Landau levels in a novel two-dimensional electron system interacting with charged quantum dots

Landau levels have been theoretically investigated in a two-dimensional electron gas near a quantum dot (QD) layer. By a diagrammatical method, we have formulated the self-energy for the Landau level and deduced its relation to the AC conductivity σ_loc(ω) in the QD layer. As an example, we have examined the density of states in the case where σ_loc(ω) is described by Aω^S(S=0.8). It is found that the Landau levels are broadened due to the interaction with the localized electrons in the QDs.     

Simultaneous observation of CO isotopomer absorption by broadband difference-frequency generation using a direct-bonded quasi-phase-matched LiNbO3 waveguide

Rovibration absorption lines both of 12CO and 13CO are observed simultaneously with the output of a 2 microm broadband difference frequency generated in a direct-bonded quasi-phase-matched LiNbO3 waveguide, which is a 50 mm device with a single quasi-phase-matching period that is operated at a constant temperature. The wavelength conversion efficiency and the difference-frequency generation bandwidth reach 100%/W and 100 nm, respectively. The idler output bandwidth in the 2 microm region is obtained by group-velocity matching or phase-mismatch minimization when a 0.94 microm pump laser diode and a 1.55 microm tunable signal source are used.     

Generators of Spn(V) over a quasi semilocal semihereditary ring

This paper is devoted to determine the minimal length of expressions of an isometry in a symplectic group Sp_n(V) by a product of transvections under the assumption that V is an n-ary nonsingular alternating space over a quasi semilocal semihereditary ring with 2 as a unit.     

Plasma production by helicon and slow waves

The observation of slow-wave sustained (SW) discharge in a whistler- or helicon-wave range of frequency is made using high-frequency and very-high-frequency bands of rf. The SW discharge occurs at an extremely low rf power and plasma density, which are lower than a capacitive-coupling discharge region.     

Development of a “Built-in” Scanning Near Field Microscope Head for an Atomic Force Microscope System and Stress Mapping of an Al2O3/ZrO2 Eutectic Composite

We constructed a scanning near-field optical microscope (SNOM) on a commercially available atomic force microscopy (AFM) apparatus (SPM-9500J2; Shimadzu Corp.) to measure the stress distribution in ceramic composite materials. Features of our SNOM system are: (1) a compact SNOM head substituted for the original AFM head; (2) a wide scanning range (125 × 125 μm²) inherited from the original scanner; (3) use of conventional shear-force regulation; (4) an optical system for the illumination-collection (I-C) mode; (5) excitation by a 488 nm line of an Ar-ion laser, and (6) light detection by photon counting or a polychromator equipped with an electronically cooled charge coupled device (CCD). This SNOM system was used to measure the surface structure and stress distribution of an Al₂O₃/ZrO₂ eutectic composite. We simultaneously measured topographic images and fluorescence spectra of an Al₂O₃/ZrO₂ eutectic composite. We estimated its peak intensity, peak position, and peak width from the fluorescence spectrum during scanning, which respectively correspond to the abundance of Al₂O₃, stress in the grain, and the anisotropy of that stress. Mapping images showed that the stress and its anisotropy were weaker in the center of the Al₂O₃ grain than its boundary between Al₂O₃ and ZrO₂. That observation suggests that Al₂O₃ underwent intense anisotropic stress induced by volume expansion in the phase transition of ZrO₂ from the cubic phase to the monoclinic phase during preparation.     

Design of a widely tunable laser with a chirped ladder filter

We theoretically investigated a digitally tunable laser with a chirped ladder filter and a ring resonator to obtain a wide wavelength tuning range covering the whole C- or L- band. The clear relation between the tuning range and laser structure, especially the ladder filter, is described analytically. The introduction of a chirped structure into a ladder filter is effective in achieving both wide tunability and a stable lasing mode. A numerical simulation based on multimode rate equations shows that a tuning range of over 40 nm and a mode suppression ratio over 40 dB can be achieved by introducing a chirped ladder filter.     

Computation of betti numbers of monomial ideals associated with cyclic polytopes

We give a combinatorial formula for the Betti numbers which appear in a minimal free resolution of the Stanley-Reisner ringk[Δ(P)]=A/I _Δ(P) of the boundary complex Δ(P) of an odd-dimensional cyclic polytopePover a fieldk. A corollary to the formula is that the Betti number sequence ofk[Δ(P)] is unimodal and does not depend on the base fieldk.     

Lightness Change as Perceived in Relation to the Size of Recognized Visual Space of Illumination

According to the concept of the recognized visual space of illumination (RVSI) the lightness of an object surface is perceived in relation to its conceptualized size. To prove this proposition the lightness of gray test patches was judged when they were located at various positions inside an illuminated space composed of two rooms in the depth direction from a subject. No retinal image arrangement was changed in the test patch and its immediate surroundings, but the front room had walls, floors and furniture lower in lightness by the amount of N1.5 than the back room to make the RVSI of the former smaller despite the illuminance in the entire space being the same. The results showed that the apparent lightness of the patches was perceived higher by amount of about 13 in L units for the N4 test patch and about 20 for N6 when the patches were located in the front room, in accordance with the prediction. It was stressed that the experiment of lightness judgment should be conducted in a three dimensional space rather than two dimensional plane as done by several investigators.     

Finsler geometry of topological singularities for multi‐valued fields: Applications to continuum theory of defects

Topological singularity in a continuum theory of defects and a quantum field theory is studied from a viewpoint of differential geometry. The integrability conditions of singularity (Clairaut‐Schwarz‐Young theorem) are expressed by a torsion tensor and a curvature tensor when a Finslerian intrinsic parallelism holds for the multi‐valued function. In the context of the quantum field theory, the singularity called an extended object is expressed by the torsion when the intrinsic parallelism is related to the spontaneous breakdown of symmetry. In the continuum theory of defects, the path‐dependency of point and line defects within a crystal is interpreted by the non‐vanishing condition of torsion tensor in a non‐Riemannian space osculated from the Finsler space, and the domain is not simply connected. On the other hand, for the rotational singularity, an energy integral (J‐integral) around a disclination field is path‐independent when a nonlinear connection is single‐valued. This means that the topological expression for the sole defect (Gauss‐Bonnet theorem with genus ) is understood by the integrability of nonlinear connection.

     

Boltzmann equation in de Sitter space

In a time dependent background like de Sitter space, Feynman–Dyson perturbation theory breaks down due to infra-red divergences. We investigate an interacting scalar field theory in Schwinger–Keldysh formalism. We derive a Boltzmann equation from a Schwinger–Dyson equation inside the cosmological horizon. Our solution shows that the particle production is compensated by the reduction of the on-shell states due to unitarity. Although the degrees of freedom inside the horizon leads to a small and diminishing screening effect of the cosmological constant, there is a growing screening effect from those outside the horizon.