## Set Theory

 Unit code: MATH63021 Credit Rating: 15 Unit level: Level 6 Teaching period(s): Semester 1 Offered by School of Mathematics Available as a free choice unit?: N

#### Requisites

None

Students are not permitted to take MATH43021 and MATH63021 for credit in an undergraduate programme and then a postgraduate programme.

#### Aims

To introduce students to set theory and its role in mathematics.

#### Overview

The study of abstract set theory was started by Georg Cantor who, whilst studying trigonometric series, came up against problems involving iterative processes which could be applied more than a finite number of times. Out of this work came the revolutionary idea of transfinite numbers, which could be used to compare the sizes of infinite sets. A naive approach to set theory leads to paradox and it was left to Zermelo to propose an axiomatic approach that puts set theory on a sound rigorous basis.

We will study Zermelo-Fraenkel axioms for set theory, and redo some of the material from the Mathematical Logic course in this formal setting.  We will also look at the role of the Axiom of Choice, in both set theory and other parts of the mathematics.

We will then study cardinal arithmetic in some detail before moving on to some infinite combinatorics. The combinatorics will be applied to prove Silver's theorem, that the generalised continuum hypothesis cannot first fail at singular cardinals of uncountable cofinality.

#### Learning outcomes

On completion of this course students will be familiar with:

• Formalise the basic concepts of set theory in the system ZF.
• Apply the axioms of ZF to construct ordinals and cardinals.
• Formulate and proof basic properties of cardinality in ZF.
• Distinguish those arguments which require the axiom of choice.
• Prove equivalences between various forms of the axiom of choice.
• Prove various inequalities in cardinal arithmetic.
• Apply the generalised continuum hypothesis to determine cardinal exponentials.
• Prove basic results on clubs and stationary sets.

#### Assessment methods

• Other - 20%
• Written exam - 80%

#### Assessment Further Information

• One coursework assignment; weighting 20% each,
• End of semester examination: three hours; weighting 80%

#### Syllabus

2. Well-orderings, ordinals and transfinite induction [6]
3. The size of sets [4]
4. The axiom of choice [3]
5. Cardinal arithmetic [5]
6. Clubs, stationary sets, and Silver's theorem.  [5]

There is no recommended textbook for this course but the following text books cover much of the material.

1. H.B. Enderton, elements of Set Theory, Academic Press.
2. K. Ciesielski, Set Theory for the Working Mathematician, London Mathematical Society Student Texts.
3. K. Hrbacek, T. Jech, Introduction to Set Theory, CHapman & Hall/CRC Pure and Applied Mathematics.
4. Y.N. Moschovakis, Notes on Set Theory, Springer-Verlag Undergraduate Texts in Mathematics.
5. K. Kunen, Foundation of Mathematics, College Publications.

#### Feedback methods

Feedback tutorials will provide an opportunity for students' work to be discussed and provide feedback on their understanding.  Coursework also provides an opportunity for students to receive feedback.  Students can also get feedback on their understanding directly from the lecturer, for example during the lecturer's office hour.

#### Study hours

• Lectures - 27 hours
• Tutorials - 6 hours
• Independent study hours - 117 hours

#### Teaching staff

Gareth Jones - Unit coordinator