abstractmath.org 2.0
help with abstract math

Revised 2016-03-05      website TOC      website index   blog


# INTRODUCTION

CONTENTS

## Who is this website for?

Abstractmath.org is designed for people who are beginning the study of some part of abstract math. This includes:

• University math majors or beginning grad students taking math courses that require working with abstract definitions and understanding and creating proofs.
• Teachers of university courses like those just described.
• Professionals who need to learn math (in any one of many fields) that is described in terms of mathematical properties with no reference to applications.
• Anyone who is curious about advanced math!

## What is abstract math?

Abstract math is my name for what is often called “higher math” or “pure math”.

• Abstract Math provides the conceptual background and theory that justfies the way math is used in applications..
• Abstract math requires conceptual reasoning about abstract ideas  (as well as manipulating symbols), in particular on understanding and constructing proofs.
• Abstract math is mathematics for its own sake. In doing abstract math, you state theorems and prove them mostly in the context of mathematical ideas rather than applications or ideas from other fields.
• When you first meet up with abstract math, you may find it hard to understand or even bizarre. If you need to know some piece of abstract math you may find the texts in the subject appear to be unmotivated and full of mysterious chains of reasoning. This happens to many people who are quite good at solving trig, derivative and integral problems.

## Overview of the site

This website is a multiple-entry site with many cross-links. This overview will give you a start on finding out what is on it.

### The four main parts of the website

These head pages explain the ideas of that part in more detail:

The languages of math

Proofs

Understanding math

Doing math

Abmath also has articles on certain mathematical topics:

Numbers

Sets

Functions

• These topic articles describe a few of the basic ideas of each topic.
• They define the ideas precisely and describe how to think about them.
• None of the articles go very far into the subject, but there are links to websites that cover the subjects more thoroughly.

### Other things on this website

Background and Attitude: This article describes some of the thinking behind this website.

Diagnostic examples: These examples illustrate some of the many kinds of difficulty people meet with when studying and doing abstract math. Each example gives links to the relevant sections of the website.

Gyre&Gimble: A blog that discusses new ideas I have about abstract math and language, some specifically related to abstractmath.org.

Discrete Mathematics Class Notes: An introduction to abstract math for computing science students based on some of the ideas of abstractmath.org.

Mathematica notebooks and CDF files: These are the sources for most of the diagrams, including interactive diagrams, in abmath and in the Gyre&Gimble posts.

Expository articles.

All the abstractmath.org articles and all the other documents listed in this section are licensed under a Creative Commons Attribution-ShareAlike 2.5 License.

## Reading this website

### Links

This website is aimed at people with widely varying knowledge of parts of math. When some sort of math object or method is mentioned, it is usually linked to a definition or explanation in Wikipedia or somewhere else in abstractmath.org.

I encourage you to click on the link if you are not sure you understand a word or phrase in blue. This is particularly important if the word is an ordinary English word rather than a technical word such as "homomorphism", because mathematicians routinely give ordinary words technical meanings which may be quite different from their ordinary meanings, for example "definition" and "group".

### Purple prose

Many of the important ideas about mathematics in this site are summarized in

 Slogans in Purple Prose Displayed Like This
• I put the slogans in purple prose because they are aimed at correcting deep misunderstanding that some readers will have about certain topics. Take purple prose statements seriously.
• It takes work to understand all the ins and outs of purple-prose slogans. Many of them require thinking about things in a way that is very different from the way you think about things in daily life.
• Some of them are difficult to believe and put into practice.

### Images and metaphors

In many places in abmath you will find a section or an article with the phrase "images and metaphors" in its title. An article title "Images and metaphors for [topic]" will tell you about how to think intuitively about [topic]. Gaining intuition about a topic in math is as important as learning how to understand and come up with proofs.

Intuition is both vitally necessary and dangerous, since it can mislead you. The article baldly titled Images and Metaphors explains this aspect of doing math in general, and it is worth looking at to get an overview of what is going on when you read (for example) Functions: Images Metaphors and Representations (big article) or Images and Metaphors for Rational Numbers (little bitty section).

### Mathematica

Most of the abmath articles are illustrated by diagrams created in Mathematica. The programming for these illustrations are in Mathematica notebooks, all of which have a file extension ".nb". The illustrations are all .gif, .jpeg or .png files. All these files are in the directory Mathematica Notebooks, many of them in subdirectories. In addition there are interactive documents with extension ".cdf".

#### How to use the notebooks

• If you own or have access to Mathematica 10.4, you can load an .nb file into Mathematica and run the interactive commands (the ones with sliders), turn any 3D diagram to get better views, and change and run any command in any way you want.
• If you own CDF Player, you can load an .nb or .cdf file into the player and run the interactive commands and turn 3D diagrams around. But you can't change the document or compile any command in it.
• Some of the notebooks are also supplied as .pdf files. If you don't have CDF player, you can download the PDF version of the document and read it. (The .nb file can be read in an editor but it is written in an impenetrable code.)

## Other sources for math

### Math sites

I provide links to other treatments of a specific topic at the point where they are discussed. These general links are particularly useful for learning about various aspects of math:

Mathematical Association of America

American Mathematical Society.

Math Forum

Mathworld

MathOverflow A question and answer site for professional mathematicians

MathStackExchange A question and answer site for people studying math at any level and professionals in related fields

$n$-Category Cafe

Planet Math

+plus magazine

Wikipedia

Wolfram Alpha

### Math Blogs

Explaining Mathematics

Gowers’s Weblog

Gyre&Gimble

Pat’s Blog

Plus Magazine Blog

Roots of unity

Visual Insight

### Books on beginning abstract math

The books listed below are suitable for people beginning abstract math.  Except for the Handbook, they emphasize different aspects of abstract math from what this website emphasizes.

Ash, Robert, A Primer of Abstract Mathematics.

Wells, Charles, The Handbook of Mathematical Discourse. Infinity Publishing Company, 2003.

### Articles and blog posts about abstract math

Bagchi, Atish and Charles Wells, Varieties of Mathematical Prose (1997).

Bagchi, Atish and Charles Wells, Communicating Logical Reasoning PRIMUS (1998).

Wells, Charles, Communicating mathematics: useful ideas from computer science. American Mathematical Monthly 102, 1995.

### University courses containing abstract math

Courses that math majors must take typically include some of these:

• Linear Algebra
• Abstract Algebra (or Modern Algebra)
• Advanced Calculus
• Discrete Math
• Number Theory

All of them may involve abstract definitions and require doing proofs.

## Acknowledgments

I am grateful to Case Western Reserve University for providing software and library privileges.

This work is licensed under a Creative Commons Attribution-ShareAlike 2.5 License.