On the Lattice Corrections to the Free Energy of Kink-Bearing Nonlinear One-Dimensional Scalar Systems

A ri proof of the effective potential (lattice corrections included) deduced by Trullinger and Sasaki is given. Using asymptotic methods from the theory of differential equations depending on a large parameter, the lattice corrections to the kink and kink-kink contributions to the free energy are calculated. The results are in complete agreement with a first order correction to the energy of the static kink.Comment: 12 pages,plainte

Understanding the Nature and Effects of Police-Citizen Encounters in Social Context: The Road Less Traveled

Aggressive policing tactics have been identified as contributors to declining crime rate trends in urban, culturally diverse neighborhoods. They encompass stop and frisk practices which have spawned negative public opinion that contrasts with its justification by criminal justice officials as an effective means for the control and prevention of crime. The issue, however, begs deeper questions not readily addressed: how does the nature of police-citizen suspicion-based encounters influence the attitudes and behavior of both stakeholders; and does it contribute to effective crime control and prevention? Based on an analysis of theoretical and empirical research in the field, this article argues that a sense of shame and perception of fairness or unfairness are endemic to face-to-face suspicion-based encounters between police officers and the public, and have significant implications for the experience of justice, control and prevention of crime, and policy initiatives to promote community safety

Statistical approach of the modulational instability of the discrete self-trapping equation

The discrete self-trapping equation (DST) represents an useful model for several properties of one-dimensional nonlinear molecular crystals. The modulational instability of DST equation is discussed from a statistical point of view, considering the oscillator amplitude as a random variable. A kinetic equation for the two-point correlation function is written down, and its linear stability is studied. Both a Gaussian and a Lorentzian form for the initial unperturbed wave spectrum are discussed. Comparison with the continuum limit (NLS equation) is done.Comment: 10 page

Buyer-Seller Relationships in International Trade: Evidence from U.S. States' Exports and Business-Class Travel

International trade has become increasingly dependent on the transmission of complex information, often realized via face-to-face communication. This paper provides novel evidence for the importance of in-person business meetings in international trade. Interactions among trade partners entail a fixed cost of trade, but at the same time they generate relationship capital, which adds bilateral specific value to the traded products. Differences in the face-to-face communication intensity of traded goods, bilateral travel costs and foreign market size determine the optimal amount of interaction between trade partners. Using U.S. state level data on international business-class air travel as a measure of in-person business meetings, I find robust evidence that the demand for business-class air travel is directly related to volume and composition of exports in differentiated products. I also find that trade flows in R&D intensive manufactures and goods facing contractual frictions are most dependent on face-to-face meetings. The econometric identification exploits the cross-state variation in bilateral exports and business-class air travelers by foreign country and time period, circumventing any spurious correlation induced by cross-country differences driving aggregate travel and trade patterns.state exports; air travel; fixed export cost; face-to-face communication; relationship intensity; tacit knowledge

Magnetic Monopole in Noncommutative Space-Time and Wu-Yang Singularity-Free Gauge Transformations

We investigate the validity of the Dirac Quantization Condition (DQC) for magnetic monopoles in noncommutative space-time. We use an approach which is based on an extension of the method introduced by Wu and Yang. To study the effects of noncommutativity of space-time, we consider the gauge transformations of $U_\star(1)$ gauge fields and use the corresponding deformed Maxwell's equations. Using a perturbation expansion in the noncommutativity parameter $\theta$, we show that the DQC remains unmodified up to the first order in the expansion parameter. The result is obtained for a class of noncommutative source terms, which reduce to the Dirac delta function in the commutative limit.Comment: 18 pages. Relation to relevant literature clarified in the conclusions, 6 references adde