Spectrum of C_heart where
                 1 + z + 2\sqrt{1 - z^2}
    heart(z)=   -------------------------
                 3 - z + 2\sqrt{1 - z^2}

Figure 7.1, page 303, of "Composition Operators on Spaces of Analytic Functions" [spectrum of C_heart]

Reprinted with permission from
"Composition Operators on Spaces of Analytic Functions"
by Carl C. Cowen and Barbara D. MacCluer.
Copyright CRC Press, Boca Raton, Florida.