The Rise of Projective Geometry Euclid
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Projective Geometry: a Short Introduction
Projective Geometry: A Short Introduction Lecture Notes Edmond Boyer Master MOSIG Introduction to Projective Geometry Contents 1 Introduction 2 1.1 Objective . .2 1.2 Historical Background . .3 1.3 Bibliography . .4 2 Projective Spaces 5 2.1 Definitions . .5 2.2 Properties . .8 2.3 The hyperplane at infinity . 12 3 The projective line 13 3.1 Introduction . 13 3.2 Projective transformation of P1 ................... 14 3.3 The cross-ratio . 14 4 The projective plane 17 4.1 Points and lines . 17 4.2 Line at infinity . 18 4.3 Homographies . 19 4.4 Conics . 20 4.5 Affine transformations . 22 4.6 Euclidean transformations . 22 4.7 Particular transformations . 24 4.8 Transformation hierarchy . 25 Grenoble Universities 1 Master MOSIG Introduction to Projective Geometry Chapter 1 Introduction 1.1 Objective The objective of this course is to give basic notions and intuitions on projective geometry. The interest of projective geometry arises in several visual comput- ing domains, in particular computer vision modelling and computer graphics. It provides a mathematical formalism to describe the geometry of cameras and the associated transformations, hence enabling the design of computational ap- proaches that manipulates 2D projections of 3D objects. In that respect, a fundamental aspect is the fact that objects at infinity can be represented and manipulated with projective geometry and this in contrast to the Euclidean geometry. This allows perspective deformations to be represented as projective transformations. Figure 1.1: Example of perspective deformation or 2D projective transforma- tion. Another argument is that Euclidean geometry is sometimes difficult to use in algorithms, with particular cases arising from non-generic situations (e.g. -
The Trigonometry of Hyperbolic Tessellations
Canad. Math. Bull. Vol. 40 (2), 1997 pp. 158±168 THE TRIGONOMETRY OF HYPERBOLIC TESSELLATIONS H. S. M. COXETER ABSTRACT. For positive integers p and q with (p 2)(q 2) Ù 4thereis,inthe hyperbolic plane, a group [p, q] generated by re¯ections in the three sides of a triangle ABC with angles ôÛp, ôÛq, ôÛ2. Hyperbolic trigonometry shows that the side AC has length †,wherecosh†≥cÛs,c≥cos ôÛq, s ≥ sin ôÛp. For a conformal drawing inside the unit circle with centre A, we may take the sides AB and AC to run straight along radii while BC appears as an arc of a circle orthogonal to the unit circle.p The circle containing this arc is found to have radius 1Û sinh †≥sÛz,wherez≥ c2 s2, while its centre is at distance 1Û tanh †≥cÛzfrom A. In the hyperbolic triangle ABC,the altitude from AB to the right-angled vertex C is ê, where sinh ê≥z. 1. Non-Euclidean planes. The real projective plane becomes non-Euclidean when we introduce the concept of orthogonality by specializing one polarity so as to be able to declare two lines to be orthogonal when they are conjugate in this `absolute' polarity. The geometry is elliptic or hyperbolic according to the nature of the polarity. The points and lines of the elliptic plane ([11], x6.9) are conveniently represented, on a sphere of unit radius, by the pairs of antipodal points (or the diameters that join them) and the great circles (or the planes that contain them). The general right-angled triangle ABC, like such a triangle on the sphere, has ®ve `parts': its sides a, b, c and its acute angles A and B. -
Definitions and Nondefinability in Geometry 475 2
Definitions and Nondefinability in Geometry1 James T. Smith Abstract. Around 1900 some noted mathematicians published works developing geometry from its very beginning. They wanted to supplant approaches, based on Euclid’s, which han- dled some basic concepts awkwardly and imprecisely. They would introduce precision re- quired for generalization and application to new, delicate problems in higher mathematics. Their work was controversial: they departed from tradition, criticized standards of rigor, and addressed fundamental questions in philosophy. This paper follows the problem, Which geo- metric concepts are most elementary? It describes a false start, some successful solutions, and an argument that one of those is optimal. It’s about axioms, definitions, and definability, and emphasizes contributions of Mario Pieri (1860–1913) and Alfred Tarski (1901–1983). By fol- lowing this thread of ideas and personalities to the present, the author hopes to kindle interest in a fascinating research area and an exciting era in the history of mathematics. 1. INTRODUCTION. Around 1900 several noted mathematicians published major works on a subject familiar to us from school: developing geometry from the very beginning. They wanted to supplant the established approaches, which were based on Euclid’s, but which handled awkwardly and imprecisely some concepts that Euclid did not treat fully. They would present geometry with the precision required for general- ization and applications to new, delicate problems in higher mathematics—precision beyond the norm for most elementary classes. Work in this area was controversial: these mathematicians departed from tradition, criticized previous standards of rigor, and addressed fundamental questions in logic and philosophy of mathematics.2 After establishing background, this paper tells a story about research into the ques- tion, Which geometric concepts are most elementary? It describes a false start, some successful solutions, and a demonstration that one of those is in a sense optimal. -
Perspectives on Projective Geometry • Jürgen Richter-Gebert
Perspectives on Projective Geometry • Jürgen Richter-Gebert Perspectives on Projective Geometry A Guided Tour Through Real and Complex Geometry 123 Jürgen Richter-Gebert TU München Zentrum Mathematik (M10) LS Geometrie Boltzmannstr. 3 85748 Garching Germany [email protected] ISBN 978-3-642-17285-4 e-ISBN 978-3-642-17286-1 DOI 10.1007/978-3-642-17286-1 Springer Heidelberg Dordrecht London New York Library of Congress Control Number: 2011921702 Mathematics Subject Classification (2010): 51A05, 51A25, 51M05, 51M10 c Springer-Verlag Berlin Heidelberg 2011 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation,reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Cover design: deblik, Berlin Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) About This Book Let no one ignorant of geometry enter here! Entrance to Plato’s academy Once or twice she had peeped into the book her sister was reading, but it had no pictures or conversations in it, “and what is the use of a book,” thought Alice, “without pictures or conversations?” Lewis Carroll, Alice’s Adventures in Wonderland Geometry is the mathematical discipline that deals with the interrelations of objects in the plane, in space, or even in higher dimensions. -
Chapter 9 the Geometrical Calculus
Chapter 9 The Geometrical Calculus 1. At the beginning of the piece Erdmann entitled On the Universal Science or Philosophical Calculus, Leibniz, in the course of summing up his views on the importance of a good characteristic, indicates that algebra is not the true characteristic for geometry, and alludes to a “more profound analysis” that belongs to geometry alone, samples of which he claims to possess.1 What is this properly geometrical analysis, completely different from algebra? How can we represent geometrical facts directly, without the mediation of numbers? What, finally, are the samples of this new method that Leibniz has left us? The present chapter will attempt to answer these questions.2 An essay concerning this geometrical analysis is found attached to a letter to Huygens of 8 September 1679, which it accompanied. In this letter, Leibniz enumerates his various investigations of quadratures, the inverse method of tangents, the irrational roots of equations, and Diophantine arithmetical problems.3 He boasts of having perfected algebra with his discoveries—the principal of which was the infinitesimal calculus.4 He then adds: “But after all the progress I have made in these matters, I am no longer content with algebra, insofar as it gives neither the shortest nor the most elegant constructions in geometry. That is why... I think we still need another, properly geometrical linear analysis that will directly express for us situation, just as algebra expresses magnitude. I believe I have a method of doing this, and that we can represent figures and even 1 “Progress in the art of rational discovery depends for the most part on the completeness of the characteristic art. -
Archivio Istituzionale Open Access Dell'università Di Torino Original
AperTO - Archivio Istituzionale Open Access dell'Università di Torino From Emancipation to Persecution: Aspects and Moments of the Jewish Mathematical Milieu in Turin (1848-1938) This is the author's manuscript Original Citation: Availability: This version is available http://hdl.handle.net/2318/1677679 since 2019-01-02T09:39:53Z Published version: DOI:10.19272/201809201005 Terms of use: Open Access Anyone can freely access the full text of works made available as "Open Access". Works made available under a Creative Commons license can be used according to the terms and conditions of said license. Use of all other works requires consent of the right holder (author or publisher) if not exempted from copyright protection by the applicable law. (Article begins on next page) 28 September 2021 BOLLETTINO DI STORIA DELLE SCIENZE MATEMATICHE Anno XXXVIII · Numero 1 · Giugno 2018 PISA · ROMA FABRIZIO SERRA EDITORE MMXVIII Autorizzazione del Tribunale di Pisa n. 13 del 17.07.2001. Direttore responsabile: Lucia Corsi * Amministrazione e abbonamenti Fabrizio Serra editore® Casella postale n. 1, succursale n. 8, I 56123 Pisa Uffici di Pisa: Via Santa Bibbiana 28, I 56127 Pisa, tel. +39 050542332, fax +39 050574888, [email protected] Uffici di Roma: Via Carlo Emanuele I, I 00185 Roma, tel. +39 0670493456, fax +39 0670476605, [email protected] I prezzi ufficiali di abbonamento cartaceo e Online sono consultabili presso il sito Internet della casa editrice www.libraweb.net. Print and Online official subscription rates are available at Publisher’s website www.libraweb.net. I pagamenti possono essere effettuati tramite versamento su c.c.p. -
PROJECTIVE GEOMETRY Contents 1. Basic Definitions 1 2. Axioms Of
PROJECTIVE GEOMETRY KRISTIN DEAN Abstract. This paper investigates the nature of finite geometries. It will focus on the finite geometries known as projective planes and conclude with the example of the Fano plane. Contents 1. Basic Definitions 1 2. Axioms of Projective Geometry 2 3. Linear Algebra with Geometries 3 4. Quotient Geometries 4 5. Finite Projective Spaces 5 6. The Fano Plane 7 References 8 1. Basic Definitions First, we must begin with a few basic definitions relating to geometries. A geometry can be thought of as a set of objects and a relation on those elements. Definition 1.1. A geometry is denoted G = (Ω,I), where Ω is a set and I a relation which is both symmetric and reflexive. The relation on a geometry is called an incidence relation. For example, consider the tradional Euclidean geometry. In this geometry, the objects of the set Ω are points and lines. A point is incident to a line if it lies on that line, and two lines are incident if they have all points in common - only when they are the same line. There is often this same natural division of the elements of Ω into different kinds such as the points and lines. Definition 1.2. Suppose G = (Ω,I) is a geometry. Then a flag of G is a set of elements of Ω which are mutually incident. If there is no element outside of the flag, F, which can be added and also be a flag, then F is called maximal. Definition 1.3. A geometry G = (Ω,I) has rank r if it can be partitioned into sets Ω1,..., Ωr such that every maximal flag contains exactly one element of each set. -
Euclidean Versus Projective Geometry
Projective Geometry Projective Geometry Euclidean versus Projective Geometry n Euclidean geometry describes shapes “as they are” – Properties of objects that are unchanged by rigid motions » Lengths » Angles » Parallelism n Projective geometry describes objects “as they appear” – Lengths, angles, parallelism become “distorted” when we look at objects – Mathematical model for how images of the 3D world are formed. Projective Geometry Overview n Tools of algebraic geometry n Informal description of projective geometry in a plane n Descriptions of lines and points n Points at infinity and line at infinity n Projective transformations, projectivity matrix n Example of application n Special projectivities: affine transforms, similarities, Euclidean transforms n Cross-ratio invariance for points, lines, planes Projective Geometry Tools of Algebraic Geometry 1 n Plane passing through origin and perpendicular to vector n = (a,b,c) is locus of points x = ( x 1 , x 2 , x 3 ) such that n · x = 0 => a x1 + b x2 + c x3 = 0 n Plane through origin is completely defined by (a,b,c) x3 x = (x1, x2 , x3 ) x2 O x1 n = (a,b,c) Projective Geometry Tools of Algebraic Geometry 2 n A vector parallel to intersection of 2 planes ( a , b , c ) and (a',b',c') is obtained by cross-product (a'',b'',c'') = (a,b,c)´(a',b',c') (a'',b'',c'') O (a,b,c) (a',b',c') Projective Geometry Tools of Algebraic Geometry 3 n Plane passing through two points x and x’ is defined by (a,b,c) = x´ x' x = (x1, x2 , x3 ) x'= (x1 ', x2 ', x3 ') O (a,b,c) Projective Geometry Projective Geometry -
Research Article Traditional Houses and Projective Geometry: Building Numbers and Projective Coordinates
Hindawi Journal of Applied Mathematics Volume 2021, Article ID 9928900, 25 pages https://doi.org/10.1155/2021/9928900 Research Article Traditional Houses and Projective Geometry: Building Numbers and Projective Coordinates Wen-Haw Chen 1 and Ja’faruddin 1,2 1Department of Applied Mathematics, Tunghai University, Taichung 407224, Taiwan 2Department of Mathematics, Universitas Negeri Makassar, Makassar 90221, Indonesia Correspondence should be addressed to Ja’faruddin; [email protected] Received 6 March 2021; Accepted 27 July 2021; Published 1 September 2021 Academic Editor: Md Sazzad Hossien Chowdhury Copyright © 2021 Wen-Haw Chen and Ja’faruddin. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The natural mathematical abilities of humans have advanced civilizations. These abilities have been demonstrated in cultural heritage, especially traditional houses, which display evidence of an intuitive mathematics ability. Tribes around the world have built traditional houses with unique styles. The present study involved the collection of data from documentation, observation, and interview. The observations of several traditional buildings in Indonesia were based on camera images, aerial camera images, and documentation techniques. We first analyzed the images of some sample of the traditional houses in Indonesia using projective geometry and simple house theory and then formulated the definitions of building numbers and projective coordinates. The sample of the traditional houses is divided into two categories which are stilt houses and nonstilt house. The present article presents 7 types of simple houses, 21 building numbers, and 9 projective coordinates. -
TOWARDS a HISTORY of the GEOMETRIC FOUNDATIONS of MATHEMATICS LATE Xixth CENTURY*
ARTICLES TOWARDS A HISTORY OF THE GEOMETRIC FOUNDATIONS OF MATHEMATICS LATE XIXth CENTURY* Rossana TAZZIOLI RÉSUMÉ : Beaucoup de « géomètres » du XIXe siècle – Bernhard Riemann, Hermann von Helmholtz, Felix Klein, Riccardo De Paolis, Mario Pieri, Henri Poincaré, Federigo Enriques, et autres – ont joué un rôle important dans la discussion sur les fondements des mathématiques. Mais, contrairement aux idées d’Euclide, ils n’ont pas identifié « l’espace physique » avec « l’espace de nos sens ». Partant de notre expérience dans l’espace, ils ont cherché à identifier les propriétés les plus importantes de l’espace et les ont posées à la base de la géométrie. C’est sur la connaissance active de l’espace que les axiomes de la géométrie ont été élaborés ; ils ne pouvaient donc pas être a priori comme ils le sont dans la philosophie kantienne. En outre, pendant la dernière décade du siècle, certains mathématiciens italiens – De Paolis, Gino Fano, Pieri, et autres – ont fondé le concept de nombre sur la géométrie, en employant des résultats de la géométrie projective. Ainsi, on fondait l’arithmétique sur la géométrie et non l’inverse, comme David Hilbert a cherché à faire quelques années après, sans succès. MOTS-CLÉS : Riemann, Helmholtz, fondements des mathématiques, géométrie, espace. ABSTRACT : Many XIXth century « geometers » – such as Bernhard Riemann, Hermann von Helmholtz, Felix Klein, Riccardo De Paolis, Mario Pieri, Henri Poincaré, Federigo Enriques, and others – played an important role in the discussion about the founda- tions of mathematics. But in contrast to Euclid’s ideas, they did not simply identify « physical space » with the « space of the senses ». -
Notices of the American Mathematical Society ABCD Springer.Com
ISSN 0002-9920 Notices of the American Mathematical Society ABCD springer.com Highlights in Springer’s eBook Collection of the American Mathematical Society August 2009 Volume 56, Number 7 Guido Castelnuovo and Francesco Severi: NEW NEW NEW Two Personalities, Two The objective of this textbook is the Blackjack is among the most popular This second edition of Alexander Soifer’s Letters construction, analysis, and interpreta- casino table games, one where astute How Does One Cut a Triangle? tion of mathematical models to help us choices of playing strategy can create demonstrates how different areas of page 800 understand the world we live in. an advantage for the player. Risk and mathematics can be juxtaposed in the Students and researchers interested in Reward analyzes the game in depth, solution of a given problem. The author mathematical modelling in math- pinpointing not just its optimal employs geometry, algebra, trigono- ematics, physics, engineering and the strategies but also its financial metry, linear algebra, and rings to The Dixmier–Douady applied sciences will find this text useful. performance, in terms of both expected develop a miniature model of cash flow and associated risk. mathematical research. Invariant for Dummies 2009. Approx. 480 p. (Texts in Applied Mathematics, Vol. 56) Hardcover 2009. Approx. 140 p. 23 illus. Hardcover 2nd ed. 2009. XXX, 174 p. 80 illus. Softcover page 809 ISBN 978-0-387-87749-5 7 $69.95 ISBN 978-1-4419-0252-8 7 $49.95 ISBN 978-0-387-74650-0 7 approx. $24.95 For access check with your librarian Waco Meeting page 879 A Primer on Scientific Data Mining in Agriculture Explorations in Monte Programming with Python A. -
The Diffusion of Sophus Lie's Theory of Continuous Transformation Groups In
The diffusion of Sophus Lie’s theory of continuous transformation groups in Italy The role of Corrado Segre and his followers Maria Anna RASPANTI Università di Torino Trento 2014 ABSTRACT The aim of this report is to analyze the influence of the dissemination of Sophus Lie’s (1842-1899) theory of continuous transformation groups on the development of Italian mathematics, in particular in the field of algebraic geometry, thanks to Corrado Segre’s (1863-1924) scientific, didactic and promoting activity. Segre’s interest in the theory of Lie groups and in its applications (especially to geometry as a consequence of Felix Klein’s Erlangen Program) emerges from some of his notebooks (conserved in the Biblioteca Matematica “Giuseppe Peano” of the University of Turin), among which one can find the “Quaderno 11”, concerning the course in Higher Geometry he held in the 1897-1898 academic year, entitled “Lezioni sui gruppi continui di trasformazioni” (lessons in continuous groups of transformation). Among the students who attended the classes there were Grace Chisholm and William Young, whose notes (Archives – University of Liverpool) have been used for a comparison of the contents. Italian geometers (in particular, those close to Corrado Segre’s School), played an important role in the connection between the theory of Lie groups and geometry; an evidence of this can be found in some writings of Federigo Enriques (1871- 1946) and Gino Fano (1871-1952). Theory of continuous transformation groups and its connections with the developments of geometry in the sense of Erlangen Program Analysis of Corrado Segre’s notebook for his course of Higher Geometry of 1897-1898 Diffusion of Sophus Lie's theory and role of Corrado Segre’s School Unpublished documents and correspondence Fondo Segre, Biblioteca Matematica G.