# [Q]Hamiltonian of many body problem.

1. Nov 23, 2008

### good_phy

Hi

I thought Hamiltonian for two particle system is $H = \frac{-\hbar^2}{2m}\frac{\partial}{\partial x_{1}} + \frac{-\hbar^2}{2m}\frac{\partial}{\partial x_{2}} + v(x)$

But is it right? I just want to know This way is right to construct every hamiltonian of many

body system.

What i want to know more is How can we solve this problem?

I have heard that computational methode can be used after transforming wave equation to

matrix form. Is it right?

Do you have any recommandation practice to improve integral and solve difficult differential

equation ?

2. Nov 23, 2008

### Manchot

First, I should say that the derivatives in your equation should be second derivatives, not first derivatives. Secondly, while you are correct that a general quantum mechanical system has the above form (derivative error aside), there are additional constraints imposed by the types of particles you are considering. If they are indistinguishable, the state of the system must be either symmetric or antisymmetric under exchange of the two particles (depending on whether they are bosons or fermions).

Obviously, if you want to solve the problem computationally, how you go about doing so will vary depending on the form of the potential. For example, if the two particles are weakly coupled, then you can get away with solving the individual particle wavefunctions and perturbatively adding back the coupling term. Or, if one particle is much heavier than the other (e.g., the hydrogen atom), the Born-Oppenheimer approximation would work nicely. In most cases, you won't find a nice closed-form solution, and some approximation is necessary.