1. The strong CP needs axions - 김진의 교수 

      The current upper bound on the neutron electric dipole moment constrains the physically observable QCD vacuum angle less than 10-11. Since QCD explains a great deal of experimental data from the 100 MeV to the TeV scale, it is desirable to explain this smallness of the angle in the QCD framework. This strong CP invariance needs an axion(s) since the other possible solutions such as the calculable models and the massless up quark possibility are ruled out. The acceptable axion is the so-called invisible axion with lifetime around 1040 years. A remarkable property of the axion is that it is not invisible permanently to us human but is detectable by several ingeneous methods.

2. Patterns and Waves in Living Systems - Karl van Bibber 교수

      After three decades, the axion, a hypothetical elementary particle, still represents the best solution to the Strong-CP problem, i.e. why the neutron has a vanishingly small electric dipole moment. Should the axion exist, it would be extremely light, in the range between a micro-eV and milli-eV, and possess extraordinarily feeble couplings to matter and radiation, far below the reach of conventional particle physics experiments. Remarkably, very light axions would have been produced abundantly during the Big Bang, and thus the axion also represents a well-motivated dark matter candidate. Being a pseudoscalar, like the neutral pion, the axion can couple to two photons, and as recognized by Pierre Sikivie in 1983, the axion can convert to a single real photon in an external electromagnetic field, an effect historically known as the Primakoff interaction. The coherent mixing of axions and photons in a strong magnetic field of large spatial extent provides the strategy for elegant and ultrasensitive experiments which may finally render the axion observable. This talk will review three major experimental campaigns to discover the axion by coherent axion-photon mixing: the microwave cavity search for halo dark matter axions (AMDX); a search for solar axions (CAST); and purely laboratory experiments, such as photon regeneration (“shining light through the wall”) or looking for magnetically-induced dichroism and birefringence of the vacuum. The searched-for signals are nevertheless still extremely small, and thus axion searches have proven to be a driver for the development of new detector technologies, such as quantum-limited SQUID amplifiers for the microwave cavity experiment.