arXiv research

Revisits Koiso's rigid metrics on complex projective spaces.

Study on complex Grassmannians' rigidity using Einstein deformations.

We study infinitesimal Einstein deformations on compact flat manifolds and on product manifolds. Moreover, we prove refinements of results by Koiso and Bourguignon which yield obstructions on the existence of infinitesimal Einstein deformations under certain curvature conditions.

Study second order integrability of Einstein deformations on Riemannian and Kähler manifolds.

In this note, stimulated by the existence result of Futaki-Ono-Wang for toric Sasaki-Einstein metrics, we obtain new examples of Sasaki-Einstein metrics on S^1-bundles associated to canonical line bundles of P^1-bundles over Kähler-Einstein Fano manifolds, even though the Futaki's obstruction does not vanish. Here the …

This note analyzes the normal form of gradient Ricci 4-solitons.

By extending Koiso's examples to the non-compact case, we construct complete gradient Kahler-Ricci solitons of various types on certain holomorphic line bundles over compact Kahler-Einstein manifolds. Moreover, a uniformization result on steady gradient Kahler-Ricci solitons with non-negative Ricci curvature is obtaine…

We consider the non-trivial Ricci soliton on $\mathbb{CP}^2\#\overline{\mathbb{CP}^2}$ constructed by Koiso and Cao. It is a Kähler metric invariant by the $U(2)$ action on $\mathbb{CP}^2\#\overline{\mathbb{CP}^2}$. We study its Yamabe equation and prove it has exactly one $U(2)-$invariant solution up to homothecies.

The paper decomposes metrics on manifolds with boundaries.

In Riemannian geometry the prescribed Ricci curvature problem is as follows: given a smooth manifold $M$ and a symmetric 2-tensor $r$, construct a metric on $M$ whose Ricci tensor equals $r$. In particular, DeTurck and Koiso proved the following celebrated result: the Ricci curvature uniquely determines the Levi-Civita…

Let (M,g) be a compact oriented Einstein 4-manifold. Write R-plus for the part of the curvature operator of g which acts on self-dual 2-forms. We prove that if R-plus is negative definite then g is locally rigid: any other Einstein metric near to g is isometric to it. This is a chiral generalisation of Koiso's Theorem,…

The paper proves stability for a modified Bach flow on various manifolds.

In this note, using Calabi's method, we construct rotationally symmetric Kahler-Ricci solitons on the total space of direct sum of fixed hermitian line bundle and its projective compactification, where the curvature of hermitian line bundle is Kahler-Einstein. These examples generalize the construction of Koiso, Cao an…

There are several types of equation of motion of elastic wires. In this paper, we treat an equation taking account of the thickness of wire. The equation was introduced by Caflisch and Maddocks on plane curves, and they proved the existence of solutions. Koiso and Sugimoto generalized the result to any dimensional Eucl…

English translation of "Solitony Ricciego" (Wiadomości Matematyczne 48, 2012, no. 1, pp. 1-32). Despite the general-sounding title, the text covers just a few narrow topics: Perelman's proof of the fact that compact Ricci solitons are of the gradient type, and a detailed unified description of Page's and Berard Bergery…

Study the deformation theory of Einstein-Yang-Mills system on compact manifolds.

Establishes metrics with positive curvature on projective line bundles.

Given a compact Fano Kähler manifold (M,J) with a Kähler Ricci soliton g, we consider smooth families {J_t} of complex deformations of (M,J) which are invariant under the action of a maximal torus T in the full isometry group of (M,g). We prove that, under a certain condition on the spectrum of the Laplacian of g, ther…

Study on stability of Einstein metrics on symmetric spaces.

Rigidity of Fubini-Study metric on odd complex Grassmannians.

We study a class of asymptotically cylindrical Ricci-flat Kähler metrics arising on quasiprojective manifolds. Using the Calabi--Yau geometry and analysis and the Kodaira--Kuranishi--Spencer theory and building up on results of N.Koiso for the case of compact manifolds, we show that under rather general hypotheses any …

Study shows unique Einstein metrics on $SU_{2n+1}$ and related spaces.

This paper studies torsion obstructions to complex sections on manifolds.

Study stability of non-Kähler Calabi-Yau metrics using critical points of generalized Einstein Hilbert action.

Fewer obstructions for small graphs in knotless embedding.

3028 obstructions found for embedding without knots.

We prove that the quasi-Einstein metrics found by Lü, Page and Pope on $\mathbb{C}P^{1}$-bundles over Fano Kähler-Einstein bases are conformally Kähler and that the Kähler class of the conformal metric is a multiple of the first Chern class. A detailed study of the lowest-dimensional example of such metrics on $\mathbb…

The paper develops obstructions for embedding 2D complexes into 4D space.

Global obstructions found for conformally Einstein metrics in 6D.

Complete surgery obstructions for manifolds with finite fundamental group, disproving a conjecture.

Given a polarized manifold there are obstructions for asymptotic Chow semistability described as integral invariants. One of them is an obstruction to the existence for the first Chern class of the polarization to admit a constant scalar curvature Kähler (cscK) metric. A natural question is whether or not the other obs…

The article classifies cubiquitous sublattices and applies them to branched covers.

For a 3-manifold with torus boundary admitting an appropriate involution, we show that Khovanov homology provides obstructions to certain exceptional Dehn fillings. For example, given a strongly invertible knot in S^3, we give obstructions to lens space surgeries, as well as obstructions to surgeries with finite fundam…

New obstructions found for smooth desingularization of compact Einstein orbifolds.

For $\ell >1$, we develop $L^{(2)}$-signature obstructions for $(4\ell-3)$-dimensional knots with metabelian knot groups to be doubly slice. For each $\ell>1$, we construct an infinite family of knots on which our obstructions are non-zero, but for which double sliceness is not obstructed by any previously known invari…

Study identifies obstructions for solving a 4th-order boundary problem.

Developing a singular dimension descent method for positive scalar curvature obstructions

Study Euler obstruction of 1-forms on determinantal singularities.

Proves Massey's theorems on complex structure obstructions.

The paper explores properties of CR hypersurfaces and their flatness.

On a manifold of dimension at least six, let $(g,τ)$ be a pair consisting of a Kähler metric g which is locally Kähler irreducible, and a nonconstant smooth function $τ$. Off the zero set of $τ$, if the metric $\hat{g}=g/τ^2$ is a gradient Ricci soliton which has soliton function $1/τ$, we show that $\hat{g}$ is Kähler…

Study on a specific obstruction in four-dimensional geometry.

Introduce generalized Ueda obstruction classes for line bundles and apply them to non-semi-positivity.

Surgery obstructions extended to integer homology spheres using Heegaard Floer homology.

Extended solitons show constant curvature on compact manifolds.

Study the topological information of map germs using Euler obstruction.

New obstructions show some 4-manifold homeomorphisms are pseudo-isotopic but not isotopic.

Geometrically, a new obstruction is found for 4-manifold realizations.