for the exact result, we know the model is integrable, so by fermionization
and finally diagonalizing the Hamiltonian we will end up to an Hamiltonian
with sum over independent modes,
H=\sum_{k} E(k) (2 a_{k}^{dagger} a_{k}-1)
for the T=0 ground state energy, I have compared with DMRG results which are
exactly same, so I am sure up to this point the form of E(k) and my
summation over k space is correct.
so finally for E(T) simply we have:
E(T)=\sum_{k} E(k)(2*n(k,T)-1) in which n(k,T)=1/(exp(E(k)/T)+1) ::with
Boltzmann constant=1
Regards,
Zhian.
On Sun, Jul 24, 2011 at 12:00 PM, <
comp-phys-alps-users-request@lists.phys.ethz.ch> wrote:
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Today's Topics:
- Quantum Monte Carlo for Ising in transverse field
(zhian asadzadeh)
- Re: Quantum Monte Carlo for Ising in transverse field
(Matthias Troyer)
Message: 1
Date: Sat, 23 Jul 2011 16:29:39 +0200
From: zhian asadzadeh zhian.asadzadeh@gmail.com
Subject: [ALPS-users] Quantum Monte Carlo for Ising in transverse
field
To: comp-phys-alps-users@lists.phys.ethz.ch
Message-ID:
<CAEw6G6sPavSO0RMreyy701xo+LN4M4LGrBzOLJkonEKs9S=Wkw@mail.gmail.com
Content-Type: text/plain; charset="iso-8859-1"
Dear Matthias,
my intention is doing finite T QMC for 2D ising in transverse field with
the following Hamiltonian:
H=-J \Sigma_{i,j} S_{i}^{z} S_{j}^{z}-h \Sigma_{i} S_{i}^{x}
but for checking the accuracy of the numeric I did some checks for 1D
case which we can have an exact results,
probably I am expecting too much accuracy, for example:
L=100, T=0.32859
Exact:: E(T)=-105.29789708270407, Mx(T)=0.27030367598168420
looper:: E(T)=-105.61795 (0.00554), M(T)=0.4093185 (0.000138) ( I
think it is in z direction)
with SWEEPS:6000000, THERMALIZATION=2000000
I have checked also for other sizes and very large SWEEPS.
I don't expect to get exact result but I need much more accuracy in the
calculated energy.
and also other question: that magnetization which looper calculates is
in the z direction?
can I also measure M_{x} just with declaring it in parm file?
Thanks a lot,
Zhian.
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Today's Topics:
- restarting Lanczos iteration (jessica.alfonsi@unipd.it)
- Quantum Monte Carlo for Ising in transvers field (zhian asadzadeh)
- Re: Quantum Monte Carlo for Ising in transvers field
(Matthias Troyer)
- Re: restarting Lanczos iteration (Matthias Troyer)
Message: 1
Date: Fri, 22 Jul 2011 12:22:47 +0200
From: jessica.alfonsi@unipd.it
Subject: [ALPS-users] restarting Lanczos iteration
To: comp-phys-alps-users@lists.phys.ethz.ch
Message-ID:
5b0ae17b0813c63a97720e0fbc6cc1c6.squirrel@webmail.unipd.it
Content-Type: text/plain;charset=utf-8
Hi all,
I'd like to modify the Lanczos *.cpp examples in IETL example folder to
be
able to restart the iteration from any interruption point during the
Lanczos iteration. I suppose first one has to dump some information, for
instance the cofficients of T-matrix and the starting vector, however the
more difficult part would be the resuming of the iteration. Can somebody
give me some hints on how accomplishing this task? Thanks in advance...
Best regards,
Jessica Alfonsi
Message: 2
Date: Fri, 22 Jul 2011 13:03:23 +0200
From: zhian asadzadeh zhian.asadzadeh@gmail.com
Subject: [ALPS-users] Quantum Monte Carlo for Ising in transvers field
To: comp-phys-alps-users@lists.phys.ethz.ch
Message-ID:
<
CAEw6G6vLtP2G8kviZ97cxgZy9Dv1x_MqyUzFWs9ejnM8WvwnmA@mail.gmail.com
Content-Type: text/plain; charset="iso-8859-1"
Dear All,
I am trying to do QMC at finite temperature for calculating the
magnetization of *Ising model in transverse field*, but I realized just
looper code is working for this model, ( the others codes doesn't work
with
off diagonal matrix elements) but the result are not so good.
I am interested to modify dirloop_sse for this model, is it possible?
I appreciate your help,
Thanks,
zhian.