Sy-reflection is a symmetry, and thus there is always the y-reflected state as well which has the same energy.

For the Sy-Sy correlations you can just measure S+ - S+, S+ - S- and S- - S- correlations and calculate it from the, without the need for complex arithmetic

Matthias

On Jan 14, 2009, at 12:56 PM, zhian asadzadeh wrote:

Dear I don't think so, when we increase the field this is true. and for tow point correlations <Sy Sy>, I need to define Sy. Thanks Zhian

On Thu, Jan 15, 2009 at 12:20 AM, Matthias Troyer troyer@phys.ethz.ch wrote: Then <Sy> should be 0 by symmetry

On Jan 14, 2009, at 12:48 PM, zhian asadzadeh wrote:

...

Hi I have an isotropy in Z direction, and the field is in X direction Thanks Zhian

On Thu, Jan 15, 2009 at 12:15 AM, Matthias Troyer <troyer@phys.ethz.ch

...

wrote:

Is the transverse field in the x or y direction?

On Jan 14, 2009, at 12:43 PM, zhian asadzadeh wrote:

...

Hi

My model doesn't conserve U(1) symmetry. My model is spin chain in transverse magnetic field. if we want to define the Sy we must use complex number i, so can we define complex number in Model.XML file?

Thanks, Zhian

On Wed, Jan 14, 2009 at 9:54 PM, Matthias Troyer <troyer@phys.ethz.ch

...

wrote:

Does your model conserve SU(2) or U(1) symmetry? In that case the expectation value is 0. Otherwise you should be able to measure it

Matthias

On 30 Dec 2008, at 04:33, zhian asadzadeh wrote:

Hi Dears

Can i measure the expectation value of the y component of Spin operator (Sy)?( in DMRG )

Thanks

Zhian