On Nov 11, 1:18 pm, Ray Vickson <RGVick...@shaw.ca> wrote: > On Sunday, November 11, 2012 7:38:09 AM UTC-8, kir wrote: > > What kind of work is being done in probability theory beyond the standard normally used? I know that negative probabilities have been discussed. Is there anything else? > > I'm not sure this is what you want, but there has been work in Probability theory using "non-standard analysis", so one can talk about actual infinitesimals, etc. Perhaps the most accessible introduction to this is the old but still good little book by Edward Nelson ("Radically Elementary Probability", Princeton U. Press). You can download a free pdf version from Edward Nelson's home page: just go to his publications list and click on the book title.