Charge densities and charge noise in mesoscopic conductors

We introduce a hierarchy of density of states to characterize the charge distribution in a mesoscopic conductor. At the bottom of this hierarchy are the partial density of states which represent the contribution to the local density of states if both the incident and the out-going scattering channel is prescribed. The partial density of states play a prominent role in measurements with a scanning tunneling microscope on multiprobe conductors in the presence of current flow. The partial density of states determine the degree of dephasing generated by a weakly coupled voltage probe. In addition the partial density of states determine the frequency-dependent response of mesoscopic conductors in the presence of slowly oscillating voltages applied to the contacts of the sample. The partial density of states permit the formulation of a Friedel sum rule which can be applied locally. We introduce the off-diagonal elements of the partial density of states matrix to describe charge fluctuation processes. This generalization leads to a local Wigner-Smith life-time matrix.     

Upper bounds to the susceptibility and the spin pair correlation function of the Ising ferromagnet

Improved upper bounds are presented to the susceptibility and the spin pair correlation function given in the Bethe approximation, for the Ising ferromagnet under zero external field above the critical temperature of the Bethe approximation.     

Correlation function for topological charge densities within the instanton model in QCD

The QCD sum rule for the correlation of topological charge densities χ(Q ²) and for the longitudinal part of the correlation function for singlet axial currents (the latter is related to the former) is considered within the instanton model. The constant f _η′ of η′-meson coupling to the singlet axial current is determined. Its value appears to be in good agreement with that determined recently from the relation between the proton-spin fraction Σ carried by u, d, and s quarks and the derivative of the QCD topological susceptibility χ′(0). On the basis of the same sum rule, the η-η′ mixing angle θ₈ is found within the model employing two mixing angles. The value of θ₈ coincides with that in effective chiral theory. The correlation function for topological charge densities χ(Q ²) at large Q ² is calculated. It is shown that the Q ² dependence at high Q ² matches well with that at low Q ², the latter being determined by the known values χ′(0) and by the contributions of the π and η mesons.     

Instantons: Dynamical mass generation,chiral Ward identities and the topological charge correlation function

When dynamical mass generation resulting from the breakdown of chiral symmetry is taken into account, instanton dynamics treated within the dilute gas approximation may satisfy the constraints on the quark condensates and the topological charge correlation function derived by Crewther from an analysis of the chiral Ward identities assuming the absence of a physical axial U(1) Goldstone boson. From a consideration of the contribution of the η′ to the topological charge correlation function, a relationship is derived in which m_η′²f_η′² is proportional to the vacuum energy density.     

The two-point correlation function of the one-dimensional matrix model

Following Kostov and Ben-Menahem, we calculate the two-puncture correlation function for the one-dimensional matrix model. We find that it depends on the details of discretization for all momenta p. Its only universal features are its vanishing as p → 0 and the appearance of double poles at |p| = n/√′, N = 1,2,…. We show how to derive these double poles in the conformal gauge treatment of Liouville gravity.     

Nearest-neighbor two-point correlation function of the Z-invariant eight-vertex model

The nearest-neighbor two-point correlation function of the Z-invariant inhomogeneous eight-vertex model in the thermodynamic limit is computed using the free-field representation. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 3, 243–247 (10 August 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

相关测速声呐时空相关函数模型改进研究

相关测速声呐通过对回波的理论时空相关函数和数据时空相关函数进行最小二乘拟合或其它优化算法来解算载体速度,因此理论时空相关函数模型的准确性对速度解算是至关重要的。通过对多次海试数据的处理发现,在某些情形下,相关测速声呐的理论空间相关函数和数据空间相关函数三维俯视图形状不匹配,导致速度估计结果不准确。通过对时空相关函数理论模型进行改进,将理论空间相关函数在水平面上的投影由圆形修改为椭圆,则其与数据空间相关函数拟合得更好,从而使相关测速声呐测速准确度得到了提高,并得出相关函数的三维俯视图呈椭圆形状与部分海底表面不平整性的各向异性有关的结论。     

Pion charge radius from current algebra sum rule and short range correlation model

Starting from the Fubini-Dashen-Gell-Mann sum rule, we relate the slope of the pion electromagnetic form factor at t = 0 to the rotational properties of the photopion production amplitudes. When the pion's charge radius is calculated with a simple short range correlation model for the production amplitudes (diffractive processes being forbidden), the result is $\text{〈r}{}_{\mathrm{\pi }}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 0.8}\text{fm}$.     

Enhanced flavour charge in the integer quark charge model

We reexamine the mechanism by which electroproduction of coloured final states is suppressed in integer quark charge theories. An additional O(α/α_s) correction to the $e^{+}{e}^{?}\to q\overline{q}$ amplitude is shown to increase the square of the unsuppressed flavour charge of quarks by 10% at present energies.     

Jump of the minimal site and a new correlation function in the Bak-Sneppen model

A new type of spatio-temporal correlation function for the process approaching the self-organized criticality is investigated within the Bak-Sneppen model for biological evolution. In terms of the “directional shorter distance” between the two sites with minimum fitness at two successive updates, the correlation function is defined and studied numerically for the nearest- and random-neighbor versions of the model. Qualitatively different behaviors of the jump of the minimal site in the two models are presented, and the behaviors of the correlation functions are shown also different. Received 14 April 2001 and Received in final form 28 June 2001     

The correlation function of the Ising model in the MFA and their sum rule

It is shown that in the correctly performed molecular field approximation the correlation function 〈S(q) S(-q)〉 fulfills the sum rule N^-1Σ_q〈S(q) S(-q)〉 = 1. This can be proved for ferro- and antiferromagnets and the disordered phases of o-hydrogen.     

Vacuum charge and the eta function

The vacuum charge of a second quantized spinor field in a static classical background field on a static spacetime is studied. Wheng ₀₀=1 the vacuum charge is shown to be essentially the eta function of the spinor Hamiltonian ats=0. This is computed for compact and noncompact spaces and a boundary dependence is derived in the latter case.     

Charge radii from lattice relative charge distributions

Electromagnetic charge radii values are extracted from relative charge distribution data for pseudoscalars using lattice QCD techniques. This is done with Wilson fermions and SU(2) color at five values of the hopping parameter.     

Charge transfer in the shell model

the mechanism of charge transfer is incorporated into the shell model in an effort to better describe the lattice dynamics of crystals of the zincblende structure. The long-wavelength aspects of the resulting new model are treated in detail. A preliminary application is made to GaAs.     

Electron correlation and charge transfer in superconducting superlattices

We use x-ray spectroscopy to examine the electronic structure of high-temperature superconducting superlattices [(Ba0.9Nd0.10)CuO(2 + delta)]2/[CaCuO2]2. The O 2p density of states reveals the insulating character of the individual component layers and the metallic character of the superlattices. We report the first direct observation of Zhang-Rice singlets in artificial high-temperature superconducting heteroepitaxial structures. The experimental findings in the superlattices and its component layers offer evidence of charge transport from the so-called charge reservoir layer to the superconducting infinite layer. This suggests a strong link between superconductivity and both electron correlation and charge transfer within the superlattices.     

Charge deficiency,charge transport and comparison of dimensions

We study the relative index of two orthogonal infinite dimensional projections which, in the finite dimensional case, is the difference in their dimensions. We relate the relative index to the Fredholm index of appropriate operators, discuss its basic properties, and obtain various formulas for it. We apply the relative index to counting the change in the number of electrons below the Fermi energy of certain quantum systems and interpret it as the charge deficiency. We study the relation of the charge deficiency with the notion of adiabatic charge transport that arises from the consideration of the adiabatic curvature. It is shown that, under a certain covariance, (homogeneity), condition the two are related. The relative index is related to Bellissard's theory of the Integer Hall effect. For Landau Hamiltonians the relative index is computed explicitly for all Landau levels.Dedicated to Elliott Lieb on the occasion of his 60^th birthdayPart of this work was written while the authors enjoyed the hospitality of the Landau Center at the Hebrew University. The work is supported by BSF, DFG, GIF, NSF, the fund for the Promotion of Research at teh Technion and the Technion VPR-Steigman research fund. One of the authors (RS) should like to acknowledge the hospitality of the Mittag-Leffler Institute     

Semiconductor nanocrystals in carrier-transporting polymers: Charge generation and charge transport

By incorporating semiconductor nanocrystals in carrier-transporting polymers, an interesting class of photoconductive nanocomposites is created. The presence of semiconductor nanocrystals enhances the photoinduced charge generation efficiency and extends the sensitivity range, while the polymer matrix is responsible for charge transport. A wide variety of semiconductors and polymers have been used. In this paper, we review material synthesis and discuss the effects of semiconductor nanocrystals on the charge transport and charge generation properties.