Forms of Relativistic Dynamics: What Are the Possibilities?

Various methods of constructing solvable few-body models are reviewed, with an emphasis on direct interactions with few degrees of freedom, as an alternative to the use of local quantum field theories. Several applications are discussed.Comment: 13 p

Expectations and Contagion in Self-Fulfilling Currency Attacks

This paper shows how expectations-driven contagion of currency crises can arise even if the currency market has a unique equilibrium when viewed in isolation. The model of Morris and Shin (1998) is extended to allow speculators to trade in a second currency market. If speculators believe that a devaluation of this other currency will make a domestic devaluation more likely, they will engage in trades that link the two markets. A sharp devaluation of the other currency will then be propagated to the domestic market and will increase the likelihood of a crisis there, fulfilling the original expectations. Even though this contagion is driven solely by expectations, the model places restrictions on observable variables, and these restrictions are broadly consistent with existing empirical evidence.

Lecture Notes on The Optimal Growth Problem

These notes provide an introduction to the study of optimal growth in the one-sector neoclassical growth model in continuous time. The model is developed using the analogy of Robinson Crusoe living on a deserted island. Both the Hamiltonian method and the phase diagram are presented and explained on an intuitive level. Some familiarity with optimization theory and differential equations, as well as a thorough understanding of intermediatelevel microeconomics, is assumed.Optimal Growth

Expectations and Contagion in Self-fulfilling Currency Attacks

This paper shows how expectations-driven contagion of currency crises can arise even if the currency market has a unique equilibrium when viewed in isolation. The model of Morris and Shin (1998) is extended to allow speculators to trade in a second currency market. If speculators believe that a devaluation of this other currency will make a domestic devaluation more likely, they will engage in trades that link the two markets. A sharp devaluation of the other currency will then be propagated to the domestic market and will increase the likelihood of a crisis there, fulfilling the original expectations. Even though this contagion is driven solely by expectations, the model places restrictions on observable variables, and these restrictions are broadly consistent with existing empirical evidenceContagion, Currency Crisis, Coordination, Global Games

Model tests of cluster separability in relativistic quantum mechanics

A relativistically invariant quantum theory first advanced by Bakamjian and Thomas has proven very useful in modeling few-body systems. For three particles or more, this approach is known formally to fail the constraint of cluster separability, whereby symmetries and conservation laws that hold for a system of particles also hold for isolated subsystems. Cluster separability can be restored by means of a recursive construction using unitary transformations, but implementation is difficult in practice, and the quantitative extent to which the Bakamjian-Thomas approach violates cluster separability has never been tested. This paper provides such a test by means of a model of a scalar probe in a three-particle system for which (1) it is simple enough that there is a straightforward solution that satisfies Poincar\'e invariance and cluster separability, and (2) one can also apply the Bakamjian-Thomas approach. The difference between these calculations provides a measure of the size of the corrections from the Sokolov construction that are needed to restore cluster properties. Our estimates suggest that, in models based on nucleon degrees of freedom, the corrections that restore cluster properties are too small to effect calculations of observables.Comment: 13 pages, 15 figure

"Family Structure, Race, and Wealth Ownership: A Longitudinal Exploration of Wealth Accumulation Processes"

Researchers have documented racial inequalities in wealth ownership and have offered a variety of explanations to account for these differences. One potentially important contributing factor that has received little attention is racial differences in family structure. This paper explores racial differences in the structure of family of origin and family in adulthood and examines the impact of these differences on wealth accumulation patterns. Using the National Longitudinal Survey of Youth, I find that large family size and family disruptions in childhood are negatively associated with wealth accumulation, portfolio behavior, and wealth mobility in adulthood. My analyses suggest that family size is a more important factor determining wealth accumulation for whites than for blacks or Hispanics and that family disruption is most strongly related to wealth outcomes for Hispanics. I find that family structure in adulthood is only modestly associated with overall wealth but strongly related to portfolio behavior and wealth mobility and that these relationships are relatively fixed across racial groups. My findings lend support to arguments about the importance of the role that resource dilution plays in determining life outcomes. They also suggest that efforts to reduce racial inequality in wealth ownership may be most effective if they seek to reduce the impact of deprivation early in life.

Family Structure, Race, and Wealth Ownership: A Longitudinal Exploration of Wealth Accumulation Processes

Researchers have documented racial inequalities in wealth ownership and have offered a variety of explanations to account for these differences. One potentially important contributing factor that has received little attention is racial differences in family structure. This paper explores racial differences in the structure of family of origin and family in adulthood and examines the impact of these differences on wealth accumulation patterns. Using the National Longitudinal Survey of Youth, I find that large family size and family disruptions in childhood are negatively associated with wealth accumulation, portfolio behavior, and wealth mobility in adulthood. My analyses suggest that family size is a more important factor determining wealth accumulation for whites than for blacks or Hispanics and that family disruption is most strongly related to wealth outcomes for Hispanics. I find that family structure in adulthood is only modestly associated with overall wealth but strongly related to portfolio behavior and wealth mobility and that these relationships are relatively fixed across racial groups. My findings lend support to arguments about the importance of the role that resource dilution plays in determining life outcomes. They also suggest that efforts to reduce racial inequality in wealth ownership may be most effective if they seek to reduce the impact of deprivation early in life.