3,112 research outputs found
The Politics of Labeling in International Relations: The Case of the So-Called aoCoup daEtat of March 2009a in Madagascar
The consecutive and unconstitutional transfers of power which occurred in Madagascar on March 17 2009 between on the one hand President Marc Ravalomanana and the Military Directorate and on the other hand the Military Directorate and Andry Rajoelina have been labeled and condemned as a coup d tat by the great majority of the members of the international community However despite this quasi-unanimity the different members of the international community adopted different responses in dealing with this so-called coup d tat Using the labeling approach this study analyzes the rules and procedures of the relevant members of the international community in dealing with a coup d tat in general and their actual responses in the particular case of Madagascar This study finds on the one hand that the rules and procedures of the relevant members of the international community in dealing with a coup d tat were completely different on the other hand that their actual responses were usually inconsistent with their own rules and procedure
Spin-orbit resonances and rotation of coorbital bodies in quasi-circular orbits
The rotation of asymmetric bodies in eccentric Keplerian orbits can be
chaotic when there is some overlap of spin-orbit resonances. Here we show that
the rotation of two coorbital bodies (two planets orbiting a star or two
satellites of a planet) can also be chaotic even for quasi-circular orbits
around the central body. When dissipation is present, the rotation period of a
body on a nearly circular orbit is believed to always end synchronous with the
orbital period. Here we demonstrate that for coorbital bodies in quasi-circular
orbits, stable non-synchronous rotation is possible for a wide range of mass
ratios and body shapes. We further show that the rotation becomes chaotic when
the natural rotational libration frequency, due to the axial asymmetry, is of
the same order of magnitude as the orbital libration frequency
Wilson loop approach to fragile topology of split elementary band representations and topological crystalline insulators with time reversal symmetry
We present a general methodology towards the systematic characterization of
crystalline topological insulating phases with time reversal symmetry (TRS).~In
particular, taking the two-dimensional spinful hexagonal lattice as a proof of
principle we study windings of Wilson loop spectra over cuts in the Brillouin
zone that are dictated by the underlying lattice symmetries.~Our approach finds
a prominent use in elucidating and quantifying the recently proposed
``topological quantum chemistry" (TQC) concept.~Namely, we prove that the split
of an elementary band representation (EBR) by a band gap must lead to a
topological phase.~For this we first show that in addition to the Fu-Kane-Mele
classification, there is -symmetry protected
classification of two-band subspaces that is obstructed by the
other crystalline symmetries, i.e.~forbidding the trivial phase. This accounts
for all nontrivial Wilson loop windings of split EBRs \textit{that are
independent of the parameterization of the flow of Wilson loops}.~Then, we show
that while Wilson loop winding of split EBRs can unwind when embedded in
higher-dimensional band space, two-band subspaces that remain separated by a
band gap from the other bands conserve their Wilson loop winding, hence
revealing that split EBRs are at least "stably trivial", i.e. necessarily
non-trivial in the non-stable (few-band) limit but possibly trivial in the
stable (many-band) limit.~This clarifies the nature of \textit{fragile}
topology that has appeared very recently.~We then argue that in the many-band
limit the stable Wilson loop winding is only determined by the Fu-Kane-Mele
invariant implying that further stable topological phases must
belong to the class of higher-order topological insulators.Comment: 27 pages, 13 figures, v2: minor corrections, new references included,
v3: metastable topology of split EBRs emphasized, v4: prepared for
publicatio
Exploring the Limitations of Behavior Cloning for Autonomous Driving
Driving requires reacting to a wide variety of complex environment conditions
and agent behaviors. Explicitly modeling each possible scenario is unrealistic.
In contrast, imitation learning can, in theory, leverage data from large fleets
of human-driven cars. Behavior cloning in particular has been successfully used
to learn simple visuomotor policies end-to-end, but scaling to the full
spectrum of driving behaviors remains an unsolved problem. In this paper, we
propose a new benchmark to experimentally investigate the scalability and
limitations of behavior cloning. We show that behavior cloning leads to
state-of-the-art results, including in unseen environments, executing complex
lateral and longitudinal maneuvers without these reactions being explicitly
programmed. However, we confirm well-known limitations (due to dataset bias and
overfitting), new generalization issues (due to dynamic objects and the lack of
a causal model), and training instability requiring further research before
behavior cloning can graduate to real-world driving. The code of the studied
behavior cloning approaches can be found at
https://github.com/felipecode/coiltraine
Microbial carbon use efficiency predicted from genome-scale metabolic models
Respiration by soil bacteria and fungi is one of the largest fluxes of carbon (C) from the land surface. Although this flux is a direct product of microbial metabolism, controls over metabolism and their responses to global change are a major uncertainty in the global C cycle. Here, we explore an in silico approach to predict bacterial C-use efficiency (CUE) for over 200 species using genome-specific constraint-based metabolic modeling. We find that potential CUE averages 0.62 ± 0.17 with a range of 0.22 to 0.98 across taxa and phylogenetic structuring at the subphylum levels. Potential CUE is negatively correlated with genome size, while taxa with larger genomes are able to access a wider variety of C substrates. Incorporating the range of CUE values reported here into a next-generation model of soil biogeochemistry suggests that these differences in physiology across microbial taxa can feed back on soil-C cycling.Published versio
- …