The nature of dark matter continues to perplex astronomers. As the search for dark matter particles continues to turn up nothing, it’s tempting to throw out the dark matter model altogether, but indirect evidence for the stuff continues to be strong. So what is it? One team has an idea, and they’ve published the results of their first search.
The conditions of dark matter mean that it can’t be regular matter. Regular matter (atoms, molecules, and the like) easily absorbs and emits light. Even if dark matter were clouds of molecules so cold they emitted almost no light, they would still be visible by the light they absorb. They would appear like dark nebula commonly seen near the galactic plane. But there aren’t nearly enough of them to account for the effects of dark matter we observe. We’ve also ruled out neutrinos. They don’t interact strongly with light, but neutrinos are a form of “hot” dark matter since neutrinos move at nearly the speed of light. We know that most dark matter must be sluggish, and therefore “cold.” So if dark matter is out there, it must be something else.
In this latest work, the authors argue that dark matter could be made of particles known as scalar bosons. All known matter can be placed in two large categories known as fermions and bosons. Which category a particle is in depends on a quantum property known as spin. Fermions such as electrons and quarks have fractional spin such as 1/2 or 3/2. Bosons such as photons have an integer spin such as 1 or 0. Any particle with a spin of 0 is a scalar boson.
Quarks and leptons are fermions, while force carriers are bosons. Credit: Fermilab
While it seems like a trivial distinction, the two kinds of particles behave very differently when brought together in large groups. Fermions can never occupy the same quantum state, so when you try to squeeze them together, they push back. This is why white dwarfs and neutron stars exist. Gravity tries to push electrons or neutrons together, but the Fermi pressure is so strong it can resist gravity (up to a point). Bosons, on the other hand, are perfectly happy occupying the same state. So if you supercool a bunch of bosons (such as helium-4) they can settle into a strange quantum object known as a Bose-Einstein condensate.
The only known scalar boson is the Higgs boson. The Higgs can’t be dark matter given its known properties, but some theories propose other scalar bosons. These would not interact strongly with light, only with gravity. Since light can’t significantly heat them up, over time these scalar bosons would cool and collapse into large clouds. So perhaps dark matter is made of large diffuse clouds of scalar bosons.
Illustration of a quark core in a neutron star. Credit: Jyrki Hokkanen, CSC – IT Center for Science
It’s an interesting idea, but how could you prove it? It turns out that since scalar bosons interact gravitationally, they also interact with gravitational waves. Depending on their mass, scalar bosons might also decay by emitting gravitons. As a result, scalar bosons could create long-lasting gravitational waves that have a similar frequency. It’s the gravitational equivalent of a faint hum. So the team looked at gravitational wave data from LIGO and Virgo. They looked for evidence of a gravitational hum in the 20 – 600 Hz range and found nothing. Based on their work, the authors conclude that there are no young scalar boson clouds in our galaxy. There are also no old and cold scalar boson clouds within 3,000 light-years of Earth.
This study doesn’t rule out scalar bosons completely, but it does put some strong limits on the idea. And right now that seems to be the story of dark matter. In our search to discover what it is, we continue to find out what it is not.
Adapted from an article originally published on Universe Today.
For more on this research, see Ghostly Boson Clouds Could Solve the Mystery of Dark Matter.
Another possibility, from a view of String Theory, is that Dark Matter appears to us as an effect of string/anti-string annihilations. As you may know, quantum mechanics requires that strings must be formed as pairs in the quantum foam – a string and an anti-string – that immediately annihilate each other. Quantum mechanics also requires both the string and anti-string to be surrounded by “jitters” that reduce their monstrous vibrating energies. What if this jitter remains for a fraction of an instant after their string/anti-string annihilations? This temporary jitter would be seen by us as matter, via E=mc2, for that instant before it too returns to the foam. That’s why we never see it – the “mass” lasts only for that instant but is repeated over and over and over, all over. Specifics on this can be found in my YouTube, Dark Matter – A String Theory Way at https://www.youtube.com/watch?v=N84yISQvGCk
Could the dark matter boson be the force carrier of Dark Energy’s repulsion?
Another way to explain Dark Energy is suggested by String Theory. All matter and energy, including photons (light), have vibrating strings as their basis.
String and anti-string pairs are speculated to be created in the quantum foam, a roiling energy field suggested by quantum mechanics, and they immediately annihilate each other. If light passes near these string/anti-string annihilations, perhaps some of that annihilation energy is absorbed by the string in the light. Then the Fraunhofer lines in that light will move a bit towards the blue and away from the red shift. As this continues in an expanding universe we get the same curve displayed by Perlmutter and colleagues at their Nobel Prize lecture, without the need for Dark Energy.
This speculation has the universe behaving in a much more direct way. Specifics can be found in my YouTube, Dark Energy – a String Theory Way at https://www.youtube.com/watch?v=0b6t0jO7IgQ
Nice informative article. I’m not a believer in dark matter. It’s elusive because it’s an invention to solve irregularities in gravitational theory. I think will go the same way as N-rays in the early 1900’s.. a complete fallacy. We should not be destracted by theories of dark matter, but instead be investigating other theories regarding the inconsistencies… Saying that, I’m not even 100% convinced by big bang theory, any I know I’m not alone in that (I think possibly the extreme red shift if a factor relating to viewing stars in the very distant past. Anyway.. let’s see. It’s an exciting time for physics.
I think it is time to let go of the “dark matter theory” and start to reevaluate the theory of how and why galaxies stick together. The theory doesn’t fit the facts so it’s time for a new or another theory such as MOND for example.
Perhaps by looking into what makes the Corona of the Sun Shine so bright and hot compared to its surface temperature then you people might figure out the real creation of the Universe. Recently that Parker satellite orbiting the sun photographed STRING LIKE STRANDS of ESD like charged particles inside the Corona which come from outside the star not inside. Look at the Niels Bohr atom model that depict the mysterious ESD Cloud of Quark that accumulates to form a burst of photons in the form of particles and waves and knocks the Electron out of its orbit level. The Vacuum of Einstein’s curvature of space and time rushes into the Corona like a black holes event horizon and in the process creates the ESD Static quark cloud just as in the Atom and that quark is what is causing the extra bright and hot Corona which appears just as in the Parker satellite photoe.The Particles are not coming from the surface of the Sun or from its Chromosphere but from the Vacuum rushing into the Corona which is Kinetic Energy being converted into quark mass. Think about it and yes this info is FREE to whoever wishes to use it.
I think that was English. Wow.
I imagine dark matter and its subsequent dark energy as real force carriers such as gravity and created by the vacuum virtual particles. The virtual particles could have an anti-matter ecosystem smaller than sub standard model, which hosts all anti-matter particles. The particles would exist momentarily in the standard model and impart large scale gravity fields before their ecosystem reabsorbed them. The entropy of Dark matter could be dark energy and its dark force carrier gravity.
Helium 4 is not a Boson. It’s an atom composed of multiple baryons, of the fermion variety.
Gravity is a property of matter repulsive gravity is a property of dark matter.