There is now a considerable amount of experimental evidence, particualrly excess heat and also some high energy particle emission that indicates that something 'interesting' is going on.

However, one of the observations that is frequenctly made is that the progress so far is very 'Edisonian'. There is a lack of a coherent theory to explain the results and guide the experiments and so experiments proceed in a very 'trial and error' manner.

That is not to say that there have been no attempts at producing a coherent theory, indeed there have been many, but at present they are often contradictory, and clearly incomplete.

The basic problem: Doing chemistry with nuclei

In normal chemistry, the atoms of elements make and break bonds with each other, sometimes releasing energy, and sometimes requiring energy to be put into the system. The important thing is that the atoms stay unchanged. You might start with an atom of hydrogen and nickel, and thats what you finish with. Scientists measure the energy involved per atom or bond in terms of electron volts. A typical chemical reacton involves energies of a few electron volts.

Nuclear reactions such as fusion involve changing the atoms themselves, by adding things to the nucleas, or removing things from the nucleus. It turns out that some nuclei are more stable than others, and if you can make a set of nuclei that are more stable than the set you are start from, that will release energy. Lots of it. TYpically millions of electron volts per atom, or of the order than a million times more energy than you get from a chemical reaction.

The problem is that the nuclei are positively charged and repel each other. This makes it very difficult to push them together so that they make a different nuclei and release some energy It takes a lot of energy, or some very clever tricks, to overcome this barrier. In the sun fusion happens because the atoms have lots of energy because they are very hot and move very fast. Traditionally we have used the same approach of making the atoms move very fast in our attempts to use fusion as an energy source here on earth. This has proved difficult.

Howver, if we succeed, then we would end up with more energy being released as a reult of the nuclei being changed than we have put in

The promise of cold fusion has always been the possibility that there is some kind of 'back door' that allows the nuclei of atoms to be brought together to do 'chemeistry' with nuclei. The problem has been:

• We don't understand the physics well enough to use it to be able to predict the back doors to use
• If there is a system where more energy has been produced than we put in, we don't understand the physics well enough to satisfy ourselves, and particularly the sceptics, that it was because we have been fusing nuclei together to produce the energy.

Rossi publications

In 2010, Rossi and Focardi attempted to submit a paper to various journals, without success. This claims that the process is patented in 90 countries, although as yet the patent is yet to be granted. A few notable points from the paper:

• System consists of Nickel, Hydrogen and 'an additive'
• The process is that a proton is added to the Nickel nucleus, and then this decays, either by emitting a positron or by capturing an electron to form a Nickel isotope one molecular weight heigher than the original isotope.
• Both the proton capture and then the proton to neutron decay are always energetically favourable
• No neutrons or gamma rays detected
• The explanation of how the coulomb barrier is overcome and the protons are able to tunnel in suggests implies the system is in a simialr state to the "stellar gas" where the nuclei are stripped of their electrons and sit in a sea of electrons (Cauldrons in the Universe p167). They refer to a Debye and Huckel paper on the theory of electrolytes ("Historic Papers in Electrochemistry", p)

However, one paper that impressed me by the way that it attempted to establish some of underlying ground rules was "Physics of the Cold Fusion Phenomenon" by Hideo Kozima.

Smuggling protons into the nucleus by making them look like neutrons

One angle that some people are exploring is the possibility that protons could be smuggled into the nucleus by 'masking them' or making them look like neutrons by creating a temporary state which is a superposition of a proton and an electron

• A paper by Giuliano Bettini, a significant contributer to the facebook page, which builds on some ideas originally published in the journal of nuclear physics by Prof Stremmenos
• What I beleive to be the same basic idea was presented at a recent conference on coherence in Italy

Doing this provides a way of overcoming the coulomb barrier that would have repelled the proton on its own. A problem with this model is that there is no precedent for such 'masked' protons, and a better way of taking this approach is to consider the possibility that the weak nuclear force can occasional result in a proton and an electron coming together to form a real neutron that is then captured by a Nickel nucleus.

A possible role of resonance

Another way of approaching the problem is consider ways in which the protons or hydrogen nuclei might end up coincident to a Nickel nucleus. Some key evidence that may help identify what is going on is the following:

• It is frequently found that LENR only happens when the number of protons in the metal lattice are close to the number of metal atoms, which will result in significant regions where there is a very regular metal/proton lattice

Proton pairing

One possibility that has been raised is that protons may pair up, much like the cooper pairs in superconductors.

There have been a few papers in the physics archive, including:

• A detailed analysis of the formation of cooper pairs, showing that the binding energy is of the order of 1eV, which should be measureable using calorimetry
• A paper in the Physics archive showing how such pairs could support a mechanism by which protons are able to tunnel into the nucleus of other atoms.

Water explosions

http://www.eskimo.com/~billb/amateur/capexpt.html

http://www.lenr-canr.org/acrobat/ZhangXontheexplo.pdf