[Paper Review] Schwinger effect, backreaction and magnetogenesis in de Sitter spacetime

Clément Stahl, She-Sheng Xue|arXiv (Cornell University)|Mar 22, 2016

Cosmology and Gravitation Theories3 citations

TL;DR

This paper investigates Schwinger pair production in de Sitter spacetime, analyzing how fermionic pairs backreact on the electromagnetic field via the Einstein-Maxwell equations. It finds that fermionic pairs suppress or leave unchanged the electric field, preventing magnetogenesis, but reports a potential enhancement for light bosons, suggesting a new route to primordial magnetogenesis.

ABSTRACT

We consider the particle-antiparticle pairs produced by both a strong electric field and de Sitter curvature. We investigate in 1+1 D the backreaction of the pairs on the electromagnetic field. To do so we describe the canonical quantization of an electromagnetic field in de Sitter space and add in the Einstein-Maxwell equation the fermionic current induced by the pairs. After solving this equation, we find that the electric field gets either damped or unaffected depending on the value of the pair mass and the gauge coupling. No enhancement of the electromagnetic field to support a magnetogenesis scenario is found. The physical picture is that the Schwinger pairs locally created screen the production and amplification of the electromagnetic field. However, if one considers light bosons created by the Schwinger mechanism, we report a solution to the Einstein-Maxwell equation with an enhancement of the electromagnetic field. This solution could be a new path to primordial magnetogenesis.

Motivation & Objective

• To study the interplay between Schwinger pair production and de Sitter curvature in 1+1 dimensions.
• To analyze the backreaction of produced fermionic pairs on the electromagnetic field in curved spacetime.
• To determine whether the backreaction can lead to electromagnetic field amplification suitable for magnetogenesis.
• To explore whether light bosons, rather than fermions, could support a viable mechanism for primordial magnetic field generation.

Proposed method

• Perform canonical quantization of the electromagnetic field in de Sitter spacetime.
• Compute the fermionic current induced by Schwinger pairs in the presence of a strong electric field.
• Include the induced current in the Einstein-Maxwell equations to model backreaction effects.
• Solve the modified Einstein-Maxwell equations numerically or analytically in 1+1 dimensions.
• Compare the evolution of the electric field for different fermion masses and gauge couplings.
• Extend the analysis to light bosons to assess their potential for field enhancement.

Experimental results

Research questions

• RQ1 Does the backreaction of Schwinger-produced fermions amplify the electromagnetic field in de Sitter spacetime?
• RQ2 How does the mass of the fermionic pairs influence the backreaction on the electric field?
• RQ3 Can the induced fermionic current lead to sustained or enhanced electromagnetic fields, supporting a magnetogenesis scenario?
• RQ4 What role does the gauge coupling play in determining the strength and sign of the backreaction?
• RQ5 Do light bosons produced via the Schwinger mechanism exhibit a different backreaction behavior that could enable electromagnetic field growth?

Key findings

• The backreaction of fermionic pairs suppresses or leaves unchanged the electric field, depending on the pair mass and gauge coupling.
• No enhancement of the electromagnetic field is observed for fermions, ruling out this mechanism for magnetogenesis.
• The local screening effect from pair production prevents field amplification and limits the growth of the electric field.
• For light bosons, a solution to the Einstein-Maxwell equations is found that exhibits electromagnetic field enhancement.
• This enhancement suggests a potential new pathway for primordial magnetogenesis via bosonic Schwinger pairs.
• The results indicate a fundamental difference in backreaction behavior between fermions and bosons in de Sitter spacetime.