Anti-matter

[Master of Pain.]

Why it exists:

 

Meh. I started writing this out and I don't think it would have really be understandable to anybody who hasn't gone through the math themselves. Long story short, if you believe in quantum mechanics (ie Schroodinger equation) and special relativity, antimatter has to exist. Basically, when you write down a version of the Scroodinger equation that preserves Lorentz invariance, you find solutions that correspond to antimatter.

 

Why does it annihilate:

This is actually a bit easier to explain. Annihilation is defined as a process in which 2 or more particles with mass interact and the end result is only photons, which are massless. I'll talk a bit about how we think of particle interactions. We start with an initial state and we would like to know what possible final states exist and what the probability of reaching these states are. We know some quantities that must be conserved. The important ones for our problem will include some you are familiar with, momentum, energy, charge and one that you might not know, lepton number.

 

A good question to consider is why don't 2 electrons annihilate. It would always be possible to write down decay modes that conserve energy and momentum that involve an end product of just photons. The problem is, that photons have 0 charge and 0 lepton number (ie they are not leptons). The conservation of charge and lepton number mean that these reactions can't happen. The most common (low energy) interactions with 2 electrons involve 2 electrons initially, they interact via photons, and the final state involves two electrons with different momentums.

 

The most common decay method for low energy positron-electron collisions is an end result of just photons, since they have no mass. Conservation of energy and momentum guarentee that the final state must have two or more particles. The easiest way to see this is to think about the state where initially there is no momentum, ie you are in a frame that is moving with the center of mass of the system. The final state must also have 0 momentum and this is only possible with two or more particles. It is easy to conserve charge and lepton number, since the charge of the initial state is 0 and the lepton number is 0 as well, positrons have lepton number of -1. Since a decay into 2 photons is not disallowed, it happens, and it happens often.

 

[For simplification, I ignored angular momentum, which when taken into account, make interactions which involve 3 or more photons at the end more likely.]

 

So, that's my theory about anti-matter.

Anyone here feel free to share ideas and discuss the theories about anti-matter.

 

 

[leik oh em jeez!]

Anti-matter has an opposite charge of matter. (Protons - charge, electrons + charge)

[Struff Bunstridge]

I don't think you'll find too many people here with as in-depth a knowledge of the physics involved as you appear to. I have a basic working knowledge of things like quantum mechanics and relativity, that sort of thing, but nothing I'd be able to use in an involved discussion or anything. It stems more from an interest in the paradoxes behind, for example, Schrodinger's theorems, and the fact that Einstein always used trains to analogise his ideas. No-one had a f*cking clue about the maths, but everyone knows trains.

[Stefan.]

I'm with Struff on this one; I haven't studied Physics that in depth before, however from what I understand I think that the particles would simply be split-up into miniscule, tiny particles with an incredibly small mass, so small that it is considered obsolete. I'm most likely wrong, but hey, I've only done very basic physics.