added a sentence about conditions of existence of path integrals (at PT's request); other minor stuff
\input{\pathtotrunk preamble.tex}
\input{\pathtotrunk text/kw_macros}
\input{\pathtotrunk talks/beamer_preamble.tex}
% This switches fonts to the Palatino family.
% \renewcommand{\familydefault}{ppl}
\usepackage{array}