Kolloquien SS 2025

Montag, 30.06.2025: Inhomogeneous Laplace equation on modular surface

Ksenia Fedosova

Low-energy expansion of scattering amplitudes of elementary particles arising in string theory are often linked to an inhomogeneous Laplace equation. For example, for the IIB string theory in 10+1 dimensions and scattering of 4-gravitons, the equation is the inhomogeneous Laplace equation on the modular surface, where the inhomogeneous part contains products of Eisenstein series. In this talk, we discuss how to solve this partial differential equation. Additionally, from asymptotic behavior of its solutions we obtain exact identities for infinite convolution sums of even divisor functions weighted by Laurent polynomials with logarithms.