Difference between revisions of "741"

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'''Math 741'''
 
'''Math 741'''
  
Fall 2013 -- this page is no longer current!
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Fall 2016
  
 
Algebra
 
Algebra
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Prof: [http://www.math.wisc.edu/~ellenber Jordan Ellenberg]
 
Prof: [http://www.math.wisc.edu/~ellenber Jordan Ellenberg]
  
Grader:  Evan Dummit.
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Grader:  [https://www.math.wisc.edu/~eramos/ Eric Ramos].
* Homework policies:
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<!-- * Homework policies:
 
  * Late homework may be given directly to the grader, along with either  
 
  * Late homework may be given directly to the grader, along with either  
 
     (i) the instructor's permission, or (ii) a polite request for mercy.
 
     (i) the instructor's permission, or (ii) a polite request for mercy.
 
  * Assignments that are more than 1 page should be affixed in some reasonable way.
 
  * Assignments that are more than 1 page should be affixed in some reasonable way.
  * Results from places (e.g., the internet) other than 741 and standard books must be cited.
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  * Results from places (e.g., the internet) other than 741 and standard books must be cited.-->
  
JE's office hours: Monday 12pm-1pm (right after class)
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Homework will be due on Wednesdays.  
  
This course, the first semester of the introductory graduate sequence in algebra, will cover the basic theory of groups, group actions, representation, linear and multilinear algebra, and the beginnings of ring theory.
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JE's office hours:  Monday 12pm-1pm (right after class)
  
==SYLLABUS==
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This course, the first semester of the introductory graduate sequence in algebra, will cover the basic theory of groups, group actions, representations, linear and multilinear algebra, and the beginnings of ring theory.  A good understanding of the material of 741 and 742 are more than enough preparation for the qualifying exam in algebra.
  
In this space we will record the theorems and definitions we covered each week, which we can use as a list of notions you should be prepared to answer questions about on the Algebra qualifying exam.  The material covered on the homework is also an excellent guide to the scope of the course.
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==APPROXIMATE SYLLABUS==
  
 
'''WEEK 1''':   
 
'''WEEK 1''':   
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Definition of group.  Associativity.  Inverse.   
 
Definition of group.  Associativity.  Inverse.   
  
Examples of group:  GL_n(R).  GL_n(Z).  Z/nZ.  R.  Z.  R^*.  The free group F_k on k generators.   
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Examples of groups:  GL_n(R).  GL_n(Z).  Z/nZ.  R.  Z.  R^*.  The free group F_k on k generators.   
  
 
Homomorphisms.  The homomorphisms from F_k to G are in bijection with G^k.  Isomorphisms.
 
Homomorphisms.  The homomorphisms from F_k to G are in bijection with G^k.  Isomorphisms.
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'''WEEK 2''':
 
'''WEEK 2''':
  
The symmetric group (or permutation group) S_n on n letters.  Cycle decomposition of a permutation.  Order of a permutation.  Thm:  every element of a finite group has finite order.   
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The symmetric group (or permutation group) S_n on n letters.  Cycle decomposition of a permutation.  Order of a permutation.  Conjugacy classes of permutations.   
  
 
Subgroups.  Left and right cosets.  Lagrange's Theorem.  Cyclic groups.  The order of an element of a finite group is a divisor of the order of the group.
 
Subgroups.  Left and right cosets.  Lagrange's Theorem.  Cyclic groups.  The order of an element of a finite group is a divisor of the order of the group.
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==HOMEWORK 1 (due Sep 16)==
 
==HOMEWORK 1 (due Sep 16)==
  

Revision as of 14:42, 6 September 2016

Math 741

Fall 2016

Algebra

Prof: Jordan Ellenberg

Grader: Eric Ramos.

Homework will be due on Wednesdays.

JE's office hours: Monday 12pm-1pm (right after class)

This course, the first semester of the introductory graduate sequence in algebra, will cover the basic theory of groups, group actions, representations, linear and multilinear algebra, and the beginnings of ring theory. A good understanding of the material of 741 and 742 are more than enough preparation for the qualifying exam in algebra.

APPROXIMATE SYLLABUS

WEEK 1:

Definition of group. Associativity. Inverse.

Examples of groups: GL_n(R). GL_n(Z). Z/nZ. R. Z. R^*. The free group F_k on k generators.

Homomorphisms. The homomorphisms from F_k to G are in bijection with G^k. Isomorphisms.

WEEK 2:

The symmetric group (or permutation group) S_n on n letters. Cycle decomposition of a permutation. Order of a permutation. Conjugacy classes of permutations.

Subgroups. Left and right cosets. Lagrange's Theorem. Cyclic groups. The order of an element of a finite group is a divisor of the order of the group.

The sign homomorphism S_n -> +-1.


WEEK 3

Normal subgroups. The quotient of a group by a normal subgroup. The first isomorphism theorem. Examples of S_n -> +-1 and S_4 -> S_3 with kernel V_4, the Klein 4-group.

Centralizers and centers. Abelian groups. The center of SL_n(R) is either 1 or +-1.

Groups with presentations. The infinite dihedral group <x,y | x^2 = 1, y^2 = 1>.

WEEK 4

More on groups with presentations.

Second and third isomorphism theorems.

Semidirect products.

WEEK 5

Group actions, orbits, and stabilizers.

Orbit-stabilizer theorem.

Cayley's theorem.

Cauchy's theorem.

WEEK 6

Applications of orbit-stabilizer theorem (p-groups have nontrivial center, first Sylow theorem.)

Classification of finite abelian groups and finitely generated abelian groups.

Composition series and the Jordan-Holder theorem (which we state but don't prove.)

The difference between knowing the composition factors and knowing the group (e.g. all p-groups of the same order have the same composition factors.)

WEEK 7

Simplicity of A_n.

Nilpotent groups (main example: the Heisenberg group)

Derived series and lower central series.

Category theory 101: Definition of category and functor. Some examples. A group is a groupoid with one object.

WEEK 8

Introduction to representation theory.

WEEK 10

Ring theory 101: Rings, ring homomorphisms, ideals, isomorphism theorems. Examples: fields, Z, the Hamilton quaternions, matrix rings, rings of polynomials and formal power series, quadratic integer rings, group rings. Integral domains. Maximal and prime ideals. The nilradical.

Module theory 101: Modules, module homomorphisms, submodules, isomorphism theorems. Noetherian modules and Zorn's lemma. Direct sums and direct products of arbitrary collections of modules.