Noncommutative D-Brane in Non-Constant NS-NS B Field Background

We show that when the field strength H of the NS-NS B field does not vanish, the coordinates X and momenta P of an open string endpoints satisfy a set of mixed commutation relations among themselves. Identifying X and P with the coordinates and derivatives of the D-brane world volume, we find a new type of noncommutative spaces which is very different from those associated with a constant B field background.Comment: 11 pages, Latex, minor modification

Aspects of U-duality in BLG models with Lorentzian metric 3-algebras

In our previous paper, it was shown that BLG model based on a Lorentzian metric 3-algebra gives Dp-brane action whose worldvolume is compactified on torus T^d (d=p-2). Here the 3-algebra was a generalized one with d+1 pairs of Lorentzian metric generators and expressed in terms of a loop algebra with central extensions. In this paper, we derive the precise relation between the coupling constant of the super Yang-Mills, the moduli of T^d and some R-R flux with VEV's of ghost fields associated with Lorentzian metric generators. In particular, for d=1, we derive the Yang-Mills action with theta term and show that SL(2,Z) Montonen-Olive duality is realized as the rotation of two VEV's. Furthermore, some moduli parameters such as NS-NS 2-form flux are identified as the deformation parameters of the 3-algebras. By combining them, we recover most of the moduli parameters which are required by U-duality symmetry.Comment: 27 pages, v2: minor correction

Silicon solar cells for space use: Present performance and trends

A technology assessment of present performance levels and current fabrication methods and designs is presented

Circumbinary Molecular Rings Around Young Stars in Orion

We present high angular resolution 1.3 mm continuum, methyl cyanide molecular line, and 7 mm continuum observations made with the Submillimeter Array and the Very Large Array, toward the most highly obscured and southern part of the massive star forming region OMC1S located behind the Orion Nebula. We find two flattened and rotating molecular structures with sizes of a few hundred astronomical units suggestive of circumbinary molecular rings produced by the presence of two stars with very compact circumstellar disks with sizes and separations of about 50 AU, associated with the young stellar objects 139-409 and 134-411. Furthermore, these two circumbinary rotating rings are related to two compact and bright {\it hot molecular cores}. The dynamic mass of the binary systems obtained from our data are $\geq$ 4 M$_\odot$ for 139-409 and $\geq$ 0.5 M$_\odot$ for 134-411. This result supports the idea that intermediate-mass stars will form through {\it circumstellar disks} and jets/outflows, as the low mass stars do. Furthermore, when intermediate-mass stars are in multiple systems they seem to form a circumbinary ring similar to those seen in young, multiple low-mass systems (e.g., GG Tau and UY Aur).Comment: Accepted by Astronomy and Astrophysic

Characterization Of Thermal Stresses And Plasticity In Through-Silicon Via Structures For Three-Dimensional Integration

Through-silicon via (TSV) is a critical element connecting stacked dies in three-dimensional (3D) integration. The mismatch of thermal expansion coefficients between the Cu via and Si can generate significant stresses in the TSV structure to cause reliability problems. In this study, the thermal stress in the TSV structure was measured by the wafer curvature method and its unique stress characteristics were compared to that of a Cu thin film structure. The thermo-mechanical characteristics of the Cu TSV structure were correlated to microstructure evolution during thermal cycling and the local plasticity in Cu in a triaxial stress state. These findings were confirmed by microstructure analysis of the Cu vias and finite element analysis (FEA) of the stress characteristics. In addition, the local plasticity and deformation in and around individual TSVs were measured by synchrotron x-ray microdiffraction to supplement the wafer curvature measurements. The importance and implication of the local plasticity and residual stress on TSV reliabilities are discussed for TSV extrusion and device keep-out zone (KOZ).Microelectronics Research Cente

Stress-Induced Delamination Of Through Silicon Via Structures

Continuous scaling of on-chip wiring structures has brought significant challenges for materials and processes beyond the 32 nm technology node in microelectronics. Recently three-dimensional (3-D) integration with through-silicon-vias (TSVs) has emerged as an effective solution to meet the future interconnect requirement. Thermo-mechanical reliability is a key concern for the development of TSV structures used in die stacking as 3-D interconnects. This paper examines the effect of thermal stresses on interfacial reliability of TSV structures. First, the three-dimensional distribution of the thermal stress near the TSV and the wafer surface is analyzed. Using a linear superposition method, a semi-analytic solution is developed for a simplified structure consisting of a single TSV embedded in a silicon (Si) wafer. The solution is verified for relatively thick wafers by comparing to numerical results obtained by finite element analysis (FEA). Results from the stress analysis suggest interfacial delamination as a potential failure mechanism for the TSV structure. Analytical solutions for various TSV designs are then obtained for the steady-state energy release rate as an upper bound for the interfacial fracture driving force, while the effect of crack length is evaluated numerically by FEA. Based on these results, the effects of TSV designs and via material properties on the interfacial reliability are elucidated. Finally, potential failure mechanisms for TSV pop-up due to interfacial fracture are discussed.Aerospace Engineerin

Branes from a non-Abelian (2,0) tensor multiplet with 3-algebra

In this paper, we study the equations of motion for non-Abelian N=(2,0) tensor multiplets in six dimensions, which were recently proposed by Lambert and Papageorgakis. Some equations are regarded as constraint equations. We employ a loop extension of the Lorentzian three-algebra (3-algebra) and examine the equations of motion around various solutions of the constraint equations. The resultant equations take forms that allow Lagrangian descriptions. We find various (5+d)-dimensional Lagrangians and investigate the relation between them from the viewpoint of M-theory duality.Comment: 44+1 pages, reference added, typos corrected, and several discussions added; v3, reference added, many typos corrected, the language improved; v4, some typos and references corrected, final version to appear in J. Phys.

A new observational and numerical study of tidal interactions in M81-M82-NGC3077 system

A nearby system of interacting galaxies M81-M82-NGC3077 triplet (D = 3.3 Mpc; Freeman & Madore 1988) has been studied using multi-wavelength observations and numerical simulations to obtain a comprehensive understanding on the dynamics and the consequences of tidal interactions in a group environment. The VLA 12-field Mosaic H I observations of 2 x 1.5 deg. region have revealed a vast array of H I filaments which suggests that the severity and extent of tidal disruptions far exceed the previous estimates. A tidal remnant of the former H I disk of M82 extending up to 30 kpc (in projection) is identified for the first time, and the pervasive effects of the tidal disruption are traced into the inner disk by optical and CO observations, including a kinematic trace of a large scale bar potential (Yun, Ho, & Lo 1992). The H I disk of M81 is traced out to 40 kpc in radius, and a large scale (l approx. 20 kpc) velocity anomaly ('High Velocity Trough'), which may be a remnant of a gaseous collision, is found within the disk of M81. The large H I bridge between M81 and NGC 3077 (van der Hulst 1979) is also found to extend approx. greater than 50 kpc further, bending around NGC 3077, toward M82. The total H I detected in this experiment, 5.6 x 10(exp 9) solar mass, represents the majority of the single-dish flux (Appleton, Davies, & Stephenson 1981) and suggests that the bulk of H I found in the region belongs to the three galaxies and the tidal filaments. The impact and details of the tidal interactions have been further examined through the use of numerical techniques. The 'restricted 3-body' approach was used to simulate the observed distribution of tidal H I streamers connecting the three galaxies, and the success of the simulation is further strengthened by the accurate predictions on the gas kinematics