Is non-particle dark matter equation of state parameter evolving with time?

Recently, the so-called Hubble Tension, i.e. the mismatch between the local and the cosmological measurements of the Hubble parameter, has been resolved when non-particle dark matter is considered which has a negative equation of state parameter ($$\omega \approx -\,0.01$$ ω ≈ - 0.01 ). We investigate if such a candidate can successfully describe the galactic flat rotation curves. It is found that the flat rotation curve feature puts a stringent constraint on the dark matter equation of state parameter $$\omega $$ ω and $$\omega \approx -\,0.01$$ ω ≈ - 0.01 is not consistent with flat rotational curves, observed around the galaxies. However, a dynamic $$\omega $$ ω of non-particle dark matter may overcome the Hubble tension without affecting the flat rotation curve feature.

Distribution of Baryonic and Dark Matter in Spiral Galaxies

In the present paper, the distributions of baryonic and dark matter are derived for 24 northern sky spiral galaxies. The baryonic mass surface density profile is derived, and the component of the galaxies' observed rotation due to the baryons (stars and gas) is computed. Thus, the baryonic rotation curve of each sampled galaxy is separated from the observed rotation curve given in data base (Stapehane Courteau).

Galactic rotation curve and dark matter according to gravitomagnetism

Historically, the existence of dark matter has been postulated to resolve discrepancies between astrophysical observations and accepted theories of gravity. In particular, the measured rotation curve of galaxies provided much experimental support to the dark matter concept. However, most theories used to explain the rotation curve have been restricted to the Newtonian potential framework, disregarding the general relativistic corrections associated with mass currents. In this paper it is shown that the gravitomagnetic field produced by the currents modifies the galactic rotation curve, notably at large distances. The coupling between the Newtonian potential and the gravitomagnetic flux function results in a nonlinear differential equation that relates the rotation velocity to the mass density. The solution of this equation reproduces the galactic rotation curve without recourse to obscure dark matter components, as exemplified by three characteristic cases. A bi-dimensional model is developed that allows to estimate the total mass, the central mass density, and the overall shape of the galaxies, while fitting the measured luminosity and rotation curves. The effects attributed to dark matter can be simply explained by the gravitomagnetic field produced by the mass currents.

Galactic Evolution Showing a Constant Circulating Speed of Stars in a Galactic Disc without Requiring Dark Matter

It is an unsolved mystery that the rotation velocity of a galactic disc is same at any radial distances. The presence of dark matter is expected, but not observed. Here we propose a novel scheme for the evolution of the initial cosmic energy to current galaxies. According to the energy circulation theory, which we previously reported, the fundamental force works based on momentums. Antiparallel movements of energy pieces form a circulation. Due to the space expansion, the initial energy circulations separate and decompose to smaller level circulations; to galactic seeds, stellar seeds, and smallest energy circulations. The internal circulating velocity of a galactic seed is inherited to the circulating speed of stellar seeds in a ring. The intra-circulation interaction by the fundamental force keeps the stellar seeds to circulate at the initial speed, which does not alter by the space expansion. The new scheme meets the galaxy rotation curve without requiring dark matter.