Astronomy, Volume 3, Issue 4 (December 2024) – 4 articles

For the deconfinement phase of an SU(2) Yang–Mills theory, we compute the axion mass $m_A$ by appealing to the Veneziano–Witten formula. The topological susceptibility $\chi$ arises (i) from a precisely computable thermal ground-state contribution due to a center of a relevant (anti)caloron, and (ii) from contributions due to free thermal quasi-particles in the effective theory. Both (i) and (ii) are derived by using standard Euclidean thermal field theory techniques. While contribution (i) is positive and $\propto T^4$, contribution (ii) is negative, as demanded by reflection positivity, but negligible compared to contribution (i). As a consequence, practically from the critical temperature $T_c$ onward, a real-valued axion mass $m_A\left(T\right)=\sqrt{{\displaystyle \frac{2}{3}}}\pi {\displaystyle \frac{T^2}{M_P}}$ emerges when the Peccei–Quinn scale is assumed to be the Planck mass $M_P$, independently of the Yang–Mills scale that the axion associates with. We discuss why our results deviate from those found in the dilute instanton gas and interacting instanton liquid approximations, and from results obtained in lattice simulations. Assuming the universe is dark sector to be based on such ultralight axion species, which are nonrelativistic for $T\ll M_P$, we investigate the cosmological conditions for their global Bose condensation as the very early universe cooled to temperatures of the order of ${10}^9$eV. Full article

To investigate the gravitational effects of massive objects on a typical observer, we studied the dynamics of a test particle following ${\mathrm{BMS}}_3$ geodesics. We constructed the ${\mathrm{BMS}}_3$ framework using the canonical phase space formalism and the corresponding Hamiltonian. We focused on analyzing these effects at fine scales of spacetime, which led us to quantization of the phase space. By deriving and studying the solutions of the quantum equations of motion for the test particle, we obtained its energy spectrum and explored the behavior of its wave function. These findings offer a fresh perspective on gravitational interactions in the context of quantum mechanics, providing an alternative approach to traditional quantum field theory analyses. Full article

Archival XMM and ROSAT X-Ray data are used to investigate the structure of the Abell 548–Abell 3367 region. Based on previous optical studies, this is a region likely to be rich in structure, although studies are in disagreement regarding the connection between Abell 3367 and Abell 548. We use the available archival X-Ray data together with kinematic data of counterpart galaxies to address this question and determine the structure in this region. The region is particularly rich in X-Ray structure elongated along a SW-NE axis and consisting of numerous extended X-Ray sources. In general, the structure consists of many galaxy groups and clusters which appear segregated in X-Ray luminosity, with the least luminous ~30% toward the outer region of the clusters, possibly tracing a filament. We find evidence to suggest a supercluster of three clusters at redshifts ~0.04, 0.045, and 0.06. Several of the X-Ray sources coincident with Abell 3367 have counterpart galaxy redshifts consistent with Abell 548, while others are significantly higher. This supports the formation of a supercluster consisting of Abell 548 and Abell 3667, with the higher-redshift X-Ray source being a background object. In addition, they are part of a larger structure consisting of a previously identified cluster at redshift 0.04 and two groups at redshift ~0.06. There is also filamentary structure at z ~0.103. The ubiquity of groups in the large-scale structure suggests that they provide an environment where galaxies are in close proximity and evolution via interaction can proceed well before the galaxies make their way into the dense central region of a cluster. Full article

We present a model-independent method for separating the spectral counterparts of the active galactic nucleus (AGN) NGC 1275 from the surrounding emission of the Perseus cluster, as observed by Suzaku/XIS cameras. The Perseus cluster emission extends to higher energies than typically observed in AGN environments, reaching up to 9–10 keV. This necessitates precise separation of AGN and cluster spectra. To circumvent the degeneracy arising from numerous spectral fitting parameters, including elemental abundances, thermal and Compton emissions from the nucleus, and spectral parameters of the jet synchrotron self-Compton/inverse Compton emissions, we avoid traditional spectral fitting methods. Instead, we leverage spatial resolution and employ a double background subtraction approach. We apply this procedure to the complete set of Suzaku/XIS observational data for NGC 1275, resulting in cleaned spectra and a light curve of the AGN emission in this system. To demonstrate the applicability of our method, we also utilize the available XMM-Newton/EPIC data. Full article