Generation of Asymmetric Dark Matter and Gravitational Waves

We consider the possibility of a gravitational wave signal in an asymmetric dark matter model. In this model a generative sector produces both the baryon asymmetry and a dark matter asymmetry in a strong first-order phase transtion. Bubble collisions during the phase transition lead to sound waves in the plasma which are a source of a stochastic gravitational wave background. We consider the prospects of future graviational wave observatories such as LISA and BBO detecting such a signal. Constraints on the model from Halo ellipticity, $\Delta N_{\rm eff}$ and direct detection experiments are also discussed.Comment: 4 pages, 3 figures. Prepared for the proceedings of the 29th Rencontres de Blois on Particle Physics and Cosmolog

Gravitational waves from the asymmetric-dark-matter generating phase transition

The baryon asymmetry, together with a dark matter asymmetry, may be produced during a first order phase transition in a generative sector. We study the possibility of a gravitational wave signal in a model realising such a scenario. We identify areas of parameter space with strong phase transitions which can be probed by future, space based, gravitational wave detectors. Other signals of this scenario include collider signatures of a $Z'$, DM self interactions, a contribution to $\Delta N_{\rm eff}$ and nuclear recoils at direct detection experiments.Comment: 23 pages, 3 figures. V2: corrected typo, added references. V3: small corrections, added reference

Asymmetric thermal-relic dark matter: Sommerfeld-enhanced freeze-out, annihilation signals and unitarity bounds

Dark matter that possesses a particle-antiparticle asymmetry and has thermalised in the early universe, requires a larger annihilation cross-section compared to symmetric dark matter, in order to deplete the dark antiparticles and account for the observed dark matter density. The annihilation cross-section determines the residual symmetric component of dark matter, which may give rise to annihilation signals during CMB and inside haloes today. We consider dark matter with long-range interactions, in particular dark matter coupled to a light vector or scalar force mediator. We compute the couplings required to attain a final antiparticle-to-particle ratio after the thermal freeze-out of the annihilation processes in the early universe, and then estimate the late-time annihilation signals. We show that, due to the Sommerfeld enhancement, highly asymmetric dark matter with long-range interactions can have a significant annihilation rate, potentially larger than symmetric dark matter of the same mass with contact interactions. We discuss caveats in this estimation, relating to the formation of stable bound states. Finally, we consider the non-relativistic partial-wave unitarity bound on the inelastic cross-section, we discuss why it can be realised only by long-range interactions, and showcase the importance of higher partial waves in this regime of large inelasticity. We derive upper bounds on the mass of symmetric and asymmetric thermal-relic dark matter for s-wave and p-wave annihilation, and exhibit how these bounds strengthen as the dark asymmetry increases.Comment: 31 pages, 8 figures. V2: small corrections, added discussion and reference

Daylight compliance of multi-dwelling apartment blocks : Design considerations, evaluation criteria and occupant responses

This thesis examines the daylight compliance of residential spaces, in particular apartments in multi-dwelling building blocks, and provides knowledge that may prove useful for the development of future daylight criteria for dwellings. The implications of design choices on daylight compliance of spaces and the effect of daylight criteria on the level of compliance are at the core of this work. Daylight simulations were performed to evaluate a large sample of representative apartment buildings according to past and present daylight criteria. Self-administered questionnaires were also used to investigate occupant preferences and subjective impressions of daylight conditions in the dwellings. The simulations and questionnaires divide this work into two parts, which are connected on the basis of the same study object: multi-dwelling buildings.The first part includes a review of daylight regulations in Sweden from the time the term “daylight” first appeared in 1960. It proceeds with compliance testing results for a large sample of multi-dwelling blocks, evaluated according to the current Swedish daylight compliance criteria. Several criteria commonly used internationally are assessed for the same spaces, to evaluate compliance differences when using different criteria. The review concludes that there has been no significant progress in Swedish daylight regulations since 1975, when the basis for the current daylight factor criterion was first formulated. It also argues that the current geometric criterion has limitations due to spatial implications deriving from its formulation. The compliance testing results indicate that Swedish daylight criteria have not been successful in safeguarding daylight access for residential spaces historically, especially in denser urban areas, perhaps because they were expressed as “general recommendations” instead of “mandatory provisions”. To this end, several buildings built prior to the introduction of daylight criteria, and built only by architectural intuition, perform better than regulated buildings. A more detailed assessment of the investigated rooms using additional criteria indicated which building types perform better overall, which geometric attributes are more significant for compliance, and the effect of urban density on compliance.The second part includes results from a questionnaire survey carried out in the city of Malmö, the third largest city in Sweden. The questionnaires were distributed in buildings of the same block typologies as the buildings evaluated via simulations in the first part of this research. This second part concerns daylight perception, electric lighting use, and occupant preferences with respect to daylighting among room types. The questionnaire rating scales were validated for their suitability as a form of measurement for daylight surveys. The reported electric lighting use was compared between different room types, geometries, and facade orientations to evaluate whether there is less use of lighting in rooms with specific characteristics. The relation between reported daylit area and electric lighting use was analysed to assess whether daylight availability can yield reductions in electric light use, to what extent, and under which conditions. The survey also revealed clear occupant preferences, indicating the room types where daylight availability is prioritised