Chhaj lany, Dr . S. C.Tsegaye, Biru2021-12-132023-11-092021-12-132023-11-091988-06http://10.90.10.223:4000/handle/123456789/29219The path i ntegra l formalism of Quantum Hechanic s is developed from both the Lagrangian and Hamiltonian point of view. Some e xact propagators are calculated. Several stat istical mechanics p r oblems are d i scussed via a pa th integ r a l fo rmulation of the statisti cal density matrix a nd an a pplicati on to second quantized Hamilton ians using coherent states is described . The va riational technique i s considered wi th illustrative examples . A review of some selecte d recen t achievements o f the technique 1s presentedenQuantum and Statistical MechanicsThesis