Speaker
Description
Particle dark matter, along with many ultraviolet scenarios, suggest
that additional low-energy degrees of freedom remain to be discovered.
Theories of new physics may be understood as data models, for which the
Lagrangian couplings are model parameters. The net worth of a theory is
determined by its Bayesian evidence: the likelihood of precision
cosmology data is multiplied by the prior probability of the couplings,
and integrated over the coupling-space. Precision cosmology has made
great advances both in the collection of data and the efficient
computation of likelihoods. But whilst the complementary programme of
manufacturing candidate models is very active, it is far less
systematic, and priors are seldom specified.
Taking metric-affine gravity as an example, we review the formal
requirements of perturbative model-building with torsion and
non-metricity fields. We then present a framework for massively
automating the construction of new physics models, designed to scale
with the ever-increasing volume of data. Numerical polology uses nested
sampling to identify unitary and technically natural regions in
metric-affine coupling-space. Such models form self-consistent effective
field theories, which is essential since the predictivity of a model
(the ability to compute a likelihood) is endowed by the systematics of
QFT alone. The framework is adapted to bosonic theories of the dark
sector: the phenomenological implications of arbitrary field content
(field number, rank and index-symmetry) can be systematically explored
with recourse to tools such as GetDist and Cobaya. The framework is
inspired by the SOFTSUSY/SARAH tools for supersymmetric model-building,
and builds directly on the PSALTer software for modified gravity. The
latter is computer algebra software, which scales badly with complexity:
numerical polology overcomes this technical hurdle and facilitates
data-driven model-building.
As an illustration, we derive simple posterior reweightings from black
hole superradiance, large scale structure, and gravitational wave
dispersion. We also discuss realistic prospects for more sophisticated
likelihood plugins. We then perform a high-resolution survey of the
coupling-space of symmetric rank-two fields, and rank-three fields
corresponding to torsion and non-metricity.