A Berger type normal holonomy theorem for complex submanifolds

We prove a kind of Berger-Simons' Theorem for the normal holonomy group of a complex submanifold of the projective spac

A Cellular Automaton Model for the Traffic Flow in Bogota

In this work we propose a car cellular automaton model that reproduces the experimental behavior of traffic flows in Bogot\'a. Our model includes three elements: hysteresis between the acceleration and brake gaps, a delay time in the acceleration, and an instantaneous brake. The parameters of our model were obtained from direct measurements inside a car on motorways in Bogot\'a. Next, we simulated with this model the flux-density fundamental diagram for a single-lane traffic road and compared it with experimental data. Our simulations are in very good agreement with the experimental measurements, not just in the shape of the fundamental diagram, but also in the numerical values for both the road capacity and the density of maximal flux. Our model reproduces, too, the qualitative behavior of shock waves. In addition, our work identifies the periodic boundary conditions as the source of false peaks in the fundamental diagram, when short roads are simulated, that have been also found in previous works. The phase transition between free and congested traffic is also investigated by computing both the relaxation time and the order parameter. Our work shows how different the traffic behavior from one city to another can be, and how important is to determine the model parameters for each city.Comment: 14 pages and 13 figures (gzipped tar file). Submitted to Int.J.Mod.Phys.C. Minor changes, specially at references and typoes, plus a clearer summary of the CA rule

Genetic variability within accessions of the B73 maize inbred line

The maize inbred line B73 has been extensively studied at the molecular level. Researchers now have access to the genome sequence of B73 as well as to databases of biallelic and multiallelic markers where functional poly- morphisms between B73 and a public inbred line population can be compared to relate genotypes to phenotypes. This indicates the importance to determine the genetic fidelity of the germplasm during preservation and propa- gation processes, in particular, when seeds of reference inbred lines such as B73 are maintained. The aim of this study was to assess the genetic uniformity among three different sources of the B73 inbred line by means of 75 Simple Sequence Repeats (SSRs). The three B73 sources showed homozygosis; however, some accessions dif- fered greatly from the expected locus size predicted at the reference B73 genomic sequence. A particular haplo- type was prevalent in the USDA accession PI550473. The error rate of the allele size determination was estimated. The genotyping technique used in this work allowed the separation of alleles of ± 2 bp range difference within the same electrophoresis run, whereas allele size estimations between experiments, within the laboratory, differed in ± 4 bp range difference. Besides experimental errors in genotyping, the putative cause of differences among ac- cessions could be attributed to seed contamination and genetic drift. The B73 accessions evaluated in our work can be shared among laboratories to precise genotyping and phenotyping of maize inbred lines

Creation of collective many-body states and single photons from two-dimensional Rydberg lattice gases

The creation of collective many-body quantum states from a two-dimensional lattice gas of atoms is studied. Our approach relies on the van-der-Waals interaction that is present between alkali metal atoms when laser excited to high-lying Rydberg s-states. We focus on a regime in which the laser driving is strong compared to the interaction between Rydberg atoms. Here energetically low-lying many-particle states can be calculated approximately from a quadratic Hamiltonian. The potential usefulness of these states as a resource for the creation of deterministic single-photon sources is illustrated. The properties of these photon states are determined from the interplay between the particular geometry of the lattice and the interatomic spacing.Comment: 12 pages, 8 figure

On the stability of Hamiltonian relative equilibria with non-trivial isotropy

We consider Hamiltonian systems with symmetry, and relative equilibria with isotropy subgroup of positive dimension. The stability of such relative equilibria has been studied by Ortega and Ratiu and by Lerman and Singer. In both papers the authors give sufficient conditions for stability which require first determining a splitting of a subspace of the Lie algebra of the symmetry group, with different splittings giving different criteria. In this note we remove this splitting construction and so provide a more general and more easily computed criterion for stability. The result is also extended to apply to systems whose momentum map is not coadjoint equivariant

Stability of relative equilibria with singular momentum values in simple mechanical systems

A method for testing $G_\mu$-stability of relative equilibria in Hamiltonian systems of the form "kinetic + potential energy" is presented. This method extends the Reduced Energy-Momentum Method of Simo et al. to the case of non-free group actions and singular momentum values. A normal form for the symplectic matrix at a relative equilibrium is also obtained.Comment: Partially rewritten. Some mistakes fixed. Exposition improve

Changes in mobility and socioeconomic conditions during the COVID-19 outbreak

Since the outbreak of the 2019 novel coronavirus (COVID-19) pandemic, governments have been implementing containment measures aimed at mitigating the spread of the virus, including restrictions to human mobility. The ability to adapt to the pandemic and respond to containment measures can be bound by socioeconomic conditions, which are heterogeneous in large urban areas of low-income and middle-income countries. In this paper, we analyse mobility changes following the implementation of containment measures in Bogotá, Colombia. We characterise the mobility network before and during the pandemic and analyse its evolution and changes between January and July 2020. We observe a general reduction in mobility trends, but the overall connectivity between different areas of the city remains after the lockdown, reflecting the resilience of the mobility network. Then, we estimate a gravity model to assess the effect of socioeconomic conditions on mobility flows. We find that the responses to lockdown policies depend on the socioeconomic conditions of the population. Before the pandemic, the population with better socioeconomic conditions shows higher mobility flows. Since the lockdown, mobility presents a general decrease, but the population with worse socioeconomic conditions shows lower reductions in mobility flows. We conclude by deriving policy implications.Fil: Dueñas, Marco. Universidad de Bogota Jorge Tadeo Lozano; ColombiaFil: Campi, Mercedes Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Interdisciplinario de Economía Política de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Económicas. Instituto Interdisciplinario de Economía Política de Buenos Aires; ArgentinaFil: Olmos, Luis E.. University of California; Estados Unidos. Universidad de Medellin; Colombi

The nitrogen source as a tool for weeds management

Los resultados de producción de biomasa, tanto de parte aérea como de raíz, nos muestran las distintas preferencias por una u otra fuente [(nitrato (NO3 -) o amonio(NH4 +)] de nitrógeno (N), así como La influencia de la fuente de N en la respuesta a la dosis (2 mM vs. 0,2 mM) en la zona radicular: Amaranthus viridis y Chenopodium album prefieren el NO3- y no responden a la dosis de NH4+, Conyza bonaeriensis y Solanum nigrum también prefieren NO3- pero responden a la dosis de NH4+, mientras que Sonchus oleraceus prefiere el NH4+ y no responde a la dosis de NO3 -. Igualmente, la fuente de N, y no sólo la dosis de N, tiene una gran repercusión en la relación carbono/nitrógeno (C/N) tanto de la parte aérea como de la raíz. El conjunto de los resultados sugiere que el manejo de la fuente de N en los sistemas agrícolas podría ayudar al manejo de las malas hierbas y con ello a su control, en pro de hacer una mejor optimización de los recursos.The results of biomass production both in terms of shoot and root, show distinct plants preferences for the nitrogen source; Amaranthus viridis and Chenopodium album prefers NO3 - and does not respond to the dose of NH4 +, Conyza bonaeriensis and Solanum nigrum also prefers NO3 - but respond to the dose of NH4 +, and finally Sonchus oleraceus prefers NH4 + over NO3 - and does not respond to the dose of NO3 -. Here, we also show that the source of N has a major role in plant N and C concentration. Overall, these results indicate that N fertilization (source and dose) may be a tool for the management of weeds in agricultural system where the farmer has control over the source of N applied