Meaning of RGEs::StillEntangled

[TomSt]

Hi Florian,

I am trying to write a model file, but I always come across the error "RGEs::StillEntangled" - however, it is not quite clear from the source code what happens there. Could you outline what causes this behaviour so I can identify my error?

Thanks for your time,
Tom

[FStaub]

Hi,

the error message appears if you have couplings with the same external particles. For instance, looking at a left-right model there are two Yukawa couplings:

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+ YQ1 Phi.QLbar.QR  + YQ2 conj[Phi].QLbar.QR 

After splitting Phi in it's real components as it has to be done for the RGE calculation one gets

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(YQ1+YQ2) phi.QLbar.QR + (YQ1-YQ2) sigma.QLbar.QR

This is the origin for the problem, because now YQ1 and YQ2 are no longer separated. Thus, to get the RGEs for the couplings SARAH calculates the beta-functions for both sets of external particles and uses

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beta(YQ1) = 1/2 (beta(phi.QLbar.QR) +  beta(sigma.QLbar.QR))
beta(YQ2) = 1/2 (beta(phi.QLbar.QR) -  beta(sigma.QLbar.QR))

to disentangle the running. Unfortunately, the routine to disentangle the running in that way checks only for simple superpositions like this and tries different combination of the external indices (for instance in THDM models you can separate the running of lambda by using specific external isospin combinations for the Higgs fields). In more complicated cases, or if you have tree couplings with the same fields, it might fail.

Cheers,
Florian

[TomSt]

Hi Florian,

thanks for the fast answer, this explains a lot. However, I am experiencing this for some VEVs as well, which I think is strange. I am indeed working with a left-right model, featuring a Higgs quadruplet transforming fundamentally under both SU(2) groups. It is supposed to have two independend VEVs, which however cannot be disentangled by SARAH. Assuming that the running of the VEVs is calculated using the anomalous dimensions of the scalar field, it is hard to believe that these cannot be disentangled, since these are calculated using two-point functions of two different components of this scalar quadruplet. Do you have any idea what might be going on?

Cheers,
Tom

[FStaub]

Hi,

here is an update. It works at least with a toy LR model for me now:
replace the existing file in Package/RGEs/ by the attached one.

Cheers,
Florian

[TomSt]

Hi Florian,

thanks a lot! This patch works fine for me. You should consider to include this in the next release.

Cheers,

Tom