Experimental measurements in terrestrial laboratory , space and astrophysical observations of variation and fluctuation of nuclear decay constants , measurements of large enhancements in fusion reaction rate of deuterons implanted in metals and electron capture by nuclei in solar core indicate that these processes depend on the environment where take place and possibly also on the fluctuation of some extensive parameters and eventually on stellar energy production .
Electron screening is the first important environment effect .
We need to develop a treatment beyond the Debye-Hückel screening approach , commonly adopted within global thermodynamic equilibrium .
Advances in the description of these processes can be obtained by means of q -thermostatistics and/or superstatistics for metastable states .
This implies to handle without ambiguities the case q < 1 .