Referral Networks and Inequality*

This is the first paper to study the interaction between labour markets and endogenous referral networks in the context of worker heterogeneity. In equilibrium the structure of the referral network is hierarchical, which is different from the usual assumption of homophily but is consistent with the evidence. Hierarchy exacerbates inequality. The welfare effects of the use of referrals are subtle and depend on the nature of heterogeneity. If heterogeneity is due to productivity differences, referrals improve welfare. If workers face different probability of forming a match despite having the same productivity, as in the case of discrimination, referrals reduce welfare.

Banks’ Risk Dynamics and Distance to Default

We adapt structural models of default risk to take into account the special nature of bank assets. The usual assumption of lognormally distributed asset values is not appropriate for banks. Typical bank assets are risky debt claims with concave payoffs. Because of the payoff nonlinearity, bank asset volatility rises following negative shocks to borrower asset values. As a result, standard structural models with constant asset volatility can severely understate banks’ default risk in good times when asset values are high. Additionally, bank equity return volatility is much more sensitive to negative shocks to asset values than in standard structural models.

The case of NGC 6302: the impact of shocks in the derivation of nitrogen abundances

ABSTRACT High nitrogen abundance is characteristic of Type I planetary nebulae, as well as their highly filamentary structure. In the present work, we test the hypothesis of shocks as a relevant excitation mechanism for a Type I nebula, NGC 6302, using recently released diagnostic diagrams to distinguish shocks from photoexcitation. The construction of the diagrams depends on emission-line ratios and kinematical information. NGC 6302 shows the relevance of shocks in peripheral regions and their importance to the whole nebula. Using shocks, we question the usual assumption of ionization correction factor calculation, justifying a warning regarding broadly used abundance derivation methods. From kinematical analysis, we derive a new distance for NGC 6302 of $805\pm 143\,$ pc.

The Harvard Manuscript of Keats's ‘On First Looking into Chapman's Homer’, Joseph Severn, Leigh Hunt, and its Transmission into Print

The recent discovery that Harvard's manuscript of ‘On First Looking into Chapman's Homer’ was in Joseph Severn's possession at his death questions the usual assumption that it was probably the manuscript Keats sent to Cowden Clarke. It further prompts a fresh consideration of the sonnet's manuscript circulation and Leigh Hunt's role in its transmission into print

Analytic Simulations of Packaging Cardboards with Non-Rigid Adhesives

The understanding of the cardboard performance is necessary to the design of packaging containers and the protection of their contents for safe deliveries. The use of adhesives is unavoidable in the manufacturing of the cardboards. Like all materials, the adhesives have finite stiffness but when used in the literature, they are assumed perfectly rigid. This study changes this assumption by using the real properties of adhesives. A closed-form solution for cardboard panelsassembled withnon-rigid adhesives, and subjected to edgewise loading is presented. The solution satisfies the equilibrium equations of the layers, the compatibility equations of stresses and strains at the interfaces, and the boundary conditions. To investigate the effects of the finite values of adhesivestiffness on the responses, numerical evaluations are conducted. The results obtained have shown that the adhesive stiffness has a strong effect on the performance. Beyond a certain level of stiffness, the usual assumption of perfect bonding used in classical theories is acceptable. This could provide an answer to what constitutes perfect bonding in terms of the ratio of the fluted layer, or simply flute, stiffness to the bonding stiffness.

Superrational types

We present a formal analysis of Douglas Hofstadter’s concept of superrationality. We start by defining superrationally justifiable actions, and study them in symmetric games. We then model the beliefs of the players, in a way that leads them to different choices than the usual assumption of rationality by restricting the range of conceivable choices. These beliefs are captured in the formal notion of type drawn from epistemic game theory. The theory of coalgebras is used to frame type spaces and to account for the existence of some of them. We find conditions that guarantee superrational outcomes.

Modelling of carving turns in alpine skiing

In this paper we analyse the model of carving turns in alpine skiing and snowboarding based on the usual assumption of approximate balance between forces and torques acting on the skier during the turn. The approximation of torque balance yields both lower and upper limits on the skier speed, which depend only on the sidecut radius of skis and the slope gradient. We use the model to simulate carving runs on slopes of constant gradient and find that pure carving is possible only on relatively flat slopes, with the critical slope angle in the range of 8°-20°. The exact value depends mostly on the coefficient of snow friction and to a lesser degree on the sidecut radius of skis. Comparison with the practice of ski racing shows that the upper speed limit and the related upper limit on the slope gradient set by the model are too restrictive and so must be the assumption of torque balance used in the model. A more advanced theory is needed.

Civil disobedience

According to common definitions, civil disobedience involves a public and nonviolent breach of law that is committed in order to change a law or policy, and in order to better society. More, those classed as civilly disobedient must be willing to accept punishment. Why is the categorization of what counts as civil disobedience of practical importance? The usual assumption is that acts of civil disobedience are easier to justify morally than other illegal acts. Acts of civil disobedience, such as those committed by abolitionists, by followers of Mahatma Gandhi and Martin Luther King, Jr and by opponents of the Vietnam War, have been an important form of social protest. The decision as to what exactly should count as civil disobedience should be guided both by an ordinary understanding of what the term conveys and by what factors are relevant for moral justification. For justification, nonviolence and publicness matter because they reduce the damage of violating the law. Tactics should be proportionate to the evil against which civil disobedience is aimed; someone who assesses the morality of a particular act of civil disobedience should distinguish an evaluation of tactics from an evaluation of objectives.

Forget the Competition Trope

The current debate on internationalization has revolved around the impacts of nationalist politics in many countries on student mobility. In recent research, we have questioned the usual assumption that major host countries have been engaged in an ongoing “brain race.” Through an analysis of the politics and public policies impacting international students in Australia, Canada, England, and the United States during a sixteen year period, we show that there is no clear pattern of “competition” among countries, but rather uncoordinated and inconsistent actions.

Forget the Competition Trope

The current debate on internationalization has revolved around the impacts of nationalist politics in many countries on student mobility. In recent research, we have questioned the usual assumption that major host countries have been engaged in an ongoing “brain race.” Through an analysis of the politics and public policies impacting international students in Australia, Canada, England, and the United States during a sixteen year period, we show that there is no clear pattern of “competition” among countries, but rather uncoordinated and inconsistent actions.