The Australian National University
Australian Institute of Physics 16th Biennial Congress 2005
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Plenary Speakers

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Plenary Speakers

Professor Tony Leggett

FRS, FAPS, FAIP Department of Physics, University of Illinois at Urbana-Champaign, USA

2003 Nobel Prize winner in Physics "for pioneering contributions to the theory of superconductors and superfluids"

Anthony J. Leggett was born in London, England in March 1938. He attended Balliol College, Oxford where he majored in Literae Humaniores (classical languages and literature, philosophy and Greco-Roman history),and thereafter Merton College, Oxford where he took a second undergraduate degree in Physics. He completed a D.Phil. (Ph.D.) degree in theoretical physics under the supervision of D. terHaar. After postdoctoral research in Urbana, Kyoto and elsewhere he joined the faculty of the University of Sussex (UK) in 1967, being promoted to Reader in 1971 and to Professor in 1978. In 1983 he became John D. and Catherine T. Macarthur Professor at the University of Illinois at Urbana-Champaign, a position he currently holds. His principal research interests lie in the areas of condensed matter physics, particularly high-temperature superconductivity, glasses and ultracold atomic gases, and the foundations of quantum mechanics.

Ultracold Fermi Alkali Gases: Bose Condensation Meets Cooper Pairing

For many years, condensed-matter theorists have appreciated that Bose-Einstein condensation of diatomic molecules and Cooper pairing of degenerate fermions are in some sense opposite ends of the same continuous spectrum, and the problem of the "crossover" between these two limits has been intensively studied, in particular because of its possible connection with issues in cuprate superconductivity.

Recent experimental work on the ultracold Fermi alkali gases (6-Li and 40-K) has made it extremely plausible that this crossover actually occurs in these systems. However, both the physical conditions and the properties most easily investigated experimentally are rather different from those traditionally assumed in the theoretical literature. I review the salient properties of these new systems, and discuss the experimental results so far obtained and some of the challenges they present to theory.

Professor Karsten Danzmann

Director, Max Planck Institute for Gravitational Physics, Hannover, Germany Lead scientist for the European space-based LISA gravity wave observatory and Co-Director of the GEO ground based gravity wave detector project

Karsten Danzmann obtained his diploma and PhD from the Universität Hannover in Germany with work on plasma spectroscopy. Next he joined the Physikalische Technische Bundesanstalt (PTB) concentrating on optical precision measurements. From 1986–89 he was an Assistant Professor at Stanford University where he worked on high resolution spectroscopy. He returned to Germany in 1990 as the leader of the project for detecting gravitational waves (GW) at the Max-Planck-Institut for Quantenoptik (MPQ) in Garching. Since 1993 he is full Professor at the Universität Hannover. In 2002 he became the founding Director of the Hannover branch of the Max-Planck-Institut for Gravitationsphysik (Albert-Einstein-Institut) and devotes his time to the detection of gravitational waves with earth-based and outerspace instruments.

Gravitational Wave Detectors on the Earth and in Deep Space

Gravitational waves have been predicted more than 80 years ago by Einstein as a consequence of his Theory of General Relativity. Although gravitational waves have not yet been seen directly, their indirect influence can be observed in the binary pulsar PSR 1913+16. This binary's two neutron stars are spiralling together at just the rate predicted by gravitational radiation reaction.

Gravitational waves, once observed, promise us a radically new view of the universe.

Electromagnetic waves are incoherent superpositions of emission from individual electrons, atoms or molecules in low-density regions. But gravitational waves will tell us about the coherent motion of huge amounts of mass-energy and the vibrating, non-linear spacetime curvature itself.

Several kilometres-sized laser interferometric gravitational wave detectors have been under construction in the US and Europe over the last few years (LIGO, VIRGO, GEO600). LIGO and GEO600 have gone into operation in 2004 and VIRGO will join in the near future, forming a world-wide network of ground-based detectors to perform routine observations of gravitational waves in the high-frequency band between a few Hz and 10 kHz, aiming at sources such as coalescing binaries or supernovae.

The low-frequency band from 1 Hz down to less than a milli-Hertz is populated by waves emitted by sources as diverse as supermassive black holes at large redshifts to short period binaries in our own galaxy. This band will never be observable on the ground due to the unshieldable background of Newtonian gravity gradients on earth. This is the domain of detectors flown in space. The European Space Agenca (ESA) and NASA in the US have reached agreement on a spaceborne laser interferometric gravitational wave detector (LISA) as a collaborative ESA/NASA mission with a launch date in 2013.The technology demonstrator mission LISA Pathfinder has entered into its final Implementation Phase in October of 2004, aiming at a launch date in 2008.

Professor Joachim Ullrich

Director Max Planck Institute for Nuclear Physics, Heidelberg, Germany

Leibniz Award winner, 1999

Joachim Ullrich studied physics and geo-physics at the Johann-Wolfgang-Goethe Universität in Frankfurt. His PhD, about novel methods to detect small recoil-momenta in atomic or molecular fragmentation reactions (Recoil-Ion Momentum Spectroscopy), was awarded the Best Thesis Prize in 1988. At the BEVALAC of the LBL, Berkeley and as scientific staff member at the GSI, Darmstadt he explored energetic heavy-ion atom collisions and, later, photon interactions at the ALS, Berkeley or at DESY, Hamburg. For the development of many-particle imaging techniques, so-called "Reaction-Microscopes", he received the German Leibniz-Award in 1999. From 1997 to 2000 he held a Full Professor position at Freiburg University and was appointed Director at the Max-Planck-Institute for Nuclear Physics (MPI-K), Heidelberg in 2001. He is Honorary Professor at the University of Heidelberg since 2001, Managing Director at the MPI-K since 2002, Consultant Professor at the Shanghai Fudan University since 2003 and has published about 250 articles. His main current interest is in atomic and molecular many-particle dynamics in ultra-fast intense lasers, free electron lasers, in collisions with electrons, heavy ions and antiparticles. He is developing storage techniques, like ion-traps and sources (EBIT) as well as novel storage rings for molecular ions, heavy ions and antiprotons.

"Reaction Microscopes": The "Cloud Chambers" of Atomic and Molecular Physics

Reaction-Microscopes, developed 10 years ago in order to investigate ultra-fast electronic dynamics in ion-atom collisions[1], allow one to determine the complete vector momenta of several electrons and ions resulting from the fragmentation of atoms, molecules or clusters. In a unique combination, large solid angles close to 4π and superior momentum resolutions around a few percent of an atomic unit are typically reached in state-of-the art machines corresponding to energy resolutions of a few µeV for ions and sub-meV for electrons. Thus, these "cloud chambers" deliver precise images of the complete final-state many-particle wave function in momentum space essentially for any atomic and molecular fragmentation reaction[2]. Consequently, the technique has been tremendously expanding in recent years beyond the investigation of ion-atom collisions and was successfully used by an increasing number of groups to explore the interaction of photons, electrons, antiprotons and, most recently, of intense ultra-short lasers with atoms, molecules and clusters[3,4]. It turns out, that Reaction-Microscopes enable to follow in unprecedented detail and completeness correlated electronic and nuclear quantum dynamics on ultra-fast time scales from tens of femto- to sub-attoseconds.

In the talk the working principle of newest machines will be highlighted. Benchmark experiments will be presented in the various areas that have been explored where atoms, molecules or clusters interact with individual eV up to 100 keV photons, with singly up to highly-charged U92+ ions at eV to 200 GeV energies, with ultra-fast lasers at 1013 to 1016 W/cm2 intensities, with electrons from threshold to keV energies or with antiprotons at any velocity.

Finally, the rich future potential of the method will be envisaged ranging from the investigation of correlated electron emission from (super-conducting) solids and surfaces, the possible study of single-particle (molecule) properties of Bose-Einstein-Condensates to proton exchange (chemical) reactions at thermal energies and the possible control of ultra-fast correlated electronic motion in laser assisted reactions using few-cycle phase-controlled laser pulses or future free-electron lasers.

[1] R. Moshammer et al., Phys. Rev. Lett. 73 (1994) 3371

[2] J. Ullrich et al., J. Phys. B 30 (1997) 2917

[3] R. Dörner et al., Phys. Rep. 330 (2000) 95

[4] J. Ullrich et al., Rep. Prog. Phys. 66 (2003) 1463

Professor Graeme Pearman

AM, FAA, Chief of Sustainability Science, Monash University, Australia; formerly Chief, CSIRO Division of Atmospheric Research

CSIRO Medal, 1988 UNEP Global 500 Award, 1989

Professor Graeme Pearman obtained his degrees from the University of Western Australia where he was trained as a biologist. He joined CSIRO, in 1971 where he was Chief of the CSIRO Division of Atmospheric Research for ten years 1992–2002. He established an active research team looking at the biogeochemical cycles of climatically active trace gases.

He contributed over 150 scientific journal papers primarily on aspects of the global carbon budget. In 2003 he established the CSIRO CLIMATE program a thirteen-Division CSIRO wide research activity in climate change and variability. In 2004 he joined the Australian Climate Group and left CSIRO to start a consultancy company and to develop Sustainability Science at Monash University.

He was awarded a United Nation's Environment Program Global 500 Award in 1989 for his involvement in a national awareness program on the climate change issue. He was elected to Fellowship of the Australian Academy of Science in 1988 and to Fellowship of the Royal Society of Victoria in 1997 for his contribution to scientific knowledge.

In 1999 he was awarded the Australian Medal of the Order of Australia for his services to atmospheric science and promotion of the science of climate change to the public. In 2002 he was a finalist in Prime Minister's Environmentalist of the Year, and in 2001 he was awarded a Federation Medal in 2003.

Examples of his membership are: Past member of the National Greenhouse Science Advisory Committee; Past President of the Australia Meteorological and Oceanographic Society; Past Co-Chairman of the Science Advisory Group for the Asia Pacific Network for global change (Kobi); Past Chairman of the Joint Australian Academies Committee for Sustainability; Past Chairman of the National Committee for Sustainability (AAS); current Chairman of START International (Washington; System for Analysis, Research and Training of the IGBP, WCRP and IHDP international programs); Acting Chair of the Board of Greenfleet Australia; Deputy Chair of the ICSU Committee for Strategic Planning and Review (Paris). He currently serves on the Advisory Bodies of WWF and Environment Business Australia and Chairs the Antarctic Research Assessment Committee (Physical Sciences) of the Australian Antarctic Division.

From Physics to Policy: The Science of Climate Change Underpinning Private and Public Policy Decisions

Analyses of countries around the world demonstrate a growing need through this century for energy in response to increasing life-style expectations and population. At least for some time, these needs can be met only by a continued utilisation of fossil-fuel energy that in turn results, with current technologies, in the emission of carbon dioxide.

The accumulation of this gas in the earth's atmosphere has already changed the climate of the earth and more change is likely. In 2001, the international science community reported it is now clear that the earth warmed through the last century; most of this warming was likely due to increasing levels of greenhouse gases; the demand for energy will ensure that carbon dioxide continues to accumulate in the atmosphere and thus the climate warm through this century; and there are many observed and anticipated impacts of this warming on natural ecosystems and human activities around the world.

Since that time, the science has progressed further and here in Australia, evidence for warming, other climatic changes and impacts is growing.

So what is the solution to this apparent conflict for the future? Is it in new technologies? Is there a single response that will save the day? Or is there a demand for a new portfolio of energy production and utilisation technologies that meet the demands for the amenity that energy delivers, but does not compromise the future?

Are there economic gains to be made through early engagement in a new vision of energy futures? Can we usefully extrapolate our existing energy systems into the future? Or is the solution in behavioural change, and new expectations for economic growth and social security?

Graeme Pearman will outline some of the more recent evidence for climate change; address the issue of how much change might turn out to be "dangerous"; discuss the dynamic between a still incomplete and developing science and the perceived need for intervention and legislative action to deal with climate change; and the risks that this imposes on the operating environment of the commercial and industrial world, both through the impact of climate change itself and through the need for adaptive and mitigative responses to the issue.

He will discuss also the nature of a new paradigm for the development of policy, both private and public, that maximise delivery of these needs.

Professor Steven Chu

Lawrence Berkeley National Laboratory and Stanford University, USA

1997 Nobel Prize winner in Physics “for development of methods to cool and trap atoms with laser light”

Steven Chu is the Director of the Lawrence Berkeley National Laboratory and a Professor of Physics and Molecular and Cellular Biology at the University of California, Berkeley.

His thesis and postdoctoral work was the observation of parity non-conservation in atomic transitions. While at Bell Laboratories he and Allen Mills did the first laser spectroscopy of positronium and muonium. Chu led a group that showed how to first cool and then trap atoms with light. The "optical tweezers" trap is also widely used in biology. Other contributions include the demonstration of the magneto-optic trap, the theory of laser cooling (also by Claude Cohen-Tannoudji and Jean Dalibard), the first atomic fountain, and precision atom interferometry based on optical pulses of light. Using the optical tweezers, Chu introduced methods to simultaneously visualize and manipulate single bio-molecules in 1990. His group is also applying methods such as fluorescence energy transfer, optical tweezers and atomic force microscope methods to study the biology at the single molecule level.

Chu has been awarded numerous prizes that include co-winner of the Nobel Prize in Physics with William Phillips and Claude Cohen-Tannoudji (1997). He is a member of the National Academy of Sciences, the American Philosophical Society, the American Academy of Arts and Sciences, the Academia Sinica, and a foreign member of the Chinese Academy of Sciences and the Korean Academy of Science and Engineering.

What Can Physics Say about Life?

An increasing number of physical scientists are beginning to devote considerable attention to biological problems. As more physical/mechanistic understandings of biological systems emerge, we are beginning to develop a deeper, quantitative understanding of how biological systems work. With this understanding, we are beginning to appreciate the extraordinarily clever ways living systems have chosen to solve can be though of as essentially engineering problems. I will present examples of the engineering problems and solutions that life has taken that allow us to hear music and make proteins. Finally, if time permits, I will discuss how nature can give us insights into how we might solve the challenge of realizing a sustainable, CO2 neutral source of energy before out fossil fuel supply is depleted.

Dr Edwin Hans van Leeuwen

FAA Manager Exploration Technologies, BHP Billiton, Melbourne, Australia.

Clunies Ross National Science and Technology Award winner, 2002

Leader, development team for the FALCON airborne gravity gradiometer

Dr Edwin van Leeuwen is the Global Manager of BHP Billiton’s Exploration and Mining Technologies Group and is responsible for developing new exploration and mining technologies to ensure BHP Billiton stays at the forefront of its competitive business’s.

Dr van Leeuwen has held several senior positions with BHP Billiton managing the Advanced Systems Engineering Group, BHP’s External Research and Development Portfolio and Business Development Group. Prior to his career with BHP Billiton he spent five years working in the Australian Defence Department.

He currently serves on the Board of several international consortia involving Australia, Japan, USA, Canada, South Korea and Europe and is the international chairman of a program on Advanced Systems. He also sits on several University Boards and Research Centres in Australia.

In 2000, Dr van Leeuwen was elected a fellow of the Australian Academy of Technology Science and Engineering. In 2002 he was awarded the Centenary Medal for services to Australian Society in Research and Development and the prestigious ATSE Clunies Ross Award for his contributions to exploration geophysics.

He is also responsible for leading the team that developed the world’s first airborne gravity gradiometer system for mapping mineral and hydrocarbon structures from a light aircraft. This technology has won the team the CSIRO award for excellence in science and the Graham Sands award from the Australian Society for Exploration Geophysics.

Airborne Gravity Gradiometry Applied to Mineral and Hydrocarbon Exploration

Gravity, the most ubiquitous of all forces, is difficult to measure with the accuracy needed for both fundamental research, and for applications such as geodesy, mineral exploration, and defence. The reason is easy to understand, the variations in gravity from point to point on the earth’s surface are of the order of 10–6 of the average value of 9.81 ms–2. Even today, that is a major measurement challenge.

The instrumentalists of the late 1800s solved the problem the way all good instrumentalists approach such a problem; they turned it into a differential measurement. Thus the Eotvos gradiometer was developed that measured the difference between the gravitational attractions at two points about a meter apart. While excruciatingly slow to use (8 hours per measurement), and very sensitive to external influences (eg. temperature), this remained the standard technology for five decades.

By the 1950s, gravimeters (that measure the gravitational acceleration directly) had been developed to the point that they replaced the gravity gradiometer for most applications. However, a new need arose in the 1970s, when it was recognised that the accuracy with which a missile would hit it’s target was strongly influenced by the gravity gradient at the point of launch. This drove a new wave of research that led to an entirely new generation of gravity gradiometers.

While the gravimeter had satisfied many of the needs of mineral and petroleum explorers since 1950, it had failed almost totally in one important application; namely in airborne geophysics. Once again it is easy to understand why; the gravitational signals of interest are a factor of <10–7 of the accelerations of the aircraft and are indistinguishable from them at a point measurement.

Starting in 1991, BHP Billiton surveyed all the known gravity technologies and in particular gravity gradiometer technologies to assess the practicability of developing an operational airborne system with the sensitivity, reliability, and operating costs required by the minerals industry. The goal of the team was to determine whether BHP Billiton could achieve a competitive advantage in mineral and hydrocarbon exploration industry by building the ‘worlds first’ airborne gravity gradiometer system.

Since 1999, BHP Billiton has successfully built and deployed three airborne gravity gradiometer systems, (Newton, Einstein, and Galileo) based upon the Bell Aerospace (now Lockheed Martin) Gravity Gradient Instruments. A second-generation digital gravity gradiometer (Feynnman) is presently undergoing airborne testing. The GGI technology is based on groups of four (4) accelerometers where the accelerometers are equi-spaced on a circle with the sensing axis tangential to the circle. The configuration successfully rejects both common mode accelerations and rotations about the axis perpendicular to the plane of the complement.

The BHP Billiton AGG technology provides high quality gravity maps with a resolution and sensitivity to map gravity anomalies associated with both minerals and hydrocarbon deposits.

This paper presents an overview of the technology and technical challenges in developing an airborne gravity gradiometer by using a partially declassified military technology and the success BHP Billiton has achieved in deploying technology for the detection of mineral and hydrocarbon targets.

Dr Catherine Cesarsky

Director-General, European Southern Observatory, Garching, Germany

COSPAR Space Science Award winner, 1998

President of the International Astronomical Union, 2006

Born in France, Catherine Cesarsky graduated in Physics from the University of Buenos Aires in 1965 and obtained a Doctorate in Astronomy in 1971 from Harvard University. She then worked at the California Institute of Technology, before returning to France in 1974. She spent the major part of her career at the “Commissariat à l’Energie Atomique (CEA)”. She has been the Head of the Service d’Astrophysique from 1985 to 1993, and the Directeur des Sciences de la Matiére, responsible for all activities in basic research in physics and chemistry at CEA from 1994 to 1999. She was the Principal Investigator of the ISOCAM instrument on board of the ESA ISO satellite.

Since September 1999, Catherine Cesarsky is Director General of the European Southern Observatory (ESO) which has the La Silla Observatory, four 8m telescopes (VLT) at Monte Paranal, and is constructing in a world wide collaboration the ALMA Observatory, all in Chile.

She is a member of many national and international associations and organisations within physics, astrophysics and space sciences, as well as of Academia Europeae and of the National Academy of Sciences (USA, as foreign associate). She is the president elect of the International Astronomical Union.

A Golden Age for Astronomy

We live in a truly exceptional age of discovery in astronomy and cosmology. Revolutionary advances have taken place in our knowledge in these fields, ranging from our local galactic environment to the entire Universe. Thanks to new and powerful observational facilities, on the ground and in space, virtually every stage of evolution of the universe and its components is now within reach.

Following the discovery of the first planets outside our solar system a decade ago, well over a hundred are now known. At the other end of the scale, the large-scale properties of the Universe have been determined with astonishing precision over just the last few years. The existence of pervasive dark matter has been confirmed, and new discoveries have revealed the existence of a mysterious dark energy that dominates the expansion of the Universe. The presence of black holes in the centers of galaxies, including our own, the Milky Way, has been ascertained.

While several of the classic questions of the last century have been answered, a whole host of new and profound questions has arisen. Will we find earth-like planets, capable of sustaining life, as we know it? How do stars and planets form and how do they evolve? What are the dark matter and dark energy that comprise 96% of our Universe? The ultimate question can now begin to be addressed: What is the origin and fate of our Universe?

Professor Marcela Bilek

University of Sydney, Australia

Malcolm McIntosh Prize for Physical Scientist of the Year, 2002

Federation Fellow, 2003

Marcela Bilek was appointed Professor of Applied Physics at the University of Sydney in 2000 and awarded an ARC Federation Fellowship in 2003. She holds a PhD in Engineering from the University of Cambridge, UK, a B.Sc. in Physics from the University of Sydney and an MBA degree from the Rochester Institute of Technology, USA. Prior to her present appointment she held a visiting Professorship at the Technische Universität Hamburg-Harburg, Germany, and a Research Fellowship at Emmanuel College, University of Cambridge, UK. She also worked as a visiting Research Scientist at the Lawrence Berkeley Laboratory, University of California, USA. Aside from her academic experience, Marcela has spent time working in industry as a Research Scientist at Comalco Research Centre, Melbourne, and at the IBM Asia Pacific Group Headquarters in Tokyo, Japan. Her research focus is plasma processing for materials synthesis and surface modification. She has published over 60 referred journal articles and won a number of prizes, including the Malcolm McIntosh Prize for Physical Scientist of the Year in 2002, an MIT TR100 Young Innovator award in 2003, and the Australian Academy of Science’s Pawsey Medal in 2004.

Plasma Physics Enters the Nano-Age

Ions, the positively charged species extracted from a plasma, have an established role as the work horse of the microelectronics age. Their use as machining and fabrication tools in the microelectronics and now in the MEMs industries is well established. Ions are commonly used for deposition of thin film layers and the etching of features which make up sub micron scale devices. Because of their charge, their energies are easily controlled by the application of electric fields. With control of ion energy, it is relatively straightforward to tailor the microstructure and properties of thin films deposited from plasma sources and to control the directionality of reactive ion etching processes. Recently, research has been focused on the development of devices with features at the nanoscale. Whether ion based technologies will continue to dominate this new field is uncertain. Scale down of top-down machining methods, such as most ion based methods, is difficult, with control of the process on such a fine scale presenting the biggest problem.

The creation of nanostructures in nature occurs by bottom-up processes, such as self-assembly, where the molecular building blocks organize themselves into the final structures. Self assembly is based on the concept that a system will move under natural forces to the minimum energy state it can reach given the time and energy available to it. Control can be achieved by ensuring that the properties of the system and the nanoscale building blocks in it are such that energy minimization under the applied external constraints leads to the desired structures. An example of such an approach is the self organization, in water, of a dispersion of nanoparticles with hydrophobic and hydrophilic surfaces, produced by polymer grafting or co-polymerisation. These particles self assemble because energy minimization principles dictate that the hydrophobic parts cluster together away from the solution while the hydrophilic surfaces make contact with the solution. Structures such as spheres, rods and planes have been demonstrated depending on the ratios of hydrophobic to hydrophilic surfaces on the self-assembling nanoparticles. Plasma processing has the potential to play an important role in the production of nanoscale devices in treating or grafting the surfaces of particles or in producing substrates and templates with anchoring, control and readout functions for the devices.

This paper will review recent applications of ions extracted from plasma with controlled energy to produce structure at the nanoscale. Strategies, systems and processes to create nanoscale multilayered structures, nanocomposites and patterned surfaces will be presented. The experimental results presented show the range of structures which can be achieved and in particular the power of these methods to produce preferred crystallographic orientations and metastable phases within nanostructured materials. Plasmas can be used to control the hydrophilic/hydrophobic properties of surfaces to prepare them for interaction with molecules and particles in solution. Plasma methods to produce functional groups on surfaces for interaction with self-assembling particles and biomolecules, such as proteins and antibodies, will also be discussed.

Professor Helen Quinn

FAPS, FAAAS Stanford Linear Accelerator, USA

Dirac Prize winner, 2000

President of the American Physical Society, 2004

Helen Rhoda (Arnold) Quinn was born in Melbourne. After matriculating from Tintern CEGGS in 1959, she attended Melbourne University for two years. She emigrated to the United States in 1962 with her family, following a career opportunity for her father. She enrolled at Stanford University where she received a B.Sc. in 1963 and a Ph.D in Physics in 1967. She was a postdoctoral researcher at the Deutches Elektronen Synchrotron in Hamburg in 1968–69. Returning to the United States she had one year with no employment and then took a postdoctoral position at Harvard University, and later became Assistant and then Associate Professor. In 1976 she followed her husband back to California and to Stanford using a Sloan Foundation Fellowship to support her research for the year. She took up a staff position at Stanford Linear Accelerator Center in 1977 and in 2003 was promoted to Professor of Physics.

Her research has been recognized with a Dirac Medal from the International Center for Theoretical Physics in Trieste, Italy in 2000 and by election to both the American Academy of Arts and Sciences (1998) and the (US) National Academy of Science (2003).

Helen married Daniel Quinn in 1966. They have two children and two grandchildren.

The Asymmetry between Matter and Antimatter—in the Universe and in the Laws of Physics

A major outstanding puzzle at the intersection of particle physics and cosmology is the asymmetry between matter and antimatter. The Universe contains significant amounts of matter and an insignificant amount of antimatter. The puzzle is how this can occur when the laws of physics for matter and antimatter are very close to identical. Unless it arises from a very finely tuned initial condition that is maintained by an absolute conservation law, the matter-antimatter asymmetry of the Universe can only occur due to an asymmetry between matter and antimatter in the laws of physics. In technical terms this asymmetry in the laws of physics is known as CP violation, where C is the operation that interchanges all particles and antiparticles and P is the operation that reverses all spatial coordinate directions (mirror reflection plus rotation about an axis perpendicular to the mirror).

I will review how CP violation can arise in particle theories. In the current (extended) Standard Model of particle physics CP violation can appear in only two places, one affecting heavy quark decays and the other, which enters only after the theory is expanded to include neutrino masses, affecting heavy neutrino decays. Extensions of the theory can add additional CP violating effects. I will explain why this is so.

I will also discuss the status of experiments aimed at investigating these features of the theory in further detail. I will then discuss scenarios for the evolution of matter-antimatter asymmetry in the Universe based on each of these possibilities. In either case it seems that the current Standard Model theory must be extended in some way to give the observed Universe.