Automorphism proof (graph theory)

In summary: Yes, I'll take a look.In summary, the problem is attached and it's fully explained in the file attached.
  • #1
TheMathNoob
189
4

Homework Statement


The problem is attached and it's part A. There is no need to put problem 4 hence the problem is fully explained in the file attached

Homework Equations


Zk is mod k basically.

The Attempt at a Solution


I know that we have to prove that the transformation is onto,one to one and preserves adjacency.
It's one to one because
T(s1)=T(s2)
s1+v=s2+v
s1=s2

It's onto because
y=s+v
y-v=s
T(s)=T(y-v)=y-v+v=y
I am not quite sure how to show that it preserves adjacency because I can't apply the concept of hamming distance anymore.
 

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  • #2
Two vertices are adjacent iff they have identical coordinates in all dimensions except for one.

Say ##U## and ##V## are adjacent because their coordinates are identical except for the ##j##th one.

For which, if any, of ##u\in\{1,2,...,n\}## are the ##u##th coordinates of ##T(U)## and ##T(V)## equal?
 
  • #3
andrewkirk said:
Two vertices are adjacent iff they have identical coordinates in all dimensions except for one.

Say ##U## and ##V## are adjacent because their coordinates are identical except for the ##j##th one.

For which, if any, of ##u\in\{1,2,...,n\}## are the ##u##th coordinates of ##T(U)## and ##T(V)## equal?
Yes except for the jth coordinate?
 
  • #4
Yes, and what does that tell us about whether T(U) and T(V) are adjacent?
 
  • #5
andrewkirk said:
Yes, and what does that tell us about whether T(U) and T(V) are adjacent?
T(U) and T(V) are still adjacent because all their coordinates are the same except for the jth one.
 
  • #6
andrewkirk said:
Yes, and what does that tell us about whether T(U) and T(V) are adjacent?
I had another problem. I would be glad if you take a look.
 

1. What is an automorphism in graph theory?

An automorphism in graph theory refers to a mapping from a graph to itself, where the mapping preserves the structure of the graph. In other words, an automorphism is a permutation of the vertices of a graph that maintains the same edges and connections between vertices.

2. How do you prove that a graph has an automorphism?

To prove that a graph has an automorphism, you must show that there exists a permutation of its vertices that preserves its structure. This can be done by finding a specific permutation that satisfies the definition of an automorphism, or by showing that specific properties of the graph are invariant under certain permutations.

3. What is the significance of automorphisms in graph theory?

Automorphisms play an important role in graph theory as they help identify symmetries and patterns within a graph. They can also be used to simplify and analyze complex graphs by reducing the number of distinct structural components.

4. How do you determine the number of automorphisms in a graph?

The number of automorphisms in a graph can be determined by using the orbit-stabilizer theorem. This theorem states that the number of automorphisms is equal to the size of the graph's vertex set divided by the size of the stabilizer subgroup, which is the set of permutations that leave a specific vertex fixed.

5. Can a graph have multiple automorphisms?

Yes, a graph can have multiple automorphisms. In fact, most graphs have more than one automorphism. The number of automorphisms a graph has is dependent on its structure and can range from 1 (for a graph with no symmetry) to n! (for a complete graph with n vertices).

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