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Tag: Gravitational Waves

  • Using Gravitational Waves to Hunt for Dark Matter

    Using Gravitational Waves to Hunt for Dark Matter

    Credit: Unsplash.

    A global team of cosmologists has discovered through computer simulations that observing gravitational waves from merging black holes can reveal the real nature of dark matter. Dr. Alex Jenkins of University College London will co-author their discovery today at the 2023 National Astronomy Meeting.

    The team studied the production of gravitational wave signals in simulated universes with various types of dark matter through computer simulations. Their findings show that counting the number of black hole merger events found by the next generation of observatories can tell us whether or not dark matter interacts with other particles. This gives us new insights into what it is made of.

    The understanding of cosmologists

    Cosmologists generally believe that our understanding of the cosmos lacks dark matter. Despite solid evidence that it accounts for 85% of all matter in the universe, there is no current consensus on the underlying nature of dark matter. This covers whether dark matter particles can collide with others, such as atoms or neutrinos, or can pass directly through them unaffected.

    To verify this, you can look at how galaxies form into haloes, dense clouds of dark matter. The structure of the dark matter disperses when it collides with the neutrinos, resulting in fewer galaxies forming. The problem with this method is that all the galaxies that disappear are tiny and very far away from us. Even with the best telescopes available, it is difficult to determine whether they are there.

    Exploring the Structure of the Universe Through Gravitational Waves: Future Perspectives

    The authors of this study suggest using gravitational waves to indirectly measure the abundance of vanishing galaxies rather than seeing them directly. Their simulation shows far fewer black hole mergers in the distant universe in models where dark matter collides with other particles. Although this effect is too small to be observed by the gravitational-wave experiments currently being performed, it will be an important target for the next generation of observatories that are being planned.

    The authors hope their methods will stimulate new ideas for using gravitational-wave data to explore the universe’s large-scale structure and shed new light on the mysterious nature of dark matter.

    Dr. Sownak Bose of Durham University, a co-author, said: Our understanding of the universe still faces many mysteries, including dark matter. This indicates that it is crucial to continue discovering new ways to study dark matter models, combining new and existing probes to test model predictions as much as possible. The study of gravitational wave astronomy allows for a better understanding of dark matter and the formation and evolution of galaxies in general.

    Co-authors’ Statements on Gravitational Waves and the Evolution of the Universe

    The other co-author, Markus Mosbech of the University of Sydney, added: As they pass unimpeded through the universe, gravitational waves offer us a unique opportunity to observe the early universe, and next-generation interferometers will be sensitive enough to detect individual events over enormous distances.

    Professor Mairi Sakellariadou of King’s College London, another member of the research team, said: The third generation gravitational wave data will provide a new and independent way to test the current model describing the evolution of our universe and shed light on the still unknown nature of dark matter.

    Read the original article on PHYS.

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  • “Boson Clouds” Could Explain Dark Matter

    “Boson Clouds” Could Explain Dark Matter

    Credit:  Brian Koberlein

    The nature of dark matter stills astonishes astronomers. As the search for dark matter particles keeps on turning up nothing, it is tempting to throw away the dark matter model altogether, but indirect evidence for the stuff remains to be strong. So what is it? One team has an idea, and they have released the results of their very first search.

    The conditions of dark matter imply that it cannot be regular matter. Regular matter (atoms, molecules, and so forth) easily absorbs and emits light. Even if dark matter were clouds of molecules so frigid, they emitted practically no light, these clouds would still show up by the light they soak up. They would resemble dark nebula typically seen near the galactic plane.

    There are not enough of them to account for the effects of dark matter we observe. We have likewise eliminated neutrinos. They do not interact strongly with light. However, neutrinos are a form of “hot” dark matter because neutrinos move at almost the speed of light. We know that the majority of dark matter should be sluggish and consequently “cold.” If dark matter is out there, it has to be something else.

    Dark matter and elementary particles

    In their most recent work, the authors argue that dark matter could be constructed from particles referred to as scalar bosons. All identified matter can be put in 2 huge categories known as fermions and bosons. A particle’s category depends on a quantum property referred to 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 kind of particle with a spin of 0 is a scalar boson.

    Quarks and leptons are fermions, while force carriers are bosons. Credit: Fermilab

    While it appears like a trivial difference, both types of particles behave very differently when united in large groups. Fermions can never occupy the exact same quantum state, so when you try to press them with each other, they push back. This is why white dwarfs and neutron stars exist.

    Gravity attempts to push electrons or neutrons together, but the Fermi pressure is so strong that it can withstand gravity (up to a point). On the other hand, Bosons are completely pleased occupying the same state. So if you supercool a lot of bosons (such as helium-4), they can settle right into an odd quantum object called a Bose-Einstein condensate.

    The only recognized scalar boson is the Higgs boson. The Higgs cannot be dark matter considering its known properties; however, some theories suggest other scalar bosons. These would certainly not interact strongly with light, only with gravity. Since light cannot substantially heat them up, in time, these scalar bosons would certainly cool and collapse into big clouds. So probably dark matter is constructed from huge diffuse clouds of scalar bosons.

    How would researchers confirm this idea?

    Illustration of a quark core in a neutron star. Credit: Jyrki Hokkanen, CSC– IT Center for Science

    It appears that considering that scalar bosons interact gravitationally, they also interact with gravitational waves. Depending on their mass, scalar bosons may also decay by emitting gravitons. Therefore, scalar bosons can create lasting gravitational waves with a similar frequency. It is the gravitational equivalent of a slight hum.

    The team observed the gravitational-wave data from LIGO and Virgo. They tried to find evidence of a gravitational hum in the 20– 600 Hz range and found nothing. The authors conclude that there are no young scalar boson clouds in our galaxy based on their work. There are additionally no old and cold scalar boson clouds within 3,000 light-years of Earth.

    This research study does not entirely eliminate scalar bosons, but it strongly limits the idea. Furthermore, now that appears to be the story of dark matter. In our search to find what it is, we continue to learn what it is not.

    Read the original article on Scitech Daily.

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