Warm Dark Haloes Accretion Histories and their Gravitational Signatures

We study clusters in Warm Dark Matter (WDM) models of a thermally produced dark matter particle $0.5$ keV in mass. We show that, despite clusters in WDM cosmologies having similar density profiles as their Cold Dark Matter (CDM) counterparts, the internal properties, such as the amount of substructure, shows marked differences. This result is surprising as clusters are at mass scales that are {\em a thousand times greater} than that at which structure formation is suppressed. WDM clusters gain significantly more mass via smooth accretion and contain fewer substructures than their CDM brethren. The higher smooth mass accretion results in subhaloes which are physically more extended and less dense. These fine-scale differences can be probed by strong gravitational lensing. We find, unexpectedly, that WDM clusters have {\em higher} lensing efficiencies than those in CDM cosmologies, contrary to the naive expectation that WDM clusters should be less efficient due to the fewer substructures they contain. Despite being less dense, the larger WDM subhaloes are more likely to have larger lensing cross-sections than CDM ones. Additionally, WDM subhaloes typically reside at larger distances, which radially stretches the critical lines associated with strong gravitational lensing, resulting in excess in the number of clusters with large radial cross-sections at the $\sim2\sigma$ level. Though lensing profile for an individual cluster vary significantly with the line-of-sight, the radial arc distribution based on a sample of $\gtrsim100$ clusters may prove to be the crucial test for the presence of WDM.Comment: 13 pages, 14 figures, submitted to MNRA

Rethinking the space of ethics in social entrepreneurship: Power, subjectivity, and practices of freedom’

This article identifies power, subjectivity, and practices of freedom as neglected but significant elements for understanding the ethics of social entrepreneurship. While the ethics of social entrepreneurship is typically conceptualized in conjunction with innate properties or moral commitments of the individual, we problematize this view based on its presupposition of an essentialist conception of the authentic subject. We offer, based on Foucault’s ethical oeuvre, a practice-based alternative which sees ethics as being exercised through a critical and creative dealing with the limits imposed by power, notably as they pertain to the conditioning of the neoliberal subject. To this end, we first draw on prior research which looks at how practitioners of social enterprises engage with government policies that demand that they should act and think more like prototypical entrepreneurs. Instead of simply endorsing the kind of entrepreneurial subjectivity implied in prevailing policies, our results indicate that practitioners are mostly reluctant to identify themselves with the invocation of governmental power, often rejecting the subjectivity offered to them by discourse. Conceiving these acts of resistance as emblematic of how social entrepreneurs practice ethics by retaining a skeptical attitude toward attempts that seek to determine who they should be and how they should live, we introduce three vignettes that illustrate how practices of freedom relate to critique, the care for others, and reflected choice. We conclude that a practice-based approach of ethics can advance our understanding of how social entrepreneurs actively produce conditions of freedom for themselves as well as for others without supposing a ‘true self’ or a utopian space of liberty beyond power

Hidden from view: Coupled Dark Sector Physics and Small Scales

We study cluster mass dark matter haloes, their progenitors and surroundings in an coupled Dark Matter-Dark Energy model and compare it to quintessence and $\Lambda$CDM models with adiabatic zoom simulations. When comparing cosmologies with different expansions histories, growth functions & power spectra, care must be taken to identify unambiguous signatures of alternative cosmologies. Shared cosmological parameters, such as $\sigma_8$, need not be the same for optimal fits to observational data. We choose to set our parameters to $\Lambda$CDM $z=0$ values. We find that in coupled models, where DM decays into DE, haloes appear remarkably similar to $\Lambda$CDM haloes despite DM experiencing an additional frictional force. Density profiles are not systematically different and the subhalo populations have similar mass, spin, and spatial distributions, although (sub)haloes are less concentrated on average in coupled cosmologies. However, given the scatter in related observables ($V_{\rm max},R_{V_{\rm max}}$), this difference is unlikely to distinguish between coupled and uncoupled DM. Observations of satellites of MW and M31 indicate a significant subpopulation reside in a plane. Coupled models do produce planar arrangements of satellites of higher statistical significance than $\Lambda$CDM models, however, in all models these planes are dynamically unstable. In general, the nonlinear dynamics within and near large haloes masks the effects of a coupled dark sector. The sole environmental signature we find is that small haloes residing in the outskirts are more deficient in baryons than their $\Lambda$CDM counterparts. The lack of a pronounced signal for a coupled dark sector strongly suggests that such a phenomena would be effectively hidden from view.Comment: 13 pages, 14 figures, 2 tables, accepted for publication in MNRA