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SUMMARY:Virtual Seminar - "Classifying\, Counting and Constraining Gravita
tional S matrices"
DTSTART;VALUE=DATE-TIME:20191121T103000Z
DTEND;VALUE=DATE-TIME:20191121T123000Z
DTSTAMP;VALUE=DATE-TIME:20200712T132949Z
UID:indico-event-863171@indico.cern.ch
DESCRIPTION:Abstract: We study the space of all kinematically allowed fou
r photon and four graviton S-matrices\, polynomial in scattering momenta.
We demonstrate that this space is the permutation invariant sector of a mo
dule over the ring of polynomials of the Mandelstam invariants s\, t and u
. We construct these modules for every value of the spacetime dimension D\
, and so explicitly count and parameterize the most general four photon an
d four graviton S-matrix at any given derivative order. We also explicitly
list the local Lagrangians that give rise to these S-matrices. We then co
njecture that the Regge growth of S-matrices in all physically acceptable
classical theories is bounded by s 2 at fixed t. A four parameter subset o
f the polynomial photon S-matrices constructed above satisfies this Regge
criterion. For gravitons\, on the other hand\, no polynomial addition to t
he Einstein S-matrix obeys this bound for D ≤ 6. For D ≥ 7 there is a
single six derivative polynomial Lagrangian consistent with our conjecture
d Regge growth bound. Our conjecture thus implies that the Einstein four g
raviton S-matrix does not admit any physically acceptable polynomial modif
ications for D ≤ 6. We also argue that every finite sum of pole exchan
ge contributions to four graviton scattering also such violates our conjec
tured Regge growth bound\, at least when D ≤ 6\, even when the exchanged
particles have low spin\n\nhttps://indico.cern.ch/event/863171/
LOCATION:CERN 4/3-006 - TH Conference Room
URL:https://indico.cern.ch/event/863171/
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