Strain Effect in MgB2/Stainless Steel Superconducting Tape

The influence of mechanical strain on the critical current (Ic) is investigated for MgB2/stainless steel (SUS316) superconducting tapes. The tapes are fabricated by using 'powder in tube' method and deformation process without any heat treatment. The tensile axial strain along tape length is successfully induced to the sample by using a U-shape holder made of stainless steel (SUS304). Two samples are examined at 4.2 K in 5 T (B is applied perpendicular to the tape surface). While the initial Ic at zero external strain state (Ic0) varies (30.4 and 33.3 A), normalized Ic (Ic/Ic0) vs. external strain relations fall on the same curve. Linear increase of Ic is observed from zero external strain state to 0.5% strain (107% of Ic0). Rapid and large degradation occurs at the strain exceeding 0.4-0.5%. High durability against stress can be expected for MgB2/stainless steel superconducting tapes.Comment: 3 pages including 2 figures, submitted to Physica

Single-atom laser generates nonlinear coherent states

The stationary state of a single-atom (single-qubit) laser is shown to be a phase-averaged nonlinear coherent state - an eigenstate of a specific deformed annihilation operator. The solution found for the stationary state is unique and valid for all regimes of the single-qubit laser operation. We have found the parametrization of the deformed annihilation operator which provides superconvergence in finding the stationary state by iteration. It is also shown that, contrary to the case of the usual laser with constant Einstein coefficients describing transition probabilities, for the single-atom laser the interaction-induced transition probabilities effectively depend on the field intensity

Ginzburg - Landau equation from SU(2) gauge field theory

The dual superconductor picture of the QCD vacuum is thought to describe various aspects of the strong interaction including confinement. Ordinary superconductivity is described by the Ginzburg-Landau (GL) equation. In the present work we show that it is possible to arrive at a GL-like equation from pure SU(2) gauge theory. This is accomplished by using Abelian projection to split the SU(2) gauge fields into an Abelian subgroup and its coset. The two gauge field components of the coset part act as the effective, complex, scalar field of the GL equation. The Abelian part of the SU(2) gauge field is then analogous to the electromagnetic potential in the GL equation. An important aspect of the dual superconducting model is for the GL Lagrangian to have a spontaneous symmetry breaking potential, and the existence of Nielsen-Olesen flux tube solutions. Both of these require a tachyonic mass for the effective scalar field. Such a tachyonic mass term is obtained from the condensation of ghost fields.Comment: 7 pages, LATE

Synergetics and computers

AbstractSynergetics deals with complex systems composed of many subsystems and the way these systems form spatial, temporal, or functional structures via selforganization. Though the systems may belong to e.g., physics, chemistry, biology, sociology, economy, close to situations where the structure change, the structures are determined by the same basic principles, briefly outlined in this article. We then discuss possible exploitations of these principles and phenomena in the design of computer hardware

Euler characteristic and quadrilaterals of normal surfaces

Let $M$ be a compact 3-manifold with a triangulation $\tau$. We give an inequality relating the Euler characteristic of a surface $F$ normally embedded in $M$ with the number of normal quadrilaterals in $F$. This gives a relation between a topological invariant of the surface and a quantity derived from its combinatorial description. Secondly, we obtain an inequality relating the number of normal triangles and normal quadrilaterals of $F$, that depends on the maximum number of tetrahedrons that share a vertex in $\tau$.Comment: 7 pages, 1 figur

Field quantization for chaotic resonators with overlapping modes

Feshbach's projector technique is employed to quantize the electromagnetic field in optical resonators with an arbitray number of escape channels. We find spectrally overlapping resonator modes coupled due to the damping and noise inflicted by the external radiation field. For wave chaotic resonators the mode dynamics is determined by a non--Hermitean random matrix. Upon including an amplifying medium, our dynamics of open-resonator modes may serve as a starting point for a quantum theory of random lasing.Comment: 4 pages, 1 figur

Theory of the spatial structure of non-linear lasing modes

A self-consistent integral equation is formulated and solved iteratively which determines the steady-state lasing modes of open multi-mode lasers. These modes are naturally decomposed in terms of frequency dependent biorthogonal modes of a linear wave equation and not in terms of resonances of the cold cavity. A one-dimensional cavity laser is analyzed and the lasing mode is found to have non-trivial spatial structure even in the single-mode limit. In the multi-mode regime spatial hole-burning and mode competition is treated exactly. The formalism generalizes to complex, chaotic and random laser media.Comment: 4 pages, 3 figure

Effects of external global noise on the catalytic CO oxidation on Pt(110)

Oxidation reaction of CO on a single platinum crystal is a reaction-diffusion system that may exhibit bistable, excitable, and oscillatory behavior. We studied the effect of a stochastic signal artificially introduced into the system through the partial pressure of CO. First, the external signal is employed as a turbulence suppression tool, and second, it modifies the boundaries in the bistable transition between the CO and oxygen covered phases. Experiments using photoemission electron microscopy (PEEM) together with numerical simulations performed with the Krischer-Eiswirth-Ertl (KEE) model are presented.Comment: 15 pages, 7 figures, accepted in J. Chem. Phy

Local interaction scale controls the existence of a non-trivial optimal critical mass in opinion spreading

We study a model of opinion formation where the collective decision of group is said to happen if the fraction of agents having the most common opinion exceeds a threshold value, a \textit{critical mass}. We find that there exists a unique, non-trivial critical mass giving the most efficient convergence to consensus. In addition, we observe that for small critical masses, the characteristic time scale for the relaxation to consensus splits into two. The shorter time scale corresponds to a direct relaxation and the longer can be explained by the existence of intermediate, metastable states similar to those found in [P.\ Chen and S.\ Redner, Phys.\ Rev.\ E \textbf{71}, 036101 (2005)]. This longer time-scale is dependent on the precise condition for consensus---with a modification of the condition it can go away.Comment: 4 pages, 6 figure

Quantum shape effects on Zeeman splittings in semiconductor nanostructures

We develop a general method to calculate Zeeman splittings of electrons and holes in semiconductor nanostructures within the tight-binding framework. The calculation is carried out in the electron-hole picture and is extensible to the excitonic calculation by including the electron-hole Coulomb interaction. The method is suitable for the investigation of quantum shape effects and the anisotropy of the g-factors. Numerical results for CdSe and CdTe nanostructures are presented