Categories
Math

Sine Angle Product Formula 3

In this post, we continue the discussion from a previous post about the existence of a suitable sine angle product identity.

Categories
Math

Starting Intro to Abstract Algebra

I’ve started writing a textbook for Intro to Abstract Algebra! You can check it out here (in-progress, published incrementally).

Categories
Math

Generalization of the Group Ring to Other Algebraic Structures

It seems natural to try to generalize the group ring construction to algebraic structures other than groups and rings. We do so here.

Categories
Math

Removing Proper Classes via Universal Sets

Can we avoid ever needing to mention proper classes in math by restricting to subsets of a universal working set?

Categories
Math

Subsets of Algebras, Subalgebras, and Preserving Concepts

Let F be a field and S \subseteq F be closed under addition and multiplication; under these operations, say S is a field. Is it then necessarily true that the other field concepts on S (identities and inverse) agree with those on F? What about for other algebras?

Categories
Math

Rings as Modules Over Themselves

In this note, we address some questions I had concerning rings when viewed as modules over themselves.

Categories
Math

Constructing Compatible Operations 2

In this post, we continue the discussion from the previous in the series.

Categories
Math

An Abstract Approach to Generating Sets 4

In this post, we continue our discussion from the previous in the series.

Categories
Math

Constructing Compatible Operations

Recently in my ring theory class I heard about the theorem that if a ring satisfies x^{n} = x for some constant n, then it must be commutative. Now, note that this statement is made entirely in terms of multiplication. Thus, going off of the theme discussed in my post The Unreasonable Effectiveness of Definitions in Mathematics, we can wonder: is this in fact true for all monoids? If not, then what “data” is needed in the monoid to ensure that we can construct a compatible addition operation turning it into a ring? For such a monoid, we would be able to conclude commutativity.

Categories
Math

The Unreasonable Effectiveness of Definitions in Mathematics

Recently, I have been thinking about the unreasonable effectiveness of definitions in mathematics. Without making any additional assumptions or knowing any additional information about a situation, by simply making judicious definitions and studying their theory, we can get a lot farther than we could without those definitions. (As you might have noticed, “unreasonable” here is a nod to Eugene Wigner’s classic piece.) Upon further thought, it seems somewhat baffling that this works so well, especially in certain cases.