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  1. Article ; Online: Spin transport in non-Hermitian quantum systems

    Leonardo S. Lima

    Scientific Reports, Vol 13, Iss 1, Pp 1-

    2023  Volume 10

    Abstract: Abstract Transport in non-Hermitian quantum systems is studied. The goal is a better understanding of transport in non-Hermitian systems like the Lieb lattice due to its flat bands and the integrability of the Ising chain which allows transport in that ... ...

    Abstract Abstract Transport in non-Hermitian quantum systems is studied. The goal is a better understanding of transport in non-Hermitian systems like the Lieb lattice due to its flat bands and the integrability of the Ising chain which allows transport in that model to be computed analytically. This is a very special feature that is not present in a generic non-Hermitian system. We obtain the behaviour of the spin conductivity as a function of the non-Hermitian parameters of each system with aim to verify the influence of variation them on conductivity. For all models analyzed: Ising model as well as noninteracting fermion models, we obtain a little influence of the non-Hermitian parameters on conductivity and thus, a small effect over transport coefficients. Furthermore, we obtain an influence of opening of the gap in the spectrum in these models on longitudinal conductivity as well.
    Keywords Medicine ; R ; Science ; Q
    Language English
    Publishing date 2023-07-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Entanglement Negativity and Concurrence in Some Low-Dimensional Spin Systems

    Leonardo S. Lima

    Entropy, Vol 24, Iss 1629, p

    2022  Volume 1629

    Abstract: The influence of magnon bands on entanglement in the antiferromagnetic XXZ model on a triangular lattice, which models the bilayer structure consisting of an antiferromagnetic insulator and normal metal, is investigated. This effect was studied in ... ...

    Abstract The influence of magnon bands on entanglement in the antiferromagnetic XXZ model on a triangular lattice, which models the bilayer structure consisting of an antiferromagnetic insulator and normal metal, is investigated. This effect was studied in ferromagnetic as well as antiferromagnetic triangular lattices. Quantum entanglement measures given by the entanglement negativity have been studied, where a magnon current is induced in the antiferromagnet due to interfacial exchange coupling between localized spins in the antiferromagnet and itinerant electrons in a normal metal. Moreover, quantum correlations in other frustrated models, namely the metal-insulation antiferromagnetic bilayer model and the Heisenberg model with biquadratic and bicubic interactions, are analyzed.
    Keywords entanglement negativity ; triangular lattice ; metal-insulating antiferromagnet ; bicubic interaction ; Science ; Q ; Astrophysics ; QB460-466 ; Physics ; QC1-999
    Language English
    Publishing date 2022-11-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Dynamics based on analysis of public data for spreading of disease

    Leonardo S. Lima

    Scientific Reports, Vol 11, Iss 1, Pp 1-

    2021  Volume 11

    Abstract: Abstract The stochastic model for epidemic spreading of the novel coronavirus disease based on the data set supply by the public health agencies in countries as Brazil, United States and India is investigated. We perform a numerical analysis using the ... ...

    Abstract Abstract The stochastic model for epidemic spreading of the novel coronavirus disease based on the data set supply by the public health agencies in countries as Brazil, United States and India is investigated. We perform a numerical analysis using the stochastic differential equation in Itô’s calculus for the estimating of novel cases daily, as well as analytical calculations solving the correspondent Fokker–Planck equation for the probability density distribution of novel cases, P(N(t), t). Our results display that the model based in the Itô’s diffusion fits well to the results due to uncertainty in the official data and to the number of tests realized in populations of each country.
    Keywords Medicine ; R ; Science ; Q
    Language English
    Publishing date 2021-06-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Nonlinear Stochastic Equation within an Itô Prescription for Modelling of Financial Market

    Leonardo S. Lima

    Entropy, Vol 21, Iss 5, p

    2019  Volume 530

    Abstract: The stochastic nonlinear model based on Itô diffusion is proposed as a mathematical model for price dynamics of financial markets. We study this model with relation to concrete stylised facts about financial markets. We investigate the behavior of the ... ...

    Abstract The stochastic nonlinear model based on Itô diffusion is proposed as a mathematical model for price dynamics of financial markets. We study this model with relation to concrete stylised facts about financial markets. We investigate the behavior of the long tail distribution of the volatilities and verify the inverse power law behavior which is obeyed for some financial markets. Furthermore, we obtain the behavior of the long range memory and obtain that it follows to a distinct behavior of other stochastic models that are used as models for the finances. Furthermore, we have made an analysis by using Fokker−Planck equation independent on time with the aim of obtaining the cumulative probability distribution of volatilities <math display="inline"> <semantics> <mrow> <mi>P</mi> <mo>(</mo> <mi>g</mi> <mo>)</mo> </mrow> </semantics> </math> , however, the probability density found does not exhibit the cubic inverse law.
    Keywords price dynamics ; stochastic differential equation ; Itô calculus ; Science ; Q ; Astrophysics ; QB460-466 ; Physics ; QC1-999
    Language English
    Publishing date 2019-05-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Perfil e produção científica dos pesquisadores do CNPq nas áreas de Nefrologia e Urologia

    Eduardo A. Oliveira / Roberto Pécoits-Filho / Isabel G. Quirino / Maria Christina Oliveira / Daniela Reis Martelli / Leonardo S. Lima / Hercílio Martelli Jr

    Jornal Brasileiro de Nefrologia , Vol 33, Iss 1, Pp 31-

    2011  Volume 37

    Abstract: OBJETIVO: O objetivo deste estudo foi avaliar o perfil e a produção científica de pesquisadores de Nefrologia e Urologia, cadastrados como bolsistas de produtividade no Conselho Nacional de Desenvolvimento Científico e Tecnológico. MÉTODOS: Os currículos ...

    Abstract OBJETIVO: O objetivo deste estudo foi avaliar o perfil e a produção científica de pesquisadores de Nefrologia e Urologia, cadastrados como bolsistas de produtividade no Conselho Nacional de Desenvolvimento Científico e Tecnológico. MÉTODOS: Os currículos Lattes de 39 pesquisadores com bolsas ativas no triênio 2006 a 2008 foram incluídos na análise. As variáveis de interesse foram: sexo, instituição, tempo de doutoramento, artigos publicados, e orientação de alunos de graduação, mestres e doutores. RESULTADOS: Houve uma predominância do gênero masculino (74,4%) e de bolsistas na categoria 2 (56,4%). Três estados da federação são responsáveis por 90% dos pesquisadores: SP (28; 71,8%), RS (4; 10,3%) e MG (3; 7,7%). Quatro instituições são responsáveis por 70% dos pesquisadores: UNIFESP (14; 36%), USP (8; 20,5%), UFMG (3, 7,7%) e UNICAMP (3; 7,7%). No total da carreira acadêmica, os pesquisadores em Nefrourologia publicaram 3.195 artigos em periódicos, sendo a mediana de 75 artigos por pesquisador (IQ = 52 - 100). Os pesquisadores receberam um total de 25.923 citações na base de dados Web of Science®, sendo a mediana por pesquisador de 452 citações (IQ = 161 - 927). A média de citações por artigo foi de 13,8 citações (DP = 11,6). CONCLUSÕES: Há uma concentração dos pesquisadores na região Sudeste. Neste estudo, pode ser observado um aumento da produção científica entre a maioria dos pesquisadores nos últimos cinco anos. Através do conhecimento do perfil dos pesquisadores das áreas de Nefrologia e Urologia podem ser definidas, de maneira mais eficaz, estratégias para incentivar a produção científica e a demanda de recursos para o financiamento de projetos de pesquisa.
    Keywords indicadores de produção científica ; Nefrologia ; Ciências da Saúde ; Diseases of the genitourinary system. Urology ; RC870-923 ; Specialties of internal medicine ; RC581-951 ; Internal medicine ; RC31-1245 ; Medicine ; R
    Language Portuguese
    Publishing date 2011-03-01T00:00:00Z
    Publisher Sociedade Brasileira de Nefrologia
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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