  Certain AdS black holes in the STU model can be conformally scaled to
wormhole and black hole solutions of an f(R) type theory which have two
asymptotically AdS regions and are completely free of curvature singularities.
While there is a delta-function source for the dilaton, classical string probes
are not sensitive to this singularity. If the AdS/CFT correspondence can be
applied in this context, then the wormhole background describes a phase in
which two copies of a conformal field theory interact with each other, whereas
the nonsingular black hole describes entangled states. By studying the behavior
of open strings on these backgrounds, we extract a number of features of the
quarks and anti-quarks that live in the field theories. In the interacting
phase, we find that there is a maximum speed with which the quarks can move
without losing energy, beyond which energy is transferred from a quark in one
field theory to a quark in the other. We also compute the rate at which moving
quarks within entangled states lose energy to the two surrounding plasmas.
While a quark-antiquark pair within a single field theory exhibits Coulomb
interaction for small separation, a quark in one field theory exhibits
spring-like confinement with an anti-quark in the other field theory. For the
entangled states, we study how the quark-antiquark screening length depends on
temperature and chemical potential. In the interacting phase of the two field
theories, a quadruplet made up of one quark-antiquark pair in each field theory
can undergo transitions involving how the quarks and antiquarks are paired in
terms of the screening.
