Determinant of matrix with Aij = min(i, j)

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    Determinant Matrix
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Discussion Overview

The discussion centers on the determinant of a specific n x n matrix defined by the entries Aij = min(i, j). Participants explore methods to prove that the determinant of such matrices is 1, including the use of induction and row operations.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Exploratory

Main Points Raised

  • One participant claims that the determinant of the matrix is 1 and seeks a proof, mentioning an attempt at induction.
  • Another participant suggests subtracting the line immediately above from each line to simplify the matrix.
  • A participant presents a transformed matrix and questions how to prove that it has the same determinant as the original matrix.
  • Another participant confirms that the transformation maintains the determinant, citing that subtracting a line is an elementary row operation that preserves the determinant.

Areas of Agreement / Disagreement

Participants generally agree on the method of using row operations to simplify the matrix, but the overall proof of the determinant being 1 remains unresolved.

Contextual Notes

The discussion does not resolve the assumptions or steps required to complete the proof of the determinant's value, leaving some mathematical steps and justifications unclear.

nedf
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Given a n x n matrix whose (i,j)-th entry is i or j, whichever smaller, eg.
[1, 1, 1, 1]
[1, 2, 2, 2]
[1, 2, 3, 3]
[1, 2, 3, 4]
The determinant of any such matrix is 1.
How do I prove this? Tried induction but the assumption would only help me to compute the term for Ann mirror.
 
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From each line subtract the line immediately above it.
 
I will get this?
[1 1 1 1]
[0 1 1 1]
[0 0 1 1]
[0 0 0 1]
How do I prove that this matrix has same determinant as the original one?
 
nedf said:
I will get this?
[1 1 1 1]
[0 1 1 1]
[0 0 1 1]
[0 0 0 1]
Yes.

nedf said:
How do I prove that this matrix has same determinant as the original one?
Subtracting another line is one of the elementary row operations and is known to preserve the determinant.
 

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