Possible Evidence of Time Variation of Weak Interaction Constant from   Double Beta Decay Experiments
  A comparison is made of the probability of the process of two neutrino double beta decay for $^{82}$Se in direct (counter) and geochemical experiments. It is shown that the probability is systematically lower in geochemical experiments, which characterize the probability of $\beta\beta(2\nu)$ decay a few billions years ago. The experimental data for $^{130}$Te are also analyzed. It is shown that geochemical measurements on young minerals give lower values of $T_{1/2}$ ($^{130}$Te) and $T_{1/2}$ ($^{82}$Se) as compared to measurements on old minerals. It is proposed that this could be due to a change in the weak interaction constant with time. Possibilities of new, precise measurements be performed with the aid of counters and geochemical experiments are discussed. 
A.S. Barabash