We show that complete conformally flat manifolds of dimension n > 3 with nonnegative Ricci curvature enjoy nice rigidity properties: they are either flat, or locally isometric to a product of a sphere and a line, or are globally conformally equivalent to R n or a spherical spaceform Sn/Γ. This extends previous results due to Q.-M. Cheng and B.-L. Chen and X.-P. Zhu. In this note, we study compl...

We classify all connected, simple, 3-regular graphs with girth at least 5 that are Ricci-flat. use the definition of Ricci curvature on given in Lin-Lu-Yau, Tohoku Math., 2011, which is a variation Ollivier, J. Funct. Anal., 2009. A graph Ricci-flat, if it has vanishing edges. show, only Ricci-flat cubic Petersen graph, Triplex and dodecahedral graph. This will correct classification Comm. Anal...

We generalize the previously studied cosmological solutions in D -dimensional gravity with an antisymmetric (p+2)form to the case when the spatial part of the metric is Ricci-flat rather than flat. These generalized solutions are characterized by a parallel self-dual or anti-self-dual charge density form Q of rank 2m and satisfy the condition Q > 0. As with the previous flat-space case, these e...

We present explicit constructions of complete Ricci-flat Kähler metrics that are asymptotic to cones over non-regular Sasaki-Einstein manifolds. The metrics are constructed from a complete Kähler-Einstein manifold (V, gV ) of positive Ricci curvature and admit a Hamiltonian two-form of order two. We obtain Ricci-flat Kähler metrics on the total spaces of (i) holomorphic C/Zp orbifold fibrations...

– in this paper we consider some (α ,β ) -metrics such as generalized kropina, matsumoto and f (α β )2α = + metrics, and obtain necessary and sufficient conditions for them to be einstein metrics when βis a constant killing form. then we prove with this assumption that the mentioned einstein metrics must beriemannian or ricci flat.

We study adiabatic limits of Ricci-flat Kähler metrics on a Calabi-Yau manifold which is the total space of a holomorphic fibration when the volume of the fibers goes to zero. By establishing some new a priori estimates for the relevant complex Monge-Ampère equation, we show that the Ricci-flat metrics collapse (away from the singular fibers) to a metric on the base of the fibration. This metri...

The three-dimensional Heisenberg group H3 has three left-invariant Lorentz metrics g1 , g2 and g3 as in [R92] . They are not isometric each other. In this paper, we characterize the left-invariant Lorentzian metric g1 as a Lorentz Ricci soliton. This Ricci soliton g1 is a shrinking non-gradient Ricci soliton. Likewise we prove that the isometry group of flat Euclid plane E(2) has Lorentz Ricci ...

In this paper, we study the dilation limit of solutions to the Ricci flow on manifolds with nonnegative curvature operator. We first show that such a dilation limit must be a product of a compact ancient Type I solution of the Ricci flow with flat factors. Then we show under the Type I normalized Ricci flow, the compact factor has a subsequence converge to a Ricci soliton.

Let X be a compact Kähler manifold with zero first Chern class, and let L be an ample line bundle overX . The pair (X,L) is called a polarized Calabi-Yaumanifold. By Yau’s proof of the Calabi conjecture, we know such a manifold carries a unique Ricci flat metric compatable with the polarization (cf. [37]). Thus, the moduli space of such Ricci flat Kähler metrics is the moduli space of complex s...

We determine the Killing spinors for a class of magnetic brane solutions with Minkowski worldvolume of the theory of AdS Einstein Maxwell theories in d dimensions. We also obtain curved magnetic brane solutions with Ricci-flat worldvolumes. If we demand that the curved brane solution admits Killing spinors, then its worldvolume must admit parallel spinors. Classes of Ricci-flat worldvolumes adm...