Weakly compact composition operators on spaces of Lipschitz functions

Let $X$ be a pointed compact metric space. Assuming that $\mathrm{lip}_0(X)$ has the uniform separation property, we prove that every weakly compact composition operator on spaces of Lipschitz functions $\mathrm{Lip}_0(X)$ and $\mathrm{lip}_0(X)$ is compact.Comment: 6 page

Multi-domain ferroelectricity as a limiting factor for voltage amplification in ferroelectric field-effect transistors

We revise the possibility of having an amplified surface potential in ferroelectric field-effect transistors pointed out by [S. Salahuddin and S. Datta, Nano Lett. 8, 405 (2008)]. We show that the negative-capacitance regime that allows for such an amplification is actually bounded by the appearance of multi-domain ferroelectricity. This imposes a severe limit to the maximum step-up of the surface potential obtainable in the device. We indicate new device design rules taking into account this scenario.Comment: 4 pages, 3 figure

The acoustic cut-off frequency of the Sun and the solar magnetic activity cycle

The acoustic cut-off frequency -the highest frequency for acoustic solar eigenmodes- is an important parameter of the solar atmosphere as it determines the upper boundary of the p-mode resonant cavities. At frequencies beyond this value, acoustic disturbances are no longer trapped but traveling waves. Interference amongst them give rise to higher-frequency peaks -the pseudomodes- in the solar acoustic spectrum. The pseudomodes are shifted slightly in frequency with respect to p modes making possible the use of pseudomodes to determine the acoustic cut-off frequency. Using data from GOLF and VIRGO instruments on board the SOHO spacecraft, we calculate the acoustic cut-off frequency using the coherence function between both the velocity and intensity sets of data. By using data gathered by these instruments during the entire lifetime of the mission (1996 till the present), a variation in the acoustic cut-off frequency with the solar magnetic activity cycle is found.Comment: Paper accepted in ApJ. 26 Pages, 9 figure

A BARGAINING APPROACH TO COORDINATION IN NETWORKS

This paper presents a model in which players interact via the formation of costly links and the benefits of bilateral interactions are determined by a coordination game. A novel contribution of this paper is that the fraction of the cost borne by each player involved in a bilateral link is not fixed exogenously, but results from bargaining. We analyze the model both in a static and a dynamic setting. Whereas the static game has multiplicity of equilibria, we show that only one is stochastically stable.Coordination; Nash bargaining solution; Risk-dominance; Stochastic stability

Strangeness on the nucleon

Observables from parity violation in elastic electron-nucleon scattering and neutral current quasi-elastic neutrino-nucleus scattering are employed as tools to improve the current knowledge on the strangeness content in the nucleon.Comment: Proceedings of International Scientific Meeting on Nuclear Physics, 9-13th September 2012. La R\'abida, Huelva, Spai

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

NETWORK FORMATION AND COORDINATION: BARGAINING THE DIVISION OF LINK COSTS

This paper presents a model of network formation with costly links. We endogenize the amount of cost born by each player involved in a bilateral link by considering that these shares result from bargaining. We analyze this feature in a context of coordination games. We show that, if the cost of the link is not too high, the complete network arises and players coordinate on the same action. If this cost is higher than the risk-dominance premium the efficient action is selected; instead, if it is lower, the risk-dominant action prevails.Coordination, Nash bargaining solution, Markov process