DMRG sweep

Density Matrix Renormalization Group

Introduction As promised in the Numerical Renormalization Group post, I implemented a Density Matrix Renormalization Group program. As I start writing this post, the program is already on GitHub1. It’s quite basic, currently it is implemented only for Heisenberg model chains, for both spin 1/2 and 1. It runs only for even number of sites … Read more

CO2 molecule

The Hartree-Fock program

Introduction After some posts about the theory it is time to present the Hartree-Fock program1. You might find the previous posts useful, along with the links in there: How to solve a quantum many-body problem, The Hartree-Fock method. Here is the program in action (the final version might have minor differences): Although it doesn’t show … Read more

The Hartree-Fock method

Introduction Last time we ended up with a simplified Hamiltonian: and having the variational principle for help. It turns out that this simplified Hamiltonian is not simple enough. In this post I’ll expose one method that allows one to do calculations for quite complex quantum systems, the Hartree-Fock method. Because the subject is quite large, … Read more

How to solve a quantum many body problem

Introduction Quite a bit of time passed since my last post on this blog. I had a visit to the sunny Spain, I switched to a double-surface hang glider and I had to take a little care of my firm. Despite those things, I did a little bit of work for the blog, but it … Read more

The Numerical Renormalization Group

Introduction Finally here1 it is. A simple (relatively) program implementing the Numerical Renormalization Group. I tried to implement it as simple as possible to be easy to understand. Here is the program in action, running an Anderson model at half-filling: I already used charts generated by the program in The Kondo Effect and Renormalization Groups … Read more