Ambigüedad estratégica en contratos públicos de suministro

En este trabajo se presenta, sobre la base de un modelo de intercambio entre agentes privados de Douglas Bernheim y Michael Whinston (1998), un contrato típico de suministro entre el gobierno y una firma privada, en un contexto dinámico y sin renegociación. La firma debe realizar inversiones (observables, no verificables) para mejorar la calidad o para reducir costos o ambos tipos. Los resultados obtenidos por Bernheim, D. y M. Whinston se aplican cuando el comprador es el gobierno benevolente, siempre que valore por igual las utilidades de los agentes privados y la recaudación de impuestos para pagar el bien no distorsione la asignación de recursos en otros mercados. Cuando la firma debe realizar inversiones para reducir costos, el contrato incompleto que sólo especifica todas las variables verificables es óptimo; y cuando la firma debe realizar inversiones para mejorar la calidad, es óptimo un contrato incompleto por ambigüedad estratégica (no incluye todas las variables verificables). Sin embargo, cuando se incorpora el supuesto de que la inversión en reducción de costos disminuye la calidad del bien, el contrato incompleto tradicional no es óptimo y se alcanza el first best con uno incompleto por ambigüedad estratégica. Lo mismo sucede cuando se combinan ambos modelos y la firma debe realizar ambos tipos de inversión, afecte o no la inversión en reducción de costos el nivel de calidad.

Observation of Stable Jones-Roberts Solitons in Bose-Einstein Condensates

We experimentally generate two-dimensional Jones-Roberts solitons in a three-dimensional atomic Bose-Einstein condensate by imprinting a triangular phase pattern. By monitoring their dynamics we observe that this kind of solitary waves are resistant to both dynamic (snaking) and thermodynamic instabilities, that usually are known to strongly limit the lifetime of dark plane solitons in dimensions higher than one. We additionally find signatures of a possible dipole-like interaction between them. Our results confirm that Jones-Roberts solitons are stable solutions of the non-linear Schr\"odinger equation in higher dimensions and promote these excitations for applications beyond matter wave physics, like energy and information transport in noisy and inhomogeneous environments

An idea for the future proton detection of (p,2p) reactions with the (RB)-B-3 set-up at FAIR

5 págs.; 6 figs.; 1 tab.; FAIRNESS 2014; Open Access funded by Creative Commons Atribution Licence 3.0The R3B Collaboration has a long experience in probing exotic nuclei via quasi-free scattering reactions. To continue these studies a new array capable of detecting protons and gamma rays of high energy is currently being developed, the CALIFA (R3B CALorimeter for In Flight γ arrays and high energy charged pArticles). This contribution reports on the current solution for the forward Endcap of the CALIFA detector and on the latest test results.This work was partly financed by the Spanish Research Funding Agency CICYT under Project FPA2012-32443. Further Guillermo Ribeiro acknowledges his FPI-MICINN grant.Peer Reviewe

Optimizing photon indistinguishability in the emission from incoherently-excited semiconductor quantum dots

Most optical quantum devices require deterministic single-photon emitters. Schemes so far demonstrated in the solid state imply an energy relaxation which tends to spoil the coherent nature of the time evolution, and with it the photon indistinguishability. We focus our theoretical investigation on semiconductor quantum dots embedded in microcavities. Simple and general relations are identified between the photon indistinguishability and the collection efficiency. The identification of the key parameters and of their interplay provides clear indications for the device optimization

Forming first-ranked early-type galaxies through hierarchical dissipationless merging

We have developed a computationally competitive N-body model of a previrialized aggregation of galaxies in a flat LambdaCDM universe to assess the role of the multiple mergers that take place during the formation stage of such systems in the configuration of the remnants assembled at their centres. An analysis of a suite of 48 simulations of low-mass forming groups (of about 1E13 solar masses) demonstrates that the gravitational dynamics involved in their hierarchical collapse is capable of creating realistic first-ranked galaxies without the aid of dissipative processes. Our simulations indicate that the brightest group galaxies (BGGs) constitute a distinct population from other group members, sketching a scenario in which the assembly path of these objects is dictated largely by the formation of their host system. We detect significant differences in the distribution of Sersic indices and total magnitudes, as well as a luminosity gap between BGGs and the next brightest galaxy that is positively correlated with the total luminosity of the parent group. Such gaps arise from both the grow of BGGs at the expense of lesser companions and the decrease in the relevance of second-ranked objects in equal measure. This results in a dearth of intermediate-mass galaxies which explains the characteristic central dip detected in their luminosity functions in dynamically young galaxy aggregations. The fact that the basic global properties of our BGGs define a thin mass fundamental plane strikingly similar to that followed giant early-type galaxies in the local universe reinforces confidence in the results obtained.Comment: 25 pages, 14 figures, 3 tables. Accepted to MNRA