Abstract: In nature one finds superconductors of varying critical temperatures and energy gaps. For weak superconductors, where the critical temperature is small, a universal phenomenon occurs: The ratio of the energy gap and critical temperature is a universal value, independent of the specific superconductor. I will present recent work on such universal phenomena in the BCS theory of superconductivity.
Based on joint works with A. B. Lauritsen, E. Langmann, and B. Roos.