Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options not deleted user 46140

Questions about the properties of vector spaces and linear transformations, including linear systems in general.

9 votes
Accepted

Efficiently computing $\prod_{i=1}^{n} A_i$

To be unambiguous about the order of multiplication, let $B(n) = A_1 A_2 \cdots A_n$. We have the D-finite recurrences $B(n)_{r,1} = (\frac{n}{n-1})^k B(n-1)_{r,1} + n^k B(n-2)_{r,1}$ $B(n)_{r,2} = B …
Peter Taylor's user avatar
  • 7,226
5 votes
Accepted

Guess the next polynoms in the sequence (MO vs. AI :), count anticommuting $F_p$-matrices, P...

It's not entirely clear to me how much data your guesses are based on, so I present a table with calculated data and guessed polynomials based on that data and the assumption that $f(1) = f(-1) = 1$. …
Peter Taylor's user avatar
  • 7,226
1 vote

Recurrence relation with two variables

The solutions look like a mess, so it's not too surprising that you always end up with one. If we follow Iosif Pinelis in dividing all by the last constraint by $\lambda$ and substituting $r = \frac{1 …
Peter Taylor's user avatar
  • 7,226
5 votes

Matrices over $\mathbb{F}_p$ that have nonzero determinant under any element permutation

$\det \begin{pmatrix} 1 \end{pmatrix} = 1$ works for any $p$. $\det \begin{pmatrix} 0 & 1 \\ 1 & 1 \end{pmatrix} = -1$ similarly. For $n=3$ we require $p \ge 5$. By exhaustion there's no solution for …
Peter Taylor's user avatar
  • 7,226
2 votes
Accepted

Inflection point calculation for cubic Bézier curve encounters division by zero

You're trying to solve $$(3a_xt^2 + 2b_xt + c_x)(6a_yt + 2b_y) - (6a_xt + 2b_x)(3a_yt^2 + 2b_yt + c_y) = 0$$ Expanded out, $$6(a_y b_x - a_x b_y) t^2 + 6(a_y c_x - a_x c_y)t + 2(b_y c_x - b_x c_y) = 0 …
Peter Taylor's user avatar
  • 7,226
2 votes

Non-singular matrix with restricted entries

Disclaimer: this is only a partial answer. If $S = \{x, y\}$ (considered as variables), the determinant must be a polynomial with integer coefficients and constant coefficient 1. Therefore by Gauss's …
Peter Taylor's user avatar
  • 7,226
4 votes

Sum of divisors and LCM in determinants

This is only empirical observation, but I was requested to post it as an answer rather than merely a comment. Define $b(n) = \frac{\det(A_n)}{n! \, \sigma(\operatorname{lcm}(1,\ldots,n))}$ for $n \ge …
Peter Taylor's user avatar
  • 7,226
3 votes

Vandermonde $V_n$ mod $n$

OP asked me to fill in the details of my comment, and in attempting to do so I realised that I claimed too much. However, a very similar argument proves a weaker result which is strong enough to suppo …
Peter Taylor's user avatar
  • 7,226