Clock spectroscopy of interacting bosons in deep optical lattices

We report on high-resolution optical spectroscopy of interacting bosonic $^{174}$Yb atoms in deep optical lattices with negligible tunneling. We prepare Mott insulator phases with singly- and doubly-occupied isolated sites and probe the atoms using an ultra-narrow "clock" transition. Atoms in singly-occupied sites undergo long-lived Rabi oscillations. Atoms in doubly-occupied sites are strongly affected by interatomic interactions, and we measure their inelastic decay rates and energy shifts. We deduce from these measurements all relevant collisional parameters involving both clock states, in particular the intra- and inter-state scattering lengths

World natural gas endowment as a bridge towards zero carbon emissions

We use global energy market (GEM) model to show that natural gas has the potential to help stabilize global carbon emissions in a span of about 50-100 years and pave the way towards low and zero carbon energy. The GEM provides a close fit of the global energy mix between 1850 and 2005. It also matches historical carbon and CO2 emissions generated by the combination of fossil fuels. The model is used them to forecast the future energy mix, as well as the carbon and CO2 emissions, up to the year 2150. Historical data show relative decarbonization and an increase in the amount of hydrogen burned as a percent of fossil fuel use between 1850 and 1970. The GEM indicates that with a larger contribution of natural gas to the future energy market, the burned hydrogen percentage will increase. This decarbonization will help to advance economic and environmental sustainability

Link Between Endowments, Economics and Environment in Conventinal and unconventional Gas Reservoirs

This paper presents a methodology for connecting endowments, economics and the environment in conventional, tight, shale and Coalbed Methane (CBM) reservoirs. The volumetric estimates are generated by a Variable Shape Distribution model (VSD). The VSD has been shown in the past to be useful for the evaluation of conventional and tight gas reservoirs. However, this is the first paper in which the method is used to also include shale gas and CBM formations. Results indicate a total gas endowment of 70,000 tcf, split between 15,000 tcf in conventional reservoirs, 15,000 tcf in tight gas, 30,000 tcf in shale gas and 10,000 tcf in CBM reservoirs. Thus, natural gas formations have potential to provide a significant contribution to global energy demand estimated at approximately 790 quads by 2035. A common thread between unconventional formations is that nearly all of them must be hydraulically fractured to attain commercial production. A significant volume of data indicates that the probabilities of hydraulic fracturing (fracking) fluids and/or methane contaminating ground water through the hydraulically-created fractures are very low. Since fracking has also raised questions about the economic viability of producing unconventional gas in some parts of the world, supply curves are estimated in this paper for the global gas portfolio. The curves show that, in some cases, the costs of producing gas from unconventional reservoirs are comparable to those of conventional gas. The conclusion is that there is enough natural gas to supply the energy market for nearly 400 years at current rates of consumption and 110 years with a growth rate in production of 2% per year. With appropriate regulation, this may be done safely, commercially, and in a manner that is more benign to the environment as compared with other fossil fuels

Non-linear Relaxation of Interacting Bosons Coherently Driven on a Narrow Optical Transition

We study the dynamics of a two-component Bose-Einstein condensate (BEC) of $^{174}$Yb atoms coherently driven on a narrow optical transition. The excitation transfers the BEC to a superposition of states with different internal and momentum quantum numbers. We observe a crossover with decreasing driving strength between a regime of damped oscillations, where coherent driving prevails, and an incoherent regime, where relaxation takes over. Several relaxation mechanisms are involved: inelastic losses involving two excited atoms, leading to a non-exponential decay of populations; Doppler broadening due to the finite momentum width of the BEC and inhomogeneous elastic interactions, both leading to dephasing and to damping of the oscillations. We compare our observations to a two-component Gross-Pitaevskii (GP) model that fully includes these effects. For small or moderate densities, the damping of the oscillations is mostly due to Doppler broadening. In this regime, we find excellent agreement between the model and the experimental results. For higher densities, the role of interactions increases and so does the damping rate of the oscillations. The damping in the GP model is less pronounced than in the experiment, possibly a hint for many-body effects not captured by the mean-field description.Comment: 7 pages, 4 figures; supplementary material available as ancillary fil

Asymptotic iteration method for eigenvalue problems

An asymptotic interation method for solving second-order homogeneous linear differential equations of the form y'' = lambda(x) y' + s(x) y is introduced, where lambda(x) \neq 0 and s(x) are C-infinity functions. Applications to Schroedinger type problems, including some with highly singular potentials, are presented.Comment: 14 page

Frame synchronization performance and analysis

The analysis used to generate the theoretical models showing the performance of the frame synchronizer is described for various frame lengths and marker lengths at various signal to noise ratios and bit error tolerances

De la “Europa de las Regiones” a la Europa con las Regiones

L’autor comença per analitzar el procés de transformació que està passant l’Estat-nació a mans del triple fenomen de la globalització, l’europeïtzació i la regionalització. Aquest darrer, a més, es veu clarament afectat pels dos primers i s’ha generat un ressorgiment del neoregionalisme. Pel que fa a la incidència de la Unió Europea sobre les regions, l’autor nega que s’estiguin erosionant les identitats etnoterritorials i considera, per contra, que davant de la manca d’un demos europeu la clau del procés de construcció europea rau en saber combinar les molt diverses identitats que conviuen a Europa. Des del punt de vista de les regions, d’altra banda, l’autor posa de manifest les seves diferències d’interessos i el seu elevat nombre, factors que, entre altres, impedeixen que puguin ser els actors principals de la construcció europea, però no que hi contribueixin. No es tracta tant de parlar d’una Europa de les regions com d’una Europa amb les regions, les quals tindran el seu espai com el tenen els estats, que seguiran essent els principals protagonistes. L’autor, finalment, analitza el paper dels partits nacionalistes subestatals, els límits del Comitè de les Regions com a catalitzador dels interessos regionals, i el pes i les estratègies de les regions a Alemanya, Bèlgica i el Regne Unit.In this article the author begins by analyzing the process of transformation taking place within state-nations at the hands of the triple phenomenon of globalisation, Europeisation and regionalisation. The latter, furthermore, is clearly being affected by the first two and has generated a resurgence of neo-regionalism. In regard to the influence of the European Union on the regions, the author denies that it is eroding ethnic-territorial identities and considers, on the other hand, that in view of the lack of a European demos, the key to the process of the construction of Europe lies in knowing how to combine the extremely varied identities living together in Europe. From the point of view of the regions, on the other hand, the author points out the enormous number of different interests, factors which, among others, prevent them from being the main forces behind the construction of Europe, but not from making a contribution. It is not so much to speak of a Europe of regions as of a Europe with regions, all of which have their own space, as do the states, who will continue to be the main decision-makers. The author, finally, analyzes the role of sub-state nationalist parties, the limits of the Committee of the Regions as a catalyst for regional interests, and the weight and strategies of regions in Germany, Belgium and the United Kingdom.1. La teoría de la “Europa de las regiones”. – 2. Estrategias regionalistas de los actores políticos. – 3. Los límites del Comité de las Regiones. – 4. Perspectiva comparada. – 5. Una nota conclusiva. – Bibliografía citada