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Category: cosmology – Page 417

Monster black holes shooting jets of gamma-ray radiation right at us have been spotted farther away than ever before, dating back to when the universe was nearly one-tenth its current age.

The five distant objects, called gamma-ray blazars, deepen the mystery of how black holes so large could have formed so early in the universe’s history.

Roopesh Ojha, an astronomer at NASA’s Goddard Space Flight Center in Maryland, presented the new results during a press conference today (Jan. 30) at the American Physical Society meeting in Washington, D.C. The results will also be published in The Astrophysical Journal Supplement. [Found: Gamma-Ray Blazars Powered by ‘Supersized’ Black Holes (Video)].

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Awesome! More news on the time crystals.

The source of time travel speculation lies in the fact that our best physical theories seem to contain no prohibitions on traveling backward through time. The feat should be possible based on Einstein’s theory of general relativity, which describes gravity as the warping of spacetime by energy and matter. An extremely powerful gravitational field, such as that produced by a spinning black hole, could in principle profoundly warp the fabric of existence so that spacetime bends back on itself. This would create a “closed timelike curve,” or CTC, a loop that could be traversed to travel back in time.

Experimenting With CTC’s

Single particles of light (photons) to simulate quantum particles travelling through time were just used by scientists from the University of Queensland, Australia. They showed that one photon can pass through a wormhole and then interact with its older self. Their findings were published in Nature Communications.

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(Phys.org)—Physicists have proposed that violations of energy conservation in the early universe, as predicted by certain modified theories of quantum mechanics and quantum gravity, may explain the cosmological constant problem, which is sometimes referred to as “the worst theoretical prediction in the history of physics.”

The physicists, Thibaut Josset and Alejandro Perez at the University of Aix-Marseille, France, and Daniel Sudarsky at the National Autonomous University of Mexico, have published a paper on their proposal in a recent issue Physical Review Letters.

“The main achievement of the work was the unexpected relation between two apparently very distinct issues, namely the accelerated expansion of the universe and microscopic physics,” Josset told Phys.org. “This offers a fresh look at the cosmological constant problem, which is still far from being solved.”

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The big bang poses a big question: if it was indeed the cataclysm that blasted our universe into existence 13.7 billion years ago, what sparked it? Three researchers at the Perimeter Institute for Theoretical Physics and the University of Waterloo propose that the big bang could be the three-dimensional “mirage” of a collapsing star in a universe profoundly different than our own.

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An international team of astronomers have discovered a ‘cosmic one-two punch’ in the night sky that has never been seen before. In one image, the team managed to spot a supermassive black hole and two gigantic galaxy clusters colliding at the same time.

Matter ejected from the black hole gets caught up inside the violent galactic collisions, turning this dynamic duo into one hell of an enormous cosmic particle accelerator.

“We have seen each of these spectacular phenomena separately in many places,” said team leader Reinout van Weeren, from the Harvard-Smithsonian Centre for Astrophysics.

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NASA’s Chandra X-ray Observatory has completed the deepest X-ray image ever obtained, made with over 7 million seconds of observing time revealing the best picture ever at the growth of black holes over billions of years beginning soon after the Big Bang. The central region of the image contains the highest concentration of supermassive black holes ever seen, equivalent to about 5,000 objects that would fit into the area of the full Moon and about a billion over the entire sky.

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We examine the effect of the stress tensor of a quantum matter field, such as the electromagnetic field, on the spectrum of primordial gravity waves expected in inflationary cosmology. We find that the net effect is a small reduction in the power spectrum, especially at higher frequencies, but which has a different form from that described by the usual spectral index. Thus this effect has a characteristic signature, and is in principle observable. The net effect is a sum of two contributions, one of which is due to quantum fluctuations of the matter field stress tensor. The other is a quantum correction to the graviton field due to coupling to the expectation value of this stress tensor. Both contributions are sensitive to initial conditions in the very early universe, so this effect has the potential to act as a probe of these initial conditions.

Read this paper on arXiv…

J. Hsiang, L. Ford, K. Ng, et. al. Thu, 5 Jan 17 31/58.

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