4,519 research outputs found
Derived bracket construction and Manin products
We will extend the classical derived bracket construction to any algebra over
a binary quadratic operad. We will show that the derived product construction
is a functor given by the Manin white product with the operad of permutation
algebras. As an application, we will show that the operad of prePoisson
algebras is isomorphic to Manin black product of the Poisson operad with the
preLie operad. We will show that differential operators and Rota-Baxter
operators are, in a sense, Koszul dual to each other.Comment: This is the final versio
Critical behavior at Mott-Anderson transition: a TMT-DMFT perspective
We present a detailed analysis of the critical behavior close to the
Mott-Anderson transition. Our findings are based on a combination of numerical
and analytical results obtained within the framework of Typical-Medium Theory
(TMT-DMFT) - the simplest extension of dynamical mean field theory (DMFT)
capable of incorporating Anderson localization effects. By making use of
previous scaling studies of Anderson impurity models close to the
metal-insulator transition, we solve this problem analytically and reveal the
dependence of the critical behavior on the particle-hole symmetry. Our main
result is that, for sufficiently strong disorder, the Mott-Anderson transition
is characterized by a precisely defined two-fluid behavior, in which only a
fraction of the electrons undergo a "site selective" Mott localization; the
rest become Anderson-localized quasiparticles.Comment: 4+ pages, 4 figures, v2: minor changes, accepted for publication in
Phys. Rev. Let
Distinct magnetic signatures of fractional vortex configurations in multiband superconductors
Vortices carrying fractions of a flux quantum are predicted to exist in
multiband superconductors, where vortex core can split between multiple
band-specific components of the superconducting condensate. Using the
two-component Ginzburg-Landau model, we examine such vortex configurations in a
two-band superconducting slab in parallel magnetic field. The fractional
vortices appear due to the band-selective vortex penetration caused by
different thresholds for vortex entry within each band-condensate, and
stabilize near the edges of the sample. We show that the resulting fractional
vortex configurations leave distinct fingerprints in the static measurements of
the magnetization, as well as in ac dynamic measurements of the magnetic
susceptibility, both of which can be readily used for the detection of these
fascinating vortex states in several existing multiband superconductors.Comment: 5 pages, 4 figure
Optimal vaccine allocation for the control of sexually transmitted infections
The burden of sexually transmitted infections (STIs) poses a challenge due to its
large negative impact on sexual and reproductive health worldwide. Besides simple
prevention measures and available treatment efforts, prophylactic vaccination is a
powerful tool for controlling some viral STIs and their associated diseases. Here, we
investigate how prophylactic vaccines are best distributed to prevent and control STIs.
We consider sex-specific differences in susceptibility to infection, as well as disease
severity outcomes. Different vaccination strategies are compared assuming distinct
budget constraints that mimic a scarce vaccine stockpile. Vaccination strategies are
obtained as solutions to an optimal control problem subject to a two-sex Kermack–
McKendrick-type model, where the control variables are the daily vaccination rates
for females and males. One important aspect of our approach relies on conceptualizing
a limited but specific vaccine stockpile via an isoperimetric constraint. We solve the
optimal control problem via Pontryagin’sMaximum Principle and obtain a numerical
approximation for the solution using a modified version of the forward–backward
sweep method that handles the isoperimetric budget constraint in our formulation. The
results suggest that for a limited vaccine supply (20%–30%vaccination coverage), onesex
vaccination, prioritizing females, appears to be more beneficial than the inclusion
of both sexes into the vaccination program.Whereas, if the vaccine supply is relatively
large (enough to reach at least 40% coverage), vaccinating both sexes, with a slightly
higher rate for females, is optimal and provides an effective and faster approach to
reducing the prevalence of the infection
Quantum Dissipation and Decoherence via Interaction with Low-Dimensional Chaos: a Feynman-Vernon Approach
We study the effects of dissipation and decoherence induced on a harmonic
oscillator by the coupling to a chaotic system with two degrees of freedom.
Using the Feynman-Vernon approach and treating the chaotic system
semiclassically we show that the effects of the low dimensional chaotic
environment are in many ways similar to those produced by thermal baths. The
classical correlation and response functions play important roles in both
classical and quantum formulations. Our results are qualitatively similar to
the high temperature regime of the Caldeira-Leggett model.Comment: 31 pages, 4 figure
A conjugate for the Bargmann representation
In the Bargmann representation of quantum mechanics, physical states are
mapped into entire functions of a complex variable z*, whereas the creation and
annihilation operators and play the role of
multiplication and differentiation with respect to z*, respectively. In this
paper we propose an alternative representation of quantum states, conjugate to
the Bargmann representation, where the roles of and
are reversed, much like the roles of the position and momentum operators in
their respective representations. We derive expressions for the inner product
that maintain the usual notion of distance between states in the Hilbert space.
Applications to simple systems and to the calculation of semiclassical
propagators are presented.Comment: 15 page
Pasteurização do leite-do-amapá in natura para controle do escurecimento enzimático.
O extrato do amapazeiro (Brosimum parinarioides Ducke), conhecido como leite-do-amapá, é utilizado pelas populações amazônicas como fonte alimentar e medicinal. A rápida alteração de cor do látex após extração representa a presença de enzimas como polifenoloxidase (PPO) e peroxidase (POD), escurecendo o produto in natura e desqualificando-o para comercialização. Desse modo, este trabalho objetivou a avaliação da atividade das enzimas PPO e POD em três amostras de leite-do-amapá resfriadas a 8°C, coletadas em amapazeiros em Moju (PA), e onze amostras de leite-do-amapá após o processo de pasteurização em diversos binômios tempo/temperatura e posteriormente resfriadas a 8°C, visando à otimização da conservação do produto in natura. Após resfriamento a 8°C, as amostras de leite-do-amapá in natura apresentaram diferença significativa entre os valores de atividade da enzima POD e, posteriormente observou-se elevação dessa atividade durante os períodos de tempo analisados. Como também se observou atividade da enzima PPO nas mesmas amostras, constata-se que esse tipo de conservação não foi efi ciente para as enzimas POD e PPO para leite-do-amapá. As amostras pasteurizadas de leitedo-amapá, e posteriormente resfriadas, apresentaram atividades das enzimas POD e PPO significativamente diferenciadas da respectiva amostra controle (sem pasteurização), concluindo que a pasteurização nos binômios estudados, aliada ao resfriamento, foi eficaz na diminuição da atividade das enzimas peroxidase e polifenoloxidase, alcançando-se a inativação destas, podendo ser um processo potencial para conservação desse produto
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