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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Nonthermal axion dark radiation and constraints
AU - Mazumdar, Anupam
AU - Qutub, Saleh
AU - Saikawa, Ken'ichi
N1 - © 2016 American Physical Society
PY - 2016/9/22
Y1 - 2016/9/22
N2 - The Peccei-Quinn mechanism presents a neat solution to the strong CPproblem. As a by-product, it provides an ideal dark matter candidate, “the axion”, albeit with a tiny mass. Axions therefore can act as dark radiation if excited with large momenta after the end of inflation. Nevertheless, the recent measurement of relativistic degrees of freedom from cosmic microwave background radiation strictly constrains the abundance of such extra relativistic species. We show that ultrarelativistic axions can be abundantly produced if the Peccei-Quinn field was initially displaced from the minimum of the potential. This in lieu places an interesting constraint on the axion dark matter window with large decay constant which is expected to be probed by future experiments. Moreover, an upper bound on the reheating temperature can be placed, which further constrains the thermal history of our Universe.
AB - The Peccei-Quinn mechanism presents a neat solution to the strong CPproblem. As a by-product, it provides an ideal dark matter candidate, “the axion”, albeit with a tiny mass. Axions therefore can act as dark radiation if excited with large momenta after the end of inflation. Nevertheless, the recent measurement of relativistic degrees of freedom from cosmic microwave background radiation strictly constrains the abundance of such extra relativistic species. We show that ultrarelativistic axions can be abundantly produced if the Peccei-Quinn field was initially displaced from the minimum of the potential. This in lieu places an interesting constraint on the axion dark matter window with large decay constant which is expected to be probed by future experiments. Moreover, an upper bound on the reheating temperature can be placed, which further constrains the thermal history of our Universe.
U2 - 10.1103/PhysRevD.94.065030
DO - 10.1103/PhysRevD.94.065030
M3 - Journal article
VL - 94
JO - Physical Review D
JF - Physical Review D
SN - 1550-7998
IS - 6
M1 - 065030
ER -