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SUMMARY:Symmetry protection of superhorizon perturbations from small-scale
  loops
DTSTART:20260602T070000Z
DTEND:20260602T083000Z
DTSTAMP:20260531T195400Z
UID:indico-event-409@indico.kias.re.kr
DESCRIPTION:Speakers: Ryusuke Jinno (Kobe University)\n\nTitle: Symmetry p
 rotection of superhorizon perturbations from small-scale loops\nSpeaker: R
 yusuke Jinno\nAbstract: Small-scale scalar perturbations can be strongly 
 enhanced in inflationary scenarios relevant to primordial black holes and 
 induced gravitational waves. A central question is whether such enhanced m
 odes can feed back into superhorizon scalar and tensor perturbations throu
 gh scale-invariant one-loop corrections. I will discuss this problem using
  the Schwinger–Keldysh formalism in the r/a basis and the corresponding 
 soft effective field theory obtained by integrating out hard scalar modes.
  For tensor perturbations\, the dangerous operator in the soft tensor EFT 
 is forbidden by the residual spatial diffeomorphism invariance of general 
 relativity. For scalar perturbations\, the dilatation symmetry of zeta\, t
 ogether with the tadpole cancellation condition and the associated symmetr
 y-preserving counterterm\, removes the corresponding scale-invariant contr
 ibution. I will also explain how the explicit one-loop cancellation follow
 s from an identity among statistical and retarded Green’s functions\, va
 lid for arbitrary time-dependent inflationary backgrounds. These results s
 how that\, including transient ultra-slow-roll scenarios\, enhanced small-
 scale scalar perturbations do not generate scale-invariant one-loop correc
 tions to the large-scale scalar or tensor power spectra in the soft limit.
   \nParticle Physics is inviting you to a scheduled Zoom meeting.Join Zoo
 m Meetinghttps://kias-re-kr.zoom.us/j/84995441726?pwd=ruay1lNAd4f19W4d3lSC
 cu17W2gWO9.1Meeting ID: 849 9544 1726Passcode: 633003\n\nhttps://indico.ki
 as.re.kr/event/409/
LOCATION:Room 1423 (KIAS)
URL:https://indico.kias.re.kr/event/409/
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