The only Wiedersehen surfaces are the standard round spheres. The conjecture was proven by combining the Berger-Kazdan comparison theorem with A. Weinstein's results for even and C. T. Yang's for odd. Green (1963) obtained the first proof of the Blaschke's conjecture in the two-dimensional case.

# Blaschke Conjecture

## See also

Wiedersehen Surface## Explore with Wolfram|Alpha

## References

Chavel, I.*Riemannian Geometry: A Modern Introduction.*New York: Cambridge University Press, 1994.Green, L. W., "Auf Wiedersehensflächen."

*Ann. Math.*

**78**, 289-299, 1963.

## Referenced on Wolfram|Alpha

Blaschke Conjecture## Cite this as:

Weisstein, Eric W. "Blaschke Conjecture."
From *MathWorld*--A Wolfram Web Resource. https://mathworld.wolfram.com/BlaschkeConjecture.html