Measurements of $$H_0$$ and reconstruction of the dark energy properties from a model-independent joint analysis

Gaussian processes (GP) provide an elegant and model-independent method for extracting cosmological information from the observational data. In this work, we employ GP to perform a joint analysis by using the geometrical cosmological probes such as Supernova Type Ia (SN), Cosmic chronometers (CC), Baryon Acoustic Oscillations (BAO), and the H0LiCOW lenses sample to constrain the Hubble constant $$H_0$$ H 0 , and reconstruct some properties of dark energy (DE), viz., the equation of state parameter w, the sound speed of DE perturbations $$c^2_s$$ c s 2 , and the ratio of DE density evolution $$X = \rho _\mathrm{de}/\rho _\mathrm{de,0}$$ X = ρ de / ρ de , 0 . From the joint analysis SN+CC+BAO+H0LiCOW, we find that $$H_0$$ H 0 is constrained at 1.1% precision with $$H_0 = 73.78 \pm 0.84\ \hbox {km}\ \hbox {s}^{-1}\,\hbox {Mpc}^{-1}$$ H 0 = 73.78 ± 0.84 km s - 1 Mpc - 1 , which is in agreement with SH0ES and H0LiCOW estimates, but in $$\sim 6.2 \sigma $$ ∼ 6.2 σ tension with the current CMB measurements of $$H_0$$ H 0 . With regard to the DE parameters, we find $$c^2_s < 0$$ c s 2 < 0 at $$\sim 2 \sigma $$ ∼ 2 σ at high z, and the possibility of X to become negative for $$z > 1.5$$ z > 1.5 . We compare our results with the ones obtained in the literature, and discuss the consequences of our main results on the DE theoretical framework.

An in-depth reanalysis of the alleged type Ia supernova progenitor Henize 2−428

Context. The nucleus of the planetary nebula Hen 2-428 is a short orbital-period (4.2 h), double-lined spectroscopic binary, whose status as a potential supernova type Ia progenitor has raised some controversy in the literature. Aims. With the aim of resolving this debate, we carried out an in-depth reanalysis of the system. Methods. Our approach combines a refined wavelength calibration, thorough line-identifications, improved radial-velocity measurements, non-LTE spectral modeling, as well as multi-band light-curve fitting. Our results are then discussed in view of state-of-the-art stellar evolutionary models. Results. Besides systematic zero-point shifts in the wavelength calibration of the OSIRIS spectra which were also used in the previous analysis of the system, we found that the spectra are contaminated with diffuse interstellar bands. Our Voigt-profile radial velocity fitting method, which considers the additional absorption of these diffuse interstellar bands, reveals significantly lower masses (M1 = 0.66 ± 0.11 M⊙ and M2 = 0.42 ± 0.07 M⊙) than previously reported and a mass ratio that is clearly below unity. Our spectral and light curve analyses lead to consistent results, however, we find higher effective temperatures and smaller radii than previously reported. Moreover, we find that the red-excess that was reported before to prove to be a mere artifact of an outdated reddening law that was applied. Conclusions. Our work shows that blends of He II λ 5412 Å with diffuse interstellar bands have led to an overestimation of the previously reported dynamical masses of Hen 2−428. The merging event of Hen 2−428 will not be recognised as a supernova type Ia, but most likely leads to the formation of a H-deficient star. We suggest that the system was formed via a first stable mass transfer episode, followed by common envelope evolution, and it is now composed of a post-early asymptotic giant branch star and a reheated He-core white dwarf.

The quantum gravitational field theory and the domains of its fix points for inflationary or low-redshift universe

We study a quantum field theory for the Einstein–Cartan gravity and the domain of its ultraviolet unstable (stable) fixed point [Formula: see text] [Formula: see text] of running gravitational constant [Formula: see text], where inflationary (low-redshift) universe can be realized as the basic space-time cutoff [Formula: see text] approaching to the Planck length [Formula: see text]. Because the fundamental operators of quantum gravitational field theory are dimension-2 area operators, the cosmological constant is inversely proportional to the squared correlation length [Formula: see text]. The correlation length [Formula: see text] characterizes an infrared size of a causally correlate patch of the universe. The quantitative description of low-redshift universe in the scaling-invariant region of fixed point [Formula: see text] is given, and its deviation from the [Formula: see text]CDM can be examined by recent cosmological observations, such as supernova Type Ia.

Study of a quadratic redshift-based correction in f(R) gravity with Baryonic matter

This paper is considered as a second-order redshift-based corrections in derivative of modified gravitational action, f(R), to explain the late time acceleration which is appeared by Supernova Type Ia (SNeIa) without considering the dark components. Here, we obtained the cosmological dynamic parameters of universe for this redshift depended corrections. Next, we used the recent data of SNeIa Union2, shift parameter of the cosmic background radiation, Baryon acoustic oscillation from sloan digital sky survey (SDSS), and combined analysis of these observations to put constraints on the parameters of the selected F(z) model. It is very interesting that the well-known age problem of the three old objects for combined observations can be alleviated in this model. Finally, the reference action will be constructed in terms of its Taylor expansion. Also, we show that the reconstructed action definitely pass the solar system and stability of the cosmological solution tests.