Galaxies

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 ($N=34$, $\rho =0.500$, 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 believe that the origin of the universal dark energy may crucially depend on the behavior of the gravitational constant G. If G is constant throughout the universe, then the dark energy density ${\mathit{u}}_0$ is supported by the vacuum via its constant and evolving properties. On the other hand, in varying-G gravity (whose low-acceleration limit is MOND), ${\mathit{u}}_0$ is a manifestation of radial G-gradients in the source of gravity. We estimate the present-day dark energy density of the universe in these two independent cases without using conventional Planck-2018 modeling in deriving the expressions for ${\mathit{u}}_0$. The constant-G derivation uses dimensional analysis, vacuum constants, and a newly discovered evolving bridge between vacuum mechanical and electromagnetic quantities. The varying-G derivation relies on the MOND critical acceleration $a_0$, the source of gravity that falls off as ∼$r^{-2}$ at large distances r, and the assumption that the present-day energy density $u_0$ can be estimated by spatially averaging this radial profile over the MOND volume ${\displaystyle \frac{4\pi }{3}}{r}_0^3$, where and c is the speed of light in vacuum. The agreement between these two determinations and the Planck-2018 results from $\Lambda$CDM modeling is at the percent level, so that the results cannot distinguish clearly between constant-G and varying-G gravity. The analysis further indicates that the Newtonian constant $G_0$, the MOND constant $a_0$, and the Planck units of force, power, voltage, and current can be regarded as empirical vacuum constants within the proposed framework, alongside the well-known resistive properties of the vacuum, whereas charge, capacitance, inductance, and various fields are scale-dependent properties evolving in the expanding universe since the Stoney era. Ultimately, the vacuum behaves as a remarkably stiff elastic medium under stress, irrespective of the presence or absence of matter. This property has long been encoded, albeit inconspicuously, in the much discussed Tully–Fisher and Faber–Jackson relations, as well as in the Casimir effect and the field equations of General Relativity.

Rain fade is the dominant weather disturbance for high-frequency radio telescopes in the tropics, where convective storms develop within minutes and long-term statistical models such as ITU-R P.618 offer no short-term guidance. We present the first site-specific multi-horizon forecast of rain-induced signal degradation for a radio telescope in a tropical climate, built from 65 days (1249 h) of 30-s signal-to-noise ratio (SNR) telemetry from the KMITL 12-m Ku-band antenna in Bangkok, co-located with a 16-s surface weather station. An attention-based network with quantile output and a gradient-boosting ensemble forecast the apparent attenuation (the SNR loss from clear sky; a radiometric correction for rain-emitted noise yields the path attenuation) 5–60 min ahead under day-blocked cross-validation. The point skill against persistence reaches +0.13 at 60 min but is near zero at 5–15 min under rain: the slant-path signal itself leads every surface predictor, including the rain gauge by about 5 min. The forecast value appears instead at the event level. At matched false-alarm rates, quantile-based warnings detect 11 to 13 of 13 fade events with a 20–60 min median lead time, against 9 of 13 and under 20 min for reactive monitoring. A scheduling replay quantifies when forecast-based deferral beats reactive operation, and the fade climatology, lead–lag physics, and 17.7-dB (apparent) case study characterize the site itself.