Statistics of Entropy Production in Linearized Stochastic System

We consider a wide class of linear stochastic problems driven off the equilibrium by a multiplicative asymmetric force. The force brakes detailed balance, maintained otherwise, thus producing entropy. The large deviation function of the entropy production in the system is calculated explicitly. The general result is illustrated using an example of a polymer immersed in a gradient flow and subject to thermal fluctuations.Comment: 4 pages, 1 figur

Proof Relevant Corecursive Resolution

Resolution lies at the foundation of both logic programming and type class context reduction in functional languages. Terminating derivations by resolution have well-defined inductive meaning, whereas some non-terminating derivations can be understood coinductively. Cycle detection is a popular method to capture a small subset of such derivations. We show that in fact cycle detection is a restricted form of coinductive proof, in which the atomic formula forming the cycle plays the role of coinductive hypothesis. This paper introduces a heuristic method for obtaining richer coinductive hypotheses in the form of Horn formulas. Our approach subsumes cycle detection and gives coinductive meaning to a larger class of derivations. For this purpose we extend resolution with Horn formula resolvents and corecursive evidence generation. We illustrate our method on non-terminating type class resolution problems.Comment: 23 pages, with appendices in FLOPS 201

Probing the microscopic structure of bound states in quantum point contacts

Using an approach that allows us to probe the electronic structure of strongly pinched-off quantum point contacts (QPCs), we provide evidence for the formation of self-consistently realized bound states (BSs) in these structures. Our approach exploits the resonant interaction between closely-coupled QPCs, and demonstrates that the BSs may give rise to a robust confinement of single spins, which show clear Zeeman splitting in a magnetic field

A model for microinstability destabilization and enhanced transport in the presence of shielded 3-D magnetic perturbations

A mechanism is presented that suggests shielded 3-D magnetic perturbations can destabilize microinstabilities and enhance the associated anomalous transport. Using local 3-D equilibrium theory, shaped tokamak equilibria with small 3-D deformations are constructed. In the vicinity of rational magnetic surfaces, the infinite-n ideal MHD ballooning stability boundary is strongly perturbed by the 3-D modulations of the local magnetic shear associated with the presence of nearresonant Pfirsch-Schluter currents. These currents are driven by 3-D components of the magnetic field spectrum even when there is no resonant radial component. The infinite-n ideal ballooning stability boundary is often used as a proxy for the onset of virulent kinetic ballooning modes (KBM) and associated stiff transport. These results suggest that the achievable pressure gradient may be lowered in the vicinity of low order rational surfaces when 3-D magnetic perturbations are applied. This mechanism may provide an explanation for the observed reduction in the peak pressure gradient at the top of the edge pedestal during experiments where edge localized modes have been completely suppressed by applied 3-D magnetic fields

The relationship between chaotic behavior and tunneling effect in quantum transport devices(1)Current topics of quantum chaos in nanosciences, Chaos and Nonlinear Dynamics in Quantum-Mechanical and Macroscopic Systems)

この論文は国立情報学研究所の電子図書館事業により電子化されました。狭い金属ゲート(QPC)を両端に有する開放型量子ドットについて、零磁場近傍の磁気抵抗のピーク形状が、ゲート電圧を変化させることによってローレンツ型とカスプ型が交互に現れる現象が観測された。このローレンツ型とカスプ型が交互に現れる要因としては、QPCによるトンネリング効果と量子ドットによる弱局在の両方が関係しているものではないかと推測され、考察を行った。We have studied transport properties in the low-temperature magnetoresistance through the ballistic narrow path restricted by short width metallic gates, which cause a quantum point contact(QPC) which have a saddle point potential, on the 2 dimensional electron gas(2DEG) system. An alternate and systematic variation between a Lorentzian line fitting and a cusplike line fitting in the zero-field peaks has been observed, as sweeping the gate voltage. It indicates a possibility of existence of chaotic and regular paths on the short gated ballistic/tunneling transport. We will discuss on the quantum chaos behavior on the systematic variation between the Lorentzian and the cusp-like peakshape based on the disordered path system under the short gate, and suggest a relation with level repulsion of energy spectrum

High energy cosmic-rays: puzzles, models, and giga-ton neutrino telescopes

The existence of cosmic rays of energies exceeding 10^20 eV is one of the mysteries of high energy astrophysics. The spectrum and the high energy to which it extends rule out almost all suggested source models. The challenges posed by observations to models for the origin of high energy cosmic rays are reviewed, and the implications of recent new experimental results are discussed. Large area high energy cosmic ray detectors and large volume high energy neutrino detectors currently under construction may resolve the high energy cosmic ray puzzle, and shed light on the identity and physics of the most powerful accelerators in the universe.Comment: 12 pages, 7 figures; Summary of review talk, PASCOS 03 (Mumbai, India

Extension of the Cosmic-Ray Energy Spectrum Beyond the Predicted Greisen-Zatsepin-Kuz'min Cutoff

The cosmic-ray energy spectrum above 10^{18.5} eV is reported using the updated data set of the Akeno Giant Air Shower Array (AGASA) from February 1990 to October 1997. The energy spectrum extends beyond 10^{20} eV and the energy gap between the highest energy event and the others is being filled up with recently observed events. The spectral shape suggests the absence of the 2.7 K cutoff in the energy spectrum or a possible presence of a new component beyond the 2.7 K cutoff.Comment: to be published in PRL, 3 figures, REVTEX forma