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SUMMARY:Gravitational-Wave Imprints of Disappearing Matter in the Early Un
 iverse
DTSTART;VALUE=DATE-TIME:20260821T060000Z
DTEND;VALUE=DATE-TIME:20260821T070000Z
DTSTAMP;VALUE=DATE-TIME:20260815T045900Z
UID:indico-event-5239@indico-tdli.sjtu.edu.cn
DESCRIPTION:Speakers: Xiaohan Ma（马潇汉） (University of Science and
  Technology of China & IPMU)\n\nAbstract:An early matter-dominated era can
  be generated by nonrelativistic populations such as ultralight primordial
  black holes\, Q-balls\, or oscillons. If they disappear before Big Bang n
 ucleosynthesis\, the Universe returns to radiation domination\, and the as
 sociated transition can source a stochastic background of scalar-induced g
 ravitational waves. We develop a general framework connecting the microsco
 pic law governing this disappearance to the transition dynamics and its gr
 avitational-wave signal.Using evaporating ultralight primordial black hole
 s as a concrete example\, we show that a finite-width mass distribution le
 ads to a universal transition qualitatively different from that of a monoc
 hromatic population. Near the evaporation endpoint\, the mass loss of indi
 vidual black holes is accompanied by the continuous depletion of the survi
 ving population. This evolution is controlled by the evaporation law and i
 s largely insensitive to the detailed initial mass distribution. It imprin
 ts a characteristic high-frequency tail on the gravitational-wave spectrum
 \, whose asymptotic behavior directly encodes the underlying evaporation l
 aw and may therefore probe black-hole evaporation physics. At the same tim
 e\, this tail is strongly suppressed relative to the monochromatic predict
 ion\, reducing the total gravitational-wave energy density and substantial
 ly relaxing observational constraints on primordial-black-hole-driven earl
 y matter domination.Speaker Bio:Xiao-Han Ma recently received his PhD in a
 strophysics from the University of Science and Technology of China and wil
 l soon join the Asia Pacific Center for Theoretical Physics as a postdocto
 ral researcher. During his doctoral studies\, he was also a joint doctoral
  student at the Kavli Institute for the Physics and Mathematics of the Uni
 verse\, University of Tokyo. His research focuses on theoretical cosmology
  and the early Universe\, particularly non-perturbative primordial non-Gau
 ssianity\, primordial black-hole formation\, and cosmological gravitationa
 l waves. He develops analytical and numerical approaches to connect small-
 scale primordial physics with observable signatures\, including gravitatio
 nal-wave signals associated with evaporating ultralight primordial black h
 oles.Alternative online link: https://meeting.tencent.com/dm/tKaMDGwuLtMF
 ID: 502266669 (No Password)\n\nhttps://indico-tdli.sjtu.edu.cn/event/523
 9/
LOCATION:Tsung-Dao Lee Institute/N6F-N600 - Lecture Room (Tsung-Dao Lee In
 stitute)
URL:https://indico-tdli.sjtu.edu.cn/event/5239/
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