Physics at 17 January 2013


Pulsed accretion in a variable protostar (see also: ulaulaman’s island)
James Muzerolle et al.
First Paragraph | Full Text | PDF

Planetary system disruption by Galactic perturbations to wide binary stars
Nathan A. Kaib, Sean N. Raymond & Martin Duncan

Nearly half the exoplanets found within binary star systems reside1 in very wide binaries with average stellar separations greater than 1,000 astronomical units (one astronomical unit (AU) being the Earth–Sun distance), yet the influence of such distant binary companions on planetary evolution remains largely unstudied. Unlike their tighter counterparts, the stellar orbits of wide binaries continually change under the influence of the Milky Way’s tidal field and impulses from other passing stars. Here we report numerical simulations demonstrating that the variable nature of wide binary star orbits dramatically reshapes the planetary systems they host, typically billions of years after formation.
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Towards an exact description of electronic wavefunctions in real solids
George H. Booth et al.

The properties of all materials arise largely from the quantum mechanics of their constituent electrons under the influence of the electric field of the nuclei. The solution of the underlying many-electron Schrödinger equation is a ‘non-polynomial hard’ problem, owing to the complex interplay of kinetic energy, electron–electron repulsion and the Pauli exclusion principle. The dominant computational method for describing such systems has been density functional theory.
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Efimov effect in quantum magnets
Yusuke Nishida, Yasuyuki Kato & Cristian D. Batista
Nature Physics

Physics is said to be universal when it emerges regardless of the underlying microscopic details. A prominent example is the Efimov effect, which predicts the emergence of an infinite tower of three-body bound states obeying discrete scale invariance when the particles interact resonantly.
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Exotic non-Abelian anyons from conventional fractional quantum Hall states
David J. Clarke, Jason Alicea, Kirill Shtengel
Nature Communications

Non-Abelian anyons—particles whose exchange noncommutatively transforms a system’s quantum state—are widely sought for the exotic fundamental physics they harbour and for quantum computing applications. Numerous blueprints now exist for stabilizing the simplest type of non-Abelian anyon, defects binding Majorana modes, by interfacing widely available materials.
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Spin imbalance and spin-charge separation in a mesoscopic superconductor
C. H. L. Quay et al.
Nature Physics

What happens to spin-polarized electrons when they enter a superconductor? Superconductors at equilibrium and at finite temperature contain both paired particles (of opposite spin) in the condensate phase as well as unpaired, spin-randomized quasiparticles. Injecting spin-polarized electrons into a superconductor (and removing pairs) thus creates both spin and charge imbalances, which must relax when the injection stops, but not necessarily over the same time (or length) scale. These different relaxation times can be probed by creating a dynamic equilibrium between continuous injection and relaxation; this leads to constant-in-time spin and charge imbalances, which scale with their respective relaxation times and with the injection current.
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Entropy favours open colloidal lattices
Xiaoming Mao, Qian Chen & Steve Granick
Nature Materials

Burgeoning experimental and simulation activity seeks to understand the existence of self-assembled colloidal structures that are not close-packed.
First Paragraph | Full Text | PDF


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