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48 results for Crofton formula

Developed new Crofton formulas for pseudo-Riemannian spaces.

problem Computing volumes and curvature integrals in pseudo-Riemannian space forms.
method Introduced Crofton formulas using distributions and Alesker's Radon transform.
result Explicit Crofton formulas for all isometry-invariant valuations on pseudo-Riemannian spaces.

This note generalizes the visual angle to convex sets in 3D space.

problem Analyzing geometric properties of convex sets in 3D space.
method Generalizing the visual angle to convex sets in Euclidean space and expressing geometric quantities in terms of integrals of functions related to the solid angle.
result Invariant quantities of the original convex set can be expressed by integrals of functions related to the solid angle.

Estimates average number of common zeros of Laplacian eigenfunctions on manifolds.

problem Estimating the average number of common zeros of Laplacian eigenfunctions on compact Riemannian manifolds.
method Application of Crofton's formula for the sphere.
result Proves an estimate for the average number of common zeros of eigenfunctions, showing it does not exceed a specific expression.

We prove new kinematic formulas for tensor valuations and simplify previously known Crofton formulas by using the recently developed algebraic theory of translation invariant valuations. The heart of the paper is the computation of the Alesker-Fourier transform on the large class of spherical valuations, which is achie…

2014-02-12abs ↗pdf ↗

We prove that the length difference between a closed periodic curve and its parallel curve at a sufficiently small distance is proportional to the rotation index. As an application, the rotation index of a curve could be estimated by means of Cauchy-Crofton formula.

2007-11-11abs ↗pdf ↗

We describe a hyperbolic version of the Ambartzumian-Pleijel identity. We use this identity to prove the hyperbolic Crofton formula and the hyperbolic isoperimetric inequality. This identity also provides a way to compute the chord length distribution for an ideal polygon in the hyperbolic plane. The analogous results …

2014-10-15abs ↗pdf ↗

We show that for every compact domain in a Euclidean space with d.c. (delta-convex) boundary there exists a unique Legendrian cycle such that the associated curvature measures fulfil a local version of the Gauss-Bonnet formula. This was known in dimensions two and three and was open in higher dimensions. In fact, we sh…

2012-09-11abs ↗pdf ↗

We construct a class of Finsler metrics in three-dimensional space such that all their geodesics are lines, but not all planes are extremal for their Hausdorff area functionals. This shows that if the Hausdorff measure is used as notion of volume on Finsler spaces, then totally geodesic submanifolds are not necessarily…

2004-08-30abs ↗pdf ↗

The paper proposes a new way to approximate Riemannian metrics using discrete wall systems.

problem Approximating Riemannian metrics and proving geometric conjectures.
method Discretization of metrics using walls and triangulations.
result The discrete filling area conjecture is equivalent to Gromov's original conjecture.

The article develops a mathematical theory for uniformly distributing points on surfaces.

problem Creating representative point clouds on surfaces and higher-dimensional manifolds.
method Using Cauchy Crofton formula and its generalizations from Integral Geometry.
result A rigorous mathematical theory for point clouds on various manifolds.

The paper explores connections between perimeter, area, and visual angle of convex sets.

problem Understanding geometric properties of convex sets through visual angle and related measurements.
method Establishing universal formulas and characterizing convex sets of constant width.
result Crofton's formula is the unique universal formula relating visual angle, length, and area.

In order to study large variations or fluctuations of finite or infinite sequences (time series), we bring to light an 1868 paper of Crofton and the (Cauchy-)Crofton theorem. After surveying occurrences of this result in the literature, we introduce the inconstancy of a sequence and we show why it seems more pertinent …

2009-10-07abs ↗pdf ↗

Classical integral geometry takes place in Euclidean space, but one can attempt to imitate it in any other metric space. In particular, one can attempt this in R^n equipped with the metric derived from the p-norm. This has, in effect, been investigated intensively for 1<p<\infty, but not for p=1. We show that integral …

2010-12-29abs ↗pdf ↗

The width ww of a curve γγ in Euclidean space RnR^n is the infimum of the distances between all pairs of parallel hyperplanes which bound γγ, while its inradius rr is the supremum of the radii of all spheres which are contained in the convex hull of γγ and are disjoint from γγ. We use a mixture of topological and…

2016-05-04abs ↗pdf ↗

Cauchy used infinitesimals in differential geometry and integral geometry.

problem Applying infinitesimals in differential and integral geometry.
method Using infinitesimals as numbers in differential and integral geometry.
result Valid application of infinitesimals in geometric probability, differential geometry, elasticity, and Dirac delta functions.

We define a new notion of total curvature, called net total curvature, for finite graphs embedded in Rn, and investigate its properties. Two guiding principles are given by Milnor's way of measuring the local crookedness of a Jordan curve via a Crofton-type formula, and by considering the double cover of a given graph …

2011-01-12abs ↗pdf ↗

We study the integral expression of a knot invariant obtained as the second coefficient in the perturbative expansion of Witten's Chern-Simons path integral associated with a knot. One of the integrals involved turns out to be a generalization of the classical Crofton integral on convex plane curves and it is related w…

1994-11-30abs ↗pdf ↗

Paper proves a fixed point formula and applies it to a new proof of Harish-Chandra's character formula.

problem Proving a fixed point formula for equivariant indices of elliptic differential operators.
method Fixed point formula for proper actions by connected semisimple Lie groups on manifolds.
result New proof of Harish-Chandra's character formula for discrete series representations.

Unified formula for surfaces in Euclidean or Lorentzian 3-space.

problem Describe surfaces in Euclidean or Lorentzian 3-space.
method Unified Kenmotsu-type formula for surfaces in Euclidean or Lorentzian 3-space.
result Unified single equation for Kenmotsu-type formulas in Euclidean and Lorentzian 3-space.

The study identifies types of manifolds using variational formulas and integral-differential formulas.

problem Identifying specific types of manifolds based on curvature properties.
method Established variational formulas for Ricci curvature bounds and used them to identify manifolds.
result Constant curvature, Einstein, and Ricci parallel manifolds identified with specific formulas.

The main result of the present paper is a coincidence formula for foliated manifolds. To prove this we establish Kuenneth formula, Poincare duality and intersection product in the context of tangential de Rham cohomology and homology of tangential currents. We apply the formula to get a dynamical Lefschetz formula for …

2003-06-02abs ↗pdf ↗