Hubble expansion as a curvature of space

By considering the expansion of space as an additional component of general relativity, a model is described that adds a Hubble curvature term as a new solution to the general equation. Correlation with the $\Lambda$CDM model was assessed using the extensive type~Ia supernovae (SNe~Ia) data with redshift corrected to the CMB, and recent baryonic acoustic oscillation (BAO) measures. For the SNe~Ia data, the modified GR and $\Lambda$CDM models differed by $^{+0.11}_{-0.15}~\mu_B$~mag. over $z_{cmb}=0.01-1.3$, with overall weighted RMS errors of $\pm0.136$ and $\pm0.151$ $\mu_B$~mag respectively. For the BAO measures, the weighted RMS errors were $\pm0.034$ and $\pm0.085$ Mpc with $H_0=67.6\pm0.25$ for the modified GR and $70.0\pm0.25$ for the $\Lambda$CDM models, over the range $z=0.106-2.36$. The derived GR metric accurately describes both the SNe Ia and the baryonic acoustic oscillation (BAO) observations without requiring dark matter or $w$-corrected dark energy while allowing the spatial term to remain flat, suggesting that the standard metric may accept an additional term for the curvature of space due to its Hubble expansion.Comment: 11 pages, 7 figures, submitted to Results in Physic

Entropy and Mass Distribution in Disc Galaxies

The relaxed motion of stars and gas in galactic discs is well approximated by a rotational velocity that is a function of radial position only, implying that individual components have lost any information about their prior states. Thermodynamically, such an equilibrium state is a microcanonical ensemble with maximum entropy, characterised by a lognormal probability distribution. Assuming this for the surface density distribution yields rotation curves that closely match observational data across a wide range of disc masses and galaxy types, and provides a useful tool for modelling the theoretical density distribution in the disc. A universal disc spin parameter emerges from the model, giving a tight virial mass estimator with strong correlation between angular momentum and disc mass, suggesting a mechanism by which the proto-disc developed by dumping excess mass to the core, or excess angular momentum to a satellite galaxy. The baryonic-to-dynamic mass ratio for the model approaches unity for high mass galaxies, but is generally $<1$ for low mass discs, and this discrepancy appears to follow a similar relationship to that shown in recent work on the radial acceleration relation (RAR). Although this may support Modified Newtonian Dynamics (MOND) in preference to a dark matter (DM) halo, it does not exclude undetected baryonic mass or a gravitational DM component in the disc.Comment: 16 pages, 4 figures. Invitation paper for "Debate on the Physics of Galactic Rotation and the Existence of Dark Matter". Accepted Jan 202

Re-orientations : East Asian popular cultures in contemporary Vietnam

Vietnamese-Australians live in Australia, a large island continent. The physical contrast between Vietnam and Australia is remarked upon by many Vietnamese in their migration stories. Whereas Vietnam is remembered as an interlinked sensual and social world, Australia is often viewed as a harsh, spacious, empty, dry continent. Australia is located in a regional Asian context, but this location has always been culturally and politically problematic, as it historically attempted to define itself as a "white" European nation in the Southern Hemisphere (Ang, 2000, p. xiii; McNamara &amp; Coughlan, 1997, p. 1). During the Gold Rush period in the late 1800s, when there was widespread opposition to Chinese labor, Australia implemented a "White Australia" policy, although there were historically a significant number of Australians of Asian background. This exclusionary immigration policy was effectively overturned in the 1970s with the acceptance of a large number of refugees from Vietnam, Cambodia, and Laos in 1975. Vietnamese-Australians live predominantly in urban areas with over three quarters living in Sydney and Melbourne, the two largest cities. Within these two cities they are also highly concentrated in ethnically diverse suburbs, most living in areas with more than 1,000 residents born in Vietnam (Viviani, 1996, p. 49). However, Jupp (Jupp et al., 1990; Jupp, 1993) has argued that these areas are also zones of transition, with much movement in and out