R
ijkl;m
þ R
ijlm;k
þ R
ijmk;l
¼ 0; (Bianchi identities).
Sectional curvature: Gaussian curvature of EM formed by geodesics
through x and tangent to E,
Kðx; EÞ¼
RðX; Y; X; YÞ
jXj
2
jYj
2
ðXj YÞ
2
; E ¼ spanfX; Yg:
Ricci tensor: The only non-zero contraction of the Riemann curvature tensor,
R
lm
¼ g
jk
R
jlkm
; R
lm
¼ R
ml
:
Curvature scalar: R = g
lm
R
lm
.
References
1. Lang, S.: Algebra. Addison-Wesley, Reading (1965)
2. Reed, M., Simon, B.: Methods of Modern Mathematical Physics. Vol. I: Functional Analysis.
Academic Press, New York (1973)
3. Steenrod, N.E.: The Topology of Fiber Bundles, 6th ed. Princeton University Press, Princeton
(1967)
4. Warner, F.W.: Foundations of Differentiable Manifolds and Lie Groups. Springer, New York
(1983)
5. Pontrjagin, L.S.: Topological Groups, 2nd ed. Gordon and Breach, New York (1966)
6. Fuchs, J.: Affine Lie Algebras and Quantum Groups. Cambridge University Press, Cambridge
(1992)
7. Kobayashi, S., Nomizu, K.: Foundations of Differential Geometry (Interscience, New York,
1963 and 1969), Vol. I and II.
8. Chern, S.S., Chen, W.H., Lam, K.S.: Lectures on Differential Geometry. World Scientific,
Singapore (2000)
378 Compendium