SUB-GIANT BRANCH EVOLUTION AND EFFICIENT CENTRAL ENERGY-TRANSPORT

We gather and present observational evidence of a problem with the con ventional understanding of the late main-sequence and sub-giant branch evolution of globular cluster stars. The difficulties with these supp osedly ''well-understood'' phases of stellar evolution manifest themse lves in both sub-giant and red-giant branch anomolies (relative to mai n-sequence normalization) in recent, accurate, CCD-derived luminosity functions. Attempts to reproduce these features using conventional the ory and fairly conventional modifications have failed. However, we sho w that the anomalies, now known to exist in four classical metal-weak clusters including the historical archetype M92 and the now even more thoroughly surveyed M30, are consistent with simple predicted conseque nces of highly efficient central energy transport inside such stars. I f these results and our interpretation survive, then globular clusters may be younger than usually thought by up to approximately 20%. Altho ugh any sufficiently effective energy transport mechanism would help e xplain the observations, one intriguing possibility is transport due t o WIMPs (weakly interacting massive particles). In this case, globular clusters may have acted as giant detectors for such particles. These potentially significant results require further investigation with mor e detailed and specific models and more observational data, which shou ld be relatively easy to obtain on 2 m class telescopes.