Ever refined cosmological measurements have established the $Λ$CDM concordance model, with the key cosmological parameters being determined to percent-level precision today. This allows us to make explicit predictions for the spectral distortions of the cosmic microwave background (CMB) created by various processes occurring in the early Universe. Here, we summarize all guaranteed CMB distortions and assess their total uncertainty within $Λ$CDM. We also compare simple methods for approximating them, highlighting some of the subtle aspects when it comes to interpreting future distortion measurements. Under simplified assumptions, we briefly study how well a PIXIE-like experiment may measure the main distortion parameters (i.e., $μ$ and $y$). Next generation CMB spectrometers are expected to detect the distortion caused by reionization and structure formation at extremely high significance. They will also be able to constrain the small-scale power spectrum through the associated $μ$-distortion, improving limits on running of the spectral index. Distortions from the recombination era, adiabatic cooling of matter relative to the CMB and dark matter annihilation require a higher sensitivity than PIXIE in its current design. The crucial next step is an improved modeling of foregrounds and instrumental aspects, as we briefly discuss here.
It has recently been claimed that measurements of the baryonic Tully-Fisher relation (BTFR), a power-law relationship between the observed baryonic masses and outer rotation velocities of galaxies, support the predictions of modified Newtonian dynamics for the slope and scatter in the relation, while challenging the cold dark matter (CDM) paradigm. We investigate these claims, and find that: 1) the scatter in the data used to determine the BTFR is in conflict with observational uncertainties on the data; 2) these data do not make strong distinctions regarding the best-fit BTFR parameters; 3) t…
Although both early and late-time modifications of the $Λ$CDM model have been proposed to address the Hubble tension, compelling arguments suggest that for a solution to be successful it needs to modify the expansion history of the universe prior to recombination. This greatly increases the importance of precise CMB observations, and in this letter we make the argument for CMB spectral distortions, highlighting their potential role in constraining models that introduce significant shifts in the standard $Λ$CDM parameters, such as the scalar spectral index, in attempt to solve the Hubble tensio…
Modified gravity and massive neutrino cosmologies are two of the most interesting scenarios that have been recently explored to account for possible observational deviations from the concordance $Λ$-cold dark matter ($Λ$CDM) model. In this context, we investigated the large-scale structure of the Universe by exploiting the \dustp simulations that implement, simultaneously, the effects of $f(R)$ gravity and massive neutrinos. To study the possibility of breaking the degeneracy between these two effects, we analysed the redshift-space distortions in the clustering of dark matter haloes at differ…
Linear Growth of Matter Perturbations Probed by Redshift-Space Distortions in Interacting $Λ(t)$CDM Cosmologies
University of Science and Technology of China（中国科学技术大学）；Universidade Estadual Paulista (UNESP)（圣保罗州立大学）；Universidade Federal do Rio Grande do Sul（南里奥格兰德联邦大学）；Instituto Nacional de Pesquisas Espaciais（国家空间研究所）；Universidade de São Paulo（圣保罗大学）
In multiple inflation scenario having two inflations with an intermediate matter-dominated phase, the power spectrum is estimated to be enhanced on scales smaller than the horizon size at the beginning of the second inflation, $k > k_{\rm b}$. We require $k_{\rm b} > 10 {\rm Mpc}^{-1}$ to make sure that the enhanced power spectrum is consistent with large scale observation of cosmic microwave background (CMB). We consider the CMB spectral distortions generated by the dissipation of acoustic waves to constrain the power spectrum. The $μ$-distortion value can be $10$ times larger than the expect…
We investigate the spatial properties of the large scale structure (LSS) of the Universe in the framework of coupled dark energy (cDE) cosmologies. Using the public halo catalogues from the CoDECS simulations -- the largest set of N-body experiments to date for such cosmological scenarios -- we estimate the clustering and bias functions of cold dark matter (CDM) haloes, both in real- and redshift-space. Moreover, we investigate the effects of the dark energy (DE) coupling on the geometric and dynamic redshift-space distortions, quantifying the difference with respect to the concordance LambdaC…
We present an impact of coupling between dark matter and a scalar field, which might be responsible for dark energy, on measurements of redshift-space distortions. We point out that, in the presence of conformal and/or disformal coupling, linearized continuity and Euler equations for total matter fluid significantly deviate from the standard ones even in the sub-horizon scales. In such a case, a peculiar velocity of total matter field is determined not only by a logarithmic time derivative of its density perturbation but also by density perturbations for both dark matter and baryon, leading to…
We propose a new consistency test for the $Λ$CDM cosmology using baryonic acoustic oscillations (BAO) and redshift space distortion (RSD) measurements from galaxy redshift surveys. Specifically, we determine the peak position of $fσ_8(z)$ in redshift $z$ offered by a RSD measurement, and compare it to the one predicted by the BAO observables assuming a flat $Λ$CDM cosmology. We demonstrate this new test using the simulated data for the DESI galaxy survey, and argue that this test complements those using the background observables alone, and is less subject to systematics in the RSD analysis, c…
In this paper, a specific family of $f(R)$ models that can produce the $Λ$CDM background expansion history is constrained by using the currently available geometric and dynamic probes. The scale dependence of the growth rate $f(z,k)$ in this specific family of $f(R)$ model is shown. Therefore to eliminate the scale dependence of $fσ_8(z)$ in theory, which usually is defined as the product of $f(z,k)$ and $σ_8(z)$, we define $fσ_8(z)=dσ_8(z)/d\ln a$ which is obviously scale independent and reproduces the conventional definition in the standard $Λ$CDM cosmology. In doing so, under the assumption…
Although the large-scale perturbations beyond a finite-volume survey region are not direct observables, these affect measurements of clustering statistics of small-scale (sub-survey) perturbations in the large-scale structure, compared with the ensemble average, via the mode-coupling effect. In this paper we show that the large-scale tides induced by scalar perturbations cause apparent anisotropic distortions in the redshift-space power spectrum of galaxies in a way depending on an alignment between the tides, the wavevector of small-scale modes and the line-of-sight direction. Using the pertu…
Within the $Λ$CDM model, measurements from recent Cosmic Microwave Background (CMB) and weak lensing (WL) surveys have uncovered a $\sim 3σ$ disagreement in the inferred value of the parameter $S_8 \equiv σ_8\sqrt{Ω_m/0.3}$, quantifying the amplitude of late-time matter fluctuations. Before questioning whether the $S_8$ discrepancy calls for new physics, it is important to assess the view of measurements other than CMB and WL ones on the discrepancy. Here, we examine the role of measurements of the growth rate $f(z)$ in arbitrating the $S_8$ discrepancy, considering measurements of $fσ_8(z)$ f…
Measurements of cosmic microwave background spectral distortions have profound implications for our understanding of physical processes taking place over a vast window in cosmological history. Foreground contamination is unavoidable in such measurements and detailed signal-foreground separation will be necessary to extract cosmological science. We present MCMC-based spectral distortion detection forecasts in the presence of Galactic and extragalactic foregrounds for a range of possible experimental configurations, focusing on the Primordial Inflation Explorer (PIXIE) as a fiducial concept. We …
In this work we consider CMB spectral distortions as a probe of dark matter microphysics in the early universe. We demonstrate that future experiments such as PRISM have the potential to distinguish between scenarios which offer solutions to the small-scale problems of CDM cosmology.
One of the most prominent challenges to the standard Lambda cold dark matter ($Λ$CDM) cosmology is the tension between the structure growth parameter $S_8$ constrained by the cosmic microwave background (CMB) data and the smaller one suggested by the cosmic shear data. Recent studies show that, for $Λ$CDM cosmology, redshift-space distortion (RSD) data also prefers a smaller $S_8$ that is $\sim 2$-$3σ$ lower than the CMB value, but the result is sensitive to the cosmological model. In the present work we update the RSD constraint on $S_8$ with the most up-to-date RSD data set where the correla…
The dissipation of small-scale perturbations in the early universe produces a distortion in the blackbody spectrum of cosmic microwave background photons. In this work, we propose to use these distortions as a probe of the microphysics of dark matter on scales $1\,\textrm{Mpc}^{-1}\lesssim k \lesssim 10^{4}\,\textrm{Mpc}^{-1}$. We consider in particular models in which the dark matter is kinetically coupled to either neutrinos or photons until shortly before recombination, and compute the photon heating rate and the resultant $μ$-distortion in both cases. We show that the $μ$-parameter is gene…
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 …
Cosmological Constraints on the Generalized Uncertainty Principle from Redshift-Space Distortions
Durban University of Technology（德班理工大学）；North-West University（西北大学）；Universidad Catòlica del Norte（北天主教大学）；National Institute for Theoretical and Computational Sciences (NITheCS)（国家理论与计算科学研究所）
The simplest theory describing large-scale redshift-space distortions (RSD), based on linear theory and distant galaxies, depends on the growth of cosmological structure, suggesting that strong tests of General Relativity can be constructed from galaxy surveys. As data sets become larger and the expected constraints more precise, the extent to which the RSD follow the simple theory needs to be assessed in order that we do not introduce systematic errors into the tests by introducing inaccurate simplifying assumptions. We study the impact of the sample geometry, non-linear processes, and biases…
A Bayesian statistical analysis using redshift space distortions data is performed to test a model of Symmetric Teleparallel Gravity where gravity is non-metrical. The cosmological background mimics a $Λ$CDM evolution but differences arise in the perturbations. The linear matter fluctuations are numerically evolved and the study of the growth rate of structures is analysed in this cosmological setting. The best fit parameters reveal that the $σ_8$ tension between Planck and Large Scale Structure data can be alleviated within this framework.
The Evolutionary Map of the Universe (EMU) is an all-sky survey in radio-continuum which uses the Australian SKA Pathfinder (ASKAP). Using galaxy angular power spectrum and the integrated Sachs-Wolfe effect, we study the potential of EMU to constrain models beyond $Λ$CDM (i.e., local primordial non-Gaussianity, dynamical dark energy, spatial curvature and deviations from general relativity), for different design sensitivities. We also include a multi-tracer analysis, distinguishing between star-forming galaxies and galaxies with an active galactic nucleus, to further improve EMU's potential. W…
We use the emulation framework CosmoPower to construct and publicly release neural network emulators of cosmological observables, including the Cosmic Microwave Background (CMB) temperature and polarization power spectra, matter power spectrum, distance-redshift relation, baryon acoustic oscillation (BAO) and redshift-space distortion (RSD) observables, and derived parameters. We train our emulators on Einstein-Boltzmann calculations obtained with high-precision numerical convergence settings, for a wide range of cosmological models including $Λ$CDM, $w$CDM, $Λ$CDM+$N_\mathrm{eff}$, and $Λ$CDM…
We study observational constraints on the non-metricity $f(Q)$-gravity which reproduces an exact $Λ$CDM background expansion history while modifying the evolution of linear perturbations. To this purpose we use Cosmic Microwave Background (CMB) radiation, baryonic acoustic oscillations (BAO), redshift-space distortions (RSD), supernovae type Ia (SNIa), galaxy clustering (GC) and weak gravitational lensing (WL) measurements. We set stringent constraints on the parameter of the model controlling the modifications to the gravitational interaction at linear perturbation level. We find the model to…
Measurements of the cosmic microwave background (CMB) spectral distortions (SDs) will open a new window on the very early universe, providing new information complementary to that gathered from CMB temperature and polarization anisotropies. In this paper, we study their synergy as a function of the characteristics of the considered experiments. In particular, we examine a wide range of sensitivities for possible SD measurements, spanning from FIRAS up to noise levels 1000 times better than PIXIE, and study their constraining power when combined with current or future CMB anisotropy experiments…
The low statistical errors on cosmological parameters promised by future galaxy surveys will only be realised with the development of new, fast, analysis methods that reduce potential systematic problems to low levels. We present an efficient method for measuring the evolution of the growth of structure using Redshift Space Distortions (RSD), that removes the need to make measurements in redshift shells. We provide sets of galaxy-weights that cover a wide range in redshift, but are optimised to provide differential information about cosmological evolution. These are derived to optimally measur…
We perform parametric tests of the consistency of the standard $w$CDM model in the framework of general relativity by carefully separating information between the geometry and growth of structure. We replace each late-universe parameter that describes the behavior of dark energy with two parameters: one describing geometrical information in cosmological probes, and the other controlling the growth of structure. We use data from all principal cosmological probes: of these, Type Ia supernovae, baryon acoustic oscillations, and the peak locations in the cosmic microwave background angular power s…
The Lambda-CDM cosmological model is succesful at reproducing various independent sets of observations concerning the large-scale Universe. This model is however currently, and actually in principle, unable to predict the gravitational field of a galaxy from it observed baryons alone. Indeed the gravitational field should depend on the relative contribution of the particle dark matter distribution to the baryonic one, itself depending on the individual assembly history and environment of the galaxy, including a lot of complex feedback mechanisms. However, for the last thirty years, Milgrom's f…
Recent anomalies found in cosmological datasets such as the low multipoles of the Cosmic Microwave Background or the low redshift amplitude and growth of clustering measured by e.g., abundance of galaxy clusters and redshift space distortions in galaxy surveys, have motivated explorations of models beyond standard $Λ$CDM. Of particular interest are models where general relativity (GR) is modified on large cosmological scales. Here we consider deviations from $Λ$CDM+GR within the context of Horndeski gravity, which is the most general theory of gravity with second derivatives in the equations o…
Weak galaxy lensing surveys have consistently reported a lower amplitude for the matter fluctuation spectrum, as measured by the $S_8$ parameter, than expected in the $Λ{\rm CDM}$ cosmology favoured by $Planck$. However, the expansion history follows the predictions of the $Planck$ $Λ{\rm CDM}$ cosmology to high accuracy, as do measurements of lensing of the cosmic microwave background anisotropies. Redshift space distortion measurements also appear to be consistent with $Planck$ $Λ{\rm CDM}$. In this paper, we argue that these observations can be reconciled with the $Planck$ $Λ{\rm CDM}$ cosm…
We investigate an interacting dark sector scenario in which the vacuum energy is free to interact with cold dark matter (CDM), which itself is assumed to cluster under the sole action of gravity, i.e. it is in free fall (geodesic), as in $Λ$CDM. The interaction is characterised by a dimensionless coupling $q_{\rm V}$ that we constrain using cosmic microwave background data from the Planck 2015 data release, along with baryon acoustic oscillation, redshift space distortion and Type Ia supernova measurements. We present the full linear perturbation theory of this interacting scenario and use MCM…
We study the cosmology of a specific class of nonlocal model of modified gravity, the so-called Deser-Woodard (DW) model, modifying the Einstein-Hilbert action by a term $\sim R f(\Box^{-1}R)$, where $f$ is a free function. Choosing $f$ so as to reproduce the $Λ{\rm CDM}$ cosmological background expansion history within the nonlocal model, we implement the model in a cosmological linear Einstein--Boltzmann solver and study the deviations to GR the model induces in the scalar and tensor perturbations. We observe that the DW nonlocal model describes a modified propagation for the gravitational w…
Baryon acoustic oscillations (BAO) provide a robust standard ruler, and can be used to constrain the expansion history of the Universe at low redshift. Standard BAO analyses return a model-independent measurement of the expansion rate and the comoving angular diameter distance as function of redshift, normalized by the sound horizon at radiation drag. However, this methodology relies on anisotropic distance distortions of a fixed, pre-computed template (obtained in a given fiducial cosmology) in order to fit the observations. Therefore, it may be possible that extensions to the consensus $Λ$CD…
In a recent article, Kleidis and Spyrou (2015) proposed that both dark matter (DM) and dark energy (DE) can be treated as a single component, if accommodated in the context of a polytropic DM fluid with thermodynamical content. Depending only on the polytropic exponent, $-0.103 < Γ\leq 0$, this unified DM model reproduces to high accuracy the distance measurements performed with the aid of the supernovae Type Ia (SNe Ia) standard candles, without suffering either from the age or from the coincidence problem. To demonstrate also its compatibility with current observational data concerning struc…
About two-thirds of present-day, large galaxies are spirals such as the Milky Way or Andromeda, but the way their thin rotating disks formed remains uncertain. Observations have revealed that half of their progenitors, six billion years ago, had peculiar morphologies and/or kinematics, which exclude them from the Hubble sequence. Major mergers, i.e., fusions between galaxies of similar mass, are found to be the likeliest driver for such strong peculiarities. However, thin disks are fragile and easily destroyed by such violent collisions, which creates a critical tension between the observed fr…
We propose a novel model in the framework of $f(Q)$ gravity, which is a gravitational modification class arising from the incorporation of non-metricity. The model has General Relativity as a particular limit, it has the same number of free parameters to those of $Λ$CDM, however at a cosmological framework it gives rise to a scenario that does not have $Λ$CDM as a limit. Nevertheless, confrontation with observations at both background and perturbation levels, namely with Supernovae type Ia (SNIa), Baryonic Acoustic Oscillations (BAO), cosmic chronometers (CC), and Redshift Space Distortion (RS…
Within the effective field theory approach to cosmic acceleration, the background expansion can be specified separately from the gravitational modifications. We explore the impact of modified gravity in a background different from a cosmological constant plus cold dark matter ($Λ$CDM) on the stability and cosmological observables, including covariance between gravity and expansion parameters. In No Slip Gravity the more general background allows more gravitational freedom, including both positive and negative Planck mass running. We examine the effects on cosmic structure growth, as well as sh…
Peering Beyond the Veil of Last Scattering: A View of the Universe with CMB Spectral Distortions
Massachusetts Institute of Technology（麻省理工学院）；Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale（巴黎萨克雷大学，法国国家科学研究中心，天体物理研究所）；Boston University（波士顿大学）；Sapienza Universitá di Roma（罗马第一大学）；INFN, Sezione di Roma（意大利国家核物理研究所，罗马分部）；University of Manchester（曼彻斯特大学）；Instituto de Física de Cantabria (IFCA), CSIC-Univ. de Cantabria（坎塔布里亚物理研究所，西班牙高等科学研究委员会-坎塔布里亚大学）；Jodrell Bank Centre for Astrophysics（乔德雷尔银行天体物理学中心）；University of Oxford（牛津大学）；University of Sheffield（谢菲尔德大学）；Leibniz University Hannover（汉诺威莱布尼茨大学）；Max Planck Institute for G（马克斯·普朗克G研究所）
In this paper, we study a model which is composed by the cosmological constant and dark matter with nonzero equation of state parameter, which could be called as $Λ$wDM. In the synchronous gauge, we obtain the perturbation equations of dark matter, and deduce the evolution equations of growth factor about the dark matter and baryons. Based on the Markov Chain Monte Carlo method, we constrain this model by the recently available cosmic observations which include cosmic microwave background radiation, baryon acoustic oscillation, type Ia supernovae, and $fσ_8(z)$ data points from redshift-space …
We place observational constraints on the Galileon ghost condensate model, a dark energy proposal in cubic-order Horndeski theories consistent with the gravitational-wave event GW170817. The model extends the covariant Galileon by taking an additional higher-order field derivative $X^2$ into account. This allows for the dark energy equation of state $w_{\rm DE}$ to access the region $-2<w_{\rm DE}<-1$ without ghosts. Indeed, this peculiar evolution of $w_{\rm DE}$ is favored over that of the cosmological constant $Λ$ from the joint data analysis of cosmic microwave background (CMB) radiation, …
We measure the growth rate and its evolution using the anisotropic clustering of the extended Baryon Oscillation Spectroscopic Survey (eBOSS) Data Release 14 (DR14) quasar sample, which includes $148\,659$ quasars covering the wide redshift range of $0.8 < z < 2.2$ and a sky area of $2112.90$ $\rm deg^2$. To optimise measurements we deploy a redshift-dependent weighting scheme, which allows us to avoid binning, and perform the data analysis consistently including the redshift evolution across the sample. We perform the analysis in Fourier space, and use the redshift evolving power spectrum mul…
Cosmic Microwave Background (CMB) experiments, such as WMAP and Planck, measure intensity anisotropies and build maps using a \emph{linearized} formula for relating them to the temperature blackbody fluctuations. However such a procedure also generates a signal in the maps in the form of y-type distortions, and thus degenerate with the thermal SZ (tSZ) effect. These are small effects that arise at second-order in the temperature fluctuations not from primordial physics but from such a limitation of the map-making procedure. They constitute a contaminant for measurements of: our peculiar veloci…
Cosmic Microwave Background (CMB) experiments, such as WMAP and Planck, measure intensity anisotropies and build maps using a linearized formula for relating them to the temperature blackbody fluctuations. However, this procedure also generates a signal in the maps in the form of y-type distortions which is degenerate with the thermal Sunyaev Zel'dovich (tSZ) effect. These are small effects that arise at second-order in the temperature fluctuations not from primordial physics but from such a limitation of the map-making procedure. They constitute a contaminant for measurements of: our peculiar…
We propose the implementation of an imaging telescope in combination with an inter-frequency calibrator to measure the spectral shape of the microwave sky by exploiting the differences in the sky intensity between multiple pairs of frequency channels. By jointly sampling the cosmological and foreground parameters in a Bayesian framework for $600$ instrument configurations, we determine the minimum calibration accuracy required in order to obtain measurements of spectral distortions and simultaneously measure spectral and spatial fluctuations of the CMB. We demonstrate the feasibility of this t…
We perform a general test of the $Λ{\rm CDM}$ and $w {\rm CDM}$ cosmological models by comparing constraints on the geometry of the expansion history to those on the growth of structure. Specifically, we split the total matter energy density, $Ω_M$, and (for $w {\rm CDM}$) dark energy equation of state, $w$, into two parameters each: one that captures the geometry, and another that captures the growth. We constrain our split models using current cosmological data, including type Ia supernovae, baryon acoustic oscillations, redshift space distortions, gravitational lensing, and cosmic microwave…
A recent analysis of the Supernova Ia data claims a 'marginal' ($\sim3σ$) evidence for a cosmic acceleration. This result has been complemented with a non-accelerating $R_{h}=ct$ cosmology, which was presented as a valid alternative to the $Λ$CDM model. In this paper, we use the same analysis to show that a non-marginal evidence for acceleration is actually found. We compare the standard Friedmann models to the $R_{h}=ct$ cosmology by complementing SN Ia data with the Baryon Acoustic Oscillations, Gamma Ray Bursts and Observational Hubble datasets. We also study the power-law model which is a …
We combine model-independent reconstructions of the expansion history from the latest Pantheon supernovae distance modulus compilation and measurements from baryon acoustic oscillation to test some important aspects of the concordance model of cosmology namely the FLRW metric and flatness of spatial curvature. We then use the reconstructed expansion histories to fit growth measurement from redshift-space distortion and obtain strong constraints on $(Ω_\mathrm{m},γ,σ_8)$ in a model independent manner. Our results show consistency with a spatially flat FLRW Universe with general relativity to go…
One problem of the $Λ$CDM model is the tension between the $S_8$ found in Cosmic Microwave Background (CMB) experiments and the smaller one obtained from large-scale observations in the late Universe. The $σ_8$ quantifies the relatively high level of clustering. Bayesian Analysis of the Redshift Space Distortion (RSD) selected data set yields: $S_8 = 0.700^{+0.038}_{-0.037}$. The fit has $3σ$ tension with the Planck 2018 results. With Gaussian processes method a model-independent reconstructions of the growth history of matter in-homogeneity is studied. The fit yields $S_8 = 0.707^{+0.085}_{-0…
Marked correlation functions, which are sensitive to the clustering of galaxies in different environments, have been proposed as constraints on modified gravity models. We present measurements of the marked correlation functions of galaxies in redshift space using 361,761 LOWZ ($z_{\rm eff} = 0.32$) galaxies from the Sloan Digital Sky Survey III (SDSS III) Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12 (DR12) and compare them to $Λ$CDM+General Relativity simulations. We apply mass cuts to find the best match between the redshift space autocorrelation function of subhaloes in th…
The observed properties of high redshift galaxies depend on the underlying foreground distribution of large scale structure, which distorts their intrinsic properties via gravitational lensing. We focus on the regime where the dominant contribution originates from a single lens and examine the statistics of gravitational lensing by a population of virialized and non-virialized structures using sub-mm galaxies at z ~ 2.6 and Lyman-break galaxies at redshifts z ~ 6 - 15 as the background sources. We quantify the effect of lensing on the luminosity function of the high redshift sources, focusing …
