arXiv subjects

Adrienn Pataki

Publications and source records attributed to Adrienn Pataki.

3 recordsLinked to original sources

arXiv2025

A Case for an Inhomogeneous Einstein-de Sitter Universe

We present a local-to-global cosmological framework in which cosmic acceleration emerges from structure formation in an inhomogeneous Einstein-de Sitter (iEdS) universe, without dark energy. The model exhibits a quasilinear coasting evolution toward an effective Milne state driven by growing inhomogeneities. We test the iEdS model with ${H_0=72.5\ \mathrm{km\ s^{-1}\ Mpc^{-1}}}$ and ${\Omega_{\mathrm{m},0}=0.272}$ using CMB, BAO, and SN Ia data. The iEdS model fits the data comparably to $\Lambda$CDM and resolves the $H_0$ tension, while yielding a cosmic age ${t_0\simeq 13.67\ \mathrm{Gyr}}$ consistent with globular-cluster estimates.

astro-ph.CO↗

arXiv2025

Constraints on AvERA Cosmologies from Cosmic Chronometers and Type Ia Supernovae

We constrain AvERA cosmologies in comparison with the flat $\Lambda$CDM model using cosmic chronometer (CC) data and the Pantheon+ sample of type Ia supernovae (SNe Ia). The analysis includes fits to both CC and SN datasets using the \texttt{dynesty} dynamic nested sampling algorithm. For model comparison, we use the Bayesian model evidences and Anderson-Darling tests applied to the normalized residuals to assess consistency with a standard normal distribution. Best-fit parameters are derived within the redshift ranges $z \leq 2$ for CCs and $z \leq 2.3$ for SNe. For the baseline AvERA cosmology, we obtain best-fit values of the Hubble constant of ${H_0=68.32_{-3.27}^{+3.21}~\mathrm{km~s^{-1}~Mpc^{-1}}}$ from the CC analysis and ${H_0=71.99_{-1.03}^{+1.05}~\mathrm{km~s^{-1}~Mpc^{-1}}}$ from the SN analysis, each consistent within $1\sigma$ with the corresponding AvERA simulation value of $H(z=0)$. While both the CC and SN datasets yield higher Bayesian evidence for the flat $\Lambda$CDM model, they favor the AvERA cosmologies according to the Anderson-Darling test. We have identified signs of overfitting in each model, which suggests the possibility of overestimating the uncertainties in the Pantheon+ covariance matrix.

astro-ph.CO↗

arXiv2024

Cosmic chronometers, Pantheon+ supernovae, and quasars favor coasting cosmologies over the flat $Λ$CDM model

We test and compare coasting cosmological models with curvature parameters ${k=\left\{ -1,0,+1 \right\}}$ in ${H_0^2 c^{-2}}$ units and the flat $Λ$CDM model by fitting them to cosmic chronometers (CC), the Pantheon+ sample of type Ia supernovae (SNe), and standardized quasars (QSOs). We used the \texttt{emcee} code for fitting CC data, a custom Markov Chain Monte Carlo implementation for SNe and QSOs, and Anderson-Darling tests for normality on normalized residuals for model comparison. Best-fit parameters are presented, constrained by data within redshift ranges $z\leq 2$ for CCs, $z\leq 2.3$ for SNe, and $z\leq 7.54$ for QSOs. Coasting models, particularly the flat coasting model, are generally favored over the flat $Λ$CDM model. The overfitting of the flat $Λ$CDM model to Pantheon+ SNe and the large intrinsic scatter in QSO data suggest a need to refine error estimates in these datasets. We also highlight the seemingly fine-tuned nature of either the CC data or $Ω_{\mathrm{m},0}$ in the flat $Λ$CDM model to an ${H_1=H_0}$ coincidence when fitting ${H(z)=H_1z+H_0}$, a natural feature of coasting models.

astro-ph.CO↗