Lifeboat Foundation

Signals can be amplified by an optimum amount of noise, but stochastic resonance is a fragile phenomenon. Researchers at AMOLF were the first to investigate the role of memory for this phenomenon in an oil-filled optical microcavity. The effects of slow non-linearity (i.e. memory) on stochastic resonance were never considered before, but these experiments suggest that stochastic resonance becomes robust to variations in the signal frequency when systems have memory. This has implications in many fields of physics and energy technology. In particular, the scientists numerically show that introducing slow nonlinearity in a mechanical oscillator harvesting energy from noise can increase its efficiency tenfold. They have published their findings in Physical Review Letters on May 27th.

It is not easy to concentrate on a difficult task when two people are having a loud discussion right next to you. However, complete silence is often not the best alternative. Whether it is some soft music, remote traffic noise or the hum of people chatting in the distance, for many people, an optimum amount of noise enables them to concentrate better. “This is the human equivalent of stochastic resonance,” says AMOLF group leader Said Rodriguez. “In our scientific labs, stochastic resonance happens in nonlinear systems that are bistable. This means that, for a given input, the output can switch between two possible values. When the input is a periodic signal, the response of a non-linear system can be amplified by an optimum amount of noise using the stochastic resonance condition.”

Pulses of laser light moving through a jet of plasma can surf a wave to travel faster or slower than the speed of light without breaking the laws of physics.

Five years on from the first discovery of gravitational waves, an international team of scientists, including from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), are continuing the hunt for new discoveries and insights into the Universe. Using the super-sensitive, kilometer-sized LIGO detectors in the United States, and the Virgo detector in Europe, the team have witnessed the explosive collisions of black holes and neutron stars. Recent studies, however, have been looking for something quite different: the elusive signal from a solitary, rapidly-spinning neutron star.

Take a star similar in size to the Sun, squash it down to a ball about twenty kilometers across — roughly the distance from Melbourne airport to the city center — and you’d get a neutron star: the densest object in the known Universe. Now set your neutron star spinning at hundreds of revolutions per second and listen carefully. If your neutron star isn’t perfectly spherical, it will wobble about a bit, and you’ll hear a faint “humming” sound. Scientists call this a continuous gravitational wave.

So far, these humming neutron stars have proved elusive. As OzGrav postdoctoral researcher Karl Wette from the Australian National University explains: Imagine you’re out in the Australian bush listening to the wildlife. The gravitational waves from black hole and neutron star collisions we’ve observed so far are like squawking cockatoos — loud and boisterous, they’re pretty easy to spot!

A new map of dark matter in the local universe reveals several previously undiscovered filamentary structures connecting galaxies. The map, developed using machine learning by an international team including a Penn State astrophysicist, could enable studies about the nature of dark matter as well as about the history and future of our local universe.

Dark matter is an elusive substance that makes up 80% of the universe. It also provides the skeleton for what cosmologists call the cosmic web, the large-scale structure of the universe that, due to its gravitational influence, dictates the motion of galaxies and other cosmic material. However, the distribution of local dark matter is currently unknown because it cannot be measured directly. Researchers must instead infer its distribution based on its gravitational influence on other objects in the universe, like galaxies.

“Ironically, it’s easier to study the distribution of dark matter much further away because it reflects the very distant past, which is much less complex,” said Donghui Jeong, associate professor of astronomy and astrophysics at Penn State and a corresponding author of the study. “Over time, as the large-scale structure of the universe has grown, the complexity of the universe has increased, so it is inherently harder to make measurements about dark matter locally.”

To better understand the universe, we may need to kill off one of the most important theories of all time.

With machine learning, astrophysicists can now simulate vast, complex universes in a fraction of the time it takes with conventional methods.

Researchers at the Flatiron Institute’s Center for Computational Astrophysics published a paper last week that just might explain a mysterious gap in planet sizes beyond our solar system. Planets between 1.5 and 2 times Earth’s radius are strikingly rare. This new research suggests that the reason might be because planets slightly larger than this, called mini-Neptunes, lose their atmospheres over time, shrinking to become ‘super-Earths’ only slightly larger than our home planet. These changing planets only briefly have a radius the right size to fill the gap, quickly shrinking beyond it. The implication for planetary science is exciting, as it affirms that planets are not static objects, but evolving and dynamic worlds.

Exoplanet research is a very young field. As recently as 1992, no one had ever seen a planet beyond our solar system. Today, we’ve discovered more than 4700 of them, and that number is growing rapidly due to the efforts of dedicated planet-hunting space telescopes like Kepler (now defunct) and its successor, TESS. We’ve suddenly gained an enormous new sample size of planets to study, beyond the eight planets (sorry Pluto) that orbit around our sun.

Kepler, TESS, and other planet hunters have discovered brand new types of planets, like so-called ‘hot-Jupiters,’ large gas giants that orbit very close to their star. These were among the first exoplanets observed because their large size made them easy to find, and their small, fast orbital periods meant we could see them pass in front of their star more than once in a short period of time (some hot-Jupiters have a year that lasts only a few Earth days).

This is how the future is made.

Sailing through the smooth waters of vacuum, a photon of light moves at around 300 thousand kilometers (186 thousand miles) a second. This sets a firm limit on how quickly a whisper of information can travel anywhere in the Universe.

While this law isn’t likely to ever be broken, there are features of light which don’t play by the same rules. Manipulating them won’t hasten our ability to travel to the stars, but they could help us clear the way to a whole new class of laser technology.

Continue reading “Physicists Have Broken The Speed of Light With Pulses Inside Hot Plasma” »

Nobody knows exactly how big the Universe actually is.

The cosmos has been expanding since the Big Bang, but how fast? The answer could reveal whether everything we thought we knew about physics is wrong.