Non-radial instabilities and progenitor asphericities in core-collapse supernovae

Since core-collapse supernova simulations still struggle to produce robust neutrino-driven explosions in 3D, it has been proposed that asphericities caused by convection in the progenitor might facilitate shock revival by boosting the activity of non-radial hydrodynamic instabilities in the post-shock region. We investigate this scenario in depth using 42 relativistic 2D simulations with multigroup neutrino transport to examine the effects of velocity and density perturbations in the progenitor for different perturbation geometries that obey fundamental physical constraints (like the anelastic condition). As a framework for analysing our results, we introduce semi-empirical scaling laws relating neutrino heating, average turbulent velocities in the gain region, and the shock deformation in the saturation limit of non-radial instabilities. The squared turbulent Mach number, 〈Ma2〉, reflects the violence of aspherical motions in the gain layer, and explosive runaway occurs for 〈Ma2〉 ≳ 0.3, corresponding to a reduction of the critical neutrino luminosity by ∼25∼25 per cent compared to 1D. In the light of this theory, progenitor asphericities aid shock revival mainly by creating anisotropic mass flux on to the shock: differential infall efficiently converts velocity perturbations in the progenitor into density perturbations δρ/ρ at the shock of the order of the initial convective Mach number Maprog. The anisotropic mass flux and ram pressure deform the shock and thereby amplify post-shock turbulence. Large-scale (ℓ = 2, ℓ = 1) modes prove most conducive to shock revival, whereas small-scale perturbations require unrealistically high convective Mach numbers. Initial density perturbations in the progenitor are only of the order of Ma2progMaprog2 and therefore play a subdominant role.

Domestic Violence Perpetrators - Evidence informed responses

Domestic violence is a serious, widespread public, social and health problem that affects the lives of many women, children and men. There is also evidence to suggest it has one of the highest rates of recidivism. This comprehensive book provides an overview of what the research tells us about the perpetrators of domestic violence and what works, and what doesn’t, in promoting positive change.

Collecting together the most up-to-date evidence from the international literature and bringing psychological, sociological, gendered and socio-political theoretical perspectives to bear on the issue, the book explores:
- what domestic violence is, why it happens and how it can be measured
- who the perpetrators of domestic violence are, including discussion of non-stereotypical patterns such as male victims, female perpetrators, couples where the abuse is mutual, and couples with abusive relationships who want the abuse to end but the relationship to be sustained
- strategies for engaging perpetrators in interventions and for promoting behaviour change
- evidence-informed interventions, programmes and policies for working with perpetrators
- where robust evidence is lacking and more research needs to be undertaken.