Bloch inductance in small-capacitance Josephson junctions

We show that the electrical impedance of a small-capacitance Josephson junction also includes, in addition to the capacitive term -i/(omega)CB, an inductive term i(omega)LB. Similar to the known Bloch capacitance CB(q), the Bloch inductance LB(q) also depends periodically on the quasicharge, q, and its maximum value achieved at q=e(mod 2e) always exceeds the value of the Josephson inductance of this junction LJ(phi) at fixed phi=0. The effect of the Bloch inductance on the dynamics of a single junction and a one-dimensional array is described.     

Paul trap simulator experiment to model intense-beam propagation in alternating-gradient transport systems

The results presented here demonstrate that the Paul trap simulator experiment (PTSX) simulates the propagation of intense charged particle beams over distances of many kilometers through magnetic alternating-gradient (AG) transport systems by making use of the similarity between the transverse dynamics of particles in the two systems. Plasmas have been trapped that correspond to normalized intensity parameters s=omega(2)(p)(0)/2omega(2)(q)相似文献   

Dynamic response of one-dimensional interacting fermions

We evaluate the dynamic structure factor S(q, omega) of interacting one-dimensional spinless fermions with a nonlinear dispersion relation. The combined effect of the nonlinear dispersion and of the interactions leads to new universal features of S(q, omega). The sharp peak S(q, omega) approximately q(delta(omega -uq), characteristic for the Tomonaga-Luttinger model, broadens up; for a fixed becomes finite at arbitrarily large . The main spectral weight, however, is confined to a narrow frequency interval of the width deltaomega approximately q(2)/m. At the boundaries of this interval the structure factor exhibits power-law singularities with exponents depending on the interaction strength and on the wave number q.     

Recursion method for the density of states and spectral dimension of percolation networks

We use the recursion method to calculate the vibrational density of states of site percolation clusters slightly above the percolation threshold. It is found that is proportional to at long wavelengths. At shorter length scales, is proportional to , with the fraction dimension . The cross-over from phonon to fraction regime is characterized by a rapid rise in in agreement with effective medium calculations.     

Dynamic structure factor of the Calogero-Sutherland model

We evaluate the dynamic structure factor S(q, omega) of a one-dimensional quantum Hamiltonian with the inverse-square interaction (Calogero-Sutherland model). For a fixed small q, the structure factor differs from zero in a finite interval of frequencies of the width deltaomega proportional to q2/m. At the borders of this interval S(q, omega) exhibits power-law singularities with exponents depending on the interaction strength. The singularities are similar in origin to the well-known Fermi-edge singularity in the x-ray absorption spectra of metals.     

Dynamics of quantum noise in a tunnel junction under ac excitation

We report the first measurement of the dynamical response of shot noise (measured at frequency omega) of a tunnel junction to an ac excitation at frequency omega0. The experiment is performed in the quantum regime, variant Planck's over 2piomega approximately variant Planck's over 2piomega0>kBT at very low temperature T=35 mK and high frequency omega0/2pi=6.2 GHz. We observe that the noise responds in phase with the excitation, but not adiabatically. The results are in very good agreement with a prediction based on a new current-current correlator.     

Peptide internal motions on nanosecond time scale derived from direct fitting of (13)C and (15)N NMR spectral density functions

NMR relaxation-derived spectral densities provide information on molecular and internal motions occurring on the picosecond to nanosecond time scales. Using (13)C and (15)N NMR relaxation parameters [T(1), T(2), and NOE] acquired at four Larmor frequencies (for (13)C: 62.5, 125, 150, and 200 MHz), spectral densities J(0), J(omega(C)), J(omega(H)), J(omega(H) + omega(C)), J(omega(H) - omega(C)), J(omega(N)), J(omega(H) + omega(N)), and J(omega(H) - omega(N)) were derived as a function of frequency for (15)NH, (13)C(alpha)H, and (13)C(beta)H(3) groups of an alanine residue in an alpha-helix-forming peptide. This extensive relaxation data set has allowed derivation of highly defined (13)C and (15)N spectral density maps. Using Monte Carlo minimization, these maps were fit to a spectral density function of three Lorentzian terms having six motional parameters: tau(0), tau(1), tau(2), c(0), c(1), and c(2), where tau(0), tau(1) and tau(2) are correlation times for overall tumbling and for slower and faster internal motions, and c(0), c(1), and c(2) are their weighting coefficients. Analysis of the high-frequency portion of these maps was particularly informative, especially when deriving motional parameters of the side-chain methyl group for which the order parameter is very small and overall tumbling motions do not dominate the spectral density function. Overall correlation times, tau(0), are found to be in nanosecond range, consistent with values determined using the Lipari-Szabo model-free approach. Internal motional correlation times range from picoseconds for methyl group rotation to nanoseconds for backbone N-H, C(alpha)-H, and C(alpha)-C(beta) bond motions. General application of this approach will allow greater insight into the internal motions in peptides and proteins.     

Impact of four-quark shape functions on inclusive B decay spectra

It has recently been pointed out that a new class of subleading shape functions involving B-meson matrix elements of non-local four-quark operators contributes at order to decay distributions in the endpoint region. The corresponding functions and are estimated using the vacuum-insertion approximation. A numerical analysis of various decay spectra suggests that these power corrections are very small, below present theoretical uncertainties due to other subleading shape-function contributions. Received: 29 June 2005, Published online: 13 September 2005     

Dynamical structure factor of the homogeneous electron liquid: its accurate shape and the interpretation of experiments on aluminum

Based on a highly self-consistent theory maintaining the exact functional relations between the self-energy and the vertex part, we evaluate the dynamical structure factor S(q,omega) of the electron liquid. We find striking deviations from S(q,omega) in the random-phase approximation (RPA) for /q/>p(F); besides a broad peak in the one-pair excitation region as seen in the RPA, a clear shoulder appears along a steepened slope at low omega due to electron-hole multiple scattering, and a flattened structure follows due to inseparable interference between one-pair and multipair excitations. Our result agrees with experiments on Al on the whole. The remaining discrepancy is ascribed to the band-structure-induced effect.     

Global gyrokinetic stability of pressure-gradient-driven electromagnetic modes in tokamaks with regions of low shear

Tokamaks with large pressure gradients (alpha(max)) formed in regions of weak magnetic shear are shown to be susceptible to novel, low-n, global, kinetic, electromagnetic modes with a toroidal mode number n in the range 21 on the magnetic axis and alpha(max) near q(min), new, global kinetic infernal modes with a strong mode rotation omega(r) and a finite growth rate gamma<|omega(r)| are found. For equilibria with reverse shear where q(min) is off axis and alpha(max) near q(min), the existence of an unstable low-n global branch of Alfve n ion temperature gradient modes is revealed with an oscillatory gamma as a function of n. The addition of trapped electron dynamics is shown to be further destabilizing.     

High-energy magnon dispersion and multimagnon continuum in the two-dimensional Heisenberg antiferromagnet

We use quantum Monte Carlo simulations and numerical analytic continuation to study high-energy spin excitations in the two-dimensional S = 1/2 Heisenberg antiferromagnet at low temperature. We present results for both the transverse (x) and longitudinal (z) dynamic spin structure factors Sx,z(q,omega) at q = (pi,0) and (pi/2, pi/2). Linear spin-wave theory predicts no dispersion on the line connecting these momenta. Our calculations show that in fact the magnon energy at (pi,0) is 10% lower than at (pi/2, pi/2). We also discuss the transverse and longitudinal multimagnon continua and their relevance to neutron scattering experiments.     

Artifacts in T1 rho-weighted imaging: compensation for B(1) and B(0) field imperfections

The origin of spin locking image artifacts in the presence of B(0) and B(1) magnetic field imperfections is shown theoretically using the Bloch equations and experimentally at low (omega(1) < Delta omega(0)), intermediate (omega(1) approximately Delta omega(0)) and high (omega(1) > Delta omega(0)) spin locking field strengths. At low spin locking fields, the magnetization is shown to oscillate about an effective field in the rotating frame causing signature banding artifacts in the image. At high spin lock fields, the effect of the resonance offset Deltao mega(0) is quenched, but imperfections in the flip angle cause oscillations about the omega(1) field. A new pulse sequence is presented that consists of an integrated spin echo and spin lock experiment followed by magnetization storage along the -z-axis. It is shown that this sequence almost entirely eliminates banding artifacts from both types of field inhomogeneities at all spin locking field strengths. The sequence was used to obtain artifact free images of agarose in inhomogeneous B(0) and B(1) fields, off-resonance spins in fat and in vivo human brain images at 3 T. The new pulse sequence can be used to probe very low frequency (0-400 Hz) dynamic and static interactions in tissues without contaminating B(0) and B(1) field artifacts.     

Exact dynamical structure factor of the degenerate haldane-shastry model

The dynamical structure factor S(q,omega) of the K-component ( K = 2, 3, 4) spin chain with a 1/r(2) interaction is derived exactly at zero temperature for the arbitrary size of the system. The result is interpreted in terms of a free quasiparticle picture which is a generalization of the spinon picture in the SU(2) case. The excited states consist of K quasiparticles each of which is characterized by a set of K-1 quantum numbers. Divergent singularities of S(q,omega) at the spectral edges are derived analytically. The analytic result is checked numerically for finite systems.     

Novel dynamic ccaling regime in hole-doped La2CuO4

Only 3% hole doping by Li is sufficient to suppress the long-range three-dimensional (3D) antiferromagnetic order in La2CuO4. The spin dynamics of such a 2D spin liquid state at T相似文献   

Chirality-induced dynamic kohn anomalies in graphene

We develop a theory for the renormalization of the phonon energy dispersion in graphene due to the combined effects of both Coulomb and electron-phonon (e-ph) interactions. We obtain the renormalized phonon energy spectrum by an exact analytic derivation of the phonon self-energy, finding three distinct Kohn anomalies (KAs) at the phonon wave vector q=omega/v, 2k_{F}+/-omega/v for LO phonons and one at q=omega/v for TO phonons. The presence of these new KAs in graphene, in contrast to the usual KA q=2k_{F} in ordinary metals, originates from the dynamical screening of e-ph interaction (with a concomitant breakdown of the Born-Oppenheimer approximation) and the peculiar chirality of the graphene e-ph coupling.     

Dynamical response of the sinusoidally perturbed electrodissolution/passivation of iron in sulfuric acid solutions: Entrainment,spike generation,and quasiperiodicity

The iron/sulfuric acid (Fe/2 M H(2)SO(4)) system exhibits periodic current oscillations of relaxation type within the potential transition region formed between the active and passive states of the iron electrode when it is polarized in the 2 M sulfuric acid solution. In the present work the dynamical response of the Fe/2 M H(2)SO(4) electrochemical oscillator is investigated when the applied potential at the iron electrode is sinusoidally perturbed. The behavior of the periodically perturbed Fe/2 M H(2)SO(4) oscillator differs significantly from the response of other forced oscillators, as the potential amplitude E(p) and the frequency ratio omega(p)/omega(0) vary. The omega(p) and omega(0) are the angular frequencies of the perturbed applied potential and the unperturbed oscillator, respectively. A special feature of its response is the appearance of a number of spikes, generated within the passive section of a periodic oscillatory cycle for omega(p)/omega(0)<2.9, for periods of the autonomous oscillator T(0) greater, similar 3 s. The number of the generated spikes depends on the amplitude and frequency of the perturbed applied potential as well as on the period of the autonomous oscillator. Spikes are not generated for omega(p)/omega(0)=1 and the system is harmonically entrained by the forcing frequency. However, when the system is subharmonically entrained for omega(p)/omega(0) close to 2, spike generation does occur. By increasing the perturbation frequency for omega(p)/omega(0) greater, similar 2.9 and T(0) greater, similar 3 s, or by decreasing the autonomous period for T(0)<3 s and all the omega(p)/omega(0)<2.9 ratios, the spike generation pattern, is replaced by a quasiperiodic pattern. The dynamical response of the perturbed Fe/2 M H(2)SO(4) electrochemical oscillator is characterized by using time-delay reconstructions of the attractors, Poincare maps, and Fourier power spectra.     

Dirichlet Forms and Dirichlet Operators for Gibbs Measures of Quantum Unbounded Spin Systems: Essential Self-Adjointness and Log-Sobolev Inequality

For each [0, 1] we consider the Dirichlet form and the associated Dirichlet operator for the Gibbs measure of quantum unbounded spin systems interacting via superstable and regular potential. The Gibbs measure is related to the Gibbs state of the system via a (functional) Euclidean integral procedure. The configuration space for the spin systems is given by We formulate Dirichlet forms in the framework of rigged Hilbert spaces which are related to the space . Under appropriate conditions on the potential, we show that the Dirichlet operator is essentially self-adjoint on the domain of smooth cylinder functions. We give sufficient conditions on the potential so that the corresponding Gibbs measure is uniformly log-concave (ULC). This property gives the spectral gap of the Dirichlet operator at the lower end of the spectrum. Furthermore, we prove that under the conditions of (ULC), the unique Gibbs measure satisfies the log-Sobolev inequality (LS). We use an approximate argument used in the study of the same subjects for loop spaces, which in turn is a modification of the method originally developed by S. Albeverio, Yu. G. Kondratiev, and M. Röckner.     

Enhanced sensitivity to the time variation of the fine-structure constant and m{p}/m{e} in diatomic molecules

Sensitivity to temporal variation of the fundamental constants may be strongly enhanced in transitions between narrow close levels of different nature. This enhancement may be realized in a large number of molecules due to cancellation between the ground state fine-structure omega{f} and vibrational interval omega{v} [omega=omega{f}-nomega{v} approximately 0, delta omega/omega=K(2delta alpha/alpha+0.5 delta mu/mu), K>1, mu=m{p}/m{e}]. The intervals between the levels are conveniently located in microwave frequency range and the level widths are very small. Required accuracy of the shift measurements is about 0.01-1 Hz. As examples, we consider molecules Cl(+)(2), CuS, IrC, SiBr, and HfF(+).     

Scaling characteristics of ac conductivity and dielectric function in fractal regime of the metal-insulator transition

An analysis of the ac conductivity _ac(), and the ac dielectric constant, (), of the metal-insulator percolation systems is presented in the critical regime near the transition threshold. It is argued that the polarization and relaxation of the finite fractal metallic clusters play dominant roles in controlling the dynamic response of the system on both sides of the threshold. The relaxation time constant of a fractal cluster is shown to scale with its size as withd _t = 4 – 2d +d _c + /, whered is tge Euclidean dimension, andd _c , , and are the scaling indices for the charging, the dc conductivity, and the correlation length respectively. The average time dependent response of the system is shown to scale with a new time scale , where is the correlation length and ₀ is a microscopic time constant. It is shown that at frequencies and with /d_t 1, in close agreement with experiments. The effects of the anomalous transport along the infinite cluster and the medium polarizability are also discussed.     

Algorithm for linear response functions at finite temperatures: application to ESR spectrum of s=1/2 antiferromagnet Cu benzoate

We introduce an efficient and numerically stable method for calculating linear response functions chi(q,omega) of quantum systems at finite temperatures. The method is a combination of numerical solution of the time-dependent Schr?dinger equation, random vector representation of trace, and Chebyshev polynomial expansion of Boltzmann operator. This method should be very useful for a wide range of strongly correlated quantum systems at finite temperatures. We present an application to the ESR spectrum of s=1 / 2 antiferromagnet Cu benzoate.