Hi Michael,
I see, I thought that might be the case. I know very little about Fortran, but if it's possible to set up this initial Hamiltonian/state, I'd like to give it a go, even if I am unable to get it to work. Could I have further details on this please?
Thank you, Joseph
On 7 Aug 2013, at 11:00, comp-phys-alps-users-request@lists.phys.ethz.ch wrote:
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Today's Topics:
- Question concerning an initial state in TEBD (Joseph Prentice)
- Re: Question concerning an initial state in TEBD (Michael Wall)
Message: 1 Date: Tue, 6 Aug 2013 12:25:40 +0000 From: Joseph Prentice Joseph.Prentice@physics.ox.ac.uk To: "comp-phys-alps-users@lists.phys.ethz.ch" comp-phys-alps-users@lists.phys.ethz.ch Subject: [ALPS-users] Question concerning an initial state in TEBD Message-ID: 747861816F6A5C47BE50FCA07F5B2B4A0DF3D2@EXCHNG16.physics.ox.ac.uk Content-Type: text/plain; charset="us-ascii"
Hi again all,
I just had a short question about the TEBD code in ALPS. I would like to study the evolution of an initial state that is a Neel state, but rotated by an angle /alpha about the y-axis, under the XXZ Hamiltonian. A Hamiltonian whose ground state would be the right one would simply have a magnetic field along the direction of /alpha that swaps direction at each site i.e. (-1)^l *(cos /alpha *S^z_l + sin /alpha *S^x_l) where l is the site number, but I can't see a way to put this into the code. Is alternating the sign of the interaction in this way possible? Also, if there is another way of producing such a state in the TEBD code, it would be wonderful if someone pointed it out, I would be very grateful.
Thank you very much,
Joseph Prentice
Message: 2 Date: Tue, 6 Aug 2013 14:31:20 -0600 From: Michael Wall mwall.physics@gmail.com To: comp-phys-alps-users@lists.phys.ethz.ch Subject: Re: [ALPS-users] Question concerning an initial state in TEBD Message-ID: CA+DwVMoeLK_TfLEi4DGHCkG7riYn3MHOZz6=E3TaPLcxcekBLQ@mail.gmail.com Content-Type: text/plain; charset="iso-8859-1"
Hi Joseph,
At present, the only initial states supported by tebd are ground states of translation-invariant Hamiltonians or the 'kink' initial state used in the spin tutorials. You can edit the source file tebd.f90 to write in another product state of your choice. If this is the route you would like to follow I can give you more details. The next generation of MPS codes for ALPS will include much greater flexibility in the choice of initial state.
-Michael
On Tue, Aug 6, 2013 at 6:25 AM, Joseph Prentice < Joseph.Prentice@physics.ox.ac.uk> wrote:
Hi again all,
I just had a short question about the TEBD code in ALPS. I would like to study the evolution of an initial state that is a Neel state, but rotated by an angle /alpha about the y-axis, under the XXZ Hamiltonian. A Hamiltonian whose ground state would be the right one would simply have a magnetic field along the direction of /alpha that swaps direction at each site i.e. (-1)^l *(cos /alpha *S^z_l + sin /alpha *S^x_l) where l is the site number, but I can't see a way to put this into the code. Is alternating the sign of the interaction in this way possible? Also, if there is another way of producing such a state in the TEBD code, it would be wonderful if someone pointed it out, I would be very grateful.
Thank you very much,
Joseph Prentice
Hi Joseph,
You will modify the source file tebd.f90, which also means you will need to re-build ALPS from source when you are finished. The lines to modify are 162-176, in which the array "carray" is constructed. This array specifies a product state \prod_{i=1}^L \sum_{j=1}^d c_{i j} |i_j>, where d is the local dimension of a single site, L is the number of lattice sites, and c_{i j} is the expansion of the wavefunction at site i in the local basis states |i_j>. The coefficients c_{i j} are stored as carray(j,i). You will also want to set qSwitch to .false. if your initial eigenstate is not an eigenstate of S_z. Hope this helps.
-Michael
On Wed, Aug 7, 2013 at 5:26 AM, Joseph Prentice < Joseph.Prentice@physics.ox.ac.uk> wrote:
Hi Michael,
I see, I thought that might be the case. I know very little about Fortran, but if it's possible to set up this initial Hamiltonian/state, I'd like to give it a go, even if I am unable to get it to work. Could I have further details on this please?
Thank you, Joseph
On 7 Aug 2013, at 11:00, comp-phys-alps-users-request@lists.phys.ethz.ch wrote:
Send Comp-phys-alps-users mailing list submissions to comp-phys-alps-users@lists.phys.ethz.ch
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You can reach the person managing the list at comp-phys-alps-users-owner@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:
- Question concerning an initial state in TEBD (Joseph Prentice)
- Re: Question concerning an initial state in TEBD (Michael Wall)
Message: 1 Date: Tue, 6 Aug 2013 12:25:40 +0000 From: Joseph Prentice Joseph.Prentice@physics.ox.ac.uk To: "comp-phys-alps-users@lists.phys.ethz.ch" comp-phys-alps-users@lists.phys.ethz.ch Subject: [ALPS-users] Question concerning an initial state in TEBD Message-ID: 747861816F6A5C47BE50FCA07F5B2B4A0DF3D2@EXCHNG16.physics.ox.ac.uk Content-Type: text/plain; charset="us-ascii"
Hi again all,
I just had a short question about the TEBD code in ALPS. I would like to
study the evolution of an initial state that is a Neel state, but rotated by an angle /alpha about the y-axis, under the XXZ Hamiltonian. A Hamiltonian whose ground state would be the right one would simply have a magnetic field along the direction of /alpha that swaps direction at each site i.e. (-1)^l *(cos /alpha *S^z_l + sin /alpha *S^x_l) where l is the site number, but I can't see a way to put this into the code. Is alternating the sign of the interaction in this way possible?
Also, if there is another way of producing such a state in the TEBD
code, it would be wonderful if someone pointed it out, I would be very grateful.
Thank you very much,
Joseph Prentice
Message: 2 Date: Tue, 6 Aug 2013 14:31:20 -0600 From: Michael Wall mwall.physics@gmail.com To: comp-phys-alps-users@lists.phys.ethz.ch Subject: Re: [ALPS-users] Question concerning an initial state in TEBD Message-ID: <CA+DwVMoeLK_TfLEi4DGHCkG7riYn3MHOZz6=
E3TaPLcxcekBLQ@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hi Joseph,
At present, the only initial states supported by tebd are ground states
of
translation-invariant Hamiltonians or the 'kink' initial state used in
the
spin tutorials. You can edit the source file tebd.f90 to write in
another
product state of your choice. If this is the route you would like to follow I can give you more details. The next generation of MPS codes for ALPS will include much greater flexibility in the choice of initial
state.
-Michael
On Tue, Aug 6, 2013 at 6:25 AM, Joseph Prentice < Joseph.Prentice@physics.ox.ac.uk> wrote:
Hi again all,
I just had a short question about the TEBD code in ALPS. I would like to study the evolution of an initial state that is a Neel state, but
rotated
by an angle /alpha about the y-axis, under the XXZ Hamiltonian. A Hamiltonian whose ground state would be the right one would simply have
a
magnetic field along the direction of /alpha that swaps direction at
each
site i.e. (-1)^l *(cos /alpha *S^z_l + sin /alpha *S^x_l) where l is the site number, but I can't see a way to put this into the code. Is alternating the sign of the interaction in this way possible? Also, if there is another way of producing such a state in the TEBD
code,
it would be wonderful if someone pointed it out, I would be very
grateful.
Thank you very much,
Joseph Prentice
comp-phys-alps-users@lists.phys.ethz.ch