Conservation of asymptotic charges from past to future null infinity: Supermomentum in general relativity

We show that the BMS-supertranslations and their associated supermomenta on past null infinity can be related to those on future null infinity, proving the conjecture of Strominger for a class of spacetimes which are asymptotically-flat in the sense of Ashtekar and Hansen. Using a cylindrical 3-manifold of both null and spatial directions of approach towards spatial infinity, we impose appropriate regularity conditions on the Weyl tensor near spatial infinity along null directions. The asymptotic Einstein equations on this 3-manifold and the regularity conditions imply that the relevant Weyl tensor components on past null infinity are antipodally matched to those on future null infinity. The subalgebra of totally fluxless supertranslations near spatial infinity provides a natural isomorphism between the BMS-supertranslations on past and future null infinity. This proves that the flux of the supermomenta is conserved from past to future null infinity in a classical gravitational scattering process provided additional suitable conditions are satisfied at the timelike infinities.Comment: v2: corrected formula for epsilon in Eqs. A.4E and A.9 v1: (published version in JHEP) 49 pages, 2 figures. arXiv admin note: substantial text overlap with arXiv:1808.0786

Integration of smed and triz in improving productivity at semiconductor industry

A case study on a test handler’s changeover process was conducted in a semiconductor organization (Intel Technology Sdn. Bhd.). The test handler being a constraint operation in the production supports the testing of two of the mainstream chipset products. Though the test handler is capable to support multiple chipset products but due to the equipment configuration complexity, the changeover process today requires an average 4 hours to fully complete. The long changeover duration degrades the overall productivity especially inability to meet customer demand timely, lower utilization and rising cost issues. These identified issues are potential factors that could impact the sustainability of the organization in long run. This case study focuses on improving the changeover process using techniques from Single Minute Exchange of Die (SMED) and Theory of Inventive Problem Solving (TRIZ). Both the techniques have individual strengths and weakness and thus the focus will be to integrate them to complement each other to enhance the changeover process duration further. Problems in the current process like non standard practices, complex hardware setup and waste activities that plagued today are process were identified and categorized accordingly. Later, appropriate techniques from SMED and TRIZ were proposed to counter these issues systematically. SMED will be used mostly for task simplification while TRIZ will be used for hardware part redesigns and overall process optimization. The end of mind of this study is to achieve a lean and optimized changeover process that can be performed below 30 minutes with no safety, quality or output concerns

Opinion : The economics of bankruptcy

Bankruptcy

Shame as it ever was : stigma and personal bankruptcy

Bankruptcy

The growth of unsecured credit : are we better off?

Bankruptcy ; Credit ; Debt

Unemployment insurance and personal bankruptcy

Bankruptcy

Mode Coupling and Cavity-Quantum-Dot Interactions in a Fiber-Coupled Microdisk Cavity

A quantum master equation model for the interaction between a two-level system and whispering-gallery modes (WGMs) of a microdisk cavity is presented, with specific attention paid to current experiments involving a semiconductor quantum dot (QD) embedded in a fiber-coupled, AlGaAs microdisk cavity. In standard single mode cavity QED, three important rates characterize the system: the QD-cavity coupling rate g, the cavity decay rate kappa, and the QD dephasing rate gamma_perpendicular. A more accurate model of the microdisk cavity includes two additional features. The first is a second cavity mode that can couple to the QD, which for an ideal microdisk corresponds to a traveling wave WGM propagating counter to the first WGM. The second feature is a coupling between these two traveling wave WGMs, at a rate beta, due to backscattering caused by surface roughness that is present in fabricated devices. We consider the transmitted and reflected signals from the cavity for different parameter regimes of {g,beta,kappa,gamma_perpendicular}. A result of this analysis is that even in the presence of negligible roughness induced backscattering, a strongly coupled QD mediates coupling between the traveling wave WGMs, resulting in an enhanced effective coherent coupling rate g = sqrt(2)*g0 corresponding to that of a standing wave WGM with an electric field maximum at the position of the QD. In addition, analysis of the second-order correlation function of the reflected signal from the cavity indicates that regions of strong photon antibunching or bunching may be present depending upon the strength of coupling of the QD to each of the cavity modes. Such intensity correlation information will likely be valuable in interpreting experimental measurements of a strongly-coupled QD to a bi-modal WGM cavity.Comment: rev4: updated references and added additional correlation function calculations; to appear in Phys. Rev. A in Feb 200

Momentum space design of high-Q photonic crystal optical cavities

The design of high quality factor (Q) optical cavities in two dimensional photonic crystal (PC) slab waveguides based upon a momentum space picture is presented. The results of a symmetry analysis of defect modes in hexagonal and square host photonic lattices are used to determine cavity geometries that produce modes which by their very symmetry reduce the vertical radiation loss from the PC slab. Further improvements in the Q are achieved through tailoring of the defect geometry in Fourier space to limit coupling between the dominant momentum components of a given defect mode and those momentum components which are either not reflected by the PC mirror or which lie within the radiation cone of the cladding surrounding the PC slab. Numerical investigations using the finite-difference timedomain (FDTD) method predict that radiation losses can be significantly suppressed through these methods, culminating with a graded square lattice design whose total Q approaches 105 with a mode volume of approximately 0.25 cubic half-wavelengths in vacuum