On Oct 20, 2006, at 4:20 AM, Pearl Louis wrote:

Hi,

In one of the presentations that are available on the ALPS webpage, the <INHOMOGENEOUS> tag is mentioned. As I was going through the doc folder on the ALPS installion I see the mention of a <DISORDER> tag as well. However, besides these instances I cannot seem to find any information on how to actually use these tags when defining different lattices e.g. syntax and then how to implement site dependent hamiltonians. I was wondering if there are any examples about how to use these tags?

The tag has been renamed from <DISORDER> to <INHOMOGENEOUS> in the recent versions of the code. Look at the "inhomogeneous square lattice" in lattices.xml for an example. The purpose of this tag is to do models with site-dependent interaction terms, e.g. a chemical potential that is site dependent. The prime example are bosons in a harmonic trap for which one would use a potential such as

mu = (x-L/2)^2 + (y-W/2)^2

in two dimensions. When site-inhomogeneities are specified then the potential is evaluated explicitly for each site, and x, y, and z have the values of the coordinates at that site.

It could also be used for random couplings, since there are random() functions available, but we have not used that extensively yet.

I hope this helps.

Matthias