# What is parity

1. Mar 27, 2006

### sneez

Could you help me to get some sensible definition of parity? In my book they talk about having negative reversing coordinates and stuff.

What does it physically mean to reverse coordinates?

Any understandable definition of parity?

thank you vr mch.

2. Mar 28, 2006

### Perturbation

A discrete symmetry operator that changes the sign of the momentum.

$$Pa_{\mathbf{p}}P^{-1}=a_{-\mathbf{p}}$$

Here a is an anihilation operator (it works on any Hilbert space operator responsible for the creation/anihilation of four-momentum).

Which is the same as flipping the coordiante axes, so that the positive spatial axes become the negative and visa versa.

There are two other very important discrete symmetries: charge conjugation and time reversal.

Last edited: Mar 28, 2006
3. Mar 29, 2006

### rammstein

Parity is actually an inborn quality that is attatched with the particle when it is born, just like mass and charge. Well, now reversing the coordinates means a reflection across the origin. Now, u might ask wat does reflection across the origin mean? it is reversing the signs of ur coordinates. for eg ur particle is on (1,1,1). Reversing means (-1,-1,-1). Did u get that? Now consider ur particle as a Bohr wave. ok. So it must have some wave function defining its motion. Ok. if there is a sign change in the wave function when u reverse the space, it means it has odd parity. And if the sign doesnt change, it means it has even parity. Getting used to this term will require a lot of reading.

4. Mar 31, 2006

### sneez

thank you ram.

Does it than violate "law" that laws of physics should be independent of reference frame? You are telling me that different reference frame will have different properties?