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

5 votes

About the Hadamard conjecture

Using the Paley construction I, we obtain Hadamard matrices of size $4, 8, 12, 20, 24, 28, 32, 44, 48, 60, 68, 72, 80, 84, 88$. Using Paley Construction II we add $36=2(17+1)$, $52=2(25+1)$, $76=2(37+ …
Maarten Havinga's user avatar
4 votes
0 answers
140 views

Does an instance of this generalisation of the determinant exist?

Let $n$ be composite, $d$ a divisor greater than $1$ and $m=n/d$. Does anybody know if there is a general mapping $T$ from $n×n$ matrices to $m×m$ matrices that preserves the determinant? Over a field …
Maarten Havinga's user avatar
3 votes
Accepted

On the half-skew-centrosymmetric Hadamard matrices

Let $H_n$ be an $n×n$ Hadamard matrix and $R_n$ the $n×n$ reverse identity matrix. The matrix $X= \begin{pmatrix} H_n & R_nH_n \\ H_n & -R_nH_n \end{pmatrix}$ has entries of length $1$ and $$XX^* = 2n …
Maarten Havinga's user avatar
1 vote

Reshaping data vector into a matrix for deconvolution using a circulant matrix

To circumvent the size difference between $S$ and $v$, one can use JPL codes. These are a XOR (which is modulo $2$ addition) of two or more maximal length sequences of coprime sizes. After 2nd thought …
Maarten Havinga's user avatar