A projective representation is a representation up to a phase. Sternberg proved that projective representations of a group ( G ) are equivalent to linear representations of its central extension ( \tildeG ).
This is the heart of the text. Sternberg excels at explaining the continuous symmetries that define fundamental physics. sternberg group theory and physics new
The latter half of the book applies the mathematical machinery to the Standard Model of particle physics. A projective representation is a representation up to