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Category: cosmology – Page 93

More comprehensive search for sterile neutrinos comes up empty

Particle physicists have been looking for so-called “sterile neutrinos” for a few decades now. They are a hypothesized particle that would have a tiny mass like the three known neutrinos but would not interact by the weak force or any other Standard Model force, only through gravitational interactions.

Its existence—or their existence—would solve some anomalies seen in , help answer questions beyond the Standard Model of particle physics, and, if massive enough, could explain cold dark matter or warm dark matter.

But have not been seen in any particle experiments, despite many attempts. Now an experiment by the IceCube Collaboration has used 10.7 years of data from their detector near the Amundsen-Scott South Pole Station to lower the probability that at least one sterile neutrino does not exist. Their paper appears in Physical Review Letters.

Why the [expletive] can’t we travel back in time?

Observations of the cosmic microwave background, leftover light from when the Universe was only 380,000 years old, reveal that our cosmos is not rotating. Infinitely long cylinders don’t exist. The interiors of black holes throw up singularities, telling us that the math of GR is breaking down and can’t be trusted. And wormholes? They’re frighteningly unstable. A single photon passing down the throat of a wormhole will cause it to collapse faster than the speed of light. Attempts to stabilize wormholes require exotic matter (as in, matter with negative mass, which isn’t a thing), and so their existence is just as debatable as time travel itself.

This is the point where physicists get antsy. General relativity is telling us exactly where time travel into the past can be allowed. But every single example runs into other issues that have nothing to do with the math of GR. There is no consistency, no coherence among all these smackdowns. It’s just one random rule over here, and another random fact over there, none of them related to either GR or each other.

If the inability to time travel were a fundamental part of our Universe, you’d expect equally fundamental physics behind that rule. Yet every time we discover a CTC in general relativity, we find some reason it’s im possible (or at the very least, implausible), and the reason seems ad hoc. There isn’t anything tying together any of the “no time travel for you” explanations.

Insanely bright light bursts from a black hole pair shock scientists

Scientists detect two giant black holes flashing light a billion light-years away.

Astronomers have identified two giant black holes causing strange flashes of light at about one billion light years away from Earth. The flashes or light bursts are occurring at regular intervals, but what’s causing them is even more surprising.

The researchers suggest that the black hole pair is swirling within a vast cloud of gas, and their interaction with the gas cloud is actually sparking the unusual flashes —- marking it as the first observation of its kind.

Extending classical black hole inequalities into the quantum realm

A recent study in Physical Review Letters explores quantum effects on black hole thermodynamics and geometry, focusing on extending two classical inequalities into the quantum regime.

Black holes have been thoroughly studied through a classical approach based on Einstein’s general theory of relativity. However, this approach does not account for quantum effects like Hawking radiation.

The goal of the study was for the researchers to refine classical theories by including quantum effects, thereby offering an improved understanding of black hole dynamics.

Dark matter’s search could be end by a nearby supernova explosion

Researchers at UC Berkeley proposed that axions, hypothetical particles, could be detected shortly after a supernova’s gamma rays. They suggest that the Fermi Gamma-ray Space Telescope has a 1 in 10 chance of observing this phenomenon. Axions would be produced during the early moments of a star’s collapse and would then transform into high-energy gamma rays in the star’s magnetic field.

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Dead and Alive: Astronomers Uncover Star Pairs Transforming Our Universe

Astronomers have made a groundbreaking discovery of binary star systems, consisting of a white dwarf and a main sequence star, within young star clusters.

This discovery opens up new avenues for understanding stellar evolution and could provide insights into the origins of phenomena such as supernovas and gravitational waves.

Breakthrough Discovery in Star Clusters.

Dark Matter at Cosmic Dawn

Low-frequency radio observations could allow researchers to distinguish among several dark matter models, thanks to dark matter’s influence on the early Universe.

The profusion of dark matter candidates reflects how easy it is for any of them to explain the current large-scale structure of the Universe. Decisive clues about dark matter’s true nature are more likely to appear at earlier epochs. Unfortunately, those clues are harder to observe. Now Jo Verwohlt of the University of Copenhagen in Denmark and her collaborators have shown how a deeply redshifted hydrogen line could unmask dark matter [1]. To do so, they also identified confounding signatures from regular, baryonic matter.

Some theories posit that dark matter interacts with so-called dark radiation. In the dense early Universe, the heating effect of that interaction could have been enough for large concentrations of dark matter known as halos to temporarily and repeatedly resist gravitational collapse. Termed dark acoustic oscillations (DAOs), these cycles of expansion and collapse would have quickly died out. But before they did, they could have affected the onset of “cosmic dawn.” That’s when the first galaxies formed from primordial gas drawn into the halos.

A nearby supernova could end the search for dark matter

The search for the universe’s dark matter could end tomorrow—given a nearby supernova and a little luck. The nature of dark matter has eluded astronomers for 90 years, since the realization that 85% of the matter in the universe is not visible through our telescopes. The most likely dark matter candidate today is the axion, a lightweight particle that researchers around the world are desperately trying to find.

Astrophysicists at the University of California, Berkeley, now argue that the axion could be discovered within seconds of the detection of gamma rays from a nearby supernova explosion. Axions, if they exist, would be produced in copious quantities during the first 10 seconds after the core collapse of a massive star into a neutron star, and those axions would escape and be transformed into in the star’s intense magnetic field.

Such a detection is possible today only if the lone gamma-ray telescope in orbit, the Fermi Gamma-ray Space Telescope, is pointing in the direction of the supernova at the time it explodes. Given the telescope’s field of view, that is about one chance in 10.

‘Mind-blowing’ dark energy instrument results show Einstein was right about gravity — again

Scientists have now performed one such large-scale test by using DESI. They observed almost 6 million galaxies and quasars, which are bright hearts of galaxies powered by feeding supermassive black holes. Perhaps unsurprisingly, this test, which has traced the evolution of the universe since it was around 3 billion years old, has once again shown general relativity to be the right “recipe” for gravity.

“General relativity has been very well tested at the scale of solar systems, but we also needed to test that our assumption works at much larger scales,” study co-leader and the French National Center for Scientific Research (CNRS) cosmologist Pauline Zarrouk said in a statement. “Studying the rate at which galaxies formed lets us directly test our theories and, so far, we’re lining up with what general relativity predicts at cosmological scales.”

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