Radiative zone solar magnetic fields and g-modes

We consider a generalized model of seismic-wave propagation that takes into account the effect of a central magnetic field in the Sun. We determine the g-mode spectrum in the perturbative magnetic field limit using a one-dimensional Magneto-Hydrodynamics (MHD) picture. We show that central magnetic fields of about 600-800 kG can displace the pure g-mode frequencies by about 1%, as hinted by the helioseismic interpretation of GOLF observations.Comment: 6 pages, 4 figures; final version to appear in MNRA

Effective cavity pumping from weakly coupled quantum dots

We derive the effective cavity pumping and decay rates for the master equation of a quantum dot-microcavity system in presence of $N$ weakly coupled dots. We show that the in-flow of photons is not linked to the out-flow by thermal equilibrium relationships.Comment: 6 pages, 1 figure, PLMCN10 conference proceeding

Probing the internal solar magnetic field through g-modes

The observation of g-mode candidates by the SoHO mission opens the possibility of probing the internal structure of the solar radiative zone (RZ) and the solar core more directly than possible via the use of the p-mode helioseismology data. We study the effect of rotation and RZ magnetic fields on g-mode frequencies. Using a self-consistent static MHD magnetic field model we show that a 1% g-mode frequency shift with respect to the Solar Seismic Model (SSeM) prediction, currently hinted in the GOLF data, can be obtained for magnetic fields as low as 300 kG, for current measured modes of radial order n=-20. On the other hand, we also argue that a similar shift for the case of the low order g-mode candidate (l=2, n=-3) frequencies can not result from rotation effects nor from central magnetic fields, unless these exceed 8 MG.Comment: 6 pages, 2 figures; final version to appear in MNRA

Relation Liftings on Preorders and Posets

The category Rel(Set) of sets and relations can be described as a category of spans and as the Kleisli category for the powerset monad. A set-functor can be lifted to a functor on Rel(Set) iff it preserves weak pullbacks. We show that these results extend to the enriched setting, if we replace sets by posets or preorders. Preservation of weak pullbacks becomes preservation of exact lax squares. As an application we present Moss's coalgebraic over posets

National evaluation of the neighbourhood nurseries: impact report

This study assessed the impact of NNI on parental employment, use of formal childcare, and take-up of benefits and tax credits, particularly for disadvantaged groups such as lone parents, low income families and ethnic minority groups

A non-resonant dark-side solution to the solar neutrino problem

We re-analyse spin-flavour precession solutions to the solar neutrino problem in the light of the recent SNO CC result as well as the 1258--day Super-Kamiokande data and the upper limit on solar anti-neutrinos. In a self-consistent magneto-hydrodynamics approach the resulting scheme has only 3 effective parameters: $\Delta m^2$, $\mu B_\perp$ and the neutrino mixing angle $\theta$. We show how a rates-only analysis for fixed $\mu B_\perp$ slightly favours spin-flavour precession (SFP) solutions over oscillations (OSC). In addition to the resonant solution (RSFP for short), there is a new non-resonant solution (NRSFP) in the ``dark-side''. Both RSFP and NRSFP lead to flat recoil energy spectra in excellent agreement with the latest SuperKamiokande data. We also show that in the presence of a neutrino transition magnetic moment of $10^{-11}$ Bohr magneton, a magnetic field of 80 KGauss eliminates all large mixing solutions other than the so-called LMA solution.Comment: 12 pages, 3 postscript figures, using elsart.cls. Published versio

Del monopolio estatal al "monopolio" privado : el rol de la alianza entre el gobierno mexicano y el Grupo Carso en la re-regulación de las telecomunicaciones (1989-2006)

A partir de los años 80, el antiguo régimen internacional de las telecomunicaciones ha sufrido importantes cambios. Los Estados impulsaron un proceso de liberalización de las telecomunicaciones que conllevó la privatización de los monopolios públicos y la desregulación de los monopolios privados del sector. La doctrina neoliberal que propugnaba la reformulación del rol de los Estados frente a sus economías, ha afectado también este sector económico. Estas transformaciones han provocado la aparición de una nueva estructura del régimen internacional de las telecomunicaciones, en la que la Unión Internacional de las Telecomunicaciones (UIT) ha cedido su rol como regulador del sector a una nueva constelación de organizaciones lideradas por la OMC. Además, otra característica relevante de esta nueva estructura es que el poder de los mercados de telecomunicaciones está centralizado en un reducido grupo de firmas multinacionales (FMN). En este contexto, es interesante estudiar las reformas de las telecomunicaciones mexicanas (1989-2006), con el objeto de comprender el actual comportamiento del mercado mexicano de las telecomunicaciones. Primeramente, analizaremos el rol jugado por la alianza establecida entre el sector privado mexicano (el Grupo Carso) y el gobierno central en el proceso de privatización de Telmex (1989-90). Seguidamente, estudiaremos el proceso de liberalización de las telecomunicaciones mexicanas en vistas a demostrar el impacto que ha tenido la consolidación de esta alianza en el mercado mexicano de las telecomunicaciones