# Altarelli & Meloni's GUT-minimalism

1. May 7, 2013

### mitchell porter

http://arxiv.org/abs/1305.1001
A non Supersymmetric SO(10) Grand Unified Model for All the Physics below $M_{GUT}$
Guido Altarelli, Davide Meloni
(Submitted on 5 May 2013)
We present a renormalizable non supersymmetric Grand Unified SO(10) model which, at the price of a large fine tuning, is compatible with all compelling phenomenological requirements below the unification scale and thus realizes a minimal extension of the SM, unified in SO(10) and describing all known physics below $M_{GUT}$. These requirements include coupling unification at a large enough scale to be compatible with the bounds on proton decay; a Yukawa sector in agreement with all the data on quark and lepton masses and mixings and with leptogenesis as the origin of the baryon asymmetry of the Universe; an axion arising from the Higgs sector of the model, suitable to solve the strong CP problem and to account for the observed amount of Dark Matter. The above constraints imposed by the data are very stringent and single out a particular breaking chain with the Pati-Salam group at an intermediate scale $M_I\sim10^{11}$ GeV.

For those interested in "minimalism", this is an interesting construction because it incorporates GUT successes that aren't part of the nuMSM.

To turn this into a true "phenomenological theory of everything", you also need to add an inflaton (singlet under SO(10), I guess) and e.g. a cosmological constant for the dark energy.

2. May 7, 2013

### arivero

Baez and Huerta did a good job explaining the breaking via a square with sides

SO(10)---> PatiSalam,
SO(10)--->SU(5)
PatiSalam---> StandardModel
SU(5)---> StandardModel

It is amusing that there is a counterpart of the square with manifolds, looking the groups as isometries on compact manifolds, with the relabeling

SO(10) ==== sphere S9
SU(5) ===== CP4
P-S ===== S3 x S5
SM ==== Witten's 7 dim manifolds.

Because of this, a naive, unfulfilled expectation of the string approach had been to produce SM from M-Theory, PatiSalam (and/or SU(5)) from F-Theory and SO(10) from S-theory.

Last edited: May 7, 2013