Mean-field limit for the stochastic Vicsek model

We consider the continuous version of the Vicsek model with noise, proposed as a model for collective behavior of individuals with a fixed speed. We rigorously derive the kinetic mean-field partial differential equation satisfied when the number N of particles tends to infinity, quantifying the convergence of the law of one particle to the solution of the PDE. For this we adapt a classical coupling argument to the present case in which both the particle system and the PDE are defined on a surface rather than on the whole space. As part of the study we give existence and uniqueness results for both the particle system and the PDE

The Codazzi Equation for Surfaces

In this paper we develop an abstract theory for the Codazzi equation on surfaces, and use it as an analytic tool to derive new global results for surfaces in the space forms {\bb R}^3, {\bb S}^3 and {\bb H}^3. We give essentially sharp generalizations of some classical theorems of surface theory that mainly depend on the Codazzi equation, and we apply them to the study of Weingarten surfaces in space forms. In particular, we study existence of holomorphic quadratic differentials, uniqueness of immersed spheres in geometric problems, height estimates, and the geometry and uniqueness of complete or properly embedded Weingarten surfaces

Topological Gravity on (D,N)−(D,N)-Shift Superspace Formulation

In this contribution, we re-assess the subject of topological gravity by following the Shift Supersymmetry formalism. The gauge-fixing of the theory goes under the Batallin-Vilkovisky (BV) prescription based on a diagram that contains both ghost and anti-ghost superfields, associated to the super-vielbein and the super-Lorentz connection. We extend the formulation of the topological gravity action to an arbitrary number of dimensions of the shift superspace by adopting a formulation based on the gauge-fixing for BF-type models

Managerial turnover and worker turnover

We study the influence of the manager's degree of consolidation within the firm over the firm's labor policy. We argue that non-consolidated (recently-appointed) managers are more worried about short-term results than consolidated managers are. This feature leads the former to bias the labor contracting favoring short-term contracts. This has two main consequences. First, a higher variation in the number of workers hired in each period. And second, a lower increase in unitary labor costs. To contrast these results, we use a database of 1.054 Spanish companies during the period (1994-98), and analyze their managerial turnover as well as their corresponding variation in the number of workers and in unitary labor costs. The theoretical results are confirmed, especially for highly-productive R and D-intensive firms

Impact of the Operations Manager's dual role on inventory policy

In modern corporations, the Operations Manager’s role in defining of firm’s strategy is becoming more important. In this paper we describe how firms can use this tendency for Operations Managers to make strategic decisions as a mechanism to prevent inventory mismanagement. These managers have incentives to speculate with inventory cost reductions, thereby avoiding sharp reductions in a single period, because it would hinder further reductions in the future. Remarkably, firms may prevent such behavior by stimulating the Operations Managers’ strategic orientation, without losing sight of inventory-efficient management

Current US algae biorefineries, projects and perspectives

Large challenges remain to take advantage of algae (cyanobacteria, microalgae, and macroalgae) as a bioenergy, biofuels, and bioproducts crop. Traditional applications in the nutraceutical and food industry, have shown more promise. New efforts in combining a biorefinery approach with wastewater treatment, anaerobic digestion, and biomass utilization are becoming more popular and successful towards providing a middle ground for implementation of algae cultivation systems. An overview will be provided of the growth in fundamental and applied algae research in recent years, which will include a review of the scientific literature and key programs in bioenergy in the US leading to a resurgence and interest in algae. With this presentation, a discussion will ensue on the challenges being tackled to make the algae biorefinery a viable industry, including progress and opportunities available to develop algae as a key crop for the bioenergy and the bioproducts industries.Universidad de Málaga.Campus de Excelencia Internacional Andalucia Tec

Loop quantization from a lattice gauge theory perspective

We present an interpretation of loop quantization in the framework of lattice gauge theory. Within this context the lack of appropriate notions of effective theories and renormalization group flow exhibit loop quantization as an incomplete framework. This interpretation includes a construction of embedded spin foam models which does not rely on the choice of any auxiliary structure (e.g. triangulation) and has the following straightforward consequences: (1) The values of the coupling constants need to be those of an UV-attractive fixed point (2) The kinematics of canonical loop quantization and embedded spin foam models are compatible (3) The weights assigned to embedded spin foams are independent of the 2-polyhedron used to regularize the path integral, $|J|_x = |J|_{x'}$ (4) An area spectrum with edge contributions proportional to $l_{\rm PL}^2 (j+1 / 2)$ is not compatible with embedded spin foam models and/or canonical loop quantizationComment: 11 pages, no figures; completely rewritte