BSM Set Theory — SET 2014S.
Instructor: Dr. Lajos SOUKUP
EMail: If you have any question, do not hesitate to write me:
soukup@renyi.hu or lsoukup@gmail.com
Gmail chat: lsoukup@gmail.com
Homepage:
http:www.renyi.hu/~soukup
Classes:
Prerequisite: Some familiarity with "higher" mathematics.
No specific knowledge is expected.
Course description
 We get an insight how
set theory can serve as the foundation of mathematics: all mathematical concepts, methods, and results can be represented within set theory.
 We study how to build up a rich mathematical theory from simple axioms.
 We learn how to use set theory as a powerful tool in algebra,
analysis, and even geometry
 Since set theory is also an independent branch of mathematics, like algebra or geometry, with its own subject
matter, basic results, open problems, the course tries to catch a glimpse of some results and problems from contemporary set theory, especially from infinite combinatorics.
In this course, set theory is developed axiomatically, but the treatment is not formal. Logical apparatus is kept to minimal, and logic formalism is completely avoided.
Topics:
 Naive set theory. Basic principles:
 Extensionality: Two sets are equal if and only if they have the same elements.

General principle of comprehension:
If P(x) is a property, then there is a set Y={x:P(x)} of all elements
having property P.
 Countable and uncountable sets. An application: there are uncountably many transcendental real numbers.
 Inductive constructions. The infinite Ramsey Theorem.
 The fall of naive set theory:
The general principle of comprehension leads to contradiction.
 Russel's Paradox:
Does the set of all those sets that do not contain
themselves contain itself?
 The solution: keep Extensionality, and replace the faulty General Comprehension with some weaker hypotheses, axioms, which are necessary for the proofs of the fundamental
results and seemingly free of contradiction.
For example,
 Axiom of Pairing: For any set A and set B, there is a set C such that x ∈ C if and only if x=A or x=B.
 Axiom Schema of Separation: Let P(x) be a property of x. For each set A there is set B such that
x ∈ B if and only if x ∈ A and P(x).
 Basic mathematical constructions using the Axioms: Ordered pairs, relations and functions, Cartesian product, partial and
linearorder relations, equivalence relations.

Natural numbers. The Axiom of Infinity and the settheoretic definition of the natural numbers.

Cardinalities. Basic operation on cardinalities.
Elementary properties of cardinal numbers.
CantorBernstein 'Sandwich' Theorem and its consequences, A < P(A).
 Wellorderings. Transfinite
Induction and Recursion : Ordinal numbers, and ordinal arithmetic.
 Axion of Choice and its equivalents : the Well Ordering Theorem, Zorn lemma, and the Fundamental Theorem of Cardinal Arithmetic.
 Applications (as many as time permits):
 Hamel
basis; the additive groups of the reals and of the complex numbers are isomorphic;
the function f(x)=x is the sum of two periodic functions.
 Mazurkiewicz theorem: there is a subset of the plain which intersects every line in exactly
two points. Find/create generalizations of this theorem

Dehn's Theorem about decompositions of geometric bodies
 Sierpinski's Theorem and the Continuum Hypothesis,
 decomposition of R^{3} into congruent circles,
 Infinite combinatorics: pressingdown lemma, partition theorems, Δsystems
 Goodstein's Theorem.
 A glimpse of independence proofs: New axioms: large cardinals, ⋄ and Martin's Axiom
Text: The course is based on printed handouts, which are distributed after classes.
Books:

Karel Hrbacek, Thomas Jech: Introduction to Set Theory, (Chapman & Hall/CRC Pure and Applied Mathematics)
 Yiannis Moschovakis: Notes on Set Theory (Undergraduate Texts in Mathematics, Springer)
Grading: Homework assignments: 50%, midterm exam: 20%, final exam: 30%.
A: 80100%, B: 7079%, C: 6069%, D: 5059%