Monthly Archives: April 2014

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I started the blog on Bowler Hat Science to cover the writing I do at other sites, but to simplify matters, I’m going to move all that content over to my primary blog Galileo’s Pendulum. (This post has more on my reasoning for doing so, as well as a great song.) So, this is the last blog post here, though obviously the main part of the site — my portfolios and other professional information — will live on.

One blog fewer

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This metal plate is perforated with holes, each of which lines up with a galaxy or quasar. The BOSS survey maps the position and distance to a huge number of galaxies using many masks such as this. [Credit: moi]

This metal plate is perforated with holes, each of which lines up with a galaxy or quasar. The BOSS survey maps the position and distance to a huge number of galaxies using many masks such as this. [Credit: moi]

Far from being invisible, black holes are among some of the brightest objects in the Universe. The black holes themselves aren’t emitting light, but the matter they draw in heats up and much of it shoots back out in powerful jets. When that happens, the black hole is known as a quasar, and it can be visible from billions of light-years away. For that reason, mapping the distribution of quasars can help cosmologists understand the expansion rate of the Universe in an earlier era — and constrain the behavior of dark energy. My latest story in The Daily Beast explains:

If dark energy will be the same in billions of years as it seems to be today, the future will be dark and empty, as galaxies continue to move apart from each other at ever-faster rates. If dark energy comes and goes, though, maybe the rate of expansion will slow down again. All of this is a long time from now—trillions of years after the death of the Sun—but we might see hints about it today. We hope to see signs of what is to come by looking at how dark energy behaves now, and how it has acted in the past. Similarly, if dark energy is stronger in some parts of the cosmos, then certain pockets of the Universe would grow faster than in others. That also has implications for how the future cosmos looks. [Read more…]

Using Black Holes to Measure Dark Energy, Like a BOSS

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Captain Picard may be a little confused.

Today, researchers with the LHCb experiment at CERN announced the confirmation of a weird object that first appeared in detectors in 2008. This object is made up of four quarks, where other particles are made of two or three quarks (or zero, in the case of electrons, neutrinos, and the like). But what sort of beast is this? As is often the case, more work is needed before we can say for ccertain.

With that much data, physicists were able to determine the composition of the Z(4430)–: it consists of a charm quark, a charm anti-quark, a down quark, and an up antiquark. The “4430” part of the name indicates its mass: 4,430 million electron-volts, which a little more than four times the mass of a proton (938 million electron volts). The combination of quarks gives the Z(4430)– a negative electric charge, hence the “-” in the label. The particle is highly unstable, so none of them are expected to be seen in nature. [Read more…]

Four quarks for Muster Mark!

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Artist's impression of the ringed asteroid Chariklo. While the asteroid is too small and distant to image directly, astronomers found two narrow rings around it — making it the smallest known object with a ring system. [Credit: ESO/L. Calçada/M. Kornmesser/Nick Risinger (skysurvey.org)]

Artist’s impression of the ringed asteroid Chariklo. While the asteroid is too small and distant to image directly, astronomers found two narrow rings around it — making it the smallest known object with a ring system. [Credit: ESO/L. Calçada/M. Kornmesser/Nick Risinger (skysurvey.org)]

Saturn’s magnificent rings have been known since Galileo observed the planet’s “ears” in his telescope. In the last few decades, researchers found rings (albeit less shiny ones) around the other giant planets — Jupiter, Uranus, and Neptune. And now the small asteroid Chariklo has joined the ring cycle: observations revealed it has two narrow rings, probably composed of water ice. It’s an intriguing discovery, since nothing else we’ve found at intermediate sizes has rings, leading to questions of how they form, how stable they may be, and whether there might be other beringed objects out there.

Beyond size, another challenge is Chariklo’s location between Saturn and Uranus. It orbits in a long ellipse, ranging from 13 to nearly 19 times farther from the Sun than Earth. This position, along with its composition of rock and ice, marks Chariklo as a “centaur.” Just like mythological centaurs are half human and half horse, astronomical centaurs combine features of asteroids and comets. (Centaurs would grow comet-like tails if they fell closer toward the Sun.) Tens of thousands of centaurs may lurk among the giant planets, though most of those are much smaller than Chariklo, the largest known centaur. [Read more…]

All the single centaurs

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The particles of the the Standard Model and its simplest supersymmetric version. [Credit: Pauline Gagnon]

The particles of the the Standard Model and its simplest supersymmetric version. [Credit:
Pauline Gagnon]

Symmetry and elegance have proven to be a very successful way to think about the physical Universe. Arguably the greatest successes in 20th century particle physics came from translating mathematical symmetries into predictions about the results of particle collisions. However, not every symmetry thus far has led to a successful theory, and one of the frustrations is that a natural consequence of a symmetry in the theory of relativity hasn’t produced the predicted particles. The currently unfulfilled theory is known as supersymmetry (or SUSY), and so far none of its predictions have borne out experimentally.

However, a completely analogous version of SUSY could exist in certain exotic superconductors. This is not built out of elementary particles, but out of interactions between electrons and atoms, giving rise to a set of particle-like quantum excitations known as quasiparticles.

The new paper discussed the idea of emergent SUSY-like behavior in topological superconductors. In these systems (described in more detail in the sidebar story), the interior of the material conducts electricity without resistance, but the outside is an ordinary conductor. The authors argued that experimentally observed magnetic behavior on the conducting surface could be interpreted super symmetrically. It also exhibits a breaking of SUSY due to the fundamental difference in interior and surface behavior of the system.

In this view, the magnetic excitations (acting like bosons) on the surface are SUSY partners with the topological superconductor quasiparticles, which are fermions. [read more…]

Supersymmetry in…superconductors?