Aspects of the Magnetogenesis in the Curved Spacetime of Rotating Astrophysical Bodies

Roy, Sourashis (2025) Aspects of the Magnetogenesis in the Curved Spacetime of Rotating Astrophysical Bodies. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Sourashis Roy (20MS053)) 20MS053_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (646kB)

Abstract

As per our present understanding, we know that our universe is magnetized at different length-scales. But, still there is no well-established mechanism to explain the origin of this wide-spread magnetic field. Many models for the magnetogenesis has been proposed. Some of them can’t produce enough seed magnetic field, that can be amplified to present day observed scale(μG range) via galactic dynamos, others invokes beyond standard model physics concepts. Biermann Astrophysical battery mechanism is probably the most successful model of magnetogenesis, till now. But, it relies on the non-alignment of density gradient and pressure gradient due to shock waves generated from the Primordial Density Fluctuations. This requires the proto-galactic plasma to be non-barotropic(i.e. pressure is not solely a function of density). But maintaining such non-barotropic nature is very difficult, due to the thermalization processes inside plasma. In this report, we explore the possibility of magnetogenesis in the rotating protogalactic cloud. Galaxies form in the process of collapse of dense molecular protogalactic clouds, which starts rotating due to angular momentum conservation. So, rotation is a universal phenomenon for galaxies. We will see that, Spin Degeneracy of fermions breaks down in the vicinity of a massive rotating body, due to frame-dragging effect. As a result of this broken degeneracy, number density of spin-up and spin-down fermions no longer remains same and as these fermions (Predominantly electrons and H-ions inside proto-galactic clouds) have non-zero magnetic moment, a Magnetic field arises due to this difference between the number density of two kinds of fermions.

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