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We investigate geometric properties of surfaces given by certain formulae. In particular, we calculate the singular curvature and the limiting normal curvature of such surfaces along the set of singular points consisting of singular points…

Differential Geometry · Mathematics 2020-03-25 Yoshiki Matsushita , Takuya Nakashima , Keisuke Teramoto

Polyhedral surfaces are fundamental objects in architectural geometry and industrial design. Whereas closeness of a given mesh to a smooth reference surface and its suitability for numerical simulations were already studied extensively, the…

Metric Geometry · Mathematics 2017-03-17 Felix Günther , Caigui Jiang , Helmut Pottmann

The Universe is a physical object. Physical objects have shapes and sizes. General relativity is insufficient to describe the global shape and size of the Universe: the Hilbert-Einstein equations only treat limiting quantities towards an…

Astrophysics · Physics 2007-05-23 B. F. Roukema

We survey many of the important properties of spherically symmetric spacetimes as follows. We present several different ways of describing a spherically symmetric spacetime and the resulting metrics. We then focus our discussion on an…

General Relativity and Quantum Cosmology · Physics 2014-10-10 Alan R. Parry

We discuss design techniques for catadioptric sensors that realize given projections. In general, these problems do not have solutions, but approximate solutions may often be found that are visually acceptable. There are several methods to…

Computer Vision and Pattern Recognition · Computer Science 2007-05-23 R. Andrew Hicks

Reflector-normal angles and reflector-curvature parameters are the principal geometric attributes used in seismic interpretation for characterizing the orientations and shapes, respectively, of geological reflecting surfaces. Commonly, the…

Geophysics · Physics 2023-02-01 Igor Ravve , Anne-Laure Tertois , Bruno de Ribet , Zvi Koren

We give a relationship that yields an effective geometric way of evaluating mean curvature of surfaces. The approach is reminiscent of the Gauss's contour based evaluation of intrinsic curvature. The presented formula may have a number of…

Numerical Analysis · Mathematics 2011-08-10 Pavel Grinfeld

It is common in Physiological Optics to fit the corneal and the lens surfaces to conic-based surfaces (usually ellipse-based surfaces), obtaining their characteristic radius of curvature and asphericity. Here we show that the variation in…

Medical Physics · Physics 2011-05-03 Alfonso Pérez-Escudero , Carlos Dorronsoro , Susana Marcos

Quantum observables can be identified with vector fields on the sphere of normalized states. Consequently, the uncertainty relations for quantum observables become geometric statements. In the Letter the familiar uncertainty relation…

Quantum Physics · Physics 2009-11-13 Alexey A. Kryukov

We introduce a visual motion segmentation method employing spherical geometry for fisheye cameras and automoated driving. Three commonly used geometric constraints in pin-hole imagery (the positive height, positive depth and epipolar…

Computer Vision and Pattern Recognition · Computer Science 2022-08-10 Letizia Mariotti , Ciaran Eising

The Cartesian coordinate system is the most commonly used system in computer visualization. This is due to its ease of use and processing speed. However, it is not always suitable for a given problem. Angular measures often allow us to…

Graphics · Computer Science 2023-06-08 Grzegorz Borowik , Michał Balicki , Michał Kasprzak , Piotr Cukier

The kinematical setting of spherically symmetric quantum geometry, derived from the full theory of loop quantum gravity, is developed. This extends previous studies of homogeneous models to inhomogeneous ones where interesting field theory…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Martin Bojowald

In this work, we study plane and spherical curves in Euclidean and Lorentz-Minkowski 3-spaces by employing rotation minimizing (RM) frames. By conveniently writing the curvature and torsion for a curve on a sphere, we show how to find the…

Differential Geometry · Mathematics 2022-09-22 Luiz C. B. da Silva

This paper presents a method for improved analysis of objects with an axial symmetry using X-ray Computed Tomography (CT). Cylindrical coordinates about an axis fixed to the object form the most natural base to check certain characteristics…

Image and Video Processing · Electrical Eng. & Systems 2020-10-06 Wannes Goethals , Marjolein Heyndrickx , Matthieu Boone

Measuring the similarity of curves is a fundamental problem arising in many application fields. There has been considerable interest in several such measures, both in Euclidean space and in more general setting such as curves on Riemannian…

Computational Geometry · Computer Science 2013-04-01 Erin Wolf Chambers , Yusu Wang

The basic arguments underlying the symplectic projector method are presented. By this method, local free coordinates on the constrait surface can be obtained for a broader class of constrained systems. Some interesting examples are…

High Energy Physics - Theory · Physics 2009-11-07 M. A. De Andrade , M. A. Santos , I. V. Vancea

Spherical field theory is a new non-perturbative method for studying quantum field theories. It uses the spherical partial wave expansion to reduce a general d-dimensional Euclidean field theory into a set of coupled one-dimensional…

High Energy Physics - Theory · Physics 2010-11-19 Dean Lee

Embedding diagrams prove to be quite useful when learning general relativity as they offer a way of visualizing spacetime curvature through warped two dimensional (2D) surfaces. In this manuscript we present a different 2D construct that…

General Relativity and Quantum Cosmology · Physics 2015-06-19 Chad A. Middleton

We begin by studying the surface area of an ellipsoid in n-dimensional Euclidean space as the function of the lengths of the semi-axes. We write down an explicit formula as an integral over the unit sphere in n-dimensions and use this…

Metric Geometry · Mathematics 2007-05-23 Igor Rivin

Consider an analytic map of a neighborhood of 0 in a vector space to a Euclidean space. Suppose that this map takes all germs of lines passing through 0 to germs of circles. Such a map is called rounding. We introduce a natural equivalence…

Metric Geometry · Mathematics 2007-05-23 Vladlen Timorin