Homotopy classification of projections in the corona algebra of a non-simple $C\sp *$-algebra

Lawrence G. Brown, Hyun Ho Lee

We study projections in the corona algebra of $C(X)\otimes K$ where $X=[0,1],[0,\infty ),(-\infty ,\infty )$, and $[0,1]/\{0,1\}$. Using BDF's essential codimension, we determine con…