Systems of set theory

Semiset

In set theory, a semiset is a proper class that is a subclass of a set.The theory of semisets was proposed and developed by Czech mathematicians Petr Vopěnka and Petr Hájek (1972). It is based on a modification of the von Neumann–Bernays–Gödel set theory; in standard NBG, the existence of semisets is precluded by the axiom of separation. The concept of semisets opens the way for a formulation of an alternative set theory.In particular, Vopěnka's Alternative Set Theory (1979) axiomatizes the concept of semiset, supplemented with several additional principles. Semisets can be used to represent sets with imprecise boundaries. Novák (1984) studied approximation of semisets by fuzzy sets, which are often more suitable for practical applications of the modeling of imprecision. (Wikipedia).

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(ML 19.5) Positive semidefinite kernels (Covariance functions)

Definition of a positive semidefinite kernel, or covariance function. A simple example. Explanation of terminology: autocovariance, positive definite kernel, stationary kernel, isotropic kernel, covariogram, positive definite function.

From playlist Machine Learning

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What are Supersets? | Set Theory, Subsets, Set Relations

What are supersets? We'll be going over the definition and examples of supersets in today's video set theory lesson! If B is a subset of A then A is a superset of B. The superset relation is the same as the subset relation but in the opposite direction! Remember if every element of B is

From playlist Set Theory

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Inner & Outer Semidirect Products Derivation - Group Theory

Semidirect products are a very important tool for studying groups because they allow us to break a group into smaller components using normal subgroups and complements! Here we describe a derivation for the idea of semidirect products and an explanation of how the map into the automorphism

From playlist Group Theory

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Semirings that are finite and have infinity

Semirings. You can find the simple python script here: https://gist.github.com/Nikolaj-K/f036fd07991fce26274b5b6f15a6c032 Previous video: https://youtu.be/ws6vCT7ExTY

From playlist Algebra

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Orders on Sets: Part 1 - Partial Orders

This was recorded as supplemental material for Math 115AH at UCLA in the spring quarter of 2020. In this video, I discuss the concept and definition of a partial order.

From playlist Orders on Sets

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Normal subgroups

Before we carry on with our coset journey, we need to discover when the left- and right cosets are equal to each other. The obvious situation is when our group is Abelian. The other situation is when the subgroup is a normal subgroup. In this video I show you what a normal subgroup is a

From playlist Abstract algebra

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An incredible semicircle problem!

A semicircle contains an inscribed semicircle dividing its diameter into two lengths a and b. Can you find the formula for the inscribed semicircle's diameter in terms of the lengths a and b? What is the locus of the center of the inscribed semicircle? Thanks to Nick from Greece for the su

From playlist Math Puzzles, Riddles And Brain Teasers

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Goemans-Williamson Max-Cut Algorithm | The Practical Guide to Semidefinite Programming (4/4)

Fourth and last video of the Semidefinite Programming series. In this video, we will go over Goemans and Williamson's algorithm for the Max-Cut problem. Their algorithm, which is still state-of-the-art today, is one of the biggest breakthroughs in approximation theory. Remarkably, it is

From playlist Semidefinite Programming

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What is Set Subtraction?

What is set subtraction? In this video we go over that, the set minus set operation, and an example of subtraction in set theory. This is a handy concept to grasp to understand the complement of a set and universal sets, which I also have videos on. Links below. I hope you find this vide

From playlist Set Theory

Related pages

Fuzzy Sets and Systems | Set theory | Class (set theory) | Fuzzy set | Subclass (set theory) | Set (mathematics) | Alternative set theory | Von Neumann–Bernays–Gödel set theory