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seen May 30 at 20:59

Apr
10
comment complex numbers and 2x2 matrices
Should we not have $a^2+b^2 \ge 0$, because the absolute value of a complex number cannot be smaller than zero?
Apr
9
comment What does it mean to multiply a real matrix by a complex scalar?
I'm confused about the sentence "Multiplication with a fixed complex number is a linear transformation on this two-dimensional vector space". I thought that a complex number itself (not only the multiplication operation) can be represented as a 2x2 matrix, see en.wikipedia.org/wiki/…. Doesn't that mean that the complex numbers are not a vector space, but a matrix space over the real numbers?
Oct
27
comment To “subtract” two matrices with different dimensions in Octave (Matlab)
This works also in Octave 3.4
Oct
27
comment To “subtract” two matrices with different dimensions in Octave (Matlab)
In Octave (3.4) this gives an error: a - b error: operator -: nonconformant arguments (op1 is 4x2, op2 is 1x2)
May
20
comment Does my definition of double complex noncommutative numbers make any sense?
@QiaochuYuan Thank you. "One cannot invent useful things, one can only rediscover them." ;-)
May
20
comment Does my definition of double complex noncommutative numbers make any sense?
Is there a special name for quaternions which have the coefficient of $k$ set to zero? And can't there also be quintions which could then factorize $a^2+b^2+c^2+d^2+e^2$ into two factors ?