[en] We clarify the contribution of Ragusa and Lazo (2004 Eur. J. Phys. 25 127-31) to the problem of covariance of electromagnetic momentum as given by Poynting's vector and the associated problem of the 4/3 in the electromagnetic mass. In particular, we note that the authors are not conscious of von Laue's theorem which makes their discussion mostly unnecessary. (letters and comments)

[en] We consider a discrete–time dynamical system consisting of three controllable objects. The motions of all objects are given by the corresponding vector nonlinear or linear discrete–time recurrent vector relations, and control system for its has two levels: basic (first or I level) that is dominating and subordinate level (second or II level) and both have different criterions of functioning and united a priori by determined informational and control connections defined in advance. For the dynamical system in question, we propose a mathematical formalization in the form of solving a multistep problem of two-level hierarchical minimax program control over the terminal approach process with incomplete information and give a general scheme for its solving

[en] During attitude determination using a global positioning system (GPS), cycle slips occur due to the loss of lock and noise disturbance. Therefore, the integer ambiguity needs re-computation to isolate the error in carrier phase. This paper presents a fast method for integer ambiguity resolution for land vehicle application. After the cycle slips are detected, the velocity vector is utilized to obtain the rough baseline vector. The obtained baseline vector is substituted into carrier phase observation equations to solve the float ambiguity solution which can be used as a constraint to accelerate the integer ambiguity search procedure at next epochs. The probability of correct integer estimation in the expanded search space is analyzed. Experimental results demonstrate that the proposed method gives a fast approach to obtain new fixed ambiguities while the regular method takes longer time and sometimes results in incorrect solutions

[en] In the present work we study the photonic band structure (PBS) and the polarization state of the Bloch eigenmodes of a two-dimensional magnetophotonic crystal (MPC) with square lattice formed from magneto-optically (MO) active cylinders. The refraction of light at the boundary of the MPC is analyzed. We found that both-the PBS and eigenmodes of the MPC-are most significantly altered by the MO activity in the vicinity of the degeneracies. For this case we demonstrated the possibility of an abrupt change in the propagation direction of light by the application of a magnetic field. For the Bloch wave vectors and frequencies corresponding to non-degenerate branches, the alteration of the PBS is shown to be negligible and eigenmodes almost completely coincide with linearly TE- and/or TM-polarized eigenmodes of the non-magnetic photonic crystal

[en] In this paper we formulate a number of teaching paradoxical problems, dealing with the energy-momentum conservation law in a bound electromagnetic field

No abstract available

[en] Expressions for the parameters of the macroscopic magnetization vector field are obtained based on a model of point magnetic moments. It is shown that the magnetization vector field consists of a vortex and a potential part. The form of the obtained expansion depends on the system of units chosen. The magnetic field of the magnetization vector and the electric field of the polarization vector are compared and shown to be equivalent. In relation to the problems discussed, the methodical aspects of teaching an 'Electricity and Magnetism' section of a physics course are highlighted. (methodological notes)

[en] It has been shown in the past that the classical Laplace-Runge-Lenz vector emerges naturally in the computation of the post-Newtonian Lorentz boost in 2-body electrical or gravitational systems. This procedure is extended here to many-body systems. A new N-body vector observable of the Runge-Lenz type is found which is an integral of motion for non-trivial families of solutions. Conditions for its integrability are discussed with explicit examples. The relation of this vector with the post-Newtonian centre-of-mass is also briefly discussed.

[en] We investigated the influence of external magnetic field in the tube onthe vacuum of massive charged scalar field for the case of arbitraryspace-time dimension. The tube is considered impermeable for scalar field andobeys Dirichlet boundary condition on bounding surface. It was shown that forparticular case of 2+1 dimensional space-time the induced vacuum energy ofscalar field outside the tube can be numerically calculated withoutregularization procedure.

[en] Biomagnetic instruments usually employ sensors with approximately radial normal vectors arranged on a near-spherical surface. The multipole expansion employed in the recently introduced signal space separation method (SSS) reveals limitations in this traditional sensor array design. Specifically, we show that the excessive symmetry of the sensor array impedes separation of multipole components arising from inside and outside of the array. This motivates consideration of novel instrument designs that would sample the field in a more comprehensive way. We evaluated several simulated sensor arrays that employ vector sensors in one or two layers, giving information on multiple field components and the radial dependence of the field. Our results indicate that this kind of sensor array design could significantly improve SSS performance, leading to enhanced shielding against external interference and reduced noise after signal reconstruction. The best two-layer array evaluated here attains a shielding factor of nearly 1000 or 60 dB with about 400 sensors. Due to limited spatial coverage, a traditional reference array geometry does not give the same level of improvement. In addition to improved software shielding, enhanced detection of different multipole components increases the information obtained about the magnetic field, which has fundamental importance.