Non-Vanishing Cosmological Constant $\Lambda$, Phase Transitions, And $\Lambda$-Dependence Of High Energy Processes

It is pointed out that a collider experiment involves a local contribution to the energy-momentum tensor, a circumstance which not a common feature of the current state of the Universe at large characterized by the cosmological constant $\Lambda_0$. This contribution may be viewed as a change in the structure of space-time from its large scale form governed by $\Lambda_0$ to one governed by a $\Lambda$ peculiar to the scale of the experiment. Possible consequences of this effect are explored by exploiting the asymptotic symmetry of space-time for non-vanishing $\Lambda$ and its relation to vacuum energy.