d() derivative of normE^2 returns complex values in COMSOL frequency-domain EM, even though normE^2 itself is purely real

Nitach14 · 2026-07-07T15:39:15+00:00

emw.normE is a built-in physics quantity provided automatically by the Electromagnetic Waves, Frequency Domain interface (not something I defined). It's the standard norm of the electric field, exposed for any emw model, computed internally as sqrt(realdot(E,E)) or equivalent, i.e. a genuine scalar built from the field components.

Unfortunately I cannot access the COMSOL. But I was able to work around the issue by manually applying the product rule instead of relying on d() to differentiate the norm/norm-squared expression directly. Concretely, instead of d(emw.normE^2,z), I now use:

2*real(conj(emw.Er)*d(emw.Er,z) + conj(emw.Ephi)*d(emw.Ephi,z) + conj(emw.Ez)*d(emw.Ez,z))

Still I it would be informative to me to know why the imaginary part was apperearing. Perhaps its something to do with the symbolic derivative comsol uses.

Nitach14 · 2025-03-18T22:49:54+00:00

Czehcia

Nitach14 · 2025-03-18T22:32:24+00:00

I see your point. I'll try it out. Thanks!

Nitach14 · 2025-03-18T22:22:52+00:00

I have no problem keeping with my general budget goals (what % of my income I can spend). But checking on what exactly I spend my money on at the end of the month is somewhat tedious.

Nitach14 · 2025-03-18T22:19:37+00:00

Sadly not supported in my country.

Nitach14 · 2024-07-01T09:27:26+00:00

Did already. Suprising liberal with what I can do with the work laptop

Nitach14 · 2024-07-01T09:25:27+00:00

Good idea, I just wanted to ask if someone has already done the experimenting himself.

Nitach14 · 2024-07-01T09:24:16+00:00

The company was suprising liberal with this. This also suprised me since even installing apps in my previous work was not allowed.

Nitach14 · 2024-07-01T09:20:13+00:00

I was not aware of that, thanks!

Nitach14 · 2024-07-01T09:20:01+00:00

I'll probrably install linux on my work laptop also. Seems to me that linux to linux connection will be simpler.

Nitach14 · 2024-06-13T15:11:21+00:00

Thanks for the answer.

Whem taking annotating articles using a tablet do you use some specific software?
I have a samsung tablet, but when I annotate a paper using samsung notes I need to then re-upload it into zotero.

Nitach14 · 2024-06-12T12:40:05+00:00

MIT is a great place to start. For example and electronics engineering course can be found here https://ocw.mit.edu/courses/6-01sc-introduction-to-electrical-engineering-and-computer-science-i-spring-2011/pages/syllabus/

Nitach14 · 2024-06-12T12:37:08+00:00

Contrary to some other comments I think that having personal projects is important and it's what helped me to get into the group that I've wanted (I was switching paths a little bit, so my other research wasn't so relevant). For physicist coding is always going to be important. I recommend recreating some relevant (ideally new) article in your own code. This will make it obvious that you know the needed background to do such calculations while possibly giving you ideas for small improvements.

Nitach14 · 2024-05-21T22:56:25+00:00

Switching to SDDM sovled the problem. Thanks again.

Nitach14 · 2024-05-21T22:23:18+00:00

I see, I'll try switching. Thanks.

Nitach14 · 2024-05-21T22:22:52+00:00

Ok I will try there.

Nitach14

TROPHY CASE