AsymSafe QG rejects SUSY & extra dims (Donà Eichhorn Percacci)

[marcus]

Percacci and friends have found incompatibility between Asymptotically Safe quantum gravity on the one hand and, on the other, extensions of the Standard Model which involve supersymmetry and/or extra dimensions.

If evidence for supersymmetry or extra dimensions ever shows up that would tend to falsify AsymSafe.
On the other hand evidence supporting AS has been building up over the years and that tends to weigh against SUSY and universal extra dimensions.

The paper by Donà Eichhorn Percacci was just posted on arxiv today. http://arxiv.org/abs/1311.2898 It's pretty interesting. I'll quote some excerpts.

==quote "Matter matters in asymptotically safe quantum gravity" page 15==
In spite of these limitations, our work clearly shows that “matter matters” in asymptotically safe quantum gravity. Asymptotic safety might not be compatible with arbitrary extensions of the Standard Model; e.g., supersymmetric extensions and higher dimensions seem to be disfavoured. This opens a new route to obtain experimental guidance in the construction of a viable model of quantum gravity: The discovery of many new matter fields could potentially lead to a setting that is theoretically inconsistent with asymptotic safety.
==endquote==

But certain other extensions of Standard Model matter are compatible with asymptotic safety. Here's the paper's abstract:
==quote==
We investigate the compatibility of minimally coupled scalar, fermion and gauge fields with asymptotically safe quantum gravity, using nonperturbative functional Renormalization Group methods. We study d=4,5 and 6 dimensions and within certain approximations find that for a given number of gauge fields there is a maximal number of scalar and fermion degrees of freedom compatible with an interacting fixed point at positive Newton coupling. The bounds impose severe constraints on grand unification with fundamental Higgs scalars. Supersymmetry and universal extra dimensions are also generally disfavored. The standard model and its extensions accommodating right-handed neutrinos, the axion and dark-matter models with a single scalar are compatible with a fixed point.
==endquote==

 

[Evan Fox]

It looks like the paper is suggesting that while certain extensions of the Standard Model are incompatible with AsymSafe, there are still some that are compatible. It's worth noting that the authors are using a non-perturbative approach, which is a bit different than what has been used in the past. So, while their findings may not be definitive, they certainly provide interesting food for thought.