Proposing New Particles

[lpetrich]

Exponential expansion brings to mind the old steady-state cosmology, which also featured exponential expansion. Inflation also has a curious analogy with SS.

SS never had a good account of the origin of matter. The most that its advocates could think of was a mysterious C-field that makes neutrons.

But inflation produces something vaguely similar, but something with much more physical motivation. Primordial density fluctuations.

Evidence of PDF's first came from clusters of galaxies, where they account for how these structures got started. But that is not very strong evidence, and much stronger evidence appeared in the cosmic microwave background. CMB photons were released from their surrounding matter when its ionization ended as it cooled below about 3000 K, making the Universe much more transparent to visible light. But that "recombination" event happened about 300,000 years into the Universe's expansion -- and about 14 billion years ago.

That means that there was far too little time for CMB fluctuations to have formed. Or was there?

According to inflationary cosmology, quantum fluctuations would get frozen into the Universe's space-time as it expanded, because once a fluctuation got stretched to the size of the Universe's event horizon, it became too hard to communicate across its size. So the Universe would make quantum fluctuations that would then get baked into it, fluctuations that would later make their imprint on the CMB and would later start the formation of galaxies and clusters of galaxies.

From the sizes of primordial fluctuations one can estimate the expansion rate of the inflationary phase, and from that, the inflaton's energy scale as it powered that inflation. One finds about 10^(15) GeV, close to GUT energies.

Inflation did not last forever, of course, or we wouldn't be able to exist. The inflaton's field energy must have gone into making lots of other particles, but the details of this reheating are still obscure.


So from cosmology, we find three particles -- dark matter, dark energy, and the inflaton -- particles with no clear nongravitational evidence of their existence.

 

[Jimmy Higgins]

Scientists discover third....ish particle type.

First there were bosons. Then there were fermions. Now there are anyons... well kind of... if you make conditions just right.

Bosons are the liberal hippy of particles. Their vegan diet causes them to not have mass, and they are fine with communal living and all occupying the same spot without making a big deal of it.

Fermions are the libertarians of particles. Their primary focus is their property and the insistence that if they occupy a space, no one else can. Being meat eaters, these particles also have mass.

Some scientists want to figure out if they could prove anyons exist and somehow use them in quantum computing because.... umm... science that is absurdly over my head.

MIT physicist Frank Wilczek, who predicted and named anyons in the early 1980s, credits the first paper as the discovery but says the second lets the quasiparticles shine. “It’s gorgeous work that makes the field blossom,” he says. Anyons aren’t like ordinary elementary particles; scientists will never be able to isolate one from the system where it forms. They’re quasiparticles, which means they have measurable properties like a particle — such as a location, maybe even a mass — but they’re only observable as a result of the collective behavior of other, conventional particles. (Think of the intricate geometric shapes made by group behavior in nature, such as flocks of birds flying in formation or schools of fish swimming as one.)