*The Knot Book: an elementary introduction to the mathematical theory of knots.*American Mathematical Society, ISBN 0-8218-3678-1. Chapters 2 and 3.

## Section2.1Knots Overview

¶Studying rational tangles was a way to focus in a limited fashion on how crossings interact with one another to build intricate local structures that define a knot. But as an invariant for knots, the tangle number isn't perfect: it's most useful for rational knots, and even then, it can be challenging to rearrange a knot diagram into a twist-form rational tangle.

What we'd like instead are more *global* invariants that work for knots, invariants that capture the whole structure of the topology without relying upon making a specific set of choices along the way. This will come at the cost of needing invariants capable of conveying more algebraic information than a single rational number does: polynomials on one hand, and algebraic groups on the other.

### Subsection2.1.1Objectives

- Determine and contrast several ways to notate (tabulate) a knot using its crossings.
- Use numerical invariants for knots including the unknotting, bridge, and crossing numbers, to investigate relationships among classes of knots.

### Subsection2.1.2References

`http://www.ams.org/publicoutreach/feature-column/fc-2016-03`.

`http://www.csuchico.edu/math/mattman/NSF.html`.

*Knots and Links.*Corrected reprint of the 1976 original. Mathematics Lecture Series (7). American Mathematical Society. Chapter 3.