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Toric extremal Kähler-Ricci solitons are Kähler-Einstein. (English) Zbl 1381.53076

The authors prove that Calabi extremal Kähler-Ricci solitons on compact toric Kähler manifolds are Kähler-Einstein, see Theorem 2.
Extremal Kähler metrics are critical points of the Calabi functional, that is, the \(L^2\)-norm of the scalar curvature. Kähler-Ricci solitons are Kähler metrics \(\omega\) satisfying \(\rho+c\omega=\mathcal{L}_X\omega\), where \(\rho\) is the Ricci form, \(c\) is a real constant, and \(X\) is a holomorphic vector field. Toric manifolds are compact Kähler \(2n\)-dimensional manifolds admitting an effective Hamiltonian action of an \(n\)-dimensional torus by Kähler automorphisms.
In [Proc. Am. Math. Soc. 144, No. 2, 813–821 (2016; Zbl 1337.53053)], the authors proved that compact extremal Kähler-Ricci solitons with positive holomorphic sectional curvature are Kähler-Einstein. Note that toric Kähler manifolds can have holomorphic sectional curvature of any sign. More in general, the authors ask whether it is true that every extremal Kähler-Ricci solitons are Einstein, see Problem 2.

MSC:

53C25 Special Riemannian manifolds (Einstein, Sasakian, etc.)
53C55 Global differential geometry of Hermitian and Kählerian manifolds
58D19 Group actions and symmetry properties

Citations:

Zbl 1337.53053

References:

[1] M. Abreu, Kähler geometry of toric manifolds in symplectic coordinates, Symplectic and contact topology: interactions and perspectives (Toronto, ON/Montreal, QC, 2001), Fields Inst. Commun., vol. 35, Amer. Math. Soc., Providence, RI, 2003, pp. 1-24.; · Zbl 1044.53051
[2] S. Calamai and D. Petrecca, On Calabi extremal Kähler-Ricci solitons, Proc. Amer. Math. Soc. 144 (2016), no. 2, 813-821. MR 3430856; · Zbl 1337.53053
[3] B. Chow et al., The Ricci Flow: Techniques and Applications: Geometric Aspects, Mathematical surveys and monographs, vol. 135, American Mathematical Society, 2007.; · Zbl 1157.53034
[4] S. K. Donaldson, Kähler geometry on toric manifolds, and some other manifolds with large symmetry, Handbook of geometric analysis. No. 1, Adv. Lect. Math. (ALM), vol. 7, Int. Press, Somerville, MA, 2008, pp. 29-75. MR 2483362; · Zbl 1161.53066
[5] F. Podestà and A. Spiro, Kähler-Ricci solitons on homogeneous toric bundles, J. Reine Angew. Math. 642 (2010), 109-127. MR 2658183; · Zbl 1210.14057
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