41. Because of the gauge invariance of general relativity, the correct formulation of cosmological perturbation theory is subtle. 42. SSA perturbation theory is developed in Nekrutkin ( 2010 ) and Hassani et al . ( 2011 ). 43. Asymptotic analysis ( perturbation theory ) is widely used in the modern applied mathematics, mechanics and physics. 44. Perturbation theory at the level of the random phase approximation captures many of the properties of composite fermions.45. :: : : You can exactly work out the case of two Hydrogen atoms in perturbation theory . 46. The interaction of strings is most straightforwardly defined by generalizing the perturbation theory used in ordinary quantum field theory. 47. This equation can be solved using ordinary perturbation theory in the same way as regular expansion for was obtained. 48. Renormalization was first developed in quantum electrodynamics ( QED ) to make sense of infinite integrals in perturbation theory . 49. Singular perturbation theory is a rich and ongoing area of exploration for mathematicians, physicists, and other researchers. 50. But standard perturbation theory techniques don't work at distances, where the running coupling constant reaches 1.
