String theory triplets and higher-spin curvatures

Unconstrained local Lagrangians for higher-spin gauge theories are bound to involve auxiliary fields, whose integration in the partition function generates geometric, effective actions expressed in terms of curvatures. When applied to the triplets, emerging from the tensionless limit of open string field theory, the same procedure yields interesting alternative forms of geometric Lagrangians, expressible for both bosons and fermions as squares of field-strengths. This shows that higher-spin curvatures might play a role in the dynamics, regardless of whether the Fronsdal-Labastida constraints are assumed or forgone.Comment: 14 pages. Eqs. (2.13) and (3.7) added. Footnotes 8 and 14 and corresponding references included. Additional minor changes. To appear in Phys. Lett.

Confined two-dimensional fermions at finite density

We introduce the chemical potential in a system of two-dimensional massless fermions, confined to a finite region, by imposing twisted boundary conditions in the Euclidean time direction. We explore in this simple model the application of functional techniques which could be used in more complicated situations.Comment: 15 pages, LaTe

Quartet unconstrained formulation for massless higher spin fields

We construct simple unconstrained Lagrangian formulations for massless higher spin fields in flat space of arbitrary dimension and on anti de Sitter background. Starting from the triplet equations of Francia and Sagnotti, which describe a chain of spin modes, we introduce an auxiliary field and find appropriate gauge invariant constraints that single out the spin-s mode. The resulting quartet of fields, thus describing an irreducible representation of the Poincare group, is used to construct simple Lagrangian formulations, which are local, free from higher derivative terms and use equal number of auxiliary fields for an unconstrained description of any value of spin. Our method proves to be most efficient for an unconstrained description of massless higher spin fermions in anti de Sitter space. A relation of the minimal models with the universal BRST approach is discussed.Comment: V4: 27 pages; references and acknowledgement adde

Transverse Invariant Higher Spin Fields

It is shown that a symmetric massless bosonic higher-spin field can be described by a traceless tensor field with reduced (transverse) gauge invariance. The Hamiltonian analysis of the transverse gauge invariant higher-spin models is used to control a number of degrees of freedom.Comment: 12 pages, no figures. The general proof and the example of a spin-3 adde

Estimation of the methane emission factor for the Italian Mediterranean buffalo

In order to contribute to the improvement of the national greenhouse gas emission inventory, this work aimed at estimating a country-specific enteric methane (CH4) emission factor for the Italian Mediterranean buffalo. For this purpose, national agriculture statistics, and information on animal production and farming conditions were analysed, and the emission factor was estimated using the Tier 2 model of the Intergovernmental Panel on Climate Change. Country-specific CH4 emission factors for buffalo cows (630 kg body weight, BW) and other buffalo (313 kg BW) categories were estimated for the period 1990–2004. In 2004, the estimated enteric CH4 emission factor for the buffalo cows was 73 kg/head per year, whereas that for other buffalo categories it was 56 kg/head per year. Research in order to determine specific CH4 conversion rates at the predominant production system is suggested

On geometric equations and duality for free higher spins

We provide a general scheme for dualizing higher-spin gauge fields in arbitrary irreducible representations of GL(D,R). We also give a recipe for constructing Fronsdal-like field equations and Lagrangians for such exotic fields.Comment: 12 pages, no figur

Massless fermions in a bag at finite density and temperature

We introduce the chemical potential in a system of massless fermions in a bag by impossing boundary conditions in the Euclidean time direction. We express the fermionic mean number in terms of a functional trace involving the Green's function of the boundary value problem, which we study analytically. Numerical evaluations are made, and an application to a simple hadron model is discussed.Comment: 14 pages, 3 figures, RevTe

La comunicación didáctica entre profesores de matemáticas: un elemento para el cambio

Este artículo presenta una serie de reflexiones acerca de cómo la alfabetización matemática puede llegar a ser una de las herramientas necesarias para que los ciudadanos de sociedades con un alto desarrollo tecnológico adquieran una competencia democrática que les permita participar en los procesos de sus sociedades. El argumento central gira en torno a la idea de que a través de la educación matemática se puede construir y fomentar un conocimiento reflexivo que, junto con el conocimiento tecnológico, consoliden la capacidad de los individuos para actuar en la sociedad. A pesar de que todo el artículo discute el caso de sociedades desarrolladas, el artículo ilumina el significado que tiene una educación para la democracia, proyecto que hoy en día se trata de construir en países como Colombia