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Observations of supermassive black holes at the centers of galaxies point to a likely source of dark energy – the ‘missing’ 70% of the Universe.

Continue reading “First Evidence that Black Holes are the Source of Dark Energy” »

When two black holes collide into each other to form a new bigger black hole, they violently roil spacetime around them, sending ripples, called gravitational waves, outward in all directions. Previous studies of black hole collisions modeled the behavior of the gravitational waves using what is known as linear math, which means that the gravitational waves rippling outward did not influence, or interact, with each other. Now, a new analysis has modeled the same collisions in more detail and revealed so-called nonlinear effects.

“Nonlinear effects are what happens when waves on the beach crest and crash,” says Keefe Mitman, a Caltech graduate student who works with Saul Teukolsky (Ph. D. ‘74), the Robinson Professor of Theoretical Astrophysics at Caltech with a joint appointment at Cornell University.

“The waves interact and influence each other rather than ride along by themselves. With something as violent as a black hole merger, we expected these effects but had not seen them in our models until now. New methods for extracting the waveforms from our simulations have made it possible to see the nonlinearities.”

The James Webb Space Telescope (JWST) is still doing its job — and doing it very well. Released today, this image shows the arms of barred spiral galaxy NGC 1,433 teeming with young stars that can be seen affecting the clouds of gas and dust around them. The image was taken as part of the Physics at High Angular resolution in Nearby Galaxies (PHANGS) collaboration, of which more than 100 researchers around the world are a part.

One of the James Webb Space Telescope’s first science programs is to image 19 spiral galaxies for PHANGS with its Mid-Infrared Instrument (MIRI), which is capable of seeing through gas and dust clouds that are impenetrable with other types of imaging.

A combined team of physicists from Harvard University and Northwestern University has found the most precise value yet for the magnetic moment of an electron. In their paper published in the journal Physical Review Letters, the group describes the methods they used to measure properties of an electron and implications of the new precision.

The magnetic moment of an electron, also known as the electron magnetic dipole moment, results from its electric and spin properties. Of all the elementary properties that have been studied, it is the one that has been the most precisely measured, and also the most accurately verified.

Measuring the magnetic moment of an electron to ever higher standards of accuracy is important because physicists believe that at some point, such measurements will help to complete the standard model of physics. In this new effort, the research group has measured the magnetic moment to a precision twice that of any other effort—the last best effort was 14 years ago.

I explore the reduction of thermodynamics to statistical mechanics by treating the former as a control theory: a theory of which transitions between states can be induced on a system (assumed to obey some known underlying dynamics) by means of operations from a fixed list. I recover the results of standard thermodynamics in this framework on the assumption that the available operations do not include measurements which affect subsequent choices of operations. I then relax this assumption and use the framework to consider the vexed questions of Maxwell’s demon and Landauer’s principle. Throughout I assume rather than prove the basic irreversibility features of statistical mechanics, taking care to distinguish them from the conceptually distinct assumptions of thermodynamics proper.

Annual UWO Philosophy of Physics Conference.
Thermodynamics as a Resource Theory: Foundational and Philosophical Implications.
June 20–22, 2018
http://philphysics.uwo.ca.
David Wallace, University of Southern California.

Continue reading “David Wallace: Thermodynamics as control theory” »

Dark energy is the name physicists have given to the mysterious thing driving the universe’s accelerated expansion. It may be a force or a form of energy, and one piece of evidence suggests it is hidden inside black holes.

Sir Roger Penrose, a mathematician and physicist from the University of Oxford who recently shared this year’s Nobel Prize in physics, says that our universe has undergone numerous Big Bangs, with another one on the way.

The acoustically generated force will help astronomers better understand the sun’s photosphere and the causes of space weather.

Two neutron stars collided which caused a huge explosion but with an unusually flawless form, baffling scientists. Usually, a collision between neutron stars would lead to a flattened cloud but the recently observed explosion formed a perfectly spherical shape, SpaceAcademy.org reports.

It is still unclear how this is possible, but a new study may shed light on the fundamental physics involved and help scientists calculate the universe’s age. Astrophysicists from the Universe of Copenhagen discovered the kilonova and described it in full in their study, titled “Spherical Symmetry in the Kilonova At2017gfo/GW170817,” which was published in the journal Nature.