Synthesis of magnetic systems producing field with maximal scalar characteristics

A method of synthesis of the magnetic systems (MSs) consisting of uniformly magnetized blocks is proposed. This method allows to synthesize MSs providing maximum value of any magnetic field scalar characteristic. In particular, it is possible to synthesize the MSs providing the maximum of a field projection on a given vector, a gradient of a field modulus and a gradient of a field energy on a given directing vector, a field magnitude, a magnetic flux through a given surface, a scalar product of a field or a force by a directing function given in some area of space, etc. The synthesized MSs provide maximal efficiency of permanent magnets utilization. The usage of the proposed method of MSs synthesis allows to change a procedure of projecting in principal, namely, to execute it according to the following scheme: (a) to choose the sizes, a form and a number of blocks of a system proceeding from technological (economical) reasons; (b) using the proposed synthesis method, to find an orientation of site magnetization providing maximum possible effect of magnet utilization in a system obtained in (a). Such approach considerably reduces a time of MSs projecting and guarantees maximal possible efficiency of magnets utilization. Besides it provides absolute assurance in “ideality” of a MS design and allows to obtain an exact estimate of the limit parameters of a field in a working area of a projected MS.The method is applicable to a system containing the components from soft magnetic material with linear magnetic properties.     

Vibrations of double-string complex system under moving forces. Closed solutions

In this paper the dynamic response of a double-string system traversed by a constant or a harmonically oscillating moving force is considered. The force is moving with a constant velocity on the top string. The strings are identical, parallel, one upon the other and continuously coupled by a linear Winkler elastic element. The classical solution of the response of a double-string system subjected to a force moving with a constant velocity has a form of an infinite series. The main goal of this paper is to show that in the considered case a part of the solution can be presented in a closed, analytical form instead of an infinite series. The presented method of finding the solution in a closed, analytical form is based on the observation that the solution of the system of partial differential equations in the form of an infinite series is also a solution of an appropriate system of ordinary differential equations.     

Geometric phase induced by a cyclically evolving squeezed vacuum reservoir

We propose a new way to generate an observable geometric phase by means of a completely incoherent phenomenon. We show how to imprint a geometric phase to a system by adiabatically manipulating the environment with which it interacts. As a specific scheme, we analyze a multilevel atom interacting with a broadband squeezed vacuum bosonic bath. As the squeezing parameters are smoothly changed in time along a closed loop, the ground state of the system acquires a geometric phase. We also propose a scheme to measure such a geometric phase by means of a suitable polarization detection.     

Some non-abelian phase spaces in low dimensions

A non-abelian phase space, or a phase space of a Lie algebra, is a generalization of the usual (abelian) phase space of a vector space. It corresponds to a para-Kähler structure in geometry. Its structure can be interpreted in terms of left-symmetric algebras. In particular, a solution of an algebraic equation in a left-symmetric algebra which is an analogue of classical Yang–Baxter equation in a Lie algebra can induce a phase space. In this paper, we find that such phase spaces have a symplectically isomorphic property. We also give all such phase spaces in dimension 4 and some examples in dimension 6. These examples can be a guide for a further development.     

Physical adsorption and surface plasmons

The quantum mechanical formulation of the screening of a point charge by surface plasmons is extended to describe the coupling of a fluctuating atomic dipole with a metallic surface of planar, spherical or cylindrical shape. This allows for the calculation of the nonretarded Van der Waals attraction of an atom by a solid surface in the three different geometries. Applications of the theoretical formulae are made to obtain numerical values of the dispersion energy by a spherical particle, a spherical pore, a thin film, a slot-like prore, a cylindrical fiber or a cylindrical pore.     

Interaction of electromagnetic waves with nonlinear substance layer under conditions of electron paramagnetic resonance in millimeter waves

Trancated equations have been obtained by the Green's functions method for a slowly varying amplitude of a transverse magnetic field component in a paramagnetic layer under conditions of the electron paramagnetic resonance (EPR). A magnetic susceptibiliti of the substence has been found from the Bloch equation for a homogeneously line breadth of the EPR. In a stationary case a solution of a nonlinear boundary-value problem is redused to a solution of two boundary problems for amplitude and phase equations. It is shown that unstable regimes of the electrodynamic system under inves tigation are possible.Electrodynamic characteristics of a nonlinear resonator of the Fabry-Pero type filled with a saturated paramagnetic medium have been analyzed numerically in a non-stationery case.     

Evolution of Classical and Quantum States in the Groupoid Picture of Quantum Mechanics

The evolution of states of the composition of classical and quantum systems in the groupoid formalism for physical theories introduced recently is discussed. It is shown that the notion of a classical system, in the sense of Birkhoff and von Neumann, is equivalent, in the case of systems with a countable number of outputs, to a totally disconnected groupoid with Abelian von Neumann algebra. The impossibility of evolving a separable state of a composite system made up of a classical and a quantum one into an entangled state by means of a unitary evolution is proven in accordance with Raggio’s theorem, which is extended to include a new family of separable states corresponding to the composition of a system with a totally disconnected space of outcomes and a quantum one.     

Weak values of electron spin in a double quantum dot

We propose a protocol for a controlled experiment to measure a weak value of the electron's spin in a solid state device. The weak value is obtained by a two step procedure--weak measurement followed by a strong one (postselection), where the outcome of the first measurement is kept provided a second postselected outcome occurs. The setup consists of a double quantum dot and a weakly coupled quantum point contact to be used as a detector. Anomalously large values of the spin of a two electron system are predicted, as well as negative values of the total spin. We also show how to incorporate the adverse effect of decoherence into this procedure.     

On reconstructing photon statistics by on/off detectors: Toward the multi-partite case

The propagation of pulses of the pump and its second harmonic in a quadratically nonlinear medium whose linear properties are characterized by a negative refractive index at the pump frequency and by a positive refractive index at the harmonic frequency is considered theoretically. In the case of a low intensity of the interacting waves, the pump and second-harmonic pulses propagate in the opposite directions, but sufficiently powerful pulses can form a simulton—a solitary two-frequency wave propagating in a certain direction as a single whole. Solutions to a set of equations are found which describe the steady-state propagation of a solitary wave and of a nonlinear periodic (cnoidal) wave.     

Effects of a magnetic field on a modulated phase

The effects of a magnetic field on a modulated phase are studied. A modulated phase is found to have two critical fields H₁ and H₂. For a large enough magnetic field, H₁ and H₂ can be approximated by a linear law. As a result, the minimum magnetic field needed to destroy a modulated phase is a constant. The minimum magnetic field also greatly depends on the order of a commensurate phase. A very high order commensurate phase and an incommensurate phase cannot survive a magnetic field. The behaviour of a magnetoelastic chain in a magnetic field can be described by a harmless devil's staircase. The inverse temperature is found to play a role similar to that of a special magnetic field. The deeper physics underlying these new phenomena is the breaking of the left-right symmetry of a phase diagram. As a result a controllable path to a modulated phase is found.     

Dynamics of sandwich domain structure in Co-based amorphous ribbons with helical magnetic anisotropy: Part I

The distribution of axes of easy magnetization close to a homogeneous distribution is revealed in each half-thickness of a ribbon after annealing it in a helical magnetic field. The transition from magnetic reversal of a ribbon by the displacement of two domain walls formed near a middle plane of a ribbon to magnetic reversal of a ribbon by displacement of two domain walls formed near to the main surfaces of a ribbon is found out during each half-period of a magnetic reversal.     

Reconstruction of the acoustic impedance profile in a plate using an inverse spectral procedure

An inverse spectral procedure was applied to reconstruct the acoustic impedance profile along the thickness direction of a plate using its thickness resonance frequencies, density and thickness. For a successful reconstruction, the material-property profile must be symmetric about the mid-plane of the plate. Several cases of numerical simulations, including plates with a few layers and with a high number of layers are described. The calculated resonance frequencies were used to reconstruct the acoustic impedance profile, a process that was successful for all cases. We assume that a plate with a high number of layers, each with a different but constant acoustic impedance, simulates a plate with a smoothly varying acoustic impedance profile. It can be concluded that such a plate, which generates small, virtually undetectable, internally reflected waves, can also be reconstructed. In the special case of a plate of unknown thickness and unknown but constant density, the method is still useful, because a relative variation of the material property can be reconstructed using only the resonance frequencies. An experiment using a resonance-mode electromagnetic acoustic transducer (resonance-mode EMAT) is also described. EMAT is a non-contact ultrasonic method that can measure thickness resonance frequencies, making it appropriate for this method. Some examples of applications are measurement of the temperature profile inside a rolled metal sheet, measurement of a clad metal plate, and monitoring of a metal casting.     

Asymmetric universal entangling machine for qubits

We give a definition of a universal entangling machine that entangles a system in an unknown state to a specially prepared ancilla. We describe explicitly such a machine for one qubit; i.e., we show how a qubit in an a priori unknown state can be entangled to a four-level ancilla by means of a unitary transformation. As a result, a fixed state-independent amount of entanglement is generated in exchange for a fixed degradation of qubit state fidelity.     

Cumulants and moments

We introduce a ¹-algebra of terminating sequences. The set of normalized linear functionals on this algebra is then equipped with a quasi-multiplication and thus with a multiplication. A state corresponds to a sequence of moments. With it we associate its sequence of cumulants. The quasi-multiplication relates cumulants and moments in a very easy way. We give necessary and sufficient conditions for a sequence to be a sequence of moments and necessary and sufficient conditions for a sequence to be a sequence of cumulants.     

Instability of traveling waves in an optical waveguide

Instability of traveling IR waves within a waveguide structure is discussed. A practical model of a traveling wave amplifier of a solid state is proposed, utilizing an optical waveguide. The mechanism of instability is interpreted in terms of an interaction between a plasmon wave and a circuit one under a constraining boundary condition. Properties of the traveling amplification and related problems are discussed, with appropriately suggested semiconductor materials and device designs. The features of the amplifier are a simple structure, a low DC biasing power dissipation for room-temperature operation, unidirectionality, and a wide wavelength range from IR or submillimeter order, suited to various applications.     

Development of a self-oscillating ultrasonic micro-motor and its application to a watch

We have developed an ultrasonic micro-motor for use as a micro-actuator in place of an electromagnetic motor. This ultrasonic micro-motor, which can be driven by a single signal and in which the change of the direction of the rotor movement can be made easily by selecting the electrode to apply the driving signal, can easily construct a self-oscillating circuit and simplify the driving circuit. We have also simplified the motor structure, which is easy to miniaturize and mass-produce. We applied a version of this motor with a diameter of 8 mm to a vibration alarm, and one with a diameter of 4.5 mm to a driving source of a calendar mechanism in a watch. This ultrasonic micro-motor is expected to be of use as a new driving source in a broad range of fields.     

Scattering of a plane wave from a periodic random surface: a probabilistic approach

This paper deals with a probabilistic formulation of the wave scattering from a periodic random surface. When a plane wave is incident on a random surface described by a periodic stationary stochastic process, it is shown by a group-theoretic consideration that the scattered wave may have a stochastic Floquet form, i.e. a product of a periodic stationary random function and an exponential phase factor. Such a periodic stationary random function is then written by a harmonic series representation similar to a Fourier series, where Fourier coefficients are mutually correlated stationary processes instead of constants. The mutually correlated stationary processes are represented by Wiener - Hermite functional series with unknown coefficient functions called Wiener kernels. In case of a slightly rough surface and TE wave incidence, low-order Wiener kernels are determined from the boundary condition. Several statistical properties of the scattering are calculated and illustrated in figures.     

Coulomb self-energy and electrostatic potential of a uniformly charged square in two dimensions

The most popular model for a two-dimensional electronic system considers electrons moving in a background of uniform positive charge. Studies of finite systems employing a spherical geometry (electrons on the surface of a sphere) or a disk geometry background are numerous. The same cannot be said for a square geometry, who after all, would be the geometry of choice for quantum Hall states in a Landau gauge. A background represented by a uniformly charged square seems to be perceived as too costly from a computational point of view. By using simple transformations, we show that the Coulomb self-energy and the electrostatic potential of a uniformly charged square can be exactly calculated and poses no difficulty. The current results can be used in systematic studies of properties of finite systems of electrons embedded in a positive background in the form of a uniformly charged square.     

Measuring Light Field of Light Source with High Directional Resolution Using Mirrored Ball and Pinhole Camera

This paper presents a method of measuring a light field of a light source with high directional resolution using a mirrored ball and a pinhole camera. The light field describes a spatial and directional distribution of radiances from the light source. The directional distribution is expanded by a reflection on the mirrored ball, and the radiances are measured by a charge-coupled device (CCD) camera with a pinhole lens. The light source is laterally moved by a robot arm to measure the directionally expanded light field, and each pixel on a CCD can obtain the radiances from the light source through the pinhole lens with high directional resolution. The light field is estimated from the pixel value and the position of each pixel using a ray tracing technique. The light field of a krypton lamp was experimentally measured by the proposed method, and the accuracy of the measurement was evaluated against the irradiances measured by a spectro-radiometer at sample points.