I’ve been trying to implement a model with multiple generations of a real scalar “phi”, which leads to a parameter with four indices if the quartic self-interaction is included. The corresponding SPheno source code created by MakeSPheno[] yields compiler errors with such a parameter, though.

I’ve found the old forum topic “3-index parameter” and wanted to ask if there are still problems with parameters with more than two indices.

Hi,

It's likely that this is not supported. I haven't ever worked with a model having that feature or have one at hand to test it.
The simple solution is to define independent fields. The only drawback is that the Lagrangian will be a bit lengthy.

Cheers
Florian