This is the first post in a series. This started as an investigation of various non-standard axiomatizations of common structures, but soon the posts ended up focusing on a particular such kind of axiomatization. Thus, this title is misleading (and anyway, it seems too broad for a single series.)
Category: Math
Facts About Field Extensions
This is a list of definitions and theorems concerning field extensions, that I’m compiling for my learning. Throughout, let be a field.
On Renaming Universal Algebra
Especially in comparatively recent times, researchers in the subject of universal algebra have sought to replace that name, leading people to choose an alternative term instead. In this post, I discuss my thoughts on this matter.
Algebraic Structures Applicable to All Sets
This exploration is inspired by the fact that, given the Axiom of Choice, any set can be given a group structure. (Fine print: throughout the rest of this post, we assume all sets are nonempty.) In fact, these two statements are equivalent. Questions about similar statements have popped up in other contexts; for example, in Topology as an Algebraic Structure, the question arises as to whether any infinite set can be given a field structure. (Clearly, not every finite set can be given a field structure, since we have the classification of finite fields.)
Construction of the Reals from Decimals
In typical real analysis classes, the presentation of real numbers that is generally given in schools (starting from rationals) is considered insufficiently rigorous, and replaced by a construction involving Dedekind cuts. However, in this post, we investigate a formalization that derives directly from the presentation given in schools — specifically, using decimals — and study its equivalence to the Dedekind cut formulation.
Characteristic of a Monoid
In ring theory, the characteristic is defined as the min such that
, or 0 if no such
exists; judging from https://en.wikipedia.org/wiki/Characteristic_(algebra), it seems that no concept of characteristic has been considered for structures more general than rings. Here, we generalize the concept to any monoid
.
Archimedes and the Area of a Circle
In this post, we claim that the method of exhaustion developed by Archimedes to calculate the area of a circle is in fact sufficiently rigorous.
Sine Angle Addition Functional Equation 2
In this post, we continue the discussion from this post, where we investigate the sine angle addition functional equation
Normal Subset of a Group
We attempt to generalize the notion of “normal subgroup,” used in studying kernels and homomorphisms, to a “normal subset” that does not have the requirement of being a subgroup, and we see whether it is possible for a normal subset to exist that is not a normal subgroup.
On the Philosophical Foundations of ZFC
In this post, we discuss some questions concerning the philosophical foundations of ZFC.
