In pure axion inflation, detectable gravitational wave signals arise only in parameter regions with strong backreaction that violate the upper bound on ΔN_eff.
N-flationary magnetic fields
7 Pith papers cite this work. Polarity classification is still indexing.
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abstract
There is increasing interest in the role played by pseudo Nambu-Goldstone bosons (pNGBs) in the construction of string-inspired models of inflation. In these models the inflaton is expected to be coupled to gauge fields, and will lead to the generation of magnetic fields that can be of cosmological interest. We study the production of such fields mainly focusing on the model of N-flation, where the collective effect of several pNGBs drives inflation. Because the produced fields are maximally helical, inverse cascade processes in the primordial plasma increase significantly their coherence length. We discuss under what conditions inflation driven by pNGBs can account for the observed cosmological magnetic fields. A constraint on the parameters of this class of inflationary scenarios is also derived by requiring that the magnetic field does not backreact on the inflating background.
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Lattice simulations show that Schwinger currents saturate gauge-field production in axion inflation, yielding universal conductivity and magnetic-field values at the onset of strong backreaction.
Coupling dark photons to standard photons enables adequate primordial magnetogenesis without strong-coupling or backreaction issues.
Schwinger fermion production in axion inflation damps gauge fields, enabling observable primordial gravitational waves in LISA/ET bands while satisfying ΔN_eff limits and identifying a new damped-oscillation backreaction regime.
Constant electric fields in de Sitter require a tachyonic photon mass ~H, yielding finite positive Schwinger currents for massless fermions and scalars after on-shell renormalization.
Lattice simulations of bumpy axion U(1) inflation in the strong backreaction regime generate curvature perturbations large enough for primordial black holes to comprise all dark matter.
PBHs generated by axion inflation with gauge-field coupling can comprise all dark matter in the asteroidal mass range while producing a LISA-measurable stochastic GW background.
citing papers explorer
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Gravitational waves from axion inflation in the gradient expansion formalism. Part I. Pure axion inflation
In pure axion inflation, detectable gravitational wave signals arise only in parameter regions with strong backreaction that violate the upper bound on ΔN_eff.
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Schwinger effect in axion inflation on a lattice
Lattice simulations show that Schwinger currents saturate gauge-field production in axion inflation, yielding universal conductivity and magnetic-field values at the onset of strong backreaction.
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Dark photon -- Assisted Primordial Magnetogenesis
Coupling dark photons to standard photons enables adequate primordial magnetogenesis without strong-coupling or backreaction issues.
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Gravitational waves from axion inflation in the gradient expansion formalism. Part II. Fermionic axion inflation
Schwinger fermion production in axion inflation damps gauge fields, enabling observable primordial gravitational waves in LISA/ET bands while satisfying ΔN_eff limits and identifying a new damped-oscillation backreaction regime.
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Classical constant electric fields and the Schwinger effect in de Sitter
Constant electric fields in de Sitter require a tachyonic photon mass ~H, yielding finite positive Schwinger currents for massless fermions and scalars after on-shell renormalization.
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Lattice study of primordial black hole formation in bumpy axion inflation
Lattice simulations of bumpy axion U(1) inflation in the strong backreaction regime generate curvature perturbations large enough for primordial black holes to comprise all dark matter.
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Primordial black hole dark matter from axion inflation
PBHs generated by axion inflation with gauge-field coupling can comprise all dark matter in the asteroidal mass range while producing a LISA-measurable stochastic GW background.