“high-end capability computing,” or HECC, as shorthand for this nonroutine frontier of computation, the precise definition of which will vary by field.

While this study does identify the potential impact of HECC in these four fields, and thus implicitly identifies some potential funding opportunities, that is not the goal, and this study is no substitute for competitive review of specific proposals. Rather, the study is meant to illustrate the sort of examination that any field or federal agency could undertake in order to analyze the HECC infrastructure it needs to support progress toward its research goals, within the context of other means of pursuing those goals.

SUMMARY OF THE MAJOR CHALLENGES IN THE FOUR FIELDS

Astrophysics

A small sample of some of the most important discoveries in astrophysics made in the past decade includes dark matter and dark energy, exosolar planets, and good evidence for the existence of black holes. These discoveries have positioned the field to address the following major challenges:

  1. What is dark matter?

  2. What is the nature of dark energy?

  3. How did galaxies, quasars, and supermassive black holes form from the initial conditions in the early Universe observed by the Wilkinson Microwave Anisotropy Probe (WMAP) and the Cosmic Backround Explorer (COBE), and how have they evolved since then?

  4. How do stars and planets form, and how do they evolve?

  5. What is the mechanism for supernovae and gamma-ray bursts, the most energetic events in the known Universe?

  6. Can we predict what the Universe will look like when observed in gravitational waves?

To answer the questions posed by Challenges 3-6, advances in HECC are necessary. Challenges 1-2 are limited in the near term by the need for advanced astronomical observations, but these observations will produce so much data that HECC will in any case be needed for their analysis. The current situation for these challenges is described in Chapter 2.

While astrophysics is a computationally mature discipline—that is, it has a long history in the use of computing to solve problems—it would certainly benefit from access to more, and more powerful, HECC resources. The primary computational challenge is associated with the enormous dynamic range in length scales and timescales needed to resolve astrophysical processes. For example, grids as large as 20483 are currently used for calculations involving hydrodynamics, but even then the spatial features they are able to resolve are only about a hundredth the size of the computational domain. The availability of systems of 105 or more processors will enable much larger calculations (encompassing finer resolution, models of more physical processes, or both) while also making it feasible to perform more complex calculations that couple different models. The community needs support for porting its codes to multicore and petascale environments.

The committee identified some likely ramifications of inadequate or delayed support of HECC for astrophysics:

  • The rate of new discovery would be limited.

  • Inadequate support for HECC would lead to a failure to optimize investment in expensive experimental and observational facilities.



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