York University

About: York University is a education organization based out in Toronto, Ontario, Canada. It is known for research contribution in the topics: Population & Politics. The organization has 18899 authors who have published 43357 publications receiving 1568560 citations.

Dark Matter Halos as Particle Colliders: Unified Solution to Small-Scale Structure Puzzles from Dwarfs to Clusters

Abstract: Astrophysical observations spanning dwarf galaxies to galaxy clusters indicate that dark matter (DM) halos are less dense in their central regions compared to expectations from collisionless DM N-body simulations. Using detailed fits to DM halos of galaxies and clusters, we show that self-interacting DM (SIDM) may provide a consistent solution to the DM deficit problem across all scales, even though individual systems exhibit a wide diversity in halo properties. Since the characteristic velocity of DM particles varies across these systems, we are able to measure the self-interaction cross section as a function of kinetic energy and thereby deduce the SIDM particle physics model parameters. Our results prefer a mildly velocity-dependent cross section, from σ/m≈2 cm^{2}/g on galaxy scales to σ/m≈0.1 cm^{2}/g on cluster scales, consistent with the upper limits from merging clusters. Our results dramatically improve the constraints on SIDM models and may allow the masses of both DM and dark mediator particles to be measured even if the dark sector is completely hidden from the standard model, which we illustrate for the dark photon model.

Dark Matter Self-interactions and Small Scale Structure

Abstract: We review theories of dark matter (DM) beyond the collisionless paradigm, known as self-interacting dark matter (SIDM), and their observable implications for astrophysical structure in the Universe. Self-interactions are motivated, in part, due to the potential to explain long-standing (and more recent) small scale structure observations that are in tension with collisionless cold DM (CDM) predictions. Simple particle physics models for SIDM can provide a universal explanation for these observations across a wide range of mass scales spanning dwarf galaxies, low and high surface brightness spiral galaxies, and clusters of galaxies. At the same time, SIDM leaves intact the success of $\Lambda$CDM cosmology on large scales. This report covers the following topics: (1) small scale structure issues, including the core-cusp problem, the diversity problem for rotation curves, the missing satellites problem, and the too-big-to-fail problem, as well as recent progress in hydrodynamical simulations of galaxy formation; (2) N-body simulations for SIDM, including implications for density profiles, halo shapes, substructure, and the interplay between baryons and self-interactions; (3) semi-analytic Jeans-based methods that provide a complementary approach for connecting particle models with observations; (4) merging systems, such as cluster mergers (e.g., the Bullet Cluster) and minor infalls, along with recent simulation results for mergers; (5) particle physics models, including light mediator models and composite DM models; and (6) complementary probes for SIDM, including indirect and direct detection experiments, particle collider searches, and cosmological observations. We provide a summary and critical look for all current constraints on DM self-interactions and an outline for future directions.

The Changing Nature of Professional Control

Abstract: The traditional view of the professions is that they are largely free of the hierarchical forms of social control characteristic of other kinds of occupations; instead, they are self-regulating, subject only to informal collegial control. As a result of events in the past few decades in the United States, analysts now believe that the traditional autonomy of professions is eroding. This paper reviews two theories that emphasize this process, one focusing on deprofessionalization and the other on proletarianization. It concludes that the available evidence does not support either theory sufficiently to make them analytically useful; it advances an alternate theory that emphasizes the formalization of professional social control. This third viewpoint is based on the finding that the professions—as corporate bodies—have remained relatively autonomous. Antitrust decisions, political pressure to exercise more control over errant members, and the administrative requirement of greater accountability in large org...

Accounting as reality construction: towards a new epistemology for accounting practice*

Abstract: Accountants often see themselves as objective appraisers of reality, representing reality “as is”. This paper takes a different view, arguing that accountants typically construct reality in limited and one-sided ways. It shows that the idea of objectivity in accounting is largely a myth, and one which stands in the way of interesting future developments in the discipline. The paper develops an alternative perspective on the nature of the accounting process, building on insights regarding the interpretive and metaphorical nature of accounting, and arguing that accounting should be approached as a form of “dialogue” through which accountants can construct, “read” and probe situations in a variety of ways.

Compensatory conviction in the face of personal uncertainty: going to extremes and being oneself.

Abstract: Study 1 participants' self-integrity (C. M. Steele. 1988) was threatened by deliberative mind-set (S. E. Taylor & P. M. Gollwitzer, 1995) induced uncertainty. They masked the uncertainty with more extreme conviction about social issues. An integrity-repair exercise after the threat, however, eliminated uncertainty and the conviction response. In Study 2, the same threat caused clarified values and more self-consistent personal goals. Two other uncertainty-related threats, mortality salience and temporal discontinuity, caused similar responses: more extreme intergroup bias in Study 3, and more self-consistent personal goals and identifications in Study 4. Going to extremes and being oneself are seen as 2 modes of compensatory conviction used to defend against personal uncertainty. Relevance to cognitive dissonance and authoritarianism theories is discussed, and a new perspective on terror managenment theory (J. Greenberg, S. Solomom, & T. Pyszczynski, 1997) is proposed.