The non-self-adjointness of the radial momentum operator in n dimensions

The non self-adjointness of the radial momentum operator has been noted before by several authors, but the various proofs are incorrect. We give a rigorous proof that the $n$-dimensional radial momentum operator is not self- adjoint and has no self-adjoint extensions. The main idea of the proof is to show that this operator is unitarily equivalent to the momentum operator on $L^{2}[(0,\infty),dr]$ which is not self-adjoint and has no self-adjoint extensions.Comment: Some text and a reference adde

Dipolar atomic spin ensembles in a double-well potential

We experimentally study the spin dynamics of mesoscopic ensembles of ultracold magnetic spin-3 atoms located in two separated wells of an optical dipole trap. We use a radio-frequency sweep to selectively flip the spin of the atoms in one of the wells, which produces two separated spin domains of opposite polarization. We observe that these engineered spin domains are metastable with respect to the long-range magnetic dipolar interactions between the two ensembles. The absence of inter-cloud dipolar spin-exchange processes reveals a classical behavior, in contrast to previous results with atoms loaded in an optical lattice. When we merge the two subsystems, we observe spin-exchange dynamics due to contact interactions which enable the first determination of the s-wave scattering length of 52Cr atoms in the S=0 molecular channel a_0=13.5^{+11}_{-10.5}a_B (where a_B is the Bohr radius).Comment: 9 pages, 7 figure

Mirror symmetry breaking as a problem in dynamical critical phenomena

The critical properties of the Frank model of spontaneous chiral synthesis are discussed by applying results from the field theoretic renormalization group (RG). The long time and long wavelength features of this microscopic reaction scheme belong to the same universality class as multi-colored directed percolation processes. Thus, the following RG fixed points (FP) govern the critical dynamics of the Frank model for d<4: one unstable FP that corresponds to complete decoupling between the two enantiomers, a saddle-point that corresponds to symmetric interspecies coupling, and two stable FPs that individually correspond to unidirectional couplings between the two chiral molecules. These latter two FPs are associated with the breakdown of mirror or chiral symmetry. In this simplified model of molecular synthesis, homochirality is a natural consequence of the intrinsic reaction noise in the critical regime, which corresponds to extremely dilute chemical systems.Comment: 9 pages, 3 figure

Module production of the one-arm AFP 3D pixel tracker

The ATLAS Forward Proton (AFP) detector is designed to identify events in which one or two protons emerge intact from the LHC collisions. AFP will consist of a tracking detector, to measure the momentum of the protons, and a time of flight system to reduce the background from multiple proton-proton interactions. Following an extensive qualification period, 3D silicon pixel sensors were selected for the AFP tracker. The sensors were produced at CNM (Barcelona) during 2014. The tracker module assembly and quality control was performed at IFAE during 2015. The assembly of the first AFP arm and the following installation in the LHC tunnel took place in February 2016. This paper reviews the fabrication process of the AFP tracker focusing on the pixel modules.Comment: PIXEL 2016 proceedings; Submitted to JINS

Hydro-economic model for the assessment of water resources allocation and availability impacts on agricultural income.

RESUMO: A sub-bacia hidrográfica do rio Buriti Vermelho (BHBV), localizada nas proximidades de Brasília, caracteriza-se por intensa atividade agrícola desenvolvida sob uma distribuição heterogênea de água ao longo do tempo e do espaço. Neswte contexto, o artigo desenvolve um modelo hidro-econômico para quantificação dos impactos de curto-prazo na renda regional agrícola de mudanças nos regimes de precipitação e de disponibilidade de água. O modelo econômico se baseia no método de Programação Matemática Positiva que possibilita a construção de funções de produção agrícolas específicas por cultura e por produtor rural, mesmo para pequenas áreas com poucas observações. Do lado hidrológico, um modelo de naturalização de vazões acoplado a um modelo de balanço de água no solo é utilizado para a estimativa da vazão do rio e dos canais de irrigação. Os modelos econômico e hidrológico são interligados e calibrados com dados primários coletados in situ. Considerando as características hídricas da região, as quais, em anos típicos, garantem uma oferta de água para irrigação nos reservatórios bem acima da demanda, e que culturas irrigadas tem um peso muito maior na composição da receita líquida da região do que culturas de sequeiro, os resultados preliminares indicam que uma redução de 5% na disponibilidade de água e na precipitação provocaria uma queda de apenas 1,2% na receita líquida da sub-bacia. Este porcentual, contudo, aumentaria para 11% e 32%, quando a disponibilidade de água e precipitação se reduzissem para 50 e 90%, respectivamente. ABSTRACT: The Buriti Vermelho experimental Basin (BHBV) is characterized by agricultural activities, seasonal water flow uncertainty and heterogeneous water allocation among rural farmers. In this context, this paper follows an interdisciplinary modeling approach that involves economics, hydrology and agronomy. The model developed is then used to evaluate the short-run impacts on agricultural income from changes on precipitation and irrigation water supply. The economic regional model follows a Positive Mathematical Programming approach which allows for the calibration of crop and farmer specific production functions. The hydrological model follows a water balance approach and yields water availability estimates on a proper time and spatial resolution. The two models are coupled together and calibrated with primary data collected in situ. Alternative temperature and precipitation regimes are simulated. Considering that the hydrologic characteristics of the region which, in normal years, guarantees a much higher supply of water for irrigation in the reservoirs relatively to demand and the fact that irrigated crops have a much heavier weight on the net revenue of the region than rainfed crops, a 5% decrease in water availability would be accompanied by a decrease of only 1.2% in the regional net revenue. This percentage, however, would increase to 11% and 32% when water availability reduces to 50 and 90% respectively. KEYWORDS: Water resources, agriculture, irrigation

High thermoelectric performance of bornite through control of the Cu(II) content and vacancy concentration

The thermoelectric performance of the p-type semiconductor bornite, Cu5FeS4, is greatly enhanced through chemical substitution. Non-stoichiometric materials in which the Cu:Fe ratio and overall cation-vacancy con-tent were adjusted are reported and a figure of merit, ZT = 0.79, is achieved at temperatures as low as 550 K in Cu4.972Fe0.968S4. All materials were synthesised mechanochemically and characterised by powder X-ray diffrac-tion, DSC and thermal and electrical transport property measurements. Single-phase behaviour is retained in copper deficient phases, Cu5-xFeS4, for vacancy levels up to x = 0.1, while in materials Cu5+yFe1-yS4, in which the Cu:Fe ratio is varied whilst maintaining full occupancy of cation sites, single-phase behaviour persists for y≤0.08. Adjusting the Cu:Fe ratio at a constant cation-vacancy level of 0.06 in Cu4.94+zFe1-zS4, leads to single-phases for z ≤0.04. DSC measurements indicate the temperature of the intermediate- (2a) to high-temperature (a) phase transition shows a more marked dependence on the Cu:Fe ratio than the lower temperature 4a to 2a transition. The thermoelectric power factor increases almost linearly with increasing Cu(II) content. The maximum figures of merit are obtained for materials with Cu(II) contents in the range 0.10 to 0.15 (corresponding to 2.0 – 2.8 % Cu(II)) which simultaneously contain ca .1 % of cation vacancies

Decoherence and the rate of entropy production in chaotic quantum systems

We show that for an open quantum system which is classically chaotic (a quartic double well with harmonic driving coupled to a sea of harmonic oscillators) the rate of entropy production has, as a function of time, two relevant regimes: For short times it is proportional to the diffusion coefficient (fixed by the system--environment coupling strength). For longer times (but before equilibration) there is a regime where the entropy production rate is fixed by the Lyapunov exponent. The nature of the transition time between both regimes is investigated.Comment: Revtex, 4 pages, 3 figures include

Aplicação de fertilizantes via água de irrigação por injetor Venturi.

Lista de símbolos; Aplicacão de fertilizantes via água de irrigaçãopor injetor venturi; Introducão; Fertirrigacão; Métodos de injecão de fertilizantes; Injetor venturi; princípio de funcionamento do injetor venturi; Condicões requeridas para o funcionamento do venturi; Rendimento dos injetores; Instalacão do injetor venturi; Calibracão do injetor venturi; Uniformidade de distribuicão de fertilizantes; Utilizando injetores venturi; Hidráulica do injetor venturi simples; Comportamento do injetor venturi duplo; Recomendações; Consideracões gerais.bitstream/item/36447/1/Doc59.pd

Non-Markovian finite-temperature two-time correlation functions of system operators of a pure-dephasing model

We evaluate the non-Markovian finite-temperature two-time correlation functions (CF's) of system operators of a pure-dephasing spin-boson model in two different ways, one by the direct exact operator technique and the other by the recently derived evolution equations, valid to second order in the system-environment interaction Hamiltonian. This pure-dephasing spin-boson model that is exactly solvable has been extensively studied as a simple decoherence model. However, its exact non-Markovian finite-temperature two-time system operator CF's, to our knowledge, have not been presented in the literature. This may be mainly due to the fact, illustrated in this article, that in contrast to the Markovian case, the time evolution of the reduced density matrix of the system (or the reduced quantum master equation) alone is not sufficient to calculate the two-time system operator CF's of non-Markovian open systems. The two-time CF's obtained using the recently derived evolution equations in the weak system-environment coupling case for this non-Markovian pure-dephasing model happen to be the same as those obtained from the exact evaluation. However, these results significantly differ from the non-Markovian two-time CF's obtained by wrongly directly applying the quantum regression theorem (QRT), a useful procedure to calculate the two-time CF's for weak-coupling Markovian open systems. This demonstrates clearly that the recently derived evolution equations generalize correctly the QRT to non-Markovian finite-temperature cases. It is believed that these evolution equations will have applications in many different branches of physics.Comment: To appear in Phys. Rev.