Topological Descendants: DDK and KM Realizations

The "minimal matter + scalar" system can be embedded into the twisted N=2 topological algebra in two ways: a la DDK or a la KM. Here we present some results concerning the topological descendants and their DDK and KM realizations. In particular, we prove four "no-ghost" theorems (two for null states) regarding the reduction of the topological descendants into secon- daries of the "minimal matter + scalar" conformal field theory. We write down the relevant expressions for the case of level 2 descendants.Comment: 10 pgs, Late

Spectral Flows and Twisted Topological Theories

We analyze the action of the spectral flows on N=2 twisted topological theories. We show that they provide a useful mapping between the two twisted topological theories associated to a given N=2 superconformal theory. This mapping can also be viewed as a topological algebra automorphism. In particular null vectors are mapped into null vectors, considerably simplifying their computation. We give the level 2 results. Finally we discuss the spectral flow mapping in the case of the DDK and KM realizations of the topological algebra.Comment: The presentation of the results has been very much improved. Some references have been adde

A virtual element method for the vibration problem of Kirchhoff plates

The aim of this paper is to develop a virtual element method (VEM) for the vibration problem of thin plates on polygonal meshes. We consider a variational formulation relying only on the transverse displacement of the plate and propose an $H^2(\Omega)$ conforming discretization by means of the VEM which is simple in terms of degrees of freedom and coding aspects. Under standard assumptions on the computational domain, we establish that the resulting schemeprovides a correct approximation of the spectrum and prove optimal order error estimates for the eigenfunctions and a double order for the eigenvalues. The analysis restricts to simply connected polygonal clamped plates, not necessarily convex. Finally, we report several numerical experiments illustrating the behaviour of the proposed scheme and confirming our theoretical results on different families of meshes. Additional examples of cases not covered by our theory are also presented

Pobreza urbana y terciarización en la megalópolis de México

Tesis de maestría de Álvarez Rivera DavidAnálisis estadístico y espacial de la relación entre el proceso de terciarización y la pobreza urbana en la megalópolis del centro de México, que es una de las aglomeraciones urbanas más grandes del mundo

Noether-Wald energy in Critical Gravity

Criticality represents a specific point in the parameter space of a higher-derivative gravity theory, where the linearized field equations become degenerate. In 4D Critical Gravity, the Lagrangian contains a Weyl-squared term, which does not modify the asymptotic form of the curvature. The Weyl$^{2}$ coupling is chosen such that it eliminates the massive scalar mode and it renders the massive spin-2 mode massless. In doing so, the theory turns consistent around the critical point. Here, we employ the Noether-Wald method to derive the conserved quantities for the action of Critical Gravity. It is manifest from this energy definition that, at the critical point, the mass is identically zero for Einstein spacetimes, what is a defining property of the theory. As the entropy is obtained from the Noether-Wald charges at the horizon, it is evident that it also vanishes for any Einstein black hole.Comment: 7 pages, no figures, Final version for PL

First report of Diaphorina citri (Hemiptera: Psyllidae) in Costa Rica

In November 2003, the Asian citrus psyllid (Diaphorina citri) was found for the first time in Costa Rica, in Alajuela, Heredia and San Jose provinces. Figure 1 shows an adult female and nymphal instars of Asiatic citrus psyllid

Bridging the Disconnect

New York City is facing a youth unemployment crisis, but the city's youth workforce development programs reach only a fraction of those in need of help and are too often misaligned to the developmental needs of young New Yorkers

The Architecture of Non-places and Today’s Odyssey

Los llamados No-lugares se han ido convirtiendo en una de las señas distintivas de nuestra época; el cine reciente ha explorado con gran penetración sus contenidos espaciales y arquitectónicos.ENG: The so-called Non-places are becoming one of the distinctive features of our time; the recent cinema has explored with great insight their spacial and architectural contents.Peer Reviewe