I've been trying to get a better grasp of the vacuum catastrophe problem, that is vacuum energy as calculated in QFT vs the observed value in cosmology differs by 120 orders of magnitude. The issue fundamentally arises from the fact that if we try to calculate the absolute value of the zero point energy of any quantum field the result is necessarily divergent (infinity) as we add all the possible modes of vibrations (frequencies) of the field, which are infinite. It is then speculated that there exist a cutoff frequency which would prevent adding infinite quantities, but to me it seems rather arbitrary this cutoff corresponds to the Planck lenght, which is simply a number where seemingly unphysical stuff happens when we cram two electrons too close together. Using this reasoning we get the wildly wrong (according to measurements) 10^110 value.
If we instead try to fit the measured value in the equations (from astronomical observations of the Hubble constant), we get a corresponding cut off lenght of around 1 mm.
Now this result has mostly been deemed unphysical as well, but for reasons that are not really convincing to me, like the cutoff corresponding to the natural quantization of spacetime can't be 1 mm, but it doesn't seem to be necessarily related to that. It could stem from a totally different property of fields. To my understanding this cutoff doesn't prevent lower wavelength vibrations, it just prevents them at the fundamental level of the field (unexcited fields).
I'd be glad if anyone could link or just explain this issue better, and why they think 1 mm cutoff is/is not a valid solution.
I tried looking this stuff up online, but i couldn't really find many papers that tackled this issue (explaining a possible 1 mm cutoff), and many of those i found were rather hard to digest.
Something I will link though is these two studies, that hopefully will make it more clear where I'm trying to point the discussion: one that refutes first low energies cutoffs, then tries to generalize to any possible cutoff, using the common explanation of the Casimir effect as stemming from a quantum vacuum effect. The second study elegantly explains how a quantum vacuum interpretation of this effect is not legitimate mathematically, hence invalidating many assumptions of the first paper.
This paper discusses why a cut off of any kind in vacuum energy would produce different effects from those observed in the Casimir experiment (IF vacuum energy is responsible for the effect)
This paper explains why the Casimir effect is better understood with Van Der Waals forces rather than vacuum fluctuations: