Confinement and scaling in deep inelastic scattering

We show that parton confinement in the final state generates large $1/Q^2$ corrections to Bjorken scaling, thus leaving less room for the logarithmic corrections. In particular, the $x$-scaling violations at large $x$ are entirely described in terms of power corrections. For treatment of these non-perturbative effects, we derive a new expansion in powers of $1/Q^2$ for the structure function that is free of infra-red singularities and which reduces corrections to the leading term. The leading term represents scattering from an off-mass-shell parton, which keeps the same virtual mass in the final state. It is found that this quasi-free term is a function of a new variable $\bar x$, which coincides with the Bjorken variable $x$ for $Q^2\to\infty$. The two variables are very different, however, at finite $Q^2$. In particular, the variable $\bar x$ depends on the invariant mass of the spectator particles. Analysis of the data at large $x$ shows excellent scaling in the variable $\bar x$, and determines the value of the diquark mass to be close to zero. $\bar x$-scaling allows us to extract the structure function near the elastic threshold. It is found to behave as $F_2\sim (1-x)^{3.7}$. Predictions for the structure functions based on $\bar x$-scaling are made.Comment: Discussion of target mass corrections is added. Accepted for publication in Phys. Rev.

Structure function of a damped harmonic oscillator

Following the Caldeira-Leggett approach to describe dissipative quantum systems the structure function for a harmonic oscillator with Ohmic dissipation is evaluated by an analytic continuation from euclidean to real time. The analytic properties of the Fourier transform of the structure function with respect to the energy transfer (the ``characteristic function'') are studied and utilized. In the one-parameter model of Ohmic dissipation we show explicitly that the broadening of excited states increases with the state number without violating sum rules. Analytic and numerical results suggest that this is a phenomenologically relevant, consistent model to include the coupling of a single (sub-)nuclear particle to unobserved and complex degrees of freedom.Comment: 23 pages, 5 figures, RevTex4, minor changes following referee's comments and by PRC: the definite article in the original title has been droppe

Resonance peak in underdoped cuprates

The magnetic susceptibility measured in neutron scattering experiments in underdoped YBa$_2$Cu$_3$O$_{7-y}$ is interpreted based on the self-consistent solution of the t-J model of a Cu-O plane. The calculations reproduce correctly the frequency and momentum dependencies of the susceptibility and its variation with doping and temperature in the normal and superconducting states. This allows us to interpret the maximum in the frequency dependence -- the resonance peak -- as a manifestation of the excitation branch of localized Cu spins and to relate the frequency of the maximum to the size of the spin gap. The low-frequency shoulder well resolved in the susceptibility of superconducting crystals is connected with a pronounced maximum in the damping of the spin excitations. This maximum is caused by intense quasiparticle peaks in the hole spectral function for momenta near the Fermi surface and by the nesting.Comment: 9 pages, 6 figure

Comportamento de dois genótipos de milho cultivados em sistema de aléias preestabelecido com diferentes leguminosas arbóreas.

O cultivo em aléias tem sido recomendado como alternativa para a substituição da agricultura de corte e queima, no trópico úmido, devido à grande capacidade de produção de matéria orgânica e de reciclagem de nutrientes, mas algumas dúvidas quanto à sustentabilidade e à competição interespecífica são persistentes. O objetivo no trabalho foi avaliar a viabilidade da cultura do milho em um sistema de cultivo em aléias de leguminosas arbóreas. O delineamento experimental utilizado foi em blocos casualisados, com quatro repetições dos tratamentos: aléias de sombreiro (Clitoria fairchildiana), ingá (Inga edulis), guandu (Cajanus cajan) e leucena (Leucaena leucocephala) e uma testemunha sem aléias. Foram avaliadas a remobilização de carbono e nitrogênio, massa de grãos, massa de mil grãos e competição interespecífica entre as cultivares de milho e as leguminosas. A produção de grãos foi maior nas parcelas com C. fairchildiana e L. leucocephala. A produtividade do híbrido de milho foi superior à da variedade em todos os tratamentos. A produtividade e a massa de mil grãos de milho não são negativamente afetadas pela distância da linha da leguminosa arbórea. Esse estudo conclui que o sistema de aléias com leguminosas arbóreas é uma alternativa importante ao manejo sustentável dos agroecossistemas no tropico úmido. Além disso, nessa região a produtividade em grãos na cultura do milho é favorecida no sistema de aléias preeestabelecidas com as leguminosas arbóreas sombreiro, ingá e leucena e pela utilização de genótipos eficientes no aproveitamento do nitrogênio, cujo sincronismo entre a liberação e a absorção do N aplicado por meio das leguminosas deve ser aprimorado

The Role of Power-Law Correlated Disorder in the Anderson Metal-Insulator Transition

We study the influence of scale-free correlated disorder on the metal-insulator transition in the Anderson model of localization. We use standard transfer matrix calculations and perform finite-size scaling of the largest inverse Lyapunov exponent to obtain the localization length for respective 3D tight-binding systems. The density of states is obtained from the full spectrum of eigenenergies of the Anderson Hamiltonian. We discuss the phase diagram of the metal-insulator transition and the influence of the correlated disorder on the critical exponents.Comment: 6 pages, 3 figure

Quantum walks: a comprehensive review

Quantum walks, the quantum mechanical counterpart of classical random walks, is an advanced tool for building quantum algorithms that has been recently shown to constitute a universal model of quantum computation. Quantum walks is now a solid field of research of quantum computation full of exciting open problems for physicists, computer scientists, mathematicians and engineers. In this paper we review theoretical advances on the foundations of both discrete- and continuous-time quantum walks, together with the role that randomness plays in quantum walks, the connections between the mathematical models of coined discrete quantum walks and continuous quantum walks, the quantumness of quantum walks, a summary of papers published on discrete quantum walks and entanglement as well as a succinct review of experimental proposals and realizations of discrete-time quantum walks. Furthermore, we have reviewed several algorithms based on both discrete- and continuous-time quantum walks as well as a most important result: the computational universality of both continuous- and discrete- time quantum walks.Comment: Paper accepted for publication in Quantum Information Processing Journa

Strategies for Controlled Placement of Nanoscale Building Blocks

The capability of placing individual nanoscale building blocks on exact substrate locations in a controlled manner is one of the key requirements to realize future electronic, optical, and magnetic devices and sensors that are composed of such blocks. This article reviews some important advances in the strategies for controlled placement of nanoscale building blocks. In particular, we will overview template assisted placement that utilizes physical, molecular, or electrostatic templates, DNA-programmed assembly, placement using dielectrophoresis, approaches for non-close-packed assembly of spherical particles, and recent development of focused placement schemes including electrostatic funneling, focused placement via molecular gradient patterns, electrodynamic focusing of charged aerosols, and others

Galaxy Clusters Associated with Short GRBs. II. Predictions for the Rate of Short GRBs in Field and Cluster Early-Type Galaxies

We determine the relative rates of short GRBs in cluster and field early-type galaxies as a function of the age probability distribution of their progenitors, P(\tau) \propto \tau^n. This analysis takes advantage of the difference in the growth of stellar mass in clusters and in the field, which arises from the combined effects of the galaxy stellar mass function, the early-type fraction, and the dependence of star formation history on mass and environment. This approach complements the use of the early- to late-type host galaxy ratio, with the added benefit that the star formation histories of early-type galaxies are simpler than those of late-type galaxies, and any systematic differences between progenitors in early- and late-type galaxies are removed. We find that the ratio varies from R(cluster)/R(field) ~ 0.5 for n = -2 to ~ 3 for n = 2. Current observations indicate a ratio of about 2, corresponding to n ~ 0 - 1. This is similar to the value inferred from the ratio of short GRBs in early- and late-type hosts, but it differs from the value of n ~ -1 for NS binaries in the Milky Way. We stress that this general approach can be easily modified with improved knowledge of the effects of environment and mass on the build-up of stellar mass, as well as the effect of globular clusters on the short GRB rate. It can also be used to assess the age distribution of Type Ia supernova progenitors.Comment: ApJ accepted versio

Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model

We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h095%=3.47×10-25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering. © 2019 American Physical Society