  We investigate contributions of spacetime wormholes, describing baby universe
emission and absorption, to calculations of entropies and correlation
functions, for example those based on the replica method. We find that the
rules of the "wormhole calculus," developed in the 1980s, together with
standard quantum mechanical prescriptions for computing entropies and
correlators, imply definite rules for $\textit{limited}$ patterns of connection
between replica factors in simple calculations. These results stand in contrast
with assumptions that all topologies connecting replicas should be summed over,
and call into question the explanation for the latter. In a "free"
approximation baby universes introduce probability distributions for coupling
constants, and we review and extend arguments that successive experiments in a
"parent" universe increasingly precisely fix such couplings, resulting in
ultimately pure evolution. Once this has happened, the nontrivial question
remains of how topology-changing effects can modify the standard description of
black hole information loss.
