Current state of “cold” antihydrogen research

Research on the production of cold antihydrogen atoms, aimed at directly testing the CPT-invariance and the equivalence principle for antimatter, is reviewed. The properties of cold positron and electron plasmas, in particular the processes accompanying antiproton stopping, are discussed. Mechanisms for the formation of antihydrogen atoms are analyzed. The most favorable conditions for the production and confinement of cold antihydrogen atoms are appraised.