Anomalous exchange interaction between intrinsic spins in conducting graphene systems

We address the nature and possible observable consequences of singular one-electron states that appear when strong defects are introduced in the metallic family of graphene, namely, metallic carbon nanotubes and nanotori. In its simplest form, after creating two defects on the same sublattice, a state may emerge at the Fermi energy presenting very unusual properties: It is unique, normalizable, and features a wave function equally distributed around both defects. As a result, the exchange coupling between the magnetic moments generated by the two defects is anomalous. The intrinsic spins couple ferromagnetically, as expected, but do not present an antiferromagnetic excited state at any distance. We propose the use of metallic carbon nanotubes as a novel electronic device based on this anomalous coupling between spins which can be useful for the robust transmission of magnetic information at large distances.Comment: 5 pages 5 fugure

Optical implementability of the two-dimensional Quantum Walk

We propose an optical cavity implementation of the two-dimensional coined quantum walk on the line. The implementation makes use of only classical resources, and is tunable in the sense that a large number of different unitary transformations can be implemented by tuning some parameters of the device.Comment: 9 pages, 3 figure

Hydrogenated Graphene Nanoribbons for Spintronics

We show how hydrogenation of graphene nanoribbons at small concentrations can open new venues towards carbon-based spintronics applications regardless of any especific edge termination or passivation of the nanoribbons. Density functional theory calculations show that an adsorbed H atom induces a spin density on the surrounding $\pi$ orbitals whose symmetry and degree of localization depends on the distance to the edges of the nanoribbon. As expected for graphene-based systems, these induced magnetic moments interact ferromagnetically or antiferromagnetically depending on the relative adsorption graphene sublattice, but the magnitude of the interactions are found to strongly vary with the position of the H atoms relative to the edges. We also calculate, with the help of the Hubbard model, the transport properties of hydrogenated armchair semiconducting graphene nanoribbons in the diluted regime and show how the exchange coupling between H atoms can be exploited in the design of novel magnetoresistive devices

The approximate f-core and the utopia payoff for infinite assignment games

Assignment problems where both sets of agents are countably infinite, the so-called infinite assignment problems, are studied as well as the related assignment games. Further, two solutions for these games are studied. The first one is the approximate f-core for games with a finite value. This particular solution takes into account that due to organisational limitations only finite groups of agents can protest against proposals of profit distributions. Second, we study the utopia payoff, the perfect proposal in which each agent receives the maximal amount he can get. \u

Viscoelastic vibration damping identification methods. Application to laminated glass.

Laminatedglass is composed of two glass layers and a thin intermediate PVB layer, strongly influencing PVB's viscoelastic behaviour its dynamic response. While natural frequencies are relatively easily identified even with simplified FE models, damping ratios are not identified with such an ease. In order to determine to what extent external factors influence dampingidentification, different tests have been carried out. The external factors considered, apart from temperature, are accelerometers, connection cables and the effect of the glass layers. To analyse the influence of the accelerometers and their connection cables a laser measuring device was employed considering three possibilities: sample without instrumentation, sample with the accelerometers fixed and sample completely instrumented. When the sample is completely instrumented, accelerometer readings are also analysed. To take into consideration the effect of the glass layers, tests were realised both for laminatedglass and monolithic samples. This paper presents in depth data analysis of the different configurations and establishes criteria for data acquisition when testing laminatedglass

Van der Waals spin valves

We propose spin valves where a 2D non-magnetic conductor is intercalated between two ferromagnetic insulating layers. In this setup, the relative orientation of the magnetizations of the insulating layers can have a strong impact on the in-plane conductivity of the 2D conductor. We first show this for a graphene bilayer, described with a tight-binding model, placed between two ferromagnetic insulators. In the anti-parallel configuration, a band gap opens at the Dirac point, whereas in the parallel configuration, the graphene bilayer remains conducting. We then compute the electronic structure of graphene bilayer placed between two monolayers of the ferromagnetic insulator CrI$_3$, using density functional theory. Consistent with the model, we find that a gap opens at the Dirac point only in the antiparallel configuration.Comment: 5 pages, 4 figure

Convex Games with Countable Number of Players and Sequencing Situations

AMS classification: 91A12;Cooperative games;countable number of players;convexity;infinite sequencing situations

The Owen Set and the Core of Semi-Infinite Linear Production Situations

AMS classifications: 90D12, 90C05, 90C34.cooperative games;linear production;core;duality gap