Coherently controllable non-equilibrium charge accumulation inside a magnetic quantum dot: a non-equilibrium Green’s function approach

We have performed a non-equilibrium quantum transport calculations for a two-terminal mesoscopic system including a magnetic quantum dot. Using the non-equilibrium Green’s function technique, we have obtained electric current and charge distribution in the temperature range from 1 to 10 K as a function of magnetic field. Results indicate that the density of carriers essentially can be controlled by temperature and bias voltage.     

Generalized Sturm expansions of the Coulomb Green’s function and two-photon Gordon formulas

The radial component of the Coulomb Green’s function (CGF) is written in the form of a double series in Laguerre polynomials (Sturm’s functions in the Coulomb problem), which contains two free parameters α and α′. The obtained result is applicable both in the nonrelativistic case and for the CGF of the squared Dirac equation with a Coulomb potential. The CGF is decomposed into the resonance and potential components (the latter is a smooth function of energy) for α = α′. In the momentum representation, the CGF with the free parameters is written in the form of an expansion in four-dimensional spherical functions. The choice of the parameters α and α ′ in accordance with the specific features of the given problem radically simplifies the calculation of the composite matrix elements for electromagnetic transitions. Closed analytic expressions (in terms of hypergeometric functions) are obtained for the amplitudes of bound-bound and bound-free two-photon transitions in the hydrogen atom from an arbitrary initial state ¦nl〉, which generalize the known (one-photon) Gordon formulas. The dynamic polarizability tensor components α_nlm(ω) for an arbitrary n are expressed in terms of the hypergeometric function ₂ F ₁ depending only on l and $\tilde \omega $ and through the polynomial functions $f_{nl} (\tilde \omega )$ of frequency $\tilde \omega = {{\hbar \omega } \mathord{\left/ {\vphantom {{\hbar \omega } {\left| {E_n } \right|}}} \right. \kern-0em} {\left| {E_n } \right|}}$ . The Rydberg (n ? 1) and threshold (?ω ～ ¦ E _n¦) asymptotic forms of polarizabilities are investigated.     

Thermodynamics of a quantum gas and a two-particle Green’S function

It has been shown with the use of the virial theorem and the equation of motion for the single-particle Green’s function that the thermodynamic properties of a single-component quantum gas beyond the perturbation theory are fully determined by the two-particle Green’s function Moscow Power Engineering Institute.     

Shell energy in the heaviest nuclei using the Green’s function oscillator expansion method

The Greens function oscillator expansion method and the generalized Strutinsky smoothing procedure are applied to shell corrections in the heaviest elements. A macroscopic-microscopic method with a finite deformed Woods-Saxon potential is used. The stability condition for the shell correction is discussed in detail and the parameters defining the smoothing procedure are carefully determined. It is demonstrated that the spurious contribution to the total binding energy due to the unphysical particle gas that appears in the standard method can be as large as 1.5 MeV for weakly bound neutron-rich superheavy nuclei, but the effect on energy differences (e.g., alpha-decay values) is fairly small.     

A new method for the analysis of transmission property in carbon nanotubes using Green’s function

A new method for the analysis of electron transmission property in single-walled carbon nanotubes (SWCNTs) using Green’s function is presented in this paper for the first time. Using the proposed method, a new relation for the transmission function through a deformed SWCNT is obtained, which depends on the energy variations and the coupling matrices related to the mechanical deformations applied to the structure of CNT. The obtained new relation is explained by the presented results in the literature.     

The Green’s function in a channel with a sound-absorbing cover in the case of a uniform flow

We study the modal structure of an acoustic field of a point source as function of channel wall admittance in the case of a two-dimensional channel. The characteristic equation for determining the eigen-values corresponding to the boundary problem is studied in the form of this equation??s dependence on the admittance, which varies in the entire complex plane. All modes, without exception, existing in the channel and forming the source field are classified based on the obtained topography of the characteristic equation. The expressions that describe the amplitudes and spatial distribution of the hydrodynamic modes, attenuation rate (for stable modes), or increment (for unstable modes) were obtained as functions of the wall admittance and flow velocity. It is shown that in addition to the hydrodynamic unstable modes existing downstream from the source, hydrodynamic unstable modes exist upstream from the source at any admittance. They appear only when the admittance has an elastic character. It is shown that hydrodynamic modes are induced only in the case when the source is located close to the wall or on the wall. The amplitude of these modes decreases exponentially with distance from the wall.     

Regularized Green’s function and group of reflections in a cavity with triangular cross section

For a certain class of triangles (with angles proportional to π/N, N ≥ 3) we formulate the image method by making use of the group G _N generated by reflections with respect to three lines which form the triangle under consideration. A regularized Green’s function (which is employed in Casimir energy calculations) is obtained by classification of subgroups of G _N and corresponding fixed points in the triangle.     

Green’s function of a 2D Fermi system undergoing a topological phase transition

An explicit expression is obtained for the single-particle Green’s function of a 2D metallic system with attraction between carriers. It is shown that as a result of transverse phase fluctuations, this function is pole-free throughout the entire region of finite temperatures (both above and below the topological phase transition point) corresponding to a nonzero modulus of the complex order field describing the transition from a nonsuperconducting (in this case normal) state to a superconducting state, whose appearance in the 2D case is not accompanied by spontaneous breaking of charge symmetry. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 2, 126–131 (25 January 1999)     

Measurements of electron-phonon coupling factor and interfacial thermal resistance of metallic nano-films using a transient thermoreflectance technique

Using a transient thermoreflectance (TTR) technique,several Au films with different thicknesses on glass and SiC substrates are measured for thermal characterization of metallic nano-films,including the electron-phonon coupling factor G,interfacial thermal resistance R,and thermal conductivity K s of the substrate. The rear heating-front detecting (RF) method is used to ensure the femtosecond temporal resolution. An intense laser beam is focused on the rear surface to heat the film,and another weak laser beam is focused on the very spot of the front surface to detect the change in the electron temperature. By varying the optical path delay between the two beams,a complete electron temperature profile can be scanned. Different from the normally used single-layer model,the double-layer model involving interfacial thermal resistance is studied here. The electron temperature cooling profile can be affected by the electron energy transfer into the substrate or the electron-phonon interactions in the metallic films. For multiple-target optimization,the genetic algorithm (GA) is used to obtain both G and R. The experimental result gives a deep understanding of the mechanism of ultra-fast heat transfer in metals.     

Self-consistent calculations within the Green’s function method including particle-phonon coupling and the single-particle continuum

The Green’s function method in the Quasiparticle Time Blocking Approximation is applied to nuclear excitations in ¹³²Sn and ²⁰⁸Pb. The calculations are performed self-consistently using a Skyrme interaction. The method combines the conventional RPA with an exact single-particle continuum treatment and considers in a consistent way the particle-phonon coupling. We reproduce not only the experimental values of low-and high-lying collective states but we also obtain fair agreement with the data of non-collective low-lying states that are strongly influenced by the particle-phonon coupling.     

Influence of a metallic substrate’s magnetic state on the huge magnetoresistance of a ferromagnet-polymer structure

The association between the threshold value of conductance switching in an external magnetic field and the initial magnetic state of a ferromagnetic plate substrate is shown for a ferromagnet/polymer/nonmagnetic metal system. The threshold magnetic field change is explained by appearance of residual magnetization after being held in an external magnetic field and, correspondingly, by the change in the initial state upon further remagnetization.     

Noise analysis of coaxial Schottky barrier carbon nanotube fets using non equilibrium Green’s function formalism

The effect of noise on the performance of Schottky Barrier Carbon Nanotube Field Effect Transistors (SB-CNTFETs) has been investigated under various bias conditions. In order to calculate the noise power spectral density, the Non-Equilibrium Green’s Function formalism (NEGF) is used to obtain the transmission coefficient and the number of carriers inside the channel. Results are presented in two sections: In the first section the Hooge’s empirical rule is used to investigate the flicker noise properties of SB-CNTFETs with defects in the gate oxide region, while in the second section the thermal and shot noise properties of SB-CNTFETs are studied. Finally, the best bias points in the ON and OFF states have been suggested according to the total noise power spectral density and the device signal to noise ratio.      

Analytical approach to quantum phase transitions of ultracold Bose gases in bipartite optical lattices using the generalized Green’s function method

In order to investigate the quantum phase transitions and the time-of-flight absorption pictures analytically in a systematic way for ultracold Bose gases in bipartite optical lattices, we present a generalized Green’s function method. Utilizing this method, we study the quantum phase transitions of ultracold Bose gases in two types of bipartite optical lattices, i.e., a hexagonal lattice with normal Bose–Hubbard interaction and a d-dimensional hypercubic optical lattice with extended Bose–Hubbard interaction. Furthermore, the time-of-flight absorption pictures of ultracold Bose gases in these two types of lattices are also calculated analytically. In hexagonal lattice, the time-of-flight interference patterns of ultracold Bose gases obtained by our analytical method are in good qualitative agreement with the experimental results of Soltan-Panahi, et al. [Nat. Phys. 7, 434 (2011)]. In square optical lattice, the emergence of peaks at \(\left( { \pm \frac{\pi }{a}, \pm \frac{\pi }{a}} \right)\) in the time-of-flight absorption pictures, which is believed to be a sort of evidence of the existence of a supersolid phase, is clearly seen when the system enters the compressible phase from charge-density-wave phase.     

More on the renormalization of the horizon function of the Gribov–Zwanziger action and the Kugo–Ojima Green function(s)

In this paper we provide strong evidence that there is no ambiguity in the choice of the horizon function underlying the Gribov–Zwanziger action. We show that there is only one correct possibility which is determined by the requirement of multiplicative renormalizability. As a consequence, this means that relations derived from other horizon functions cannot be given a consistent interpretation in terms of a local and renormalizable quantum field theory. In addition, we also discuss that the Kugo–Ojima functions u(p ²) and w(p ²) can only be defined after renormalization of the underlying Green function(s).     

Evaluation of the brain pH using a phosphorus magnetic resonance spectroscopy technique – a comparison of women and men

The aim of this study was to determine the reference value of pH in healthy women and men using the phosphorus magnetic resonance spectroscopy technique. The brains of 65 young volunteers were examined. The intracellular pH was calculated in the group of women and the group of men. In both groups, the average pH was slightly alkaline (respectively 7.10?±?0.08 and 7.08?±?0.12). No statistically significant sex difference in brain pH was found. Thus, in case if this method is used to estimate possible brain pathology in the young population, it is not needed to take the gender factor into consideration.     

Hamilton’s principle and the rolling motion of a symmetric ball

In this paper, we show that the trajectories of a dynamical system with nonholonomic constraints can satisfy Hamilton’s principle. As the simplest illustration, we consider the problem of a homogeneous ball rolling without slipping on a plane. However, Hamilton’s principle is formulated either for a reduced system or for a system defined in an extended phase space. It is shown that the dynamics of a nonholonomic homogeneous ball can be embedded in a higher-dimensional Hamiltonian phase flow. We give two examples of such an embedding: embedding in the phase flow of a free system and embedding in the phase flow of the corresponding vakonomic system.     

Penrose’s circles in the CMB and a test of inflation

We present a calculation of the angular size of the circles in the CMB predicted by Penrose on the basis of his conformal cyclic cosmology. If these circles are detected, the existence of an upper limit on their angular radius would provide a challenge for inflation.     

Pryce’s mass-center operators and the anomalous velocity of a spinning electron

In the present work, we develop a method to derive the anomalous velocity of a spinning electron. From Dirac equation, the relationships among the expectation values of the Pryce’s mass-center operator, the position operator, the spin operator and the canonical momentum operator are investigated. By requiring that the center of mass for a classical spinning electron is related to the expectation value of Pryce’s mass-center operator, one can obtain a classical expression for the position of the electron. With the classical equations of motion, the anomalous velocity of a spinning electron can be easily obtained. It is shown that two factors contribute to the anomalous velocity: one is dependent on the selection of Pryce’s mass-center operators and the other is a type-independent velocity expressed by the rotational velocity and the Lorentz force.