General tête-à-tête graphs and Seifert manifolds

Tête-à-tête graphs and relative tête-à-tête graphs were introduced by N. A’Campo in 2010 to model monodromies of isolated plane curves. By recent work of Fdez de Bobadilla, Pe Pereira and the author, they provide a way of modeling the periodic mapping classes that leave some boundary component invariant. In this work we introduce the notion of general tête-à-tête graph and prove that they model all periodic mapping classes. We also describe algorithms that take a Seifert manifold and a horizontal surface and return a tête-à-tête graph and vice versa

Mixed tête-à-tête twists as monodromies associated with holomorphic function germs

Tête-à-tête graphs were introduced by N. A’Campo in 2010 with the goal of modeling the monodromy of isolated plane curves. Mixed tête-à-tête graphs provide a generalization which define mixed tête-à-tête twists, which are pseudo-periodic automorphisms on surfaces. We characterize the mixed tête-à-tête twists as those pseudo-periodic automorphisms that have a power which is a product of right-handed Dehn twists around disjoint simple closed curves, including all boundary components. It follows that the class of tête-à-tête twists coincides with that of monodromies associated with reduced function germs on isolated complex surface singularities. Finally, using the language of plumbing calculus, we relate horizontal open book decompositions of graph manifolds with mixed tête-à-tête graphs via two algorithms

Direct estimation of electron density in the Orion Bar PDR from mm-wave carbon recombination lines

A significant fraction of the molecular gas in star-forming regions is irradiated by stellar UV photons. In these environments, the electron density (n_e) plays a critical role in the gas dynamics, chemistry, and collisional excitation of certain molecules. We determine n_e in the prototypical strongly irradiated photodissociation region (PDR), the Orion Bar, from the detection of new millimeter-wave carbon recombination lines (mmCRLs) and existing far-IR [13CII] hyperfine line observations. We detect 12 mmCRLs (including alpha, beta, and gamma transitions) observed with the IRAM 30m telescope, at ~25'' angular resolution, toward the H/H2 dissociation front (DF) of the Bar. We also present a mmCRL emission cut across the PDR. These lines trace the C+/C/CO gas transition layer. As the much lower frequency carbon radio recombination lines, mmCRLs arise from neutral PDR gas and not from ionized gas in the adjacent HII region. This is readily seen from their narrow line profiles (dv=2.6+/-0.4 km/s) and line peak LSR velocities (v_LSR=+10.7+/-0.2 km/s). Optically thin [13CII] hyperfine lines and molecular lines - emitted close to the DF by trace species such as reactive ions CO+ and HOC+ - show the same line profiles. We use non-LTE excitation models of [13CII] and mmCRLs and derive n_e = 60-100 cm^-3 and T_e = 500-600 K toward the DF. The inferred electron densities are high, up to an order of magnitude higher than previously thought. They provide a lower limit to the gas thermal pressure at the PDR edge without using molecular tracers. We obtain P_th > (2-4)x10^8 cm^-3 K assuming that the electron abundance is equal or lower than the gas-phase elemental abundance of carbon. Such elevated thermal pressures leave little room for magnetic pressure support and agree with a scenario in which the PDR photoevaporates.Comment: Accepted for publication in A&A Letters (includes language editor corrections

Validación experimental de un modelo de músculo activado de forma artificial

Postprint (published version

Information on activities other than fishing (offshore oil and gas) in the NAFO Convention Area: Implications for the development of the Ecosystem Summary Sheets (Divisions 3LNO and 3M)

Updated available information on activities other than fishing in the NAFO Convention Area - with focus on oil and gas - was collected and summarized from publicly available data sources (e.g. websites and project reports). This information is relevant not only to produce advice on Commission Request #14, but also to the development of the ecosystem summary sheets for Divisions 3LNO and 3M (Commission Request #15). In general, data on geographical location of oil and gas activities is available (including spatial location and technical details of a development project in the Flemish Pass), but information on the adverse impacts of such activities (e.g. routine operations, accidental events, unauthorized discharges, exploratory drilling on VME closed areas, etc.), as well as mitigation measures, is scarce or difficult to obtain. Based on the available information, it is observed that offshore oil and gas activities in NAFO Divs. 3LNM increased in recent years, including drilling activities on NAFO VME closed areas (Areas 2 and 10). Moreover, a number of different types of “incidents” have occurred during the period 2015-2020 (e.g. the Hibernia oil spill in 2019, a transboundary incident, in which the oil was extended into the NAFO Regulatory Area).European Union’s Horizon 2020, No 678760 (ATLAS).Postprint

Deep-sea: Vulnerable Marine Ecosystems in the North Atlantic Ocean: NEREIDA & ECOVUL/ARPA projects

Charla presentada en la DG Mare. European Commission. Directorate General for Maritime Affairs and Fisherie