Babur Mirza and colleagues presented a general relativistic mechanism for accelerated cosmic expansion and the Hubble’s constant. They showed that spacetime vorticity coupled to the magnetic field density in galaxies causes the galaxies to recede from one another at a rate equal to the Hubble’s constant.
Accelerated expansion of the universe, as observed, for example, in the cosmological redshift measurements using type-Ia supernovae (SNe Ia) as standard candles, implies the need for an expansion energy effective at least up to the Mpc scale. A number of independent observations (including the SNe Ia redshift, the Hubble’s constant measurements, the cosmic microwave background (CMB), baryon acoustic oscillations, and various cosmological probes), have measured the contributions of matter and the cosmological constant to the energy density of the universe, providing an accurate measurement of the cosmic acceleration. However the amount of energy for this acceleration implies a hidden or dark form of energy which is approximately three times of the observed gravitational mass-energy density in the universe.
Within Einstein’s general theory of relativity, the observed expansion rate can be accounted for by including a cosmological constant, whose origin remains somewhat mysterious. In this context various mechanisms have been postulated, including new forms of hypothetical particles, or modifications of the Newtonian-Einsteinian law of gravitation at large distances, among others. However these theories are specialized in the sense that they fail to account for other observed features of the universe, such as the high degree of isotropy in CMB, or even some feature of the expansion, such as the correct value of the Hubble’s constant.
Now, Babur and colleagues in their work showed that the specific form of the cosmological constant, hence cosmic acceleration, which can be described by spacetime vorticity, is generated by galactic rotations. They showed that this vorticity coupled to the local (galactic) magnetic field provides the requisite push (repulsive energy) causing the individual galaxies to recede at an accelerated rate. They are therefore led to an oscillatory universe, where expansion and conversely contraction rate is determined by local spacetime vorticity, rather than global geometry (curvature) of the spacetime.
“To recapitulate we remark that, within the above model of the accelerated expansion of the universe, local spacetime vorticity and magnetic field energy generation within galaxies and galactic clusters act as the feedback mechanism for expansion. Thus, contrary to some recent suggestions that accelerated expansion must imply a violation of the law of conservation of energy, we see that energy conservation remains strictly valid not only locally but globally as well. The continued universal acceleration depends on the energy generation within galaxies, which in turn is determined by accretion rate in galactic nuclei.”, said Babur.
Friends, conversion of matter-energy density into the magnetic field energy under such conditions can only take a finite amount of time, hence the magnetic field driven acceleration cannot continue indefinitely for a finite total mass. Since the acceleration aB ∼ B’², where B’² is the magnetic energy density per unit volume, they saw that with the decreasing feedback magnetic field, universal acceleration after reaching an maximum will gradually decrease. With the decrease of Magnetic energy generation via accretion, a gradual deacceleration under gravitational attraction is likely to cause cosmic contraction. They therefore proposed that they have an oscillatory universe, where magneto-vorticity coupling rather than global spacetime curvature causes the expansion and contraction phases.
According to Babur, “A very high degree of entropy must have existed at the early stage of the universe, as inferred from the Planckian shape of the CMB radiation. This raises the paradox for other cosmological models, since entropy should decrease closer to the initial singularity (big bang). Our model implies that this must be so due to the expansion started before the cross-over R = Rs, where Rs is Schwarzschild singularity. Subsequently, as this expansion (inflation) stops, and matter formation starts, expansion under spacetime vorticity must now cause matter entropy to gradually increase with time. As deduced in our paper, this explains the high isotropy and the Planckian profile of the CMB spectrum, carrying the imprint of this initial inflation over R > Rs.”
Reference: Babur M. Mirza, “Can accelerated expansion of the universe be due to spacetime vorticity?”, Modern Physics Letters A, Vol. 33, No. 40, 1850240 (2018). https://www.worldscientific.com/doi/abs/10.1142/S0217732318502401 https://doi.org/10.1142/S0217732318502401
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