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SUMMARY:Extensions of scalar-tensor theory: Parity violation and multiple 
 fields
DTSTART;VALUE=DATE-TIME:20260521T053000Z
DTEND;VALUE=DATE-TIME:20260521T061000Z
DTSTAMP;VALUE=DATE-TIME:20260530T170815Z
UID:indico-contribution-2474@indico.itp.ac.cn
DESCRIPTION:Speakers: Xian Gao (Sun Yat-sen University)\nThis talk present
 s recent progress in the construction of scalar-tensor theories\, with a f
 ocus on parity violation and multiple scalar fields. I will first review t
 he relation between generally covariant scalar-tensor theories and spatial
 ly covariant gravity in the unitary gauge\, emphasizing how this correspon
 dence provides an efficient way to control higher-order time derivatives a
 nd avoid Ostrogradsky ghost degrees of freedom. Using this framework\, I w
 ill discuss the systematic construction of the most general parity-violati
 ng scalar-tensor theory up to d=4 that is ghost-free in the unitary gauge\
 , including the resulting "Qi-Xiu" Lagrangians and their relation to known
  examples such as Chern-Simons and chiral scalar-tensor theories. I will t
 hen describe a new geometric approach to multiple scalar-tensor theories\,
  in which each scalar field defines a foliation of spacelike hypersurfaces
  and the theory is built from the corresponding hypersurface geometric qua
 ntities. This multiple-foliation construction provides a systematic route 
 toward ghost-free multi-field scalar-tensor theories beyond the traditiona
 l Horndeski/DHOST framework.\n\nhttps://indico.itp.ac.cn/event/419/contrib
 utions/2474/
LOCATION:Small Lecture Hall\, Chongqing University Library (图书馆小
 报告厅) 1F-9
URL:https://indico.itp.ac.cn/event/419/contributions/2474/
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