The effects of non-helical component of hypermagnetic field on the evolution of the matter-antimatter asymmetry, vorticity, and hypermagnetic field

TL;DR

This paper investigates how non-helical hypermagnetic fields influence the evolution of matter-antimatter asymmetry, vorticity, and hypermagnetic fields in the early Universe, revealing mechanisms for their generation and amplification across different initial conditions.

Contribution

It introduces a comprehensive analysis of the impact of non-helical hypermagnetic components on early Universe asymmetries and vorticity, including three distinct scenarios with new insights into their interplay.

Findings

Helicity can be generated and amplified from non-helical fields via chiral effects.

Vorticity and asymmetry can be produced and enhanced by hypermagnetic fields.

Final vorticity values depend on initial hypermagnetic field strength, regardless of initial asymmetry.

Abstract

We study the evolution of the matter-antimatter asymmetry ({\eta}), the vorticity, and the hypermagnetic field in the symmetric phase of the early Universe, and in the temperature range 100 GeV < T < 10 TeV. We assume a configuration for the hypermagnetic field which includes both helical and non-helical (Bz) components. Consequently, the hypermagnetic field and the fluid vorticity can directly affect each other, the manifestations of which we explore in three scenarios. In the first scenario, we show that in the presence of a small vorticity and a large {\eta}eR, helicity can be generated and amplified for an initially strong Bz. The generation of the helical seed is due to the chiral vortical effect (CVE) and/or the advection term, while its growth is mainly due to the chiral magnetic effect (CME) which leads to the production of the baryon asymmetry, as well. The vorticity saturates to a nonzero value which depends on Bz, even in the presence of the viscosity, due to the back-reaction of Bz on the plasma. Increasing the initial vorticity, makes the values of the helicity, {\eta}s, and vorticity reach their saturation curves sooner, but does not change their final values at the onset of the electroweak phase transition. The second scenario is similar to the first except we assume that all initial {\eta}s are zero. We find that much higher initial vorticity is required for the generation process. In the third scenario, we show that in the presence of only a strong hypermagnetic field, {\eta}s and vorticity can be generated and amplified. Increasing the initial helicity, increases the final {\eta}s and vorticity. We find that although the presence of a nonzero initial Bz is necessary in all three scenarios, its increase only increases the final values of vorticity.