Zonal flow dynamics and control of turbulent transport in stellarators

The relation between magnetic geometry and the level of ion-temperature-gradient (ITG) driven turbulence in stellarators is explored through gyrokinetic theory and direct linear and nonlinear simulations. It is found that the ITG radial heat flux is sensitive to details of the magnetic configuration that can be understood in terms of the linear behavior of zonal flows. The results throw light on the question of how the optimization of neoclassical confinement is related to the reduction of turbulence.     

Unified fields in pentadimensional theory

The theory of Jordan-Thiry is investigated by using a five-dimensional Riemannian manifold V₅ which admits a one-parameter group of isometries. The set of trajectories is supposed to represent the space-time of Relativity.The use of the induced metric in the quotient space leads to essential difficulties. It is necessary to consider a conformal metric and to modify the energy tensor in order to obtain the classical results of relativistic celestial mechanics. Moreover, the conformal metric brings out the evident interpretation of the fifteenth potential like a massless scalar field.A mass term referring to the scalar field is introduced; then the gravitational, electromagnetic, and mesonic scalar fields are unified through the metric of V₅. Several results make the new theory very coherent; in particular, the exact relativistic equations of motion are obtained asymptotically when the matter density vanishes.Exact solutions are searched. The classical Schwarzschild solution and neighbouring solutions are valid in the interior of the matter. Special non-static solutions are also obtained; some of these may be interpreted locally as describing the “collapse” of neutron stars; others ones, analogous to Robertson's metric, can be used to build a cosmology of the unified field.     

Phase ripple correction: theory and application

Spectral phase ripple associated with novel dispersive devices can distort broadband optical signals. We present a digital postprocessing algorithm to correct for this distortion by exploiting the static deterministic nature of the ripple. This algorithm is demonstrated with empirical data for several systems employing chirped fiber Bragg gratings (CFBGs). We employ this technique in a photonic time-stretch system incorporating CFBGs, improving the signal fidelity by 9 dB. Simulations and experiments show that this algorithm, which can be reduced to a simple interpolation and matrix multiplication, also mitigates additive noise. We see that the act of distortion correction yields signal fidelity superior to that of an ideal dispersive element.     

Intrinsic ambipolarity and rotation in stellarators

It is shown that collisional plasma transport is intrinsically ambipolar only in quasiaxisymmetric or quasihelically symmetric magnetic configurations. Only in such fields can the plasma rotate freely, and then only in the direction of quasisymmetry. In a non-quasi-symmetric magnetic field, the average radial electric field is determined by parallel viscosity, which in turn is usually governed by collisional processes. Locally, the radial electric field may be affected by turbulent Reynolds stress producing zonal flows, but on a radial average taken over several ion gyroradii, it is determined by parallel viscosity, at least if the turbulence is electrostatic and obeys the conventional gyrokinetic orderings. This differs from the situation in a tokamak, where there is no flow damping by parallel viscosity in the symmetry direction and the turbulent Reynolds stress may affect the global radial electric field.     

Unified field theory with homotopic charge

Previously proposed field equations for the field which maps points in space-time to points on the two-sphere are derived from a suitable Lagrangian. The original conjecture that this theory may be the nonlinear theory of electrodynamics which has charge quantization as a topological property is supported by this result. Problems with this interpretation are indicated.     

Unified field theory of quarks and electrons

A unified gauge theory of quarks and electrons in which electromagnetic and strong interactions are both transmitted by the same vector field is formulated. It is argued that the theory is finite and that it is in agreement with observed electromagnetic and nuclear phenomena.     

Unified theory of high-Tc superconductivity in BSCCO and YBCO

This paper shows that in YBCO and BSCCO there are five kinds of waves for the order parameter, d, pl, p2, s and extended s, and explains six important experimental facts.     

High-beta equilibria of drift-optimized compact stellarators

Compact stellarator configurations have been obtained with good neoclassical confinement that are stable to both pressure- and current-driven modes for high values of beta. These configurations are drift-optimized tokamak-stellarator hybrids with a high-shear tokamak-like rotational transform profile and /B/ that is approximately poloidally symmetric. The bootstrap current is consistent with the required equilibrium current and, while larger than that in existing stellarators, is typically only a small fraction (1/3-1/5) of that in an equivalent tokamak. These configurations have strong magnetic wells and consequently high interchange stability beta limits up to beta=23%. Because of the reduced bootstrap current, these configurations are stable to low-n ideal MHD kink modes with no wall stabilization for values of beta ( approximately 7%-11%) significantly larger than in an equivalent advanced tokamak.     

Unified study and transport properties of simple metals

The resistivity, thermoelectric power at the melting points and temperature variation of resistivity of the liquid alkali metals are studied with local Heine-Abarenkov and the modified Ashcroft pseudopotentials. The parameters of the model potentials are obtained from a unified study of the static and dynamic properties of the metals. The effect of different dielectric function and structure factor on the transport properties is discussed. It is shown that the simple modified Ashcroft pseudopotential reproduces the result fairly well except for Li and Cs.     

Unified theory of model reduction via Gleason measures

Previous work on the stochastic realization and approximation problem has cast this problem in the framework of theRV-coefficient, a measure of correlation recently introduced in the multivariate statistical literature. This allowed the introduction of a common measure for the goodness of fit for the different realization algorithms. This paper explores the deeper geometrical and logical foundation for this common measure in a unified theory for the data-driven and the exact covariance approaches.     

Unified geometric theory of electromagnetic and gravitational interactions

A geometric unification of the electromagnetic and gravitational fields is presented. The unified field is described by a linear connection on the space-time. Field equations for the unified field are equivalent to Einstein-Maxwell equations. Field equations for matter interacting with the unified field are the usual ones. The interaction of the unified field with a charged scalar field is studied in detail.This work has been written under the financial support of: Gruppo Nazionale per la Fisica Matematica of the Italian National Research Council.     

Unified theory of dynamically suppressed qubit decoherence in thermal baths

We develop a unified theory of dynamically suppressed decay and decoherence by external fields in qubits coupled to arbitrary thermal baths and dephasing sources. This general theory does not invoke the rotating-wave approximation, which fails for ultrafast field-induced modulations of qubit-bath coupling. Considerations for optimizing the dynamical suppression are outlined.     

Broad resonances in transport theory

We discuss the extension of the transport theoretical framework to include states with a broad mass distribution. We focus on the proper life-time and cross sections for a state with an arbitrarily given invariant mass.