Axion Kinetic Misalignment and Parametric Resonance from Inflation. (arXiv:2004.00629v1 [hep-ph])

<a href="http://arxiv.org/find/hep-ph/1/au:+Co_R/0/1/0/all/0/1">Raymond T. Co</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Hall_L/0/1/0/all/0/1">Lawrence J. Hall</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Harigaya_K/0/1/0/all/0/1">Keisuke Harigaya</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Olive_K/0/1/0/all/0/1">Keith A. Olive</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Verner_S/0/1/0/all/0/1">Sarunas Verner</a>

Axion cold dark matter from standard misalignment typically requires a decay

constant $f_a~gtrsim~10^{11}$ GeV. Kinetic misalignment and parametric

resonance easily allow lower values of $f_a$ when the radial Peccei-Quinn (PQ)

symmetry breaking field takes large initial values. Here, we consider the

effects of inflation on kinetic misalignment and parametric resonance. We

assume that the initial PQ field value is determined by quantum fluctuations,

and is set by the Hubble parameter during inflation, $H_I$, and the PQ field

mass. PQ field oscillations begin before or after the completion of reheating

after inflation at a temperature $T_R$. We determine the range of $f_a$ and the

inflationary parameters $(H_I, T_R)$ consistent with axion dark matter for a

quartic potential for the PQ field. We find that $4times 10^8$ GeV $< f_a <

10^{11}$ GeV can consistently produce axion dark matter. A significant portion

of the allowed parameter space predicts rare kaon decays, $K_L rightarrow

(pi^0 + rm{missing ; energy})$, and/or suppression of structure formation on

small scales.

Axion cold dark matter from standard misalignment typically requires a decay

constant $f_a~gtrsim~10^{11}$ GeV. Kinetic misalignment and parametric

resonance easily allow lower values of $f_a$ when the radial Peccei-Quinn (PQ)

symmetry breaking field takes large initial values. Here, we consider the

effects of inflation on kinetic misalignment and parametric resonance. We

assume that the initial PQ field value is determined by quantum fluctuations,

and is set by the Hubble parameter during inflation, $H_I$, and the PQ field

mass. PQ field oscillations begin before or after the completion of reheating

after inflation at a temperature $T_R$. We determine the range of $f_a$ and the

inflationary parameters $(H_I, T_R)$ consistent with axion dark matter for a

quartic potential for the PQ field. We find that $4times 10^8$ GeV $< f_a <

10^{11}$ GeV can consistently produce axion dark matter. A significant portion

of the allowed parameter space predicts rare kaon decays, $K_L rightarrow

(pi^0 + rm{missing ; energy})$, and/or suppression of structure formation on

small scales.

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