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Bounds on characteristic numbers by curvature and radius. (English) Zbl 1175.53047

Let \(M_{2n}\) and \(N_{4n}\) be closed and orientable Riemanian manifolds of dimension \(2n\) and \(4n\), respectively. Numerical bounds on the Euler-Poincaré characteristic \(\chi(M_{2n})\) and the Pontryagin numbers \(P_I(N_{4n})\) are presented in terms of the sectional curvature \(k\leq\text{sec}\leq K\) and radius \(r\). Here the letter \(I\) appearing in \(P_I(N_{4n})\) indicates a partition \(I= k_1,\dots,k_s\) of unity. They are summarized as follows: \(|\chi (M_{2n})|\) is bounded by \(\frac{(2n)!^2}{n!^2}\frac{(Kr^2)^n}{2^{3n}}\) if \(k=0\), and if \(k<0\) by
\[ \frac{(2n)!^2C^n(-1)^{n-1}}{2^{3n-1}n!(n-1)!(-k)^n}\sum^{n-1}_{m=0}(-1)^m{n-1\choose m}\left(\frac {\cosh^{2m +1}(r\sqrt{-k})-1}{2m+1} \right) \] where \(C\) is given by \[ |R_{ij1m}|<C=\max(-k,K,\tfrac 23(K-K)). \] Next, \(|P_I(N_{4n})|\) is bounded by
\[ \frac{(4n)!^{s+1}}{(2n)!\prod^s_{i=1}(4n-2k_i)!} \frac{(Kr^2)^{2n}}{2^{4n}} \]
if \(k=0\), and by
\[ A(n)\frac{C^{2n}} {(-k)^{2n}} \sum^{2n-1}_{m=0}(-1)^m{2n-1\choose m}\left(\frac{\cosh^{2m+1}(r\sqrt{-k})-1}{2m+2} \right) \]
where
\[ A(n)=\frac {(4n)!^{s+1}(-1)^{2n-1}}{(2n-1)!2^{4m-1}\prod^s_{i=1} (4n-2K_i)!} \]
if \(k<0\).

MSC:

53C20 Global Riemannian geometry, including pinching
57R20 Characteristic classes and numbers in differential topology
Full Text: DOI

References:

[1] M. Berger, On the characteristic of positively-pinched Riemannian manifolds , Proc. National Acad. Sci. 48 (1962), 1915-1917. · Zbl 0116.38702 · doi:10.1073/pnas.48.11.1915
[2] R.L. Bishop and S.I. Goldberg, On curvature and Euler-Poincaré characteristic , Proc. National Acad. Sci. 49 (1963), 814-817. · Zbl 0173.49805 · doi:10.1073/pnas.49.6.814
[3] ——–, Some implications of the generalized Gauss-Bonnet theorem , Trans. Amer. Math. Soc. 112 (1964), 508-535. JSTOR: · Zbl 0133.15101 · doi:10.2307/1994158
[4] J.P. Bourguignon and H. Karcher, Curvature operators: Pinching estimates and geometric examples , Ann. Sci. École Norm. 11 (1978), 71-92. · Zbl 0386.53031
[5] A. Dessai and W. Tuschmann, Nonnegative curvature and cobordism type , Math. Z. 257 (2007), 7-12. · Zbl 1127.53031 · doi:10.1007/s00209-006-0092-1
[6] I.S. Gradshteyn and I.M. Ryshik, Tables of integrals, series, and products , 6th ed., Academic Press, San Diego, 2000
[7] W. Gröbner and N. Hofreiter, Integraltafel. Erster Teil. Unbestimmte Integrale. , Springer-Verlag, Vienna, 1949. · Zbl 0039.12903
[8] M. Gromov, Curvature, diameter and Betti numbers , Comment. Math. Helv. 56 (1981), 179-195. · Zbl 0467.53021 · doi:10.1007/BF02566208
[9] S. Kobayashi and K. Nomizu, Foundations of differential geometry , vol. II, Interscience Tracts Pure Appl. Math. 15 , Interscience Publishers, John Wiley & Sons, Inc., 1969. · Zbl 0175.48504
[10] J. Milnor and J. Stasheff, Characteristic classes , Princeton University Press and University of Tokyo Press, 1974. · Zbl 0298.57008
[11] M. Spivak, A comprehensive introduction to differential geometry , second ed., vol. V, Publish or Perish, Wilmington, Delaware, 1979. · Zbl 0439.53001
[12] G. Tsagas, On the Pontrjagin numbers of positively-pinched Riemannian manifolds , Tensor (N.S.) 21 (1970), 377-379. · Zbl 0195.23502
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