Paired states of interacting electrons in a two dimensional lattice

We show that two tight binding electrons that repel may form a bounded pair in two dimensions. The paired states form a band with energies that scale like the strength of the interaction potential. By applying an electric field we show that the dynamics of such states is that of a composite particle of charge 2e. The system still sustains Bloch-like states, so that if the two bands overlap single and paired states might coexist allowing for a bosonic fluid component that, if condensed, would decrease the resistance at low temperatures. The presence of two bands allows for new oscillations whose experimental detection would permit a direct measurement of the interaction potential strength.Comment: 7 pages, 3 figure

Species richness and beta-diversity of aquatic macrophytes assemblages in three floodplain tropical lagoons: evaluating the effects of sampling size and depth gradients

Using aquatic macrophyte data gathered in three lagoons of the Paraná River floodplain we showed a strong effect of sample size on species richness. Incidence-based species richness estimators (Chao 2, jackknife 1, jackknife 2, incidence-based coverage estimator and bootstrap) were compared to evaluate their performance in estimating the species richness throughout transect sampling rnethod. Our results suggest that the best estimate of the species richness was gave by jackknife 2 estimator. Nevertheless, the transect sampling design was considered inappropriate to estimate aquatic macrophytes species richness. Depth gradient was not a good predictor of the species richness and species turnover (beta diversity). The dynamics of these environments, subject to high water-level fluctuation prevents the formation and permanence of a clear floristic depth-related gradient

Restrictions over two-dimensional gauge models with Thirring-like interaction

Some years ago, it was shown how fermion self-interacting terms of the Thirring-type impact the usual structure of massless two-dimensional gauge theories [1]. In that work only the cases of pure vector and pure chiral gauge couplings have been considered and the corresponding Thirring term was also pure vector and pure chiral respectively, such that the vector (or chiral) Schwinger model should not lose its chirality structure due to the addition of the quartic interaction term. Here we extend this analysis to a generalized vector and axial coupling both for the gauge interaction and the quartic fermionic interactions. The idea is to perform quantization without losing the original structure of the gauge coupling. In order to do that we make use of an arbitrariness in the definition of the Thirring-like interaction.Comment: 9 pages, no figure

Comment on "Weyl fermions and the anomalous Hall effect in metallic ferromagnets"

We point out that, contrary to an assertion by Chen, Bergman and Burkov [Phys. Rev. B 88, 125110 (2013)], the non-quantized part of the intrinsic anomalous Hall conductivity can indeed be expressed as a Fermi-surface property even when Weyl points are present in the bandstructure.Comment: Submitted to Physical Review

Intersectionality, Resistance, and History-Making: A Conversation Between Carolyn D'Cruz, Ruth DeSouza, Samia Khatun, and Crystal McKinnon, Facilitated by Jordana Silverstein

A good, solid, history-writing practice is one which, I think, shakes people's ideas of the world and their place in it, compelling them to imagine new social, cultural and political formations which can provide an account of life. Kimberle Crenshaw's development of the term 'intersectionality', and the ways it has been taken up by people of colour within the academy internationally, as well as by activists, provides one example of such imaginative work. Because when you spend some time in the Australian History academic scene, at conferences, in departments, talking to other academics, it's quickly noticeable that one of its key features is its hegemonic whiteness. Even in those spaces that aspire to avoid whiteness, it's inescapable, visible daily, as well as in the themes at conferences, the keynote speakers chosen, the food served, the knowledge shared. When it came time for the Australian Women's History Network conference in 2016, which carried the theme of 'Intersections in History', it felt like this could provide a way of modelling a different kind of Australian academic History space. What would a conversation look like that skipped over the presence of white Anglo Australians, I wondered? What if we just left them to the side? What if we gathered together some of the smartest, sharpest thinkers in Melbourne academia, and spoke amongst ourselves, coming up with new formations of knowledge? And so we did: Crystal, Samia, Ruth and Carolyn gathered together, I asked them some questions, and we had a conversation that, in numerous ways, challenged white hegemonies. We've recreated some of that conversation below, as a way of continuing to think together, and to find new ways of making this thinking public