Structure of multiphoton quantum optics. II. Bipartite systems, physical processes, and heterodyne squeezed states

Extending the scheme developed for a single mode of the electromagnetic field in the preceding paper ``Structure of multiphoton quantum optics. I. Canonical formalism and homodyne squeezed states'', we introduce two-mode nonlinear canonical transformations depending on two heterodyne mixing angles. They are defined in terms of hermitian nonlinear functions that realize heterodyne superpositions of conjugate quadratures of bipartite systems. The canonical transformations diagonalize a class of Hamiltonians describing non degenerate and degenerate multiphoton processes. We determine the coherent states associated to the canonical transformations, which generalize the non degenerate two--photon squeezed states. Such heterodyne multiphoton squeezed are defined as the simultaneous eigenstates of the transformed, coupled annihilation operators. They are generated by nonlinear unitary evolutions acting on two-mode squeezed states. They are non Gaussian, highly non classical, entangled states. For a quadratic nonlinearity the heterodyne multiphoton squeezed states define two--mode cubic phase states. The statistical properties of these states can be widely adjusted by tuning the heterodyne mixing angles, the phases of the nonlinear couplings, as well as the strength of the nonlinearity. For quadratic nonlinearity, we study the higher-order contributions to the susceptibility in nonlinear media and we suggest possible experimental realizations of multiphoton conversion processes generating the cubic-phase heterodyne squeezed states.Comment: 16 pages, 23 figure

Informality, Inequality and ICT in Transition economies

In this paper, we examine the role of the quality of institutional infrastructure and information and communication technology (ICT) in the relationship between the size of the informal sector (IS) and income inequality. Following our results, the sign of the relationship between IS and income inequality depends on the quality of institutions. When institutions are weak, agents invest less human capital and ICT in the formal sector (FS), thereby reducing income inequality. Utilizing panel data for sixteen transition countries we show that the relationship between the size of the IS and the level of income inequality is ambiguous. Our findings highlight the problem of measuring the relative size of the IS which is a hidden entity. We control for robustness of our findings using alternative proxies of ICT, human capital, and institutional quality and some interaction terms among these variables

A submarine volcanic eruption leads to a novel microbial habitat

Submarine volcanic eruptions are major catastrophic events that allow investigation of the colonization mechanisms of newly formed seabed. We explored the seafloor after the eruption of the Tagoro submarine volcano off El Hierro Island, Canary Archipelago. Near the summit of the volcanic cone, at about 130 m depth, we found massive mats of long, white filaments that we named Venus’s hair. Microscopic and molecular analyses revealed that these filaments are made of bacterial trichomes enveloped within a sheath and colonized by epibiotic bacteria. Metagenomic analyses of the filaments identified a new genus and species of the order Thiotrichales, Thiolava veneris. Venus’s hair shows an unprecedented array of metabolic pathways, spanning from the exploitation of organic and inorganic carbon released by volcanic degassing to the uptake of sulfur and nitrogen compounds. This unique metabolic plasticity provides key competitive advantages for the colonization of the new habitat created by the submarine eruption. A specialized and highly diverse food web thrives on the complex three-dimensional habitat formed by these microorganisms, providing evidence that Venus’s hair can drive the restart of biological systems after submarine volcanic eruption

Multipartite entangled states in particle mixing

In the physics of flavor mixing, the flavor states are given by superpositions of mass eigenstates. By using the occupation number to define a multiqubit space, the flavor states can be interpreted as multipartite mode-entangled states. By exploiting a suitable global measure of entanglement, based on the entropies related to all possible bipartitions of the system, we analyze the correlation properties of such states in the instances of three- and four-flavor mixing. Depending on the mixing parameters, and, in particular, on the values taken by the free phases, responsible for the CP-violation, entanglement concentrates in preferred bipartitions. We quantify in detail the amount and the distribution of entanglement in the physically relevant cases of flavor mixing in quark and neutrino systems. By using the wave packet description for localized particles, we use the global measure of entanglement, suitably adapted for the instance of multipartite mixed states, to analyze the decoherence induced by the free evolution dynamics on the quantum correlations of stationary neutrino beams. We define a decoherence length as the distance associated with the vanishing of the coherent interference effects among massive neutrino states. We investigate the role of the CP-violating phase in the decoherence process.Comment: 18 pages, 7 figure

Developmental perspectives on Europe

The crisis of 2008–2009 has ended, stockmarkets skyrocketed in 2012–2013, while growth of the real sector remained sluggish in Europe. This article attempts to explain the latter puzzle. Analyzing long term factors, the costs of short-termism in crisis management become obvious. The limitations of EU as a growth engine are highlighted

Prospect theory and tax evasion: a reconsideration of the Yitzhaki puzzle

The standard expected utility (EUT) model of tax evasion predicts that evasion is decreasing in the marginal tax rate (the Yitzhaki puzzle). Recent literature shows cases in which incorporating prospect theory (PT) does and does not overturn the Puzzle. In a general environment that nests both PT and EUT preferences, we provide a detailed study of how the elements of PT affect the Puzzle. PT does not always reverse the Puzzle, hence we give and interpret conditions for when it does and does not. When allowing for stigma and/or variable audit probability, PT reverses the Puzzle in the same way and with the same limitations as does EUT, if equally augmented

Exchange of nutrients and oxygen across the sediment-water interface below a Sparus aurata marine fish farm in the north-western Mediterranean Sea

Purpose: This study analyzes the effects of aquaculture activities in open seawater in the north-western coastal waters of the Mediterranean Sea. It is the first of its kind to be based on benthic flux data gathered in situ below fish farms for this particular area. Materials and methods: Samples were collected on four sampling campaigns over a 1-year cycle under a Sparus aurata fish farm facility where benthic fluxes were measured in situ using light and dark benthic chambers. Bottom water and sediment samples were also collected. Data were compared to those for a nearby control station. Results and discussion: Significant differences were found (ANOVA, p < 0. 05) between concentrations of organic matter (OM), total phosphorus and redox potentials in sediments located under the cages and those of the control station. The consumption of dissolved oxygen (DO) by sediment and positive ammonium (NH4 +) fluxes was stimulated by OM content, with correlations of r = -0. 60 (p < 0. 01) and r = 0. 70 (p < 0. 01), respectively. The OM content of sediments was found to be consistently higher under the cages than at the control station, with the highest value (1. 8 ± 0. 7 %) under the cages observed during the early summer; values of DO and NH4 + fluxes were -64 ± 17 and 12. 7 ± 1. 0 mmol m-2 day-1, respectively. PO4 3- fluxes were consistently higher in the fish farm sediments (between 0. 58 and 0. 98 mmol m-2 day-1) than those observed at the control station. Nitrate (NO3 -) fluxes were found to be consistently negative due to denitrification occurring in the sediments and were related to the concentration of NO3 - in bottom waters (r = 0. 92, p < 0. 01). Si fluxes were shown to be associated with water temperature (r = 0. 59, p < 0. 05). Conclusions: The results imply that sediments located below cages accumulate organic matter originating from aquaculture activities, especially during summer months when this activity increases. Sediments undergo biogeochemical changes that mainly affect fluxes of DO, NH4 + and soluble reactive phosphorus, although these do not seem to have a significant impact on the quality of the water column due to the hydrodynamic characteristics of the area. © 2012 Springer-Verlag.We would like to thank the Caja del Mediterraneo for a predoctoral fellowship fund for this research and Antonio Asuncion Acuigroup Maremar manager for the facilities and support in conducting the study. The translation of this paper was funded by the Universidad Politecnica de Valencia, Spain. We are grateful for the valuable comments of the anonymous reviewers on previous versions of the manuscript.Morata Higón, T.; Sospedra, J.; Falco Giaccaglia, SL.; Rodilla Alama, M. (2012). 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The energy–diversity relationship of complex bacterial communities in Arctic deep-sea sediments

The availability of nutrients and energy is a main driver of biodiversity for plant and animal communities in terrestrial and marine ecosystems, but we are only beginning to understand whether and how energy–diversity relationships may be extended to complex natural bacterial communities. Here, we analyzed the link between phytodetritus input, diversity and activity of bacterial communities of the Siberian continental margin (37–3427 m water depth). Community structure and functions, such as enzymatic activity, oxygen consumption and carbon remineralization rates, were highly related to each other, and with energy availability. Bacterial richness substantially increased with increasing sediment pigment content, suggesting a positive energy–diversity relationship in oligotrophic regions. Richness leveled off, forming a plateau, when mesotrophic sites were included, suggesting that bacterial communities and other benthic fauna may be structured by similar mechanisms. Dominant bacterial taxa showed strong positive or negative relationships with phytodetritus input and allowed us to identify candidate bioindicator taxa. Contrasting responses of individual taxa to changes in phytodetritus input also suggest varying ecological strategies among bacterial groups along the energy gradient. Our results imply that environmental changes affecting primary productivity and particle export from the surface ocean will not only affect bacterial community structure but also bacterial functions in Arctic deep-sea sediment, and that sediment bacterial communities can record shifts in the whole ocean ecosystem functioning