18 research outputs found
Shell occupation by the hermit crab Dardanus insignis (Decapoda, Diogenidae) from the north Coast of São Paulo state, Brazil
Magnetic Catalysis: A Review
We give an overview of the magnetic catalysis phenomenon. In the framework of
quantum field theory, magnetic catalysis is broadly defined as an enhancement
of dynamical symmetry breaking by an external magnetic field. We start from a
brief discussion of spontaneous symmetry breaking and the role of a magnetic
field in its a dynamics. This is followed by a detailed presentation of the
essential features of the phenomenon. In particular, we emphasize that the
dimensional reduction plays a profound role in the pairing dynamics in a
magnetic field. Using the general nature of underlying physics and its
robustness with respect to interaction types and model content, we argue that
magnetic catalysis is a universal and model-independent phenomenon. In support
of this claim, we show how magnetic catalysis is realized in various models
with short-range and long-range interactions. We argue that the general nature
of the phenomenon implies a wide range of potential applications: from certain
types of solid state systems to models in cosmology, particle and nuclear
physics. We finish the review with general remarks about magnetic catalysis and
an outlook for future research.Comment: 37 pages, to appear in Lect. Notes Phys. "Strongly interacting matter
in magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A.
Schmitt, H.-U. Yee. Version 2: references adde
Pervasive gaps in Amazonian ecological research
Biodiversity loss is one of the main challenges of our time, and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes, vast areas of the tropics remain understudied. In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity, but it remains among the least known forests in America and is often underrepresented in biodiversity databases. To worsen this situation, human-induced modifications may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge, it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost
Characterization of the excitation state of picosecond laser-induced plasmas for light elements detection in metallic matrices
International audienc
Electron-impact excitation and recombination of molecular cations in cold ionized gases: application to H 2+ , BeH + , CH + , CO + , N 2+ , BF + and AlO +
International audienc
Advances in the MQDT approach of electron/molecular cation reactive collisions: High precision extensive calculations for applications
Recent advances in the stepwise multichannel quantum defect theory approach of electron/molecular cation reactive collisions have been applied to perform computations of cross sections and rate coefficients for dissociative recombination and electron-impact ro-vibrational transitions of H2+, BeH+ and their deuterated isotopomers. At very low energy, rovibronic interactions play a significant role in the dynamics, whereas at high energy, the dissociative excitation strongly competes with all other reactive processes
Advances in the MQDT approach of electron/molecular cation reactive collisions: High precision extensive calculations for applications
Recent advances in the stepwise multichannel quantum defect theory approach of electron/molecular cation reactive collisions have been applied to perform computations of cross sections and rate coefficients for dissociative recombination and electron-impact ro-vibrational transitions of H2+, BeH+ and their deuterated isotopomers. At very low energy, rovibronic interactions play a significant role in the dynamics, whereas at high energy, the dissociative excitation strongly competes with all other reactive processes
Advances in the MQDT approach of electron/molecular cation reactive collisions: High precision extensive calculations for applications
WOS:000351835100007International audienceRecent advances in the stepwise multichannel quantum defect theory approach of electron/molecular cation reactive collisions have been applied to perform computations of cross sections and rate coefficients for dissociative recombination and electron-impact rovibrational transitions of H-2(+), BeH+ and their deuterated isotopomers. At very low energy, rovibronic interactions play a significant role in the dynamics, whereas at high energy, the dissociative excitation strongly competes with all other reactive processes
Quasi-one dimensional graphite ribbon structures in the presence of a magnetic field and the on-site Coulomb correlation at half-filling
We have presented the role of the Coulomb interaction (U) and the magnetic field on the ground state properties of the quasi-one dimensional graphite ribbon structures at half-filling. Mean field Hartree-Fock Approximation is used to study the systems. To understand the boundary effects in graphite structures, we have compared the results of these systems with those of the square lattice ribbon structures. Studying the density of states, the Drude weight and the charge gap, we have drawn the U – B phase diagrams for the zigzag and the armchair graphite ribbons. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2010