14-1100/Homework Assignment 1

DBN: Classes: 2014-15: 14-1100/Navigation Welcome to Math 1100! (additions to this web site no longer count towards good deed points) # Week of... Notes and Links 1 Sep 8 About This Class; Monday - Non Commutative Gaussian Elimination; Thursday - the category of groups, automorphisms and conjugations, images and kernels. 2 Sep 15 Monday - coset spaces, isomorphism theorems; Thursday - simple groups, Jordan-Holder decomposition series. 3 Sep 22 Monday - alternating groups, group actions, The Simplicity of the Alternating Groups, HW1, HW 1 Solutions, Class Photo; Thursday - group actions, Orbit-Stabilizer Thm, Class Equation. 4 Sep 29 Monday - Cauchy's Thm, Sylow 1; Thursday - Sylow 2. 5 Oct 6 Monday - Sylow 3, semi-direct products, braids; HW2; HW 2 Solutions; Thursday - braids, groups of order 12, Braids 6 Oct 13 No class Monday (Thanksgiving); Thursday - groups of order 12 cont'd. 7 Oct 20 Term Test; Term Test Solutions on Monday, HW3; HW 3 Solutions; Thursday - solvable groups, rings: defn's & examples. 8 Oct 27 Monday - functors, Cayley-Hamilton Thm, ideals, iso thm 1; Thursday - iso thms 2-4, integral domains, maximal ideals, One Theorem, Three Corollaries, Five Weeks 9 Nov 3 Monday - prime ideals, primes & irreducibles, UFD's, Euc.Domain$\Rightarrow$PID, Thursday - Noetherian rings, PID$\Rightarrow$UFD, Euclidean Algorithm, modules: defn & examples, HW4, HW 4 Solutions 10 Nov 10 Monday - R is a PID iff R has a D-H norm, R-modules, direct sums, every f.g. module is given by a presentation matrix, Thursday - row & column reductions plus, existence part of Thm 1 in 1t3c5w handout. 11 Nov 17 Monday-Tuesday is UofT's Fall Break, HW5, Thursday - 1t3c5w handout cont'd, JCF Tricks & Programs handout 12 Nov 24 Monday - JCF Tricks & Programs cont'd, tensor products, Thursday - tensor products cont'd 13 Dec 1 End-of-Course Schedule; Monday - tensor products finale, extension/reduction of scalars, uniqueness part of Thm 1 in 1t3c5w, localization & fields of fractions; Wednesday is a "makeup Monday"!; Notes for Studying for the Final Exam Glossary of terms F Dec 15 The Final Exam Register of Good Deeds Add your name / see who's in! See Non Commutative Gaussian Elimination

This assignment is due at class time on Monday, October 6, 2011.

Part I

Web search "Rubik's Cube Variants" (look at images), or look at Wikipedia: Combination Puzzle or TwistyPuzzles.com, or search elsewhere or go to a toy shop, pick your favourite "permutation group puzzle" (other than the Rubik Cube, of course), and figure out how many configurations it has. For your solution to count the number of configurations must be more than you can count, and your solution must include a clear picture or diagram of the object being studied, its labeling by integers, the list of generating permutations for it, and a printout of the program you used along with screen shot of its output (or an input/output log). It is ok to use the program presented in class (Mathematica is available on a departmental server; look for it!) but better to write your own. You can submit your solution either as a wiki page on this server (best option), or as a URL elsewhere (second best), or as a single file in any reasonable format, or on paper.

Part II

Solve the following questions.

1. (Selick) If $g$ is an element of a group $G$, the order $|g|$ of $g$ is the least positive number n for which $g^{n}=1$ (may be $\infty$). If $x,y\in G$, prove that $|xy|=|yx|$.
2. (Selick) Let $G$ be a group. Show that the function $\phi :G\to G$ given by $\phi (g)=g^{2}$ is a morphism of groups if and only if $G$ is Abelian.
3. (Lang, pp 75) Let $G$ be a group. For $a,b\in G$, the commutator $[a,b]$ of $a$ and $b$ is $[a,b]=aba^{-1}b^{-1}$. Let $G'$ be the subgroup of $G$ generated by all commutators of elements of $G$. Show that $G'$ is normal in $G$, that $G/G'$ is Abelian, and that any morphism from $G$ into an Abelian group factors through $G/G'$.
4. (Lang, pp 75) Let $G$ be a group. An automorphism of $G$ is an invertible group morphism $G\to G$. An inner automorphism is an automorphism of $G$ given by conjugation by some specific element $g$ of $G$, so $x\mapsto x^{g}$. Prove that the inner automorphisms of $G$ form a normal subgroup of the group of all automorphisms of $G$.

Part III

After September 25, identify yourself in the 14-1100/Class Photo page! It is best (though not mandatory) if you do that on the 14-1100/Class Photo page itself.