If I call mathptmx, the following are carried out:
\def\rmdefault{ptm}
\DeclareSymbolFont{operators} {OT1}{ztmcm}{m}{n}
\DeclareSymbolFont{letters} {OML}{ztmcm}{m}{it}
\DeclareSymbolFont{symbols} {OMS}{ztmcm}{m}{n}
\DeclareSymbolFont{largesymbols}{OMX}{ztmcm}{m}{n}
\DeclareSymbolFont{bold} {OT1}{ptm}{bx}{n}
\DeclareSymbolFont{italic} {OT1}{ptm}{m}{it}
\@ifundefined{mathbf}{}{\DeclareMathAlphabet{\mathbf}{OT1}{ptm}{bx}{n}}
\@ifundefined{mathit}{}{\DeclareMathAlphabet{\mathit}{OT1}{ptm}{m}{it}}
My question is: what are the defaults, i.e. what would these fonts be if I didn't call mathptmx? I guess \rmdefault would be cmr for Computer Modern, but the others? Also, I know \mathcal is redefined in mathptmx, since the font changes, but I cannot find the code redefining it. Which is that code? And again, what is the default? And what about \mathfrak? Does it get changed too?
\mathfrakisamsfontswith its\DeclareMathAlphabet{\mathfrak}{U}{euf}{m}{n} \SetMathAlphabet{\mathfrak}{bold}{U}{euf}{b}{n}. Which meansmathptmxis unlikely to affect it. – MickG Apr 05 '15 at 17:50