Mathematics

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Jan 14, 2022 17:16
Question: is there an analogue concept of a pseudovector (axial vector) but for matrices?

The motivation is something like this:
A vector field F(r) transforms under a "rotation" g via gF(r) = (gF)(g^{-1}r); a pseudovector does the same, but incorporates an additional factor det(g).
A "matrix field" M(r) transforms similarly like gM(r)g^{-1} = (RM(g^{-1}r)R^{-1}), with R denoting a matrix-representation of g.
Now, if I have a matrix field that has an additional factor of det(g) that then seems very analogous to the pseudovector concept.
 

 The h Bar

General chat for Physics SE (physics.stackexchange.com). For M...
Jul 29, 2019 18:30
Jul 29, 2019 18:29
I'm confused because the Bilbao crystallographic server seems to think otherwise in its KVEC program.
Jul 29, 2019 18:28
Any chance there's any crystallographers or group theorists lurking here: can you confirm that the notion of star{k} is modulo reciprocal lattice vectors {Gi}? Then, if I have a k-vector (G1 + G2 + G3)/2 that vector is equivalent to another vector, say, (-G1 - G2 + G3)/2?
Mar 15, 2019 15:00
@undefined That's wonderful! Thank you!
Mar 15, 2019 14:32
Nearly there then :)
Mar 15, 2019 14:31
Ah, thank you - I appreciate that.
Mar 15, 2019 13:39
(I unfortunately cannot comment on the answer; lack of reputation)
Mar 15, 2019 13:38
In this excellent answer physics.stackexchange.com/a/258135/99418 by @David Bar Moshe, there is a derivation of the non-Abelian Berry curvature from the holonomy/Wilson loop. However, it seems there was a term A_x^2 + A_y^2 dropped in the very last line of the derivation. Anyone know the justification for this?
Feb 1, 2019 19:30
@enumaris Sure, valid point.
Feb 1, 2019 19:29
@enumaris $\sim$ and $\cong$ are used interchangeably for isomorphisms, is that right?
Feb 1, 2019 19:27
@ACuriousMind Okay, too bad. I realized afterwards that another phrasing would be that A is unitarily isomorphic to B? Maybe I will go with something like $\cong_U$
Feb 1, 2019 19:16
Anyone know if there exists any sort of established notation to indicate that two operators, say A and B, are equal, up to an unspecified unitary transformation (i.e. writing something like $A \variant-of-equal-operator B$ if $B = U^\dagger A U$ for $U^{-1} = U^\dagger$)?