Suppression of superconductivity by Neel-type magnetic fluctuations in the iron pnictides

Motivated by recent experimental detection of Neel-type ($(\pi,\pi)$) magnetic fluctuations in some iron pnictides, we study the impact of competing $(\pi,\pi)$ and $(\pi,0)$ spin fluctuations on the superconductivity of these materials. We show that, counter-intuitively, even short-range, weak Neel fluctuations strongly suppress the $s^{+-}$ state, with the main effect arising from a repulsive contribution to the $s^{+-}$ pairing interaction, complemented by low frequency inelastic scattering. Further increasing the strength of the Neel fluctuations leads to a low-$T_{c}$ d-wave state, with a possible intermediate $s+id$ phase. The results suggest that the absence of superconductivity in a series of hole-doped pnictides is due to the combination of short-range Neel fluctuations and pair-breaking impurity scattering, and also that $T_{c}$ of optimally doped pnictides could be further increased if residual $(\pi,\pi)$ fluctuations were reduced.Comment: revised version accepted for publication in PR

Are Financial Assets Priced Locally or Globally?

We review the international finance literature to assess the extent to which international factors affect financial asset demands and prices. International asset pricing models with mean-variance investors predict that an asset's risk premium depends on its covariance with the world market portfolio and, possibly, with exchange rate changes. The existing empirical evidence shows that a country's risk premium depends on its covariance with the world market portfolio and that there is some evidence that exchange rate risk affects expected returns. However, the theoretical asset pricing literature relying on mean-variance optimizing investors fails in explaining the portfolio holdings of investors, equity flows, and the time-varying properties of correlations across countries. The home bias has the effect of increasing local influences on asset prices, while equity flows and cross-country correlations increase global influences on asset prices.

Global Market Integration and National Sovereignty

In this paper, we first trace the evolution of the global trading system from the 19th century to the present-day GATT/WTO arrangements, calling attention to the key roles of reciprocity and nondiscrimination, and we note how the system is now challenged by the new paradigm of global market integration. We then consider the recent plethora of free trade agreements (FTAs), including those between industrial and developing countries, and their uneasy relationship with a multilateral system based on non-discrimination.. Thereafter, we seek to identify the boundaries of the WTO and examine how the potential expansion of these boundaries extension and weakening of the effectiveness and influence of the WTO.Reciprocity, Non-Discrimination; Boundaries of WTO Regime

Stereo and motion parallax cues in human 3D vision: can they vanish without a trace?

In an immersive virtual reality environment, subjects fail to notice when a scene expands or contracts around them, despite correct and consistent information from binocular stereopsis and motion parallax, resulting in gross failures of size constancy (A. Glennerster, L. Tcheang, S. J. Gilson, A. W. Fitzgibbon, & A. J. Parker, 2006). We determined whether the integration of stereopsis/motion parallax cues with texture-based cues could be modified through feedback. Subjects compared the size of two objects, each visible when the room was of a different size. As the subject walked, the room expanded or contracted, although subjects failed to notice any change. Subjects were given feedback about the accuracy of their size judgments, where the “correct” size setting was defined either by texture-based cues or (in a separate experiment) by stereo/motion parallax cues. Because of feedback, observers were able to adjust responses such that fewer errors were made. For texture-based feedback, the pattern of responses was consistent with observers weighting texture cues more heavily. However, for stereo/motion parallax feedback, performance in many conditions became worse such that, paradoxically, biases moved away from the point reinforced by the feedback. This can be explained by assuming that subjects remap the relationship between stereo/motion parallax cues and perceived size or that they develop strategies to change their criterion for a size match on different trials. In either case, subjects appear not to have direct access to stereo/motion parallax cues

The Impact of the Introduction of the Euro on Foreign Exchange Rate Risk Exposures

This paper examines whether the introduction of the Euro in 1999 was associated with lower stock return volatility, market risk exposures and foreign exchange rate risk exposures for 12,821 nonfinancial firms in Europe, the United States, and Japan. We show that though the Euro led to a significant decrease in the volatility of trade-weighted exchange rates of European countries, stock return variances of nonfinancial firms increased after its introduction. However, the Euro was also accompanied by significant reductions in market risk exposures for nonfinancial firms in and outside of Europe. We show that the reduction in market risk was not as a result of changes in financial leverage, and that it is concentrated in firms with a high fraction of foreign sales in Europe, a high fraction of total foreign sales and larger market capitalizations. In addition to its impact on market betas, the Euro has a positive effect on the incremental foreign exchange rate exposures, particularly for multinationals.Foreign exchange rates, exposure, Euro, corporate finance, risk management, derivatives

Fairness in the WTO Trading System

We first provide a brief critique of the utilitarian principle as a guide to fairness in the world trading system. We then turn to the alternative conception of fairness in terms of economic equity, exploring the meaning of its two components: equality of opportunity and distributive justice. We thereafter proceed to discuss the conditions of autonomy and reciprocity that have to be met in order to realize greater fairness in multilateral trade negotiations. Next, we comment on aspects of procedural justice that are necessary for the functioning of a fair trading system. Finally, we conclude with an overall assessment of the considerations of the fairness achieved in the Uruguay Round multilateral negotiations.Fairness, Equality of Opportunity, Distributive Justice, Global Trading System

What Are the Issues in Using Trade Agreements for Improving International Labor Standards?

This paper addresses the issues of whether the linking of core labor standards with multilateral or bilateral trade agreements is an effective way of promoting the improvement of labor standards. We review the determinants of core labor standards over time and conclude that efforts to improve these standards have to be tailored to the economic and social circumstances prevailing in a country at a specific time. Legalistic means to prod governments into revising their domestic laws or enforcing them will therefore be unsuccessful unless economic incentives can be changed to erode prevailing social norms and ease the way for the acceptance of new norms that will meet with public approval and be consonant with the distribution of political power. Moral suasion from both domestic and external sources may work more slowly than more legalistic means but is preferred because it contributes to altering the social norms that underlie and will reinforce the acceptance and effectiveness of labor standards.International labor standards, social norms, trade agreements

Impedance of a sphere oscillating in an elastic medium with and without slip

The dynamic impedance of a sphere oscillating in an elastic medium is considered. Oestreicher's formula for the impedance of a sphere bonded to the surrounding medium can be expressed simply in terms of three lumped impedances associated with the displaced mass and the longitudinal and transverse waves. If the surface of the sphere slips while the normal velocity remains continuous, the impedance formula is modified by adjusting the definition of the transverse impedance to include the interfacial impedance.Comment: 10 pages, 2 figure