Oak Ridge National Laboratory

Physics Division

Physics Division Seminars

Physics Division Seminars bring us speakers on a variety of physics related subjects. Usually these are held in the Building 6008 large Conference Room, at 3:00 pm on the chosen day, but times and locations may vary. For more information, contact our seminar chairman,

Alfredo Galindo-Uribarri
Tel (Office): (865) 574-6124  (FAX): (865) 574-1268


Thu., August 19, 2010, at 3:00 p.m. (refreshments at 2:40 p.m.)

Are fundamental constants actually constant? Latest results from Oklo

Chris Gould, North Carolina State University and Triangle Universities Nuclear Laboratory
Building 6008 Conference Room

Time variation of dimensionless fundamental constants arises naturally in extra-dimensional theories. Searches for evidence of changes in alpha, the electromagnetic fine structure constant, have been particularly active over the last few decades. The Oklo natural nuclear reactors emerged early on as a testing ground, based on possible shifts in the energy of the 97.3-meV resonance in Sm-149. We recently showed that disagreements among Oklo determinations of the time evolution of alpha were due to different reactor models, which led to different neutron spectra used in the calculations. Our suggested two sigma bound on a possible fractional change in alpha over two billion years is of order a few parts in 108. I review our analysis, and discuss some remaining issues: What was the temperature while the reactor was operating? and Does the shift in energy of the Sm-149 resonance in fact bound alpha at all?