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Topics - Andreas Brinkmann

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Bug reports / Preparation with PeriodicFunction[] in Hamiltonian fails
« on: February 04, 2020, 07:13:06 PM »
Hi Malcolm & Christian,
thanks for releasing version 3.4.2. I noticed that in 3.4.2 Signal1D fails if I have a Hamiltonian with PeriodicFunction[] in the Preparation. The same code works fine in 3.3.1. Please see attached. The workaround by using BackgroundGenerator and a Delay in Preparation works fine.
All the best,

This is not really a bug, but under non-ideal conditions (large Hamiltonians, non-sufficient accuracy settings), the numerically calculated eigenvalues wrsk in the COMPUTE routine can have a small but significant imaginary part. This can translate to peak frequencies that have an imaginary part if the DigitalFrequencyResolution->True setting fails to "snap" the peak frequency to the frequency grid. In that case the FT might fail.

I would recommend taking Re[wrsk] of the eigenvalues and/or print a warning if the imaginary part is significant.

Please see attached your RotationalResonance.nb Example, that I forced into the above behavior.

Bug reports / More of a question: Ordering of Zeeman product states
« on: January 29, 2015, 08:45:18 PM »

I noticed that in SpinDynamica the Zeeman product states for example for a 2 spin 1/2 system per default are ordered as {|αα>, |βα>, |αβ>, |ββ>}. However, in the literature (e.g. spin dynamics) and other calculation programs (Simpson, mPackages) the order is {|αα>, |αβ>, |βα>, |ββ>}.

As a result, one has to be very careful when transferring a matrix representation from SpinDynamica for example to Simpson.

Is there a flag to switch the way the product states are generated?


Feature requests / Launch remote kernels in PrepareParallel
« on: September 26, 2013, 07:58:40 PM »
Currently, PrepareParallel launches local kernels only. It's relatively easy to setup remote kernels under "Preferences->Parallel->Remote Kernels", however they would not be started with simply LaunchKernels[number]. For demonstration, I added a simple option Parallel->AllConfigured to PrepareParallel that will launch all configured kernels, both local and remote:
Code: [Select]
MatchQ[parallel, AllConfigured],
  Scan[LaunchKernels, $ConfiguredKernels]),
Here, I don't try to do any kernel bookkeeping, so I just close the current ones and launch all configured ones as new. Ideally, one could imagine some fancy bookkeeping where for a certain number of requested kernels, first local kernels are started, then remote kernels and at the end additional local kernels.

Bug reports / proton magnetogyric ratio typo!
« on: June 14, 2013, 09:46:19 PM »
Dear all,

there is a typo in the magnetogyric ratio of 1H:

26.75522128e7 instead of 26.7522128e7

Please correct, it took me a while to discover this small inconsistency of newer SpinDynamica versions to older ones.


Feature requests / ZCW6044 and simple parallelization of Signal1D
« on: October 01, 2012, 09:53:47 PM »
Dear all,

please find here

a modified version of SDv2.5.3 that provides both 6044 ZCW powder angles (OrientationalSampling.nb) and a relative simple parallelization of the Signal1D routine when an ensemble average is performed (SpinDynamics.nb).

The RotationalResonance example demonstrates how to use the parallel version. It also shows that there is some (serial) overhead in the Signal1D routine, I have added some comments in the code of SpinDynamics.nb to indicate where I used Mathematica's Parallel... routines and which steps are not scaling nicely.

All the best,


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