does diffuse cosmic background radiation in the visible betray its resolution?

A widely recognized theory of dark matter particles could explain an anomaly in cosmic radiation discovered a few years ago by the New Horizons probe. These dark matter particles, the axions, would be unstable and eventually turn into light.

Many, no doubt, are those who have heard of Cosmic microwave background (CMB) probably better known in French under the name “Fond diffusediffuse cosmological” or simply fossil radiation. Those who have heard of Diffuse Fund infraredinfrared (Cosmic infrared background) or CIB are probably as rare as those who also know the diffuse background in the visible, i.e. Cosmic optical background.

COB, like CIB, is an unresolved superposition of all stars and distributions of matter observed in a band of wavelengthwavelength. It is a kind of background noise in the visible sky that would remain if we turned off all sources of lightlight in The Milky WayThe Milky Way. It therefore comes from all sources outside ours GalaxyGalaxy — by the way, the extragalactic background light is called, i.eExtragalactic backlight or EBL in English, the intensity of all the electromagnetic radiation emitted during the history ofUniverseUniverse… of cosmic radiationcosmic radiation.

COB can be estimated theoretically and even measured, which was made possible by the instruments on board the probe. new horizonsnew horizons (specifically photos provided by Lorri, the Long Range Recognition Imager) that flew past Pluto and will one day leave completely Solar systemSolar system to sail in the interstellar medium like the Voyager and Pioneer probes.

Pierre Brun is a particle physicist at Irfu and works on the border between particle physics and cosmology. He is interested in a theory that postulates the existence of a particle called “axion”, which would solve certain problems related to the breaking of symmetry in the strong interaction laws of physics. Neutral, light and interacting very weakly with matter, the axion has all the properties of being a dark matter particle. © CEA Science

A diffuse background in the visible twice as bright as predicted

Curiously, the COB is brighter than expected by a factor of 2, as an article on arXiv explained a few years ago. Of course, theorists have pondered this conundrum, and very recently an article was published in Physical review letters on this topic. José Luis Bernal, Gabriela Sato-Polito and Marc Kamionkowski, all three from Johns Hopkins University in Maryland (USA) suggest that this excess may be caused by particles of black fabricblack fabric decays into photons, more precisely avataravatar famous actionsactions.

These particles of dark matter, lotlot very easily, proposed within the framework of several theories beyond the standard model of advanced physics energiesenergieslike string theory, has come to be considered even more seriously after the many failures of experiments designed to detect heavy dark matter particles, Wimps.

The actions should form a bath of very many particles as ghostly as the cosmological neutrinos, and they should also have been formed during big bangbig bang. We know that they are very light and that they interact weakly with electromagnetic fieldelectromagnetic field. We do not know exactly what mass they have, nor with what intensity they couple to light, although we have experimental and theoretical constraints on these values.

In the hypothesis considered by the three American physicists and cosmologists, the actions that would disintegrate explainanomalyanomaly of the COB would have masses between 8 and 20 eV, which is very low when you remember that a protonproton weighs about a billion eV.

They believe they can test their theory with the measurements that will be provided, after its launch in 2025, by the mission from NasaNasa called SPHEREx (acronym of Spectrophotometer for the history of the universe, epoch of reionization and Ice Explorer).

A presentation of the SPHEREx mission. For a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Select “French”. © Nasa Jet Propulsion Laboratory


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