# Are conserved the spin and orbital parts of the angular momentum?

1. Jun 10, 2010

### jonjacson

¿Are conserved the spin and orbital parts of the angular momentum?

For example , we have a particle decay into two photons, and you want to see if the angular momentum is conserved:

J(total angular momentum)=S(spin)+L(orbital)

The question is:

-¿only total J is conserved? (and s or l can change)

or

-¿S is conserved and L is conserved also?

Thanks

2. Jun 10, 2010

### haael

Re: ¿Are conserved the spin and orbital parts of the angular momentum?

It's not known. All our theories assume that angular momentum and spin are conserved independently, but they are ready to incorporate the principle, that only the sum of the two values is conserved.

I personally think that spin can transform into orbital angular momentum. This fits nicely into black holes thermodynamics and maybe is necessary for Quantum Gravity.

3. Jun 10, 2010

### jonjacson

Re: ¿Are conserved the spin and orbital parts of the angular momentum?

I didn't know that, so I understand that the answer is yes, s and l are conserved quantities, I suppose that in the exam of nuclear and particle physics the teacher will use this.

Thanks.