Groups Definition and 906 Threads

Google Groups is a service from Google that provides discussion groups for people sharing common interests. The Groups service also provides a gateway to Usenet newsgroups via a shared user interface.
Google Groups became operational in February 2001, following Google's acquisition of Deja's Usenet archive. Deja News had been operational since March 1995.
Google Groups allows any user to freely conduct and access threaded discussions, via either a web interface or e-mail. There are at least two kinds of discussion group. The first kind are forums specific to Google Groups, which act more like mailing lists. The second kind are Usenet groups, accessible by NNTP, for which Google Groups acts as gateway and unofficial archive. The Google Groups archive of Usenet newsgroup postings dates back to 1981. Through the Google Groups user interface, users can read and post to Usenet groups.In addition to accessing Google and Usenet groups, registered users can also set up mailing list archives for e-mail lists that are hosted elsewhere.

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  1. H

    Centers of groups and products of groups

    I need to prove that the center of the product of two groups is the product of their centers. If I let G and H be two groups, then from definitions, the center of G is Z(G)={z in G such that zg=gz for g in G} and the center of H is Z(H)={z in H sucht that zh=hz for all h in H}. Also, the...
  2. homology

    Exploring Homology and Graded Groups

    Hello, I'm studying homology and graded groups have come up. I don't completely understand what they are. Wikipedia didn't have an entry on graded groups, but on graded algebras and other graded stuff and the definitions there seemed different than the way graded groups have been used...
  3. H

    Groups containing no proper subgroup

    1. Describe all groups G which contain no proper subgroup. This is my answer so far: Let G be a such a group with order n. Then the following describe G: (a) Claim that every element in G must also have order n. Proof of this: If this wasn't true, the elements of lower order (elements of...
  4. kakarukeys

    Is Isomorphism of Matrix Groups Always Expressed by Linear Maps?

    Can isomorphism of matrix groups \phi: G_1 \rightarrow G_2 always be expressed by \phi(M) = S M S^{-1}?
  5. M

    Define R/Q: How to Add in Quotient Groups

    how to define R\Q?(under addition) R\Q={a+Q:? <a<?} a€R but if it is not bounded then it will repeat please help me n
  6. A

    How to Classify Groups of Order pq² with Given Conditions?

    Let p and q be primes with q < p, and q ł (p-1). If G is a group with |G| = qp², then there are two possibilities if G is abelian by the fundamental theorem for finitely generated abelian groups: Zp x Zpq and Zqp² G has a normal Sylow-p subgroup (of order p²) and if we call it H, and call...
  7. J

    Commutators and solvable groups

    I am not really clear on what is meant by commutators. I know that the commutator of G is ABA^-1B^-1, but I am not sure how to check if a group is solvable by having the commutator eventually equal the trivial group. For example, I know that the Heisenberg group of 3x3 upper triangular...
  8. J

    Help with Paradoxical Groups: Vectors, Finite Groups, F3 & Z

    Hi, I need some serious help in paradoxical groups! 1) Given vectors v1,v2 in R2 and w1,w2 in R2 (none lieing on a line thru the origin), show that you can find a unique C such that Cv1=w1 and Cv2=w2. 2) Show that a finite group is not very paradoxical. 3) Is F3 paradoxical? Is Z...
  9. R

    Calculating Orbits of Groups: SO(3)

    group theory : orbits hi. I'm trying to calculate the orbits of some simple groups. I have found many explanations of what they are, but no example calculations. does anyone have any ideas where to look. I'm trying to calculate the orbit of SO(3). thanks
  10. G

    Heat Radiation by Groups of Atoms

    Does anybody have any thoughts on why atoms that are warm need to radiate heat in order to stop vibrating or bond back together? The obvious example is the thermos. That is a thermos has the hot liquid contained in a glass container with a mirrored surface towards the inside and then a...
  11. A

    Wallpaper Groups, Free Groups, and Trees

    1. Describe the elements of the groups c2mm, p4mm, and p3m1. My book doesn't do a good job of explaining this notation, any help? 2. Let m and n be positive integers. Prove that there is a homomorphism from the free group generated by n generators, F_n, onto the free group generated by m...
  12. quasar987

    Groups of Even Order Containing Odd Number of Elements of Order 2

    Show that if G is a finite group of even order, then G has an odd number of elements of order 2. I'd appreciate a tip or two. I really don't see how the order of the elements of a group is linked to the order of that group.
  13. H

    How you add gauge groups to spacetime

    I wanted to restart this discussion b/c the previous thread got sidetracked, and something about it has left me deeply confused, and I think my confusion is similar to the original posters confusion. In Wigners theory, particles (like say an electron) are unitary irreducible representations...
  14. Z

    Can the Direct Sum of Cyclic Groups Determine the Properties of Finite Groups?

    Assume G is a finite group and H = \left\{ {g \in G|g^n = e} \right\} for any n>0. e is identity. I have been able to show that if G is cyclic, then H has at most n elements. However, I can't go the other way. That is, assuming H has at most n elements, I haven't been able to say anything...
  15. S

    Van Kampen's theorem and fundamental groups

    I didn't see a topology forum, so I thought I'd post this question here. Can anyone give any pointers on using van Kampen's theorem? I understand the basic way it works, decompose a space X into open, path-connected sets, say U and V. Then pi1(U) * pi1(V) = pi1(X)/N, where N is a normal...
  16. C

    Comparing Reactivity of Chemical Groups: OH-R to O_4S-R

    There are several substanecs different only in a chemical group linked to the same opsition for all those substances. how can i know which one reacts fastest ? ie , OH-R, ON_2-R, O_3P-R, O_4S-R... Thanks
  17. C

    Finite groups and order of their elements

    Hi, This time around I need to prove that a finite group of order 10 must contain an element of order 2 and an element of order 5. If the group is cyclic then this is trivial. So assuming the group is not cyclic, it's easy to show that there exists an element of order 2 in the group. And...
  18. V

    Abstract Algebra: Groups of order 21

    I was given a problem to prove there are at most 3 groups of order 21, with extra credit for proving there are at most 2. I am pretty stuck on this one but here is what I have so far: Suppose G is a group of order 21 Let K be a sylow 3-subgroup of G and let H be a sylow 7-subgroup of G...
  19. E

    What are the prerequisites for understanding surgery obstruction groups?

    I need a crash course in surgery obstruction groups. Where should I go to find information on this topic, or does anyone know something about it? Thanks.
  20. A

    Order of Group Elements in Abelian and Non-Abelian Groups

    if a group of order 2p ( p prime) is abelian...then does it have exactly one element of order 2 ?? if a group is non abelian...i could figure out that there are p elements of order 2. but the abelian case is a bit confusing... also..is it like...any group of order 2p has an element of order p...
  21. A

    Find:2 Non-isomorphic groups of order n squared. help?

    Find:2 Non-isomorphic groups of order n squared i think that Zn X Zn is one. Can you help me find another. Thanks
  22. D

    Symmetry, groups and gauge theories in the standard model

    This is my (limited) understanding of particle physics: In particle physics gauge symmetries play an important role. To allow for massive gauge bosons this symmetry is broken. The theory of weak interactions can be derived from a local SU(2) symmetry, and quantumchromodynamics from a local SU(3)...
  23. D

    Can the multiplicative group of a finite field be proven to be cyclic?

    Letting F be a finite field, how would one show that the multiplicative group must be cyclic? I know that if the order of F = n, then the multiplicative group (say, F*) has order n - 1 = m. Then g^m = 1 for all g belonging to F*. Thanks for your time and help. dogma
  24. P

    Proving the Order of Elements in a Finite Group G

    For a finite group G, I need to prove that the order of an element in G is a divisor of the order of the group. I'm not sure what this exactly means, but I think you have to use cyclic groups such that G={a^0,a^1,...,a^n) where n+1 is the order of the group and a^0 is the identity element. So I...
  25. D

    Electrophilic Aromatic Substitution: NO2 & NO Groups

    The NO2 group directs meta with-deactivation in electrophilic aromatic substitution. The nitroso group - NO directs ortho-para with - deactivation. Write out the electroinc structures of - NO2 and -NO and explain the differences in behavior. Show all pertinent resonance forms for the addition of...
  26. marlon

    What do topologically stable maps mean?

    Hi I have this question on homotopy groups: Spacial infinity in two dimensional space is a unit circle S1 (topologically). I understand that. Now, in physics one can prove that fields will exhibit an equation (expressed by the map phy --> v =constant) that also represents a unit circle. Now...
  27. S

    Determine how many groups of a given number are in a entire set

    Hello all. I'm looking for an equation, one that I use to know how to figure out(but alas I am getting old and senile), that will alow me to determine how many groups of a given number are in a entire set. For example; in a set of 5, how many possible groups of 3 would there be? The answer is...
  28. G

    Functional groups present are: C=O and NH2

    This is about amines: The functional groups present are: C=O and NH2 Why does the N get protonated always but not C=O, since the oxygen has more lone pairs and more electronegative than N so shouldn't the oxygen be protonated more easily? I can't think of any good reasons... please help...
  29. Q

    Tensors & Differential Geometry - What are lie groups?

    Tensors & Differential Geometry -- What are lie groups? I've heard a lot about "lie groups" on this section of the forum, and was wondering what they are and if someone could explain it in simple terms. Thank you.
  30. A

    How to Start Learning Lie Groups with Minimal Physics Background?

    Hi all, I wanted to study Lie groups and their connections with differential geometry. But i don't want to get involved with lots of 'deep physics'. I am familiar with a little bit of group theory. can somebody suggest the right introductory material like tutorial papers or books for such a...
  31. N

    A Carbon skeleton with 2 diff functional groups

    Lets say for example a hydrocarbon skeleton has two diff functional groups branched to the skeleton.. Let's say one of the functional groups pH is less than 9 to 10, and the other functional group's pH is greater than 2 to 4 that means that molecule to be electrically charged, the pH of the...
  32. S

    Even Order Groups: Counting Elements of Order 2

    Prove: a group of even order must have an even number of elements of order 2
  33. G

    Why are groups, rings, and fields defined in the way that they are?

    Groups, Rings, Fields? I know what groups, rings, and fields are. My question is why are groups, fields, and rings defined the way they are? Why did mathematicians chose the properties that they did that define groups, rings, and fields? What is so special about those properties? Why...
  34. S

    Prove Beta is an isomorphism of groups

    i can't grasp these concepts, 1-to-1 and onto have always annoyed me. here's 1 question, (i don't know how to post symbols so Beta ..) (C is Complex numbers) Let Beta:<C,+> -> <C,+> by Beta(a+bi)=a-bi (that is, the image is a +(-b)i). Prove Beta is an isomorphism of...
  35. E

    A bit of trouble with Galois groups

    Is the Galois group of F=Q(sqrt2,3i) the maps {id, tau , sigma, gamma}, where (1) id is the identity (2) tau maps sqrt2 to -sqrt2 and leave 3i alone (3) sigma leaves sqrt2 alone and maps 3i to -3i (4) gamma maps sqrt2 to -sqrt2 and 3i to -3i ? If so, the what are the fixed fields of the...
  36. A

    Number of Elements of Order 5 in S7 Permutation Group

    what is the number of elements of order 5 in the permutaion group S7?? so what we're concerned with here is, after decompositon into disjoint cycles the l.c.m of the lengths must be 5. since 5 is a prime, the only possible way we could get 5 as l.c.m would be to fix ANY 2 elements amongst the 7...
  37. C

    Blood groups and transfusions .

    Blood groups and transfusions... I have learned that when you transfuse the wrong blood to a recipient whose antibodies work against the donated blood that agglutination occurs. eg - if you transfuse A blood to a B person, since the B person will possesses anti-A antibodies which will cause...
  38. Math Is Hard

    Deciphering the Complexity of Group 1B Elements in the Periodic Table

    I've got one of those "research in other resources" questions in my chemistry homework. (meaning the info isn't in the lecture or the text, I guess ). It goes like this: Consider Group 1A and Group 1B of the periodic table. The text states that although A groups have very regular patterns...
  39. maverick280857

    Organic Chemistry Q&A: Activating and Deactivating Groups

    Hi I have a few questions in organic chemistry. I would be very grateful if someone can answer them: 1. (cf Morrison & Boyd 6th ed page 523). "Strongly activating groups generally win out over deactivating or weakly activating groups." When the bromination of 3-hydroxybenzaldehyde...
  40. marlon

    Exploring Lie Groups and Their Use in Physics

    Here is a nice question I know that exponentiating elements of a Lie-Algebra gives you back an element of the Lie-Group. These Lie-algebra-elements generate the Lie-Group transformations. Like the Galilei-group, these Lie-groups are used in theoretical fysics as the great START, I mean they...
  41. V

    The Five Cultural Groups: A Retrospective of 1975

    My club has five cultural groups. They are literary, dramatic, musical, dancing and painting groups. The literary group meets every other day, the dramatic every third day, the musical every fourth day, the dancing every fifth day and painting every sixth day. The five groups met on the new...
  42. Oxymoron

    Showing Two Groups are Isomorphic

    How would I show that two groups are isomorphic? FOR EXAMPLE: Take the group homomorphism &phi; : ((0, oo), x) &rarr; ((0, oo), x) defined by &phi; (x) = x&sup2; Since &phi; is taking any element in (0, oo) and operating on it by x, does it map one-to-one and onto to (0, oo)? I...
  43. N

    Solving for Generators in Abelian Groups with Multiple Relations

    Okay, I'm really scratching my head here. If an Abelian group A has three generators x,y,z and they are subject to three defining relations, say something like x+y+z=0 x-y-z=0 2x-2y+3z=0 then I can solve for x,y,z and find A as a direct sum of cyclic groups, Z_x + Z_y + Z_z. But...
  44. N

    Belian group A that is the direct sum of cyclic groups

    If I have an abelian group A that is the direct sum of cyclic groups, say A=[tex]C_5 \oplus C_35[\tex], would I be right in saying the annihilator of A (viewed as a Z-module) is generated by (5,35)? If not, how do I find it?
  45. turin

    Structure constants of Lie groups

    Source: Anderson, Principles of Relativity Physics p. 13, prob. 1.4 "Reparametrize the rotation group by taking, as new infinitesimal parameters, ε1 = ε23, ε2 = ε31, and ε3 = ε12 and calculate the structure constants for these parameters." My assumptions: (1) The εij mentioned in...
  46. J

    What Are the Non-abelian Groups of a Given Order?

    Given a group of a certain size, I'm interested in determining whether a non-abelian group of that order exists, and if so how many and what are they up to isomorphism. For example, for |G|=6, the permutation group S_3 is non-abelian. How can I show that any non-abelian group of order 6 is...
  47. B

    How Do SU(n) Generators Model Cooper Pairing in Superconductors?

    Is there any general method to construct the generators of a SU(n) group?
  48. N

    Genetic groups in the modern world

    There's been some interesting discussions in this sub-forum on IQ, intelligence, the g Factor, races, hereditability, a nation's wealth, eugenics, and other things. One thing I found particularly interesting in this discussion is the work of Cavalli-Sforza into pre-1492 population groups and...
  49. A

    Exploring Groups for GR and Quantum Gravity

    In trying to get my head round GR and quantum gravity, I'm puzzled about the following questions: Is the gauge group for gravity defined as the group of all possible Weyl tensors on a general 4D Riemann manifold? Is it a subgroup of GL(4)? How do you derive the number of gravitational...
  50. A

    Gauge Groups, Riemann Tensors & Conformal Invariance in GR & QG

    In trying to get my head round GR and quantum gravity, I'm puzzled about the following questions: Is the gauge group for gravity defined as the group of all possible Weyl tensors on a general 4D Riemann manifold? How is this group defined in matrix algebra? Is it a subgroup of GL(4). How do...
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