  The question whether the center vortex picture of the strongly interacting
vacuum can encompass the infrared dynamics of both SU(2) as well as Sp(2)
Yang-Mills theory is addressed. These two theories contain the same center
vortex degrees of freedom, and yet exhibit deconfinement phase transitions of
different order. This is argued to be caused by the effective action governing
the vortices being different in the two cases. To buttress this argument, a
random vortex world-surface model is constructed which reproduces available
lattice data characterizing Sp(2) Yang-Mills confinement properties. A new
effective action term which can be interpreted in terms of a vortex stickiness
serves to realize a first-order deconfinement phase transition, as found in
Sp(2) Yang-Mills theory. Predictions are given for the behavior of the spatial
string tension at finite temperatures.
