Astroparticle Physics

306 16 GlossaryA Friedmann–Lemaître model of the universe with positive curva-ture of space. Such a universe will eventually contract leading to aBig Crunch.Cherenkov effectclosed universecluster of galaxiesCMBCOBEcold dark mattercollidercolourcolour chargecompactificationCOMPTELCompton effectconfinementCherenkov radiation occurs, if the velocity of a charged particle ina medium with index of refraction n exceeds the velocity of lightc/n in that medium.A set of galaxies containing from a few tens to several thousandmember galaxies, which are all gravitationally bound together. TheVirgo cluster includes 2500 galaxies.Cosmic microwave background, see cosmic background radiation.Cosmic Background Explorer. Satellite with which the minute temperatureinhomogeneities ( TT ≈ 10 −5 ) of the cosmic backgroundradiation were first discovered.Type of dark matter that was moving at much less than the ve-locity of light some time after the Big Bang. It could consist ofWeakly Interacting Massive Particles (WIMPs, such as supersymmetricparticles) or axions.An accelerator in which two counter-rotating beams are steeredtogether to provide a high-energy collision between the particlesfrom one beam with those of the other.The strong ‘charge’ of quarks and gluons is called colour.The quantum number that determines the participation of hadronsin strong interactions. Quarks and gluons carry non-zero colourcharges.The universe may have extra dimensions. In string theories thereare 10 or more dimensions. Since our world appears to have onlythree plus one dimension, it is assumed that the extra dimensionsare curled up into sizes so small that one can hardly detect themdirectly, which means they are compactified.Compton telescope on board the CGRO satellite.Compton effect is the scattering of a photon off a free electron. Thescattering off atomic electrons can be considered as pure Comptoneffect, if the binding energy of the electrons is small compared tothe energy of the incident photon.The property of strong interactions, which says that quarks andgluons can never be observed as single free objects, but only insidecolour-neutral objects.