Just wondering about the structure of a determinant

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    Determinant Structure
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Discussion Overview

The discussion revolves around the informational content of a determinant in relation to the entries of a matrix, its size, symmetry, and specific cofactors. Participants explore how much can be inferred from the determinant alone and the implications of additional matrix properties.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions the extent to which a determinant reveals information about a matrix, considering factors such as matrix size and symmetry.
  • Another participant argues that a determinant significantly reduces the information of an n by n matrix to a single value, indicating that much information is lost, except for determining invertibility.
  • A different viewpoint states that the determinant represents the factor by which volumes are scaled in the context of linear transformations, suggesting a specific geometric interpretation.
  • Another contribution mentions that in complex vector spaces, the determinant corresponds to the product of the eigenvalues, which may or may not be useful, and notes the relationship between the trace and eigenvalues.

Areas of Agreement / Disagreement

Participants express differing views on the utility of the determinant, with some emphasizing its limitations and others highlighting specific contexts where it may provide useful information. The discussion does not reach a consensus on the overall value of the determinant in conveying information about a matrix.

Contextual Notes

Participants do not fully explore the implications of matrix properties such as symmetry or specific cofactors, leaving these aspects somewhat unresolved in the context of the discussion.

Dosmascerveza
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Just wondering about the "structure" of a determinant...

How much can a determinant tell you about the entries of a matrix? How much more if you know the size of the aforementioned matrix? How much more if you know that the matrix is symmetric?(perhaps a silly question). How much more if you know the cofactors across the ith row or jth column?
 
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Very little. An n by n matrix contains [itex]n^2[/itex] entries and taking the determinant reduces all that information to one number. You will have lost an immense amount of information that you cannot get back just knowing the determinant.

The one thing you can be sure about, just by knowing the determinant of a matrix, is whether it is invertible or not.
 


The determinant is the factor by which volumes are multiplied under the linear transformation that the matrix represents. That is all it tells you.
 


In a complex vector space the determinant is just the product of the eigenvalues. Sometimes that is helpful, often times not. Likewise, the fact that the trace of a matrix is the sum of the eigenvalues is also sometimes of use.
 

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