This paper examines the thermal properties of a Bardeen-type black hole (BH) embedded in a cloud-of-strings and a quintessence background within the Tsallis non-extensive entropy framework. Within the extended thermodynamic phase space, generalized expressions are derived for the Tsallis thermodynamic temperature, heat capacity, equation of state, Gibbs free energy, and the associated critical parameters. Particular attention is paid to how the cloud-of-strings parameter, the magnetic charge and the quintessence field influence the resulting thermodynamic behaviour. A divergence in the heat capacity marking the boundary of local thermodynamic stability is identified from the heat-capacity analysis. The equation of state is further examined using the standard inflection-point conditions. For the representative parameter set considered in this work, the resulting mathematical critical solution has negative critical temperature and pressure and therefore lies outside the physical thermodynamic domain. Hence, no physically admissible Van der Waals-type critical point is obtained for the chosen parameters. Furthermore, the thermodynamic geometry is investigated using the HPEM metric, whose Ricci scalar provides an independent geometric characterization of the phase-transition structure. The results demonstrate that the cloud-of-strings parameter, magnetic charge, and quintessence field significantly influence the thermodynamic stability and phase structure of the BH, whereas the Tsallis entropy modifies the quantitative thermodynamic behaviour while preserving the overall qualitative phase characteristics.
Chromosome maps (ChMs) reveal multiple stellar populations in globular clusters (GCs), but radial trends can depend on how overlapping structures are partitioned. We analyse 56 Galactic GCs with Hubble Space Telescope UV Globular Cluster Survey (HUGS) photometry, separating the stability of star-by-star Gaussian-mixture assignments from that of radial statistics. Strict two-family assignments are stable in only 11/55 eligible clusters, whereas the posterior-weighted radial contrast is reproducible for 34/55. In this radial-stability sample, none of four pre-specified broad-family tests shows a robust association with compactness or half-mass relaxation time. By contrast, the label-free absolute median-radius separation between the lowest and highest 30 per cent of normalized ChM pseudocolour increases with compactness (N=34, ρ=0.500, permutation p=0.00256) and remains positive after F814W matching and common-footprint restrictions. Secondary tests show no comparable monotonic ordering with remaining-mass fraction, a present-day dynamical-age proxy, or the atlas-based global second-generation fraction. Larger amplitudes instead occur at greater compactness, higher central density, and shorter core-relaxation time. Because these central variables are strongly collinear, we interpret them as a common structural-state axis rather than unique causal drivers. Thus, the magnitude—not a universal direction—of extreme-tail radial differentiation is linked to present-day central structural state.
We examine the impacts of dark matter (DM) on the observables of the neutron star (NS). The interaction of DM with nucleons is mediated by axionlike particles (ALPs), and the DM-admixed NS (DNS) is formulated in the framework of the relativistic mean field (RMF) formalism. The effects of the DM on the NS are characterized by two parameters: DM Fermi momentum (qf) and DM mass (mχ). By varying these two parameters, we investigate how the NS’s mass, radius, and tidal deformability are altered. Furthermore, we study how the ALP-mediated DM impacts the stability of the NS through the analysis of radial oscillations. In addition, the nonradial oscillation has been investigated by calculating its fundamental mode frequency in the DNS and analyzed how the ALP-mediated DM modifies its behavior.
Globally self-gravitating accretion disks in active galactic nuclei (AGN) have been frequently discussed in the literature, but never observed. Few dozen mega-masering accretion disks in AGN have been detected, which display a clear Keplerian rotation on scales of 0.1-1 pc, allowing to estimate their masses within the sphere of influence (SoI) of the central supermassive black holes (SMBHs) to be smaller by more than a factor of 10, compared with the parent SMBH masses. Furthermore, the stellar components, deep inside the SoI, are dwarfed by the SMBH masses of M_BH few X 10^6 - few X 10^7 Mo. Theoretically, no limit exists on sizes and masses of gaseous disks in AGN, which in principle, can exceed masses of their central compact objects. We analyze instabilities which can operate in gaseous disks, i.e., fragmentation for a locally dominant self-gravity and spontaneous breaking of axial symmetry for the globally self-gravitating disks. We invoke the gas response to the latter instability which leads to gravitational collapse, leaving a negligible mass behind and dynamically stable remnants. Consequently, the characteristic timescale for globally self-gravitating disks to exist in AGN should not exceed few rotations, t_phi 10^3-4 yrs for M_BH 10^6-8 Mo. Disk rebuilding is expected to be > 10^7 yrs, meaning that probability of finding is < 10^-3, which explains their lack of detection. We conclude that observed sub-parsec disks in AGN, at least the Keplerian masering ones, can be remnants of globally self-gravitating accretion disks, and the instability timescale can be related to the duty cycle of AGN, t_duty 10t_phi 10^4-5 yr.
The galaxy size–mass relation (SMR) is a key scaling relation used to constrain the physical processes that build galaxy structure, yet it is almost always measured in a single rest-frame optical band, where the light traces the bulk of the old stellar mass. Tracing younger populations with flux-weighted ages of ∼100–500 Myr and low-metallicity stars, the rest-frame near-ultraviolet opens a new stellar window on this scaling relation. Because each process redistributes the light of young and old stars differently, the same mechanism shifts the slope and zero point of the SMR by different amounts in the two wavelength regimes. Here we review and synthesize the effects of main physical processes on the form of the SMR for star-forming and quiescent galaxies in the rest-UV and optical. For each process, we start from its underlying physics, the galaxy stellar masses it affects, and the light it adds/removes/rearranges, anchoring the predictions to observations and simulations. We validate the predicted imprints with forward Monte Carlo modelling. The two-wavelength view breaks several degeneracies that single-band analyses cannot, most notably between minor mergers, dry major mergers, and adiabatic expansion. These results motivate joint rest-UV and optical SMR measurements with current and upcoming wide-field imaging surveys.
