Comp-phys-alps-users

comp-phys-alps-users@lists.phys.ethz.ch

1244 discussions

NONLOCAL parameter in Worm algorithm
by Vipin Varma 16 Sep '11

16 Sep '11

Dear ALPS users/developers, I have a quick question about the NONLOCAL parameter used in the worm algorithm. The ALPS-Wiki mentions it to be a compile time option that one must "undefine to speed up the code for local interactions". However when I run a simulation (linear chain of hardcore bosons with finite chemical potential) for a given chain size with and without this parameter un-defined, the results are quite different. Secondly, the results for the runs with NONLOCAL=0 for different chain sizes are quite comparable to each other (though not exactly equal) and to the exact result for a single-site calculation (again though not exactly equal). I am trying to understand what this parameter does and why the results change when it is set versus unset; any ideas will be appreciated. Thanks, Vipin

2 5

How to set some measurements?
by 赵炜 12 Sep '11

12 Sep '11

Hi ALPS developers and users, I am wandering how can I set to measure the magnetization and susceptibility in using DMFT Hubbard Model. Especially how to set the operator. Thanks for any help. Zhao Wei

2 1

Confusion about the size of lattice.
by 赵炜 12 Sep '11

12 Sep '11

Hi ALPS developers and users, Please forgive my ignorance, but I really cannot find answer. One of the key ideas of DMFT is to replace "other sites" by a "bath" or "effective medium". We have to set a size of the lattice to be replaced, right? Maybe 100x100 or 200x200. But I can not find the lattice size set in the parameter file. Zhao Wei

2 1

Self Energy in DMFT Code
by Hunter Sims 11 Sep '11

11 Sep '11

Dear All, I have written a little DMFT code using the ALPS CTQMC impurity solver. The code accepts an arbitrary Hamiltonian (eventually with the goal of doing some form of LDA+DMFT, currently just a model tight-binding Hamiltonian). Firstly, I was wondering what might be done to address the large amount of noise in the tail of the self energy (after the first 20 or so Matsubara frequencies, the noise is a couple of orders of magnitude larger than the "signal"). I suppose it is not surprising that subtracting the inverses of two small numbers would lead to this sort of thing. Secondly, the type of lattice (a Bethe lattice by default in the ALPS dmft code) seems to enter into the picture via a set of three constants in the Fourier transforms. For the forward transform, these seem to be boundary terms in a numerical integration-by-parts method. They also appear in the backward transform, although it is less clear to me what their function might be. I was also wondering, if it does not exceed the scope of a mailing list query, if there are other places in the provided dmft code in which the Bethe lattice is tacitly assumed. Any help would be greatly appreciated. Regards, Hunter -- Hunter Sims Center for Materials for Information Technology University of Alabama Box 870209 Tuscaloosa AL 35487-0209 205-310-9369

4 13

A lot of＂-nan" and "inf" in output file
by 赵炜 02 Sep '11

02 Sep '11

Dear Matthias, When I ran dmft-02-hybridization in tutorial in python, I found that in G_tau and selfenergy file there is lots of "-nan" and "inf". Is it because of my computer or because I did not install alps right? How can I solve the problem? Sincerely, Zhao Wei(A student from China)

1 0

Re: [ALPS-users] Self Energy in DMFT Code
by Hunter Sims 20 Aug '11

20 Aug '11

Dr. Hafermann, That is incredibly helpful; thanks a lot (and a much belated thank you to Dr. Gull as well for his equally helpful reply and references). -Hunter On Wed, Aug 10, 2011 at 5:00 AM, < comp-phys-alps-users-request(a)lists.phys.ethz.ch> wrote: > Send Comp-phys-alps-users mailing list submissions to > comp-phys-alps-users(a)lists.phys.ethz.ch > > To subscribe or unsubscribe via the World Wide Web, visit > https://lists.phys.ethz.ch/listinfo/comp-phys-alps-users > or, via email, send a message with subject or body 'help' to > comp-phys-alps-users-request(a)lists.phys.ethz.ch > > You can reach the person managing the list at > comp-phys-alps-users-owner(a)lists.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: ALPS 2.0.1 released (Rachele Nerattini) > 2. Problems about running python (??) > 3. Re: Self Energy in DMFT Code (Hartmut Hafermann) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Tue, 9 Aug 2011 15:02:32 +0200 > From: Rachele Nerattini <r.nerattini(a)gmail.com> > Subject: Re: [ALPS-users] ALPS 2.0.1 released > To: comp-phys-alps-users(a)lists.phys.ethz.ch > Message-ID: > <CAAm4ZBp5hwez7Ne6pSPZo9qtjX75DDP5T0gjLEaYofjDq9djeA(a)mail.gmail.com > > > Content-Type: text/plain; charset="iso-8859-1" > > Dear Mr Troyer, > > thank you for the help. I'm going to edit the file and I'll write to you > soon to let you know if the program works properly. > > Thank you again for the help, > best regards > Rachele Nerattini > > > > > > > 2011/8/1 Matthias Troyer <troyer(a)phys.ethz.ch> > > > Here is the patch. I'll add that to the next release. > > > > --- mc/spins/spinmc_factory.C (revision 5665) > > +++ mc/spins/spinmc_factory.C (working copy) > > @@ -139,6 +139,8 @@ > > produceError(parms); > > return 0; > > } > > + else if (parms["MODEL"]=="O(4)") > > + return new SpinSim<ONMoment<4>,MIdMatrix<double,4> > > >(where,parms,node); > > else if (parms["MODEL"]=="Heisenberg") > > switch (maxElemCount) { > > case 1: > > > > > > > > On 14 Jul 2011, at 05:11, Rachele Nerattini wrote: > > > > Dear Mr Troyer, > > > > I've already written to you some months ago to ask you how could I > perform > > a MC classical simulation of the O(4) model. > > I've edited the file spinmc_factory.C as you suggested and typed make > > install to make it work. > > The installation of every packages seemed to be ended well. So I prepared > > the input file with MODEL O(4) but It didn't work. > > It seemed as if the simulation started in the proper way but then it > > stopped with this error: > > > > impossible to perform the simulation, impossible to find the O(4) model > in > > the file > > factory.C > > > > What is this file? Where I can find it and how can I edit it? > > > > Thank you for your help and sorry for my several requests of help. > > > > Best Regards > > Rachele Nerattini > > > > > > > > >

1 0

Problems about running python
by 赵炜 10 Aug '11

10 Aug '11

Dear Matthias or all users community, As is said in the tile, I have a problem about running python. It is that when I type "impot pyalps" and "import pyalps.plot", it appears on the screen that "ImportError: No module named scipy ". And I have no idea about that. Does anyone help,please? Thanks. zhaowei(赵炜）

2 1

ANDES/ALPS School on Numerical Methods for Many-Body Theories
by Matthias Troyer 04 Aug '11

04 Aug '11

Begin forwarded message: > From: "Adrian E. Feiguin" <afeiguin(a)uwyo.edu> > Date: 3 August 2011 17:30:28 MDT > > Dear colleague, > > We would like you to encourage students and young researchers to > participate in the following school on numerical methods to be held in > Bariloche, Argentina, Dec. 2-5 2011 and related conferences: > > ANDES/ALPS School on Numerical Methods for Many-Body Theories Dec. 2-5, 2011 > Bariloche, Argentina > > http://fisica.cab.cnea.gov.ar/mbt16/index.php/ANDES/ALPS_School_on_Numerica… > andhttp://fisica.cab.cnea.gov.ar/mbt16/ > > The deadline is pretty soon: August 5! > > We are attaching the flyer of both events and kindly ask you to please > print it out and hang it up in your group. > > We thank you for your collaboration, > > With best regards, > > > The ANDES/ALPS School Organizing Committee: > Pablo Cornaglia > Adrian Feiguin > Daniel Garcia > Karen Hallberg > Gonzalo Usaj > Web page:http://fisica.cab.cnea.gov.ar/mbt16/ > http://fisica.cab.cnea.gov.ar/mbt16/index.php/ANDES/ALPS_School_on_Numerica… > > Contact:mbt16@cab.cnea.gov.ar > > > > ------------------------------------------------------------------------------------------------------ > ANDES/ALPS School on Numerical Methods for Many-Body Theories > ------------------------------------------------------------------------------------------------------ > Bariloche, Argentina, Dec. 2 to 5, 2011 > > This school is aimed at advanced students in Physics and Chemistry. It > will cover several of the most important numerical methods used in > Many-Body Theories, taught by world leaders in the field. Some partial > support is available for a reduced number of students. There will be > hands-on activities for a practical learning of the computational > tools. > There is no registration fee for this activity. The activities will > take place at the campus of the Centro Atómico Bariloche (located > 9.5km West of the city of Bariloche) and students will be lodged on > campus and at hotels in Bariloche. > > LECTURERS: > Uli Schollwoeck: The Density Matrix Renormalization Group (DMRG) and > Matrix Product States > Adrián Feiguin: Time-dependent Methods > Simon Trebst: Series Expansions > Matthias Troyer: Quantum Monte Carlo > Philip Werner: Impurity Solvers for DMFT and Diagrammatic Monte Carlo Techniques > Antoine Georges, Michel Ferrero and Markus Aichhorn: Realistic > Simulations for Strongly Correlated Materials (DMFT+DFT) > Thomas Pruschke: The Numerical Renormalization Group (NRG) > > Deadlines: > Registration and Reception of Abstracts August 5, 2011 > Acceptance of Contributions August 26, 2011 > Registration fee (early payment) October 1, 2011 > (full support is available for a limited number of students upon request) > > Related conferences: > 1) 16th International Conference on Recent Progress in Many-Body > Theories - RPMBT16 > Bariloche, Argentina, Nov. 28 to Dec. 2 2011 > (http://fisica.cab.cnea.gov.ar/mbt16/) > > 2) New Frontiers in the Physics of Two Dimensional Electron Systems, > Buenos Aires, Nov. 23-25 2011 > (http://wwwtest.magnet.fsu.edu/mediacenter/seminars/icam/) > > -- > Adrian E. Feiguin > Assistant Professor > Dept. of Physics and Astronomy > University of Wyoming > 307-766-6534 > > >

1 0

Re: [ALPS-users] QMC simulation of time-dependent hamiltonian
by Matthias Troyer 03 Aug '11

03 Aug '11

Not for QMC and long times, since the real time evolution gives complex phases in the weights. Matthias On 3 Aug 2011, at 11:16, Dan Thompson wrote: > I think I understand what you mean now. It isn't possible to simulate a dynamic hamiltonian with alps. Ie., a MC time-dependent hamiltonian. > -Dan > > On Wed, Aug 3, 2011 at 1:39 PM, Matthias Troyer <troyer(a)phys.ethz.ch> wrote: > Hi Dan, > > That only makes sense if you are interested in the efficiency of our QMC algorithms. But the annealing time T in this scheme has nothing do to with real time. > > Matthias > > On 3 Aug 2011, at 10:37, Dan Thompson wrote: > >> Hey Matthias, >> >> Thanks for the quick reply. Here's what I'm trying to do with the alps qmc code: >> - Initially, I want to start with a quantum spin 1/2 system in a strong, transverse magnetic field. It should be in the ground state of this particular hamiltonian. >> - Then, the idea is to simulataneously: >> a) turn off the transverse field >> b) turn on a field along the spin axis and >> c) turn on couplings between the various spins. >> This would be the quantum annealing part and should take T MC time. >> - After the annealing, I would measure the new state of the spin system. Namely, I would look at the fidelity of this state and the ground state of the hamiltonian with the couplings and field along the spin axis. >> >> Does that make more sense? The idea would be to measure how the fidelity changes as the annealing time T changes. >> >> Cheers, >> -Dan >> >> >> >> On Wed, Aug 3, 2011 at 12:50 PM, Matthias Troyer <troyer(a)phys.ethz.ch> wrote: >> >> On 3 Aug 2011, at 09:40, Dan Thompson wrote: >> >> > Hello, >> > >> > I was just wondering if there was a way to simulate the quantum annealing of a spin chain/lattice. Namely, adjust the parameters in a model file so that over the course of the quantum monte carlo simulation I could start with one hamiltonian (a simple heisenberg hamiltonian with nearest neighbour couplings and a transverse magnetic field) and finish with a different one (transverse field turned off). >> > >> > Cheers, >> > -Dan >> >> Hi Dan, >> >> What is the purpose of this? Do you want to use it to improve the simulation or to get some time-dependent measurements? The QMC codes only measure equilibrium properties at the given parameters and you can thus just do a series of simulations. Please remember that MC time and real time are not the same. >> >> Matthias >> >> > >

1 0

Re: [ALPS-users] QMC simulation of time-dependent hamiltonian
by Matthias Troyer 03 Aug '11

03 Aug '11

Hi Dan, That only makes sense if you are interested in the efficiency of our QMC algorithms. But the annealing time T in this scheme has nothing do to with real time. Matthias On 3 Aug 2011, at 10:37, Dan Thompson wrote: > Hey Matthias, > > Thanks for the quick reply. Here's what I'm trying to do with the alps qmc code: > - Initially, I want to start with a quantum spin 1/2 system in a strong, transverse magnetic field. It should be in the ground state of this particular hamiltonian. > - Then, the idea is to simulataneously: > a) turn off the transverse field > b) turn on a field along the spin axis and > c) turn on couplings between the various spins. > This would be the quantum annealing part and should take T MC time. > - After the annealing, I would measure the new state of the spin system. Namely, I would look at the fidelity of this state and the ground state of the hamiltonian with the couplings and field along the spin axis. > > Does that make more sense? The idea would be to measure how the fidelity changes as the annealing time T changes. > > Cheers, > -Dan > > > > On Wed, Aug 3, 2011 at 12:50 PM, Matthias Troyer <troyer(a)phys.ethz.ch> wrote: > > On 3 Aug 2011, at 09:40, Dan Thompson wrote: > > > Hello, > > > > I was just wondering if there was a way to simulate the quantum annealing of a spin chain/lattice. Namely, adjust the parameters in a model file so that over the course of the quantum monte carlo simulation I could start with one hamiltonian (a simple heisenberg hamiltonian with nearest neighbour couplings and a transverse magnetic field) and finish with a different one (transverse field turned off). > > > > Cheers, > > -Dan > > Hi Dan, > > What is the purpose of this? Do you want to use it to improve the simulation or to get some time-dependent measurements? The QMC codes only measure equilibrium properties at the given parameters and you can thus just do a series of simulations. Please remember that MC time and real time are not the same. > > Matthias > >

1 0

Jump to page:

2025

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

2008

2007

2006

2005

2004

Comp-phys-alps-users