Real analysis | Infinity | Topological spaces | Projective geometry

Projectively extended real line

In real analysis, the projectively extended real line (also called the one-point compactification of the real line), is the extension of the set of the real numbers, by a point denoted ∞. It is thus the set with the standard arithmetic operations extended where possible, and is sometimes denoted by The added point is called the point at infinity, because it is considered as a neighbour of both ends of the real line. More precisely, the point at infinity is the limit of every sequence of real numbers whose absolute values are increasing and unbounded. The projectively extended real line may be identified with a real projective line in which three points have been assigned the specific values 0, 1 and ∞. The projectively extended real number line is distinct from the affinely extended real number line, in which +∞ and −∞ are distinct. (Wikipedia).

Projectively extended real line
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Introduction to Projective Geometry (Part 1)

The first video in a series on projective geometry. We discuss the motivation for studying projective planes, and list the axioms of affine planes.

From playlist Introduction to Projective Geometry

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Projective Coordinates for Points and Lines | Algebraic Calculus One | Wild Egg and Anna Tomskova

Dr Anna Tomskova explains a more modern framework for projective geometry where the extra coordinate often associated with infinity is the first coordinate in a projective vector. This gives us a uniform way to associate to affine points and lines projective points and lines, with the adva

From playlist Algebraic Calculus One

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The extended rational numbers in practice | Real numbers and limits Math Foundations 105

We review the extended rational numbers, which extend the rational numbers to all expressions of the form a/b, where a and b are integers---even b=0. Then we give some examples of how these strange beasts might prove useful in mathematics. But first we give one example of where they are un

From playlist Math Foundations

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algebraic geometry 15 Projective space

This lecture is part of an online algebraic geometry course, based on chapter I of "Algebraic geometry" by Hartshorne. It introduces projective space and describes the synthetic and analytic approaches to projective geometry

From playlist Algebraic geometry I: Varieties

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Extending arithmetic to infinity! | Real numbers and limits Math Foundations 103 | N J Wildberger

We are interested in investigating how to rigorously and carefully extend arithmetic with rational numbers to a wider domain involving the symbol 1/0, represented by a ``sideways 8''. First we have a look at the simpler case of natural number arithmetic, where extending to infinity is re

From playlist Math Foundations

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Introduction to Projective Geometry (Part 2)

The second video in a series about projective geometry. We list the axioms for projective planes, give an examle of a projective plane with finitely many points, and define the real projective plane.

From playlist Introduction to Projective Geometry

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Elliptic curves: point at infinity in the projective plane

This video depicts point addition and doubling on elliptic curve in simple Weierstrass form in the projective plane depicted using stereographic projection where the point at infinity can actually be seen. Explanation is in the accompanying article https://trustica.cz/2018/04/05/elliptic-

From playlist Elliptic Curves - Number Theory and Applications

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The circle and projective homogeneous coordinates | Universal Hyperbolic Geometry 7a | NJ Wildberger

Universal hyperbolic geometry is based on projective geometry. This video introduces this important subject, which these days is sadly absent from most undergrad/college curriculums. We adopt the 19th century view of a projective space as the space of one-dimensional subspaces of an affine

From playlist Universal Hyperbolic Geometry

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The circle and projective homogeneous coordinates (cont.) | Universal Hyperbolic Geometry 7b

Universal hyperbolic geometry is based on projective geometry. This video introduces this important subject, which these days is sadly absent from most undergrad/college curriculums. We adopt the 19th century view of a projective space as the space of one-dimensional subspaces of an affine

From playlist Universal Hyperbolic Geometry

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Tropical Geometry - Lecture 11 - Toric Varieties | Bernd Sturmfels

Twelve lectures on Tropical Geometry by Bernd Sturmfels (Max Planck Institute for Mathematics in the Sciences | Leipzig, Germany) We recommend supplementing these lectures by reading the book "Introduction to Tropical Geometry" (Maclagan, Sturmfels - 2015 - American Mathematical Society)

From playlist Twelve Lectures on Tropical Geometry by Bernd Sturmfels

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From playlist Stanford Seminars

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Schemes 25: Proper morphisms and valuations

This lecture is part of an online algebraic geometry course on schemes, based on chapter II of "Algebraic geometry" by Hartshorne. We describe how to test a morphism for being proper using discrete valuation rings, and use this to show that projective morphisms are proper.

From playlist Algebraic geometry II: Schemes

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Schemes 23: Valuations and separation

This lecture is part of an online algebraic geometry course on schemes, based on chapter II of "Algebraic geometry" by Hartshorne.. We state a condition for morphisms of schemes to be separated in therms of discrete valuation rings, and apply this to the line with two origins and the proje

From playlist Algebraic geometry II: Schemes

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p-Adic Analytic Continuation of Genus 2 Overconvergent... - Yichao Tian

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From playlist Mathematics

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Totally nonparallel immersions - Michael Harrison

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From playlist Mathematics

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From playlist 🔥Java Tutorial For Beginners | Java Full Course | Java Interview Questions And Answers | Java Programming | Updated Java Playlist 2023 | Simplilearn

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A brief history of Geometry III: The 19th century | Sociology and Pure Mathematics | N J Wildberger

The 19th century was a pivotal time in the development of modern geometry, actually a golden age for the subject, which then saw a precipitous decline in the 20th century. Why was that? To find out, let's first overview some of the main developments in geometry during the 1800's, includin

From playlist Sociology and Pure Mathematics

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Beyond geometric invariant theory 2: Good moduli spaces, and applications by Daniel Halpern-Leistner

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From playlist Moduli Of Bundles And Related Structures 2020

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J-B Bost - Theta series, infinite rank Hermitian vector bundles, Diophantine algebraization (Part2)

In the classical analogy between number fields and function fields, an Euclidean lattice (E,∥.∥) may be seen as the counterpart of a vector bundle V on a smooth projective curve C over some field k. Then the arithmetic counterpart of the dimension h0(C,V)=dimkΓ(C,V) of the space of section

From playlist Ecole d'été 2017 - Géométrie d'Arakelov et applications diophantiennes

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Algebraic structure on the Euclidean projective line | Rational Geometry Math Foundations 137

In this video we look at some pleasant consequences of imposing a Euclidean structure on the projective line. We give a proof of the fundamental projective Triple quad formula, talk about the equal p-quadrances theorem, and see how the logistic map of chaos theory makes its appearance as t

From playlist Math Foundations

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