Lattice effective-theory simulations give new SU(2)/SU(3) sphaleron rates for T = 0.6 GeV-10^15 GeV and show the soft magnetic sector contributes roughly half the thermal axion production rate at the electroweak scale and dominates below it.
Thermal axion production at hard and soft momenta
6 Pith papers cite this work, alongside 11 external citations. Polarity classification is still indexing.
6
Pith papers citing it
11
external citations · Pith
abstract
Hot axions, thermally produced in the Early Universe, would contribute to dark radiation and are thus subject to present and future constraints from $N_{\rm eff}$. In this paper we quantify the contribution to $N_{\rm eff}$ and its uncertainty in models with axion-gluon couplings from thermal dynamics above the QCD transition. In more detail, we determine the leading-order thermal axion production rate for axion momenta of the order of the temperature adopting three different schemes for the incorporation of the collective dynamics of soft gluons. We show how these three schemes extrapolate differently into the regime of softer axion production, thus giving us a first quantitative handle on the theory uncertainty of the rate. Upon solving the Boltzmann equation, we find that this theory uncertainty translates to an uncertainty of order 0.002 for the contribution to $N_{\rm eff}$ prior to the QCD crossover. The uncertainty from common momentum-averaged approximations to the Boltzmann equation is smaller. We also discuss how QCD transition dynamics would need to be integrated into our results and we show how existing rate determinations in the literature based on gauge-dependent resummations are problematic.
citation-role summary
background 3
citation-polarity summary
roles
background 3representative citing papers
HTL computation of soft axion rates shows interpolation between k=0 and k≈ω, raising ΔN_eff from ~0.03 to ~0.04 for light QCD axions at fa=4×10^8 GeV.
Authors formulate prescriptions for KLN cancellations of t-channel divergences in an unstable-particle model, showing scheme-independent results and steps toward finite inclusive observables.
Thermal corrections to reheating and freeze-in DM production rates are generally small in the computable regime but can be large in constructed counter-examples.
A mini-review of axion phenomenology showing how light bosons can account for dark matter, drive cosmic acceleration, or contribute to relativistic backgrounds in the early and late Universe.
A tutorial deriving cosmological perturbation equations from inflation through reheating, with explicit gauge-invariant computations and Python scripts.
citing papers explorer
-
Revisiting the sphaleron and axion production rates in QCD at high temperatures
Lattice effective-theory simulations give new SU(2)/SU(3) sphaleron rates for T = 0.6 GeV-10^15 GeV and show the soft magnetic sector contributes roughly half the thermal axion production rate at the electroweak scale and dominates below it.
-
Energy and momentum dependence of the soft-axion interaction rate
HTL computation of soft axion rates shows interpolation between k=0 and k≈ω, raising ΔN_eff from ~0.03 to ~0.04 for light QCD axions at fa=4×10^8 GeV.
-
Unitarity Cuts, t-channel Divergences and the KLN Theorem for Unstable Particles
Authors formulate prescriptions for KLN cancellations of t-channel divergences in an unstable-particle model, showing scheme-independent results and steps toward finite inclusive observables.
-
Thermal effects on Dark Matter production during cosmic reheating
Thermal corrections to reheating and freeze-in DM production rates are generally small in the computable regime but can be large in constructed counter-examples.
-
Axions as Dark Matter, Dark Energy, and Dark Radiation
A mini-review of axion phenomenology showing how light bosons can account for dark matter, drive cosmic acceleration, or contribute to relativistic backgrounds in the early and late Universe.
-
From inflation to hot big bang -- a tutorial on cosmological perturbations
A tutorial deriving cosmological perturbation equations from inflation through reheating, with explicit gauge-invariant computations and Python scripts.