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Fishery management in Brazil has many challenges, including the engagement of fishers, building institutional (NGO, university, etc.) relationships to carry out research and provide key data for managers, and strengthening the capacity to articulate effective management strategies (policy institution). Here we report on recent work to address some of these challenges for the Atlantic tarpon (Megalops atlanticus) fishery in the Parnaiba Delta Protected Area. These include meetings to create inter-sector communication, citizen science and ethnobiology to support data collection and biological sampling, satellite tagging to discern tarpon movements, and the first data-limited stock assessment. The research occurred between September 2018 and April 2020 in the Parnaíba Delta and adjacent marine area, specifically in the Canárias Islands (MA), Pedra do Sal (PI), and Bitupitá (CE). Gonadosomatic indices (GSI > 5%) of female tarpon suggested that tarpon migrate to the Parnaíba Delta to spawn in the dry season (July–December). These GSI findings corresponded with the ethnobiology results in which the fishers confirmed more intense fishing effort in the dry periods due in part to the added value of the gonads. Satellite-tagged tarpon remained close to the Buraco and Boca da Barra fishery areas, thus, close to the Parnaíba Delta region. The information collected here will enhance the collaborative formulation of an unprecedented management plan for the tarpon fishery in this region.

We study for what specific values of the theoretical parameters the axion can form the totality of cold dark matter. We examine the allowed axion parameter region in the light of recent data collected by the WMAP5 mission plus baryon acoustic oscillations and supernovae [1], and assume an inflationary scenario and standard cosmology. We also upgrade the treatment of anharmonicities in the axion potential, which we find important in certain cases. If the Peccei-Quinn symmetry is restored after inflation, we recover the usual relation between axion mass and density, so that an axion mass ma (85 ± 3) μeV makes the axion 100% of the cold dark matter. If the Peccei-Quinn symmetry is broken during inflation, the axion can instead be 100% of the cold dark matter for ma < 15 meV provided a specific value of the initial misalignment angle θi is chosen in correspondence to a given value of its mass ma. Large values of the Peccei-Quinn symmetry breaking scale correspond to small, perhaps uncomfortably small, values of the initial misalignment angle θi.

The properties of axions that constitute 100% of cold dark matter (CDM) depend on the tensor-to-scalar ratio \\(r\\) at the end of inflation. If \\(r=0.20^{+0.07}_{-0.05}\\) as reported by the BICEP2 collaboration, then \"half\" of the CDM axion parameter space is ruled out. Namely, the Peccei-Quinn symmetry must be broken after the end of inflation, and axions do not generate non-adiabatic primordial fluctuations. The cosmic axion density is then independent of the tensor-to-scalar ratio \\(r\\), and the axion mass is expected to be in a narrow range that however depends on the cosmological model before primordial nucleosynthesis. In the standard \\(\\Lambda\\)CDM cosmology, the CDM axion mass range is \\(m_a = \\left(71 \\pm 2\\right) \\mu{\\rm eV} \\, (\\alpha^{\\rm dec}+1)^{6/7}\\), where \\(\\alpha^{\\rm dec}\\) is the fractional contribution to the cosmic axion density from decays of axionic strings and walls.

In the framework of a bimetric model, we discuss a relation between the (modified) Friedmann equations and a mechanical system similar to the quantum Hall effect problem. Firstly, we show how these modified Friedmann equations are mapped to an anisotropic two-dimensional charged harmonic oscillator in the presence of a constant magnetic field, with the frequencies of the oscillator playing the role of the cosmological constants. This problem has two energy scales leading to the identification of two different regimes, namely, one dominated by the cosmological constants, with exponential expansions for the scale factors, and the other dominated by a magnetic seed, which would be responsible for both a component of dark energy and a primordial magnetic field. The latter regime would be described by a (nonperturbative) mapping between the cosmological evolution and the quantum Hall effect.

The interaction between two initially causally disconnected regions of the universe is studied using analogies of non-commutative quantum mechanics and deformation of Poisson manifolds. These causally disconnect regions are governed by two independent Friedmann-Lema\\^ıtre-Robertson-Walker (FLRW) metrics with scale factors \\(a\\) and \\(b\\) and cosmological constants \\(\\Lambda_a\\) and \\(\\Lambda_b\\), respectively. The causality is turned on by positing a non-trivial Poisson bracket \\([ {\\cal P}_{\\alpha}, {\\cal P}_{\\beta} ] =\\epsilon_{\\alpha \\beta}\\frac{\\kappa}{G}\\), where \\(G\\) is Newton's gravitational constant and \\(\\kappa \\) is a dimensionless parameter. The posited deformed Poisson bracket has an interpretation in terms of 3-cocycles, anomalies and Poissonian manifolds. The modified FLRW equations acquire an energy-momentum tensor from which we explicitly obtain the equation of state parameter. The modified FLRW equations are solved numerically and the solutions are inflationary or oscillating depending on the values of \\(\\kappa\\). In this model the accelerating and decelerating regime may be periodic. The analysis of the equation of state clearly shows the presence of dark energy. By completeness, the perturbative solution for \\(\\kappa \\ll1 \\) is also studied.

The flat rotation curve obtained for the outer star clusters of the Large Magellanic Cloud is suggestive of an LMC dark matter halo. From the composite HI and star cluster rotation curve, I estimate the parameters of an isothermal dark matter halo added to a `maximum disk.' I then examine the possibility of detecting high energy gamma-rays from non-baryonic dark matter annihilations in the central region of the Large Magellanic Cloud.

Unstable relics with lifetime longer than the age of the Universe could be the dark matter today. Electrons, photons and neutrinos are a natural outcome of their decay and could be searched for in cosmic rays and in \\(\\gamma\\)-ray and neutrino detectors. I compare the sensitivities of these three types of searches to the mass and lifetime of a generic unstable particle. I show that if the relics constitute our galactic halo and their branching ratios into electron-positrons, photons and neutrinos are comparable, neutrino searches would probe the longest lifetimes for masses \\(\\simge 40 \\TeV\\), while electron-positron searches would be better but more uncertain for lighter particles. If instead the relics are not clustered in our halo, neutrinos are more sensitive a probe than \\(\\gamma\\)-rays for masses \\(\\simge 700 \\GeV\\). A \\( 1 \\sqkm \\) neutrino telescope should be able to explore lifetimes up to \\( \\sim 10^{30} \\sec \\) while searching for neutrinos from unstable particles above the atmospheric background.

Cosmological observations indicate that most of the matter in the Universe is Dark Matter. Dark Matter in the form of Weakly Interacting Massive Particles (WIMPs) can be detected directly, via its elastic scattering off target nuclei. Most current direct detection experiments only measure the energy of the recoiling nuclei. However, directional detection experiments are sensitive to the direction of the nuclear recoil as well. Due to the Sun's motion with respect to the Galactic rest frame, the directional recoil rate has a dipole feature, peaking around the direction of the Solar motion. This provides a powerful tool for demonstrating the Galactic origin of nuclear recoils and hence unambiguously detecting Dark Matter. Furthermore, the directional recoil distribution depends on the WIMP mass, scattering cross section and local velocity distribution. Therefore, with a large number of recoil events it will be possible to study the physics of Dark Matter in terms of particle and astrophysical properties. We review the potential of directional detectors for detecting and characterizing WIMPs.

The first stars to form in the Universe may be powered by the annihilation of weakly interacting dark matter particles. These so-called dark stars, if observed, may give us a clue about the nature of dark matter. Here we examine which models for particle dark matter satisfy the conditions for the formation of dark stars. We find that in general models with thermal dark matter lead to the formation of dark stars, with few notable exceptions: heavy neutralinos in the presence of coannihilations, annihilations that are resonant at dark matter freeze-out but not in dark stars, some models of neutrinophilic dark matter annihilating into neutrinos only and lighter than about 50 GeV. In particular, we find that a thermal DM candidate in standard Cosmology always forms a dark star as long as its mass is heavier than about 50 GeV and the thermal average of its annihilation cross section is the same at the decoupling temperature and during the dark star formation, as for instance in the case of an annihilation cross section with a non-vanishing s-wave contribution.