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Category: cosmology

Gravitational waves as possible candidates for the origin of dark matter

Gravitational waves could be responsible for the production of dark matter during the early phases of our universe’s formation, according to results of a new study by Professor Joachim Kopp from Johannes Gutenberg University Mainz (JGU) and the PRISMA Cluster of Excellence in cooperation with Dr. Azadeh Maleknejad from Swansea University. Their work, published in Physical Review Letters, presents new calculations that explore a novel mechanism for the formation of dark matter through so-called stochastic gravitational waves.

In this way, they contribute to answering a fundamental question in particle physics. Planets, stars, and even life on Earth are all composed of visible matter. This type of matter only makes up about 4% of our universe. The vast majority is invisible, consisting of dark matter and dark energy. For instance, dark matter makes up about 23% of our universe.

Astrophysical observations confirm that dark matter permeates the whole universe and forms galaxies as well as the largest known structures in the cosmos. However, the particles that make up dark matter are still unknown. Many theories and ongoing experiments are looking for an answer to this open question.

This New Quantum Theory Could Change Everything We Know About the Big Bang

A new quantum gravity theory suggests the Big Bang may have unfolded naturally—and could soon be testable.

Scientists at the University of Waterloo have introduced a new approach to understanding how the universe began, one that could reshape current ideas about the Big Bang and the earliest stages of cosmic history. Their research indicates that the universe’s rapid initial expansion may have developed naturally from a deeper and more complete theory known as quantum gravity.

Combining Gravity With Quantum Physics

Gravitational waves suggest a ‘forbidden zone’ for stellar-origin black holes

An international team led by Monash University has uncovered evidence of a rare form of exploding star, helping to shed light on one of the most cataclysmic events in the universe. At the end of their lives, most massive stars collapse into black holes—objects with gravity so strong that not even light can escape.

Some very massive stars, however, are expected to become so hot that they are blown apart in a pair-instability supernova—an explosion so intense that the star is completely disrupted, leaving behind no black hole.

First predicted in the 1960s, pair-instability supernovae are challenging to distinguish from more common stellar explosions that leave behind black holes.

Primordial Magnetic Fields May Solve One of Cosmology’s Biggest Mysteries

Primordial magnetic fields may help explain why measurements of the universe’s expansion do not agree. Scientists have long known that the universe is expanding, yet there is still no agreement on how quickly that expansion is taking place. Two leading methods used to calculate the expansion r

Quadratic gravity theory reshapes quantum view of Big Bang

Waterloo scientists have developed a new way to understand how the universe began, and it could change what we know about the Big Bang and the earliest moments of cosmic history. Their work suggests that the universe’s rapid early expansion could have arisen naturally from a deeper, more complete theory of quantum gravity. The paper, “Ultraviolet completion of the Big Bang in quadratic gravity,” appears in Physical Review Letters.

Dr. Niayesh Afshordi, professor of physics and astronomy at the University of Waterloo and Perimeter Institute (PI), led the research team that explored a novel method of combining gravity with quantum physics, the rules that govern how the smallest particles in the universe behave. While general relativity has been successful for more than a century, it breaks down at the extreme conditions that existed at the birth of the universe. To address this problem, the team used Quadratic Quantum Gravity, which remains mathematically consistent even at extremely high energies—similar to the kind present during the Big Bang.

Most existing explanations for the Big Bang rely on Einstein’s theory of gravity, plus additional components added by hand. This new approach offers a more unified picture that connects the earliest moments of the universe to the well-tested cosmology scientists observe today.

In wrangling dark matter, some scientists find inspiration in the Torah, Krishna and Christ

When an invisible entity making up 85% of the universe’s mass stumps the greatest scientific minds of our time, awe is an understandable response.

Physicists call it dark matter, a substance they describe as the cosmic glue, the scaffolding, a web that uses gravity to corral, shape and hold together stars, planets and galaxies. Yet nobody knows exactly what it is.

Dark matter’s existence is only inferred from its gravitational effects on visible matter. Together with dark energy—a mysterious force causing the universe to expand at an accelerated rate—they are the biggest scientific mysteries of our time.

Astrophysicists trace the origin of valuable metals in space, from colliding stars to merging galaxies

Billions of light years away in a remote part of the universe, two neutron stars—the ultradense remnants of dead stars—collided. The catastrophic cosmic event sent light and particles, including a sudden flash of gamma rays, streaming through the universe. These gamma rays traveled for 8.5 billion years before reaching Earth.

In a new study, our team of astrophysicists examined this gamma-ray signal. We learned that the stellar collision it came from was likely caused by an even more catastrophic encounter—a merger between two galaxies.

This is the first time astronomers associated this type of signal with such a large-scale galactic interaction. Our finding offers new insight into how stellar collisions spread metals across the universe.

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