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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

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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

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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

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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

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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

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Plot files
by Niall Moran 27 Sep '07

27 Sep '07

Hi, I am having some issues with the xml plot files. I want to generate a graph of susceptibility vs. magnetic field (gamma) for each of the lengths (L) used and each temperature (T). All the results from the simulations have been placed in the sqlite achive files results.db. The plot file I am trying to use is <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plot SYSTEM "conf/plot.dtd"> <plot name="Susceptibility versus Magnetic Field" output="xmgr"> <for-each name="L" > <for-each name="T" > <xaxis name="Gamma" type="parameter" /> <yaxis name="Susceptibility" type="mean" error="true" /> </for-each> </for-each> </plot> However when I try to use this with the command archive --verbose --command=plot --db-file=results.db --plot-file=plot_example.xml --output-path=. I get the following The Plotfile does not match the DTD! Fails parsing at: for-each name="L" > <for-each name="T" > <xaxis name="Gamma" type="parameter" /> <yaxis name="Susceptibility" type="mean" error="true" /> </for-each> </for-each> </plot> By taking out the second for-each tag and using <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plot SYSTEM "conf/plot.dtd"> <plot name="Susceptibility versus Magnetic Field" output="xmgr"> <for-each name="L" > <xaxis name="Gamma" type="parameter" /> <yaxis name="Susceptibility" type="mean" error="true" /> </for-each> </plot> it works but the graph does not make sense. I have also tried adding a constraint to pick out one particular temperature. <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plot SYSTEM "conf/plot.dtd"> <plot name="Susceptibility versus Magnetic Field" output="xmgr"> <for-each name="L" > <xaxis name="Gamma" type="parameter" /> <yaxis name="Susceptibility" type="mean" error="true" /> <constraint name="T" condition="=0.1" /> </for-each> </plot> This leads to the same error and says parsing fails at the same point. I am using ALPS 1.3b6. Any help is greatly appreciated. Regards, Niall.

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Quantum Ising Model
by Niall Moran 21 Sep '07

21 Sep '07

Hi all, I am trying to do some quantum Monte Carlo simulations on a simple 1D Ising model with a transverse field. I could not find any Ising model specified in the standard models.xml file. I created a file called ising_model.xml with contents listed below. Could anyone verify if this is correct as I am new to this and do not fully understand how to specify models. Kind Regards, Niall. <MODELS> <SITEBASIS name="spin"> <PARAMETER name="local_spin" default="local_S"/> <PARAMETER name="local_S" default="1/2"/> <QUANTUMNUMBER name="S" min="local_spin" max="local_spin"/> <QUANTUMNUMBER name="Sz" min="-S" max="S"/> <OPERATOR name="Splus" matrixelement="sqrt(S*(S+1)-Sz*(Sz+1))"> <CHANGE quantumnumber="Sz" change="1"/> </OPERATOR> <OPERATOR name="Sminus" matrixelement="sqrt(S*(S+1)-Sz*(Sz-1))"> <CHANGE quantumnumber="Sz" change="-1"/> </OPERATOR> <OPERATOR name="Sz" matrixelement="Sz"/> </SITEBASIS> <BASIS name="spin"> <SITEBASIS ref="spin"> <PARAMETER name="local_spin" value="local_S#"/> <PARAMETER name="local_S#" value="local_S"/> <PARAMETER name="local_S" value="1/2"/> </SITEBASIS> <CONSTRAINT quantumnumber="Sz" value="Sz_total"/> </BASIS> <SITEOPERATOR name="Sx" site="x"> 1/2*(Splus(x)+Sminus(x)) </SITEOPERATOR> <HAMILTONIAN name="ising_spin"> <PARAMETER name="h" default="0"/> <BASIS ref="spin"/> <SITETERM site="i"> <PARAMETER name="h" default="h"/> -h*Sx(i) </SITETERM> <BONDTERM source="i" target="j"> <PARAMETER name="J" default="J"/> -J*Sz(i)*Sz(j) </BONDTERM> </HAMILTONIAN> </MODELS>

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Re: [ALPS-users] Comp-phys-alps-users Digest, Vol 18, Issue 8
by GANG CHEN 20 Sep '07

20 Sep '07

comp-phys-alps-users-request(a)phys.ethz.ch wrote: >Send Comp-phys-alps-users mailing list submissions to > comp-phys-alps-users(a)phys.ethz.ch > >To subscribe or unsubscribe via the World Wide Web, visit > https://webmail.phys.ethz.ch/mailman/listinfo/comp-phys-alps-users >or, via email, send a message with subject or body 'help' to > comp-phys-alps-users-request(a)phys.ethz.ch > >You can reach the person managing the list at > comp-phys-alps-users-owner(a)phys.ethz.ch > >When replying, please edit your Subject line so it is more specific >than "Re: Contents of Comp-phys-alps-users digest..." > > >Today's Topics: > > 1. Re: models in classical monte carlo simulation (Matthias Troyer) > 2. Re: one question about custom measurement (Matthias Troyer) > > >---------------------------------------------------------------------- > >Message: 1 >Date: Wed, 19 Sep 2007 19:41:41 +0200 >From: Matthias Troyer <troyer(a)phys.ethz.ch> >Subject: Re: [ALPS-users] models in classical monte carlo simulation >To: comp-phys-alps-users(a)phys.ethz.ch >Message-ID: <7E292C25-4D1A-4234-82E4-BF3733ED4046(a)phys.ethz.ch> >Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed > >Hi Gang, > >The classical models cannot be as easily coded in an input file as >the discrete quantum models. We have support for classical O(N) >vector spin models with anisotropic interactions hardcoded. Which >model do you have in mind? > >Matthias > >On 19 Sep 2007, at 06:16, GANG CHEN wrote: > > > Thanks, the model is O(3) Heisenberg model with Dzyaloshinskii-Moriya anisotropy. e.g. if there are two bonds in the unit cell, each bond has different Dzyaloshinskii-Moriya vector, is it possible to deal with model? What will be the name for it in the hardcoded library? Gang >>Hi all, >> >>What is the default libary for the model in classical monte carlo >>simulation? In the tutorial there are Heisenberg model and Ising >>model which could not be found in the file lib/xml/models.xml. >>Could I define my own models as usual way? And do I refer the model >>libary in the parameter file also in the same way as >>sparsediagonalization? >> >>Thanks, >>Gang >><chggst.vcf> >> >> > > > >------------------------------ > >Message: 2 >Date: Wed, 19 Sep 2007 19:42:04 +0200 >From: Matthias Troyer <troyer(a)phys.ethz.ch> >Subject: Re: [ALPS-users] one question about custom measurement >To: comp-phys-alps-users(a)phys.ethz.ch >Message-ID: <DDDC6596-1617-436A-A232-A5E7FAB77BE9(a)phys.ethz.ch> >Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed > >You will need to code those yourself manually. We do not support such >multi-site measurements yet, but will in a future version. > >Matthias > >On 19 Sep 2007, at 02:02, GANG CHEN wrote: > > > >>Hi all, >> >>I am working on a lattice which has several sites in one unit cell. >>Let's denote site index as "i, j ,k", unit cell index as "A, B, C". >>If I want to see the behavior of some particular site in the unit >>cell, e.g. S_{A, i}; or some other local information, such as Cross >>[S_{A, i}, S_{A,j}] \dot S_{A, k}, i,j,k are three given sites in >>one unit cell, how do I define them? >> >>Thanks, >>Gang >> >><chggst.vcf> >> >> > > > >End of Comp-phys-alps-users Digest, Vol 18, Issue 8 >*************************************************** > >

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one question about custom measurement
by GANG CHEN 19 Sep '07

19 Sep '07

Hi all, I am working on a lattice which has several sites in one unit cell. Let's denote site index as "i, j ,k", unit cell index as "A, B, C". If I want to see the behavior of some particular site in the unit cell, e.g. S_{A, i}; or some other local information, such as Cross[S_{A, i}, S_{A,j}] \dot S_{A, k}, i,j,k are three given sites in one unit cell, how do I define them? Thanks, Gang

2 1

models in classical monte carlo simulation
by GANG CHEN 19 Sep '07

19 Sep '07

Hi all, What is the default libary for the model in classical monte carlo simulation? In the tutorial there are Heisenberg model and Ising model which could not be found in the file lib/xml/models.xml. Could I define my own models as usual way? And do I refer the model libary in the parameter file also in the same way as sparsediagonalization? Thanks, Gang

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