Chiral charge erasure via thermal fluctuations of magnetic helicity

Journal Article · Wed May 11 04:00:00 EDT 2016 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2016/05/029· OSTI ID:22572076

Long, Andrew J. ^[1]; Sabancilar, Eray ^[2]

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1. Kavli Institute for Cosmological Physics, University of Chicago,Chicago, Illinois 60637 (United States)
2. Institut de Théorie des Phénoménes Physiques, Ecole Polytechnique Fédérale de Lausanne,CH-1015 Lausanne (Switzerland)

We consider a relativistic plasma of fermions coupled to an Abelian gauge field and carrying a chiral charge asymmetry, which might arise in the early Universe through baryogenesis. It is known that on large length scales, λ≳1/(αμ{sub 5}), the chiral anomaly opens an instability toward the erasure of chiral charge and growth of magnetic helicity. Here the chemical potential μ{sub 5} parametrizes the chiral asymmetry and α is the fine-structure constant. We study the process of chiral charge erasure through the thermal fluctuations of magnetic helicity and contrast with the well-studied phenomenon of Chern-Simons number diffusion. Through the fluctuation-dissipation theorem we estimate the amplitude and time scale of helicity fluctuations on the length scale λ, finding δ H∼λT and τ∼αλ{sup 3}T{sup 2} for a relativistic plasma at temperature T. We argue that the presence of a chiral asymmetry allows the helicity to grow diffusively for a time t∼T{sup 3}/(α{sup 5}μ{sub 5}{sup 4}) until it reaches an equilibrium value H∼μ{sub 5}T{sup 2}/α, and the chiral asymmetry is partially erased. If the chiral asymmetry is small, μ{sub 5}

• Sponsoring Organization: SCOAP3, CERN, Geneva (Switzerland)
• OSTI ID: 22572076
• Journal Information: Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 05 Vol. 2016; ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ASYMMETRY
CHIRALITY
COSMOLOGY
FINE STRUCTURE
FLUCTUATIONS
GAUGE INVARIANCE
HELICITY
MAGNETIC FIELDS
NONLUMINOUS MATTER
RELATIVISTIC RANGE
STANDARD MODEL
U-1 GROUPS
UNIVERSE