Dark Matter (DM) annihilation and decay during the Dark Ages can affect the cosmic ionization history and leave imprints in the Cosmic Microwave Background (CMB) anisotropy spectra. CMB polarization anisotropy can be sensitive to such energy injection at higher redshifts and help reducing degeneracy with primordial spectral parameters in $Λ$CDM and astrophysical ionization processes during reionization. In light of a number of upcoming CMB polarization experiments, such as AdvACTPol, AliCPT, CLASS, Simons Observatory, Simons Array, SPT-3G, we estimate their prospective sensitivity in probing dark matter annihilation and decay signals. We find that future missions have 95\% C.L. projected limits on DM decay and annihilation rates to orders of $Γ_χ(τ_χ^{-1}) \sim 10^{-27}{\rm{s}}^{-1}$ and $\left<σv \right>/m_χ \sim 10^{-29}{\rm{cm^3s^{-1}GeV^{-1}}}$ respectively, significantly improving the sensitivity to DM from current experimental bounds.
From measurements of the cosmic microwave background (CMB), the effective number of neutrino is found to be close to the standard model value Neff = 3.046 for the \LambdaCDM cosmology. One can obtain the same CMB angular power spectrum as that of \LambdaCDM for the different value of Neff by using the different dark energy model (i.e. for the different value of w). This degeneracy between Neff and w in CMB can be broken from future galaxy survey using the matter power spectrum.
Compensated isocurvature perturbations (CIPs) are primordial fluctuations that balance baryon and dark-matter isocurvature to leave the total matter density unperturbed. The effects of CIPs on the cosmic microwave background (CMB) anisotropies are similar to those produced by weak lensing of the CMB: smoothing of the power spectrum, and generation of non-Gaussian features. Previous work considered the CIP effects on the CMB power-spectrum but neglected to include the CIP effects on estimates of the lensing potential power spectrum (though its contribution to the non-Gaussian, connected, part o…
Axion-like particles (ALPs) rotate the linear polarization of photons through the ALP-photon coupling and convert the cosmic microwave background (CMB) $E$-mode to the $B$-mode. We derive the relation between the ALP dynamics and the rotation angle by assuming that the ALP $ϕ$ has a quadratic potential, $V=m^2ϕ^2/2$. We compute the current and future sensitivities of CMB observations to the ALP-photon coupling $g$, which can reach $g=4\times 10^{-21}\,\mathrm{GeV}^{-1}$ for $10^{-32}\,\mathrm{eV}\lesssim m\lesssim 10^{-28}\,\mathrm{eV}$ and extensively exceed the other searches for any mass $m…
In the curvaton scenario, primordial curvature perturbations are produced by a second field that is sub-dominant during inflation. Depending on how the curvaton decays [possibly producing baryon number, lepton number, or cold dark matter (CDM)], mixtures of correlated isocurvature perturbations are produced, allowing the curvaton scenario to be tested using cosmic microwave background (CMB) data. Here, a full range of 27 curvaton-decay scenarios is compared with CMB data, placing limits on the curvaton fraction at decay, $r_D$, and the lepton asymmetry, $ξ_{\rm lep}$. If baryon number is gener…
We investigate the issue of how accurately we can constrain the lepton number asymmetry xi_nu = mu_nu/T_nu in the Universe by using future observations of 21 cm line fluctuations and cosmic microwave background (CMB). We find that combinations of the 21 cm line and the CMB observations can constrain the lepton asymmetry better than big-bang nucleosynthesis (BBN). Additionally, we also discuss constraints on xi_nu in the presence of some extra radiation, and show that the 21 cm line observations can substantially improve the constraints obtained by CMB alone, and allow us to distinguish the eff…
We perform a comprehensive study of the signatures of Lorentz violation in electrodynamics on the Cosmic Microwave Background (CMB) anisotropies. In the framework of the minimal Standard Model Extension (SME), we consider effects generated by renormalizable operators, both CPT-odd and CPT-even. These operators are responsible for sourcing, respectively, cosmic birefringence and circular polarization. We propagate jointly the effects of all the relevant Lorentz-violating parameters to CMB observables and provide constraints with the most recent CMB datasets. We bound the CPT-even coefficient to…
We update the constraint on the dark matter annihilation cross section by using the recent measurements of the CMB anisotropy by the Planck satellite. We fully calculate the cascade of dark matter annihilation products and their effects on ionization, heating and excitation of the hydrogen, hence do not rely on any assumption on the energy fractions that cause these effects.
Many extensions of Standard Model (SM) include a dark sector which can interact with the SM sector via a light mediator. We explore the possibilities to probe such a dark sector by studying the distortion of the CMB spectrum from the blackbody shape due to the elastic scatterings between the dark matter and baryons through a hidden light mediator. We in particular focus on the model where the dark sector gauge boson kinetically mixes with the SM and present the future experimental prospect for a PIXIE-like experiment along with its comparison to the existing bounds from complementary terrestri…
The fine-structure constant, $α$, controls the strength of the electromagnetic interaction. There are extensions of the standard model in which $α$ is dynamical on cosmological length and time-scales. The physics of the cosmic microwave background (CMB) depends on the value of $α$. The effects of spatial variation in $α$ on the CMB are similar to those produced by weak lensing: smoothing of the power spectrum, and generation of non-Gaussian features. These would induce a bias to estimates of the weak-lensing potential power spectrum of the CMB. Using this effect, Planck measurements of the tem…
Mirror dark matter is a dissipative and self-interacting multiparticle dark matter candidate which can explain the DAMA, CoGeNT and CRESST-II direct detection experiments. This explanation requires photon-mirror photon kinetic mixing of strength $ε\sim 10^{-9}$. Mirror dark matter with such kinetic mixing can potentially leave distinctive signatures on the CMB anisotropy spectrum. We show that the most important effect of kinetic mixing on the CMB anisotropies is the suppression of the height of the third and higher odd peaks. If $ε\stackrel{>}{\sim} 10^{-9}$ then this feature can be observed …
The nature of dark matter is one of the major puzzles of fundamental physics, integral to the understanding of our universe across almost every epoch. The search for dark matter takes place at different energy scales, and use data ranging from particle colliders to astrophysical surveys. We focus here on CMB-S4, a future ground-based Cosmic Microwave Background (CMB) experiment, which is expected to provide exquisite measurements of the CMB temperature and polarization anisotropies. These measurements (on their own and in combination with other surveys) will allow for new means to shed light o…
We briefly discuss the intriguing case of a phenomenological non-gravitational coupling in the dark sector, where the interaction is parameterized as an energy transfer either from dark matter to dark energy or the opposite. We show that a non-zero coupling with an energy flow from the latter to the former leads to a full reconciliation of the tension between high- and low-redshift observations present in the standard cosmological model.
We present new Big Bang Nucleosynthesis (BBN) limits on the cosmic expansion rate or relativistic energy density, quantified via the number $N_ν$ of equivalent neutrino species. We use the latest light element observations, neutron mean lifetime, and update our evaluation for the nuclear rates $d+d \rightarrow He3 + n$ and $d+d \rightarrow H3 + p$. Combining this result with the independent constraints from the cosmic microwave background (CMB) yields tight limits on new physics that perturbs $N_ν$ and $η$ prior to cosmic nucleosynthesis: a joint BBN+CMB analysis gives $N_ν= 2.898 \pm 0.141$, …
Since the temperature fluctuations in cosmic microwave background (CMB) on large-angular scales probe length scales that were super-horizon sized at photon decoupling and hence insensitive to microphysical processes, the low-multipole CMB data are supposed to be a good probe to the physics of the primordial Universe. In this letter we will constrain the cosmological parameters in the base $Λ$CDM model with tensor perturbations by only using low-multipole CMB data, including Background Imaging of Cosmic Extragalactic Polarization (B2), Planck released in 2013 (P13) and Wilkinson Microwaves Anis…
Dark sectors provide a compelling theoretical framework for thermally producing sub-GeV dark matter, and motivate an expansive new accelerator and direct-detection experimental program. We demonstrate the power of constraining such dark sectors using the measured effective number of neutrino species, $N_\text{eff}$, from the Cosmic Microwave Background (CMB) and primordial elemental abundances from Big Bang Nucleosynthesis (BBN). As a concrete example, we consider a dark matter particle of arbitrary spin that interacts with the Standard Model via a massive dark photon, accounting for an arbitr…
Primordial magnetic fields (PMF) can create polarization $B$-modes in the cosmic microwave background (CMB) through Faraday rotation (FR), leading to non-trivial 2-point and 4-point correlators of the CMB temperature and polarization. We discuss the detectability of primordial magnetic fields using different correlators and evaluate their relative merits. We have fully accounted for the contamination by weak lensing, which contributes to the variance, but whose contribution to the 4-point correlations is orthogonal to that of FR. We show that a Planck-like experiment can detect scale-invariant…
The cosmic history before the BBN is highly determined by the physics that operates beyond the Standard Model (BSM) of particle physics and it is poorly constrained observationally. Ongoing and future precision measurements of the CMB observables can provide us with significant information about the pre-BBN era and hence possibly test the cosmological predictions of different BSM scenarios. Supersymmetry is a particularly motivated BSM theory and it is often the case that different superymmetry breaking schemes require different cosmic histories with specific reheating temperatures or low entr…
We investigate the degree to which the Cosmic Microwave Background (CMB) can be used to constrain primordial non-Gaussianity coming from the presence of spinning particles coupled to the inflaton. We compute the $\langle TTT \rangle$ and $\langle TTTT \rangle$ correlation functions arising from the exchange of a particle with spin $s$ and generic mass, and the corresponding signal-to-noise ratios for a cosmic-variance-limited CMB experiment. We show that already with \emph{Planck} data one could improve the theoretical bounds on the amplitude of these primordial templates by an order of magnit…
The cosmic microwave background (CMB) places a variety of model-independent constraints on the strength interactions of the dominant component of dark matter with the Standard Model. Percent-level subcomponents of the dark matter can evade the most stringent CMB bounds by mimicking the behavior of baryons, allowing for larger couplings and novel experimental signatures. However, in this note, we will show that such tightly coupled subcomponents leave a measurable imprint on the CMB that is well approximated by a change to the helium fraction, $Y_{\rm He}$. Using the existing constraint on $Y_{…
We point out two ways to search for low-mass axion dark matter using cosmic microwave background (CMB) polarization measurements. These appear, in particular, to be some of the most promising ways to directly detect fuzzy dark matter. Axion dark matter causes rotation of the polarization of light passing through it. This gives rise to two novel phenomena in the CMB. First, the late-time oscillations of the axion field today cause the CMB polarization to oscillate in phase across the entire sky. Second, the early-time oscillations of the axion field wash out the polarization produced at last-sc…
We demonstrate the feasibility to generate surrogates by Fourier-based methods for an incomplete data set. This is performed for the case of a CMB analysis, where astrophysical foreground emission, mainly present in the Galactic plane, is a major challenge. The shuffling of the Fourier phases for generating surrogates is now enabled by transforming the spherical harmonics into a new set of basis functions that are orthonormal on the cut sky. The results show that non-Gaussianities and hemispherical asymmetries in the CMB as identified in several former investigations, can still be detected eve…
Both WMAP and PLANCK missions reported the extremely Cold Spot (CS) centered at Galactic coordinate ($l=209^{\circ}$, $b=-57^{\circ}$) in CMB map. In this paper, we study the local non-Gaussianity of CS by defining the local Minkowski functions. We find that the third Minkowski function $ν_2$ is quite sensitive to the non-Gaussianity caused by CS. Compared with the random Gaussian simulations, WMAP CS deviates from Gaussianity at more than 99% confident level at the scale $R\sim10^{\circ}$. Meanwhile, we find that cosmic texture provides an excellent explanation for these anomalies related to …
The precision measurements of the cosmic microwave background power spectrum put a strong constraint on the dark matter annihilation cross section since the electromagnetic energy injection by the dark matter annihilation affects the ionization history of the universe. In this paper, we update our previous simulation code for calculating the ionization history with the effect of dark matter annihilation by including Helium interactions and improving the precision of calculations. We give an updated constraint on the annihilation cross section and mass of dark matter using the modified RECFAST …
Measurements of cosmic microwave background (CMB) anisotropies provide strong evidence for the existence of dark matter and dark energy. They can also test its composition, probing the energy density and particle mass of different dark-matter and dark-energy components. CMB data have already shown that ultra-light axions (ULAs) with mass in the range $10^{-32}~{\rm eV} \to 10^{-26}~{\rm eV}$ compose a fraction $< 0.01$ of the cosmological critical density. Here, the sensitivity of a proposed CMB-Stage IV (CMB-S4) experiment (assuming a 1 arcmin beam and $< 1~μK{\rm-arcmin}$ noise levels over a…
In the inhomogeneous Universe, the cosmological conversion of dark photons into ordinary photons (and vice versa) may happen at a great number of resonance redshifts. This alters the CMB observed energy spectrum and degree of small-scale anisotropies. We utilize results from the EAGLE simulation to obtain the conversion probability along random line-of-sights to quantify these effects. We then apply our results to the case where dark photons are sourced by dark matter decay and their high-redshift conversion into ordinary photons modify the global 21 cm signal expected from the cosmic dawn era…
Particles with masses much larger than the inflationary Hubble scale, $H_I$, can be pair-produced non-adiabatically during inflation. Due to their large masses, the produced particles modify the curvature perturbation around their locations. These localized perturbations eventually give rise to localized signatures on the Cosmic Microwave Background (CMB), in particular, pairwise hotspots (PHS). In this work, we show that Convolutional Neural Networks (CNN) provide a powerful tool for identifying PHS on the CMB. While for a given hotspot profile a traditional Matched Filter Analysis is known t…
In view of the current interest in combining different observations to constraint annihilating WIMP dark matter, we examine the relation between the Sommerfeld effect at the recombination epoch and in the galactic halo. By considering an up-to-date collection of interpolations of cosmic rays lepton data (AMS-02 2014, Fermi and PAMELA), as dark matter annihilation signals, we show that current cosmic rays measurements and recent Planck 2015 constraints from CMB anisotropies almost overlap for dark matter masses of the order of few $TeV$, although great theoretical uncertainties afflict cosmic r…
CMB photons travel from the last scattering surface, when the primary CMB has been generated, along the surface of the light cone to us. During their travel, they are affected by many secondary effects such as the integrated Sachs-Wolfe effect and CMB lensing. These CMB secondary effects modify the CMB primary power spectrum adding degeneracies and decreasing the sensibility to primordial parameters. The possibility to reconstruct the primary CMB anisotropies will allow us to have a more direct observable to test the physics of the early universe. We propose to study the imprint of features in…
We study the effects of pre-recombination physics on the Stochastic Gravitational Wave Background (SGWB) anisotropies induced by the propagation of gravitons through the large-scale density perturbations and their cross-correlation with Cosmic Microwave Background (CMB) temperature and E-mode polarization ones. As examples of Early Universe extensions to the $Λ$CDM model, we consider popular models featuring extra relativistic degrees of freedom, a massless non-minimally coupled scalar field, and an Early Dark Energy component. Assuming the detection of a SGWB, we perform a Fisher analysis to …
We study dark matter-helium scattering in the early Universe and its impact on constraints from cosmic microwave background (CMB) anisotropy measurements. We describe possible theoretical frameworks for dark matter-nucleon interactions via a scalar, pseudoscalar, or vector mediator; such interactions give rise to hydrogen and helium scattering, with cross sections that have a power-law dependence on relative velocity. Within these frameworks, we consider three scenarios: dark matter coupling to only neutrons, to only protons, and to neutrons and protons with equal strength. For these various c…
If the physics behind dark energy and/or dark matter violates the parity symmetry assumed in the standard cosmological paradigm, the linear polarization of the cosmic microwave background (CMB) photons can rotate due to their coupling to the dark sector. Recent 3$σ$ hints of this ``cosmic birefringence" in the EB spectrum of the CMB polarization motivates us to pursue new directions to independently validate and characterize the signal. Here, we explore the prospects to probe cosmic birefringence from small-scale fluctuations in the CMB using polarized Sunyaev-Zel'dovich (pSZ) tomography. We f…
Mirror dark matter interacting with ordinary matter via photon-mirror photon kinetic mixing can explain the DAMA, CoGeNT and CRESSTII direct detection experiments. This explanation requires kinetic mixing of strength $ε\sim 10^{-9}$. Such kinetic mixing will have important implications for early Universe cosmology. We calculate the additional relativistic energy density at recombination, $δN_{eff} [CMB]$. We also calculate the effects for big bang nucleosynthesis, $δN_{eff} [BBN]$. Current hints that both $δN_{eff} [CMB]$ and $δN_{eff} [BBN]$ are non-zero and positive can be accommodated withi…
Cosmic microwave background (CMB) constraints on dark matter annihilation are a uniquely powerful tool in the quest to understand the nature of dark matter. Annihilation of dark matter to Standard Model particles between recombination and reionization heats baryons, ionizes neutral hydrogen, and alters the CMB visibility function. Surprisingly, CMB bounds on dark matter annihilation are not expected to improve significantly with the dramatic improvements in sensitivity expected in future cosmological surveys. In this paper, we will present a simple physical description of the origin of the CMB…
In this paper, we explore the impact of Dark Matter-photon interactions on the CMB angular power spectrum. Using the one-year data release of the Planck satellite, we derive an upper bound on the Dark Matter-photon elastic scattering cross section of sigma_{DM-photon} < 8 x 10^{-31} (m_DM/GeV) cm^2 (68% CL) if the cross section is constant and a present-day value of sigma_{DM-photon} < 6 x 10^{-40} (m_DM/GeV) cm^2 (68% CL) if it scales as the temperature squared. For such a limiting cross section, both the B-modes and the TT angular power spectrum are suppressed with respect to LCDM prediction…
The detection of the magnetic type $B$-mode polarization is the main goal of future cosmic microwave background (CMB) experiments. In the standard model, the $B$-mode map is a strongly non-gaussian field due to the lensed component. Besides the two-point correlation function, the other statistics are also very important to dig the information of the polarization map. In this paper, we employ the Minkowski functionals to study the morphological properties of the lensed $B$-mode maps. We find that the deviations from Gaussianity are very significant for both full and partial-sky surveys. As an a…
Axion-like particles are dark matter candidates motivated by the Peccei-Quinn mechanism and also occur in effective field theories where their masses and photon couplings are independent. We estimate the dispersion of circularly polarized photons in a background of oscillating axion-like particles (ALPs) with the standard $g_{aγ}\,a\,F_{μν}\tilde F^{μν}/4$ coupling to photons. This leads to birefringence or rotation of linear polarization by ALP dark matter. Cosmic microwave background (CMB) birefringence limits $Δα\lesssim (1.0)^\circ$ enable us to constrain the axion-photon coupling $g_{aγ} …
The annihilation or decay of Dark Matter (DM) particles could affect the thermal history of the universe and leave an observable signature in Cosmic Microwave Background (CMB) anisotropies. We update constraints on the annihilation rate of DM particles in the smooth cosmological background, using WMAP7 and recent small-scale CMB data. With a systematic analysis based on the Press-Schechter formalism, we also show that DM annihilation in halos at small redshift may explain entirely the reionization patterns observed in the CMB, under reasonable assumptions concerning the concentration and forma…
We perform an improved cosmic microwave background (CMB) analysis to search for dark matter-proton scattering with a momentum-transfer cross section of the form $σ_0 v^n$ for $n=-2$ and $n=-4$. In particular, we present a new and robust prescription for incorporating the relative bulk velocity between the dark matter and baryon fluids into the standard linear Boltzmann calculation. Using an iterative procedure, we self-consistently include the effects of the bulk velocities in a cosmology in which dark matter interacts with baryons. With this prescription, we derive CMB bounds on the cross sec…
Although cosmological observations suggest that the fluctuations of seed fields are almost Gaussian, the possibility of a small deviation of their fields from Gaussianity is widely discussed. Theoretically, there exist numerous inflationary scenarios which predict large and characteristic non-Gaussianities in the primordial perturbations. These model-dependent non-Gaussianities act as sources of the Cosmic Microwave Background (CMB) bispectrum; therefore, the analysis of the CMB bispectrum is very important and attractive in order to clarify the nature of the early Universe. Currently, the imp…
After numerous astronomical and experimental searches, the precise particle nature of dark matter is still unknown. The standard Weakly Interacting Massive Particle(WIMP) dark matter, despite successfully explaining the large-scale features of the universe, has long-standing small-scale issues. The spectral distortion in the Cosmic Microwave Background(CMB) caused by Silk damping in the pre-recombination era allows one to access information on a range of small scales $0.3 \, {\rm Mpc} < k < 10^4 \, \rm Mpc^{-1}$, whose dynamics can be precisely described using linear theory. In this paper, we …
We show that the impact of energy injection by dark matter annihilation on the cosmic microwave background power spectra can be apprehended via a residual likelihood map. By resorting to convolutional neural networks that can fully discover the underlying pattern of the map, we propose a novel way of constraining dark matter annihilation based on the Planck 2018 data. We demonstrate that the trained neural network can efficiently predict the likelihood and accurately place bounds on the annihilation cross-section in a $\textit{model-independent}$ fashion. The machinery will be made public in t…
We study the problem of searching for cosmic string signal patterns in the present high resolution and high sensitivity observations of the Cosmic Microwave Background (CMB). This article discusses a technique capable of recognizing Kaiser-Stebbins effect signatures in total intensity anisotropy maps, and shows that the biggest factor that produces confusion is represented by the acoustic oscillation features of the scale comparable to the size of horizon at recombination. Simulations show that the distribution of null signals for pure Gaussian maps converges to a $χ^2$ distribution, with dete…
Global, symmetry-breaking phase transitions in the early universe can generate scaling seed networks which lead to metric perturbations. The acoustic waves in the photon-baryon plasma sourced by these metric perturbations, when Silk damped, generate spectral distortions of the cosmic microwave background (CMB). In this work, the chemical potential distortion ($μ$) due to scaling seed networks is computed and the accompanying Compton $y$-type distortion is estimated. The specific model of choice is the $O(N)$ nonlinear $σ$-model for $N\gg 1$, but the results remain the same order of magnitude f…
The electrodynamics modified by the Chern-Simons term $\mathcal{L}_{cs}\sim p_μA_ν\tilde F^{μν}$ with a non-vanishing $p_μ$ violates the {\it Charge-Parity-Time Reversal} symmetry (CPT) and rotates the linear polarizations of the propagating {\it Cosmic Microwave Background} (CMB) photons. In this paper we measure the rotation angle $Δα$ by performing a global analysis on the current CMB polarization measurements from the {\it seven-year Wilkinson Microwave Anisotropy Probe} (WMAP7), {\it BOOMERanG 2003} (B03), BICEP and QUaD using a Markov Chain Monte Carlo method. Neglecting the systematic e…
The majoron provides an attractive dark matter candidate, directly associated to the mechanism responsible for spontaneous neutrino mass generation within the standard model framework. Here we update the cosmological and astrophysical constraints on majoron dark matter which come from the Cosmic Microwave Background (CMB) and a variety of X- and gamma-ray observations.
We consider dark matter as singlet fermionic particles which carrying magnetic dipole moment to explore its contribution on the polarization of cosmic microwave background (CMB) photons. We show that Dirac fermionic dark matter has no contribution on the CMB polarization. However, in the case of Majorana dark matter this type of interaction leads to the B-mode polarization in presence of primordial scalar perturbations which is in contrast with standard scenario for the CMB polarization. We numerically calculate the B-mode power spectra and plot $C_l^{BB}$ for different dark matter masses and …
We present measurements of $E_G$, a probe of gravity from large-scale structure, using BOSS LOWZ and CMASS spectroscopic samples, with lensing measurements from SDSS (galaxy lensing) and Planck (CMB lensing). Using SDSS lensing and the BOSS LOWZ sample, we measure $\langle{E_G}\rangle=0.40^{+0.05}_{-0.04}$ (stat), $\pm 0.026$ (systematic), consistent with the predicted value from the Planck $Λ$CDM model, $E_G=0.46$. Using CMB lensing, we measure $\langle{E_G}\rangle=0.46^{+0.08}_{-0.09}$ (stat) for LOWZ (statistically consistent with galaxy lensing and Planck predictions) and $\langle{E_G}\ran…
We compute the impact of the running of higher order density correlation functions on the two point functions of CMB spectral distortions (SD). We show that having some levels of running enhances all of the SDs by few orders of magnitude which might make them easier to detect. Taking a reasonable range for $ |n_{f_{NL}} |\lesssim 1.1$ and with $f_{NL} = 5$ we show that for PIXIE like experiment, the signal to noise ratio, $(S/N)_{i}$, enhances to $\lesssim 4000$ and $\lesssim 10$ for $μT$ and $yT$ toward the upper limit of $n_{f_{NL}}$. In addition, assuming $ |n_{τ_{NL}}|< 1$ and $τ_{NL} = 10…
Probing the Cosmological Principle with CMB lensing and cosmic shear
University of the Western Cape（西开普敦大学）；National Institute for Theoretical & Computational Sciences（理论与计算科学国家研究所）；Laboratoire Univers et Particules de Montpellier, CNRS & Université de Montpellier（蒙彼利埃宇宙与粒子实验室，法国国家科学研究中心与蒙彼利埃大学）；Queen Mary University of London（伦敦玛丽女王大学）；Université de Genève（日内瓦大学）
The injection of secondary particles produced by Dark Matter (DM) annihilation around redshift 1000 would inevitably affect the process of recombination, leaving an imprint on Cosmic Microwave Background (CMB) anisotropies and polarization. We show that the most recent CMB measurements provided by the WMAP satellite mission place interesting constraints on DM self-annihilation rates, especially for models that exhibit a large Sommerfeld enhancement of the annihilation cross-section, as recently proposed to fit the PAMELA and ATIC results. Furthermore, we argue that upcoming CMB experiments suc…
We propose a simple technique to detect any anisotropic expansion stage in the history of the universe starting from the inflationary stage to the surface of last scattering from the CMBR data. We use the property that any anisotropic expansion in the universe would deform the shapes of the primordial density perturbations and this deformation can be detected in a shape analysis of superhorizon fluctuations in CMBR. Using this analysis we obtain the constraint on any previous anisotropic expansion of the universe to be less than about 35%.
