ﻻ يوجد ملخص باللغة العربية
We study systematically which features in the cosmic microwave background (CMB) and large-scale structure (LSS) probe various inhomogeneous properties of the dark sectors (including neutrinos, dark matter, and dark energy). We stress, and quantify by simple formulas, that the primary CMB anisotropies are very susceptible to the gravitational potentials during horizon entry, less at recombination. The CMB thus allows us to scan Phi+Psi and the underlying dark kinetics for all redshifts z~1-10^5. LSS, on the other hand, responds strongest to Phi at low redshifts. Dark perturbations are often parameterized by the anisotropic stress and effective sound speed (stiffness). We find that the dark anisotropic stress and stiffness influence the visible species at the correspondingly early and late stages of horizon entry, and affect stronger respectively the CMB and LSS. The CMB yet remains essential to probing the stiff perturbations of light neutrinos and dark energy, detectable only during horizon entry. The clustering of dark species and large propagation speed of their inhomogeneities also map to distinctive features in the CMB and LSS. -Any parameterization of the signatures of dark kinetics that assumes general relativity can effectively accommodate any modified gravity (MG) that retains the equivalence principle for the visible sectors. This implies that formally the nonstandard structure growth or Phi/Psi ratio, while indicative, are not definitive MG signatures. The definitive signatures of MG may include the strong dependence of the apparent dark dynamics on visible species, its superluminality, and the nonstandard phenomenology of gravitational waves.
We point out that the theoretical predictions for the inflationary observables may be generically altered by the presence of fields which are heavier than the Hubble rate during inflation and whose dynamics is usually neglected. They introduce correc
The aim of this paper is to answer the following two questions: (1) Given cosmological observations of the expansion history and linear perturbations in a range of redshifts and scales as precise as is required, which of the properties of dark energy
It is well known that gravitons can convert into photons, and vice versa, in the presence of cosmological magnetic fields. We study this conversion process in the context of atomic dark matter scenario. In this scenario, we can expect cosmological da
Theoretical descriptions of observable quantities in cosmological perturbation theory should be independent of coordinate systems. This statement is often referred to as gauge-invariance of observable quantities, and the sanity of their theoretical d
Current cosmological data exhibit a tension between inferences of the Hubble constant, $H_0$, derived from early and late-universe measurements. One proposed solution is to introduce a new component in the early universe, which initially acts as earl