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1248 discussions

Sparse Diagonalization
by Sriluckshmy Viswanathan 18 Jun '14

18 Jun '14

Hi, I had a query regarding sparse diagonalization in ALPS. The system that I am working with is heisenberg model on honeycomb lattice with pbc. I have taken 3 x 3 units which amounts to 12 lattice sites. I did a brute force diagonalization using matlab and a sparsediag of ALPS and am comparing the results. In matlab if I just look at the low lying energy i get 1 ground state 3 first excited states and 5 second excited states with gap of 2.27 and 4.61 between them respectively. Using ALPS sparsediag i get in the k = [0,0], i get an eigenvalue -6.75 and in the other momentum sectors an eigenvalue -5.75 where the energy gap is printed to be 1. My main concern is why aren't the two results matching qualitatively. I understand that one shouldn't compare the exact numbers but the "degeneracy" property should be the same i am guessing. The eigenvalue that is printed is the ground state energy of that momentum sector. Is this correct? If this is then the energy gap which is being measured from the difference in the ground state energy of the two low lying sectors seems incorrect right. Because the energy gap should be measured after sorting the eigenvalues of all the sectors and then measured isnt it. Could this be the reason why the results are not matching? Is there a way to get qualitatively get results that I get with Matlab? I tried fulldiag of this system and got a std::bad_alloc which i am guessing that its because of memory. Is there a way to handle this? Any help will be appreciated. Thanks and Regards Sriluckshmy

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Re: [ALPS-users] alternative fermion Hubbard (Fernando Iemini)
by Fernando Iemini 16 Jun '14

16 Jun '14

dear all, thanks for the responses, and sorry for the delay to reply. Yes, i was using the dmrg, and in fact using this new dmrg application `mps_optim`, as suggested by Michele Dolfi, solved my problem! I didn't know about this application, is there somewhere i can find a tutorial about it, or is it exactly the same input's as dmrg? And just a last point, in this application can i measure some "four-point" correlations, like "cdag_m:c_{m+1}:cdag_n:c_{n+1}" ? best regards, Fernando. ----------------------------------- Date: Thu, 12 Jun 2014 08:52:52 +0200 From: Michele Dolfi <dolfim(a)phys.ethz.ch> To: comp-phys-alps-users(a)lists.phys.ethz.ch Subject: Re: [ALPS-users] alternative fermion Hubbard Message-ID: <52E3FD2A-60E3-4D48-8315-1ACDF7348498(a)phys.ethz.ch> Content-Type: text/plain; charset="us-ascii" Hi Fernando, If you are using a recent version of ALPS, e.g. 2.2.0b3, you can use the new dmrg application `mps_optim`. It works the same way as the `dmrg` application, but additionally allows you to measure correlation functions for i<j, which very often is good enough. MEASURE_HALF_CORRELATIONS[ cdag_up c_up]="cdag_up:c_up" Best regards, Michele -- ETH Zurich Michele Dolfi Institute for Theoretical Physics HIT G 32.4 Wolfgang-Pauli-Str. 27 8093 Zurich Switzerland dolfim(a)phys.ethz.ch www.itp.phys.ethz.ch +41 44 633 78 56 phone +41 44 633 11 15 fax On Jun 12, 2014, at 2:08 AM, Ryo IGARASHI <rigarash(a)issp.u-tokyo.ac.jp> wrote: > Hi, Fernando, > > Assuming that you use DMRG simulation since you specify 'MAXSTATES'. > > > (2014/06/12 0:10), Fernando Iemini wrote: >> I've using the ''alternative fermion Hubbard'' model, with open boundary >> conditions, and analyzing its single-particle correlations, <cdag_up:c_up>. >> I'm not being able however to compute these observables for larger >> lattices, e.g., L=~160. I'm getting a "segmentation fault" message, does >> anybody know why is happening this error, maybe due to memory? If so, what >> would be good parameters in order to avoid it? >> >> Here is the script i'm using: >> >> LATTICE="open chain lattice" >> MODEL="alternative fermion Hubbard" >> CONSERVED_QUANTUMNUMBERS="N,Sz,Nup,Ndown" >> N_total=160 >> Sz_total=0 >> Nup_total=80 >> Ndown_total=80 >> mu=0 >> t=1 >> NUMBER_EIGENVALUES=1 >> L=160 >> MAXSTATES=100 >> MEASURE_CORRELATIONS[cdag_up c_up]="cdag_up:c_up" >> {U = 9.000000e-01,V=5.500000e-01,TRUNCATION_ERROR=1e-7} > > This is memory issue. The problem is that 'MEASURE_CORRELATIONS' > collects all pair sites. Observing ~10000 measurements costs too much > memory. > > Not tested, but I believe that you can avoid this issue by tweaking > models.xml and lattices.xml. Change the name of some specific operator > and just calculating between them. > > -- > Ryo IGARASHI, Ph.D. > rigarash(a)issp.u-tokyo.ac.jp > tel: 04-7136-5343, fax: 04-7136-3441 > OpenPGP fingerprint: BAD9 71E3 28F3 8952 5640 6A53 EC79 A280 6A19 2319 >

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PROBLEM WITH INSTALLATION OF ALPS
by emmanuel enukpere 16 Jun '14

16 Jun '14

I am trying to install and test alps on Ubuntu 12.04 32-bit system. Things went pretty fine until it got the point where it wanted to install the project , then it reported that “file cannot create directory /opt/alps/include. Maybe need administrative privileges. ” What should I do? Please help as I do not know how to proceed. Details of the last few steps before the error warning are shown below: [ 99%] Built target accumulate_if [ 99%] Built target vector_functions [100%] Built target vector_valarray_conversion Install the project... -- Install configuration: "Release" CMake Error at cmake_install.cmake:36 (FILE): file cannot create directory: /opt/alps/include. Maybe need administrative privileges. make: *** [install] Error 1 enukpere@ubuntu:~/alps-2.1.1-r6176-src-with-boost/build$ sudo cmake_install.cmake [sudo] password for enukpere: sudo: cmake_install.cmake: command not found Enukpere,E.E. Physics Department, University of Benin, Benin City, Nigeria.

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Alps Maximum Entropy Method
by Soumen Bag 16 Jun '14

16 Jun '14

Hi! I am using Alps library for my project. I need to use MEM of alps. But i did not find any tutorial for this. Can anyone please let me how to use ALPS's MEM? Thanks, *Soumen Kumar Bag* *Physical Science Dept.* *IISC*

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Accuracy of sparsediag
by epquinn＠pks.mpg.de 12 Jun '14

12 Jun '14

Greetings, I am wondering if it is possible to increase the accuracy of sparsediag, for example for the result it gives for the lowest eigenvalue. There does not appear to be a suitable input parameter. My understanding is that increasing accuracy comes at a computational cost, and I need to tweak the balance further to the side of accuracy. With best regards, Eoin

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alternative fermion Hubbard
by Fernando Iemini 12 Jun '14

12 Jun '14

dearl all, I've using the ''alternative fermion Hubbard'' model, with open boundary conditions, and analyzing its single-particle correlations, <cdag_up:c_up>. I'm not being able however to compute these observables for larger lattices, e.g., L=~160. I'm getting a "segmentation fault" message, does anybody know why is happening this error, maybe due to memory? If so, what would be good parameters in order to avoid it? Here is the script i'm using: LATTICE="open chain lattice" MODEL="alternative fermion Hubbard" CONSERVED_QUANTUMNUMBERS="N,Sz,Nup,Ndown" N_total=160 Sz_total=0 Nup_total=80 Ndown_total=80 mu=0 t=1 NUMBER_EIGENVALUES=1 L=160 MAXSTATES=100 MEASURE_CORRELATIONS[cdag_up c_up]="cdag_up:c_up" {U = 9.000000e-01,V=5.500000e-01,TRUNCATION_ERROR=1e-7} regards, Fernando.

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Unconventional hopping
by vitbka konef 05 Jun '14

05 Jun '14

Hi all, Thanks for the help. I did it, in some way! With best regards.

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Re: [ALPS-users] Comp-phys-alps-users Digest, Vol 98, Issue 6
by bondnina 01 Jun '14

01 Jun '14

Dear Michele. Thank you for your very detailed answer. I have one more question. I am afraid that the approaches you have listed in your male have only static nature. Maybe I am wrong but I didn't get how to apply t parameter depending on time. That maybe useful to simulate chain dynamics for example. Best, Nina ---------- Forwarded message ---------- From: <comp-phys-alps-users-request(a)lists.phys.ethz.ch> Date: 29 May 2014 12:00 Subject: Comp-phys-alps-users Digest, Vol 98, Issue 6 To: comp-phys-alps-users(a)lists.phys.ethz.ch 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. Exploiting degeneracy in Hybridization impurity solver (backes(a)th.physik.uni-frankfurt.de) 2. Re: Exploiting degeneracy in Hybridization impurity solver (august(a)fzu.cz) 3. Re: Variational hopping parameter (Michele Dolfi) ---------------------------------------------------------------------- Message: 1 Date: Wed, 28 May 2014 12:40:54 +0200 From: backes(a)th.physik.uni-frankfurt.de To: comp-phys-alps-users(a)lists.phys.ethz.ch Subject: [ALPS-users] Exploiting degeneracy in Hybridization impurity solver Message-ID: < c3a4761d76660198b749e13b652541aa.squirrel(a)th.physik.uni-frankfurt.de> Content-Type: text/plain;charset=utf-8 Dear Alps developers, is it possible to add an option for specifying and exploiting the degeneracy of some orbitals in the Hybridization expansion solver? E.g. for a paramagnetic calculation, where only half of the orbitals need to be measured (the input Hybridization function and interaction parameters are identical for these orbitals). best regards, Steffen Backes ------------------------------ Message: 2 Date: Wed, 28 May 2014 14:57:49 +0200 From: august(a)fzu.cz To: comp-phys-alps-users(a)lists.phys.ethz.ch Subject: Re: [ALPS-users] Exploiting degeneracy in Hybridization impurity solver Message-ID: <63da888d9fd14d678d4270331e2a4696.squirrel(a)gate.fzu.cz> Content-Type: text/plain;charset=utf-8 Hi Steffen, Do you want just symmetrize the results for equivalent orbitals at the end of your calculation or really measure only on of the equivalent G. functions and ignore the rest? If I understand correctly, you dont gain anything by not measuring say down-spin orbitals in a paramagnetic system since the spin equivalence is broken during the simulation. Full measurement is therefore slower but leads to a better statistics. Best regards, Pavel > Dear Alps developers, > > is it possible to add an option for specifying and exploiting the > degeneracy of some orbitals in the Hybridization expansion solver? E.g. > for a paramagnetic calculation, where only half of the orbitals need to be > measured (the input Hybridization function and interaction parameters are > identical for these orbitals). > > best regards, > Steffen Backes > > ------------------------------ Message: 3 Date: Wed, 28 May 2014 09:16:46 -0400 From: Michele Dolfi <dolfim(a)phys.ethz.ch> To: comp-phys-alps-users(a)lists.phys.ethz.ch Subject: Re: [ALPS-users] Variational hopping parameter Message-ID: <C16EA761-87AF-4E04-B966-4F861E887659(a)phys.ethz.ch> Content-Type: text/plain; charset="windows-1252" Dear Nina, In the latest release of ALPS 2.2.0b3 we introduced a new set of codes based on MPS. These codes use the ALPS model and lattice library, therefore there is not no problem running this kind of simulations. To do so: 1. you need to create a custom lattice with a different type for each bond. https://alps.comp-phys.org/mediawiki/index.php/Tutorials:LatticeHOWTO 2. the model ?fermion Hubbard? is already able to handle different hopping amplitudes, just specify all values with the parameters t0=?, t1=?, ? where the number correspond to the bond type you specified in the lattice 3. finally you can setup a simulation using the new mps_evolve code. the easiest is to look at the mps-05 and mps-06 tutorials to have an idea on how to run the code. Best regards, Michele -- ETH Zurich Michele Dolfi Institute for Theoretical Physics HIT G 32.4 Wolfgang-Pauli-Str. 27 8093 Zurich Switzerland dolfim(a)phys.ethz.ch www.itp.phys.ethz.ch +41 44 633 78 56 phone +41 44 633 11 15 fax On 27 May 2014, at 18:30, Michael Wall <mwall.physics(a)gmail.com> wrote: > Dear Nina, > > The TEBD code in ALPS is not set up for site-dependent Hubbard parameters. Some of the other ALPS developers may be able to answer better whether such functionality will be added in near-term ALPS MPS codes. If not, Open Source MPS can perform the sorts of calculations you want to do, and eventually will become part of ALPS. > > -Michael > > > > > On Fri, May 23, 2014 at 2:02 AM, bondnina <bondnina(a)gmail.com> wrote: > Hi dear Alps users. > I wonder is there any possibility to setup different hopping parameters for each site in the Hubbard chain and evaluate such a system using TEBD technic. > Thank you for help. > > -- > Yours sincerely, Nina Bondarenko > 1024R/EAC56154 9F6C DDF8 6873 5D19 FF9A 600E 46A4 42BE EAC5 6154 >

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Variational hopping parameter
by bondnina 28 May '14

28 May '14

Hi dear Alps users. I wonder is there any possibility to setup different hopping parameters for each site in the Hubbard chain and evaluate such a system using TEBD technic. Thank you for help. -- Yours sincerely, Nina Bondarenko 1024R/EAC56154 9F6C DDF8 6873 5D19 FF9A 600E 46A4 42BE EAC5 6154

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Exploiting degeneracy in Hybridization impurity solver
by backes＠th.physik.uni-frankfurt.de 28 May '14

28 May '14

Dear Alps developers, is it possible to add an option for specifying and exploiting the degeneracy of some orbitals in the Hybridization expansion solver? E.g. for a paramagnetic calculation, where only half of the orbitals need to be measured (the input Hybridization function and interaction parameters are identical for these orbitals). best regards, Steffen Backes

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