On ultra- dense hydrogen:

Chapter (almost) closed. A peer reviewed comment (November, 2023) by Klavs Hansen and Jos Engelen published here.

A peer reviewed published comment (July 24, 2023) by Klavs Hansen and Jos Engelen: here.

Note (Update May 3, 2023). I started questioning the validity of the papers on Ultradense Hydrogen over a year ago, soon joined by Klavs Hansen who had pointed out some of the flaws in them earlier. The papers are manifesly wrong (or in the category 'not even wrong' if you will) but it appeared to be very hard to get our criticism published. Finally we are now getting some cooperative response of a couple of journals, so we may be able to close this chapter soon, and archive this webpage.

On ultra-dense hydrogen as a medium for 'spontaneous' appearance of antiprotons and their subsequent annihilation.
This article was the reason for this letter to the editors of nine scientific journals. Their 'peer review' puzzles me. If you want to contribute to the discussion, please contact me at the e-mail address above.

I received the following reaction by the author of the article referred to above, you can read it here.

@HansDeVriesNL pointed me at this comment on claims of the observation of ultradense hydrogen. (That could have settled the issue. It did not.) A rebuttal was rejected by the journal, but was placed on ArXiv and can be found here .

A careful, responsible, well balanced and very critical 'editorial' on Holmlid's papers on Rydberg matter appeared in 2007, several years before the claims on Ultra-dense Hydrogen were published. Here is the editorial: Tim Softley: Editorial for whichever issue of Molecular Physics includes TMPH 219660, the paper by Professor Leif Holmlid. The text can be found here .

On the official website of the University of Gothenburg the claims on discovery and properties of ultra-dense hydrogen have meanwhile (January 1, 2024) been removed. The following information is therefore now obsolete, it will be removed from this website soon.
We have studied Rydberg Matter formed by hydrogen atoms in detail, and discovered both dense (metallic) and ultra-dense hydrogen H(0). This latter material is the most stable material that exists in the Universe. It has bond distances in its molecules of a few picometers. Despite this, it is easy to start nuclear reactions in it by for example laser impact, and energy generation above break-even was published in 2015. The nuclear processes generate mesons (kaons and pions) and a large number of muons in each pulse. An intense muon generator working on this principle has been patented. This is the base for building reactors of the muon-catalyzed fusion type. Technical development is now done in a company which is partly owned by me and partly by GU Ventures. We plan to have the first reactor in operation in two years.
For your own judgement: https://www.gu.se/en/about/find-staff/leifholmlid (removed per Jan.1, 2024).

I, JE, am absolutely sure that there is no experimental basis for the very far reaching claims of spectacular new physics made in these publications. No wonder there is no independent confirmation of all this, contrary to suggestions in the papers referred to above. Most spectacular claim: ultra-dense hydrogen can be easily produced through 'standard' heterogenous catalysis. Upon 'tickling' it with a normal laser it spontaneously produces antiprotons, these annihilate with protons and produce net energy! The issue is not that the author is convinced this is true, the issue is that a great many papers with these and similar claims got published in the peer reviewed literature. (Several of the crucial 'seminal' papers are not Open Access, I could not get hold of them yet.)

Added as 'supplementary material' to one of the papers (a review paper in fact)is this movie without any further explanation??? This review paper, by the way, could very well serve as a starting point for unraveling what happened and what led to the extreme and untenable claims of antiproton annihilation in ultra-dense hydrogen.
It says:Most of this research has been done by researchers at Gothenburg University, Sweden. It has been replicated and verified by researchers in Norway and Iceland.
This is not supported by references. It is not true!

L. Holmlid, S. Olafsson, Decay of muons generated by laser-induced processes in ultra-dense hydrogen H(0), Heliyon, can be read here or downloaded here . Published in a peer reviewed Elsevier journal. The article explains the data as being due to the reaction proton-proton (at rest) gives 3 kaons plus energy (difference of 2 proton masses and 3 kaon masses). The fact that baryon number is violated as well as strangeness conservation is not even mentioned. What is happening here? It is quite a shock to read this paper. It is founded on an illusory world only existing in the minds of the authors. There are many more (at least tens, more likely 50) of such peer reviewed papers that are nonsense from the first to the last phrase. The journals should at least acknowledge they made a mistake. The University of Gothenburg and the University of Iceland should distance themselves from the nonsense advertised on their web-pages.

The story continues: another 'recycled' article on muon catalyzed fusion, based on a non-existing, unphysical muon source, as recent as February 2022. In this earlier publication the author implicitly explicitly admits that NO muons are observed!!! But also that he completely disregarded any radiation safety measures, that he should have taken if his muon source were real! And what is written about kaons etc. is complete nonsense... If a beam of charged kaons is 'lethal' to the personnel in the laboratory, a beam of neutral kaons is equally lethal. University of Gothenburg, allowing this on your webpages has nothing to do with academic freedom! Take your academic responsibility! We quote:
IV.D. Radiation Damage on Biological Systems from the Muon Source
From the collected evidence discussed above and in previous studies, we argue that the particles emitted into the laboratory environment by the muon source are not mainly charged kaons which would give dangerous, maybe even lethal radiation levels (emphasis added by JE) to the personnel in the laboratory. The radiation in our laboratory has been checked by hand-held G-M counters (mainly Mirion RDS-80) close to the muon source, and no dangerous radiation levels have been observed. Of course, the G-M device response is limited to one count per laser shot so the real intensity may be higher. The sensitivity of this type of device is otherwise high enough to easily observe random radioactive decay in antireflective coatings on optical parts like lenses and windows. Instead of charged kaons, mainly neutral kaons seem to pass out into the laboratory, and the interaction of such particles with matter is believed to give considerably lower radiation levels, maybe mainly due to their longer decay times which allow them to move further before decay, thus depositing much of their energy in the building walls and in the laboratory equipment. They will also have a smaller direct Coulomb interaction with atoms in materials. Further, more energy is given off by gamma radiation from neutral kaon and pion decay, also distributing the radiation energy over a larger volume of materials. Certainly, more radiation research is required to give secure conclusions on this point. Another important factor is that the muon-matter and kaon-matter interactions are not well known. We have observed and studied a dominating pair-production interaction mechanism which is not yet understood completely (paper submitted) and which is not included in the radiation generating mechanisms normally considered for muons, pions, and kaons. First experimental results are published in Refs. 32, 33, and 43.

End quote. A reference to the patented muon source is here: L. HOLMLID, “Apparatus for Generating Muons with Intended Use in a Fusion Reactor,” Swedish Patent Application 1651504-1, Submitted November 11, 2016, Patent number SE 539684 C 2, Published October 10, 2017.
It can also be found here . Note the lack of detail on two crucial elements: the coil and the foil for detecting the muons that are claimed to be produced (which would represent a scientific revolution).