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The observed hemispherical power asymmetry in cosmic microwave background radiation may have originated from the modulations of superhorizon long-wavelength modes. In this work, we unveil different aspects of asymmetries generated from the long-wavelength mode modulations. We show that the same mechanism that leads to the observed cosmic microwave background hemispherical power asymmetry via superhorizon long-mode perturbation also yields dipole asymmetry in (a) the tensor perturbations power spectrum and (b) the halo bias parameter. These are different phenomena relevant to different cosmological histories, but both share the same underlying mechanism in generating asymmetries in the sky. We obtain the set of consistency conditions relating the amplitude of dipole asymmetries generated on tensor perturbations and halo bias parameter to the amplitude of dipole asymmetry generated on cosmic microwave background power spectrum. In addition, we show that this mechanism does not produce dipole asymmetry in acceleration expansion in an ACDM Universe because the superhorizon curvature perturbation is conserved in this background. [ABSTRACT FROM AUTHOR]

We study the time variation of the apparent flux of cosmological point sources due to the transient weak lensing by dark matter microhaloes. Assuming a transverse motion of microhaloes with respect to our line of sight, we derive the correspondence between the temporal power spectrum of the weak lensing magnification and the spatial power spectrum of density on small scales. Considering different approximations for the small-scale structure of dark matter, we predict the apparent magnitude of cosmological point sources to vary by as much as 10-4 -- 10-3, due to this effect, within a period of a few months. This red photometric noise has an almost perfect Gaussian statistics, to one part in ~104. We also compare the transient weak lensing power spectrum with the background effects such as the stellar microlensing on cosmological scales. A quasar lensed by a galaxy or cluster like a SDSSJ1004 + 4112 strong lensing system, with multiple images, is a suitable system for this study because (i) using the time-delay method between different images, we can remove the intrinsic variations of the quasar, and (ii) strong lensing enhances signals from the transient weak lensing. We also require the images to form at large angular separations from the center of the lensing structure, in order to minimize contamination by the stellar microlensing. With long-term monitoring of quasar strong lensing systems with a 10-meter class telescope, we can examine the existence of dark microhaloes as the building blocks of dark matter structures. Failure to detect this signal may either be caused by a breakdown of cold dark matter (CDM) hierarchy on small scales, or rather interpreted as evidence against a CDM paradigm, e.g., in favor of modified gravity models. [ABSTRACT FROM AUTHOR]

In this paper we provide a consistency relation between the amplitude of the hemispherical bipolar asymmetry, A, and the amplitude of the primordial non-Gaussianity in the squeezed limit, fNL, as |A| ≲ 10-1fNL. We demonstrate that this consistency condition is at work for any model of inflation in which the curvature perturbations are sourced by a single light field with the Bunch-Davies initial condition, irrespective of the number of inflation fields that contribute to the background inflationary expansion. As a nontrivial example, we show that observable hemispherical asymmetry can be generated in single-field nonattractor inflationary models. We also study hemispherical asymmetry generated in the models of multiple fields inflation. We show that A is controlled by the weighted sum of non-Gaussianity contribution from each field. In particular, we show that observable hemispherical asymmetry can be generated in models in which inhomogeneities are generated from a light scalar field modulating the surface of the end of inflation. [ABSTRACT FROM AUTHOR]

One of the open questions of modem cosmology is the nature and properties of the dark matter halo and its substructures. In this work we study the gravitational effect of dark matter substructures on pulsar timing observations. Since millisecond pulsars are stable and accurate emitters, they have been proposed as plausible astrophysical tools to probe the gravitational effects of dark matter structures. We study this effect on pulsar timing through Shapiro time delay (or integrated Sachs-Wolfe (ISW) effect) and Doppler effects statistically, showing that the latter dominates the signal. For this task, we relate the power spectrum of pulsar frequency change to the matter power spectrum on small scales, which we compute using the stable clustering hypothesis, as well as other models of nonlinear structure formation. We compare this power spectrum with the reach of current and future observations of pulsar timing designed for gravitational wave detection. Our results show that while current observations are unable to detect these signals, the sensitivity of the upcoming square kilometer array is only a factor of few weaker than our optimistic predictions. [ABSTRACT FROM AUTHOR]

The observed discrepancy of the Hubble parameter measurements in the local universe with the cosmic microwave background (CMB) data may indicate a new physics. It is vital to test the alternative models that reconcile the Hubble tension with other cosmological observations in this direction. The CMB lensing is a crucial observation that relates the early universe perturbations to the matter's late-time distribution. In this work, we study the prediction of the üΛCDM as a solution for H0 tension for CMB lensing and the low- and high-ℓ's temperature (TT) power spectrum internal inconsistency. We show that this model relaxes the low- and high-ℓ's TT mild inconsistency and the CMB lensing tensions simultaneously. Accordingly, üΛCDM having the same number of free parameters as ΛCDM with lensing amplitude AL added, has a better fit with Δχ²=-3.3. [ABSTRACT FROM AUTHOR]

Fuzzy dark matter (FDM) is one of the recent models for dark matter. According to this model, dark matter is made of very light scalar particles with considerable quantum mechanical effects on the galactic scale, which solves many problems of cold dark matter (CDM). Here we use the observed data from the rotation curve of the Milky Way (MW) Galaxy to compare the results from FDM and CDM models. We show that FDM adds a local peak on the rotation curve close to the center of the bulge, where its position and amplitude depend on the mass of FDM particles. By fitting the observed rotation curve with our expectation from FDM, we find that the mass of FDM is m=2.5-2.0+3.6×10-21 eV. We note that the local peak of the rotation curve in MW can also be explained in the CDM model with an extra inner bulge model for the MW Galaxy. We conclude that the FDM model explains this peak without a need for extra structure for the bulge. [ABSTRACT FROM AUTHOR]

One of the challenging questions in cosmology is the nature of dark matter particles. Fuzzy dark matter (FDM) is one of the candidates which is made of very light (m FDM = 10-22 - 10-21 eV) bosonic particles with no self-interaction. It is introduced by the motivation to solve the core-cusp problem in the galactic halos. In this work, we investigate the observational features from FDM halo collisions. Taking into account the quantum wavelength of the condensed bosonic structure, we determine the interference of the wave function of cores after collision. The fringe formation in the wave function is associated to the density contrast of the dark matter inside the colliding galaxies. The observational signatures of the fringes of the distribution of the dark matter are (i) on the lensing of the background sources, (ii) accumulation of the baryonic plasma tracking the interference of the FDM potential and (iii) excess in the x-ray emission from dense regions. Finally, we provide prospects for the observations of quantum wave features of FDM in the colliding galaxies. The NGC6240 colliding galaxy at the redshift of z = 0.024 is a suitable candidate for this study. No signal is detected from the fringes in the Chandra data and taking into account the angular resolution of the telescope, we put a constraint of m>7×10-23 eV on the mass of FDM particles. [ABSTRACT FROM AUTHOR]

We propose a cosmological model, üΛCDM, based on "über gravity," which is a canonical ensemble average of many theories of gravity. In this model, we have a sharp transition from (a purely) ΛCDM era to a phase in which the Ricci scalar is a constant. This transition occurs when the Ricci scalar reaches a critical scale or alternatively a transition redshift, z⊕. We use the observations of baryonic acoustic oscillations and supernovae Ia, as well as the cosmic microwave background data to constrain üΛCDM. This yields H0=70.6+1.1-1.3 km/s/Mpc, Ωm=0.2861±0.0092, and z⊕=0.537+0.277-0.375, providing a marginally better fit with a Akaike information criterion of 0.8. Therefore, üΛCDM can ease the H0 tension, albeit marginally, with one additional free parameter. We also provide a preliminary study of the linear perturbation theory in üΛCDM that points to interesting potential smoking guns in the observations of large scale structure at z

Excursion set theory (EST) is an analytical framework to study the large-scale structure of the Universe. EST introduces a procedure to calculate the number density of structures by relating the cosmological linear perturbation theory to the nonlinear structures in late time. In this work, we introduce a novel approach to reformulate the EST in matrix formalism. We propose that the matrix representation of EST will facilitate the calculations in this framework. The method is to discretize the two-dimensional plane of variance and density contrast of EST, where the trajectories for each point in the Universe lived there. The probability of having a density contrast in a chosen variance is represented by a probability ket. Naturally, the concept of the transition matrix pops up to define the trajectories. We also define the probability transition rate which is used to obtain the first up-crossing of trajectories and the number count of the structures. In this work we show that the discretization let us study the non-Markov processes by forcing them to look like a Wiener process. Also we discuss that the zero drift processes with Gaussian and also non-Gaussian initial conditions can be studied by this formalism. The continuous limit of the formalism is discussed, and the known Fokker-Planck dispersion equation is recovered. Finally we show that the probability of the most massive progenitors can be extracted in this framework. [ABSTRACT FROM AUTHOR]