Theoretical High Energy Seminar – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > 2012 > Theoretical High Energ...

Theoretical High Energy Seminar

Speaker: Paolo Di Vecchia (NBI, NORDITA)

Title: Scattering of closed strings on a stack of N Dp branes at high energy

Abstract: An important difference between field and string theory is that, while in field theory the curved space properties are put by hand in the action, in string theory the scattering amplitudes are computed in flat Minkowski space-time and the curved space-time structure emerge from them. As an example of this, I will consider the elastic scattering of a massless closed string on a stack of N Dp branes as a function of the energy E of the incoming string and of the transfer momentum. It turns out that the tree diagrams are divergent at high energy violating unitarity. Unitarity is recovered by summing over loop corrections obtaining the so-called eikonal operator. This operator is then used for computing the deflection angle in the metric of the stack of N Dp branes as a function of the impact parameter b and the tidal forces acting on the string at any order in \alpha'/b^2. We show that string theory reproduces field theory results in the limit of infinite string tension. Then, we consider the motion of the string in the metric of a stack of N Dp branes at high energy and we show that the leading term for large impact parameter agrees with the one obtained from the eikonal operator at any order in \alpha'/b^2.