International Journal of Modern Physics B

In this review, we rederive the controversial influence functional approach of Golubev and Zaikin (GZ) for interacting electrons in disordered metals in a way that allows us to show its equivalence, before disorder averaging, to diagrammatic Keldysh perturbation theory. By representing a certain Pauli factor occuring in GZ's effective action in the frequency domain (instead of the time domain, as GZ do), we also achieve a more accurate treatment of recoil effects. With this change, GZ's approach reproduces, in a remarkably simple way, the standard, generally accepted result for the decoherence rate. — The main text and appendices A.1 to A.3 of the present review are comparatively brief, and have been published previously; for convenience, they are included here again (with minor revisions). The bulk of the review is contained in several additional, lengthy appendices containing the relevant technical details.

The electronic properties of ErPd₂Sn are studied by band structure calculation based on the density functional theory within LDA, LDA+U, and fully relativistic schemes. When the Coulomb potential is added to the Er 4f orbitals, the degeneracy between the different f orbitals is lifted, and they are split into lower Hubbard bands and upper Hubbard bands. The fully relativistic band structure scheme shows that spin–orbit coupling splits the 4f states into two manifolds, the 4f_7/2 and the 4f_5/2 multiplet.

The spin Hamiltonian (SH) parameters g factors g_‖, g_⊥ and the hyperfine structure constants A_‖ and A_⊥ for the tetragonal Cu²⁺ centers (i.e., [CuX₄(H₂O)₂] clusters) in NH₄X(X = Cl, Br, I) are theoretically investigated by means of the diagonalization procedure of complete (10×10) energy matrix (DPCEM) for a 3d⁹ ion in tetragonal symmetry. The crystal-field parameters in the energy matrix are determined from the superposition model. The calculated SH parameters are in reasonable agreement with the experimental data.

Critical phenomena in systems which have a joint multicritical and Lifshitz-point-like behavior are investigated. An expression for the upper critical dimension of such systems is found. A condition of the variational scale invariance of the considered model is specified. If the space dimension coincides with the upper critical dimension, then the critical behavior of the fluctuation correction to the heat capacity is similar to that of the heat capacity without order parameter modulation.

A method of thermally assisted magnetic probe recording on a perpendicular medium was characterized. Field emission current from a scanning tunneling microscope (STM) tip was used as a heating source. A strongly-coupled CoNi/Pt multilayered film was used as a recording medium. Pulses with amplitude of 3–7 V were applied between the STM tip and the recording medium. Experiments show that magnetic marks were formed for voltages of 5–7 V, with an average size of 170 nm. No marks were observed for lower voltages. The model is built to simulate the dynamic process of domain formation in probe-based magnetic recording system. Simulation results agree with experiments.

Two sets of amorphous carbon materials prepared at different routes are irradiated with swift (145 MeV) heavy ion (Ne⁶⁺). The structural parameters like the extent of local ordering along the c and a axis i.e., L_c and L_a, the average spacing of the crystallographic planes (002) i.e., d₀₀₂ and the fraction of the amorphous phase of the unirradiated and the irradiated samples are estimated by X-ray diffraction technique. The fraction of the amorphous phase is generally found to increase with the irradiation dose for both sets of the samples. The estimated d₀₀₂ values are found to be almost unaffected by irradiation but L_c and L_a are decreased slightly with irradiation. The estimated values of L_c and L_a corroborate with the increase of disorder in both sets of the samples with the increasing dose of irradiation.

Ni–Al intermetallic compounds nanocrystalline thin films were deposited by direct current magnetron co-sputtering from elemental Ni and Al targets. The integrity of the thin films and their elemental compositions were assessed using a scanning electron microscope (SEM) equipped with an energy dispersive spectroscope analyzer. The morphologies of thin alloy films are density and smoothing characterized by atomic force microscope and SEM. The preferred (111) orientation in both as-deposited and annealed films are identified using X-ray diffractometer (XRD). The electrical properties of the alloy films were studied, and show good metallic conduction characteristics. From room temperature to 200°C, the resistance of the thin films are assumed to be linear as a function of varying temperature. All the thin films show a positive temperature coefficient of resistance (TCR). As 1% O₂ was introduced into the vacuum chamber during sputtering, the root mean square roughness of the films increased, grain size turned out to be smaller, and the crystallization process was blocked. The amorphous Al₂O₃ phase was found in XRD patterns. The results of TCR measurement show a different electric conduction mechanism compared with alloy films.

Occurring in many natural and engineered systems, the collective synchronization of oscillators has attracted much research attention to understand its behavior. Following the well-known similarity of the synchronization to a condensation phase transition, we present a new approach on how a distribution kinetics model for cluster growth can be adapted to describe synchronization dynamics. We find that oscillators which synchronize, or cluster, according to a reversible association-dissociation mechanism demonstrate behavior like the conventional stability analysis. Oscillators proceed through exponential time dependence before taking on the power law behavior at intermediate times, as reported for model computations. The power varies for synchronization and depends on the rate coefficient, but is constant for desynchronization. In this analysis, the rate coefficient for cluster growth replaces the coupling constant in the conventional linear analysis. In terms of the coupling constant K and its critical value K_c, the coherence increases as (1-K_c/K), the expression that has been found to hold in the absence of noise.

This paper analyzes the encryption and weaknesses of E. Álvarez cryptography. On the basis of this, a new chaotic cryptography based on ergodicity is presented. The control parameter and the initial condition of the chaotic system are chosen as a secret key. A bit chain is generated by iterating the chaotic map, and the location where a plaintext grouping appears in the chain is found. We then write down the number of iterations of the chaotic map as the ciphertext grouping. Several weaknesses of the E. Álvarez cryptography are avoided in the new scheme, and the security of the new scheme is improved. In the end, the new cryptography is studied experimentally using the Logistic map, where the new cryptography's confusion and diffusion is validated, and its effectiveness is also illuminated.

An analysis has been presented using the Roy-Roy equation of state (EOS), which represents an extended and modified version of the Murnaghan EOS. It is found that the value of for various types of solids remain between 5/3 and 2. The Roy-Roy EOS has been found to become applicable for the core of the Earth, predicting the values of the pressure and bulk modulus in the range of seismological data. Modifications suggested recently to remove the shortcomings of the Murnaghan equation have been discussed. The maximum values of obtained from the Roy-Roy EOS for different inorganic solids and organic solids are also discussed.