Magnetic quantum phase transition in an anisotropic Kondo lattice

The quantum phase transition between paramagnetic and antiferromagnetic phases of the Kondo lattice model with Ising anisotropy in the intersite exchange is studied within the framework of extended dynamical mean-field theory. Nonperturbative numerical solutions at zero temperature point to a continuous transition for both two- and three-dimensional magnetism. In the former case, the transition is associated with critical local physics, characterized by a vanishing Kondo scale and by an anomalous exponent in the dynamics close in value to that measured in heavy-fermion CeCu_{5.9}Au_{0.1}.Comment: 4 pages, 3 figures. Version published in Phys. Rev. Let

Temptation and self-control: some evidence and applications

This paper studies the empirical relevance of temptation and self-control using household-level data from the Consumer Expenditure Survey. We estimate an infinite-horizon consumption-savings model that allows, but does not require, temptation and self-control in preferences. To help identify the presence of temptation, we exploit an implication of the theory that a tempted individual has a preference for commitment. In the presence of temptation, the cross-sectional distribution of the wealth-consumption ratio, in addition to that of consumption growth, becomes a determinant of the asset-pricing kernel, and the importance of this additional pricing factor depends on the strength of temptation. The estimates that we obtain provide statistical evidence supporting the presence of temptation. Based on our estimates, we explore some quantitative implications of this class of preferences on equity premium and on the welfare cost of business cycles.Asset pricing ; Welfare

The Value of Information Technology in E-Business Environments: The Missing Links in the Renewed IT Value Debate

After more than a decade of intensive studies, business value of information technology continues to generate interest and debate among both academics and practitioners. Drawing upon the IT value literature and the resource-based view of the firm, we develop a process-oriented model of IT value creation in the context of electronic business. Instead of a dichotomous measure of “adoption vs. non-adoption” as typically found in the literature, this model incorporates three stages (investment–usage–value) of the diffusion process at the firm level, with actual usage being an important mediating variable. The model also includes both IT resources and organizational factors, and tests the complementarity between them. A large-scale international dataset, involving 2,139 firms from 10 countries, is used to test the theoretical model. After controlling for firm size and industry effects, our empirical analyses based on structural equation modeling have shown that the investment–usage–value linkages are significant (although the direct link between investment and value is weak), suggesting that usage would be a “missing link” if not included. Another finding is that, while IT still matters (especially deeper use of IT such as back-end integration), complementary organizational resources (e.g., management support and external relationships) are found to be highly significant in creating value from e-business investment. On the other hand, these relationships tend to be moderated by environmental factors. These findings contribute to the ongoing debate over IT value—in this case, the value of Internet technologies in the e-business environment. They also offer important implications for the way firms approach IT investment and management in the post-bubble Internet era

PRO-COMPETITION PUBLIC POLICY IN NETWORK MARKETS WITH SWITCHING COSTS: EVIDENCE FROM “MOBILE NUMBER PORTABILITY” IN WIRELESS TELECOMMUNICATIONS INDUSTRY

Does public policy designed to promote market competition indeed achieve the intended consequence? Using the wireless industry as a testing field, this paper examines this question by focusing on the impact of mobile number portability (MNP) regulation on competition. We first construct a switching-costs model in which market growth rate and initial market structure are two salient industry characteristics. Guided by the analytical predictions, we analyze quarterly panel data of 218 major wireless operators in 52 countries from 2003-2009. We find relative market share gains for small firms under MNP, especially in markets with higher growth rate and lower concentration. Yet, surprisingly, large firms still manage to enjoy greater profit after MNP. We interpret the conundrum of “market share convergence” and “profit divergence” with customer base composition. Our method of analyzing asymmetric MNP effect in a cross-country context is applicable to public policy analysis in other industries