Optimizes biharmonic map regularity using stratification methods.
problem Improving the known almost optimal regularity of biharmonic maps.
method Quantitative stratification method.
result Optimal regularity results for minimizing biharmonic maps.
The paper improves estimates on singular sets in manifolds with integral curvature bounds.
problem Estimating the singular set of manifolds with integral curvature bounds.
method Using Gromov-Hausdorff limits and Cheeger-Naber methods.
result Improved Minkowski dimension estimate for singular sets.
Extends space theory to singular spaces.
problem Analyzing Ricci flows of bounded curvature.
method Generalizes Cheeger, Colding, and Naber's theory.
result Theory applies to singular space limits of manifolds.
Study curvature growth in 4D singularity models using Perelman's method.
problem Estimating curvature growth in 4D gradient Ricci soliton singularity models.
method Applied Perelman's point selection, Cheeger and Naber's fundamental result, and topological lemmas.
result Developed estimates for curvature growth in singularity models.
Unified proof of smooth fibration theorems for collapsed manifolds.
problem Smooth fibration theorems for collapsed manifolds with Ricci curvature bounded below.
method Generalized Reifenberg condition and transformation technique for almost splitting maps.
result Unified proof of smooth fibration theorems in many previous works.
Study controls curvature in Ricci flows using necks.
problem Controlling curvature in Ricci flows.
method Introducing necks of maximal symmetry and decomposing curvature into uniform bounds.
result Established L1-bounds on Riemann curvature tensor. The paper constructs manifolds with infinite holes from a given manifold.
problem Creating manifolds with infinite holes from a given manifold.
method Constructing a sequence of (n+2)-dimensional manifolds (Mi,gi) with mRicgi>λ that approximate the original manifold (X,h) and have an infinite number of connected components. result The constructed manifolds (Xε) have dense boundary with an infinite number of connected components and no open subset topologically a manifold. Paper reconciles different Ricci flow approaches and proves weak solutions.
problem Proving weak solutions for Ricci flows with singularities.
method Introducing a novel hitting estimate for Brownian motion, compensating for lack of lower heat kernel bounds.
result Every noncollapsed limit of Ricci flows and singular Ricci flows are weak solutions.
3D Ricci flows have bounded diameter before Type I singularities.
problem Bounding the diameter of 3D Ricci flows before Type I singularities.
method Introduced a neck-region concept and proved packing measure Ahlfors regularity.
result Uniformly bounded diameter up to Type I singular time.
We show that a shrinking Ricci soliton with positive sectional curvature must be compact. This extends a result of Perelman in dimension three and improves a result of Naber in dimension four, respectively.
Sharp Gaussian isoperimetry proven along Ricci flow.
problem Proving sharp Gaussian isoperimetric inequality for Ricci flow.
method Using monotonicity formula to prove inequality.
result Exact Gaussian enlargement theorem and concentration estimates.
This is a survey article with a limited list of references (as required by the publisher) which appears in the Encyclopedia of Mathematical Physics, eds. J.-P. Francoise, G.L. Naber and Tsou S.T. Oxford: Elsevier, 2006. vol.4, pp.94--104.
The paper extends regularity for p-minimizing maps using a Reifenberg Theorem.
problem Quantitative regularity of p-minimizing maps between Riemannian manifolds. method Stratification of singular points based on almost-symmetries, followed by application of a Reifenberg-type Theorem.
result Upper bound on the Minkowski content of the singular set, and k-rectifiability of the singular set. Study on energy-minimizing structures in complex geometry.
problem Existence and regularity of harmonic almost complex structures.
method Inspired by harmonic map theory, proving results similar to Schoen-Uhlenbeck and Cheeger-Naber.
result Proved existence and regularity similar to harmonic map theory.
Study Brownian motion on Perelman's almost Ricci-flat manifold, proving convergence to Ricci flow limits.
problem Characterize Brownian motion and stochastic transport on Perelman's manifold.
method Construct sequences of projected Brownian motions and stochastic parallel transports, analyze Laplace and horizontal Laplacian martingale problems.
result Convergence of projected Brownian motions and stochastic parallel transports to Ricci flow limits as No∞. We show that if X is a limit of n-dimensional Riemannian manifolds with Ricci curvature bounded below and γ is a limit geodesic in X then along the interior of γ same scale measure metric tangent cones Tγ(t)X are Hölder continuous with respect to measured Gromov-Hausdorff topology and have the same dimen…
New Calabi-Yau metrics found on C^n for n>=3.
problem Finding Calabi-Yau metrics on complex manifolds.
method Constructing metrics with maximal volume growth and singular tangent cones.
result Infinitely many complete Calabi-Yau metrics on C^n.
In arXiv:1005.3255 we proved an orbifold Cheeger-Gromov compactness theorem for complete 4d Ricci shrinkers with a lower bound for the entropy, an upper bound for the Euler characterisic, and a lower bound for the gradient of the potential at large distances. In this note, we show that the last two assumptions in fact …
The paper characterizes upper bounds of Bakry-Emery curvature.
problem Characterizing upper bounds of Bakry-Emery curvature on Riemannian manifolds.
method Using functional inequalities on path space.
result Characterizations for upper bounds of Bakry-Emery curvature are provided.
In this note we prove convexity, in the sense of Colding-Naber, of the regular set of solutions to some complex Monge-Ampere equations with conical singularities along simple normal crossing divisors. In particular, any two points in the regular set can be joined by a smooth minimal geodesic lying entirely in the regul…
Integral estimates for Ricci flows up to singular time.
problem Integral estimates for curvature tensor in Type I Ricci flows.
method Adapted quantitative stratification technique.
result Partial extension of curvature estimates to higher dimensions.
Convexity proven in Ricci shrinker limit spaces.
problem Understanding the structure of Ricci shrinker limits.
method Regular-singular decomposition and parabolic smoothing of distance functions.
result The regular part of any Ricci shrinker limit space is convex.
We define several notions of singular set for Type I Ricci flows and show that they all coincide. In order to do this, we prove that blow-ups around singular points converge to nontrivial gradient shrinking solitons, thus extending work of Naber. As a by-product we conclude that the volume of a finite-volume singular s…
The study establishes inequalities on path space for sub-Riemannian manifolds.
problem Understanding functional inequalities on path space for sub-Riemannian manifolds.
method Derivative and integration by parts formulae on path space with respect to a natural gradient operator, showing bounds of horizontal Ricci curvature.
result Established functional inequalities on path space analogous to Riemannian geometry.
We study blow-ups around fixed points at Type I singularities of the Ricci flow on closed manifolds using Perelman's W-functional. First, we give an alternative proof of the result obtained by Naber and Enders-Müller-Topping that blow-up limits are non-flat gradient shrinking Ricci solitons. Our second and main result …
The paper bounds the shortest closed geodesic length in 4D manifolds.
problem Finding the shortest closed geodesic in 4D manifolds with specific curvature and volume constraints.
method Utilizes recent theorems on diffeomorphism finiteness by J. Cheeger and A. Naber.
result The length of a shortest closed geodesic is bounded by a function F(v,D) that depends on volume v and diameter D. Let $\cM$ be a Brakke flow of n-dimensional surfaces in RN. The singular set $\cS\subset\cM$ has a stratification $\cS^0\subset\cS^1\subset...\cS$, where $X\in \cS^j$ if no tangent flow at X has more than j symmetries. Here, we define quantitative singular strata $\cS^j_{η,r}$ satisfying $\cup_{η>0}\cap_{0<r} …
Study shows how reference measure behaves on RCD spaces through charts.
problem Understanding the behavior of reference measure on RCD spaces.
method Used charts constructed by Mondino and Naber, and a recent paper by De Philippis-Rindler.
result Push-forward of reference measure is absolutely continuous with Lebesgue measure.
The paper examines the geometry and topology of Sasaki-Ricci solitons, proving they are either connected at infinity or compact.
problem Understanding the geometry and topology of Sasaki-Ricci solitons.
method Analyzing the properties of complete gradient shrinking Sasaki-Ricci solitons, proving connectedness at infinity and compactness under certain curvature conditions.
result Proves that Sasaki-Ricci solitons are either connected at infinity or compact, generalizing results from previous studies.
Paper classifies 3D breathers and generalizes Ricci soliton results.
problem Classifying and understanding Ricci solitons and breathers.
method Developed a condition for the existence of asymptotic shrinking gradient Ricci solitons.
result Every complete shrinking Ricci soliton with bounded Ricci curvature is gradient.
Improved optimal regularity for harmonic almost complex structures.
problem Establishing optimal regularity for harmonic almost complex structures.
method Quantitative stratification method and rectifiability of singular strata.
result Optimal regularity theory for energy minimizing harmonic almost complex structures.
Extends positive mass theorem to arbitrary dimensions using a new inductive scheme.
problem Overcoming singularities in the Schoen-Yau proof for arbitrary dimensions.
method Inductive scheme combining shielding principle, conformal blow-up, and Cheeger-Naber bound.
result Proof of positive mass theorem in arbitrary dimensions.
The paper studies harmonic map flows and proves rectifiability of singular sets.
problem Understanding the structure of singular sets in harmonic map flows.
method Investigates the stratification theory for suitable solutions using tangent measures.
result Each time slice of the singular set is rectifiable.
Study fractional Allen-Cahn equation and nonlocal minimal surfaces, improving energy and perimeter estimates.
problem Properties of solutions to fractional Allen-Cahn equation and stationary nonlocal minimal surfaces.
method Quantitative stratification principle applied to fractional Allen-Cahn equation, leading to optimal estimates.
result Sharp potential energy and perimeter estimates for fractional Allen-Cahn equation and nonlocal minimal surfaces.
The paper proves regularity for minimal surfaces near polyhedral cones.
problem Understanding the regularity of minimal surfaces near polyhedral cones.
method Adapting Simon's method and establishing C1,α-regularity for minimal varifolds. result Proves C1,α-regularity for minimal varifolds near polyhedral cones. New examples challenge Geroch conjecture stability.
problem Stability of the Geroch conjecture in warped products.
method Constructing warped-product manifolds with specific curvature properties.
result First counterexample to Sormani's conjecture on stability.
The stability of the Yamabe invariant of S3 is discussed.
problem Stability of the Yamabe invariant of S3. method Analysis of asymptotically flat metrics with vanishing scalar curvature and nearly Euclidean L2 Sobolev inequality. result If a manifold (R3,g) carries a suitably normalized, positive solution to Δgw+λw5=0, then w must be close to a conformal factor transforming Euclidean space into a round sphere. Estimates on Einstein manifolds improve Brownian motion behavior and curvature limits.
problem Improving estimates on Einstein manifolds for Brownian motion behavior.
method Generalizing Benjamini-Pemantle-Peres estimate to manifolds with Ricci curvature bounds.
result Sharp estimates for Brownian motion on high curvature parts of Ricci-flat manifolds.
Generalizes Bochner formula to path space for Ricci flow.
problem Characterize solutions of the Ricci flow.
method Generalizes Bochner formula to parabolic path space.
result Characterizations of the Ricci flow from Bochner inequalities.
New examples of manifolds in tangent cones of non-collapsed Ricci limit spaces.
problem Uncertainty in homeomorphism types of tangent cones of non-collapsed Ricci limit spaces.
method Construction of limit spaces in all dimensions at least 5.
result Any finite collection of manifolds can appear as cross sections of tangent cones of the same point.
Gradient Ricci solitons can be extended to non-gradient Ricci solitons using energy function.
problem Extending the geometry of gradient Ricci solitons to non-gradient Ricci solitons.
method Using energy function E to study the geometry. result A non-steady Ricci soliton with symmetric covariant derivative is gradient.
Study bounds singular set of minimal hypersurfaces with index control.
problem Estimating singular set size of minimal hypersurfaces.
method Finite index and null singular set conditions on integral varifolds.
result Local measure bounds on singular set and upper Minkowski content.
Sharp lower bounds for eigenvalues on weighted p-Laplacian manifolds.
problem Estimating the first nonzero eigenvalue of the weighted p-Laplacian on compact manifolds.
method Sharp gradient comparison theorem and modulus of continuity estimates.
result Proves sharp lower bound estimates for the first nonzero eigenvalue.
Study of splitting maps in Type I Ricci flows for understanding singular set structure.
problem Understanding the structure of the singular set in non-collapsed Ricci limit spaces.
method Construction and investigation of almost splitting maps on Ricci flows that are almost self-similar.
result Sharp splitting maps remain splitting maps at smaller scales under certain conditions.
Study confirms conjectures on Ricci limit spaces and their topological properties.
problem Understanding the topological structure of noncollapsed Ricci limit spaces.
method Analysis of tangent cones and application of manifold recognition theorems.
result Cross-sections of tangent cones at points in 4D spaces are homeomorphic to a fixed spherical space form.
Paper proves ε-regularity for shrinking Ricci solitons and Ricci flows.
problem Proving ε-regularity for critical metrics and Ricci flows.
method Constructing counterexamples and proving ε-regularity theorems.
result Proves ε-regularity for 4-dimensional shrinking Ricci solitons and partially confirms for Ricci flows.
Researchers modify dp distance to handle long, thin splines.
problem Maintaining stability in convergence metrics with scalar curvature approaching positivity.
method Introducing and analyzing a modified dp distance to handle persistent splines. result The modified dp distance provides a stable estimate, useful for geometric stability. This paper studies the convergence of penalized energy to harmonic maps in Riemannian manifolds.
problem Analyzing the convergence of penalized energy to harmonic maps in Riemannian manifolds.
method Using the penalized energy functional and weak convergence techniques, the paper proves the energy identity for Ginzburg-Landau approximation of harmonic maps.
result The defect measure ν can be expressed as the sum of energies of harmonic spheres for arbitrary manifolds.