A random version of Simons' inequality

The purpose of this paper is to provide a random version of Simons' inequality

Symmetry characterization of the collective modes of the phase diagram of the ν=0\nu=0 quantum Hall state in graphene: Mean-field and spontaneously broken symmetries

We devote this work to the study of the mean-field phase diagram of the $\nu=0$ quantum Hall state in bilayer graphene and the computation of the corresponding neutral collective modes, extending the results of recent works in the literature. Specifically, we provide a detailed classification of the complete orbital-valley-spin structure of the collective modes and show that phase transitions are characterized by singlet modes in orbital pseudospin, which are independent of the Coulomb strength and suffer strong many-body corrections from short-range interactions at low momentum. We describe the symmetry breaking mechanism for phase transitions in terms of the valley-spin structure of the Goldstone modes. For the remaining phase boundaries, we prove that the associated exact $SO(5)$ symmetry existing at zero Zeeman energy and interlayer voltage survives as a weaker mean-field symmetry of the Hartree-Fock equations. We extend the previous results for bilayer graphene to the monolayer scenario. Finally, we show that taking into account Landau level mixing through screening does not modify the physical picture explained above.Comment: 44 pages, 10 figure

String amplitudes in the Hpp-wave limit of AdS3xS3

We compute string amplitudes on pp-waves supported by NS-NS 3-form fluxes and arising in the Penrose limit of AdS3xS3xM. We clarify the role of the non-chiral accidental SU(2) symmetry of the background. We comment on the extension of our results to the superstring and propose a holographic formula in the BMN limit of the AdS3/CFT2 correspondence valid for any correlator.Comment: Latex,no figures, 47 p

Elections in Ecuador: An Emerging Alternative beyond the Left-Right Antagonism

On 11 April 2021 Ecuador's presidential run-off election will take place between leftist candidate Andrés Arauz from the UNES coalition and right-wing conservative Guillermo Lasso from the PSC-CREO alliance. Though this appears to be a conventional left-right battle, the successful first-round performance of Yaku Pérez from Pachakutik and Xavier Hervas from the ID surprised many observers. Ecuador's run-off represents the choice between two opposing models of development. Arauz seeks to advance ex-president Rafael Correa's anti-neoliberal "Citizen Revolution," while Lasso promotes the old neoliberal agenda. Both contenders are betting on revenues from extractivism to fund their development plans. In the first round, Arauz and Lasso avoided taking firm stances on issues related to the environment, gender, and sexual minorities. For the run-off, they have both "greened" their agendas and spun their positions as "women- and LGBT-friendly," recognizing the success of alternative third forces led by Pachakutik and the Izquierda Democrática (ID). Despite a left majority in the legislature, creating a unified leftist front is wishful thinking. The differences between Unión por la Esperanza (UNES) and Pachakutik are irreconcilable: the former seems incapable of turning away from its founding figure, Correa, and the indigenous movement continues to be internally fragmented. As both run-off candidates combined received only a little over half of the first-round vote, endorsements are currently a crucial battleground for the finalists. Pachakutik and the ID have announced they will support neither Arauz nor Lasso. The political tradition in Ecuador indicates that votes are not easily transferred, due to voters' weak identification with programmatic militancy and ideology. Whoever wins the presidential run-off will have to deal with an urgent and profound socio-economic crisis reinforced by the COVID-19 pandemic

Bound-state dark matter with Majorana neutrinos

We propose a simple scenario in which dark matter (DM) emerges as a stable neutral hadronic thermal relics, its stability following from an exact $\operatorname{U}(1)_D$ symmetry. Neutrinos pick up radiatively induced Majorana masses from the exchange of colored DM constituents. There is a common origin for both dark matter and neutrino mass, with a lower bound for neutrinoless double beta decay. Direct DM searches at nuclear recoil experiments will test the proposal, which may also lead to other phenomenological signals at future hadron collider and lepton flavour violation experiments.Comment: 9 pages, 4 figures. arXiv admin note: text overlap with arXiv:1803.0852

Design and evaluation of a no-tillage seeder for small scale vegetable production using a two-wheeled tractor in Coahuila, Mexico

Currently used conventional tillage systems for small-scale vegetable production in the region of Saltillo, Coahuila, Mexico require a considerable amount of hand labor, energy and materials for all activities. Seedbed preparation can require up to 60% of the total production cost in some systems in Mexico. Further, soil is degraded and eroded due to the system. Conservation tillage may reduce costs and prevent soil degradation, but appropriate tools, such as, no-tillage seeders for small-scale farmers are not available. This papers reports on the design and construction of a prototype of a no-tillage seeder for small-scale conservation tillage using a 2-wheeled tractor. Three main functions received particular attention: opening of the soil, placing seed and/or fertilizer and closing the slot. Because of its vapor conservation and good seedling emergence, tools to create T-shaped slots were chosen, with adapted depth control and closing and covering devices. A systematic design process was applied in order to reach the required decisions. Function diagrams were defined from where morphologic charts guided the selection of the configuration of the seeder. A preliminary evaluation included testing of two furrow opener disc types (notched and fluted), and four crop residue levels, 0, 30, 60 and 100%, with respect to performance of the seeder. An evaluation showed that with low cover amounts a consistent and firm seed cover was obtained, but emergence quality decreased due to insufficient residue cover. The notched disc had a better performance than the fluted disc. The inverted T-shape in the soil was not always sustained due to technical flaws. It was possible to build a prototype under 2000 dollars with basic tools in a local workshop. Further research will focus on the biological performance and improvement of the mechanical components and performance