On 9 Jan 2009, at 13:05, Cezary Sliwa wrote:
On Tue, Dec 23, 2008 at 12:36:19PM +0100, Matthias Troyer wrote:
On 23 Dec 2008, at 10:14, Cezary Sliwa wrote:
On Sat, Dec 20, 2008 at 10:38:35AM +0800, Matthias Troyer wrote:
What is the error message and what is the code?
I defined a simple model, just one tight-binding orbital with
nearest
neighbors hops on a cubic lattice. With this model I still get the error message about fermionic operators.
Indeed - the QMC codes cannot do fermions
Sorry, what I have written in a previous message is not correct: the problem is with the hopping terms, which are first order in a fermionic operators for a given site. Only the exchange term is expressed in spins. But still, it is second order (a fermion is annihilated at one site and created at another), so that the relation for different bond operators are commutation relations.
Taking this into account, is the difficulty fundamental or just a limitation of your code?
The difficulty is fundamental: there is no general solution for the fermion sign problem.
Matthias