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| SCG Projects |
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| Nanoscale Electronic
Structure Calculations Electronic structure computational nanoscience provides a unique challenge since the nanosystems typically contain from a few thousand to a few million atoms. We have developed special methods just for such problem. One method is based on empirical pseudopotentials, where the single particle Hamiltonian is constructed nonselfconsistently, and the thousand atom Schrodinger's equation is solved using a special folded spectrum method. Another approach is the charge patching method where the charge density of a given nanosystem is constructed from charge motifs generated from small prototype systems. More details can be here. |
| Early Universe Phase
Transition Dynamics The evolution of quantum field theories in expanding space-time backgrounds is fundamental to early universe cosmology. In particular, their behaviour during the symmetry-breaking phase transitions which are believed to occur at the Planck scale, the GUT scale and the electroweak scale, underlies cosmological phenomena from inflation to baryogenesis, and provides essential clues to physics beyond the Standard Model. An example of this work is the formation and evolution of semilocal strings. |
| Cosmic Microwave Background
Data Analysis The Cosmic Microwave Background (CMB) gives us a snapshot of the Universe as it was only 300,000 years after the Big Bang. The earliest possible photon-image we can ever obtain, the CMB provides a unique imprint of primordial physics through the tiny anisotropies in its temperature and polarization. However, extracting these microKelvin fluctuations from inherently noisy data is a serious computational challenge. The MADCAP software package has been developed to meet this challenge, and successfully applied to data from the BOOMERanG and MAXIMA balloon experiments. |
| Single-particle
Cryo-electron Microscopy Estimating the three-dimensional electron density map of a macromolecule (e.g., a protein complex or virus) plays an important role in biological research. The recent advances in electron microscopy (EM) imaging techniques have made it possible to reconstruct a high resolution 3-D molecular structure by merging a large number of 2-D EM images of isolated (single) particles with random (unknown) orientations. We formulated the reconstruction problem as a large-scale nonlinear optimization problem, and are currently involved in the design and implementation of more efficient and stable numerical algorithms for solving such a problem. |
| The DOE ACTS Collection The DOE Advanced CompuTational Software (ACTS) Collection is a set of DOE-developed software tools, sometimes in collaboration with other funding agencies (DARPA, NSF), that make it easier for programmers to write high performance scientific applications for parallel computers. It aims at accelerating the adoption and use of advanced computing by DOE programs as well as non-DOE computational efforts. |
| Numerical Linear Algebra The sparse linear systems and eigen systems are at the heart of many scientific and engineering applications. The group is actively pursuing research and development of scalable algorithms and solvers for large-scale systems. Examples of work in this area include the parallel sparse direct solver SuperLU, and eigensolvers that target applications in linear accelerator design and nanostructure calculations. Part this research is carried out in the framerwork of the DOE SciDAC Program. |
| High Precision
Floating
Point
Algorithms and Software Multiprecision computation (precisions higher than double) has a variety of application areas, such as numerical linear algebra algorithms for ill-conditioned problems, pure mathematics, cryptography, and computational geometry (e.g., mesh generation). High precision arithmetic is not usually supported by hardware and therefore needs to be "simulated" by software. The examples of work in this area are the Extended and Mixed Precision BLAS and the multiprecision software ARPREC. |
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