Transmission resonance for a Dirac particle in a one-dimensional Hulthén potential

We have solved exactly the two-component Dirac equation in the presence of a spatially one-dimensional Hulthén potential, and presented the Dirac spinors of scattering states in terms of hypergeometric functions. We have derived the reflection and transmission coefficients using the matching condition on the wavefunctions, and investigated the condition for the existence of transmission resonance. Furthermore, we have demonstrated how the transmission resonance depends on the shape of the potential.      

On kinetic Alfvén waves in a dusty plasma

The dispersion and damping of a dust-modified kinetic Alfvén wave, and a lower frequency dust kinetic Alfvén wave, is investigated in a dusty plasma comprising electrons, ions, and negative dust. It is found that, when dust dynamics is neglected, the presence of cold dust modifies the usual kinetic Alfvén wave dispersion and damping owing to the inequality of the electron and ion densities. The dispersion relation of the dust kinetic Alfvén wave, with frequency below the dust cyclotron frequency, depends on the density and temperature parameters of all three species, and the wave damping is due to both electrons and ions.     

Shadow of a noncommutative geometry inspired Ayón Beato García black hole

We introduce the noncommutative geometry inspired Ayón Beato García black hole metric and study various properties of this metric by which we try to probe the allowed values of the noncommutative parameter \(\vartheta \) under certain conditions. We then construct the shadow (apparent shape) cast by this black hole. We derive the corresponding photon orbits and explore the effects of noncommutative spacetime on them. We then study the effects of noncommutative parameter \(\vartheta \), smeared mass m(r), smeared charge q(r) on the silhouette of the shadow analytically and present the results graphically. We then discuss the deformation which arises in the shape of the shadow under various conditions. Finally, we introduce a plasma background and observe how the shadow behaves in this scenario.     

Approximate path integral solution for a Dirac particle in a deformed Hulthén potential

The problem of a Dirac particle moving in a deformed Hulthén potential is solved in the framework of the path integral formalism. With the help of the Biedenharn transformation, the construction of a closed form for the Green’s function of the second-order Dirac equation is done by using a proper approximation to the centrifugal term and the Green’s function of the linear Dirac equation is calculated. The energy spectrum for the bound states is obtained from the poles of the Green’s function. A Dirac particle in the standard Hulthén potential (q = 1) and a Dirac hydrogen-like ion (q = 1 and a → ∞) are considered as particular cases.     

Electron Acceleration by a Finite-Amplitude Solitary Kinetic Alfvén Wave

The electron acceleration by a finite-amplitude solitary kinetic Alfvén wave (SKAW) in the low-β magnetized plasma is presented. It is found that the electron can be efficiently accelerated in both the parallel and the transverse directions of ambient magnetic field by a finite-amplitude SKAW up to several tenfold Alvén velocity within the time 0.08μs. These results are greatly different from the case of the electron accelerated by a small-amplitude SKAW.     

叶绿素a齐聚物的n值判定及其光谱特证

光合作用是绿色植物利用太阳能将二氧化碳和水有效地转化为有机物质的过程。大体上可以把它分成原初过程、电子传递、光合磷酸化和碳同化四个阶段。其中,光能吸收、传递和转化的过程,称为原初过程,它是光合作用研究的关键的第一步。一般认为原初反应是在光合单位(PSU)里进行的[1,2],其中叶绿素起着十分重要的作用[2,3,4]。     

Torsional Alfvén and slow magnetoacoustic waves generated by a plasma in a magnetic field

An intense electron-antineutrino source with a hard spectrum (\(E_{{{\tilde v}_e}}^{\max }\) = 13 MeV and \(\left\langle {{E_{{{\tilde v}_e}}}} \right\rangle \) = 6.5MeV) can be created on the basis of the short-lived isotope ⁸Li (β^?-decay, T_1/2 = 0.84 s) formed via the (n, γ) activation of ⁷Li. In contrast to a reactor antineutrino spectrum whose uncertainty is large, particularly in the high-energy region \({E_{{{\tilde v}_e}}}\) > 6 MeV, which is experimentally relevant, the lithium \({\tilde v_e}\) spectrum is accurately determined. The proposed accelerator-driven experimental scheme with a neutron-producing target and a lithium converter as an intense \({\tilde v_e}\) source is an alternative to a nuclear reactor. The required amount of high-purity ⁷Li will be reduced in many times by using the suggested heavy-water LiOD solutions. A possible experiment involving the lithium source on search for sterile neutrinos in the mass region Δm² ≥ 0.2 eV² with a very high sensitivity to mixing-angle values down to sin²(2Θ) ≈ (7–10) × 10^–4 at the 95% C.L. has been considered.     

Electronic transport through a C60– n X n (X=N and B) molecular bridge

By applying the non-equilibrium Green's function (NEGF) technique, the Landauer–Buttiker theory and the Fisher–Lee formula, we have investigated the transport behavior of a C_{60– n} X _n (X=N, B) molecule coupled to two semi-infinite SWCNT electrodes. In this study, the coupling through the carbon, boron and nitrogen atoms to the electrodes will be considered. We study the effects of different contact geometries, the electron–phonon interaction and the number of doped atoms on the current value and negative differential resistance (NDR) behavior of C_{60– n} X _n . Our results indicate that the transmission coefficient and the NDR behavior of C_{60– n} X _n vary on changing n and X. Moreover, NDR behavior is observed in C_{60– n} X _n with different contacts and in C₆₀ with C₅ and C₆ contacts. C_{60– n} X _n molecules are suggested for the operation of devices with a nanoscale current.     

Laboratory observation of a nonlinear interaction between shear Alfvén waves

An experimental investigation of nonlinear interactions between shear Alfvén waves in a laboratory plasma is presented. Two Alfvén waves, generated by a resonant cavity, are observed to beat together, driving a pseudomode at the beat frequency. The pseudomode then scatters the Alfvén waves, generating a series of sidebands. The observed interaction is very strong, with the normalized amplitude of the driven pseudomode comparable to the normalized magnetic field amplitude (deltaB/B) of the interacting Alfvén waves.     

Production of Alfvén waves by a rapidly expanding dense plasma

The expansion of a dense (initially, n(lpp)/n(0)>1) laser-produced plasma into an ambient magnetized plasma ( n(0) = 2 x 10(12) cm(-3)) capable of supporting Alfvén waves has been studied. The interaction results in the production of shear Alfvén waves as well as large density perturbations (Delta n/n(0) approximately 0.3) associated with the moving dense plasma. The waves propagate away from the target and are observed to become plasma-column resonances. Spatial patterns of the wave magnetic fields are measured and are used to estimate the coupling efficiency of the laser energy and the kinetic energy of the dense plasma into wave energy.     

Absence of continuous symmetry breaking in a one-dimensional n−2 model

For a one-dimensional array ofS ^N–1 spins (N 2) with isotropic pair interactions (and more general systems) with J(j–i) obeying sup_n[n^–1 ₁ ⁿ j ²|J(j)|]<, we prove that every equilibrium state is invariant under the natural action ofSO(N). In particular, there is no long-range order of the conventional type. Included is the caseJ(n)=n ^–2.Research partially supported by U.S.N.S.F. Grant No. MCS-78-01885.S. Fairchild Scholar at Caltech. On leave from Departments of Mathematics and Physics, Princeton University, Princeton, New Jersey 08544.     

An exact nonlinear Alfvén wave solution in a toroidal magnetic field

The propagation of Alfvén waves along a non-uniform toroidal magnetic field in a highly conducting incompressible fluid rotating uniformly is studied. It is shown that there is an exact Alfvén wave solution with large but restricted form.     

Parity-Violating Asymmetry in γ d → n p with a Pionless Effective Theory

Nuclear parity violation is studied with polarized neutrons in the photodisintegration of the deuteron at low energies. A pionless effective field theory with di-baryon fields is used for the investigation. Hadronic weak interactions are treated by parity-violating di-baryon–nucleon–nucleon vertices, which have undetermined coupling constants. A parity-violating asymmetry in the process is calculated for the incident photon energy up to 30 MeV. If experimental data for the parity-violating asymmetry become available in the future, we will be able to determine the unknown coupling constants in the parity-violating vertices.     

Ion pickup by the intrinsic low-frequency Alfvén waves with a spectrum

Ion pickup by a monochromatic low-frequency Alfvén wave, which propagates along the background magnetic field, has recently been investigated in a low beta plasma (Lu and Li 2007 Phys. Plasmas 14 042303). In this paper, the monochromatic Alfvén wave is generalized to a spectrum of Alfvén waves with random phase. It finds that the process of ion pickup can be divided into two stages. First, ions are picked up in the transverse direction, and then phase difference (randomization) between ions due to their different parallel thermal motions leads to heating of the ions. The heating is dominant in the direction perpendicular to the background magnetic field. The temperatures of the ions at the asymptotic stage do not depend on individual waves in the spectrum, but are determined by the total amplitude of the waves. The effect of the initial ion bulk flow in the parallel direction on the heating is also considered in this paper.     

Slow dynamics in a turbulent von Kármán swirling flow

An experimental study of a turbulent von Kármán flow in a cylinder is presented. The mean flow is stationary up to a Reynolds number Re=10(4) where a bifurcation takes place. The new regime breaks some symmetries of the problem and becomes time dependent because of equatorial vortices moving with a precession movement. In the exact counterrotating case, a bistable regime appears and spontaneous reversals of the azimuthal velocity are registered. A three-well potential model with additive noise reproduces this dynamic. A regime of periodic response is observed when a very weak forcing is applied.     

Multitude of core-localized shear Alfvén waves in a high-temperature fusion plasma

Evidence is presented for a multitude of discrete frequency Alfvén waves in the core of magnetically confined high-temperature fusion plasmas. Multiple diagnostic instruments confirm wave excitation over a wide spatial range from the device size at the longest wavelengths down to the thermal ion Larmor radius. At the shortest scales, the poloidal wavelengths are comparable to the scale length of electrostatic drift wave turbulence. Theoretical analysis confirms a dominant interaction of the modes with particles in the thermal ion distribution traveling well below the Alfvén velocity.     

(n,2n),(n,3n)反应激发函数的系统学研究

本文用包括平衡前发射在内的蒸发模型理论研究了(n,2n),(n,3n)反应的激发函数系统学.在对实验数据分析、拟合的基础上,得到一组较好的经验参数.利用这组参数计算得到的截面和实验结果符合较好.