Potts Model On Random Trees

We study the Potts model on locally tree-like random graphs of arbitrary degree distribution. Using a population dynamics algorithm we numerically solve the problem exactly. We confirm our results with simulations. Comparisons with a previous approach are made, showing where its assumption of uniform local fields breaks down for networks with nodes of low degree.Comment: 10 pages, 3 figure

Public-Private Partnerships as Collaborative Projects: testing the theory on cases from EU and Russia

Public-private partnerships (PPP) allow involvement of private parties in the provision of public goods. How does this differ from traditional public procurement? We view PPPs as collaborative projects with information frictions. Typical public procurement contracts tackle the problems of asymmetric information. However, not all projects are contractible; some are not profitable enough to ensure participation of the private partner. This is due, in part, to costly information verification, and in part to the profitability requirements of the private party. We demonstrate what specific features of a partnership can improve feasibility of projects, and thus both provide a justification of PPP as a form of public good provision, and demonstrate how and whether it differs from procurement. We then analyse real life examples of PPP projects from the perspective of optimal choice of contracts, involvement of both partners, and the features that make these PPP arrangements superior to public procurement

Connecting nonlinear normal modes to the forced response of a geometric nonlinear structure with closely spaced modes

This paper numerically and experimentally investigates the relationship between the nonlinear normal modes and the forced response of a clamped-clamped cross beam structure. The system possesses closely-spaced linear modes such that the applied force distribution across the structure plays a central role in the appropriation of the nonlinear normal modes. Numerical simulations show that the quadrature conditions of the forced response does not necessarily match the peak response nor the nonlinear normal modes of the underlying conservative system, but instead are dependent upon the applied excitation. Experimental investigations performed with a single-point excitation and control based continuation further demonstrate the necessity for appropriate forcing in order to extract the NNMs of such systems.</p

Spin-spin Correlation in Some Excited States of Transverse Ising Model

We consider the transverse Ising model in one dimension with nearest-neighbour interaction and calculate exactly the longitudinal spin-spin correlation for a class of excited states. These states are known to play an important role in the perturbative treatment of one-dimensional transverse Ising model with frustrated second-neighbour interaction. To calculate the correlation, we follow the earlier procedure of Wu, use Szego's theorem and also use Fisher-Hartwig conjecture. The result is that the correlation decays algebraically with distance ($n$) as $1/\surd n$ and is oscillatory or non-oscillatory depending on the magnitude of the transverse field.Comment: 5 pages, 1 figur

Associação de controle químico e da resistência varietal para redução da trnasmissão de begomovírus ao tomateiro.

Neste trabalho avaliou-se a associação do controle químico de Bemisia tabaci biótipo B com o uso de cultivar tolerante aos begomovírus na incidência de Tomato severe rugose virus - ToSRV e na severidade da doença em tomateiro.Resumo 2

Complete Break Up of Ortho Positronium (Ps)- Hydrogenic ion System

The dynamics of the complete breakup process in an Ortho Ps - He+ system including electron loss to the continuum (ELC) is studied where both the projectile and the target get ionized. The process is essentially a four body problem and the present model takes account of the two centre effect on the electron ejected from the Ps atom which is crucial for a proper description of the ELC phenomena. The calculations are performed in the framework of Coulomb Distorted Eikonal Approximation. The exchange effect between the target and the projectile electron is taken into account in a consistent manner. The proper asymptotic 3-body boundary condition for this ionization process is also satisfied in the present model. A distinct broad ELC peak is noted in the fully differential cross sections (5DCS) for the Ps electron corroborating qualitatively the experiment for the Ps - He system. Both the dynamics of the ELC from the Ps and the ejected electron from the target He+ in the FDCS are studied using coplanar geometry. Interesting features are noted in the FDCS for both the electrons belonging to the target and the projectile.Comment: 14 pages,7 figure

Correlations in interacting systems with a network topology

We study pair correlations in cooperative systems placed on complex networks. We show that usually in these systems, the correlations between two interacting objects (e.g., spins), separated by a distance $\ell$, decay, on average, faster than $1/(\ell z_\ell)$. Here $z_\ell$ is the mean number of the $\ell$-th nearest neighbors of a vertex in a network. This behavior, in particular, leads to a dramatic weakening of correlations between second and more distant neighbors on networks with fat-tailed degree distributions, which have a divergent number $z_2$ in the infinite network limit. In this case, only the pair correlations between the nearest neighbors are observable. We obtain the pair correlation function of the Ising model on a complex network and also derive our results in the framework of a phenomenological approach.Comment: 5 page