How does a smooth cosmic distance ladder emerge from observations made from a single location in a lumpy Universe? Distances to Type Ia supernovae in the Hubble flow are anchored on local distance measurements to sources that are very nearby. We described how this configuration could be built in a perturbed universe where lumpiness is described as small perturbations on top of a flat Friedmann-Lemaıtre Robertson-Walker spacetime. We show that there is a non-negligible modification (about 11\%) to the background Friedmann-Lemaıtre Robertson-Walker area distance due to the presence of inhomogeneities in the immediate neighbourhood of an observer. We find that the modification is sourced by the electric part of the Weyl tensor indicating a tidal deformation of the local spacetime of the observer. We show in detail how it could impact the calibration of the Type Ia supernova absolute magnitude in the Hubble flow. We show that it could potentially resolve the Type Ia supernova absolute magnitude and Hubble tensions simultaneously without the need for early or late dark energy.
There are many inflationary models that allow the formation of the large-scale structure of the observable universe. The non-gaussianity parameter $f_{NL}$ is a useful tool to discriminate among these cosmological models when comparing the theoretical predictions with the satellite survey results like those from WMAP and Planck. The goal of this proceeding contribution is to review the moment transport equations methodology and the subsequent calculation of the $f_{NL}$ parameter.
The model of holographic dark energy in which dark energy interacts with dark matter is investigated in this paper. In particular, we consider the interacting holographic dark energy model in the context of a perturbed universe, which was never investigated in the literature. To avoid the large-scale instability problem in the interacting dark energy cosmology, we employ the generalized version of the parameterized post-Friedmann approach to treat the dark energy perturbations in the model. We use the current observational data to constrain the model. Since the cosmological perturbations are c…
In this manuscript, it is shown that the Pioneer anomaly is the local evidence for an expanding universe. In other words, its value is a direct measure of the Hubble constant while its sign shows the expanding behavior of the dynamics of the universe. This analysis is obtained by studying the radial geodesic deviation of the light rays in the perturbed Friedmann-Robertson-Walker metric in the Newtonian gauge.
The measurements of the Hubble constant reveal a tension between high-redshift (CMB) and low-redshift (distance ladder) constraints. So far neither observational systematics nor new physics has been successfully implemented to explain this tension away. This paper present a new solution to the Hubble constant problem. The solution is based on the Simsilun simulation (relativistic simulation of the large scale structure of the Universe) with the ray-tracing algorithm implemented. The initial conditions for the Simsilun simulation were set up as perturbations around the $Λ$CDM model. However, un…
When the gravitational lensing of the large-scale structure is calculated from a cosmological model a few assumptions enter: $(i)$ one assumes that the photons follow unperturbed background geodesics, which is usually referred to as the Born-approximation, $(ii)$ the lenses move slowly, $(iii)$ the source-redshift distribution is evaluated relative to the background quantities and $(iv)$ the lensing effect is linear in the gravitational potential. Even though these approximations are small individually they could sum up, especially since they include local effects such as the Sachs-Wolfe and p…
Loop quantum cosmology is a tentative approach to model the universe down to the Planck era where quantum gravity settings are needed. The quantization of the universe as a dynamical space-time is inspired by Loop Quantum Gravity ideas. In addition, loop quantum cosmology could bridge contact with astronomical observations, and thus potentially investigate quantum cosmology modellings in the light of observations. To do so however, modelling both the background evolution and its perturbations is needed. The latter describe cosmic inhomogeneities that are the main cosmological observables. In t…
We exploit cosmological-model independent measurements of the expansion history of the Universe to provide a cosmic distance ladder. These are supernovae type Ia used as standard candles (at redshift between 0.01 and 1.3) and baryon acoustic oscillations (at redshifts between 0.1 and 0.8) as standard rulers. We calibrate (anchor) the ladder in two ways: first using the local $H_0$ value as an anchor at $z$ = 0 (effectively calibrating the standard candles) and secondly using the cosmic microwave background-inferred sound-horizon scale as an anchor (giving the standard ruler length) as an inver…
We study the structure and evolution of dark matter halos from z = 300 to z = 6 for two cosmological N-body simulation initialization techniques. While the second order Lagrangian perturbation theory (2LPT) and the Zel'dovich approximation (ZA) both produce accurate present day halo mass functions, earlier collapse of dense regions in 2LPT can result in larger mass halos at high redshift. We explore the differences in dark matter halo mass and concentration due to initialization method through three 2LPT and three ZA initialized cosmological simulations. We find that 2LPT induces more rapid ha…
Over the last few years, low- and high-redshift observations set off a tension in the measurement of the present-day expansion rate, $H_0$. Adding to the riddle, observational data from the Planck mission point to a $3.4σ$ evidence for a closed universe, further challenging the $Λ$CDM concordance model of cosmology. Recently, a direct-observational test has been proposed to discriminate effects of the spatial curvature in the cosmological model. The test is based on the fundamental distance--flux--redshift relation of the luminosity distance modulus, $Δμ$. We reexamine the outcomes of this tes…
Context. The precise determination of the present-day expansion rate of the Universe, expressed through the Hubble constant $H_0$, is one of the most pressing challenges in modern cosmology. Assuming flat $Λ$CDM, $H_0$ inference at high redshift using cosmic-microwave-background data from Planck disagrees at the 4.4$σ$ level with measurements based on the local distance ladder made up of parallaxes, Cepheids and Type Ia supernovae (SNe Ia), often referred to as "Hubble tension". Independent, cosmological-model-insensitive ways to infer $H_0$ are of critical importance. Aims. We apply an invers…
Model-independent late-universe measurements of $H_0$ and $Ω_K$ with the parametrization based on cosmic age-improved inverse distance ladder
College of Sciences, Northeastern University（东北大学理学院）；Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；School of Physical Science and Technology, Ningbo University（宁波大学物理科学与技术学院）
Future precision measurements of CMB polarizations can shed new light on the problem so called Hubble tension. The Hubble tension comes from the difference of the evolutions of the Hubble parameter which are determined with two different distance ladders. The standard distance ladder with the observation of Cepheid variables and type Ia supernovae gives larger values of the Hubble constant, and the inverse distance ladder with the observation of the baryon acoustic oscillations both in the CMB and in the clustering of galaxies gives smaller values of the Hubble constant. These different evolut…
We study the Hubble parameter $H(z)$ in perturbed Friedmann universe and obtain an expression of the perturbed Hubble parameter $H(z,\textbf{n})$. We derive the Hubble parameter power spectrum by using the initial spectrum during inflation and the Bardeen transfer function. We obtain a semi-analytical expression in the case of cold dark matter (CDM) universe. Similar with luminosity distance, the Hubble parameter spectrum is suggested to be an useful observational tool to determine some cosmological parameters. In addition, we show that the Hubble parameter power spectrum could be used to chec…
The observed tension ($\sim 9\%$ difference) between the local distance ladder measurement of the Hubble constant, $H_0$, and its value inferred from the cosmic microwave background (CMB) could hint at new, exotic, cosmological physics. We test the impact of the assumption about the expansion history of the universe ($0.01<z<2.3$) on the local distance ladder estimate of $H_0$. In the fiducial analysis, the Hubble flow Type Ia supernova (SN~Ia) sample is truncated to $z < 0.15$ and the deceleration parameter ($q_0$) fixed to -0.55. We create realistic simulations of the calibrator and Pantheon…
The evolution of cosmic perturbations in a two-component ultralight axionic universe is investigated. We present the first spectral computation of perturbations in multi-component universes. A particular case composed of light extreme axions and free massive particles offers a possibility for the formation of very high-redshift massive galaxies, which are typically required to host massive early quasars. Our computation retains the information of perturbed velocities for individual axion components, opening a new avenue for setting up initial conditions for future axion dark matter simulations…
Measurements of the Hubble parameter from the distance ladder are in tension with indirect measurements based on the cosmic microwave background (CMB) data and the inverse distance ladder measurements at 3-4 $σ$ level. We consider phenomenological modification to the timing and width of the recombination process and show that they can significantly affect this tension. This possibility is appealing, because such modification affects both the distance to the last scattering surface and the calibration of the baryon acoustic oscillations (BAO) ruler. Moreover, because only a very small fraction …
It is shown that the decomposition theorems of York, Stewart and Walker for symmetric spatial second-rank tensors, such as the perturbed metric tensor and perturbed Ricci tensor, and the spatial fluid velocity vector imply that, for open, flat or closed Friedmann-Lemaitre-Robertson-Walker universes, there are exactly two, unique, independent gauge-invariant quantities which describe the true, physical perturbations to the energy density and particle number density. Using these two new quantities, evolution equations for cosmological density perturbations and for entropy perturbations, adapted …
Ningbo University（宁波大学）；Institute of Theoretical Physics, Chinese Academy of Sciences (CAS)（中国科学院理论物理研究所）；Asia Pacific Center for Theoretical Physics (APCTP)（亚太理论物理中心）
The three rung distance ladder, which calibrates Type Ia supernovae through stellar distances linked to geometric measurements, provides the highest precision direct measurement of the Hubble constant. In light of the Hubble tension, it is important to test the individual components of the distance ladder. For this purpose, we report a measurement of the Hubble constant from 35 extragalactic Cepheid hosts measured by the SH0ES team, using their distances and redshifts at cz < 3300 km /s , instead of any, more distant Type Ia supernovae, to measure the Hubble flow. The Cepheid distances are cal…
A covariant description of quantum matter fields in the early universe underpins models for the origin of species, e.g. baryogenesis and dark matter production. In nearly all cases the relevant cosmological observables are computed in a general approximation, via the standard irreducible representations found in the operator formalism of particle physics, where intricacies related to a renormalized stress-energy tensor in a non-stationary spacetime are ignored. Models of the early universe also include a dense environment of quantum fields where far-from-equilibrium interactions manifest expre…
Revisiting model-independent constraints on spatial curvature and cosmic ladders calibration: updated and forecast analyses
Università di Roma Tor Vergata（罗马托尔维加塔大学）；INFN, Sezione di Roma 2（意大利国家核物理研究所罗马第二分部）；Università di Roma La Sapienza（罗马第一大学）；Universitat de Barcelona (UB)（巴塞罗那大学）；Institut de Ciències del Cosmos (ICCUB)（宇宙科学研究所）
The Hubble constant $H_{0}$ and matter density $Ω_{m}$ of the Universe are measured using the latest $γ$-ray attenuation results from Fermi-LAT and Cherenkov telescopes. This methodology is based upon the fact that the extragalactic background light supplies opacity for very high energy photons via photon-photon interaction. The amount of $γ$-ray attenuation along the line of sight depends on the expansion rate and matter content of the Universe. This novel strategy results in a value of $H_{0}=67.4_{-6.2}^{+6.0}$~km~s$^{-1}$~Mpc$^{-1}$ and $Ω_{m}=0.14_{-0.07}^{+0.06}$. These estimates are ind…
The applicability of a linearized perturbed FLRW metric to the late, lumpy universe has been subject to debate. We consider in an elementary way the Newtonian limit of the Einstein equations with this ansatz for the case of structure formation in late-time cosmology, on small and large scales, and argue that linearizing the Einstein tensor produces only a small error down to arbitrarily small, decoupled scales (e.g. Solar system scales). On subhorizon patches, the metric scale factor becomes a coordinate choice equivalent to choosing the spatial curvature, and not a sign that the FLRW metric c…
We derive a generalized luminosity distance versus redshift relation for a linearly perturbed FLRW (Friedmann-Lemaitre-Robertson-Walker) metric with two scalar mode excitations. We use two equivalent approaches, based on the Jacobi map and the van Vleck determinant respectively. We apply the resultant formula to two simple models - an exact FLRW universe and an approximate FLRW universe perturbed by a single scalar mode sinusoidally varying with time. For both models we derive a cosmographic expansion for d_L in terms of z. We comment on the interpretation of our results and their possible app…
Constraining Cosmological Parameters From Statistical Superluminal Effects Without a Distance Ladder
Research Unit in Scientific Culture and Mediation - CERIST（科学文化与调解研究单位-CERIST）；Laboratoire de Physique Mathématique et Subatomique (LPMS)（数学与亚原子物理实验室(LPMS)）；University of Constantine 1（君士坦丁第一大学）
The discrepancy between the values of the Hubble constant $H_0$ derived from the local distance ladder and the cosmic microwave background provides a tantalising hint of new physics. We explore a potential resolution involving screened fifth forces in the local Universe, which alter the Cepheid calibration of supernova distances. In particular, if the Cepheids with direct distance measurements from parallax or water masers are screened but a significant fraction of those in other galaxies are not, neglecting the difference between their underlying period--luminosity relations biases the local …
We present a measurement of the Hubble constant ($H_{0}$) and other cosmological parameters from a joint analysis of six gravitationally lensed quasars with measured time delays. All lenses except the first are analyzed blindly with respect to the cosmological parameters. In a flat $Λ$CDM cosmology, we find $H_{0} = 73.3_{-1.8}^{+1.7}$, a 2.4% precision measurement, in agreement with local measurements of $H_{0}$ from type Ia supernovae calibrated by the distance ladder, but in $3.1σ$ tension with $Planck$ observations of the cosmic microwave background (CMB). This method is completely indepen…
A measurement of the expansion rate of the Universe (that is the Hubble constant, H0) is derived here using the gamma-ray attenuation observed in the spectra of gamma-ray sources produced by the interaction of extragalactic gamma-ray photons with the photons of the extragalactic background light (EBL). The Hubble constant that is determined with our technique, for a Lambda CDM cosmology, is H0=71.8_{-5.6}^{+4.6}(stat)_{-13.8}^{+7.2}(syst) km s^{-1} Mpc^{-1}. This value is compatible with present-day measurements using well established methods such as local distance ladders and cosmological pro…
The cosmology of $f(R, L_m)$ gravity: constraining the background and perturbed dynamics
North-West University（西北大学）；Wolkite University（沃尔基特大学）；Entoto Observatory and Research Center, Space Science and Geospatial Institute（恩托托观测与研究中心，空间科学与地理信息研究所）；Imam Mohammad Ibn Saud Islamic University (IMSIU)（伊马姆穆罕默德·本·沙特伊斯兰大学）；University of Khartoum（喀土穆大学）；National Institute for Theoretical and Computations Sciences (NITheCS)（国家理论与计算科学研究所）
An error was made when calculating the amplitude of the perturbed scalar mode after Hubble-radius crossing. When corrected, it eliminates the leading term in the statistical anisotropy of the power spectrum, reducing it from the previously claimed upper estimate of $\lesssim 10^{-2}$ to the level of at most $10^{-6}$, which is beyond the possibility of detection. The general conclusion is that a single-field inflationary scenario cannot produce statistical anisotropy of appreciable magnitude.
One of the outstanding problems in modern physics is the origin is of accelerated expansion of the universe. High-precision determinations of the Hubble parameter $\mbox{H}_0$ at different redshifts provide direct insight into the Universe expansion: equation of state of the Dark Energy, geometry and curvature of space, sum of neutrino masses and isotropy of the Universe. We investigate the effect of chemical composition on the classical distance ladder based on Cepheids stars and Supernovae type Ia. Cepheids belonging to Magellanic Clouds represent a natural anchor for the ladder, due to thei…
Using sedimentary and eclipse-based measurements of the lunar recession velocity, we derive a new local-Universe measurement of the Hubble constant ($H_0$) from the recession rate of Earth's Moon. Taking into account the effects of tides, we find a value of $H_{0}$ = 63.01 $\pm$ 1.79 km s$^{-1}$ Mpc$^{-1}$, which is in approximate agreement with the Planck space mission's measurement using the cosmic microwave background (CMB) and base $Λ$CDM. Our new measurement represents the first ever model-independent, single-step measurement of the Universe's current expansion rate. This is also the firs…
In this work we investigate whether a certain phenomenological extension to the general relativity (GR), in the form of a gravitational phase transition (GPT) in the Universe, can reduce the external $Planck$ tensions with the local Hubble measurements and the distribution of matter, characterized by $σ_8$, as well as its internal inconsistencies in the lensing amplitude and the low--high $\ell$ parameter estimates. We introduce new degrees of freedom into the background and the two scalar perturbation equations in the Newtonian gauge, with simultaneous transitions from an early gravitational …
In this work we address the issue of peculiar velocity measurement in a perturbed Friedmann universe using the deviations from measured luminosity distances of standard candles from background FRW universe. We want to show and quantify the statement that in intermediate redshifts ($0.5< z < 2$), deviations from the background FRW model are not uniquely governed by peculiar velocities. Luminosity distances are modified by gravitational lensing. We also want to indicate the importance of relativistic calculations for peculiar velocity measurement at all redshifts. For this task we discuss the re…
The current tension between the direct and the early Universe measurements of the Hubble Constant, $H_0$, requires detailed scrutiny of all the data and methods used in the studies on both sides of the debate. The Cepheids in the type Ia supernova (SNIa) host galaxy NGC 5584 played a key role in the local measurement of $H_0$. The SH0ES project used the observations of this galaxy to derive a relation between Cepheids' periods and ratios of their amplitudes in different optical bands of the Hubble Space Telescope (HST), and used these relations to analyse the light curves of the Cepheids in ar…
Large-scale bulk peculiar motions introduce a characteristic length scale, inside which the local kinematics are dominated by peculiar-velocity perturbations rather than by the background Hubble expansion. Regions smaller than the aforementioned critical length, which typically varies between few hundred and several hundred Mpc, can be heavily "contaminated" by the observers' relative motion. For example, at the critical length -- hereafter referred to as the "transition scale", the sign of the locally measured deceleration parameter can change from positive to negative, while the surrounding …
The extragalactic distance scale is perhaps the most important application of stellar distance indicators. Among these, classical Cepheids are high-accuracy standard candles that support a $1.4\%$ measurement of Hubble's constant, $H_0$. The accuracy of Cepheid distances is thus directly relevant for understanding the implications of the Hubble tension, the $>5σ$ discord among direct, late-Universe $H_0$ measurements and $H_0$ values inferred from the early Universe observations assuming $Λ$CDM cosmology. This invited review aims to provide an accessible overview of the state of the art distan…
Assessing the significance and implications of the recently established Hubble tension requires the comprehensive identification, quantification, and mitigation of uncertainties and/or biases affecting $H_0$ measurements. Here, we investigate the previously overlooked distance scale bias resulting from the interplay between redshift and Leavitt laws in an expanding Universe: Redshift-Leavitt bias (RLB). Redshift dilates oscillation periods of pulsating stars residing in supernova-host galaxies relative to periods of identical stars residing in nearby (anchor) galaxies. Multiplying dilated $\lo…
