IUPAP: News from the Commissions

C4: COMMISSION ON COSMIC RAYS(K.P.WENZEL)

Cosmic-ray physics, in both its dual aspects of non-accelerator particle physics and particle astronomy, is continuing to make significant contributions to our understanding of the universe.

Probably the most important contribution to particle physics in recent years has been the discovery of the phenomenon of neutrino oscillations, i.e. the transformation of a type (or flavour) of neutrinos into another. Using natural fluxes of neutrinos, these transitions have been observed, both for solar neutrinos, produced in thermonuclear reactions inside the Sun, and for atmospheric neutrinos, produced in cosmic-ray interactions in the Earth's atmosphere. The results obtained give important constraints on the neutrino masses; the average mass is determined to be larger than a lower bound of 15 milli-electronvolts (meV). Within the last year, the results on the flavour transitions have been confirmed in studies using man-made neutrinos and identified the exact mechanism. Two pioneers of neutrino detection, Ray Davis and Masatoshi Koshiba, were among the 2002 Physics Nobel Laureates.

The last decade has seen a remarkable technological breakthrough with the introduction of sophisticated imaging systems on optical telescopes, which register the Cherenkov light from air showers due to cosmic gamma rays. This has led to a new field of TeV gamma-ray astronomy. Following the initial discovery from the Crab Nebula, TeV emission from several galactic sources has been detected, most importantly from three shell-type supernova remnants (SN1006, RX J1713-3946, and Cassiopeia A). In addition, one has found strong and rapidly varying emission from two nearby blazars, thought to be galaxies with active nuclei (powered by accretion onto a central, super-massive black hole). During outbursts the power registered in the TeV region from these objects exceeds that at all other wavelengths. Full understanding of the origin of this TeV emission may be a key to finding out whether supernova remnants are indeed the sources of the bulk of the cosmic rays.
It was confidently expected that the ultrahigh-energy cosmic ray spectrum would show a cut-off around 1020 eV. (This is quite challenging to observe because the fluxes at these energies are of order of one particle per square kilometre per century.) Tens of particles above this cut-off have now been detected by the two largest aperture air shower arrays.

There are still many difficulties in explaining the origin of these highest-energy cosmic rays because there are hardly any known astrophysical objects believed to be capable of accelerating particles to these energies.

A new outer frontier of the heliosphere - that volume of space around the Sun that the solar wind plasma carves out of the interstellar medium - has been charted. Observations of energetic particles by NASA's Voyager 1, launched in 1977, suggest that Voyager 1 may have recently, at least temporarily, encountered the 'edge' - the termination shock - of the Solar System at a distance of more than 13 billion kilometres or 85 AU (astronomical units). The termination shock is where solar wind begins to merge with the interstellar gas. It is considered to be a fascinating astrophysical object and an efficient accelerator of energetic particles.

C5: COMMISSION ON LOW TEMPERATURE PHYSICS (H.FUKUYAMA)

The greatest news not only in C5 but also in various area of condensed matter physics is that the 2003 Nobel Prize in Physics has been awarded to Alexei A. Abrikosov, Vitaly L. Ginzburg and Anthony J. Leggett for their pioneering theoretical contributions to the understanding of superconductivity and superfluidity.

Ginzburg proposed with Landau the GL phenomenological theory for superconductivity several years before the microscopic theory of Bardeen, Cooper and Schrieffer (BCS). This theoretical framework called GL theory is now the basis for phenomenological description of phase transition in solids in most cases. Abrikosov found the possibility of the vortex structure in superconductors in the presence of magnetic field based on this GL theory, which is an important feature of superconductors especially in the application. Leggett developed a theory of Nuclear Magnetic Resonance (NMR) for superfluid He3 leading to the clear identification of the spin-triplet state in contrast to the singlet state considered in the original paper by BCS. The triplet superconductivity is now observed in metals also.

By now there are many examples of realization of BEC (Bose-Einstein Condensation) in atoms. Last year the 8-th in the series but a new type with spin-singlet state has been observed on Yb atoms [1], which might open ways to very precise atomic clocks and optical frequency standard on one hand and studies for possible violation of time-reversal symmetry and parity on the other hand.

Another unexpected superconductivity has been found in Co oxides with water molecules as contents, i.e. Na0.35CoO2-1.3H2O [2] with the critical temperature of about 5K. The natures of superconductivity and its mechanism are now explored both intensively and extensively in search for the possible links between hexagonal lattice structure and electronic properties.

In most known superconductors, magnetism and superconductivity have been found to be mortal enemies. The remarkably robust superconductivity of the heavy fermion metal alloy CeCu2Si2, despite having strong magnetic properties, has been a long-standing mystery to condensed matter physicists. It appears that the mystery of this cerium-copper-silicon compound has now been solved. Groups in Max Planck Institute in Dresden and University of Geneva have shown that the stability of the superconductivity in CeCu2Si2 is a result of two distinct quantum critical points that are located close to each other [3].

Turbulence in superfluid helium-4 is associated with usual classical turbulence of the normal component and with a network of quantized vortices of the superfluid component - a complicated dynamic state with frictional losses in both fractions and weak coupling between them through the mutual friction. Recent measurements [4] have demonstrated that the superfluid turbulence in helium-3 is very different from that in helium-4. Due to the high viscosity the normal component of superfluid helium-3 is for most applications immobile. Then the mutual friction damping, which drops exponentially to zero in the zero temperature limit, is found to be the most important parameter in the turbulence of the inviscid superfluid component. This may give new insight in the still persisting problem of classical turbulence.

C11-COMMISION ON PARTICLE PHYSICS AND FIELDS(V.LÜTH)

The principal goals of particle physics have been and will be precision tests of and searches for deviations from the well established theory of electroweak and strong interactions. Though this standard model has worked extremely well up to now it fails to explain particle masses and it predicts nonsensical results at energies slightly higher than currently available. A mechanism which gives mass to the particles requires the existence of a new particle, the Higgs boson. Beyond that, new concepts are being proposed: supersymmetry and string theories might not only overcome the break down of the standard model, but also lead to a unification of all fundamental interactions, including gravity.

In recent years, the most important results have come from neutrino experiments, primarily SuperKamiokande in Japan and the Sudbury Neutrino Observatory in Canada. There is clear evidence that neutrinos from several generations undergo quantum mechanical mixing and therefore neutrinos are not massless. The solar neutrino problem, i.e. the observation that only about one third of the neutrinos produced by solar fusion survive as electron-type, is now understood, both in terms of experimental observation and predictions of the model for fusion reactions at the core of the sun. Future neutrino experiments using large volumes of sea water or Antarctic ice as detectors for atmospheric or cosmological neutrinos as well as detectors placed at various distances from accelerators or reactors will further explore the nature of these elusive particles.

A couple of years ago, the discovery of CP (Charge conjugation C and Parity P) violation in neutral B mesons at KEK in Japan and at SLAC in the USA confirmed the standard model prediction. It was the first in a series of tests of interactions between quarks of different generations that can be and will be performed with growing data samples accumulated at these B Factories.

At the energy frontier, current experiments at the Tevatron Storage Ring at Fermi National Laboratory in the USA and future experiments at the Large Hadron Collider at CERN in Switzerland will further explore the properties of the top quark and search for evidence for either the Higgs boson or some other new phenomenon to overcome the breakdown of the standard model at high energies. There is now consensus among particle physicists worldwide that a linear electron-positron collider with about 0.5 TeV of center of mass energy will be required to disentangle these new phenomena. This future machine is to be built as a true world machine, perhaps using the global accelerator network concept to allow laboratories in different regions to take responsibility for the construction, operation, and maintenance

C12:COMMISSION ON NUCLEAR PHYSICS(W.T.H.VAN OERS)

Two-proton Decay

The atomic nucleus is a bound system of protons and neutrons. Due to the interplay of the strong and electromagnetic interactions, a subtle equilibrium of the number of protons and neutrons is required. Below the atomic mass number A = 40, nuclei like to have equal numbers of protons and neutrons, but above A = 40 stable nuclei will have a larger number of neutrons due to the increasing Coulomb repulsion among the protons. Starting with a stable nucleus and increasing either the number of neutrons or the number of protons will result in instability. For a slight inbalance, the nucleus will beta-decay (electrons and positrons, respectively), but for a large disequilibrium the nucleus will emit neutrons, respectively protons; for the very heavy nuclei stability may also be reached through alpha-decay. For the lighter proton rich nuclei with an odd number of protons, proton emission was observed for the first time in the 1980s. According to theoretical predictions, simultaneous two-proton emission should occur for nuclei with an even number of protons. Such a decay is only observable if sequential emission of two protons is energetically forbidden. This situation can occur for medium mass nuclei around A = 40 - 50. Simultaneous two-proton decay has recently been observed in the decay of iron-45 at two laboratories:

at GSI (Darmstadt, Germany) and at GANIL (Caen, France).
M.Pfuetzner et al., Eur.Phys.J. A14,279(2002)
J.Giovinazzo et al., Phys.Rev.Lett. 89,102501(2002)

The Quest for the Superheavy Elements

Elements heavier than uranium (with 92 protons) are not found in nature. In general, to produce elements heavier than uranium one must resort to colliding lighter nuclei to build up these elements with more than 92 protons, which subsequently tend to exhibit alpha-decay. The shell model of the nucleus reproduces the so called magic numbers of protons and neutrons for which nuclei become significantly more stable. Extending the shell model there should also exist an island of relatively more stable superheavy elements. A recent report has detailed the discovery of four atoms of the element with 115 protons at the Joint Institute for Nuclear Research (JINR). The four atoms were created by bombarding americium-243 with a beam of calcium-48 ions at an energy of 248 MeV. The relatively long lifetime observed for element 115 points to getting closer to the island of stability. In previous experiments the same experimental group also has reported evidence for elements 114 and 116. The experiment not only represents a tour-de-force in nuclear physics but also a great feat in nuclear chemistry. If confirmed independently, these results give great weight to the existence of the island of stability at the (man made) end of the periodic table.

The Spin of the Nucleon

The nucleon consists of three so called valence quarks (two 'up' quarks and a 'down' quark for the proton and the reverse for the neutron), fleetingly existing quark-antiquark pairs through creation and subsequent annihilation, and gluons responsible for the strong interaction. The nucleon carries a spin 1/2. In principle there are contributions to the spin of the nucleon from the quarks (fermions), the gluons (bosons), and the orbital angular momenta involved. The various contributions depend on the value of the Bjorken scaling variable x. Selecting kinematics that correspond to large values of x, where the valence quarks dominate, a Jefferson Laboratory experiment studied the contributions of the valence quarks to the neutron's spin. Combining these data with existing proton data, it was found that the nucleon's two like valence quarks have their spins aligned parallel to the overall nucleon spin , but the same cannot be stated for the nucleon's valence unlike quark.

X.Zheng et al., Phys.Rev.Lett., 92,012004(2004)

The Pentaquark

In nature there appear to exist only colorless three quark systems (the nucleons) and colorless quark-antiquark systems (the mesons). In principle six quark systems could also exist. However, the search for the H-particle consisting of two 'up' quarks, two 'down' quarks, and two 'strange' quarks, in a isospin 0 and spin and parity 0+ state, has so far only been able to establish upper limits. There existed a similar situation with regard to the five quark systems consisting of three quarks plus a quark-antiquark pair. However, after some 30 years of research there are now observations made in at least five different experiments of an unusual particle composed of five quarks, a 'pentaquark'. If indeed confirmed, it will be the first time that this new exotic form of matter has been observed. The discovery will have profound influence on the understanding of quark matter, in particular if it can be determined whether the five quarks are bound to each other in the same particle or whether they form a molecule made up a three quark system and a quark-antiquark system.

T.Nakano et al., AAPPS Bull. 13:2-6(2003)
S.Stepanyan et al., Phys.Rev.Lett. 91,252001(2003)
V.V.Barmin et al., Yad.Fiz. 66,1763(2003)
C.Alt et al., hep-ex/0310014

C14-COMMISSION ON PHYSICS EDUCATION

In Commission C14, the International Commission on Physics Education (ICPE), we have undertaken a revision of the book that was published some years ago: "Physics 2000, as it Enters a New Millenium." The editor is Jon Ogborn, a member of C14. The revised book, "Physics Now," is a collection of articles for non-specialists, discussing recent developments and the current state of the art in the major areas of physics as represented by the various IUPAP Commissions. Most of the Commissions have contributed updated versions of their earlier articles in "Physics 2000" on their different fields. This book is available for downloading from the following web site:

http://web.phys.ksu.edu/icpe/Publications/PhysicsNowText-A4.pdf

Later there will also be a printed book version of this publication available.

With respect to conferences on physics education there is one "What physics should we teach?" to be held in Durban, South Africa, in July 2004, and another in 2005 in New Delhi, India. The latter is called "World View of Physics Education in 2005: Focusing on Change." The first has been supported by IUPAP and the second will be discussed in the Council meeting later this year.

Professor Laurence Viennot, from Université Paris 7, has been named as the recipient of the 2003 ICPE medal, which will be presented during the Durban Conference in July 2004. Professor Viennot is an outstanding member of the international community of physics education researchers.

C19-COMMISSION ON ASTROPHYSICS(V.TRIMBLE)

Extra-solar system planets

For decades, we knew of nine planets orbiting the sun and then, in 1991, of three more small ones orbiting a single pulsar, probably produced in the supernova event that made the neutron star (pulsar), and so very different from our sort. Now there are nearly 120, orbiting other stars like the sun. Nearly all have been found because, by orbiting a common center of mass with their stars, they introduce motions of the stars back and forth along the line of sight to the systems, producing a very small, oscillatory Doppler shift of the absorption lines in the spectra of the stars. The velocities involved range downward from a couple of km/sec to 10 m/sec, a very small fraction indeed of the speed of light.

Because of this 10 m/sec observational limit and the 10-year duration of the searches, all exo-planets found this was have masses larger than that of Sature up to about 10 times that of Jupiter (1-2 times Jupiter is commonest) and orbit periods shorter than Jupiter's 12 years. Many have orbit periods of only days to months and are so close to their parent stars that we call them "hot Jupiters." Most of the host stars are relatively rich in elements heavier than hydrogen and helium, as is the sun, with 1.5 - 2.0% of their mass in oxygen, iron, magnesium, silicon, and all the rest.

These discoveries have prompted an explosionof work on formation of planetary systems and detection strategies for earth-like planets. It seems probably that many planets (including our own Neptune) migrate some distance outward (for Neptune) or inward (for the hot Jupiters) from where they formed. Some may leave completely and appear as "orphan planets" in young star clusters. There are LOTS of things we still want to know, for instance:

How do they all form, and what interactions (with dust disks, gas, and stars) cause migration?
Are the systems we see stable for the billions of year ages of their host stars?
Which of the stars (7-20% of various samples examined so far) that have "Jupiters" with orbit periods of days to years could also have earth-like planets in stable orbits in their habitable zones?
If a "Jupiter" in a one-year orbit has a moon like Europa, would there be a wet, airy surface where you might live?
How can we detect earth-mass planets? (at present only by gravitational lensing; in the future with transits and proper motions of the stars)
Will any of them much resemble earth?

Gamma ray bursters

From their discovery in 1973 until 1997, these seconds-long flashes of gamma rays coming from seemingly random places on the sky at an average rate of about one per day prompted a wide and wild range of explanations, from magnetic quakes on neutron stars and belches of white holes (or formation of black holes0 to exhaust trails from interstellar spacecraft.

The 1997 breakthrough came from the launch of an Italian X-ray satellite, BeppoSAX (intended for quite different purposes, at which it was also very good), which provided accurate positions of the X-ray tails of the gamma-ray events fast enough for optical astronomers to look there, and, after a quarter of a century, finally observe counterparts. The first of these displayed absorption lines from gas along the light of sight, indicating that it was well outside the Milky Way, and later ones, as they faded, have revealed their host galaxies with redshifts up to 4. That is, GRBs are so rare that the ones we see probe nearly the entire visible universe. All of the GRBs with optical and radio counterparts belong to one of two classes (those with durations longer than about 2 seconds) and all happened in galaxies and regions of galaxies with active star formation.

An exciting addition in 2002-03 has been the recognition that some of the closer GRBs are associated with a particular sort of supernova explosion that involves collapse of the core of very meassive stars down to rapidly rotating black holes after the stars have shed most of their outer layers in strong winds. There are now at least three good cases of association, the cleanest from March 2003 (GRB 030329). Since supernovae have been observed for several thousand years and studied intensely for decades, the association, in the words of an old mathematicians' joke, reduces the problem to one previously solved. In any case, we are apparently watching black hole formation in real time.

Gamma ray bursts are the most energetic events now occurring in the universe, involving 1044-1045 J released in a few seconds in collimated jets. Among the residual questions are

How is this beaming or jet collimation achieved?
Do the surroundings have their chemical composition significantly affected by the supernova or progenitor star?
Are similar-looking events that peak at X-ray rather than gamma-ray energies really more or less the same sort of thing physically, but with more gas around? You might think that these should be called X-ray bursters, but the name was already taken for something else, so they are called X-ray flashers, or X-ray rich GRBs

And, most important of all, what is going on in a second group of GRBs whose durations are less than 2 seconds? There are, so far, no optical counterparts or redshifts for any of these. They may be caused by pairs of neutron stars spiraling together when energy and angular momentum are drained away by gravitational radiation.

Other sorts of black holes

Astronomical entities so compact that their escape velocities must be at least as large as the speed of light are also found in binary systems with normal stars (where accretion of gas from the companion produces bright persistent X-ray sources), at the centers of quasars and other active galaxies, and even at the center of our own passive Milky Way. A current hot question is whether there is evidence for another class, with masses between the 6-15 solar masses of the stellar ones and the million to billion solar masses of the galactic nuclei ones. With the enormous creativity of nomenclature for which astronomers are world famous, we call these "intermediate mass black holes", and suspect that they may exist in some nearby galaxies and star clusters.

C20-COMMISSION ON COMPUTATIONAL PHYSICS(T.TAKADA)

GRID is expected to be a new HPC environment for simulations, since GRID provides us with computational resources just by plugging PCs in the internet. This will definitely change our styles of computations and programming. To realize such simulations, structures of codes need to be changed from SPMD (Single Program Multiple Data) to MPMD (Multiple Program Multiple Data) which are more suitable to the GRID architectures. That is, component oriented architecture by hybridizing those units is a key for it. At GGF (Global Grid Forum: http://www.ggf.org/), interfaces for grid computing have been discussed for Particle and Nuclear Physics, Astronomy, Life Science and so on. There are many activities and national projects to utilize GRID for fundamental and industrial researches such as TERAGRID (http://www.teragrid.org/), EuroGrid (http://www.eurogrid.org/), DateGrid (http://eu-datagrid.web.cern.ch/eu-datagrid/) and e-science (http://www.escience-grid.org.uk/). These projects seem to lead each simulation scheme to so called multi scale simulations in which natural phenomena are analyzed from both microscopic and macroscopic points of view. This is a present goal of computational physics.

AC.2 INTERNATIONAL COMMISSION ON GENERAL RELATIVITY AND GRAVITATION(R.WALD)

2003 was a watershed year for cosmology and for gravitational physics. In a development designated by Science magazine as "breakthrough of the year", NASA reported on the first year of operation of its satellite WMAP (Wilkinson Microwave Anisotropy Project). The cosmic microwave radiation exhibits very small variations of its temperature with angle in the sky, a signature of sound waves at the recombination epoch when the universe was just 400,000 years old. Analysis of these fluctuations,which are being measured with exquisite precision by WMAP, allows accurate estimation of basic cosmological parameters. Further refinements will come with the launch of ESA's satellite Planck in 2006.

The results, which confirm and sharpen previous high-altitude balloon measurements, mark the coming of age of cosmology as a precision science. They reveal a universe which is 13.7 billion years old, spatially flat, and comprised by 4% ordinary (baryonic) matter, 23% exotic dark matter (exact nature still unknown), and --most mysteriously--73% so-called dark energy that is uniformly distributed (i.e., not clustered with galaxies) and characterized by negative pressure, which produces a speed-up in the Hubble expansion. The speed-up of the Hubble expansion accords with evidence from observations of distant type Ia supernovae.

This picture differs radically from what would have thought credible only a decade ago, and has sent theorists scrambling for explanations, so far without notable success.

Meanwhile, progress continues toward the goal of detecting gravitational waves. Four ground-based detectors, using laser interferometry, are currently in operation. The most sensitive--LIGO, in the US, with 4km interferometer arms--is making steady progress toward approaching its initial design sensitivity, although it may not be sensitive enough to detect gravitational waves until after its upgrade in 2006. Designs are being completed for LISA, the Laser Interferometer Space Antenna, a joint project of NASA and ESA, which is set for launch in 2012.It will consist of three spacecaft in solar orbit, arranged in the form of an equilateral triangle with a baseline of 5 million km. This will routinely see gravitational waves from binary stars in our galaxy, and should be able to study the (rare) mergers of supermassive black holes in galactic nuclei. It might even discover the cosmic background of gravitational radiation, which would allow observers to probe the earliest moments of the universe's existence.