Dynamical evolution of star forming regions - II. Basic kinematics

We follow the dynamical evolution of young star-forming regions with a wide range of initial conditions and examine how the radial velocity dispersion, $\sigma$, evolves over time. We compare this velocity dispersion to the theoretically expected value for the velocity dispersion if a region were in virial equilibrium, $\sigma_{\rm vir}$ and thus assess the virial state ($\sigma / \sigma_{\rm vir}$) of these systems. We find that in regions that are initially subvirial, or in global virial equilibrium but subvirial on local scales, the system relaxes to virial equilibrium within several million years, or roughly 25 - 50 crossing times, according to the measured virial ratio. However, the measured velocity dispersion, $\sigma$, appears to be a bad diagnostic of the current virial state of these systems as it suggests that they become supervirial when compared to the velocity dispersion estimated from the virial mass, $\sigma_{\rm vir}$. We suggest that this discrepancy is caused by the fact that the regions are never fully relaxed, and that the early non-equilibrium evolution is imprinted in the one-dimensional velocity dispersion at these early epochs. If measured early enough ($<$2 Myr in our simulations, or $\sim$20 crossing times), the velocity dispersion can be used to determine whether a region was highly supervirial at birth without the risk of degeneracy. We show that combining $\sigma$, or the ratio of $\sigma$ to the interquartile range (IQR) dispersion, with measures of spatial structure, places stronger constraints on the dynamical history of a region than using the velocity dispersion in isolation.Comment: 20 pages, 14 figures, accepted for publication in MNRA

Property A and exactness of the uniform Roe algebra

In this short note, prepared for the volume of conjectures to celebrate Guido Mislin's retirement, we outline the conjecture that a uniformly discrete bounded geometry metric space X has property A if and only if the uniform Roe algebra C^?(X ) is exact

Post-Brexit, would Whitehall be able to rise to the challenge of negotiating the best possible deal?

Much will be expected of the civil service if Britain votes to leave the EU. Every Whitehall department and diplomats in Brussels will be embroiled in complex negotiations to thrash out a series of new relationships. Without additional resources and expertise, the UK’s ability to obtain the best possible deal may be hampered, writes Nicholas Wright

Theresa Villiers wants Northern Ireland out of the EU. That stance may be untenable

Theresa Villiers, the Northern Ireland Secretary, is campaigning to leave the EU – a step that would have profound ramifications for the region. A formal land border between Northern Ireland and Eire would have to be reintroduced, trade would be affected and the EU funding that has helped the region recover from the Troubles would end. Nicholas Wright argues that, as the campaign goes on, Villiers’ position may become untenable

Squeezed mandarins: the four big challenges facing the civil service

Will the UK civil service be able to deliver Brexit alongside the efficient day-to-day provision of public services and the government’s manifesto commitments? A recent National Audit Office report identified three challenges facing Whitehall – complexity, capacity and feasibility – to which Nicholas Wright adds a fourth: trust. The suspicion that civil servants are not wholly persuaded by the case for Brexit could prove toxic

Achieving a ‘good’ Brexit: what David Cameron needs to do now

While formal exit negotiations cannot begin until Britain triggers Article 50, a three-month hiatus while the Conservatives selects a new prime minister will make it harder to achieve a ‘good’ Brexit. With our European partners and the Scottish government already laying down markers for their vision of the future, London risks ceding the initiative before the process has even begun, warns Nicholas Wright. He sets out the practical steps David Cameron should take to prepare for the forthcoming negotiations

UK foreign policy in the Biden era: an opportunity for the UK to re-establish itself post-Brexit as a credible international partner

What will the Biden Administration mean for UK foreign policy? Despite Boris Johnson’s political closeness to Donald Trump, Nicholas Wright argues that the opportunity exists for an important reset in British foreign policy based on strengthened UK-US ties, enabling the UK to demonstrate a renewed international commitment post-Brexit. To do so, though, the UK must also urgently address longer-term challenges that have impacted on its international credibility and relevance for the last decade

HIGHER EDUCATION POLICIES AND STUDENTS\u27 BEHAVIOR

This dissertation examines the impact of need-based financing policies, performance standards, and public recognition on college students\u27 outcomes over time. Each essay utilizes novel administrative student-level data from Jamaica and a quasi-experimental econometric design to identify the causal impact of these college-level interventions on students\u27 behavior. The general objective of this work is to provide credible evidence that can help policymakers create more effective policies to improve student success. Designing an effective framework for financing higher education is a major issue facing policymakers in developed and developing countries. While we have a good understanding of how college financing options affect college students\u27 behavior in developed countries, less is known about the impact of these programs in developing countries. Chapter 1 examines the impact of need-based student loan and grant financing policies on students college and labor market outcomes in a developing country. The results indicate that the students affected by either program had a higher GPA, were more likely to remain in college beyond their third year, and graduated at a higher rate. While both programs induced treated students to reduce their labor market engagement during college, the estimates suggest that grant recipients earned more and loan recipients earned less than comparable students in the early years after expected graduation. Chapter 2 examines how college initiatives that ascribe public recognition or written reprimand to a set standard of academic performance impact students academic decision-making. Many colleges utilize programs such as a Dean\u27s list and academic probation as mediums to encourage student success. These policies impose a future cost on affected students, either through the loss of acquired benefits or the threat of expulsion if they fail to perform above an established standard in future semesters. To meet these standards, treated students may be induced into exerting more effort in subsequent semesters. In addition, they have an incentive to manipulate their behavior along non-effort dimensions, such as through the type of courses and/or instructors they select. Using a regression discontinuity design, I find that the students who are treated by either the Dean’s list or academic probation policy improve their academic performance in subsequent semesters. However, increased effort may not be the only mechanisms through which students change their behavior following treatment. In particular, there is evidence that the Dean\u27s list policy induces treated students to select courses and instructors that are more likely to award higher grades and have a lower failure rate. Similarly, the results suggest that the academic probation policy causes students to switch majors and to employ what resembles a maximin strategy for expected grades when choosing courses