Association of Asia Pacific Physical Societies

Hadron mass spectrum in quenched QCD [See Fig. 3, p. 14].. " for the discovery of asymptotic freedom in the theory of the strong interaction " 2 We know of two fundamental forces on the macroscopic scale that we experience in daily life: the gravitational force that binds our solar system together and keeps us on earth, and the electromagnetic force between electrically charged objects. Both are mediated over a distance and the force is proportional to the inverse square of the distance between the objects. the photoelectric effect) presented his General Theory of Rela-tivity for the gravitational force, which generalized Newton's theory. Einstein's theory is perhaps the greatest achievement in the history of science and the most celebrated one. The laws for the electromagnetic force were formulated by James Clark Maxwell in 1873, also a great leap forward in human endeavour. With the advent of quantum mechanics in the first decades of the 20th century it was realized that the electromagnetic field, including light, is quantized and can be seen as a stream of particles, photons. In this picture, the electromagnetic force can be thought of as a bombardment of photons, as when one object is thrown to another to transmit a force. In a similar way the gravitational force is believed to be transmitted by particles called gravitons, but since the gravitational force is some 10 40 times weaker than the electromagnetic force, they have not yet been detected. The electromagnetic force holds the atom together since the nucleus and the electrons carry electric charges. The composition of the nucleus was, however, not understood in the early days of the quantum era, but there was a common belief that it consisted of protons and electrons. In 1932 James Chadwick (Nobel Prize, 1935) discovered electrically neutral radiation from the nucleus and could establish that it consisted of a new type of elementary particle called the neutron. Two years later, Eugene Wigner (Nobel Prize, 1963) showed that there must be two distinct nuclear forces at play within the nucleus, a weak force that is responsible for the radioactivity and a strong one that binds the protons and the neutrons together. Both of them act only over a very short range, of the size of the nucleus, hence they have no macroscopic analogue. Only a year after Wigner's work, the young Japa-nese student Hideki Yukawa (Nobel Prize, 1949) proposed that the …