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Alicki, R., Barenboim, G., & Jenkins, A. (2025). The irreversible relaxation of inflation. Phys. Lett. B, 866, 139519–6pp.
Abstract: Based on the results of a previous analysis of the Markovian master equation for the irreversible evolution of an open system embedded in de Sitter space [7], we include in the cosmological Friedmann equations a contribution from the presence of a physical bath at temperature T-dS = h//2 pi, where h is the Hubble parameter. We show that this provides a mechanism for the irreversible relaxation of the cosmological constant and a graceful exit to inflation, without need for subsequent reheating. Thermal particle production during inflation gives adiabatic, Gaussian, and approximately scale-invariant cosmological perturbations. We thus obtain the main features of inflation without any inflaton potential. To clarify the thermodynamic interpretation of these results, we consider the analogy of this irreversible relaxation to superfluorescence in quantum optics.
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Pilotto, E., Ferrer, F. J., Akhmadaliev, S., Fernandez, A., Gadea, A., Gomez Camacho, J., et al. (2025). Comparing 3He content in magnetron sputtered and implanted targets for nuclear studies. Eur. Phys. J. A, 61(5), 117–8pp.
Abstract: He-3 targets are a valuable tool in nuclear physics, particularly for studying nuclear structure and dynamics via direct reactions in inverse kinematics. However, they are often prone to degradation under intense beam irradiation and have insufficient He-3 content for use with lowintensity exotic beams. In a recent AGATA experiment at LNL, designed to study the astrophysically relevant lifetime of a O-15 excited state, two types of He-3 targets were tested. One was produced using ion implantation and the other with a novel magnetron sputtering technique, in both cases on Au substrates. Following irradiation with a stable O-16 beam, they were characterized using Nuclear Reaction Analysis (NRA) and Elastic Recoil Detection Analysis (ERDA). Results demonstrated that, under the here used fabrication conditions, sputtered targets present a higher He-3 content, while implanted ones exhibit thinner profiles. This highlights the possibilities and complementarity of these targets, suggesting their tailored use for future experimental campaigns.
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Tolosa-Delgado, A. et al, Tain, J. L., Agramunt, J., Algora, A., Domingo-Pardo, C., & Morales, A. I. (2025). Impact of Newly Measured β-Delayed Neutron Emitters around 78Ni on Light Element Nucleosynthesis in the Neutrino Wind Following a Neutron Star Merger. Phys. Rev. Lett., 134(17), 172701–11pp.
Abstract: Neutron emission probabilities and half-lives of 37 /3-delayed neutron emitters from 75Ni to 92Br were measured at the RIKEN Nishina Center in Japan, including 11 one-neutron and 13 two-neutron emission probabilities and six half-lives for the first time that supersede theoretical estimates. These nuclei lie in the path of the weak r process occurring in neutrino-driven winds from the accretion disk formed after the merger of two neutron stars synthesizing elements in the A 80 abundance peak. The presence of such elements dominates the accompanying kilonova emission over the first few days and have been identified in the AT2017gfo event, associated to the gravitational wave detection GW170817. Abundance calculations based on over 17 000 simulated trajectories describing the evolution of matter properties in the merger outflows show that the new data lead to an increase of 50%-70% in the abundance of Y, Zr, Nb, and Mo. This enhancement is large compared to the scatter of relative abundances observed in old very metal poor stars and thus is significant in the comparison with other possible astrophysical processes contributing to the light-element production. These results underline the importance of including experimental decay data for very neutron-rich /3-delayed neutron emitters into r-process models.
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KM3NeT Collaboration(Aiello, S. et al), Alves Garre, S., Bariego-Quintana, A., Calvo, D., Cecchini, V., Garcia Soto, A., et al. (2025). On the Potential Cosmogenic Origin of the Ultra-high-energy Event KM3-230213A. Astrophys. J. Lett., 984(2), L41–8pp.
Abstract: On 2023 February 13, the KM3NeT/ARCA telescope observed a track-like event compatible with a ultra-high-energy muon with an estimated energy of 120 PeV, produced by a neutrino with an even higher energy, making it the most energetic neutrino event ever detected. A diffuse cosmogenic component is expected to originate from the interactions of ultra-high-energy cosmic rays with ambient photon and matter fields. The flux level required by the KM3NeT/ARCA event is, however, in tension with the standard cosmogenic neutrino predictions based on the observations collected by the Pierre Auger Observatory and Telescope Array over the last decade of the ultra-high-energy cosmic rays above the ankle (hence from the local Universe, z less than or similar to 1). We show here that both observations can be reconciled by extending the integration of the equivalent cosmogenic neutrino flux up to a redshift of zmax=6 and considering either source evolution effects or the presence of a subdominant independent proton component in the ultra-high-energy cosmic-ray flux, thus placing constraints on known cosmic accelerators.
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Paxman, C. J. et al, Domingo-Pardo, C., Gadea, A., & Valiente-Dobon, J. J. (2025). Probing Exotic Cross-Shell Interactions at N=28 with Single-Neutron Transfer on 47K. Phys. Rev. Lett., 134(16), 162504–8pp.
Abstract: We present the first measurement of the 47K(d, p gamma)48K transfer reaction, performed in inverse kinematics using a reaccelerated beam of 47K. The level scheme of 48K has been greatly extended, with nine new bound excited states identified and spectroscopic factors deduced. Uniquely, the 47K(d, p) reaction gives access to nuclear states that are sensitive to the interaction of protons and neutrons in the widely spaced 1s and fp orbitals, respectively. Detailed comparisons with SDPF-U and SDPF-MU shell-model calculations reveal a number of discrepancies between theory and experiment. Intriguingly, a systematic overestimation of spectroscopic factors and a poor reproduction of the energies for 1- states suggests that the mixing between the pi s11/2d43/2 and pi s21/2d33/2 proton configurations in 48K is not correctly described using current interactions, challenging our description of light nuclei around the N = 28 island of inversion.
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