the transmission of phase information between advanced clocks (which require microgravity) over large distances through the vacuum of space, where the lack of dispersion through a medium enables highly accurate relative timing and frequency information to test Lorentz variation at unprecedented limits.

To pursue these quests, NASA should support a comprehensive program providing regular access to space, complemented by a robust ground-based program of supporting investigations, flight-definition studies, and education of the next generation of scientists. Such a balanced program will foster a broad scientific community to ensure that NASA pursues the best science, both enabled by and enabling exploration. We know that traditionally this fundamental science mission is best accomplished through peer-reviewed selection processes that are responsive to the most compelling scientific ideas of our time. Neither the overall mission program nor specific scientific projects should be dictated during peer review or at any other stage in the planning process. Instead, areas of scientific thrust are discussed below where, historically, shared facilities have either already been developed or are likely to be available in the future.

In this chapter, four scientific “thrusts” are described that define the frontier of space-based fundamental physical science. Each of these thrusts is discussed in its own section, which provides technical background as well as some typical investigations that might form the basis of an initial program. Other important areas of physical inquiry, including fluid physics, materials, and combustion, have a fundamental component as well, but because they are covered in Chapter 9 of this report, they will not be discussed here.* At the end of this chapter, the panel’s overall findings are discussed and recommendations for research in the fundamental physical sciences are provided, including statements about scientific content as well as platforms and facilities needed for success.

RESEARCH ISSUES

Thrust I: Soft-Condensed-Matter Physics and Complex Fluids

Complex fluids and soft condensed matter are materials with multiple levels of structure. That is, they are composed of objects that themselves contain many atoms or molecules. The field encompasses colloids, emulsions, foams, liquid crystals, dusty plasmas, and granular material. With large particles, slow dynamics, and controllable interactions, it is possible to use such systems as models for a wide variety of physical phenomena. Basic insights have been gained into diverse fields such as phase transitions, nucleation and growth of crystals, symmetry breaking, field theory, spinodal decomposition, and the development of the early universe, ergodicity breaking and glass formation, turbulence, and chaos. The complexity of the basic building blocks and the variety of their interactions have led to the discovery of novel phases as well as interesting processes and dynamics.

Along with their utility for studying fundamental phenomena, complex fluids/soft materials are ubiquitous in the food, chemicals, petroleum, cosmetics, pharmaceutical, liquid-crystal display, and plastics industries. Granular and fluid flow and related processes are essential to present and emerging technologies. The direct contribution of these materials and processes amount to ~5 percent of the U.S. GDP and ~30 percent of the manufacturing output of the United States alone (>$1 trillion). They also play heavily in the construction, textile, printing, and electronics industries.1

The softness of the materials may be associated with the large size of the basic units. They are easily deformed and their statics and dynamics are governed by surface tension and entropic forces. On Earth these weak forces are typically dominated by gravity. Thus microgravity is required to probe the underlying properties of these

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* Astronomy and astrophysics and fundamental physics overlap scientifically in many significant ways. This report has avoided duplication with those areas of fundamental physics (e.g., detection of gravitational waves using the Laser Interferometer Space Antenna) that have been carefully considered by the astronomy and astrophysics decadal survey in New Worlds, New Horizons in Astronomy and Astrophysics (National Research Council, The National Academies Press, Washington, D.C., 2010). Rather, this study has concentrated on experimental physics performed on small, self-contained space platforms that are typically designed and operated by small investigator teams, rather than the large observational observatories or experiments that are dealt with in New Worlds, New Horizons.

The application of ö4 field theories to understand spontaneous symmetry breaking led to research into the use of condensed matter systems to model cosmology. This has been the topic of theoretical work by Wojciech Hubert Zurek and experimental work by W.D. McCormick and others in Manchester, England. The subdiscipline is summarized in the book The Universe in a Helium Droplet by Grigory E. Volovik, The International Series of Monographs on Physics, Oxford University Press, 2003.



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