RELATIONSHIP BETWEEN MICROSCOPIC AND MACROSCOPIC INTERACTIONS IN LOW ENERGY NUCLEAR REACTIONS: Lessons Learned from D+D4He

For a long time, Cold Fusion (CF) seemed to be at odds with conventional Physics both experimentally and theoretically. A key reason for this involved confusion about the possibility that processes involving characteristic length scales of nuclearand atomicsize dimensions could couple to each other without releasing high momentum particles. As experiments have improved, this situation has changed. In the paper, we identify and contrast a number of common themes associated with the manner in which five of the more refined theories have addressed this problem.