---------- Forwarded message ----------
From: <comp-phys-alps-users-request@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@lists.phys.ethz.ch


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Today's Topics:

   1. Exploiting degeneracy in Hybridization impurity solver
      (backes@th.physik.uni-frankfurt.de)
   2. Re: Exploiting degeneracy in Hybridization impurity solver
      (august@fzu.cz)
   3. Re: Variational hopping parameter (Michele Dolfi)


----------------------------------------------------------------------

Message: 1
Date: Wed, 28 May 2014 12:40:54 +0200
From: backes@th.physik.uni-frankfurt.de
To: comp-phys-alps-users@lists.phys.ethz.ch
Subject: [ALPS-users] Exploiting degeneracy in Hybridization impurity
        solver
Message-ID:
        <c3a4761d76660198b749e13b652541aa.squirrel@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@fzu.cz
To: comp-phys-alps-users@lists.phys.ethz.ch
Subject: Re: [ALPS-users] Exploiting degeneracy in Hybridization
        impurity solver
Message-ID: <63da888d9fd14d678d4270331e2a4696.squirrel@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@phys.ethz.ch>
To: comp-phys-alps-users@lists.phys.ethz.ch
Subject: Re: [ALPS-users] Variational hopping parameter
Message-ID: <C16EA761-87AF-4E04-B966-4F861E887659@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@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@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@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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