Lagrangians for Massive Dirac Chiral Superfields

A variant for the superspin one-half massive superparticle in $4D$, $\mathcal{N}=1$, based on Dirac superfields, is offered. As opposed to the current known models that use spinor chiral superfields, the propagating fields of the supermultiplet are those of the lowest mass dimensions possible: scalar, Dirac and vector fields. Besides the supersymmetric chiral condition, the Dirac superfields are not further constrained, allowing a very straightforward implementation of the path-integral method. The corresponding superpropagators are presented. In addition, an interaction super Yukawa potential, formed by Dirac and scalar chiral superfields, is given in terms of their component fields. The model is first presented for the case of two superspin one-half superparticles related by the charged conjugation operator, but in order to treat the case of neutral superparticles, the Majorana condition on the Dirac superfields is also studied. We compare our proposal with the known models of spinor superfields for the one-half superparticle and show that it is equivalent to them.Comment: 22 pages. Matches published versio

Improved dynamical particle swarm optimization method for structural dynamics

A methodology to the multiobjective structural design of buildings based on an improved particle swarm optimization algorithm is presented, which has proved to be very efficient and robust in nonlinear problems and when the optimization objectives are in conflict. In particular, the behaviour of the particle swarm optimization (PSO) classical algorithm is improved by dynamically adding autoadaptive mechanisms that enhance the exploration/exploitation trade-off and diversity of the proposed algorithm, avoiding getting trapped in local minima. A novel integrated optimization system was developed, called DI-PSO, to solve this problem which is able to control and even improve the structural behaviour under seismic excitations. In order to demonstrate the effectiveness of the proposed approach, the methodology is tested against some benchmark problems. Then a 3-story-building model is optimized under different objective cases, concluding that the improved multiobjective optimization methodology using DI-PSO is more efficient as compared with those designs obtained using single optimization.Peer ReviewedPostprint (published version

Graphical representation and generalization in sequences problems

In this paper we present different ways used by Secondary students to generalize when they try to solve problems involving sequences. 359 Spanish students solved generalization problems in a written test. These problems were posed through particular terms expressed in different representations. We present examples that illustrate different ways of achieving various types of generalization and how students express generalization. We identify graphical representation of generalization as a useful tool of getting other ways of expressing generalization, and we analyze its connection with other ways of expressing it

DISAGGREGATED ANALYSIS OF SHORT-RUN BEEF SUPPLY RESPONSE

Conceptual problems in model specification of beef supply response studies are investigated and a simultaneous equation model is formulated to estimate annual U.S. carcass supply, demand, and inventories of beef. Three basic issues are addressed: (a) disaggregation, (b) simultaneity, and (c) differentiation between current and expected price effects. Empirical results indicate positive supply response of each quality type of steers and heifers, and negative supply response of cows to current own-price changes. The derived aggregate supply elasticity is positive. The effects of grain price changes on beef price, supply and composition are also evaluated.Demand and Price Analysis, Livestock Production/Industries,

Universal out-of-equilibrium Transport in Kondo-correlated quantum dots: Renormalized dual Fermions on the Keldysh contour

The nonlinear conductance of semiconductor heterostructures and single molecule devices exhibiting Kondo physics has recently attracted attention. We address the observed sample dependence of the measured steady state transport coefficients by considering additional electronic contributions in the effective low-energy model underlying these experiments that are absent in particle-hole symmetric setups. A novel version of the superperturbation theory of Hafermann et al. in terms of dual fermions is developed, which correctly captures the low-temperature behavior. We compare our results with the measured transport coefficients.Comment: 5 pages, 2 figure

Para-Grassmann Variables and Coherent States

The definitions of para-Grassmann variables and q-oscillator algebras are recalled. Some new properties are given. We then introduce appropriate coherent states as well as their dual states. This allows us to obtain a formula for the trace of a operator expressed as a function of the creation and annihilation operators.Comment: This is a contribution to the Proc. of the O'Raifeartaigh Symposium on Non-Perturbative and Symmetry Methods in Field Theory (June 2006, Budapest, Hungary), published in SIGMA (Symmetry, Integrability and Geometry: Methods and Applications) at http://www.emis.de/journals/SIGMA

Renormalized masses of heavy Kaluza-Klein states

Several ways of computing the radiative corrections to the heavy boson masses in Kaluza-Klein theory are discussed. It is argued that only an intrinsically higher dimensional approach embodies all the desired physical properties.Comment: LaTeX, 22 pages. Fully rewritten and streamlined. Five and six dimensional cases treated separatelly. References adde

Effective and neutral stresses in soils using boundary element methods

The evaluation of neutral pressures in soil mechanics problems is a fundamental step to evaluate deformations in soils. In this paper, we present some results obtained by using the boundary element method for plane problems, describing the undrained situation as well as the consolidation problem