Dear Michele,

Thanks for your prompt reply.

To be more specific, we would like to apply the algorithm to terms of the form

\sigma_{i}^{+} \sigma_{i+1}^{-} [ \sigma_{i-1}^z + \sigma_{i+2}^z ]

as well as to others of the form

\sigma_{i}^{+} \sigma_{i+1}^{+} [ \sigma_{i-1}^z ( \sigma_{i}^{z} + \sigma_{i+1}^{z}) \sigma_{i+2}^{z} ]

As you can see, these type of terms are rather unusual (but quasi one-dimensional).

Best regards,

Héctor

On 02/26/2014 04:55 PM, Michele Dolfi wrote:

Dear Héctor,

Currently the only way is to define a new model where more sites are fused into one. As you may guess this is not very efficient, and I think is does not scale very well in case of 2d lattices.

We will soon release a new code where such Hamiltonians will be available.

Best regards, Michele

-- ETH Zurich Michele Dolfi Institute for Theoretical Physics HIT G 32.4 Wolfgang-Pauli-Str. 27 8093 Zurich Switzerland

dolfim@phys.ethz.ch www.itp.phys.ethz.ch

+41 44 633 78 56 phone +41 44 633 11 15 fax

On 26-feb-2014, at 20:36, Hector Diego Rosales rosales@fisica.unlp.edu.ar wrote:

...

Dear ALPS users,

I have two questions related with the DMRG method: (i) Does anybody know whether three and four body interactions terms can be readily implemented in the DMRG code ? If so, (ii) is that algorithm suitable for such type of couplings ?

Thanks in advance

-- Dr. Héctor Diego Rosales

CONICET IFLP - Dto. de Física UNLP, Casilla de Correos 67 Calle 49 y 115 s/n, 1900 La Plata, Argentina Tel +54 221 4246062 Fax +54 221 4236335 e-Mail: rosales@fisica.unlp.edu.ar