244,493 research outputs found
Primordial magnetic fields
Large scale magnetic fields represent a triple point where cosmology,
high-energy physics and astrophysics meet for different but related purposes.
After reviewing the implications of large scale magnetic fields in these
different areas, the role of primordial magnetic fields is discussed in various
physical processes occurring prior to the decoupling epoch with particular
attention to the big bang nucleosynthesis (BBN) epoch and to the electroweak
(EW) epoch. The generation of matter--antimatter isocurvature fluctuations,
induced by hypermagnetic fields, is analyzed in light of a possible increase of
extra-relativistic species at BBN. It is argued that stochastic GW backgrounds
can be generated by hypermagnetic fields at the LISA frequency. The problem of
the origin of large scale magnetic fields is also scrutinized.Comment: 41 pages in Latex style, 5 figure
Three-magnetic fields
A completely new mechanism to generate the observed amount of large-scale
cosmological magnetic fields is introduced in the context of three-form
inflation. The amplification of the fields occurs via fourth order dynamics of
the vector perturbations and avoids the backreaction problem that plagues most
previously introduced mechanisms.Comment: 4 pages, 2 figures -- v2 as published (title changed in the published
version to "Cosmic magnetization in three-form inflation"
Magnetic fields
Effects of high and low gradient magnetic fields on human performance for space flight application
Biermann Mechanism in Primordial Supernova Remnant and Seed Magnetic Fields
We study generation of magnetic fields by the Biermann mechanism in the
pair-instability supernovae explosions of first stars. The Biermann mechanism
produces magnetic fields in the shocked region between the bubble and
interstellar medium (ISM), even if magnetic fields are absent initially. We
perform a series of two-dimensional magnetohydrodynamic simulations with the
Biermann term and estimate the amplitude and total energy of the produced
magnetic fields. We find that magnetic fields with amplitude
G are generated inside the bubble, though the amount of
magnetic fields generated depend on specific values of initial conditions. This
corresponds to magnetic fields of erg per each supernova
remnant, which is strong enough to be the seed magnetic field for galactic
and/or interstellar dynamo.Comment: 12 pages, 3 figure
Magnetic Field Transfer From A Hidden Sector
Primordial magnetic fields in the dark sector can be transferred to magnetic
fields in the visible sector due to a gauge kinetic mixing term. We show that
the transfer occurs when the evolution of magnetic fields is dominated by
dissipation due to finite electric conductivity, and does not occur at later
times if the magnetic fields evolve according to magnetohydrodynamics scaling
laws. The efficiency of the transfer is suppressed by not only the gauge
kinetic mixing coupling but also the ratio between the large electric
conductivity and the typical momentum of the magnetic fields. We find that the
transfer gives nonzero visible magnetic fields today. However, without possible
dynamo amplifications, the field transfer is not efficient enough to obtain the
intergalactic magnetic fields suggested by the gamma-ray observations, although
there are plenty of possibilities for efficient dark magnetogenesis, which are
experimentally unconstrained.Comment: 26 pages, 2 figure
The First Magnetic Fields
We review current ideas on the origin of galactic and extragalactic magnetic
fields. We begin by summarizing observations of magnetic fields at cosmological
redshifts and on cosmological scales. These observations translate into
constraints on the strength and scale magnetic fields must have during the
early stages of galaxy formation in order to seed the galactic dynamo. We
examine mechanisms for the generation of magnetic fields that operate prior
during inflation and during subsequent phase transitions such as electroweak
symmetry breaking and the quark-hadron phase transition. The implications of
strong primordial magnetic fields for the reionization epoch as well as the
first generation of stars is discussed in detail. The exotic, early-Universe
mechanisms are contrasted with astrophysical processes that generate fields
after recombination. For example, a Biermann-type battery can operate in a
proto-galaxy during the early stages of structure formation. Moreover, magnetic
fields in either an early generation of stars or active galactic nuclei can be
dispersed into the intergalactic medium.Comment: Accepted for publication in Space Science Reviews. Pdf can be also
downloaded from http://canopus.cnu.ac.kr/ryu/cosmic-mag1.pd
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