Theorems in computational complexity theory | Descriptive complexity

Fagin's theorem

Fagin's theorem is the oldest result of descriptive complexity theory, a branch of computational complexity theory that characterizes complexity classes in terms of logic-based descriptions of their problems rather than by the behavior of algorithms for solving those problems.The theorem states that the set of all properties expressible in existential second-order logic is precisely the complexity class NP. It was proven by Ronald Fagin in 1973 in his doctoral thesis, and appears in his 1974 paper. The arity required by the second-order formula was improved (in one direction) in , and several results of have provided tighter bounds on nondeterministic random-access machines. (Wikipedia).

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Theory of numbers: Congruences: Euler's theorem

This lecture is part of an online undergraduate course on the theory of numbers. We prove Euler's theorem, a generalization of Fermat's theorem to non-prime moduli, by using Lagrange's theorem and group theory. As an application of Fermat's theorem we show there are infinitely many prim

From playlist Theory of numbers

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Theory of numbers: Gauss's lemma

This lecture is part of an online undergraduate course on the theory of numbers. We describe Gauss's lemma which gives a useful criterion for whether a number n is a quadratic residue of a prime p. We work it out explicitly for n = -1, 2 and 3, and as an application prove some cases of Di

From playlist Theory of numbers

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Introduction to additive combinatorics lecture 10.8 --- A weak form of Freiman's theorem

In this short video I explain how the proof of Freiman's theorem for subsets of Z differs from the proof given earlier for subsets of F_p^N. The answer is not very much: the main differences are due to the fact that cyclic groups of prime order do not have lots of subgroups, so one has to

From playlist Introduction to Additive Combinatorics (Cambridge Part III course)

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Theory of numbers: Fermat's theorem

This lecture is part of an online undergraduate course on the theory of numbers. We prove Fermat's theorem a^p = a mod p. We then define the order of a number mod p and use Fermat's theorem to show the order of a divides p-1. We apply this to testing some Fermat and Mersenne numbers to se

From playlist Theory of numbers

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Mikhail Lyubich: Story of the Feigenbaum point

HYBRID EVENT Recorded during the meeting "Advancing Bridges in Complex Dynamics" the September 23, 2021 by the Centre International de Rencontres Mathématiques (Marseille, France) Filmmaker: Luca Récanzone Find this video and other talks given by worldwide mathematicians on CIRM's Audi

From playlist Dynamical Systems and Ordinary Differential Equations

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Number Theorem | Gauss' Theorem

We prove Gauss's Theorem. That is, we prove that the sum of values of the Euler phi function over divisors of n is equal to n. http://www.michael-penn.net http://www.randolphcollege.edu/mathematics/

From playlist Number Theory

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The Drinfeld-Sokolov reduction of admissible representations of affine Lie algebras - Gurbir Dhillon

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From playlist Mathematics

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Stanford Seminar - Applying Theory to Practice (and Practice to Theory)

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From playlist Statistics and Data Science

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Fermat's Last Theorem for rational and irrational exponents

Fermat's Last Theorem states the equation x^n + y^n = z^n has no integer solutions for positive integer exponents greater than 2. However, Fermat's Last Theorem says nothing about exponents that are not positive integers. Note: x, y and z are meant to be positive integers, which I should

From playlist My Maths Videos

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Theory of numbers: Multiplicative functions

This lecture is part of an online undergraduate course on the theory of numbers. Multiplicative functions are functions such that f(mn)=f(m)f(n) whenever m and n are coprime. We discuss some examples, such as the number of divisors, the sum of the divisors, and Euler's totient function.

From playlist Theory of numbers

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Cascadia Ruby Conf 2012 A Taste of Prolog by Aja Hammerly

Help us caption & translate this video! http://amara.org/v/FGiV/

From playlist Cascadia Ruby 2012

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Bayes, Medical Diagnostics, and Nomograms

(April 11, 2012) Joe Marasco shares his beliefs on how modern diagnostics and medical testing can be changed to give patients a clearer understanding of the results. He suggests implementing a new protocol using Bayes theorem and certain medical technologies to help explain testing results

From playlist Engineering

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Proof & Explanation: Gauss's Lemma in Number Theory

Euler's criterion: https://youtu.be/2IBPOI43jek One common proof of quadratic reciprocity uses Gauss's lemma. To understand Gauss's lemma, here we prove how it works using Euler's criterion and the Legendre symbol. Quadratic Residues playlist: https://www.youtube.com/playlist?list=PLug5Z

From playlist Quadratic Residues

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Nicole Schweikardt: Databases and descriptive complexity – lecture 1

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From playlist Numerical Analysis and Scientific Computing

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Knot Categorification From Mirror Symmetry (Lecture- 2) by Mina Aganagic

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From playlist Quantum Fields, Geometry and Representation Theory 2021 (ONLINE)

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Number Theory | A very special case of Fermat's Last Theorem

We prove a very simple case of Fermat's Last Theorem. Interestingly, this case is fairly easy to prove which highlights the allure of the theorem as a whole -- especially given the fact that much of modern number theory was developed as part of the program that ended in the full proof. ht

From playlist Number Theory

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Character Tables for S5 and A5

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From playlist Representation Theory

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Ilya Dumanski - Schubert varieties in the Beilinson-Drinfeld Grassmannian

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From playlist Azat Miftakhov Days Against the War

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Convolution Theorem: Fourier Transforms

Free ebook https://bookboon.com/en/partial-differential-equations-ebook Statement and proof of the convolution theorem for Fourier transforms. Such ideas are very important in the solution of partial differential equations.

From playlist Partial differential equations

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Spectrum of a sentence | Computational complexity theory | Second-order logic | First-order logic | Arity