Abstract: The nuclear properties of bismuth isotopes (Z = 83), with just one valence proton above the closed spherical shell at Z = 82, are expected to be governed by a single unpaired proton. However, already in semimagic 209Bi (Z = 83, N = 126), the magnetic moment (mu) strongly deviates from the single-particle Schmidt value. A near linear decrease in μwith the increase of N after the N = 126 magic number was observed up to N = 130. In order to test whether this trend is kept at N> 130 and to reveal the underlying mechanisms, an investigation of Bi-215,Bi-217 (N = 132, 134) has been undertaken. The magnetic dipole and electric quadrupole moments of the I-x= 9/2-nuclear ground states in these isotopes have been measured for the first time using the in-source resonance-ionization spectroscopy technique at ISOLDE (CERN). It has been shown that the linearly decreasing trend of mu(Bi-209,211,213(g)) is broken in Bi-215,Bi-217 with a nearly constant value of μobserved. Experimental data have been compared to calculations in the framework of the configuration-interaction shell model with the monopole-based universal VMU+LS interaction. The peculiarities in the behavior of μ(Bi, 9/2-) with increasing neutron number are explained as being due to the shell evolution, change of the neutron orbitals occupancies and strong configuration mixing beyond N = 130. Also, the difference in the μtrends for bismuth (Z = 83) and astatine (Z = 85) isotopes with N> 126 are reproduced by the shell-model calculations. It is shown that monopole interaction plays noticeable role in the description of the peculiarities of the μbehaviour. Additionally, the extension of the application of the V-MU interaction to the μisotopic trends for heavy nuclei is important for further study of the capabilities of this promising version of the shell-model calculations.

Abstract: A fundamental question in cosmology is whether dark energy evolves over time, a topic that has gained prominence since the discovery of cosmic acceleration. Recently, the DESI collaboration has reported increasing evidence for evolving dark energy using combinations of cosmic microwave background (CMB), type Ia supernova (SN), and their new measurements of baryon acoustic oscillations (BAO). However, our analysis reveals that these combinations are problematic due to clear tensions among the CMB, BAO and SN datasets. Consequently, DESI's claim of dynamical dark energy (DDE) is not robust. A more reliable approach involves constraining the evolution of dark energy using each dataset independently. Through a statistical comparison for each dataset, on average, we find that DDE is strongly preferred over the Lambda\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Lambda $$\end{document}CDM model. This suggests that DDE likely exists, although its real parameter space remains elusive due to weak constraints on the dark energy equation of state and inconsistencies among the datasets. Interestingly, when considering DDE, none of the individual datasets – including CMB, DESI DR2, Pantheon+, Union3, and DESY5 – can independently detect cosmic acceleration at a significant level. Our findings not only clarify the current understanding of the nature of dark energy but also challenge the established discovery of cosmic acceleration and the long-held notion that dark energy exerts negative pressure. Both individual and combined datasets suggest that the ultimate fate of the universe is likely to be dominated by matter rather than dark energy.

Abstract: We face here the problem of uncertainties in correlation functions due to the freedom in the off-shell dependence of the wave functions or, equivalently, off-shell ambiguities in the scattering matrices. We make the study for the case of meson baryon interaction, choosing the K Lambda, K Sigma, and rjN coupled channels, which are related to the N*(1535) resonance, and the K+ K<overline>0 channel related to the a0(980) resonance. We find that, by using realistic interactions based on chiral dynamics, the uncertainties are small, of the order of 2-3%, but could be much bigger if other methods are used. However, our study shows the way to optimally overcome these uncertainties in the analysis of correlation functions, and we provide a series of recommendations for any general analysis.