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SUMMARY:Motivic Superstring Amplitudes - Stieberger\, S (Max-Planck-Instit
 ut fr Physik\, Mnchen)
DTSTART:20130411T100000Z
DTEND:20130411T110000Z
UID:TALK44464@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:We review the recent advances in open superstring N-point tree
 -level computations. One basic ingredient is a basis of (N-3)! generalized
  Gaussian hypergeometric functions (generalized Euler integrals) encoding 
 all string effects through their dependence on the string tension $lpha'$
 . The structure of the open superstring amplitudes is analyzed. We find a 
 striking and elegant form\, which allows to disentangle its $lpha'$ power
  series expansion into several contributions accounting for different clas
 ses of multiple zeta values. This form is bolstered by the decomposition o
 f motivic multiple zeta values\, i.e. the latter encapsulate the $lpha'$-
 expansion of the superstring amplitude. Moreover\, a morphism induced by t
 he coproduct maps the $lpha'$-expansion onto a non-commutative Hopf algeb
 ra. This map represents a generalization of the symbol of a transcendental
  function. In terms of elements of this Hopf algebra the alpha'-expansion 
 assumes a very simple and symmetric form\, which carries all the relevant 
 information.\n
LOCATION:Seminar Room 1\, Newton Institute
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