Pions in isospin asymmetric matter and nuclear Drell-Yan scattering

Using a self-consistent delta-hole model the pion propagation in isospin asymmetric nuclear matter is studied. In neutron-rich matter, corresponding to heavy nuclei, a significant difference in positive and negative pion light-cone distributions is obtained leading to a nuclear enhancement of up antiquark distribution compared to the down antiquark one. This means that the sea-quark asymmetry in the free nucleon cannot be extracted model independently from an experiment on a neutron-rich nucleus.Comment: 10 pages, 3 figures (included), Latex 2.09, uses elsart.sty, epsf.st

Correlated Hybrid Fluctuations from Inflation with Thermal Dissipation

We investigate the primordial scalar perturbations in the thermal dissipative inflation where the radiation component (thermal bath) persists and the density fluctuations are thermally originated. The perturbation generated in this model is hybrid, i.e. it consists of both adiabatic and isocurvature components. We calculate the fractional power ratio ($S$) and the correlation coefficient ($\cos\Delta$) between the adiabatic and the isocurvature perturbations at the commencing of the radiation regime. Since the adiabatic/isocurvature decomposition of hybrid perturbations generally is gauge-dependent at super-horizon scales when there is substantial energy exchange between the inflaton and the thermal bath, we carefully perform a proper decomposition of the perturbations. We find that the adiabatic and the isocurvature perturbations are correlated, even though the fluctuations of the radiation component is considered uncorrelated with that of the inflaton. We also show that both $S$ and $\cos \Delta$ depend mainly on the ratio between the dissipation coefficient $\Gamma$ and the Hubble parameter $H$ during inflation. The correlation is positive ($\cos\Delta > 0$) for strong dissipation cases where $\Gamma/H >0.2$, and is negative for weak dissipation instances where $\Gamma/H <0.2$. Moreover, $S$ and $\cos \Delta$ in this model are not independent of each other. The predicted relation between $S$ and $\cos\Delta$ is consistent with the WMAP observation. Other testable predictions are also discussed.Comment: 18 pages using revtex4, accepted for publication in PR

Mortality Dependence of Cu Dual Damascene Interconnects on Adjacent Segments

Electromigration experiments have been carried out on straight interconnects that have single vias at each end, and are divided into two segments by a via in the center ("dotted-I" structures). For dotted-i structures in the second metal layer (M2) and with 25µm-long segments length, failures occurred even when the product of the current density and segment length (jL) was as low as 1250A/cm, even though via terminated 25µm-long lines are "immortal" when (jL)cr < 1500 A/cm. Moreover, we found the mortalities of the dotted-I segments to be dependent on the current density and current direction in the adjacent segment. These result suggest that there is not a definite value of jL product that defines true immortality in individual segments that are part of an interconnect tree, and that the critical value of jL for Cu dual damascene segments is dependent on the magnitude and direction of current flow in adjacent segments. Therefore, (jL)cr values determined in two-terminal via-terminated lines cannot be directly applied to interconnects with branched segments, but rather the magnitude as well as the direction of the current flow in the adjoining segments must be taken into consideration in determining the immortality of interconnect segments.Singapore-MIT Alliance (SMA

The Influence of Adjacent Segment on the Reliability of Cu Dual Damascene Interconnects

Three terminal âdotted-I’ interconnect structures, with vias at both ends and an additional via in the middle, were tested under various test conditions. Mortalities (failures) were found in right segments with jL value as low as 1250 A/cm, and the mortality of a dotted-I segment is dependent on the direction and magnitude of the current in the adjacent segment. Some mortalities were also found in the right segments under a test condition where no failure was expected. Cu extrusion along the delaminated Cu/Si₃N₄ interface near the central via region was believed to cause the unexpected failures. From the time-to-failure (TTF), it is possible to quantify the Cu/Si₃N₄ interfacial strength and bonding energy. Hence, the demonstrated test methodology can be used to investigate the integrity of the Cu dual damascene processes. As conventionally determined critical jL values in two-terminal via-terminated lines cannot be directly applied to interconnects with branched segments, this also serves as a good methodology to identify the critical effective jL values for immortality.Singapore-MIT Alliance (SMA

General techniques for constrained motion planning

This report presents automatic motion planning algorithms for robotic manipulators performing a variety of tasks. Given a task and a robot manipulator equipped with a tool in its hand, the motion planners compute robot motions to complete the task while respecting manipulator kinematic constraints and avoiding collisions with objects in the robot`s work space. To handle the high complexity of the motion planning problem, a sophisticated search strategy called SANDROS is developed and used to solve many variations of the motion planning problem. To facilitate systematic development of motion planning algorithms, robotic tasks are classified into three categories according to the dimension of the manifold the robot tool has to travel: visit-point (0 dimensional), trace-curve (1 dimensional) and cover-surface (2 dimensional) tasks. The motion planner for a particular dimension is used as a sub-module by the motion planner for the next-higher dimension. This hierarchy of motion planners has led to a set of compact and systematic algorithms that can plan robot motions for many types of robotic operations. In addition, an algorithm is developed that determines the optimal robot-base configuration for minimum cycle time. The SANDROS search paradigm is complete in that it finds a solution path if one exists, up to a user specified resolution. Although its worst-case time complexity is exponential in the degrees of freedom of the manipulator, its average performance is commensurate with the complexity of the solution path. Since solution paths for most of motion planning problems consist of a few monotone segments, the motion planners based on SANDROS search strategy show approximately two-orders of magnitude improvements over existing complete algorithms

Cosmological Imprints of Pre-Inflationary Particles

We study some of the cosmological imprints of pre-inflationary particles. We show that each such particle provides a seed for a spherically symmetric cosmic defect. The profile of this cosmic defect is fixed and its magnitude is linear in a single parameter that is determined by the mass of the pre-inflationary particle. We study the CMB and peculiar velocity imprints of this cosmic defect and suggest that it could explain some of the large scale cosmological anomalies.Comment: 31 pages, 7 figure

Dark energy and dark matter from an inhomogeneous dilaton

A cosmological scenario is proposed where the dark matter (DM) and dark energy (DE) of the universe are two simultaneous manifestations of an inhomogenous dilaton. The equation of state of the field is scale-dependent and pressureless at galactic and larger scales and it has negative pressure as a DE at very large scales. The dilaton drives an inflationary phase followed by a kinetic energy-dominated one, as in the "quintessential inflation" model introduced by Peebles & Vilenkin, and soon after the end of inflation particle production seeds the first inhomogeneities that lead to galaxy formation. The dilaton is trapped near the minimum of the potential where it oscillates like a massive field, and the excess of kinetic energy is dissipated via the mechanism of "gravitational cooling" first introduced by Seidel & Suen. The inhomogeneities therefore behave like solitonic oscillations around the minimum of the potential, known as "oscillatons", that we propose account for most DM in galaxies. Those regions where the dilaton does not transform enough kinetic energy into reheating or carry an excess of it from regions that have cooled, evolve to the tail of the potential as DE, driving the acceleration of the universe.Comment: 9 pages, 8 figures, uses revtex, submitted PR

Assessment of Financial Risk Prediction Models with Multi-criteria Decision Making Methods

A wide range of classification models have been explored for financial risk prediction, but conclusions on which technique behaves better may vary when different performance evaluation measures are employed. Accordingly, this paper proposes the use of multiple criteria decision making tools in order to give a ranking of algorithms. More specifically, the selection of the most appropriate credit risk prediction method is here modeled as a multi-criteria decision making problem that involves a number of performance measures (criteria) and classification techniques (alternatives). An empirical study is carried out to evaluate the performance of ten algorithms over six real-life credit risk data sets. The results reveal that the use of a unique performance measure may lead to unreliable conclusions, whereas this situation can be overcome by the application of multi-criteria decision making techniques

Characteristics of Cosmic Time

The nature of cosmic time is illuminated using Hamilton-Jacobi theory for general relativity. For problems of interest to cosmology, one may solve for the phase of the wavefunctional by using a line integral in superspace. Each contour of integration corresponds to a particular choice of time hypersurface, and each yields the same answer. In this way, one can construct a covariant formalism where all time hypersurfaces are treated on an equal footing. Using the method of characteristics, explicit solutions for an inflationary epoch with several scalar fields are given. The theoretical predictions of double inflation are compared with recent galaxy data and large angle microwave background anisotropies.Comment: 20 pages, RevTex using Latex 2.09, Submitted to Physical Review D Two figures included in fil