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CATEGORIES;LANGUAGE=en-US:Neve Shalom
CONTACT:
DESCRIPTION:Title: Landau diagrams in AdS and S-matrices from conformal cor
relators\nAbstract: Quantum field theories in AdS generate conformalcorrel
ation functions on the boundary\, and in the limit where AdS is nearly fla
t one should be able to extract an S-matrix from such correlators. We disc
uss a particularly simple position-space procedure to do so. It features a
direct map from boundary positionsto (on-shell) momenta and thereby relat
es cross ratios to Mandelstam invariants. This recipe succeeds in several
examples\, includes the momentum-conserving delta functions\, and can be s
hown to imply the two proposals based on Mellin space and on the OPE data.
Interestingly the procedure does not always work: the Landau singularities
of a Feynman diagram are shown to be part of larger regions\, to be calle
d `bad regionsâ€™\, where the flat-space limit of the Witten diagram diverge
s. To capture these divergences we introducethe notion of Landau diagrams
in AdS. As in flat space\, these describe on-shell particles propagating o
ver large distances in a complexified space\, with a form of momentum cons
ervation holding at each bulk vertex. As an application we recover the ano
malousthreshold of the four-point triangle diagram at the boundary of a ba
d region.
DTSTART;TZID=Asia/Jerusalem:20201006T160000
DTEND;TZID=Asia/Jerusalem:20201006T170000
SEQUENCE:0
SUMMARY:Shota komatsu
URL:https://phsites.technion.ac.il/strings/event/shota-komatsu/
X-ALT-DESC;FMTTYPE=text/html:\\n\\n\\n\\n\\nTitle: Landau
diagrams in AdS and S-matrices from conformal correlators

\nAbstrac
t: Quantum field theories in AdS generate conformalcorrelation functions o
n the boundary\, and in the limit where AdS is nearly flat one should be a
ble to extract an S-matrix from such correlators. We discuss a particularl
y simple position-space procedure to do so. It features a direct map from
boundary positionsto (on-shell) momenta and thereby relates cross ratios t
o Mandelstam invariants. This recipe succeeds in several examples\, includ
es the momentum-conserving delta functions\, and can be shown to imply the
two proposals based on Mellin space and on the OPE data.Interestingly the
procedure does not always work: the Landau singularities of a Feynman dia
gram are shown to be part of larger regions\, to be called `bad regionsâ€™\,
where the flat-space limit of the Witten diagram diverges. To capture the
se divergences we introducethe notion of Landau diagrams in AdS. As in fla
t space\, these describe on-shell particles propagating over large distanc
es in a complexified space\, with a form of momentum conservation holding
at each bulk vertex. As an application we recover the anomalousthreshold o
f the four-point triangle diagram at the boundary of a bad region.

\n
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