Number of distinct base

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Discussion Overview

The discussion centers on the number of distinct bases of a k-dimensional vector space W over a finite field F with q elements, specifically focusing on the case where F has 2 elements and W is a 2-dimensional vector space. Participants explore examples and the application of a formula for calculating distinct bases.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant presents a formula for the number of distinct bases of W, which is (q^k - 1)(q^k - q)(q^k - q^2)...(q^k - q^(k-1)), and applies it to a 2-dimensional vector space over the field with 2 elements, expecting to find 6 distinct bases.
  • Another participant suggests using the Z_2 field and lists the vectors in (Z_2)^2, indicating that any two of the three non-zero vectors can form a basis.
  • A subsequent reply proposes a list of 6 bases but questions the distinctness of some pairs, suggesting that only 4 distinct bases may actually exist.
  • Another participant clarifies that the formula counts ordered bases, implying that the bases in question may be considered distinct due to their order.

Areas of Agreement / Disagreement

Participants express differing views on the distinctness of certain bases, with some arguing that the bases listed are not distinct while others maintain that the order of bases makes them distinct. The discussion remains unresolved regarding the exact number of distinct bases.

Contextual Notes

The discussion highlights potential confusion regarding the distinction between ordered and unordered bases, as well as the implications of the formula presented. There is also an assumption that the bases must be considered in terms of their order.

infinityQ
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Hello, everyone.

I would like to get some concrete examples of the number of distinct bases of k-dimensional vector space W over a finite field F with q elements.

The formula for the number of distinct bases of W is ( p 412 Dummit )
(q^k - 1 )(q^k - q)(q^k - q^2)...(q^k - q ^(k-1) )

I am having a hard time finding an example of F with 2 elements and W be 2-dimensional vector space. According to the formula, 6 distinct bases of W should be acquired.

I will appreciate if anyone shows these 6 distinct bases of W.

Thanks in advance.
 
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take the [tex]Z_2[/tex] field and the vector space [tex](Z_2)^2[/tex] meaning the vectors are { (0,0), (0,1), (1,0), (1,1) }
any two of the three last vectors are a base for the vector space
 
6 distinct bases of W might be

(0,1)(1,0)
(0,1)(1,1)
(1,0)(0,1)
(1,0)(1,1)
(1,1)(0,1)
(1,1)(1,0)

But my question is second one and fifth one, for instance, does not look distinct. So it seems to me just four distinct bases exists for W.

Any suggestion?
 
That formula counts ordered bases and not just any bases. So your second and fifth bases are actually different in this sense.
 

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