Manifolds | Projective geometry
In geometry, a real projective line is a projective line over the real numbers. It is an extension of the usual concept of a line that has been historically introduced to solve a problem set by visual perspective: two parallel lines do not intersect but seem to intersect "at infinity". For solving this problem, points at infinity have been introduced, in such a way that in a real projective plane, two distinct projective lines meet in exactly one point. The set of these points at infinity, the "horizon" of the visual perspective in the plane, is a real projective line. It is the set of directions emanating from an observer situated at any point, with opposite directions identified. An example of a real projective line is the projectively extended real line, which is often called the projective line. Formally, a real projective line P(R) is defined as the set of all one-dimensional linear subspaces of a two-dimensional vector space over the reals. The automorphisms of a real projective line are called projective transformations, homographies, or linear fractional transformations. They form the projective linear group PGL(2, R). Each element of PGL(2, R) can be defined by a nonsingular 2×2 real matrix, and two matrices define the same element of PGL(2, R) if one is the product of the other and a nonzero real number. Topologically, real projective lines are homeomorphic to circles. The complex analog of a real projective line is a complex projective line; that is, a Riemann sphere. (Wikipedia).
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
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
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
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
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
Duality: magic in simple geometry #SoME2
Two inaccuracies: 2:33 explains the first property (2:16), not the second one (2:24) Narration at 5:52 should be "intersections of GREEN and orange lines" Time stamps: 0:00 — Intro 0:47 — Polar transform 4:46 — Desargues's Theorem 6:29 — Pappus's Theorem 7:18 — Sylvester-Gallai Theorem 8
From playlist Summer of Math Exposition 2 videos
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
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
The rational number line and irrationalities (b) | Famous Math Problems 19b | NJ Wildberger
In this video we present a basic and profound solution to the most important and fundamental problem in mathematics (which is: How to model the continuum?) This is the rational number line. Our presentation is geometric, assuming a prior theory of affine geometry: this balances the far mor
From playlist Famous Math Problems
Visualizing quaternions (4d numbers) with stereographic projection
How to think about this 4d number system in our 3d space. Part 2: https://youtu.be/zjMuIxRvygQ Interactive version of these visuals: https://eater.net/quaternions Help fund future projects: https://www.patreon.com/3blue1brown An equally valuable form of support is to simply share some of t
From playlist Explainers
Euler's formula and extracting power and phase
Extracting time-frequency information from the result of complex Morlet wavelet convolution involves reinterpreting Euler's formula (eik), which allows you to extract three important pieces of information from the result of complex Morlet wavelet convolution (power, phase, and the band-pas
From playlist OLD ANTS #3) Time-frequency analysis via Morlet wavelet convolution
Discrete groups in complex hyperbolic geometry (Lecture - 01) by Pierre Will
Geometry, Groups and Dynamics (GGD) - 2017 DATE: 06 November 2017 to 24 November 2017 VENUE: Ramanujan Lecture Hall, ICTS, Bengaluru The program focuses on geometry, dynamical systems and group actions. Topics are chosen to cover the modern aspects of these areas in which research has b
From playlist Geometry, Groups and Dynamics (GGD) - 2017
Complex sine waves and interpreting Fourier coefficients
Now that you know the basic mechanics underlying the Fourier transform, it's time to learn about complex numbers, complex sine waves, and how to extract power and phase information from a complex dot product. Don't worry, it's actually not so complex! The video uses files you can download
From playlist OLD ANTS #2) The discrete-time Fourier transform
What is a Manifold? Lesson 14: Quotient Spaces
I AM GOING TO REDO THIS VIDEO. I have made some annotations here and annotations are not visible on mobile devices. STAY TUNED. This is a long lesson about an important topological concept: quotient spaces.
From playlist What is a Manifold?
Perspectives in Math and Art by Supurna Sinha
KAAPI WITH KURIOSITY PERSPECTIVES IN MATH AND ART SPEAKER: Supurna Sinha (Raman Research Institute, Bengaluru) WHEN: 4:00 pm to 5:30 pm Sunday, 24 April 2022 WHERE: Jawaharlal Nehru Planetarium, Bengaluru Abstract: The European renaissance saw the merging of mathematics and art in th
From playlist Kaapi With Kuriosity (A Monthly Public Lecture Series)
Seminar on Applied Geometry and Algebra (SIAM SAGA): Dustin Mixon
Title: Packing Points in Projective Spaces Speaker: Dustin Mixon Date: Tuesday, March 8, 2022 at 11:00am Eastern Abstract: Given a compact metric space, it is natural to ask how to arrange a given number of points so that the minimum distance is maximized. For example, the setting of the
From playlist Seminar on Applied Geometry and Algebra (SIAM SAGA)
Algebraic and Convex Geometry of Sums of Squares on Varieties (Lecture 3) by Greg Blekherman
PROGRAM COMBINATORIAL ALGEBRAIC GEOMETRY: TROPICAL AND REAL (HYBRID) ORGANIZERS Arvind Ayyer (IISc, India), Madhusudan Manjunath (IITB, India) and Pranav Pandit (ICTS-TIFR, India) DATE: 27 June 2022 to 08 July 2022 VENUE: Madhava Lecture Hall and Online Algebraic geometry is the study of
From playlist Combinatorial Algebraic Geometry: Tropical and Real (HYBRID)
What is a Manifold? Lesson 12: Fiber Bundles - Formal Description
This is a long lesson, but it is not full of rigorous proofs, it is just a formal definition. Please let me know where the exposition is unclear. I din't quite get through the idea of the structure group of a fiber bundle fully, but I introduced it. The examples in the next lesson will h
From playlist What is a Manifold?
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