The 4.7 GB digital versatile disc-recordable (DVD-R) disc format has been developed to introduce very useful recordable feature in the digital versatile disc (DVD) family. We developed disc media and the write pulse control method. In our examination, recorded signal qualities of the DVD-R disc are equivalent to those of the DVD-Read-Only disc (ROM). We realized a jitter value of less than 6% using write pulse strategy with the adaptive edge shift control technology. The physical characteristics of the recorded signals satisfy all the requirements of single-layered DVD-ROM disc.

For high numerical aperture (NA) near-field systems using a solid immersion lens, layer stack types of first-surface read-only-memory (ROM) discs have been investigated. Complicated interactions of high-NA incident and diffracted waves with surface waves occur in multilayer-stacked subwavelength structures on the discs. Therefore, vector diffraction simulation in consideration of these effects is indispensable for the optimization of the disc structures. We used rigorous coupled wave analysis to numerically calculate readout signals from the discs. On the basis of the simulation results, we actually fabricated high-density ROM media. Consequently, a significantly low jitter of 6.8% was obtained for 100 Gbyte ROM media with a designed structure in an NA 2.0 system.

We developed a rewritable optical disc with 4.7 GB/side capacity as an extension of the digital versatile disc recordable (DVD-R) system. The disc is readily playable on a read-only DVD player or a DVD-ROM drive with a small firmware modification. As far as the fundamental characteristics of the disc which adopts an in-groove recording are concerned, the reflectivity is 18% or more, modulated amplitude is 60% or greater, and jitter is 8% or less. As we had sufficient differential phase detection (DPD) tracking error signals from the recorded disc, we think the DPD tracking method is practical. These results cleared the single-layer DVD-ROM specifications except for the reflectivity. The measured reflectivity satisfies the specifications of the dual-layer DVD-ROM disc. Furthermore we confirmed that the recorded disc was playable on a blue laser playback system.

We study the boundary limit of the bulk isometries of AdS × S. The superconformal symmetry is realized on the coordinates of the AdS boundary, the fermionic superspace coordinates, and the harmonics on the sphere. We show how these may be related to the coordinates of an off-shell harmonic superspace of SCFT living on the boundary. In the special case of d = 4, N = 2 super Yang-Mills theory, a truncation of the N = 4 SYM dual to type-IIB string theory compactified on AdS 5 × S 5 , we identify the bosonic space SU(2)/ U(1) of the N = 2 harmonic superspace (known before as auxiliary) with the S 2 submanifold of the S 5 .

By means of two simple examples, phase and amplitude damping, the impact of decoherence on the dynamical Casimir effect is investigated. Even without dissipating energy (i.e., pure phase damping), the amount of created particles can be diminished significantly via the coupling to the environment (reservoir theory) inducing decoherence. For a simple microscopic model, it is demonstrated that spontaneous decays within the medium generate those problems; Rabi oscillations are far more advantageous in that respect. These findings are particularly relevant in view of a recently proposed experimental verification of the dynamical Casimir effect.