Sharp boundaries for the swampland

We reconsider the problem of bounding higher derivative couplings in consistent weakly coupled gravitational theories, starting from general assumptions about analyticity and Regge growth of the S-matrix. Higher derivative couplings are expected to be of order one in the units of the UV cutoff. Our approach justifies this expectation and allows to prove precise bounds on the order one coefficients. Our main tool are dispersive sum rules for the S-matrix. We overcome the difficulties presented by the graviton pole by measuring couplings at small impact parameter, rather than in the forward limit. We illustrate the method in theories containing a massless scalar coupled to gravity, and in theories with maximal supersymmetry.

Upsilon Transverse Momentum at Hadron Colliders

We predict the shape of the transverse momentum pT spectrum of ϒ production. The distribution at low pT is dominated by the region of small impact parameter b and may be computed reliably in perturbation theory. We resum to all orders in the strong coupling αs the process-independent large logarithmic contributions that arise from initial-state gluon showers in the small pT(≤ Mϒ) region. The cross section at large pT is represented by the [Formula: see text] lowest-order non-vanishing perturbative contribution.

DECOHERENT SCATTERING OF LIGHT PARTICLES IN A D-BRANE BACKGROUND

We discuss the scattering of two light particles in a D-brane background. It is known that, if one light particle strikes the D-brane at small impact parameter, quantum recoil effects induce entanglement entropy in both the excited D-brane and the scattered particle. In this letter we compute the asymptotic "out" state of a second light particle scattering off the D-brane at large impact parameter, showing that it also becomes mixed as a consequence of quantum D-brane recoil effects. We interpret this as a non-factorizing contribution to the superscattering operator $ for the two light particles in a Liouville D-brane background, that appears when quantum D-brane excitations are taken into account.