×

\(S^{1}\)-actions on highly connected manifolds. (English) Zbl 1100.19003

A celebrated theorem of M. F. Atiyah and F. Hirzebruch [“Spin-manifolds and group actions”, Essays Topol. Relat. Top., Mem. dédiés a Georges de Rham, 18–28 (1970; Zbl 0193.52401)] states that \(\widehat{A}(M) = 0\) if \(M\) admits a smooth non-trivial \(S^1\)-action, where \(M\) denotes a smooth closed connected spin-manifold. In this paper the author considers the case where \(M\) is highly connected. Using the theory of elliptic genera, the author in fact shows that, in addition to the above one, there exist further obstructions according to the degree of connectivity of \(M\). Let \(\Phi(M)\) be a modular function of weight 0 with \(\mathbb Z_2\)-character for a subgroup \(\Gamma_0(2)\) of \(SL_2(\mathbb Z)\) consisting of all matrices whose \((2, 1)\)-components are even. Letting \(\Phi_0(M)\) denote its \(q\)-expansion \[ \Phi_0(M)=q^{-\dim M/8}\cdot (\widehat{A}(M)-\widehat{A}(M, TM)\cdot q +\widehat{A}(M, \Lambda^2TM+TM)\cdot q^2 + \cdots ) \] in the \(\widehat{A}\)-cusp, where \(\widehat{A}(M, E)\) denotes the index of the Dirac operator twisted with \(E\otimes \mathbb C\), the author proves the following theorem: Let \(M\) be be a \(k\)-connected manifold for \(k \geq 4r > 0\). If \(M\) admits a smooth non-trivial \(S^1\)-action, then the first \((r+1)\) coefficients of \(\Phi_0(M)\) vanish. This is established by considering the \(q\)-expansion \(\text{sign}_{S^1}(q, \mathcal{L}M)\) of the \(S^1\)-equivariant elliptic genus in the signature cusp, where \(\mathcal{L}M\) denotes the free loop space of \(M\). Briefly sketching, it can be stated as follows. Using the Lefschetz fixed point formula it follows from the assumption of the theorem that the first \((r+1)\) coefficients of \(\text{sign}_{S^1}(q, \mathcal{L}M)\) vanish at the involusion \(\sigma\in S^1\) as characters of \(S^1\). In addition, via the rigidity theorem one knows that \(\text{sign}_{S^1}(q, \mathcal{L}M)(\sigma)\) is equal to the \(q\)-expansion of \(\Phi(M)\) in the singular cusp, so that changing cusps one obtains the theorem. Finally the author provides an example of an 8-connected manifold with vanishing Witten genus but \(\widehat{A}(M, \Lambda^2TM+TM)\neq 0\). This example shows that the author’s theorem is independent of the vanishing theorem for the Witten genus [see the author, “\(\text{Spin}^c\)-manifolds with Pin(2)-action”, Math. Ann. 315, 511–528 (1999; Zbl 0963.19002) and K. Liu, “On modular invariance and rigidity theorems”, J. Differ. Geom. 41, 343–396 (1995; Zbl 0836.57024)].

MSC:

19J35 Obstructions to group actions (\(K\)-theoretic aspects)
19L47 Equivariant \(K\)-theory
57R20 Characteristic classes and numbers in differential topology
58J20 Index theory and related fixed-point theorems on manifolds
58J26 Elliptic genera
Full Text: DOI

References:

[1] Atiyah, M. F.; Hirzebruch, F., Spin-manifolds and group actions, (Essays on Topology and Related Topics. Essays on Topology and Related Topics, Memoires dédiés à Georges de Rham (1970), Springer), 18-28 · Zbl 0193.52401
[2] Atiyah, M. F.; Singer, I. M., The index of elliptic operators: III, Ann. of Math., 87, 546-604 (1968) · Zbl 0164.24301
[3] Bott, R.; Taubes, C. H., On the rigidity theorems of Witten, J. Amer. Math. Soc., 2, 137-186 (1989) · Zbl 0667.57009
[4] Bredon, G. E., (Introduction to Compact Transformation Groups. Introduction to Compact Transformation Groups, Pure and Applied Mathematics, vol. 46 (1972), Academic Press) · Zbl 0246.57017
[5] Burghelea, D., Free differentiable \(S^1\) and \(S^3\) actions on homotopy spheres, Ann. Sci. École Norm. Sup. (4), 5, 183-215 (1972) · Zbl 0247.57009
[6] Dessai, A., \(Spin^c\)-manifolds with Pin(2)-action, Math. Ann., 315, 511-528 (1999) · Zbl 0963.19002
[7] Herrera, H.; Herrera, R., \( \hat{A}\) genus on non-spin manifolds with \(S^1\) action and the classification of positive quaternion-Kähler 12-manifolds, J. Differential Geom., 61, 341-364 (2002) · Zbl 1071.53027
[8] Hirzebruch, F.; Berger, Th.; Jung, R., (Manifolds and Modular Forms. Manifolds and Modular Forms, Aspects of Mathematics, vol. E20 (1992), Vieweg) · Zbl 0767.57014
[9] Hirzebruch, F.; Slodowy, P., Elliptic genera, involutions and homogeneous spin manifolds, Geom. Dedicata, 35, 309-343 (1990) · Zbl 0712.57010
[10] Kervaire, M. A.; Milnor, J. W., Bernoulli numbers, homotopy groups, and a theorem of Rohlin, (Proc. Intern. Congress of Math. 1958 (1960), Cambridge Univ. Press), 454-458 · Zbl 0119.38503
[11] (Landweber, P. S., Elliptic Curves and Modular Forms in Algebraic Topology (Proceedings Princeton 1986). Elliptic Curves and Modular Forms in Algebraic Topology (Proceedings Princeton 1986), Lecture Notes in Mathematics, vol. 1326 (1988), Springer) · Zbl 0649.57022
[12] Liu, K., On modular invariance and rigidity theorems, J. Differential Geom., 41, 343-396 (1995) · Zbl 0836.57024
[13] E. Witten, The index of the Dirac operator in loop space, in: [11]; E. Witten, The index of the Dirac operator in loop space, in: [11]
This reference list is based on information provided by the publisher or from digital mathematics libraries. Its items are heuristically matched to zbMATH identifiers and may contain data conversion errors. In some cases that data have been complemented/enhanced by data from zbMATH Open. This attempts to reflect the references listed in the original paper as accurately as possible without claiming completeness or a perfect matching.