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SUMMARY:Cosmological Gravitational Particle Production: Generating Sterile
  Neutrinos Dark Matter
DTSTART;VALUE=DATE-TIME:20260113T050000Z
DTEND;VALUE=DATE-TIME:20260113T070000Z
DTSTAMP;VALUE=DATE-TIME:20260512T222317Z
UID:indico-event-403@indico.itp.ac.cn
DESCRIPTION:Speaker: Fotis Koutroulis (IHEP\, CAS)\n\nAbstract: In this wo
 rk we consider cosmological gravitational production of Dirac sterile neut
 rinos as dark matter candidates during and after inflation. In the former\
 , the Higgs field experiences large quantum fluctuations driving its avera
 ge field value to the Hubble scale and above facilitating the sterile neut
 rino production. However\, the production efficiency due to classical grav
 ity still remains suppressed compared to the standard freeze-in mechanism.
  Quantum gravitational effects\, on the other hand\, are expected to break
  conformal invariance of the fermion sector by the Planck scale-suppressed
  operators irrespective of the mass. We find that such operators are very 
 efficient in fermion production immediately after inflation\, generating a
  significant background of stable or long-lived feebly interacting particl
 es. This applies\, once more\, to sterile neutrinos which can constitute c
 old non-thermal dark matter for a wide range of masses\, including the keV
  scale.\n\nBiography: Dr. Fotis Koutroulis is a postdoc at the Institute 
 of High Energy Physics\, CAS\, and an affiliated member of CCAST. He recei
 ved his PhD in Physics from the National Technical University of Athens in
  2021. After completing his doctorate\, he held a postdoctoral position at
  the Institute of Theoretical Physics\, University of Warsaw\, before join
 ing IHEP. His research interests lie at the interface of particle physics 
 and early universe cosmology\, with a focus on physics beyond the Standard
  Model\, dark matter\, and cosmological probes of new physics.\n\nhttps://
 indico.itp.ac.cn/event/403/
LOCATION:ITP South Building 6620
URL:https://indico.itp.ac.cn/event/403/
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