Rapidity gap physics at contemporary colliders

This thesis is concerned with the theory and the phenomenology of rapidity gap processes. We perform perturbative calculations of energy flow observables in jet-gap-jet processes, which consist of resummed primary emission calculations specific to the soft gluon geometry at HERA and an estimate of non-global (secondary emission) effects in clustered energy flow observables. The resulting predictions agree well with H1 data. We also study hard diffraction and use a factorised model, with a Monte Carlo event generator, to make detailed predictions for gap-jet-gap events at the Tevatron. We find that we can describe the data in a natural way by using HERA parton densities and a gap surivial factor consistent with theoretical estimates.