Digraph Automorphisms: Counting Edge Colorings

  • Thread starter Thread starter Monte_Carlo
  • Start date Start date
AI Thread Summary
The discussion revolves around counting edge colorings for a specific digraph G with vertices {x, y, z, w} and edges {(x, y), (x, z), (x, w)}. The user, Monte, seeks clarification on the number of distinct edge colorings using various color combinations, including only white, both white and blue, and three colors: green, red, and blue. Monte believes the answer for the first scenario is 1 and for the second is 2, but this conflicts with a textbook answer. He expresses uncertainty about whether he posted in the correct forum section, as he is looking for guidance rather than direct answers. The thread highlights the challenges of understanding digraph automorphisms and edge coloring in abstract algebra.
Monte_Carlo
Messages
70
Reaction score
0
Hello,

I have the following abstract algebra problem. It has to do with digraph automorphisms.

You're given a digraph G with vertices V(G) = {x, y, z, w} and edges E(G) = { (x, y), (x, z), (x, w) }. How many essentially different ways are there to color the edges of G using the following colors:

1) only white
2) both white and blue, each at least once
3) green, red and blue, each at least once
4) all red, all blue or some red and some blue

For 1), I think the answer is 1
For 2), I think the answer is 2 but it disagrees with the answer in the book.

Please give me some direction and opinion, I don't think just answers will be useful.

Thanks,

Monte
 
Physics news on Phys.org
Since it's the first time I've posted a request for homework assistance, I realize I might have made several mistakes which would explain why nobody has proffered an attempt at solution. For one, I'm not sure if this section of the forum is the right one. I've seen descriptions of other sections, for example one for abstract algebra. However, there is an instruction not to post homework problems there. The problem I'm asking about is not, strictly speaking, a homework problem, but it is one at the end of a textbook chapter.

I'd be happy to hear if there is any other additional information that would be expected from me to elicit an attempt at solution from anybody at this forum.

Thanks,

Monte
 
Thread 'Have I solved this structural engineering equation correctly?'
Hi all, I have a structural engineering book from 1979. I am trying to follow it as best as I can. I have come to a formula that calculates the rotations in radians at the rigid joint that requires an iterative procedure. This equation comes in the form of: $$ x_i = \frac {Q_ih_i + Q_{i+1}h_{i+1}}{4K} + \frac {C}{K}x_{i-1} + \frac {C}{K}x_{i+1} $$ Where: ## Q ## is the horizontal storey shear ## h ## is the storey height ## K = (6G_i + C_i + C_{i+1}) ## ## G = \frac {I_g}{h} ## ## C...
Back
Top