**Collection Number**S012

**Collection Type**Series

## Flavor-specific scalars and dark sectors

New scalar bosons that are uncharged under the Standard Model have many phenomenological applications, and in particular may serve as mediators between the dark and visible sectors. Such scalars are often taken to have Higgs-like couplings to Standard Model fermions, in order to evade constraints from bounds on flavor-changing neutral currents.

## Some unknown unknowns, and some known unknowns in the Standard Model EFT

In recent years the Standard Model Effective Field Theory (SMEFT) has emerged as a well defined and systematically improvable theory to study the constraints on physics beyond the Standard Model. This formalism explains old mysteries in interpreting LEP data and offers a field theory framework to combine such data with LHC measurements of the properties of the Higgs. We discuss the current status of these combined studies.

## Exploring the dark universe through molecules and nuclei

Repeated null-results at dark matter experiments targeted at WIMP masses, have resulted in the spotlight shifting to lighter dark matter and more exotic WIMP candidates. In this talk I shall present the rich level structure of molecules and nuclei as a tool to explore MeV scale dark matter and dark forces. I will also present a novel detector concept that supplies energy to dark matter, thus accessing inelastic dark matter parameter space.

## Theoretical Models for Dark Matter: from WIMPs to Primordial Black Holes

Among the many candidates proposed to explain the nature of Dark Matter, WIMPs have been the most supported in the last decades, because of their success in a natural explanation of the current Dark Matter abundance and their ubiquitous presence in models addressing the hierarchy problem.

Other candidates that have been attracting some attention recently are Primordial Black Holes, which would have formed in the early history of the universe.

In my talk I will touch on both frameworks for the explanation of Dark Matter.

## Numerical Simulation of the Axion Field through the QCD Phase Transition

We perform a full (3+1)-dimensional numerical simulation of the axion field around the QCD epoch. Our aim is to fully resolve large dynamical non-linear effects in the inhomogenous axion field. These effects are important as they lead to large overdensities in the field at late times. Those overdensities will eventually evolve into axion minicluster, which have various phenomenological implications like microlensing events. It is therefore important to have a reliable estimate of the number of overdensities and their mass relation.

## Particle Phenomenology in the Era of Gravitational Wave Astronomy

After the detection of black hole and neutron star binary mergers at LIGO/Virgo, gravitational wave becomes a new observational channel that we didn't have access to years ago.

It is an interesting question to ask what kind of new particle physics this channel can probe.

To answer this question, one needs to fill the gap between the scales of the astrophysical processes and the fundamental structures.

## Hadron resonance decay widths from QCD in finite volume

Recent progress in determining scattering phase shifts, and hence, resonance properties from lattice QCD in finite volumes is presented.

The relationship between finite-volume stationary-state energies and the two-particle scattering K-matrix is discussed.

Details of the Monte Carlo computations of the finite-volume two-particle energies are described.

Results for pion-pion, kaon-pion, and nucleon-pion scattering are presented.

## Detecting Dark Blobs

Most current dark matter detection strategies, including both direct and indirect efforts, are based on the assumption that the galactic dark matter number density is quite high, allowing for the detection of rare scattering events. Such a paradigm arises naturally if the dark matter self-interactions are weak. However, strong interactions within the dark sector can give rise to large composite objects, whose detection requires a different experimental paradigm. We call these object Dark Blobs.

## Solving the Hierarchy Problem Discretely

We present a new solution to the Hierarchy Problem utilizing non-linearly realized discrete symmetries. The cancelations occur due to a discrete symmetry that is realized as a shift symmetry on the scalar and as an exchange symmetry on the particles with which the scalar interacts. We show how this mechanism can be used to solve the Little Hierarchy Problem as well as give rise to light axions.

## Quantum Loops in de Sitter space and Scale Dependent Galaxy Bias at Small Wave-Vectors

The power spectrum for fluctuations in the number density of galaxies can be very different in shape from the power spectrum for fluctuations in the mass density at very small wave vectors (i.e., large length scales) if the primordial density fluctuations are non-Gaussian. I review this phenomena. (It is fairly well known in the more astrophysical part of the cosmology community but less so in the particle physics part of the field.) Then I show that primordial non-Gaussianities that arise from quantum loop diagrams in de-Sitter space can give rise to this phenomena.