Single hole and vortex excitations in the doped Rokhsar-Kivelson quantum dimer model on the triangular lattice

We consider the doped Rokhsar-Kivelson quantum dimer model on the triangular lattice with one mobile hole (monomer) at the Rokhsar-Kivelson point. The motion of the hole is described by two branches of excitations: the hole may either move with or without a trapped Z2 vortex (vison). We perform a study of the hole dispersion in the limit where the hole hopping amplitude is much smaller than the interdimer interaction. In this limit, the hole without vison moves freely and has a tight-binding spectrum. On the other hand, the hole with a trapped vison is strongly constrained due to interference effects and can only move via higher-order virtual processes.Comment: 4 pages, 4 figures; minor changes, replaced by published versio

Nuclear State Preparation via Landau-Zener-Stueckelberg transitions in Double Quantum Dots

We theoretically model a nuclear-state preparation scheme that increases the coherence time of a two-spin qubit in a double quantum dot. The two-electron system is tuned repeatedly across a singlet-triplet level-anticrossing with alternating slow and rapid sweeps of an external bias voltage. Using a Landau-Zener-Stueckelberg model, we find that in addition to a small nuclear polarization that weakly affects the electron spin coherence, the slow sweeps are only partially adiabatic and lead to a weak nuclear spin measurement and a nuclear-state narrowing which prolongs the electron spin coherence. This resolves some open problems brought up by a recent experiment [D. J. Reilly et al., Science 321, 817 (2008).]. Based on our description of the weak measurement, we simulate a system with up to n=200 nuclear spins per dot. Scaling in n indicates a stronger effect for larger n.Comment: 4.1 pages, 2 figure

The Two-Component Virial Theorem and the Physical Properties of Stellar Systems

Motivated by present indirect evidences that galaxies are surrounded by dark matter halos, we investigate whether their physical properties can be described by a formulation of the virial theorem which explicitly takes into account the gravitational potential term representing the interaction of the dark halo with the barionic or luminous component. Our analysis shows that the application of such a ``two-component virial theorem'' not only accounts for the scaling relations displayed, in particular, by elliptical galaxies, but also for the observed properties of all virialized stellar systems, ranging from globular clusters to galaxy clusters.Comment: 13 pages, 2 figures, LaTeX, corrected few typos. This version matches the published versio

Coherent Adiabatic Spin Control in the Presence of Charge Noise Using Tailored Pulses

We study finite-time Landau-Zener transitions at a singlet-triplet level crossing in a GaAs double quantum dot, both experimentally and theoretically. Sweeps across the anticrossing in the high driving speed limit result in oscillations with a small visibility. Here we demonstrate how to increase the oscillation visibility while keeping sweep times shorter than T2* using a tailored pulse with a detuning dependent level velocity. Our results show an improvement of a factor ~2.9 for the oscillation visibility. In particular, we were able to obtain a visibility of ~0.5 for St\"uckelberg oscillations, which demonstrates the creation of an equally weighted superposition of the qubit states.Comment: Related papers at http://pettagroup.princeton.ed

Abandono en servicios - Una revisión bibliométrica

[EN] The purpose of this article is to identify the most impactful research on customer churn and to map the conceptual and intellectual structure of its field of study. Data were collected from the WoS database, comprising 338 articles published between 1995 and 2020. Several bibliometric techniques were applied, including analysis of co-words, co-citation, bibliographic coupling, and co-authorship networks. R software and the Bibliometrix/Biblioshiny package were used to perform the analyses. The results identify the most active and influential authors, articles, and journals on the topic. More specifically, through co-citations and bibliographic coupling, it was possible to map the oldest articles (retrospective analysis) and the current research front (prospective analysis). The retrospective analysis, based on co-citations, revealed that the foundations of this research field are constructs such as quality of service, satisfaction, loyalty, and changing behaviors. The prospective analysis, performed through bibliographic coupling, revealed that current research is embedded in predictive analysis, clusters, data mining, and algorithms. The results provide robust guidance for further investigation in this field.[ES] El objetivo de este artículo es identificar las investigaciones más impactantes sobre la pérdida de clientes y trazar la estructura conceptual e intelectual de su campo de estudio. Los datos han sido recogidos de la base de datos WoS, que comprenden 338 artículos publicados entre 1995 y 2020. Varias técnicas bibliométricas fueron aplicadas, incluyendo el análisis de co-palabras, cocitaciones, acoplamiento bibliográfico y redes de coautoría. Para realizar los análisis se utilizaron el software R y el Bibliometrix/Biblioshiny. Los resultados identifican los autores, artículos y revistas más influyentes y activos sobre el tema. Más específicamente, a través de las cocitaciones y el acoplamiento bibliográfico, fue posible mapear los artículos más antiguos (análisis retrospectivo) y la investigación más actual (análisis prospectivo). El análisis retrospectivo, basado en las cocitaciones, reveló que los fundamentos de este campo de investigación son constructos como la calidad del servicio, la satisfacción, la lealtad y el cambio de comportamientos. El análisis prospectivo, realizado a través del acoplamiento bibliográfico, reveló que la investigación actual está inmersa en el análisis predictivo, los conglomerados, la minería de datos y los algoritmos. Los resultados proporcionan una sólida orientación para seguir investigando en este campo

Avaliação do desempenho de misturas betuminosas temperadas

A diminuição do consumo de combustíveis e das emissões de gases com efeitos de estufa são um grande desafio da sociedade actual. No fabrico de misturas betuminosas desenvolveram-se recentemente diversas tecnologias para redução da temperatura de produção e aplicação em obra que promoveram a produção de misturas betuminosas temperadas (MBT). Inúmeros benefícios no uso das MBT têm potenciado o seu crescente desenvolvimento, destacando-se a redução das emissões no fabrico e a diminuição do combustível gasto nos queimadores. Na colocação em obra, as MBT garantem uma trabalhabilidade adequada à sua aplicação e compactação a menores temperaturas, reduzindo a produção de fumos, possibilitando o transporte a longas distâncias, alargando a época de pavimentação, e permitindo a sua aplicação a temperaturas atmosféricas inferiores. Neste trabalho compara-se o desempenho mecânico de uma mistura betuminosa (AC 14 Surf 50/70) produzida a temperaturas convencionais e a menores temperaturas (125 a 135 ºC), através da introdução de dois aditivos (Sasobit® e Cecabase®). Foram determinadas as propriedades dos ligantes base e modificados (penetração, anel e bola, viscosidade e reologia) para observação do comportamento, determinação das temperaturas de fabrico e aferição da percentagem de aditivo. A caracterização das misturas foi realizada inicialmente em laboratório (propriedades volumétricas, sensibilidade à água e resistência à deformação permanente), realizando-se em seguida um trecho experimental onde foram extraídos provetes para determinação das características anteriormente referidas, além do módulo de rigidez. Em comparação com a mistura convencional, conseguiu-se reduzir a temperatura das MBT cerca de 15 a 25 ºC mantendo idênticas propriedades volumétricas e mecânicas em laboratório, o que não se conseguiu no trecho devido a um problema de contaminação com o combustível usado no queimador

Four new species of Paspalum (Poaceae, Paniceae) from Central Brazil, and resurrection of an old one

Four new Brazilian species from the genus Paspalum are described and illustrated: P. phaeotrichum, P. vexillarium, P. veredense, and P. clipeum. Paspalum phaeotrichum is an annual with no obvious affinity to any known species of Paspalum, although it shares several characters with species of both P. subg. Ceresia and the 'Bertoniana' group. Paspalum vexillarium is presumably related to P. ceresia, with which it has been confused. Paspalum veredense shows affinities with both P. ellipticum and P. erianthoides. Paspalum clipeum is probably related to annual species of the 'Plicatula' group, although it lacks the dark brown upper florets typical of that group. Moreover, P. spissum, a species currently considered as a synonym under P. carinatum, is recognized on the basis of vegetative morphology, phenology and habitat. Keys to the treated species are provided when relevant, as well as a distribution map.Quatro novas espécies de Paspalum do Brasil são descritas e ilustradas: P. phaeotrichum, P. vexillarium, P. veredense , e P. clipeum . Paspalum phaeotrichum é uma espécie anual sem afinidades obvias com outras espécies do gênero, embora compartilhe vários caracteres com P. subg. Ceresia e com o grupo 'Bertoniana'. Paspalum vexillarium é supostamente relacionada a P. ceresia, com a qual tem sido confundida. Paspalum veredense tem afinidades com P. ellipticum e P. erianthoides. Paspalum clipeum é provavelmente relacionada às espécies anuais do grupo 'Plicatula', embora não apresente os antécios superiores de cor marrom escura, típicos desse grupo. Além disso, P. spissum, uma espécie atualmente considerada como sinônimo de P. carinatum, é reabilitada com base na morfologia vegetativa, fenologia e habitat. São fornecidas chaves para as espécies tratadas, quando relevante, assim como um mapa de distribuição.Fil: Rua, Gabriel Hugo. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio da Agricultura Pecuaria e Abastecimento de Brasil. Empresa Brasileira de Pesquisa Agropecuaria; BrasilFil: Valls, José Francisco M.. Ministerio da Agricultura Pecuaria e Abastecimento de Brasil. Empresa Brasileira de Pesquisa Agropecuaria; BrasilFil: Graciano Ribeiro, Dalva. Universidade do Brasília; BrasilFil: Oliveira, Regina C.. Universidade Federal Rural do Semi-Árido; Brasi

"Fundamental-Plane"-Like Relations From Collisionless Stellar Dynamics: A Comparison of Mergers and Collapses

We present a new set of dissipationless N-body simulations aiming to better understand the pure dynamical aspects of the ``Fundamental Plane'' (FP) of elliptical galaxies. We have extended our previous hierarchical merger scheme by considering the Hernquist profile for the initial galaxy model. Two-component Hernquist galaxy models were also used to study the effect of massive dark halos on the end-products characteristics. We have also performed new collapse simulations including initial spin. We found that the one-component Hernquist mergers give results similar to those found for the one-component King models, namely both were able to build-up small scatter FP-like correlations with slopes consistent with what is found for the near-infrared FP of nearby galaxies. The two-component models also reproduce a FP-like correlation, but with a significantly steeper slope. This is in agreement with what has been found for elliptical galaxies at higher redshift (0.1 $<$ z $<$ 0.6). We discuss some structural properties of the simulated galaxies and their ability to build-up FP-like correlations. We confirm that collapses generally do not follow a FP-like correlation regardless of the initial spin. We suggest that the evolution of gradients in the gravitational field of the merging galaxies may be the main ingredient dictating the final non-homology property of the end products.Comment: 15 pages, 11 figures, uses mn2e.cls. Accepted for publication in MNRA