Math Problem Statement

In the question (2)above, let us take n=4 in the module (A), i.e., the ring R[S4]  acts on  M=R4 as defined above. Let X=13124−11243∈R where the permutations appearing in X are written in one-line notation. What is the value of X⊙(5,6,7,8) ?

Solution

Let's break this down and find the value of X(5,6,7,8)X \odot (5,6,7,8), where X=1312411243R[S4]X = 13124 - 11243 \in R[S_4], and we are using the action of the symmetric group S4S_4 on M=R4M = R^4 as defined.

Step 1: Understand the problem and notation

  • R[S4]R[S_4] is the group algebra of the symmetric group S4S_4, which consists of all permutations on four elements.
  • X=1312411243X = 13124 - 11243 is an element of R[S4]R[S_4], and the permutations 1312413124 and 1124311243 are written in one-line notation.
    • 1312413124 likely represents the permutation that sends (11,23,31,42)(1 \to 1, 2 \to 3, 3 \to 1, 4 \to 2).
    • 1124311243 represents the permutation sending (11,21,32,43)(1 \to 1, 2 \to 1, 3 \to 2, 4 \to 3).

We are tasked with computing the action of X=1312411243X = 13124 - 11243 on the tuple (5,6,7,8)(5, 6, 7, 8).

Step 2: Apply the permutations

Action of 1312413124 on (5,6,7,8)(5, 6, 7, 8)

The permutation 1312413124 acts as follows:

  • 111 \to 1 means the first element remains the same, so the first element of (5,6,7,8)(5, 6, 7, 8) stays 5.
  • 232 \to 3 means the second element becomes the third, so the second element becomes 7.
  • 313 \to 1 means the third element becomes the first, so the third element becomes 5.
  • 424 \to 2 means the fourth element becomes the second, so the fourth element becomes 6.

Thus, 1312413124 acting on (5,6,7,8)(5, 6, 7, 8) gives: 13124(5,6,7,8)=(5,7,5,6)13124 \odot (5, 6, 7, 8) = (5, 7, 5, 6)

Action of 1124311243 on (5,6,7,8)(5, 6, 7, 8)

The permutation 1124311243 acts as follows:

  • 111 \to 1 means the first element remains the same, so the first element stays 5.
  • 212 \to 1 means the second element becomes the first, so the second element becomes 5.
  • 323 \to 2 means the third element becomes the second, so the third element becomes 6.
  • 434 \to 3 means the fourth element becomes the third, so the fourth element becomes 7.

Thus, 1124311243 acting on (5,6,7,8)(5, 6, 7, 8) gives: 11243(5,6,7,8)=(5,5,6,7)11243 \odot (5, 6, 7, 8) = (5, 5, 6, 7)

Step 3: Compute X(5,6,7,8)X \odot (5, 6, 7, 8)

Now, we can subtract the two results since X=1312411243X = 13124 - 11243: X(5,6,7,8)=(5,7,5,6)(5,5,6,7)X \odot (5, 6, 7, 8) = (5, 7, 5, 6) - (5, 5, 6, 7)

Subtracting element-wise: X(5,6,7,8)=(55,75,56,67)=(0,2,1,1)X \odot (5, 6, 7, 8) = (5 - 5, 7 - 5, 5 - 6, 6 - 7) = (0, 2, -1, -1)

Final Answer:

The value of X(5,6,7,8)X \odot (5, 6, 7, 8) is: (0,2,1,1)(0, 2, -1, -1)


Would you like more details or further clarification? Here are some questions that might help expand your understanding:

  1. What is the significance of the group algebra R[S4]R[S_4] in this context?
  2. How is the action of a permutation on a tuple formally defined in terms of group theory?
  3. Could we generalize this result for larger symmetric groups SnS_n?
  4. What are the properties of S4S_4 that make this specific calculation interesting?
  5. How does the group action of symmetric groups apply in fields like representation theory?

Tip: When dealing with permutations, writing out the explicit mappings from positions to values can greatly simplify the process of understanding group actions.

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Math Problem Analysis

Mathematical Concepts

Group Theory
Symmetric Groups
Group Actions
Permutations

Formulas

Group action of symmetric group S_n on M = R^n
Element-wise subtraction of tuples

Theorems

Group Algebra of Symmetric Group
Action of a permutation group on a vector space

Suitable Grade Level

Undergraduate level, abstract algebra