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# Group Theory

### Group theory, cardinality and isomorphic example problems

I would like to know how to identify and prove the cardinality of sets and how to identify isomorphic. (See attached file for full problem description) Group Theory: a. If S and T are sets then let TS denote the set of all functions from S to T. Prove that the cardinality of TSxU equals the cardinality of (TS)U b. C

### Formation of a Group under an Associative Product

Question: Let G be a nonempty set closed under an associative product, which in addition satisfies: (a) There exists an e in G such that e.a = a for all a in G. (b) Given a in G, there exists an element y(a) in G such that y(a).a = e. Then G is a group under this product.

### Group Theory - Group of Even Order

Modern Algebra Group Theory (XXII) Group of Even Order If G is a group of even order, prove it has an element a which is not equal to e satisfying a^2 = e. The fully formatted problem is in the attached file.

### Group Theory - Relation between Cyclic Group and Abelian Group : If the group G has five elements, show it must be abelian.

Modern Algebra Group Theory (XIX) Relation between Cyclic Group and Abelian Group If the group G has five elements, show it must be abeli

### Group Theory - Symmetric Set of Permutations..

Modern Algebra Group Theory (XIV) Symmetric Set of Permutations Symmetric Set of Permutations : Find order of all elements in S_3, where S_3 is the symme

### Group Theory - Symmetric Set of Permutations

Modern Algebra Group Theory (XI) Symmetric Set of Permutations In S3 give an example of two elements x,y such that (x.y)^2 is not equal to x^2.y

### How do you show that G is not an abelian?

Group Theory (X) In a group G in which (a.b)^i =a^i.b^i for three consecutive integers for all a,b belongs to G, then G is abelian. Show that the conclusion does not follow if we assume the relation (a.b)^i =a^i.b^i for just two consecutive integers.

### If is a group such that (ab)^2=a^2b^2 for all a,b belongs to G, show that G must be abelian. Or, Show that the group G is abelian iff (ab)^2=a^2b^2.

Modern Algebra Group Theory (VIII) If G is a group such that (ab)^2=a^2b^2 for all a,b belongs to G, show that G must be abelian. Or, Show that the group G is abelian iff (ab)^2=a^2b^2.

### Structure of Groups : Cauchy's Theorem, Order, Abelian Groups, Non-Abelian Groups, Isomorphisms and Subgroups

Let G be any non-Abelian group of order 6. By Cauchy's theorem, G has an element, a, of order 2. Let H = a, and let S be the set of left cosets of H. (a) Show H is not normal in G. (Hint: If H is normal, then H is a subset of Z(G), and then it can be shown that G is Abelian) (b) Use the below result and part (a) to show th

### Time complexity of an algorithm in theta notation

How much time does the following algorithm require as a function of n? Express your answer in "theta notation" in the simplest possible form. Show all work! l = 0 for i = 1 to n for j = 1 to i for k = j to n l = l +1

### Period of a Group of Elements

Let a and x be elements in a group G. Prove that a and axb ,where b is the inverse of a, have the same period. Let G be a multiplicative group and a, x € G. Prove that for all n € N , (xax-1) = xanx-1 ( N is the set of natural numbers) Deduce that xax-1 has the same period as a

### Fundamental Groups, Path-Connected Space, Connectivity and Homotopy

Let X be a path-connected space and suppose that every map f: S^1 --> X is homotopically trivial but not necessarily by a homotopy leaving the base point x_0 fixed. Show that pi_1(X,x_0) = 0.

### Cyclic Groups, Generators and Orders of Elements

(1) Let G be a group such that ... Show that G cannot be cyclic. (2) Show that a cyclic group with one generator has at most 2 elements. (3) Let a 2 G be an element of order two, and b 2 G an element of order three. Show that HK where H = (a) and K = (b) has order 6. See the attached file.

### Group theory proofs

A. Let =2 +1 (2 (Power 2(power n))) Plus 1. Prove that P is a prime Dividing , then the smallest m such that P (2 -1) is m = 2 (hint use the Division Algorithm and Binomial Theorem) Please see attached.

### Semi-Direct Products, S4 Groups and Homomorphisms

Let G = (Z/3Z)^4 SemiDirectProduct S_4 be the semi-direct product of (Z/3Z)^4 and S_4. Here S_4 acts on (Z/3Z)^4 by permutating the coordinates. Hint: Given H1, H2 an element in (Z/3Z)^4 and K1, K2 an element in S4. The semi-direct product is given by the operation (H1, K1) * (H2, K2) = (H1 + K1(H2), K1 * K2) A) Find the C

### Group Theory Conjugacy, Cayley Table, Subgroups & Quotient Group

See the attached file. Define the notion of conjugacy as it applies in a general group. Prove that the inverses of a pair of conjugate elements are also conjugate. Prove that conjugate elements have the same order. (6 marks) The remainder of this question concerns the group G , whose Cayley table is as [TABLE] (b) Dete

### Group Theory : Symmetry Groups, Cyclic Subgroups

Thisquestion is concerned with subgroups ofthe group S5 of permutations on the set {1,2,3,4,5} , a group with 120 elements. (a) Explain why this group has cyclic subgroups of order 1,2,3,4,5 and 6, and give examples of each of these. Explain why this group does not have cyclic subgroups of any other order. (8 marks (b) By co

### Group Theory: Abelian Groups and Subgroups

3 (a) (i) Let G=Z12(sub12 don't know how to put it), the group of integers modulo 12. Prove that H= {0, 6} AND K= {0, 4, 8} are subgroups of G. Calculate the subset H+K formed by adding together all possible pairs of elements from H and K, i.e. H+K= {h+kh is a subgroup of H, k is a subgroup of K} Prove that this is also a

### Group Theory : Homomorphisms, Kernels, Isomorphisms and Fields

(a) If G1 and G2 are groups, define what it means to describe a function h:G1 -> G2 as a homomorphism. (b) If h: G1 ?> G2 is a homomorphism, define the kernel of h.Prove that the range of h is a subgroup of G2 , and that the kernel of h is a normal subgroup of G1. (c) Let G be the group of 2x2 real matrices under additi

### Group Theory : Homomorphism, Subgroups, Abelian Groups and Group Order

2.Let G be abelian of order n. If gcd(n;m) = 1, prove that f(g) = gm is an automorphism of G. (Note: Automorphism is just an isomorphism from G to itself.) 3. If f : Z7 ! Z5 is a homomorphism, prove that f(x) = 0 for all x 2 Z7. 4. Prove that in the group S10 every permutation of order 20 must be odd. 5. Suppose G is a group

### Group Theory 1. i. State the axioms for an equivalence relation ii. The relation n mod 3 divides the non-negative integers (i.e, n in Z such that n &#8805; 0) into how many partitions? Show that n = 0 mod 3 is an equivalence relation. 2. Prove that, for any matrices, A, B and C: A+B=B+A And: A+(B+C)=(A+B)+C ( i.e., that the matrix addition is both commutative and associative) For simplicity, prove these properties using 2x2 matrices. 3. Prove that addition modulo n, written + is: i. Associative. ii. Commutative. There are two ways to prove these properties. Each way requires a definition or two: i. For n &#8805; 2, 0 &#8804; a, b &#8804; n+1, a+ b= a+b if a+b< n a+n-n if a+b&#8805; n ii. Writing a for a mod n and (a+b) = a+ b, then: (p+ q) &#8801; (p +q ) Do the proof using both methods. Which is more "algebraic" (in the sense of "abstract" algebra)? 4. Prove that addition modulo n, written + is: i. Associative ii Commutative. ( extra definations required : a for a mod n and (pà?q) = pà? q, so (pà? q) (p à?q ) 5. i. State the axioms defining a group - If (Z, +) is a group, show that it is. Identify the identity element for +; in addition, for each n in Z , identify the inverse. Also show that + is associative. - If (Z, à?) is a group, show that it is. Identify the identity element for +; in addition, for each n in Z, identify the inverse. Also show that + is associative. - If (R, à?) is a group, show that it is. Identify the identity element for +; in addition, for each n in Z , identify the inverse. Also show that + is associative. iii. In each case, deterimine whether the algebraic structure is a group. For each such group: - show how it satifies the group axioms - Draw the cayley table for the group and list the inverse elements i. For S=(0,2), a+2b &#8801; (a+b) mod 2 and aà?2b &#8801; (a à?b)mod2 a. (S,+ ) ( possibly an additive group) b. (S,&#8729; 2) (possibly a multiplicative group). ii. For S = (0,1,2) where n=2,3 and + and à? are defined as in the last part. a. (S,+n) ( possibly an additive group) b. (S,&#8729; n) (possibly a multiplicative group). Determine whether any of the groups is an abelian group. If any of them are abelian: i. state the conditions under which a group is abelian ii. show that the group is abelian 6. there are only two groups of order four (Z 4and v). How many groups are there of the order five? Draw cayley tables for each one of them( the element should be named a,b,c,d,e) is either (or both) of the groups of order four subgroup of any of those of order five? If so which one 7. for each of the following structures, state whethere it is a group. If it is, state whether it is abelian or not. i.For any set, A, the set of one-to one and onto functions, f: A &#8594;A under composition ( written "&#9702;"). ii.The set of all subsets of the three-element set (a,b,c) ( there are eight such subsets) under: a. Union b. Intersection iii. The set G=(a+b&#8730;5| a,b in Q) under addition and multiplication iv The set consisting of non-zero numbers under a. addition b. division v. The set (1,5,7,11) under multiplication modulo 12. Draw cayley table vi. The set (4,6) under multiplication modulo 12. draw cayley table vii. The set of real numbers under à?, where aà?b = 2(a+b) viii The set of real numbers under +, where a+b = a+b-10 ix. The set of rotational symmetries of a regular hexagon under composition x The following sets of permutations under composition i. (e,(12),(123),(1234)) ii. (e,(12), (34), (12), (34)) 8.Let G be a group, (G, * ) in which there is an element, a , such that g * g=g . prove that g=e 9.Prove that for every element, a, of a group, G, the order of a and a^-1 are the same ( including the case of an infinite order) 10.Let x and y be elements of a group, G. Prove that the elements xy and yx have the same orders 11.Find the subgroups of i. Z7 ii. Z8 iii Z9 12. i. determine which of the folowign are subgroups of under + a. (0) b. (-1,0,1) c. (n| n=10m for some integer m d.(p| p is a prime number e. (0,1,2,3,4) under addition modulo 5 ii. Determine which of the following are subgroups of under mulitiplication: a. (1, -1) b. (x |x=3, for some integer n c. (x |x=p/2&#8319; for some integers, p,n) d. (x| x=k 3 for some interger k

Group Theory Group Theory 1. i. State the axioms for an equivalence relation

### Group theory : explained

1. let H be a subgroup of a group G such that g ֿ ¹ hg elements in H for all h elements in H. Show every left coset gH is the same as the right coset Hg. 2. prove that if G is an abelian group, written multiplicatively, with identity element e, then all elements, x, of G satisfying the equation x²=e form a sub group H o

### Group Theory : Cayley Tables, Cyclic Groups and Isomorphisms

? I have the following cayley tables (which is in modulo 9) determine the order of each element . Prove that G is a cyclic group. ? Let be the symmetric group of degree 3 together with composition of maps. Is G isomorphic to ? Justify your answer. ? Let p be a prime number and G a group of order with identity e

### Groups and Fields

Find H K in {see attachment}, if H={[1],[8]}, and K = {[1], [4], [10], 13], [16],[19]}.

### Direct Product Groups

Let G1 and G2 be groups, and let G be a direct product of G1 x G2. Let H = {(x1, x2) element G1 x G2 | x2 = e} and let K = {(x1, x2) element G1 x G2| x1 = e}. (a) Show that H and K are subgroups of G. (b) Show that HK = KH = G (c) Show that H [see attachment] K = {(e,e)}.

### Permutation Groups : Order of Rigid Motions of a Cube

Find the order of the group of rigid motions of a cube.

### Groups and Subgroups

Let G sub1 and G sub 2 be groups, with subgroups H sub 1 and H sub 2, respectivetly. Show that {(x sub 1, x sub 2) | H sub 1 is an element of H sub 1, x sub 2 is an element of H sub 2} is a subgroup of the direct product G sub 1 x G sub 2.

### Abelian Groups

Prove that if G1 and G2 are abelian groups, then the direct product G1 x G2 is abelian.

### Groups: Third Sylow Theorem

Suppose a simple group G of order 660 is a subgroup of the symmetric group S11 (here S is with 11 as a subscript ) and x = {1,2,3,4,5,6,7,8,9,10,11}( a permutation like 1 goes to 2 and so on, I think ) in G. If P equals the span of x ( or <x> ) determine the permutations which generate NGP ( here G is written as the subscript of

### Rings and Groups (Ring Theory, Quaternions, Homomorphisms, Matrices)

A number of questions involving rings and groups. Example: 3) Let R be a ring and [equationA]. Let [equationB] be the ring of n x n matrices with entries in R. What is the identity element of S? *(Please see attachment for complete list of problems)