Zariski emigrated to the
United States in 1927 supported by
Solomon Lefschetz. He had a position at
Johns Hopkins University where he became professor in 1937. During this period, he wrote
Algebraic Surfaces as a summation of the work of the Italian school. The book was published in 1935 and reissued 36 years later, with detailed notes by Zariski's students that illustrated how the field of algebraic geometry had changed. It is still an important reference. It seems to have been this work that set the seal of Zariski's discontent with the approach of the Italians to
birational geometry. He addressed the question of rigour by recourse to
commutative algebra. The
Zariski topology, as it was later known, is adequate for
biregular geometry, where varieties are mapped by polynomial functions. That theory is too limited for algebraic surfaces, and even for curves with singular points. A rational map is to a regular map as a
rational function is to a polynomial: it may be indeterminate at some points. In geometric terms, one has to work with functions defined on some open,
dense set of a given variety. The description of the behaviour on the complement may require
infinitely near points to be introduced to account for limiting behaviour
along different directions. This introduces a need, in the surface case, to use also
valuation theory to describe the phenomena such as
blowing up (balloon-style, rather than explosively). ==Harvard University years==