  A random vortex world-surface model for the infrared sector of Sp(2)
Yang-Mills theory is constructed. The Sp(2) gauge group, while allowing for the
same set of center vortex fluxes as the SU(2) gauge group, induces a
significantly different dynamics on those vortex fluxes, which manifests itself
in a first-order deconfinement phase transition. As shown by the construction
presented here, a new vortex effective action term which can be interpreted in
terms of a vortex stickiness can be used to drive the deconfinement transition
towards first-order behavior. The available data from lattice Sp(2) Yang-Mills
theory are reproduced quantitatively and, in addition, predictions for the
behavior of the spatial string tension at high temperatures are presented.
