BEGIN:VCALENDAR
PRODID://WordPress//Event-Post-V5.9.2//EN
VERSION:2.0
BEGIN:VTIMEZONE
TZID:Europe/Madrid
BEGIN:DAYLIGHT
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
DTSTART:19700329T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:19701025T030000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
SUMMARY:Ilya L. Shapiro, "Local and nonlocal models of quantum gravity"
UID:https://capa.unizar.es/?p=533
LOCATION:
DTSTAMP:20200205T121000
DTSTART;TZID=Europe/Madrid:20200205T121000
DTEND;TZID=Europe/Madrid:20200205T131000
DESCRIPTION:The main difficulty of perturbative quantum gravity (QG) in D=4 dimensions
is the conflict between renormalizability and unitarity of the theory. The
simplest version of QG is based on General Relativity and turns out to be
nonrenormalizable. One can construct renormalizable and even
superrenormalizable versions of QG by introducing higher derivatives. In
the local versions of higher derivative models of QG there are always
unphysical higherderivative massive unphysical ghosts. One can construct
non-polynomial in derivatives (or, equivalently, nonlocal) models of QG,
which have no ghosts at the tree level. However, taking loop corrections
into account one meets infinite amount of ghost-like complex states. The
theories of both local and nonlocal types attracted a lot of attention in
the last years and our purpose it to present a brief review of the problems
and perspectives of these models, according to the present-day
understanding.
END:VEVENT
END:VCALENDAR