The Higgs, Naturalness, and Dark Sectors

The Higgs, Naturalness, and Dark Sectors
Prof. Mark Hertzberg, Tufts University
Date and time: Fri, Dec 06, 2019 - 2:15pm
Location: LGRT 419B
Category: ACFI Seminar

Modern developments in quantum gravity, especially string theory, suggest that the Standard Model (SM) degrees of freedom are not unique; that a typical low energy effective theory should include a large assortment of hidden sector degrees of freedom. It is therefore puzzling that cosmological constraints from BBN and CMB reveal that the early universe was almost entirely dominated by the SM, when the inflaton could have decayed into many sectors. Furthermore, the SM taken seriously to high scales, possesses an instability that would be catastrophic during inflation, as I will quantify in detail, and yet no new physics has been seen to correct this. In this talk, I put forth an explanation for all of these puzzles: the hidden sectors are in fact entirely natural with O(1) input parameters; this means all unprotected masses are pushed up to high scales and project out of the spectrum, while only massless (or protected) degrees of freedom remain, and so the inflaton can only reheat these sectors through higher dimension operators. On the other hand, the SM possesses a special feature: it includes a light Higgs, presumably for life to exist, and hence it allows a renormalizable coupling to the inflaton, which allows rapid decay into the SM. I then show that this naturally (i) removes the instability in the Higgs potential both during and after inflation, (ii) explains why the SM is dominant in the early universe, (iii) allows dark matter to form in hidden sector/s through subsequent strong dynamics, which I describe in detail, (iv) allows for high reheating and baryogenesis, and (v) accounts for why there so far has been no direct detection of dark matter or new physics beyond the SM.