Jim Rantschler and Randy Morrison discuss physics from elementary particles to cosmological effects at the limits of our theoretical knowledge or have recently emerged.
https://www.podomatic.com/podcasts/physicsfrontiers-rantschler
f(R) Theories of Gravity
Jim and Randy discuss gravitational theories that modify general relativity by changing the action using a polynomial dependence on the Ricci scalar. Although not physically motivated, some of these theories produce effects similar to those of dark matter, dark energy, and cosmological constants.
Show notes: http://frontiers.physicsfm.com/9