\mathcal is what you want:
I am reading Dummit and Foote on affine algebraic sets and wish to create posts refering to such objects.
The notation for a subset Z(S) of affine space is a "curly" Z - see attachment - bottom of page 658.
Also the notion for the unique largest ideal whose locus determines a particular algebraic set V is a 'curly' I - see attachment, third paragraph on page 660.
Can someone please help me to use Latex to produce these symbols.