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Lebesgue's Universal Covering Problem
Lebesgue's universal covering problem is an unsolved problem in geometry that asks for the convex shape of smallest area that can cover every planar set of diameter one. The diameter of a set by definition is the least upper bound of the distances between all pairs of points in the set. A shape covers a set if it contains a congruent subset. In other words the set may be rotated, translated or reflected to fit inside the shape. Formulation and early research The problem was posed by Henri Lebesgue in a letter to Gyula Pál in 1914. It was published in a paper by Pál in 1920 along with Pál's analysis. He showed that a cover for all curves of constant width one is also a cover for all sets of diameter one and that a cover can be constructed by taking a regular hexagon with an inscribed circle of diameter one and removing two corners from the hexagon to give a cover of area 2-\frac\approx 0.84529946. In 1936, Roland Sprague showed that a part of Pál's cover could be removed ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geometriae Dedicata
''Geometriae Dedicata'' is a mathematical journal, founded in 1972, concentrating on geometry and its relationship to topology, group theory and the theory of dynamical systems. It was created on the initiative of Hans Freudenthal in Utrecht, the Netherlands.. It is published by Springer Netherlands. The Editors-in-Chief An editor-in-chief (EIC), also known as lead editor or chief editor, is a publication's editorial leader who has final responsibility for its operations and policies. The highest-ranking editor of a publication may also be titled editor, managing ... are John R. Parker and Jean-Marc Schlenker.Journal website References External links Springer site Mathematics journals Springer Science+Business Media academic journals {{math-journal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blaschke Selection Theorem
The Blaschke selection theorem is a result in topology and convex geometry about sequences of convex sets. Specifically, given a sequence \ of convex sets contained in a bounded set, the theorem guarantees the existence of a subsequence \ and a convex set K such that K_ converges to K in the Hausdorff metric. The theorem is named for Wilhelm Blaschke. Alternate statements * A succinct statement of the theorem is that the metric space of convex bodies is locally compact. * Using the Hausdorff metric on sets, every infinite collection of compact subsets of the unit ball has a limit point (and that limit point is itself a compact set). Application As an example of its use, the isoperimetric problem can be shown to have a solution. That is, there exists a curve of fixed length that encloses the maximum area possible. Other problems likewise can be shown to have a solution: * Lebesgue's universal covering problem Lebesgue's universal covering problem is an unsolved problem in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kakeya Set
In mathematics, a Kakeya set, or Besicovitch set, is a set of points in Euclidean space which contains a unit line segment in every direction. For instance, a disk of radius 1/2 in the Euclidean plane, or a ball of radius 1/2 in three-dimensional space, forms a Kakeya set. Much of the research in this area has studied the problem of how small such sets can be. Besicovitch showed that there are Besicovitch sets of measure zero. A Kakeya needle set (sometimes also known as a Kakeya set) is a (Besicovitch) set in the plane with a stronger property, that a unit line segment can be rotated continuously through 180 degrees within it, returning to its original position with reversed orientation. Again, the disk of radius 1/2 is an example of a Kakeya needle set. Kakeya needle problem The Kakeya needle problem asks whether there is a minimum area of a region D in the plane, in which a needle of unit length can be turned through 360°. This question was first posed, for Convex set, convex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moving Sofa Problem
In mathematics, the moving sofa problem or sofa problem is a two-dimensional idealisation of real-life furniture-moving problems and asks for the rigid two-dimensional shape of largest area that can be maneuvered through an L-shaped planar region with legs of unit width. The area thus obtained is referred to as the ''sofa constant''. The exact value of the sofa constant is an open problem. The currently leading solution, by Joseph L. Gerver, has a value of approximately 2.2195 and is thought to be close to the optimal, based upon subsequent study and theoretical bounds. History The first formal publication was by the Austrian-Canadian mathematician Leo Moser in 1966, although there had been many informal mentions before that date. Bounds Work has been done on proving that the sofa constant (A) cannot be below or above certain values (lower bounds and upper bounds). Lower An obvious lower bound is A \geq \pi/2 \approx 1.57. This comes from a sofa that is a half-disk of unit ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moser's Worm Problem
Moser's worm problem (also known as mother worm's blanket problem) is an unsolved problem in geometry formulated by the Austrian-Canadian mathematician Leo Moser in 1966. The problem asks for the region of smallest area that can accommodate every plane curve of length 1. Here "accommodate" means that the curve may be rotated and translated to fit inside the region. In some variations of the problem, the region is restricted to be convex. Examples For example, a circular disk of radius 1/2 can accommodate any plane curve of length 1 by placing the midpoint of the curve at the center of the disk. Another possible solution has the shape of a rhombus with vertex angles of 60 and 120 degrees (/3 and 2/3 radians) and with a long diagonal of unit length. However, these are not optimal solutions; other shapes are known that solve the problem with smaller areas. Solution properties It is not completely trivial that a solution exists – an alternative possibility would be tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Journal Of Computational Geometry And Applications
The ''International Journal of Computational Geometry and Applications'' (IJCGA) is a bimonthly journal published since 1991, by World Scientific. It covers the application of computational geometry in design and analysis of algorithms, focusing on problems arising in various fields of science and engineering such as computer-aided geometry design (CAGD), operations research, and others. The current editors-in-chief are D.-T. Lee of the Institute of Information Science in Taiwan, and Joseph S. B. Mitchell from the Department of Applied Mathematics and Statistics in the State University of New York at Stony Brook. Abstracting and indexing * Current Contents/Engineering, Computing & Technology * ISI Alerting Services * Science Citation Index Expanded (also known as SciSearch) * CompuMath Citation Index * Mathematical Reviews * INSPEC * DBLP Bibliography Server * Zentralblatt MATH zbMATH Open, formerly Zentralblatt MATH, is a major reviewing service providing reviews and abst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quanta Magazine
''Quanta Magazine'' is an editorially independent online publication of the Simons Foundation covering developments in physics, mathematics, biology and computer science. ''Undark Magazine'' described ''Quanta Magazine'' as "highly regarded for its masterful coverage of complex topics in science and math." The science news aggregator ''RealClearScience'' ranked ''Quanta Magazine'' first on its list of "The Top 10 Websites for Science in 2018." In 2020, the magazine received a National Magazine Award for General Excellence from the American Society of Magazine Editors for its "willingness to tackle some of the toughest and most difficult topics in science and math in a language that is accessible to the lay reader without condescension or oversimplification." The articles in the magazine are freely available to read online. ''Scientific American'', ''Wired'', ''The Atlantic'', and ''The Washington Post'', as well as international science publications like ''Spektrum der Wissensch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of Computational Geometry
The ''Journal of Computational Geometry'' (JoCG) is an open access mathematics journal that was established in 2010. It covers research in all aspects of computational geometry. All its papers are published free of charge to both authors and readers, and are made freely available through a Creative Commons Attribution license. The current editors-in-chief are Kenneth L. Clarkson and Günter Rote. Along with its regularly contributed papers, the journal has since 2014 invited selected papers from the annual Symposium on Computational Geometry to a special issue. Abstracting and indexing The ''Journal of Computational Geometry'' is abstracted and indexed in MathSciNet, ''Zentralblatt Math'', and the Emerging Sources Citation Index. Long-term preservation of journal contents are ensured by the journal's membership in the Global LOCKSS Network. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roland Sprague
Roland Percival Sprague (11 July 1894, Unterliederbach – 1 August 1967) was a German mathematician, known for the Sprague–Grundy theorem and for being the first mathematician to find a perfect squared square. Biography With two mathematicians, Thomas Bond Sprague and Hermann Amandus Schwarz, as grandfathers, Roland Sprague was also a great-grandson of the mathematician Ernst Eduard Kummer and a great-grandson of the musical instrument maker Nathan Mendelssohn (1781–1852). After graduation (Abitur) in 1912 from the Bismarck-Gymnasium in Berlin-Wilmersdorf, Sprague studied from 1912 to 1919 in Berlin and Göttingen with an interruption by military service from 1915 to 1918. In 1921 in Berlin he passed the state test for teaching in mathematics, chemistry, and physics. He was Studienassessor (probationary teacher at a secondary school) from 1922 at the Paulsen-Realgymnasium in Berlin-Steglitz and from 1924 at the Schiller-Gymnasium (temporarily named "Clausewitz-Schule") i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geometry
Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is called a ''geometer''. Until the 19th century, geometry was almost exclusively devoted to Euclidean geometry, which includes the notions of point, line, plane, distance, angle, surface, and curve, as fundamental concepts. During the 19th century several discoveries enlarged dramatically the scope of geometry. One of the oldest such discoveries is Carl Friedrich Gauss' ("remarkable theorem") that asserts roughly that the Gaussian curvature of a surface is independent from any specific embedding in a Euclidean space. This implies that surfaces can be studied ''intrinsically'', that is, as stand-alone spaces, and has been expanded into the theory of manifolds and Riemannian geometry. Later in the 19th century, it appeared that geometries ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
