arXiv research

Study on functional ellipsoids to decompose the identity.

Using an idea of Voronoi in the geometric theory of positive definite quadratic forms, we give a transparent proof of John's characterization of the unique ellipsoid of maximum volume contained in a convex body. The same idea applies to the 'hard part' of a generalization of John's theorem and shows the difficulties of…

The paper applies a capillary John ellipsoid theorem to solve capillary curvature problems.

The paper proves a Bonnesen-type inequality for the real projective plane.

We present an affine-invariant random walk for drawing uniform random samples from a convex body $\mathcal{K} \subset \mathbb{R}^n$ that uses maximum volume inscribed ellipsoids, known as John's ellipsoids, for the proposal distribution. Our algorithm makes steps using uniform sampling from the John's ellipsoid of the …

Given a centrally symmetric convex body $K \subset \mathbb{R}^d$ and a positive number $λ$, we consider, among all ellipsoids $E \subset \mathbb{R}^d$ of volume $λ$, those that best approximate $K$ with respect to the symmetric difference metric, or equivalently that maximize the volume of $E\cap K$: these are the maxi…

We extend the model of stochastic bandits with adversarial corruption (Lykouriset al., 2018) to the stochastic linear optimization problem (Dani et al., 2008). Our algorithm is agnostic to the amount of corruption chosen by the adaptive adversary. The regret of the algorithm only increases linearly in the amount of cor…

We propose and analyze two new MCMC sampling algorithms, the Vaidya walk and the John walk, for generating samples from the uniform distribution over a polytope. Both random walks are sampling algorithms derived from interior point methods. The former is based on volumetric-logarithmic barrier introduced by Vaidya wher…

We generalize the maximal diameter sphere theorem due to Toponogov by means of the radial curvature. As a corollary to our main theorem, we prove that for a complete connected Riemannian $n$-manifold $M$ having radial sectional curvature at a point bounded from below by the radial curvature function of an ellipsoid of …

The paper finds a geometric way to minimize a convex function to construct isotropic measures.

Study eigenvalues of ellipsoids near a sphere, comparing to sphere's.

In his celebrated paper "Generic projections", John Mather has given a striking transversality theorem and its applications on generic projections. On the other hand, in this paper, two transversality theorems on generic linearly perturbed $C^r$ mappings are shown $(r\geq 1)$. Moreover, some applications of the two the…

We describe the geometry of geodesics on a Lorentz ellipsoid: give explicit formulas for the first integrals (pseudo-confocal coordinates), curvature, geodesically equivalent Riemannian metric, the invariant area-forms on the time- and space-like geodesics and invariant 1-form on the space of null geodesics. We prove a…

In this article we construct L--A representations of geodesic flows on quadrics and of billiard problems within ellipsoids in the pseudo--Euclidean spaces. A geometric interpretation of the integrability analogous to the classical Chasles theorem for symmetric ellipsoids is given. We also consider a generalization of t…

Given a positive function $u\in W^{1,n}$, we define its John-Nirenberg radius at point $x$ to be the supreme of the radius such that $\int_{B_t}|\nabla\log u|^n<ε_0^n$ when $n>2$, and $\int_{B_t}|\nabla u|^2<ε_0^2$ when $n=2$. We will show that for a collapsing sequence in a fixed conformal class under some curvature c…

The paper proves ellipsoids are the only centroaffine Tchebychev hyperovaloids.

The study characterizes quadrics among affine hyperspheres based on centroid collinearity of sections.

The study confirms most Cantor sets are in general position for all projections.

Study improves understanding of Ricci curvature in manifolds.

Minimal spheres found in ellipsoids with large axes.

Paper proves existence and gives construction of Symphonic map between ellipsoids.

The horizon and geodesic structure of static configurations generated by anisotropic conformal transforms of the Schwarzschild metric is analyzed. We construct the maximal analytic extension of such off--diagonal vacuum metrics and conclude that for small deformations there are different classes of vacuum solutions of …

Let $(M; g)$ be a smooth compact Riemiannian manifold without boundary and $g_{k}$ be a metric conformal to $g$. Suppose $vol(M; g_{k})+||R_{k}||_{L^{p}(M;g_{k})} < C$, where $R_{k}$ is the scalar curvature and $p > \frac{n}{2}$. We will use the 3-circle theorem and the John-Nirenberg inequality to study the bubble tre…

Study on rigidity with non-negative intermediate curvature on low-dimensional manifolds.

Many classical facts in Riemannian geometry have their pseudo-Riemannian analogs. For instance, the spaces of space-like and time-like geodesics on a pseudo-Riemannian manifold have natural symplectic structures (just like in the Riemannian case), while the space of light-like geodesics has a natural contact structure.…

CTEF fits ellipsoids to noisy data in any dimension.

The paper uses Seshadri constants to construct symplectic ellipsoid embeddings.

We construct new classes of exact solutions in metric--affine gravity (MAG) with string corrections by the antisymmetric $H$--field. The solutions are parametrized by generic off--diagonal metrics possessing noncommutative symmetry associated to anholonomy framerelations and related nonlinear connection (N--connection)…

Let Πbe a link projection in S^2. John Conway and later Francis Bonahon and Larry Siebenmann undertook to split $Π$ into canonical pieces. These pieces received different names: basic or polyhedral diagrams on one hand, rational, algebraic, bretzel, arborescent diagrams on the other hand. This paper proposes a thorough…

New minimal discs and annuli found in ellipsoids.

John Conway created pairs of domains that sound the same for a special kind of music.

The paper develops a method to create non-asymptotic confidence ellipsoids for linear regression without strong noise distribution assumptions.

Comparison theorems in centro-affine differential geometry

We discuss Darboux-Staude type of thread configurations for the ellipsoid similar to Chasles-Graves type of thread configurations for the ellipse. These threads are formed by rectilinear segments, geodesic and line of curvature segments on the considered ellipsoid and with tangents tangent to the given ellipsoid and a …

Jacobi solved geodesics on triaxial ellipsoids.

Study finds many nonplanar minimal spheres in elongated ellipsoids.

Study smoothings of singular intersections of ellipsoids.

Optimizes ellipsoids for uncertainty regions in parameter estimation.

Consider a $d\times d$ matrix $M$ whose rows are independent centered non-degenerate Gaussian vectors $ξ_1,...,ξ_d$ with covariance matrices $Σ_1,...,Σ_d$. Denote by $\mathcal{E}_i$ the location-dispersion ellipsoid of $ξ_i:\mathcal{E}_i={\mathbf{x}\in\mathbb{R}^d : \mathbf{x}^\topΣ_i^{-1} \mathbf{x}\leqslant1}$. We sh…

Discrete analogues of ellipsoids with preserved circular cross sections.

Ellipsoids host infinitely many minimal tori, bifurcating from a 2-torus orbit.

We develop an efficient algorithm to find confidence ellipsoids with volume guarantees in high dimensions.

Study smoothings of ellipsoid intersections with singularities.

Uniform convexity in divisible domains leads to hyperbolic geometry.

Self-focal points on ellipsoids of dimension 3 or higher are rare.

Geodesic algorithms extended to arbitrary ellipsoids.

Ellipsoids approach Gaussian distribution in high dimensions.

The paper studies the number of normals to ellipsoids and their intersections with caustics.