these fluctuations with those present in the ultra-high-energy universe, and this makes the CMB anisotropies a powerful tool for constraining the fundamental physics that was responsible for the generation of structure. Late-time effects also leave their mark, making the CMB temperature and polarization useful probes of dark energy and the astrophysics of reionization. …
Recent work has emphasised the importance of vector and tensor contributions to the large scale microwave anisotropy fluctuations produced by cosmic defects. In this paper we provide a general discussion of these contributions, and how their magnitude is constrained by the fundamental assumptions of causality, scaling, and statistical isotropy. We discuss an analytic model which illustrates and explains how the ratios of isotropic and anisotropic scalar, vector and tensor microwave anisotropies are determined. This provides a check of the results from large scale numerical simulations, confirm…
During the transition from a neutral to a fully reionized universe, scattering of cosmic microwave background (CMB) photons via free-electrons leads to a new anisotropy contribution to the temperature distribution. If the reionization process is inhomogeneous and patchy, the era of reionization is also visible via brightness temperature fluctuations in the redshifted 21 cm line emission from neutral Hydrogen. Since regions containing electrons and neutral Hydrogen are expected to trace the same underlying density field, the two are (anti) correlated and this is expected to be reflected in the …
The power spectrum of fluctuations in the cosmic microwave background (CMB) depends on most of the key cosmological parameters. Accurate future measurements of this power spectrum might therefore allow us to determine h, Omega, Omega_b, Lambda, n, T/S, etc, with hitherto unprecedented accuracy. In these lecture notes, which are intended to be readable without much prior CMB knowledge, I review the various physical processes that generate CMB fluctuations, focusing on how changes in the parameters alters the shape of the power spectrum. I also discuss foregrounds and real-world data analysis is…
We study the effect of gravitational time delay on the power spectra and bispectra of the cosmic microwave background (CMB) temperature and polarization anisotropies. The time delay effect modulates the spatial surface at recombination on which temperature anisotropies are observed, typically by ~1 Mpc. While this is a relatively large shift, its observable effects in the temperature and polarization fields are suppressed by geometric considerations. The leading order effect is from its correlation with the closely related gravitational lensing effect. The change to the temperature-polarizatio…
