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SUMMARY:Wiener-Hopf factorisation\, Toeplitz operators and the ergosphere 
 of a rotating black hole - M. Cristina Câmara (University of Lisbon)
DTSTART:20231109T113000Z
DTEND:20231109T123000Z
UID:TALK201847@talks.cam.ac.uk
DESCRIPTION:Using a Riemann-Hilbert approach and the canonical Wiener-Hopf
  factorisation of certain matrix functions called monodromy matrices\, one
  can obtain explicit solutions to the non-linear field equations of some g
 ravitational theories.\nWe address here\, for the first time\, the underly
 ing question of what happens when a canonical factorisation does not exist
  and we use the close connection of Wiener-Hopf factorisation with Toeplit
 z operators to study this question.\nFor the case of rational monodromy ma
 trices\, we prove that the non-existence of a canonical factorisation dete
 rmines a curve in the Weyl coordinates plane where some elements of the me
 tric tend to zero.&nbsp\; In the case of the Kerr black hole\, it coincide
 s with the ergosurface.\n&nbsp\;
LOCATION:External
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