548 research outputs found
Fate of topological states in incommensurate generalized Aubry-Andr\'e models
We study one-dimensional optical lattices described by generalized
Aubry-Andr\'e models that include both commensurate and incommensurate
modulations of the hopping amplitude. This brings together two interesting
features of this class of systems: Anderson localization and the existence of
topological edge states. We follow changes of the single-particle energy
spectrum induced by variations of the system parameters, with focus on the
survival of topological states in the localized regime.Comment: 5 pages, 5 figure
Ground-states of spin-1 bosons in asymmetric double-wells
In this work we investigate the different states of a system of spin-1 bosons
in two potential wells connected by tunneling, with spin-dependent interaction.
The model utilizes the well-known Bose-Hubbard Hamiltonian, adding a local
interaction term that depends on the modulus of the total spin in a well,
favoring a high- or low-spin state for different signs of the coupling
constant. We employ the concept of fidelity to detect critical values of
parameters for which the ground state undergoes significant changes. The nature
of the states is investigated through evaluation of average occupation numbers
in the wells and of spin correlations. A more detailed analysis is done for a
two-particle system, but a discussion of the three-particle case and some
results for larger numbers are also presented.Comment: 7 pages, 10 figure
Finite-size effects in Anderson localization of one-dimensional Bose-Einstein condensates
We investigate the disorder-induced localization transition in Bose-Einstein
condensates for the Anderson and Aubry-Andre models in the non-interacting
limit using exact diagonalization. We show that, in addition to the standard
superfluid fraction, other tools such as the entanglement and fidelity can
provide clear signatures of the transition. Interestingly, the fidelity
exhibits good sensitivity even for small lattices. Effects of the system size
on these quantities are analyzed in detail, including the determination of a
finite-size-scaling law for the critical disorder strength in the case of the
Anderson model.Comment: 15 pages, 7 figure
Pattern of mtDNA Variation in Three Populations from São Tomé e Príncipe
We have analysed the matrilineal genetic composition of three self-reported ethnic groups from São Tomé e Príncipe (Gulf of Guinea), an African archipelago whose settlement begun in the late fifteenth century. Sequence data from the hypervariable segments I (HVS-I) and II (HVS-II) were obtained for 30 Angolares, 35 Forros and 38 Tongas. The repertory of mtDNA lineages in São Tomé e Príncipe denoted a fully African maternal pool, primarily arisen from a Central/Southwestern substratum. The absence of any lineages of putative European descent means that the European impact at the mitochondrial pool was virtually nil. Angolares showed a clear reduction of mtDNA diversity and a slight genetic differentiation relative to Tongas or Forros, whereas the latter two groups did not present any signs of genetic boundaries between each other. The data obtained here reinforce the depiction of genetic substructuring in São Tomé e Príncipe previously derived from Y-chromosome STRs. In addition, the crossing of mtDNA and Y-STR information led to the inference that the female mediated gene flow within the archipelago was less restricted than the male, a pattern that could be framed in the cultural traditions and socio-historical interactions among the groups
Critical exponents of the disorder-driven superfluid-insulator transition in one-dimensional Bose-Einstein condensates
We investigate the nature of the superfluid-insulator quantum phase
transition driven by disorder for non-interacting ultracold atoms on
one-dimensional lattices. We consider two different cases: Anderson-type
disorder, with local energies randomly distributed, and pseudo-disorder due to
a potential incommensurate with the lattice, which is usually called the
Aubry-Andr\'e model. A scaling analysis of numerical data for the superfluid
fraction for different lattice sizes allows us to determine quantum critical
exponents characterizing the disorder-driven superfluid-insulator transition.
We also briefly discuss the effect of interactions close to the non-interacting
quantum critical point of the Aubry-Andr\'e model.Comment: 5 pages, 4 figure
Descritores botânicos, agronômicos e fenológicos do arroz (Oryza sativa L.).
O presente trabalho teve por objetivo apresentar os descritores morfológicos, agronômicos e fenológicos, bem como suas escalas e critérios utilizados na descrição das linhagens e genótipos de arroz, na Embrapa Arroz e Feijão, e que além de necessários para registro e proteção, são importantes para produtores e técnicos que conduzem campos de produção de sementes e úteis aos analistas que realizam análises de pureza em laboratórios oficiais e particulares de sementes.bitstream/CNPAF-2009-09/28149/1/doc_226.pd
Magnetic and superconducting instabilities in the periodic Anderson model: an RPA stud
We study the magnetic and superconducting instabilities of the periodic
Anderson model with infinite Coulomb repulsion U in the random phase
approximation. The Neel temperature and the superconducting critical
temperature are obtained as functions of electronic density (chemical pressure)
and hybridization V (pressure). It is found that close to the region where the
system exhibits magnetic order the critical temperature T_c is much smaller
than the Neel temperature, in qualitative agreement with some T_N/T_c ratios
found for some heavy-fermion materials. In our study, all the magnetic and
superconducting physical behaviour of the system has its origin in the
fluctuating boson fields implementing the infinite on-site Coulomb repulsion
among the f-electrons.Comment: 9 pages, 2 figure
Population genetic data for 17 Y STR markers from Benghazi (East Libya)
The seventeen Y-STR loci included in the AmpF‘STR1 YfilerTM PCR Amplification kit (DYS19, DYS389I,DYS389II, DYS390, DYS391, DYS392, DYS393, DYS385a/b, DYS438, DYS439, DYS437, DYS448, DYS458,DYS456, DYS635, and Y-GATA-H4) were used to type a sample population of 238 males from eastern Libya (Benghazi region). Of 238 observed haplotypes, 214 were unique (90%) and 24 (10%) were found more than once. The 17 loci gave a discriminating power of 0.999. DYS458 showed the highest diversity as a single-locus marker (0.73). Allelic frequencies and gene diversities for each Y-STR locus were determined. The high haplotype diversity and discrimination capacity (0.996) demonstrate the utility of
these loci for human identification in forensic applications. Comparative analysis with Y-STR datasets of
relevant populations and submission of the haplotypes to the Y-STR Haplotype Reference Database (YHRD) was undertaken
Atividades do banco ativo de germoplasma de feijoeiro comum (Phaseolus vulgaris L.) da Embrapa.
O Banco Ativo de Germoplasma de Feijão, em parceria com a Embrapa Recursos Genéticos e Biotecnologia, tem contribuído com a comunidade científica através do enriquecimento da variabilidade genética, disponibilizando mais de 14.000 acessos, com mais de 29.000 amostras distribuídas entre a comunidade científica em geral, o que evidencia a preocupação com problemas como a fome e o desenvolvimento de uma agricultura sustentável
Características agronômicas, botânicas, e fenológicas de genótipos de arroz-vermelho.
O objetivo deste trabalho foi apresentar algumas informações sobre os genótipos de arroz-vermelho coletados em regiões brasileiras
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