# Widom-Larsen part 1: Overview

The Widom-Larson theory of cold fusion started with this paper:

“Ultra Low Momentum Neutron Catalyzed Nuclear Reactions on Metallic Hydride Surfaces” by A. Widom, L. Larsen, 2005.

A follow-up paper with more mathematical details is here, while a follow-up with slightly more qualitative discussion is here.

This is apparently the most popular theoretical explanation of cold fusion. For example, it was the theoretical justification supporting NASA’s cold-fusion program. Apparently, lots of reasonable people are convinced by it.

On the other hand, we have things like Ron Maimon’s post railing against the theory (“…a bunch of words strung together with no coherent relation to known weak interaction theory, or to energy conservation, or to surface theory of metals, or to known nuclear physics of neutrons…”), a critical paper by Tennfors (with a 4-sentence reply here at newenergytimes), and this paper by Hagelstein that suggested that the Widom-Larsen calculation is wrong by 17 orders of magnitude, which then solicited this angry and sarcastic response by Widom et al., and this critical paper by Vysotskii, and another critical paper by Hagelstein…

(Lots more papers related to Widom Larsen theory, both for and against it, are listed here at newenergytimes.com.)

I want to get to the bottom of this. If Widom-Larsen theory is right, I want to clearly explain and justify every detail. If it’s wrong, I want to understand all the mistakes, what the authors were thinking, and how they got led astray. There is a lot of ground to cover. It will take many blog posts. Let’s get started!

Very quick summary: The paper makes two claims:

• The electron-capture process $e^- + p^+ \rightarrow n + \nu_e$ (electron plus proton turns into neutron plus electron neutrino) can and does happen on the palladium hydride surface. (Discussed in Sections 1-3 of the paper.)
• The neutrons can enable a variety of nuclear reactions which indirectly turns deuteriums into helium-4: $D+D + \cdots \rightarrow \cdots \rightarrow \text{He}^4 + \cdots$. (Discussed in Section 4 of the paper.)