The Green function on spheres in 3D implies the surface is a round sphere.
problem Verifying a conjecture about the Green function on spheres.
method Analyzing the Green function form and its properties on a sphere.
result Closed C2 embedded surfaces with the specified Green function are necessarily round spheres. The first part of the paper is to improve the fundamental theory of isoparametric functions on general Riemannian manifolds. Next we focus our attention on exotic spheres, especially on "exotic" 4-spheres (if exist) and the Gromoll-Meyer sphere. In particular, as one of main results we prove: there exists no properly t…
Proves optimal regularity for sphere minimizers in 3-sphere.
problem Finding optimal regularity for sphere minimizers.
method Proves C1,1 regularity for minimizers of prescribed mean curvature over isotopy classes. result Proves optimal C1,1 regularity for minimizers. Green functions for GJMS operators on spheres derived, linking geometry and rigidity.
problem Deriving Green functions for GJMS operators on spheres.
method Explicit representation formulae derived using Gegenbauer polynomials.
result Spheres uniquely characterized by their Green functions, with strong rigidity theorems for n=3,4,5. The paper studies geodesics and isoparametric functions on Finsler spheres.
problem Analyzing geodesics and isoparametric functions on Finsler spheres.
method Global expressions of geodesics and isoparametric functions derived using navigation and Cartan-Münzner polynomials.
result Construction of isoparametric families and focal submanifolds.
This paper extends widely the work in \cite{GT13}. Existence and non-existence results of isoparametric functions on exotic spheres and Eells-Kuiper projective planes are established. In particular, every homotopy n-sphere (n>4) carries an isoparametric function (with certain metric) with 2 points as the focal set,…
Constructs fat, shellable 3-spheres with specific f-vectors.
problem Defines and constructs fat 3-spheres.
method Constructs strongly regular CW 3-spheres that are both shellable and dual shellable.
result Constructs arbitrarily fat, shellable and dual shellable 3-spheres with specific f-vectors. Functional determinant for mixed signature sphere products depends on sphere dimensions and parity.
problem Determining the functional determinant for scalar fields on mixed signature sphere products.
method Analyzing the GJMS operator on SqimesSp to derive the functional determinant. result The functional determinant depends only on the total dimension and parity of the sphere dimensions.
Two non-Morse-Bott Chern-Simons functions on homology 3-spheres.
problem Finding homology 3-spheres with non-Morse-Bott Chern-Simons functions.
method Constructing specific surgeries on torus knots.
result Examples of homology 3-spheres with non-Morse-Bott Chern-Simons functions.
Morse theory connects low energy submanifolds in 3-sphere.
problem Understanding low energy submanifolds in the 3-sphere.
method Morse-theoretic techniques and negative gradient flow.
result Constructs connections between low energy critical submanifolds.
Two spheres found with specific curvature constraints.
problem Existence of spheres with prescribed mean curvature.
method Proved existence of at least two embedded spheres with curvature h satisfying pinching condition. result Existence of at least two embedded spheres with prescribed mean curvature h. 3D spheres with certain properties approach the round sphere.
problem Flexibility of Llarull's Theorem in dimension 3.
method Proof based on spacetime harmonic functions.
result 3D spheres with bounded Cheeger isoperimetric constant and scalar curvatures tending to 6 approach the round sphere.
Proves existence of curves with constant curvature in a sphere.
problem Existence of curves with constant geodesic curvature in a Riemannian 2-sphere.
method Develops a min-max scheme for a weighted length functional.
result Proves existence for almost every prescribed curvature.
In this article, we are interested in the problem of extending the germ of a smooth function f~ defined along the standard sphere of dimension n to a function defined on the ball which has no critical points. The article gives a necessary condition using the Morse chain complex associated to the function f…
Study classifies Morse functions with 4 critical points on immersed 2-spheres.
problem Classifying Morse functions with 4 critical points on immersed 2-spheres.
method Used dual graph of immersion and Reeb graphs to classify functions.
result Found all possible structures of the functions.
The nonzero level sets of a homogeneous, logarithmically homogeneous, or translationally homogeneous function are affine spheres if and only if the Hessian determinant of the function is a multiple of a power or an exponential of the function. In particular, the nonzero level sets of a homogeneous polynomial are proper…
Falsehood of Pólya's conjecture for spheres shown.
problem Disproving Pólya's eigenvalue conjecture for spheres.
method Comparison of Laplace spectrum and Weyl function of spheres.
result No analogue of Pólya's conjecture holds for spheres.
We study the negative gradient flow of the spinorial energy functional (introduced by Ammann, Weiß, and Witt) on 3-dimensional Berger spheres. For a certain class of spinors we show that the Berger spheres collapse to a 2-dimensional sphere. Moreover, for special cases, we prove that the volume-normalized standard 3-sp…
Real algebraic structures help classify overtwisted contact 3-spheres.
problem Classifying overtwisted contact structures on 3-spheres.
method Using real algebraic functions and open book decompositions.
result Most overtwisted contact structures are real algebraic.
New inequality on sphere generalizes circle inequality.
problem Generalizing circle inequality to sphere.
method Develops a new inequality on the sphere that incorporates mass center deviation.
result Improves Aubin's inequality and Onofri's inequality.
Tautness of submanifolds in spheres is preserved under Lie sphere transformations.
problem Invariance of tautness under Lie sphere transformations.
method Extending tautness definition to Legendre submanifolds and using Lie sphere transformations to show invariance.
result Tautness is invariant under Lie sphere transformations.
Study calculates the elastic energy of curves on a sphere.
problem Elastic energy of curves on a sphere.
method Introduced p-curvature functional for rectifiable curves in the sphere and proved its finiteness. result The p-curvature functional agrees with the integral of geodesic curvature raised to the power p for curves in W2,p. Critical trajectories in a sphere are found for a specific bending functional.
problem Finding closed trajectories in a sphere for a specific bending functional.
method Existence of infinitely many closed trajectories shown for a given Lagrange multiplier.
result Existence of closed trajectories dependent on a pair of relatively prime natural numbers.
New geometric invariant from min-max width of spheres on Riemannian 2-spheres.
problem Understanding the min-max width of spheres associated to distance functions.
method Application of min-max methods to pairs of points on Riemannian 2-spheres.
result The min-max width does not always equal half the length of a simple closed geodesic.
The paper studies biharmonic functions and bi-eigenfunctions on spheres and model spaces.
problem Characterizing biharmonic functions and eigenfunctions on model spaces.
method Analyzes bi-Laplacian on spheres, derives integral formulas for biharmonic solutions, and classifies proper biharmonic functions.
result Proper biharmonic functions on model spaces can be constructed from eigenfunctions of the factor sphere.
This is the first comprehensive introduction to the authors' recent attempts toward a better understanding of the global concepts behind spinor representations of surfaces in 3-space. The important new aspect is a quaternionic-valued function theory, whose "meromorphic functions" are conformal maps into quaternions, wh…
Research extends geodesic length function study to three holed sphere.
problem Geodesic length function on orbifolds.
method Extending previous work on punctured torus to three holed sphere and related orbifolds.
result Extension to three holed sphere and related orbifolds.
Study shortest geodesics on flat cone spheres with conical singularities.
problem Understanding the distribution of shortest geodesics on flat cone spheres.
method Proved a recurrent relation on the distribution of the length of shortest geodesics with respect to Thurston's volume form.
result Proved a recurrent relation on the distribution of the length of shortest geodesics.
The paper proves manifolds homeomorphic to spheres under specific Morse-Bott conditions.
problem Understanding the conditions for manifolds to be homeomorphic to spheres.
method Using Morse-Bott functions and critical submanifolds.
result Closed, smooth manifolds with specific Morse-Bott functions are homeomorphic to spheres.
In this paper we investigate the flow of surfaces by a class of symmetric functions of the principal curvatures with a mixed volume constraint. We consider compact surfaces without boundary that can be written as a graph over a sphere. The linearisation of the resulting fully nonlinear PDE is used to prove a short time…
In the field of optimal transport theory, an optimal map is known to be a gradient map of a potential function satisfying cost-convexity. In this paper, the Jacobian determinant of a gradient map is shown to be log-concave with respect to a convex combination of the potential functions when the underlying manifold is t…
In this paper the regularity of optimal transportation potentials defined on round spheres is investigated. Specifically, this research generalises the calculations done by Loeper, where he showed that the strong (A3) condition of Trudinger and Wang is satisfied on the round sphere, when the cost-function is the geodes…
New method constructs translationally equivariant hyperbolic affine spheres.
problem Constructing translationally equivariant hyperbolic affine spheres.
method Noncompact Iwasawa factorization via DPW method and Weierstrass elliptic functions.
result Every translationally equivariant hyperbolic affine sphere is equiaffinely equivalent to one with a circle, hyperbola, or parabola slice curve.
Invariant detects triple points in sphere immersions.
problem Detecting regular homotopy classes of triple-point-free sphere immersions.
method Defining an invariant using a directed tree and integer-valued function.
result Space of triple-point-free spheres has infinitely many regular homotopy classes.
We construct new explicit proper r-harmonic functions on the standard n-dimensional sphere S^n and hyperbolic space H^n for any r\ge 1 and n\ge 2.
Proves existence of special 2-spheres in curved 3-spaces.
problem Existence of constant mean curvature 2-spheres in Riemannian 3-spheres.
method Develops a min-max scheme for a weighted Dirichlet energy functional, using bi-harmonic approximation, derivative estimates, and Morse index estimates.
result Proves existence for almost every mean curvature and all for positively curved 3-spheres.
New optimal surfaces found in Heisenberg group defy Euclidean sphere optimality.
problem Optimizing mean curvature in Heisenberg group sub-Riemannian setting.
method Developed variational theory, established first and second variation formulas, introduced new critical surfaces.
result Identified and characterized a new family of rotationally invariant critical surfaces, the Pansu-Minkowski spheres.
Eigenvalues on spheres are compared to the unit round sphere, proving a sharp bound and equality condition.
problem Comparing eigenvalues of spheres under different metrics.
method Analyzing Laplace eigenvalues and using Alexandrov spaces.
result Equality of eigenvalues forces metrics to be isometric to the unit round sphere.
The Funk--Minkowski transform F associates a function f on the sphere S2 with its mean values (integrals) along all great circles of the sphere. Thepresented analytical inversion formula reconstruct the unknown function f completely if two Funk--Minkowski transforms, Ff and ${…
In this paper we show novel underlying connections between fractional powers of the Laplacian on the unit sphere and functions from analytic number theory and differential geometry, like the Hurwitz zeta function and the Minakshisundaram zeta function. Inspired by Minakshisundaram's ideas, we find a precise pointwise d…
We study a functional on the boundary of a compact Riemannian 3-manifold of nonnegative scalar curvature. The functional arises as the second variation of the Wang-Yau quasi-local energy in general relativity. We prove that the functional is positive definite on large coordinate spheres, and more general on nearly roun…
Sharp inequality proven for symmetric functions on a 4D sphere.
problem Proving a sharp Beckner's inequality for axially symmetric functions on S4. method Utilized pointwise properties of Gegenbauer polynomials.
result Sharp Beckner's inequality established for axially symmetric functions on S4. The paper constructs metrics on spheres with families of minimal hypersurfaces.
problem Finding Riemannian metrics on spheres with specific families of minimal hypersurfaces.
method Used Nash-Moser Inverse Function Theorem in the tame maps setting.
result Generalized Guillemin's theorem for Zoll families of minimal hypersurfaces.
We study the growth of harmonic functions on complete Riemann-ian manifolds where the extrinsic diameter of geodesic spheres is sublinear. It is an generalization of a result of A. Kazue. We also get a Cheng and Yau estimates for the gradient of harmonic functions.
We prove that the number of combinatorially distinct causal 3-dimensional triangulations homeomorphic to the 3-dimensional sphere is bounded by an exponential function of the number of tetrahedra. It is also proven that the number of combinatorially distinct causal 4-dimensional triangulations homeomorphic to the 4-sph…
The paper shows how to make certain sets on a sphere smooth and flat.
problem Understanding the smoothness of level-sets of distance functions on spheres.
method Isometric embedding into Rn+2, and analysis on codimension-2 graphs. result Level-sets of distance functions on spheres are C1,1-rectifiable. Characterizes CR manifolds as critical points of an energy functional.
problem Understanding homogeneous three-dimensional CR manifolds.
method Uses an energy functional dependent on Webster curvature and torsion.
result Identifies Rossi spheres as a specific type of critical point.
We explicitly write down all eigenvalues of the Rumin Laplacian on the standard contact spheres, and express the analytic torsion functions associated with the {Rumin complex} in terms of the Riemann zeta function. In particular, we find that the functions vanish at the origin and determine the analytic torsions.