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Dear Nektar++ Users:

I am Wang Zhouyang, and I am sorry to present some questions about the Modified Arnoldi Driver in linear stability analysis:

1. When I was doing parallel computation, I was prompted that Arpack algorithm could not implement parallel in Nektar++. Although this is true based on other user communications here, I still want this issue to be confirmed. Thank you very much.

2. As described in the user documentation, the Arpack package can specify properties such as LargestMag or LargestReal etc to output eigenvalues. For the Modified Arnoldi algorithm, what is the property of the eigenvalues utilized to write the result? (For example, nvec=4, do the four eigenvectors output after iteration have the largest four magnitudes or the top four growth rates or other criteria?)

3. In solving, is it reasonable to have a mode with a frequency of 0? I understand it as a flow phenomenon of pure exponential growth (or decay).In my humble opinion, the frequency may suggest a flow structure with oscillation, and it would be unstable (or attenuated) regarding to the growth rate.

Thank you very much for your help, and I sincerely hope to get your answers.
Thanks to the Nektar++ project team.

Best Regards,

Wang Zhouyang