  The Standard Model (SM) possesses an instability at high scales that would be
catastrophic during or just after inflation, and yet no new physics has been
seen to alter this. Furthermore, modern developments in quantum gravity suggest
that the 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 $\phi$ could have decayed into many sectors. In this work we
propose the following explanation for all of this: we allow the lowest
dimension operators with natural coefficients between the inflaton and both the
Higgs and hidden sectors. Such hidden sectors are assumed to be entirely
natural; 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 (and suppressed) operators. On the other hand, the SM
possesses a special feature: it includes a light Higgs $H$, presumably for life
to exist, and hence it allows a super-renormalizable coupling to the inflaton
$\phi H^\dagger H$, which allows rapid decay into the SM. We show that this
naturally (i) removes the instability in the Higgs potential both during and
after inflation due to a tree-level effect that increases the value of the
Higgs self-coupling from the IR to the UV when one passes the inflaton mass,
(ii) explains why the SM is dominant in the early universe, (iii) allows dark
matter to form in hidden sector/s through subsequent dynamics (or axions, etc),
(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.
