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SUMMARY:Tracing out massive fields in cosmology
DTSTART;VALUE=DATE-TIME:20261108T083000Z
DTEND;VALUE=DATE-TIME:20261108T090000Z
DTSTAMP;VALUE=DATE-TIME:20261023T150407Z
UID:indico-contribution-2941@indico.itp.ac.cn
DESCRIPTION:Speakers: Guanhao Sun (Chongqing University)\nCosmological cor
 relators are calculated through the in-in formalism in (quasi-)de Sitter b
 ackground. Their effective description is best represented by a reduced de
 nsity matrix. In this talk\, I will first review the differences between t
 he usual EFT used in scattering amplitude calculations and the Schwinger-K
 eldysh EFT for correlators. I will then discuss the reduced density matrix
  for a light field at finite time\, obtained by tracing out a massive fiel
 d in a quasi-single-field model with non-linear couplings. The trace gener
 ates branch-mixing terms which are generally present in the Schwinger-Keld
 ysh formalism. Explicit calculations of the effective description and the 
 bispectrum will be shown for a conformally coupled massive field. I will t
 hen discuss how a local effective field theory is obtained through a large
  mass expansion of the exact non-local effective description. Finally\, I 
 will study the symmetry and Schwinger-Keldysh constraints on the reduced d
 ensity matrix.\n\nhttps://indico.itp.ac.cn/event/417/contributions/2941/
LOCATION:
URL:https://indico.itp.ac.cn/event/417/contributions/2941/
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