The minimal conformal O(N) vector sigma model at d=3

For the minimal O(N) sigma model, which is defined to be generated by the O(N) scalar auxiliary field alone, all n-point functions, till order 1/N included, can be expressed by elementary functions without logarithms. Consequently, the conformal composite fields of m auxiliary fields possess at the same order such dimensions, which are m times the dimension of the auxiliary field plus the order of differentiation.Comment: 15 page

Massive Fields of Arbitrary Integer Spin in Symmetrical Einstein Space

We study the propagation of gauge fields with arbitrary integer spins in the symmetrical Einstein space of any dimensionality. We reduce the problem of obtaining a gauge-invariant Lagrangian of integer spin fields in such background to an purely algebraic problem of finding a set of operators with certain features using the representation of high-spin fields in the form of some vectors of pseudo-Hilbert space. We consider such construction in the linear order in the Riemann tensor and scalar curvature and also present an explicit form of interaction Lagrangians and gauge transformations for massive particles with spins 1 and 2 in terms of symmetrical tensor fields.Comment: 15 pages, latex, no figures,minor change

Synaptic transmission as a cooperative phenomenon in confined systems

In this review paper, the theory of synaptic transmission (ST) was developed and discussed. We used the hypothesis of isomorphism between: (a) the cooperative behavior of mediators --- acetylcholine molecules (ACh) and cholinoreceptors in a synaptic cleft with binding into mediator-receptor (AChR) complexes, (b) the critical phenomena in confined binary liquid mixtures. The systems of two (or three) nonlinear differential equations were proposed to find the change of concentrations of ACh, AChR complexes, and ferment acetylcholinesterase. The main findings of our study: the linear size of the activation zone was evaluated; the process of postsynaptic membrane activation was described as a cooperative process; different approximations of ACh synchronous release were examined; stationary states and types of singular points were studied for the proposed models of ST; the nonlinear kinetic model with three order parameters demonstrated a strange-attractor behavior.Comment: 12 pages, 1 figur

Optimum pulse shapes for stimulated Raman adiabatic passage

Stimulated Raman adiabatic passage (STIRAP), driven with pulses of optimum shape and delay has the potential of reaching fidelities high enough to make it suitable for fault-tolerant quantum information processing. The optimum pulse shapes are obtained upon reduction of STIRAP to effective two-state systems. We use the Dykhne-Davis-Pechukas (DDP) method to minimize nonadiabatic transitions and to maximize the fidelity of STIRAP. This results in a particular relation between the pulse shapes of the two fields driving the Raman process. The DDP-optimized version of STIRAP maintains its robustness against variations in the pulse intensities and durations, the single-photon detuning and possible losses from the intermediate state.Comment: 8 pages, 6 figures. submitted to Phys. Rev.

Scanning Electron Fractography of Body Centered Cubic (BCC) Metals

Scanning electron fractography is an inherent part of investigations of factors which determine the mechanical properties of materials and their failure. Transition bcc metals show the widest variety of fracture mechanisms under uniaxial tension. Brittle fracture is affected by cleavage from various defects - stress concentrators. In brittle-ductile transition, fracture starts by a tough mode but finishes by a brittle one - by cleavage. A fracture mechanism changes after the tough crack has reached some critical length. Mechanisms of subcritical growth are of cleavage with relaxation, inter-granular fracture and dimpled ones. Dimples are observed in ductile fracture. Cleavage is absent. The dimples are nucleated as a result of both failure of particles and their interfaces and delamination of structure elements. All varieties of observed fracture surface may be described as a result of actions of the following mechanisms - cleavage, cleavage with relaxation, pore coalescence, brittle intergranular or intercellular fracture. Fractographical analysis allows one to obtain information not only about the fracture mechanisms but also such characteristics as: fracture toughness, brittle-ductile transition limits, structure transformations preceding fracture