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SUMMARY:Dr. Kiyoharu Kawana "[CTP Seminar] Can QCD Axion explain the CMB a
 nisotropy?" (Host: Sunghoon Jung)
DTSTART;VALUE=DATE-TIME:20200910T070000Z
DTEND;VALUE=DATE-TIME:20200910T083000Z
DTSTAMP;VALUE=DATE-TIME:20260730T105403Z
UID:indico-event-118@sshep.snu.ac.kr
DESCRIPTION:*Speaker : Dr. Kiyoharu Kawana (Center for Theoretical Physics
 \, SNU)\n\n \n\n*Abstract : \n\nIt is usually believed that the anisotro
 py of cosmic microwave background (CMB) is explained by the fluctuation o
 f inflaton produced during cosmic inflation. However\, this is not an uni
 que scenario. In this talk\, I discuss a possibility that the anisotropy 
 is dominantly generated by the primordial fluctuations of QCD axion under 
 a circumstance that inflaton’s perturbation is too small to explain the 
 anisotropy. \n\nThe following conditions must be satisfied in this scenar
 io: (i) sufficient amplitudes of the CMB anisotropy (ii) isocurvature cons
 traint and (iii) non-Gaussianity constraint. By carefully studying those c
 onditions\, I show that a large energy fraction \\Omega_A of the axion i
 s necessary at the QCD phase transition when the axion-potential is genera
 ted\, but simultaneously\, it must become tiny at the present era due to t
 he isocurvature constraint. \n\nThus\, an additional scenario of the earl
 y universe\, such as thermal inflation\, is inevitable to dilute the axion
 s. I will also talk such a scenario if time permits. \n\nhttps://sshep.sn
 u.ac.kr/event/118/
LOCATION:B56 521
URL:https://sshep.snu.ac.kr/event/118/
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