  Hot new early dark energy describes a supercooled, first-order phase
transition that takes place at sub-eV temperatures in the dark sector. It
lowers the sound horizon, which provides a possible solution to the Hubble
tension, and, at the same time, it can explain the neutrino masses through the
inverse seesaw mechanism by making a set of sterile Majorana fermions massive.
First, we argue that this scenario strengthens existing cosmological bounds on
the heaviest neutrino mass. This, in turn, constrains the dark sector
temperature, which provides us in total with two falsifiable predictions. In a
second step, we discuss the phenomenological consequences of embedding hot new
early dark energy in a larger gauge group that is partially broken above the
TeV scale. This novel theory, which could even be motivated independently of
the Hubble tension, completes the high-energy corner of the inverse seesaw
mechanism and explains the mass of a dark matter candidate that can be produced
through gravitational interactions at high energies.
