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A bstract We study a renormalizable model of Dirac fermion dark matter (DM) that communicates with the Standard Model (SM) through a pair of mediators — one scalar, one fermion — in the representation ( 6 , 1 , $$ \frac{4}{3} $$ 4 3 ) of the SM gauge group SU(3) c × SU(2) L × U(1) Y . While such assignments preclude direct coupling of the dark matter to the Standard Model at tree level, we examine the many effective operators generated at one-loop order when the mediators are heavy, and find that they are often phenomenologically relevant. We reinterpret dijet and pair-produced resonance and jets + $$ {E}_{\mathrm{T}}^{\mathrm{miss}} $$ E T miss searches at the Large Hadron Collider (LHC) in order to constrain the mediator sector, and we examine an array of DM constraints ranging from the observed relic density Ω χ $$ {h}_{\mathrm{Planck}}^2 $$ h Planck 2 to indirect and direct searches for dark matter. Tree-level annihilation, available for DM masses starting at the TeV scale, is required in order to produce Ω χ $$ {h}_{\mathrm{Planck}}^2 $$ h Planck 2 through freeze-out, but loops — led by the dimension-five DM magnetic dipole moment — are nonetheless able to produce signals large enough to be constrained, particularly by the XENON1T experiment. In some benchmarks, we find a fair amount of parameter space left open by experiment and compatible with freeze-out. In other scenarios, however, the open space is quite small, suggesting a need for further model-building and/or non-standard cosmologies. 

A bstract We investigate a novel interplay between the decay and annihilation of a particle whose mass undergoes a large shift during a first order phase transition, leading to the particles becoming trapped in the false vacuum and enhancing their annihilation rates as the bubbles of true vacuum expand. This opens up a large region of the parameter space where annihilations can be important. We apply this scenario to baryogenesis, where we find that annihilations can be enhanced enough to generate the required baryon asymmetry even for relatively tiny annihilation cross sections with modest CP asymmetries. 

A bstract In the framework where the strong coupling is dynamical, the QCD sector may confine at a much higher temperature than it would in the Standard Model, and the temperature-dependent mass of the QCD axion evolves in a non-trivial way. We find that, depending on the evolution of Λ QCD , the axion field may undergo multiple distinct phases of damping and oscillation leading generically to a suppression of its relic abundance. Such a suppression could therefore open up a wide range of parameter space, resurrecting in particular axion dark-matter models with a large Peccei-Quinn scale f a ≫ 10 12 GeV, i.e., with a lighter mass than the standard QCD axion. 

A bstract We explore the possibility that dark matter is a pair of vector-like fermionic SU(2) L doublets and propose a novel mechanism of dark matter production that proceeds through the confinement of the weak sector of the Standard Model. This confinement phase causes the Standard Model doublets and dark matter to confine into pions. The dark pions freeze-out before the weak sector deconfines and generate a relic abundance of dark matter. We solve the Boltzmann equations for this scenario to determine the scale of confinement and constituent dark matter mass required to produce the observed relic density. We determine which regions of this parameter space evade direct detection, collider bounds, and successfully produce the observed relic density of dark matter. For a TeV scale pair of vector-like fermionic SU(2) L doublets, we find the weak confinement scale to be ∼ 700 TeV. 

We examine a real electroweak triplet scalar field as dark matter,abandoning the requirement that its relic abundance is determinedthrough freeze out in a standard cosmological history (a situation whichwe refer to as `miracle-less WIMP’). We extract the bounds on such aparticle from collider searches, searches for direct scattering withterrestrial targets, and searches for the indirect products ofannihilation. Each type of search provides complementary information,and each is most effective in a different region of parameter space. LHCsearches tend to be highly dependent on the mass of the SU(2) chargedpartner state, and are effective for very large or very tiny masssplitting between it and the neutral dark matter component. Directsearches are very effective at bounding the Higgs portal coupling, butineffective once it falls below \lambda_{\text{eff}} \lesssim 10^{-3} λ eff ≲ 10 − 3 .Indirect searches suffer from large astrophysical uncertainties due tothe backgrounds and J J -factors,but do provide key information for \sim ∼ 100 GeV to TeV masses. Synthesizing the allowed parameter space, thisexample of WIMP dark matter remains viable, but only in miracle-lessregimes. 

A bstract Standard lore states that there is tension between the need to accommodate the relic density of a weakly interacting massive particle and direct searches for dark matter. However, the estimation of the relic density rests on an extrapolation of the cosmology of the early Universe to the time of freeze out, untethered by observations. We explore a nonstandard cosmology in which the strong coupling constant evolves in the early Universe, triggering an early period of QCD confinement at the time of freeze out. We find that depending on the nature of the interactions between the dark matter and the Standard Model, freeze out during an early period of confinement can lead to drastically different expectations for the relic density, allowing for regions of parameter space which realize the correct abundance but would otherwise be excluded by direct searches.