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SUMMARY:Dynamically generated tilt of isocurvature fluctuations
DTSTART:20260225T103000Z
DTEND:20260225T113000Z
DTSTAMP:20260406T151000Z
UID:indico-event-1623355@indico.cern.ch
DESCRIPTION:Speakers: Saarik Kalia (University of Minnesota)\n\n Light sca
 lar fields acquire isocurvature fluctuations during inflation. While these
  fluctuations could lead to interesting observable signatures at small sca
 les\, they are strongly constrained on large scales by cosmic microwave ba
 ckground observations. When the mass of the scalar is much lighter than th
 e inflationary Hubble scale\, $m\\ll H_I$\, the spectrum of these fluctuat
 ions is flat. Meanwhile\, if $m\\gg H_I$\, the fluctuations are suppressed
 . A blue-tilted isocurvature spectrum which exhibits enhanced structure on
  small scales but avoids observational constraints on large scales therefo
 re requires a coincidence of scales $m\\sim H_I$ for a free massive scalar
 . In this talk\, I will show that if a scalar field possesses a nontrivial
  potential\, its inflationary dynamics naturally cause this condition to b
 e satisfied\, and so a blue-tilted spectrum is generically expected for a 
 large class of potentials. Specifically\, if its potential $V$ exhibits a 
 region which satisfies the slow-roll condition $V''<3H_I^2$\, the scalar c
 ondensate will spend most of inflation close to the boundary of this regio
 n\, so that its effective mass is typically close to $H_I$. The resulting 
 blue tilt is inversely proportional to the number of $e$-folds of inflatio
 n prior to horizon crossing. If the scalar is long-lived\, this mechanism 
 leads to an attractor prediction for its relic abundance\, which is insens
 itive to initial conditions of the scalar. In particular\, a scalar field 
 with quartic self-interactions can achieve the correct abundance to consti
 tute all of the dark matter for a wide range of masses. I will show the re
 lationship between the mass and self-coupling of quartic dark matter predi
 cted by this mechanism.\n\nhttps://indico.cern.ch/event/1623355/\n\nZoom: 
 https://cern.zoom.us/j/66371577801?pwd=TjMvLzlFZTY2QXlQMTBmWkcxVm9TUT09
LOCATION:4/2-011 - TH common room (CERN)
URL:https://indico.cern.ch/event/1623355/
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