490 research outputs found
Quasinormal modes and thermodynamical aspects of the 3D Lifshitz black hole
We consider scalar and spinorial perturbations on a background described by a
three-dimensional Lifshitz black hole. We obtained the corresponding
quasinormal modes which perfectly agree with the analytical result for the
quasinormal frequency in the scalar case. The numerical results for the
spinorial perturbations reinforce our conclusion on the stability of the model
under these perturbations. We also calculate the area spectrum, which prove to
be equally spaced, as an application of our results.Comment: 8 pages, 5 figures. Prepared for "Recent Developments in Gravity (NEB
XV)", Chania, Greece, 20-23 June 201
The role of Dark Matter interaction in galaxy clusters
We consider a toy model to analyze the consequences of dark matter
interaction with a dark energy background on the overall rotation of galaxy
clusters and the misalignment between their dark matter and baryon
distributions when compared to {\Lambda}CDM predictions. The interaction
parameters are found via a genetic algorithm search. The results obtained
suggest that interaction is a basic phenomenon whose effects are detectable
even in simple models of galactic dynamics.Comment: RevTeX 4.1, 5 pages, 3 figure
Instability of the Time Dependent Horava-Witten Model
We consider scalar perturbations in the time-dependent Ho\u{r}ava-Witten
Model in order to probe its stability. We show that during the non-singular
epoque the model evolves without instabilities until it encounters the
curvature singularity where a big crunch is supposed to occur. We compute the
frequencies of the scalar field oscillation during the stable period and show
how the oscillations can be used to prove the presence of such a singularity.Comment: 12 pages, 4 figures. References added. Some comments clarified.
Accepted in Phys. Rev.
Creative innovation in Spanish construction firms
"This material may be downloaded for personal use only. Any other use requires prior permission of the American Society of Civil Engineers"Small and medium-sized contractors are characterized by organizational structures that are highly focused on control. As a result, employees concentrate on day-to-day activities with little time or motivation to generate creative ideas. Generally, the technological improvements of these companies arise as a result of problem-solving at the construction site. Nevertheless, the actual status quo is changing. In fact, some Spanish public agencies are already considering innovation as an added value in public procurement; thus, large contractors are starting to systemize their innovative efforts. This means that small and medium-sized enterprises must modify their attitudes towards innovation in order to sustain their competitiveness. The implementation of a system that enhances innovation and acquisition of knowledge may be the solution to overcome this disadvantage. The authors analyzed the implementation of an innovation management system in a Spanish construction firm of medium size for nine years. The system builds on a set of processes aimed to generate innovation projects that allow the contractor to document the innovation, not only for internal purposes related to knowledge management, but also for external ones associated with obtaining better results in public tenders. These processes are: (a) technology watch; (b) creativity; (c) planning and executing innovation projects; (d) technology transfer; and (e) protection of results. The last step is the feedback of the entire process through the assessment of the final outcomes. The implementation of the innovation system is ensured within the organization, through training of personnel, participation of stakeholders and encouragement of the innovation culture.The research reported in this paper was partially funded by the Universidad Catolica del Maule (UCM) [Project Mejoramiento de la Calidad y Equidad de la Educacion Superior (MECESUP)-UCM0205], the Spanish Ministry of Infrastructure (Project 2004-36), and the Universitat Politecnica de Valencia (UPV) (Contract UPV-2008-0629). Francisco Vea, Ricardo Lacort, and Manuel Civera are thanked for their help and support throughout the implementation of the system. Dr. Debra Westall is thanked for revising the text.Yepes, V.; Pellicer Armiñana, E.; Fernando Alarcón, L.; Correa Becerra, CL. (2015). Creative innovation in Spanish construction firms. Journal of Professional Issues in Engineering Education and Practice. 141:04015006-1-04015006-10. https://doi.org/10.1061/(ASCE)EI.1943-5541.0000251S04015006-104015006-1014
Stability Analysis and Area Spectrum of 3-Dimensional Lifshitz Black Holes
In this work, we probe the stability of a three-dimensional Lifshitz
black hole by using scalar and spinorial perturbations. We found an analytical
expression for the quasinormal frequencies of the scalar probe field, which
perfectly agree with the behavior of the quasinormal modes obtained
numerically. The results for the numerical analysis of the spinorial
perturbations reinforce the conclusion of the scalar analysis, i.e., the model
is stable under scalar and spinor perturbations. As an application we found the
area spectrum of the Lifshitz black hole, which turns out to be equally spaced.Comment: 23 pages, 6 figures. References added. Version to appear in Phys.
Rev.
Taxonomic and nomenclatural rearrangements in Artemisia subgen. Tridentatae, including a redefinition of Sphaeromeria (Asteraceae, Anthemideae)
[EN]A recent molecular phylogenetic study of all members of Artemisia subgenus Tridentatae, as well as most of the other New World endemic Artemisia and the allied genera Sphaeromeria and Picrothamnus, raised the necessity of revising the taxonomic framework of the North American endemic Artemisia. Composition of the subgenus Tridentatae is enlarged to accommodate other North American endemics and is organized into 3 sections: Tridentatae, Nebulosae, and Filifoliae. This paper deals with the combination of one section, the amendment of 2 more sections, and the combination in or the reversion to Artemisia of some Sphaeromeria and Picrothamnus species. The new names given for previous Sphaeromeria species are Artemisia macarthurii (for S. argentea), A. albicans (for S. cana), A. constricta (for S. compacta), and A. inaequifolia (for S. diversifolia). The other Sphaeromeria we studied (S. capitata, S. potentilloides, S. ruthiae, and S. simplex) had been formerly considered Artemisia (respectively, A. capitata, A. potentilloides, A. ruthiae, and A. simplex), and their previous nomenclature is therefore recommended[ES]Un estudio reciente sobre la filogenia molecular de todos los miembros del subgénero Tridentatae de Artemisia, asà como de la mayorÃa de las otras especies de Artemisia endémicas del Nuevo Mundo y los géneros afines Sphaeromeria y Picrothamnus, hizo ver la necesidad de revisar el marco taxonómico de las especies de Artemisia endémicas a Norteamérica. La composición del subgénero Tridentatae se ha ampliado para dar cabida a las otras especies endémicas de Norteamérica, y está organizado en 3 secciones: Tridentatae, Nebulosae y Filifoliae. El presente artÃculo trata sobre la combinación de una sección y la enmienda de 2 más, y propone la incorporación o reversión a Artemisia de algunas especies de Sphaeromeria y Picrothamnus. Los nuevos nombres de las especies previamente asignadas a Sphaeromeria son Artemisia macarthurii (para S. argentea), A. albicans (para S. cana), A. constricta (para S. compacta) y A. inaequifolia (para S. diversifolia). Las otras especies de Sphaeromeria estudiadas (S. capitata, S. potentilloides, S.ruthiae y S. simplex) habÃan sido previamente consideradas como miembros de Artemisia (A. capitata, A. potentilloides, A. ruthiae y A. simplex, respectivamente), por lo quese recomienda utilizar su nomenclatura anteriorThis work was subsidized by projects CGL2007-64839-C02-01/BOS and CGL2007-64839-C02-02/BOS of the Spanish government. SG was granted a JAE-DOC contract from the CSIC and a short stay in the Shrub Sciences Laboratory (USDA) in Utah, also from the CSIC.Peer reviewe
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