Star-UBB Seminar Series:- Axion-Like-Particles, Direct Detection & Solar constraints
The Sun could produce Axion-Like Particles(ALPs) with masses in the keV-range. A fraction of them would be trapped in the solar gravitational field and accumulate over cosmic times. Their decay into photons would contribute to the observed solar X-ray flux, whose measurements can be used to constrain ALP models. This has been studied considering the Primakoff process the main production mechanism in the absence of a couplings to electrons. However, ALP production in the solar core is dominated by the photon coalescence, and this will improve the bound on their coupling to photons by an order of magnitude for ALP masses between 3 keV and 40 keV. For non-vanishing coupling to electrons, Compton process soon become the dominant one. At the same time, trapped ALPs can be Compton-absorbed while crossing the Sun during their orbits, and this counter-balances the production, partially or entirely depending on parameter values. This results in two well-defined regime in the exclusion limits, with a transition triggered by the coupling to electrons. Out of the transitional region, the solar X-ray constraints on ALPs are exclusively governed by the coupling to photons.
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講者：Prof. Mar Bastero-Gil (Departamento de Fısica Teorica y del Cosmos, Universidad de Granada, Granada, Spain)
Scientific and Technological Advanced Research- Babeș-Bolyai University(Star-UBB) Seminar Series in Gravitation, Cosmology and Astrophysics
Presently a period of rapid and intense change are being witnessed in our understanding of the gravitational force, at a rate that is quickly increasing since the important observational discoveries of the late 1990s. With the advent of new observational techniques, the emergence of important cosmological and astrophysical paradigms can be seen that lead to a deep change in our understanding of the Universe. Astronomical observations strongly suggest that at large scales the force of gravity may not behave according to standard general relativity, and that a generalization of the gravitational action, either at the geometric level, or at the matter level, may be required for a full understanding of the gravitational interaction.
The goal of the present seminar is to bring Theoretical Gravitational Physics closer to the observations and experiments, and to discuss current topics in general relativity, high-energy physics, astrophysics and cosmology.