Title:Fireball anti-nucleosynthesis

Authors:Michael A. Fedderke, David E. Kaplan, Anubhav Mathur, Surjeet Rajendran, Erwin H. Tanin

Abstract:The tentative identification of approximately ten relativistic anti-helium cosmic-ray events at AMS-02 would, if confirmed, challenge our understanding of the astrophysical synthesis of heavy anti-nuclei. We propose a novel scenario for the enhanced production of such anti-nuclei that is triggered by isolated, catastrophic injections of large quantities of energetic Standard Model (SM) anti-quarks in our galaxy by physics beyond the Standard Model (BSM). We demonstrate that SM anti-nucleosynthetic processes that occur in the resulting rapidly expanding, thermalized fireballs of SM plasma can, for a reasonable range of parameters, produce the reported tentative $\sim 2:1$ ratio of anti-helium-3 to anti-helium-4 events at AMS-02, as well as their relativistic boosts. Moreover, we show that this can be achieved without violating anti-deuterium or anti-proton flux constraints for the appropriate anti-helium fluxes. A plausible BSM paradigm for the catastrophic injections is the collision of macroscopic composite dark-matter objects carrying large net anti-baryon number. Such a scenario would require these objects to be cosmologically stable, but to destabilize upon collision, promptly releasing a fraction of their mass energy into SM anti-particles within a tiny volume. We show that, in principle, the injection rate needed to attain the necessary anti-helium fluxes and the energetic conditions required to seed the fireballs appear possible to obtain in such a paradigm. We leave open the question of constructing a BSM particle physics model to realize this, but we suggest two concrete scenarios as promising targets for further investigation.

Abstract: 2402.16460
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Title:Search for Wormhole Candidates: Accreting Wormholes with Monopole Magnetic Fields

Authors:Mikhail Piotrovich, Serguei Krasnikov, Stanislava Buliga, Tinatin Natsvlishvili

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Abstract:The existence of even the simplest magnetized wormholes may lead to observable consequences. In the case where both the wormhole and the magnetic field around its mouths are static and spherically symmetric, and gas in the region near the wormhole falls radially into it, the former's spectrum contains bright cyclotron or synchrotron lines due to the interaction of charged plasma particles with the magnetic field. At the same time, due to spherical symmetry, the radiation is non-polarized. The emission of this just-described exotic type (non-thermal, but non-polarized) may be a wormhole signature. Also, in this scenario, the formation of an accretion disk is still quite possible at some distance from the wormhole, but a monopole magnetic field could complicate this process and lead to the emergence of asymmetrical and one-sided relativistic jets.

Comments:

11 pages, 1 figure

Abstract: 2402.16483
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Title:Using Spherical Harmonics to solve the Boltzmann equation: an operator based approach

Authors:Nils W. Schween, Brian Reville

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Abstract:The transport of charged particles or photons in a scattering medium can be modelled with a Boltzmann equation. The mathematical treatment for scattering in such scenarios is often simplified if evaluated in a frame where the scattering centres are, on average, at rest. It is common therefore, to use a mixed coordinate system, wherein space and time are measured in a fixed inertial frame, while momenta are measured in a "co-moving" frame. To facilitate analytic and numerical solutions, the momentum dependency of the phase-space density may be expanded as a series of spherical harmonics, typically truncated at low order. A method for deriving the system of equations for the expansion coefficients of the spherical harmonics to arbitrary order is presented in the limit of isotropic, small-angle scattering. The method of derivation takes advantage of operators acting on the space of spherical harmonics. The matrix representations of these operators are employed to compute the system of equations. The computation of matrix representations is detailed and subsequently simplified with the aid of rotations of the coordinate system. The eigenvalues and eigenvectors of the matrix representations are investigated to prepare the application of standard numerical techniques, e.g. the finite volume method or the discontinuous Galerkin method, to solve the system.

Abstract: 2402.17140
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Title:Direct Detection of Dark Photon Dark Matter with the James Webb Space Telescope

Authors:Haipeng An, Shuailiang Ge, Jia Liu, Zhiyao Lu

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Abstract:In this study, we propose an investigation into dark photon dark matter (DPDM) within the infrared frequency band, utilizing highly sensitive infrared light detectors commonly integrated into space telescopes, such as the James Webb Space Telescope (JWST). The presence of DPDM induces electron oscillations in the reflector of these detectors. Consequently, these oscillating electrons can emit monochromatic electromagnetic waves with a frequency almost equivalent to the mass of DPDM. By employing the stationary phase approximation, we can demonstrate that when the size of the reflector significantly exceeds the wavelength of the electromagnetic wave, the contribution to the electromagnetic wave field at a given position primarily stems from the surface unit perpendicular to the relative position vector. This simplification results in the reduction of electromagnetic wave calculations to ray optics. By applying this concept to JWST, our analysis of observational data demonstrates the potential to establish constraints on the kinetic mixing between the photon and dark photon within the range [10, 500] THz. Despite JWST not being optimized for DPDM searches, our findings reveal constraints comparable to those obtained from the XENON1T experiment in the laboratory, as well as astrophysical constraints from solar emission. Additionally, we explore strategies to optimize future experiments specifically designed for DPDM searches.

Abstract: 2402.17575
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Title:Models of hot star decretion disks

Authors:Petr Kurfürst

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Abstract:Massive stars can during their evolution reach the phase of critical (or very rapid, near-critical) rotation when further increase in rotation rate is no longer kinematically allowed. The mass ejection and angular momentum outward transport from such rapidly rotating star's equatorial surface may lead to formation and supports further existence of a circumstellar outflowing (stellar decretion) disk. The efficient mechanism for the outward transport of the mass and angular momentum is provided by the anomalous viscosity. The outer supersonic regions of the disks can extend up to a significantly large distance from the parent star, the exact radial extension is however basically unknown, partly due to the uncertainties in radial variations of temperature and viscosity.
We study in detail the behavior of hydrodynamic quantities, i.e., the evolution of density, radial and azimuthal velocity, and angular momentum loss rate in stellar decretion disks out to extremely distant regions. We investigate the dependence of these physical characteristics on the distribution of temperature and viscosity. We also study the magnetorotational instability, which we regard to be the source of anomalous viscosity in such outflowing disks and to some extent we provide the preliminary models of the two-dimensional radially-vertically correlated distribution of the disk density and temperature.
We developed our own two-dimensional hydrodynamic and magnetohydrodynamic numerical code based on an explicit Eulerian finite difference scheme on staggered grid, including full Navier-Stokes viscosity. We use semianalytic approach to investigate the radial profile of magnetorotational instability, where on the base of the numerical time-dependent hydrodynamic model we analytically study the stability of outflowing disks submerged to the magnetic field of central star.

Comments:

PhD Thesis

Abstract: 2402.18645
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Title:Design of the 50-meter Atacama Large Aperture Submm Telescope

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Abstract:Submillimeter and millimeter wavelengths can reveal a vast range of objects and phenomena that are either too cold, too distant, or too hot and energetic to be measured at visible wavelengths. For decades the astronomical community has highlighted the need for a large, high-throughput submm single dish that can map statistically significant portions of the sky with sufficient surface brightness sensitivity and angular and spectral resolution to probe truly representative source populations. The Atacama Large Aperture Submillimeter Telescope (AtLAST), with its 50-m aperture and $2^\circ$ maximal field of view, aims to be such a facility. We present here the full design concept for AtLAST, developed through an EU-funded project. Our design approach begins with a long lineage of submm telescopes, relies on calculations and simulations to realize the optics, and uses finite element analysis to optimize the mechanical structure and subsystems. The result is an innovative rocking chair design with six instrument bays, two of which are mounted on Nasmyth platforms. AtLAST will be capable of $3^\circ\,\rm s^{-1}$ scanning and $1^\circ\,\rm s^{-2}$ acceleration, and will feature a surface accuracy of $\leq 20~\mu$m half wavefront error allowing observations up to $\approx 950$~GHz. Further, AtLAST will be a sustainable, visionary facility that will allow upgrades for decades to come. The demanding design requirements for AtLAST, set by transformative science goals, were met by combining novel concepts with lessons learned from past experience. While some aspects require further testing, prototyping, and field demonstrations, we estimate that the design will be construction-ready this decade.

Comments:

26 pages, 27 figures; Submitted to A&A

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