Synchronization induced by periodic inputs in finite NN-unit bistable Langevin models: The augmented moment method

We have studied the synchronization induced by periodic inputs applied to the finite $N$-unit coupled bistable Langevin model which is subjected to cross-correlated additive and multiplicative noises. Effects on the synchronization of the system size ($N$), the coupling strength and the cross-correlation between additive and multiplicative noises have been investigated with the use of the semi-analytical augmented moment method (AMM) which is the second-order moment approximation for local and global variables [H. Hasegawa, Phys. Rev. E {\bf 67} (2003) 041903]. A linear analysis of the stationary solution of AMM equations shows that the stability is improved (degraded) by positive (negative) couplings. Results of the nonlinear bistable Langevin model are compared to those of the linear Langevin model.Comment: 19 pages, 10 figures, the final version with a changed title, accepted in Physica

Zero-field and Larmor spinor precessions in a neutron polarimeter experiment

We present a neutron polarimetric experiment where two kinds of spinor precessions are observed: one is induced by different total energy of neutrons (zero-field precession) and the other is induced by a stationary guide field (Larmor precession). A characteristic of the former is the dependence of the energy-difference, which is in practice tuned by the frequency of the interacting oscillating magnetic field. In contrast the latter completely depends on the strength of the guide field, namely Larmor frequency. Our neutron-polarimetric experiment exhibits individual tuning as well as specific properties of each spinor precession, which assures the use of both spin precessions for multi-entangled spinor manipulation.Comment: 12 pages, 4 figure

Theory on the Temperature Dependence of Giant Magnetoresistance

The temperature dependence of the giant magnetoresistance (GMR) for currents parallel and perpendicular to the multilayer plane, is discussed by taking account of the random exchange potentials, phonon scatterings and spin fluctuations. The effect of spin fluctuations, which plays an important role at finite temperatures, is included by means of the static functional-integral method developed previously by the present author. Our model calculations well explain the observed features of the parallel and perpendicular GMR of Fe/Cr and Co/Cu multilayers recently reported by Gijs {\it et al}.Comment: 20 pages (LATEX), 5 figures available on request to [email protected]

Dynamics of Information Entropies in Nonextensive Systems

We have discussed dynamical properties of the Tsallis entropy and the generalized Fisher information in nonextensive systems described by the Langevin model subjected to additive and multiplicative noise. Analytical expressions for the time-dependent Tsallis entropy and generalized Fisher information have been obtained with the use of the $q$-moment approach to the Fokker-Planck equation developed in a previous study [H. Hasegawa, Phys. Rev. E {\bf 77}, 031133 (2008)]. Model calculations of the information entropies in response to an applied pulse and sinusoidal inputs have been presented.Comment: 21 pages, 8 figures, augmented text with changed titl

A fundamental work on THz measurement techniques for application to steel manufacturing processes

The terahertz (THz) waves had not been obtained except by a huge system, such as a free electron laser, until an invention of a photo-mixing technique at Bell laboratory in 1984 [1]. The first method using the Auston switch could generate up to 1 THz [2]. After then, as a result of some efforts for extending the frequency limit, a combination of antennas for the generation and the detection reached several THz [3, 4]. This technique has developed, so far, with taking a form of filling up the so-called THz gap . At the same time, a lot of researches have been trying to increase the output power as well [5-7]. In the 1990s, a big advantage in the frequency band was brought by non-linear optical methods [8-11]. The technique led to drastically expand the frequency region and recently to realize a measurement up to 41 THz [12]. On the other hand, some efforts have yielded new generation and detection methods from other approaches, a CW-THz as well as the pulse generation [13-19]. Especially, a THz luminescence and a laser, originated in a research on the Bloch oscillator, are recently generated from a quantum cascade structure, even at an only low temperature of 60 K [20-22]. This research attracts a lot of attention, because it would be a breakthrough for the THz technique to become widespread into industrial area as well as research, in a point of low costs and easier operations. It is naturally thought that a technology of short pulse lasers has helped the THz field to be developed. As a background of an appearance of a stable Ti:sapphire laser and a high power chirped pulse amplification (CPA) laser, instead of a dye laser, a lot of concentration on the techniques of a pulse compression and amplification have been done. [23] Viewed from an application side, the THz technique has come into the limelight as a promising measurement method. A discovery of absorption peaks of a protein and a DNA in the THz region is promoting to put the technique into practice in the field of medicine and pharmaceutical science from several years ago [24-27]. It is also known that some absorption of light polar-molecules exist in the region, therefore, some ideas of gas and water content monitoring in the chemical and the food industries are proposed [28-32]. Furthermore, a lot of reports, such as measurements of carrier distribution in semiconductors, refractive index of a thin film and an object shape as radar, indicate that this technique would have a wide range of application [33-37]. I believe that it is worth challenging to apply it into the steel-making industry, due to its unique advantages. The THz wavelength of 30-300 ¼m can cope with both independence of a surface roughness of steel products and a detection with a sub-millimeter precision, for a remote surface inspection. There is also a possibility that it can measure thickness or dielectric constants of relatively high conductive materials, because of a high permeability against non-polar dielectric materials, short pulse detection and with a high signal-to-noise ratio of 103-5. Furthermore, there is a possibility that it could be applicable to a measurement at high temperature, for less influence by a thermal radiation, compared with the visible and infrared light. These ideas have motivated me to start this THz work