# Pseudoscalars and pseudovectors

1. Jan 18, 2013

### copernicus1

I remember learning that a pseudoscalar is one that changes sign under a parity inversion, like the determinant of a matrix. Pseudoscalar particles have parity eigenvalue -1. Why is it that pseudovector particles have parity value +1?

2. Jan 18, 2013

### fzero

An ordinary vector changes sign under a parity inversion, so a pseudovector must not.

3. Jan 18, 2013

### copernicus1

I think I get it. A pseudovector, after being reflected, is also reversed in direction. A vector is simply reflected.

4. Jan 18, 2013

### D H

Staff Emeritus
Another way to look at it: A polar vector (or true vector) has the component normal to the mirror reversed upon reflection. Pseudovectors don't. Stand in front of a mirror and point straight at your reflection. Your reflection is pointing back at you, opposite the direction you are pointing. Now rotate some object so that the axis of rotation is into the mirror. The axis of rotation reflected image is also into the mirror, unaffected by the reflection.