An upper bound on the energies of massive particles would be very important because it was set an upper bound a many kinds of high energy physics, including but not limited to sphaleron interactions, which are critical to baryogenesis and leptogenesis, and to the stability of the Higgs vacuum.
Beginning from the standard Arnowitt-Deser-Misner (ADM) formulation of general relativity we construct a tentative model of quantum gravity from the point of view of an observer with constant proper acceleration, just outside of a horizon of spacetime. In addition of producing the standard results of black-hole thermodynamics, our model makes an entirely new prediction that there is a certain upper bound for the energies of massive particles. For protons, for instance, this upper bound is around 1.1×10^21eV. The result is interesting, because this energy is roughly of the same order of magnitude as are the highest energies ever measured for protons in cosmic rays.
Jarmo Mäkelä, "A Possible Quantum Effect of Gravitation" arXiv:2405.18502 (May 28, 2024).
arXiv:2405.20256 (cross-list from astro-ph.CO) [pdf, ps, html, other]
ReplyDeleteGravitational Lensing in More Realistic Dark Matter Halo Models
Ali Tizfahm, Saeed Fakhry, Javad T. Firouzjaee
Comments: 13 pages; 5 figures; Refs included
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
In this study, we investigate gravitational lensing within the framework of more realistic dark matter halo models, transcending the limitations of spherical-collapse approximations. Through analytical computations utilizing diverse mass functions, we address critical factors typically overlooked in the standard Press-Schechter formalism, including ellipsoidal-collapse conditions, angular momentum dynamics, dynamical friction, and the cosmological constant. Our analysis incorporates two widely recognized halo density profiles, the Navarro-Frenk-White and Einasto profiles, considering both spherical and ellipsoidal-collapse scenarios. We present relevant calculations of pivotal gravitational lensing observables, such as Einstein radii, lensing optical depths, and time delays, spanning a wide range of redshifts and masses across two distinct lensing models: the point mass and singular isothermal sphere (SIS) lens models. Our findings illuminate that adopting more realistic dark matter halo models leads to heightened lensing effects compared to their spherical-collapse counterparts. Furthermore, our analyses of lensing optical depths and time delays reveal distinct characteristics between point mass and SIS lens models. These outcomes highlight the need for more realistic halo descriptions instead of simple approximations when modeling gravitational lensing, as this approach can potentially better reveal the complex structures of dark matter.
Noted. Baby steps, but progress.
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