October 2007 - Comp-phys-alps-users

DMRG question
by Justin David Peel 11 Dec '07

11 Dec '07

Hi all, I just have a quick question. How can I get the dmrg program to output the max truncation error during the final sweep (or any truncation error for that matter) to the output file? I know that it is output to the screen, but I would like it in the output file. Thanks, Justin

2 1

dmrg tutorial example is not running
by Aniket Kulkarni 03 Nov '07

03 Nov '07

Hi all, I am trying to run dmrg tutorial example but it is showing error. The error is as follows: $ simple_dmrg <parm1 error: ALPS noninteractiong DMRG application version 1.0 available from http://alps.comp-phys.org/ copyright (c) 2003-2004 by Salvatore R. Manmana <Salva(a)theo3.physik.uni-stuttg art.de> Reinhard M. Noack <Reinhard.Noack(a)physik.uni-marbur g.de> Ian McCulloch <ianmcc(a)physik.rwth-aachen.de> for details see the publication: F. Alet et al., Report cond-mat/0410407. EXCEPTION: bad lexical cast: source type value could not be interpreted as target t Please see the error and tell me the problem. Thanks in advance with regards, Aniket

2 2

basis set
by Aniket Kulkarni 29 Oct '07

29 Oct '07

hi all, Which basis set is used for QMC calculation in ALPS? thanks, Aniket

2 1

Cannot convert fermionic operator to a bosonic matrix
by Aniket Kulkarni 20 Oct '07

20 Oct '07

Dear all, I am new user to alps. I want to calculate magnetic susceptibility for the square model(4 * 4) using Hamiltonian fermion Hubbard. For this I am using looper and dirloop_sse algorithm. But it is not running at all. It is showing following error Cannot convert fermionic operator to a bosonic matrix So please tell me how to calculate? Thanks in advance with regards, Aniket

2 1

Single site DMRG
by Justin David Peel 12 Oct '07

12 Oct '07

Hi, Thanks for the answer about the truncation error. I felt kind of dumb that I hadn't thought of that before, but I don't use unix all that often. I just read through Steven White's 2005 paper "Density matrix renormalization group algorithms with a single center site." I was looking through the dmrg code trying to figure out how to implement the single site method. I was wondering what the general consensus is about this method before I continue trying to implement it. Here is my goal: I would like to try to find the Haldane gap in S=1 Heisenberg ladders. I know that the accepted method for doing this in 1D is to make the ends of the chain be S=1/2 to avoid the end effects. Will this work in ladders as well? I was thinking that the single site method would just allow me to use periodic boundary conditions and avoid the end site problems. I also don't know how to put S=1/2 sites at the ends of the lattice in ALPS. Does anyone know how to do this? Can I just set local_S for each site of the lattice? Thanks, Justin

2 1

uniform susceptibility
by GANG CHEN 02 Oct '07

02 Oct '07

Hello, all I use "fulldiag" to diagonalize my hamiltonian. Because in my problem Sz is not a conserved quantum number, so when I try to use "fulldiag_evaluate" to treat my output xml file, I cannot get uniform_susceptibility file. In order to get the uniform_susceptibility curve, I can probably introduce magnetic field, and change the magnitude of magnetic field, measure the magnetization, see how M changes with h, and use \Delta{M} / \Delta{h} to find chi. Besides this tedious way, is there any other thing I can try in ALPS? Thanks, Gang

2 1

question about light version
by GANG CHEN 02 Oct '07

02 Oct '07

Hello all, sorry to bother. Can some one explain the difference between ALPS of light version and full version? Since I am only working with exact diagonalizatin (fulldiag or sparsediag), is the light version one able to do the job? Thanks, gang

2 1