Statistical properties of scale-invariant helical magnetic fields and applications to cosmology

Brandenburg, Axel; Durrer, Ruth; Kahniashvili, Tina; Mandal, Sayan; Yin, Weichen Winston

doi:10.1088/1475-7516/2018/08/034

Cited by 24 publications

(29 citation statements)

References 147 publications

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“…Furthermore, the vector propagators in cosmological spaces, both the massive one constructed here and the massless one left for future work, constitute fundamental building blocks for studying physical effects from the interactions of gauge fields with matter and gravity in inflation. Examples illustrating their importance are such phenomena as large scale cosmological magnetic and electric fields [7,22,30,[35][36][37][38][39][40][41], generation of gravitational waves [42][43][44][45], etc.…”

Section: Jhep09(2020)165mentioning

confidence: 99%

“…Its general solutions and their properties are given in appendix A. Here we give the solutions as, 38) where the mode function U ν given in (A.3) is, and where H (1) ν is the Hankel function of the first kind. The time-independent operatorsb † T,σ ( k) andb T,σ ( k) are introduced as initial conditions for field operators, and are chosen such that they satisfy the commutation relations for creation and annihilation operators, b 40) owing to the fact that the mode functions are normalized to the Wronskian given in (A.4), 41) and that the transverse field operators commute as in (6.26).…”

Section: Dynamics Of the Transverse Sectormentioning

confidence: 99%

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Abelian Higgs model in power-law inflation: the propagators in the unitary gauge

Glavan

Marunović²,

Prokopec

et al. 2020

J. High Energ. Phys.

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We consider the Abelian Higgs model in the broken phase as a spectator in cosmological spaces of general D space-time dimensions, and allow for the condensate to be time-dependent. We fix the unitary gauge using Dirac’s formalism for constrained systems, and then quantize the gauge-fixed system. Vector and scalar perturbations develop timedependent masses. We work out their propagators assuming the cosmological background is that of power-law inflation, characterized by a constant principal slow-roll parameter, and that the scalar condensate is in the attractor regime, scaling as the Hubble rate. Our propagators correctly reduce to known results in the Minkowski and de Sitter space limits. We use the vector propagator to compute the equal-time correlators of electric and magnetic fields and find that at super-Rubble separations the former is enhanced, while the latter is suppressed compared to the vacuum fluctuations of the massless vector field. These correlators satisfy the hierarchy governed by Faraday’s law.

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Section: Jhep09(2020)165mentioning

confidence: 99%

Section: Dynamics Of the Transverse Sectormentioning

confidence: 99%

Abelian Higgs model in power-law inflation: the propagators in the unitary gauge

Glavan

Marunović²,

Prokopec

et al. 2020

J. High Energ. Phys.

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show abstract

“…As a final remark it should be pointed out that, due to the fact that magnetic helicity is (nearly) conserved, it plays an important role in the time-evolution of magnetic fields, in particular by causing the so-called inverse cascade of energy, i.e., the transfer of magnetic energy from small to large scale fluctuations [73,115,[121][122][123]. These inverse cascades, however, do not seem to be exclusive to helical fields, as shown in recent simulations [124].…”

Section: Post-inflationarymentioning

confidence: 99%

The Gamma-ray Window to Intergalactic Magnetism

Batista

Saveliev

2021

Universe

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One of the most promising ways to probe intergalactic magnetic fields (IGMFs) is through gamma rays produced in electromagnetic cascades initiated by high-energy gamma rays or cosmic rays in the intergalactic space. Because the charged component of the cascade is sensitive to magnetic fields, gamma-ray observations of distant objects such as blazars can be used to constrain IGMF properties. Ground-based and space-borne gamma-ray telescopes deliver spectral, temporal, and angular information of high-energy gamma-ray sources, which carries imprints of the intervening magnetic fields. This provides insights into the nature of the processes that led to the creation of the first magnetic fields and into the phenomena that impacted their evolution. Here we provide a detailed description of how gamma-ray observations can be used to probe cosmic magnetism. We review the current status of this topic and discuss the prospects for measuring IGMFs with the next generation of gamma-ray observatories.

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“…Physically, turbulence can be induced at reheating by energy injection from the inflaton into the standard model particles and fields, or from bubble collisions during some (yet unknown) phase transition -the spectral energy density E M (k) has a k 4 subinertial range at large scales due to causality requirements (see Refs. [46,47]), while in the inertial range, it tends to have a Kolmogorov spectrum proportional to k −5/3 .…”

Section: Initial Conditionsmentioning

confidence: 99%

Primordial magnetic helicity evolution with a homogeneous magnetic field from inflation

Brandenburg,

Durrer,

Huang

et al. 2020

Preprint

Self Cite

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Motivated by a scenario of magnetogenesis in which a homogeneous magnetic field is generated during inflation, we study the magnetohydrodynamic evolution of the primordial plasma motions for two kinds of initial conditions -(i) a spatially homogeneous imposed field with an unlimited correlation length, and (ii) a zero flux scale-invariant statistically homogeneous magnetic field. In both cases, we apply, for a short initial time interval, monochromatic forcing at a certain wave number so that the correlation length is finite, but much smaller than the typical length scale of turbulence. In particular, we investigate the decay of non-helical and helical hydromagnetic turbulence. We show that, in the presence of an imposed magnetic field, the decay of helical and nonhelical small-scale fields can occur rapidly. This is a special property of a system with a perfectly homogeneous magnetic field, which is sometimes considered as a local approximation to a slowly varying background field. This is in a sharp contrast to the case of a statistically homogeneous magnetic field, where we recover familiar decay properties: a much slower decay of magnetic energy and a faster growth of the correlation length, especially in the case with magnetic helicity. The result suggests that a homogeneous magnetic field, if generated during inflation, should persist under the influence of small-scale fields and could be the origin of the large-scale magnetic field in the universe.

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Statistical properties of scale-invariant helical magnetic fields and applications to cosmology

Cited by 24 publications

References 147 publications

Abelian Higgs model in power-law inflation: the propagators in the unitary gauge

Abelian Higgs model in power-law inflation: the propagators in the unitary gauge

The Gamma-ray Window to Intergalactic Magnetism

Primordial magnetic helicity evolution with a homogeneous magnetic field from inflation

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