Dark matter, dark energy, dark… magnetism?

Dark matter, dark energy, dark… magnetism?:   In 2008 at the Complutense University of Madrid, Spain, they were playing with a particular version of a mutant gravity model called a vector-tensor theory, which they had found could mimic dark energy. Then came a sudden realisation. The new theory was supposed to be describing a strange version of gravity, but its equations bore an uncanny resemblance to some of the mathematics underlying another force. "They looked like electromagnetism," says Beltrán, now based at the University of Geneva in Switzerland. "We started to think there could be a connection."

So they decided to see what would happen if their mathematics described not masses and space-time, but magnets and voltages...

Crucially, inflation could also have boosted the new electromagnetic waves. Beltrán and Maroto found that this process would leave behind vast temporal modes: waves of electric potential with wavelengths many orders of magnitude larger than the observable universe. These waves contain some energy but because they are so vast we do not perceive them as waves at all.

Gamma-Ray Bending Opens New Door for Optics

Gamma-Ray Bending Opens New Door for Optics: Theory says that gamma rays, being even more energetic than x-rays, ought to bypass orbiting electrons altogether; materials should not bend them at all and the refractive index for gamma rays should be almost equal to one...

ILL is a research reactor that produces intense beams of neutrons. Habs, Jentschel, and colleagues used one of its beams to bombard samples of radioactive chlorine and gadolinium to produce gamma rays. They directed these down a 20-meter-long tube to a device known as a crystal spectrometer, which funneled the gamma rays into a specific direction. They then passed half of the gamma rays through a silicon prism and into another spectrometer to measure their final direction, while they directed the other half straight to the spectrometer unimpeded. To the researchers' surprise, as they report in a paper due to be published this month in Physical Review Letters, gamma rays with an energy above 700 kiloelectronvolts are slightly bent by the silicon prism...

So what drives this new bending effect? Although he can't be sure, Habs believes it resides in the nuclei at the heart of the silicon atoms. Although electrons don't normally reside in nuclei because of the very strong electric fields there, quantum mechanics allows pairs of "virtual" electrons and antielectrons, or positrons, to blink briefly into existence and then recombine and disappear again. Habs thinks the sheer number of these virtual electron-positron pairs amplifies the gamma-ray scattering, which is normally negligible, to a detectable amount.

Short Sharp Science: Spinning space telescope's view of a pulsar

Short Sharp Science: Spinning space telescope's view of a pulsar: It can't be so easy to keep the Fermi Gamma-ray Space Telescope trained on one spot in the sky as it maps the universe. Fermi orbits the Earth every 95 minutes while rocking between the north and the south on alternate orbits, On top of this, the satellite also completes one rotation every 54 days to keep its solar panels facing the sun.

This image traces Fermi's view via its Large Area Telescope of the gamma rays emitted by the Vela pulsar from August 2008 to August 2010. The Vela pulsar is a neutron star, itself spinning at a dizzying 11 times per second and the brightest and most persistent source of gamma rays in the sky, giving an anchoring point for Fermi's own spin.

Mini Black Holes Could Form Gravitational Atoms - Technology Review

Mini Black Holes Could Form Gravitational Atoms - Technology Review: Normally, gravity is so weak that it can effectively be ignored at the scale of atoms. But that's not the case for mini black holes, which should generate forces capable of trapping atoms into orbit around them...

These objects must have a gravitational field powerful enough to attract objects such as neutral atoms into orbit around them. But they must also have a radius that is so small that the chances of the orbiting atom encountering the black hole is vanishingly small.
The VanDevenders say that this should be true for black holes with a mass significantly smaller than a few hundred billion kilograms. And they go on to give a detailed study of some of the properties of these gravitational atoms.

Proposed gamma-ray laser could emit 'nuclear light'

Proposed gamma-ray laser could emit 'nuclear light': “In the nuclear gamma-ray laser, the photons are emitted by atomic nuclei.”
In the study, which is published in a recent issue of Physical Review Letters, Tkalya explains that a nuclear gamma-ray laser has to overcome at least two basic problems: accumulating a large amount of isomeric nuclei (nuclei in a long-lived excited state) and narrowing down the gamma-ray emission line. The new proposal fulfills these requirements by taking advantage of thorium’s unique nuclear structure, which enables some of the photons from an external laser to interact directly with thorium’s nuclei rather than its electrons.

Hints of lightweight dark matter particle found in space - space - 28 October 2010 - New Scientist

Hints of lightweight dark matter particle found in space: In a new analysis of two years of data collected by NASA's orbiting Fermi telescope, the team has found evidence of excess gamma-ray light emitted from the inner 100 light years of the galaxy.

They say the light is too bright, energetic, and confined to be explained by known gamma-ray sources. "We're at a point where we have a clear signal of what we think could be dark matter, without any alternative explanation," Hooper says.

Black holes dark matter = light - space - 27 August 2010 - New Scientist

Black holes dark matter = light: "They found that rather than simply ricocheting off one another, some of the electrons and dark matter particles could fuse together, transforming into a single, supersymmetric or extra-dimensional version of the electron. This particle would be heavy, and much of the electron's kinetic energy would be dumped into making the new particle. As a result, the particle would be almost standing still.

If the particle were then to decay into an electron and a ground-state dark matter particle, the electron would release gamma rays. Unlike a particle travelling fast, like those in the jets, the slow-moving particle would emit rays that could travel in any direction. This could potentially make them easier to distinguish from the flood of photons in the jet, says collaborator Mikhail Gorshteyn of Indiana University in Bloomington."

Gamma rays may betray clumps of dark matter - New Scientist - New Scientist

Gamma rays may betray clumps of dark matter - New Scientist - New Scientist - "Their model shows that the Milky Way should be littered with small clumps of dark matter, each about the size of our solar system. These would have been the first structures that formed in the universe. Earlier studies had suggested that the gravity of nearby stars would have ripped apart these primordial clumps, but the new simulations show that this would only happen in the crowded core of galaxies, leaving the clumps in the galactic suburbs intact"