Stars as Laboratories for Fundamental Physics - MPP Theory Group

Preface
xv
Second, particles from distant sources may decay, and there may
be photons or even measurable neutrinos among the decay products.
The absence of solar x- and γ-rays yields a limit on neutrino radiative
decays which is as “safe” as a laboratory limit, yet nine orders
of magnitude more restrictive. An even more restrictive limit obtains
from the absence of γ-rays in conjunction with the SN 1987A neutrinos
which allows one to conclude, for example, that even ν τ must obey
the cosmological limit of m < ν ∼ 30 eV unless one invents new invisible
decay channels.
Third, the emission of weakly interacting particles causes a direct
energy-loss channel from the interior of stars. For neutrinos, this effect
has been routinely included in stellar evolution calculations. If new lowmass
elementary particles were to exist such as axions or other Nambu-
Goldstone bosons, or if neutrinos had novel interactions with the stellar
medium such as one mediated by a putative neutrino magnetic dipole
moment, then stars might lose energy too fast. A comparison with the
observed stellar properties allows one to derive restrictive limits on the
operation of a new energy-loss or energy-transfer mechanism and thus
to constrain the proposed novel particle interactions.
While these and related arguments as well their application and results
are extensively covered here, I have not written on several topics
that might be expected to be represented in a book on the connection
between particle physics and stars. Neutron stars have been speculated
to consist of quark matter so that in principle they are a laboratory to
study a quark-gluon plasma. As I am not familiar enough with the literature
on this interesting topic I refer the reader to the review by Alcock
and Olinto (1988) as well as to the more recent proceedings of two topical
conferences (Madsen and Haensel 1992; Vassiliadis et al. 1995).
I have also dodged some important issues in the three-way relationship
between cosmology, stars, and particle physics. If axions are not
the dark matter of the universe, it is likely filled with a “background
sea” of hypothetical weakly interacting massive particles (WIMPs) such
as the lightest supersymmetric particles. Moreover, there may be exotic
particles left over from the hot early universe such as magnetic
monopoles which are predicted to exist in the framework of typical
grand unified theories (GUTs). Some of the monopoles or WIMPs
would be captured and accumulate in the interior of stars. GUT
monopoles are predicted to catalyze nucleon decay (Rubakov-Callaneffect),
providing stars with a novel energy source. This possibility can
be constrained by analogous methods to those presented here which
limit anomalous energy losses. The resulting constraints on the pres-