The Great Cold Spot in the cosmic microwave background

The Great Cold Spot in the cosmic microwave background: The CMB cold spot is not particularly colder than other cold regions of the CMB, but it is unusual because it is a particularly cold region surrounded by a rather warm region. Simulations of random fluctuations in a CMB estimate that the odds of such a cold spot happening in the universe is about 1 in 100. So it's possible that it is just a random fluctuation. But the 1% odds is small enough that some astronomers have looked for a possible cause, and these ideas have ranged from the mundane to the wild.

Ask Ethan #49: Do the cosmic unknowns cast doubt on the Big Bang? — Starts With A Bang! — Medium

Ask Ethan #49: Do the cosmic unknowns cast doubt on the Big Bang? — Starts With A Bang! — Medium:  ...all isotropic, homogeneous spacetimes (that is, solutions to GR that are roughly the same at all locations in space and in all directions) must either have expanding or contracting space...

All of this — the whole story I outlined above — would be true regardless of what else is actually in your Universe. The only things that change due to dark matter and dark energy are the following...

‘Unparticles’ May Hold The Key To Superconductivity, Say Physicists — The Physics arXiv Blog — Medium

‘Unparticles’ May Hold The Key To Superconductivity, Say Physicists — The Physics arXiv Blog — Medium: Georgi’s concept of unparticles comes about by conjecturing that some “stuff” may have mass, energy and momentum and yet also be scale invariant...

Physicists have long known that the behaviour of electrons in high-temperature superconductors is extremely complex...

What LeBlanc and Grushin show is that under certain conditions the interaction between these entities can become scale invariant and is therefore described by the physics of unparticles. In very simple terms, when that happens, material properties such as resistance no longer depend on the length scales involved. So if electrons move without resistance on a tiny scale, they should also move without resistance on much larger scales too. Hence the phenomenon of superconductivity.

Quantum split: Particle this way, properties that way - physics-math - 23 July 2014 - New Scientist

Quantum split: Particle this way, properties that way - physics-math - 23 July 2014 - New Scientist: In Grenoble, the Vienna team used a feeble magnetic field and a weakly interacting neutron absorber to make the weak measurements. They found that when they put the absorber in one path of the interferometer (say left), there was a discernible effect at the output. But when they put it in the right path, it had no such effect. The neutrons were travelling in one path only.

Next, the experimenters introduced a weak magnetic field near each arm of the interferometer, to interact with the spin of the neutrons. When they did this in the left path, there was no change in the interferometer's output. If they introduced the magnetic field in the right path, though, there was a change: the magnetic field had interacted with the spin. In other words, they had confirmed that the spin had chosen the path not taken by the parent neutron...

White holes: Hunting the other side of a black hole - space - 20 July 2014 - New Scientist

White holes: Hunting the other side of a black hole - space - 20 July 2014 - New Scientist: Perhaps the fact that we have found no signs of a white hole, despite peering ever deeper into space, is a more fundamental problem. Enter a space telescope called RadioAstron whose wildly elongated orbit takes it out to a distance of 350,000 kilometres – nearly as far as the moon and 30 times wider than Earth's diameter. Launched from Kazakhstan's Baikonur Cosmodrome in 2011, its dish is only 10 metres across. But when its signals are combined with those from radio telescopes on Earth, the resulting images are as sharp as those from a dish 350,000 kilometres wide...

"...once we spot a gigantic powerful gamma-ray burst with a lot of radio radiation, we will take a close look with RadioAstron and try to determine its shape and size for the first time." That could provide important clues about its source. "It may be a white hole or a wormhole. Maybe the flashes are coming from another universe."

New metamaterial gives light a one-way ticket

New metamaterial gives light a one-way ticket:  ...The silver-glass structure is an example of a "hyperbolic" metamaterial, which treats light differently depending on which direction the waves are traveling...

While the second set of grates let light escape the material, their spacing was slightly different from that of the first grates. As a result, the reverse-direction grates bent incoming light either too much or not enough to propagate inside the silver-glass layers. Testing their structures, the researchers found that around 30 times more light passed through in the forward direction than in reverse, a contrast larger than any other achieved thus far with visible light.

Combining materials that could be made using existing methods was the key to achieving one-way transmission of visible light, Lezec says. Without the intervening silver-and-glass blocks, the grates would have needed to be fabricated and aligned more precisely than is possible with current techniques. "This three-step process actually relaxes the fabrication constraints," Lezec says.

Embrace the lumpiverse: How mess kills dark energy - physics-math - 25 June 2014 - New Scientist

Embrace the lumpiverse: How mess kills dark energy - physics-math - 25 June 2014 - New Scientist: Wiltshire takes issue with the last of the motions used to make the dipole anisotropy disappear: a movement at a speed of 635 kilometres per second of the entire Local Group towards a "great attractor" somewhere in the distant Hydra-Centaurus supercluster of galaxies...

They claim the galaxies' movements make most sense if the Local Group isn't moving at all. Instead, the greater density of matter towards Hydra-Centaurus is slowing the universe's expansion along our line of sight, giving us the impression of such a movement. A comparative void in the other direction, meanwhile, is producing the opposite effect, causing an area of faster expansion behind us. The effects of the inhomogeneities along this axis are comparatively local, occurring on scales up to about 300 million light years, and only alter the universe's expansion rate by some 0.5 per cent. But they are sufficient to account for nearly all of the dipole anisotropy – and so colour our view of the entire universe...

This suggests that the age of the universe could be as much as 18.6 billion years in places where a low density of matter means the clock has ticked particularly fast. Our own smaller estimate of the universe's age is a natural consequence of sitting in an area of unusually high density: a galaxy.

Quantum theory reveals puzzling pattern in how people respond to some surveys

Quantum theory reveals puzzling pattern in how people respond to some surveys: The survey changed the order in which these questions were asked between respondents and, as expected, there were question-order effects found. When respondents were asked about Clinton first, 49 percent said that both Clinton and Gore were trustworthy. But when respondents were asked about Gore first, 56 percent said that both were trustworthy.

The pattern that quantum theory predicted – and that the researchers found – was that the number of people who switch from "yes-yes" to "no-no" when the question order is reversed must be offset by the number of people who switch in the opposite direction...

The researchers called this phenomenon "quantum question equality." They found it in every one of the surveys studied.

Ultrasonic imaging at 1,000 times times higher resolution | KurzweilAI

Ultrasonic imaging at 1,000 times times higher resolution | KurzweilAI: The researchers used a combination of subpicosecond laser pulses and unique nanostructures to produce acoustic phonons... at a frequency of 10 gigahertz (10 billion cycles per second).

By comparison, medical ultrasounds devices today typically reach a frequency of only about 20 megahertz...

“To generate 10 GHz acoustic frequencies in our plasmonic nanostructures we use a technique known as picosecond ultrasonics,” said author are Kevin O’Brien. “Sub-picosecond pulses of laser light excite plasmons which dissipate their energy as heat. The nanostructure rapidly expands and generates coherent acoustic phonons. This process transduces photons from the laser into coherent phonons.”

Impossible Cookware and Other Triumphs of the Penrose Tile - Issue 13: Symmetry - Nautilus

Impossible Cookware and Other Triumphs of the Penrose Tile - Issue 13: Symmetry - Nautilus: One of the curious aspects of aperiodic division of the plane is that information about positioning is somehow communicated across great distances—a Penrose tile placed in one position prevents the placement of other pieces hundreds (and thousands and millions) of tiles away. “Somehow a local constraint imposes a global constraint,” says Harriss. “You impose that at no scale will these tiles give you something that is periodic..."

It turns out crystals don’t always form atom-by-atom. “In very complex intermetallic compounds, the units are huge. It’s not local,” says Shechtman. When large chunks of crystal form at once, rather than through gradual atom accretion, atoms that are far apart can affect one another’s position, exactly as do Penrose tiles.

After 400 years, mathematicians find a new class of solid shapes

After 400 years, mathematicians find a new class of solid shapes: During the imagined bulging process, even one that involves replacing the bulge with multiple hexagons, as Craven points out, there will be formation of internal angles. These angles formed between lines of the same faces – referred to as dihedral angle discrepancies – means that, according to Schein and Gayed, the shape is no longer a polyhedron. Instead they claimed to have found a way of making those angles zero, which makes all the faces flat, and what is left is a true convex polyhedron...

A new topological insulator breaks symmetry, and that's a good thing

A new topological insulator breaks symmetry, and that's a good thing: Most topological insulators operate as either a p-type or n-type material on both top and bottom surfaces. But BiTeCl is asymmetric: p-type on its top surface and n-type on its bottom. This means the edges of the material could function as p-n junctions – or even many microscopic p-n junctions layered on top of each other. Even better, when the material is placed in a magnetic field, these p-n junctions develop unique edge channels that can conduct electricity with zero resistance, Chen said – and this opens all sorts of possibilities.

Moreover, this unique type of material can demonstrate many other phenomena. For instance, placing it in a static electric field can induce useful magnetic properties in the material, a phenomenon known as the topological magneto-electric effect, first predicted by theorist Shoucheng Zhang of the Stanford Institute for Materials and Energy Sciences and his group. You could even use an electric charge to induce magnetic monopoles – theorized magnets that have just one pole, north or south, rather than the usual two – and then use this exotic magnetic state to do practical work, such as storing information on a hard drive, Chen said. "This is very bizarre," he said, "because people have never found magnetic monopoles as fundamental particles."

Physicists Discover Geometry Underlying Particle Physics | Simons Foundation

Physicists Discover Geometry Underlying Particle Physics | Simons Foundation: The amplituhedron looks like an intricate, multifaceted jewel in higher dimensions. Encoded in its volume are the most basic features of reality that can be calculated, “scattering amplitudes,” which represent the likelihood that a certain set of particles will turn into certain other particles upon colliding.

Physicist proves impossibility of quantum time crystals

Physicist proves impossibility of quantum time crystals: Bruno explains that this proof should not come as a surprise, since a 1964 theory by another Nobel Laureate, Walter Kohn, shows that an insulator is completely insensitive to a magnetic flux. Since quantum time crystals are modeled as ring-shaped Wigner crystals, and Wigner crystals are insulators, attempting to show that a magnetic flux can cause such a system to rotate is, as Bruno writes, "a hopelessly doomed endeavor."

The Hunt for the Magnetic Monopole - IEEE Spectrum

The Hunt for the Magnetic Monopole - IEEE Spectrum: The team proposed looking for these trapped monopoles at temperatures close to absolute zero in spin ice, a peculiar class of materials with ions arranged in four-sided pyramids called tetrahedra. These tetrahedra are stacked together to make a crystal called a pyrochlore.

The atoms at each corner of the pyramids in a pyrochlore are magnetic dipoles. Just like a bar magnet, they have a magnetic field that emerges from one side (what physicists tend to call “north” by convention) and curves around the atom so that it eventually enters the opposite end (“south”)....

When the temperature of the crystalline material is relatively high, the forces that try to align the spins are easily overwhelmed by thermal fluctuations. The spins are oriented at random and can easily change direction. When the material is cooled to just a few degrees above absolute zero, the forces between spins begin to dominate...

In the case where ice rules are obeyed, the two north poles and two south poles cancel each other out. But here’s where it gets interesting: When the ice rules are not obeyed—if, for example, there are three spins pointing inward and one pointing outward—then the three north poles and one south pole in the center will give rise to a single, north magnetic pole.

Material low-temperature properties can be predicted from its symmetry

Material low-temperature properties can be predicted from its symmetry: In the 1960s, physicists derived a counting rule for relativistic systems—those in which particles travel at close to the speed of light. This rule, called the Nambu–Goldstone theorem, says that the number of allowed disturbances equals the number of symmetries broken in a phase transition.

Hidaka was interested in finding a more general version of this rule that would apply to non-relativistic systems like solids or liquids—something that theorists have been trying to do for 50 years. He succeeded by adapting a theory used to describe the statistical motion of particles.

Creating time crystals with a rotating ion ring

Creating time crystals with a rotating ion ring: The Berkeley team, led by Xiang Zhang and Hartmut Häffner, will attempt to build a time crystal by introducing 100 calcium ions into a 100-micron wide ion trap. The calcium ions will be confined by electric fields to form a crystalline ring, which will then be induced to rotate under the influence of a static magnetic field. According to the group's calculations, this ring should settle into the ground state when the atoms are pre-cooled with lasers to around one-billionth of a degree above absolute zero...


The experimental plan is to properly cool the chamber and then apply the proper magnetic fields. At this point, the ions should begin to cycle around their starting point at regular intervals, forming the repeating lattice of the time crystal. To observe this ion rotation, one of the 100 calcium ions will then be toggled into a new electronic state using a laser. If the scientists observe that ion rotating at steady state, they will have in effect, "broken the translational symmetry of time."

Blow for 'dark flow' in Planck's new view of the cosmos

Blow for 'dark flow' in Planck's new view of the cosmos: This flow suggested that the universe had somehow become lopsided, as if space-time itself was behaving like a tilted table and matter was sliding off...
The latest search is based on a new, higher-resolution map of the cosmic microwave background from Planck. The Planck team says their multi-pronged analysis also found no evidence of galaxy clusters gushing along in a coherent stream.

Planck shows almost perfect cosmos – plus axis of evil

Planck shows almost perfect cosmos – plus axis of evil: "The overall conclusion is that standard cosmology is an extremely good match to Planck data," said Efstathiou. "If I were an inflationary theorist I would be extremely happy."

...Planck reveals that one half of the universe has bigger variations than the other. Planck's detectors are over 10 times more sensitive and have about 2.5 times the angular resolution of WMAP's, giving cosmologists a much better look at this alignment. "We can be extremely confident that these anomalies are not caused by galactic emissions and not caused by instrumental effects..."

Solved? 80-year-old puzzle of the infinite sphere

Solved? 80-year-old puzzle of the infinite sphere: Would a basketball spinning on a fingertip behave the same way in an infinite number of dimensions? The question has flummoxed mathematicians for 80 years, but now it looks as if the answer is yes – a find that could have implications for quantum theory.