Theory Colloquium

Primordial Magnetic Fields: Cosmological Signatures and Improved Probes

by Pranjal Trivedi (Hamburg U.)

Europe/Berlin
build. 2a, SR2 (DESY Hamburg)

build. 2a, SR2

DESY Hamburg

Description
Magnetic fields are observed ubiquitously out to large scales in the Universe. Micro Gauss fields are seen in galaxies and clusters of galaxies. Evidence from blazar emission suggests that even the voids of the intergalactic medium could be permeated with a weak magnetic field of 10^{-16} Gauss. This motivates the idea of primordial magnetic fields from the early Universe, subsequently amplified and maintained, to explain the origin of the observed fields. After reviewing magnetic field generation and evolution, as well as its challenges, we describe some of their cosmological signatures, especially in the cosmic microwave background. We find that non-Gaussianity and tensor modes (gravitational wave background) sourced by magnetic fields are sensitive probes. Comparison with Planck limits leads to improved constraints on primordial magnetic fields. The deflection of pair beams produced by blazar TeV emission is also investigated. Finally, tracing the turbulent decay of magnetic fields across recombination can lead to baryon heating and further clarify our understanding of primordial magnetic fields.
Slides