Volume 6 Issue 7, July 2010

Volume 6 Issue 7

A dye-filled optical microresonator can trap photons such that their number doesn't decrease even when the 'white box' is cooled. An intriguing consequence is that light becomes concentrated in the centre of the confining potential. Such photon thermalization is an important step towards a Bose—Einstein condensate of light. Letter p512 Cover design by David Shand

Editorial

  • Editorial |

    At a time when no extra money is likely to be forthcoming, those appointed to lead European-Union-funded science must follow a more imaginative plan.

Thesis

Research Highlights

News and Views

  • News & Views |

    The critical point of a fluid is defined as the point beyond which it ceases to exhibit distinct liquid- or gas-like states. A crossover between liquid-like and gas-like behaviour observed by inelastic X-ray scattering suggests subtle effects involving nanoscale fluctuations in the one-phase region above the critical point.

    • Paul F. McMillan
    •  & H. Eugene Stanley
  • News & Views |

    The Turing mechanism provides a paradigm for the spontaneous generation of patterns in reaction–diffusion systems. A framework that describes Turing-pattern formation in the context of complex networks should provide a new basis for studying the phenomenon.

    • Romualdo Pastor-Satorras
    •  & Alessandro Vespignani
  • News & Views |

    The orientation of the magnetic field wrapped around a galaxy cluster has been measured for the first time, through a previously unexplored combination of traditional astronomy and computer simulations.

    • Ian Parrish
  • News & Views |

    Confinement of helium in a micrometre-size box rounds the sharp transition and depresses the specific-heat maximum. But coupling an array of boxes through a thin, non-superfluid film is now shown to raise that maximum, while the boxes also enhance superfluidity in the film.

    • Michael E. Fisher
  • News & Views |

    Experiments aimed at finding Einstein's elusive gravitational waves have reached their designed sensitivity. Yet we are still waiting for the first detection. What can we learn from this?

    • Nils Andersson
  • News & Views |

    The optical spectrum of a single quantum dot is strongly affected by coherent tunnelling to a nearby sea of electrons.

    • Alex Greilich
    •  & Daniel Gammon
  • News & Views |

    The process of diffusion isn't usually expected to be able to generate useful work. But when a neutrally buoyant wedge object is placed in a fluid with a vertical density gradient, the diffusion-driven flow of material can indeed generate a measureable horizontal propulsion.

    • Michael A. Page

Letters

  • Letter |

    Luttinger-liquid theory describes interacting electrons in one dimension, so long as their energies are linear as a function of momentum. When the energies become nonlinear, particles and holes behave differently, with particles able to relax when injected into a quantum wire.

    • Gilad Barak
    • , Hadar Steinberg
    • , Loren N. Pfeiffer
    • , Ken W. West
    • , Leonid Glazman
    • , Felix von Oppen
    •  & Amir Yacoby
  • Letter |

    Some effects that have long been observed in superconductors are difficult to see in superfluid helium-4, despite the similar physics governing these systems, owing to the small correlation length in helium-4. Proximity effects have now been observed in that system, using an array of micrometre-size boxes linked by a thin helium film.

    • Justin K. Perron
    • , Mark O. Kimball
    • , Kevin P. Mooney
    •  & Francis M. Gasparini
  • Letter |

    By conventional definition, a supercritical fluid is one that doesn’t exhibit distinct liquid- or gas-like states. This may need to be revised in light of measurements that show a sharp change in the speed of sound in supercritical argon when it crosses a well-defined line on its pressure versus temperature phase diagram.

    • G. G. Simeoni
    • , T. Bryk
    • , F. A. Gorelli
    • , M. Krisch
    • , G. Ruocco
    • , M. Santoro
    •  & T. Scopigno
  • Letter |

    Interatomic Coulombic decay is a recently discovered ionization process by which energy absorbed from incident radiation by one atom is rapidly transferred to another. A study of this process in helium now shows that it can operate over remarkably long distances of more than 45 atomic radii.

    • Nicolas Sisourat
    • , Nikolai V. Kryzhevoi
    • , Přemysl Kolorenč
    • , Simona Scheit
    • , Till Jahnke
    •  & Lorenz S. Cederbaum
  • Letter |

    Few would expect the process of diffusion to generate useful work. But when a buoyant wedge-shaped object is placed in a fluid with a vertically stratified density gradient, the upward flow driven by diffusion can be translated into a measurable horizontal propulsion.

    • Michael R. Allshouse
    • , Michael F. Barad
    •  & Thomas Peacock

Articles

  • Article |

    Large clusters of galaxies are cosmologically significant, and their thermal history is determined by magnetic fields. Simulations show that the magnetic-field lines in the Virgo cluster, rather surprisingly, are oriented radially. This would explain the observed ridged structure. Moreover, the model may explain why some clusters have not cooled as expected.

    • Christoph Pfrommer
    •  & Jonathan Dursi
  • Article |

    Similar to atoms in cold gases, exciton–polaritons in semiconductor microcavities can undergo Bose–Einstein condensation, but under non-equilibrium conditions. Now, quantized vortices and persistent currents — hallmarks of superfluid behaviour — have been observed in such condensates.

    • D. Sanvitto
    • , F. M. Marchetti
    • , M. H. Szymańska
    • , G. Tosi
    • , M. Baudisch
    • , F. P. Laussy
    • , D. N. Krizhanovskii
    • , M. S. Skolnick
    • , L. Marrucci
    • , A. Lemaître
    • , J. Bloch
    • , C. Tejedor
    •  & L. Viña
  • Article |

    Despite all of the fundamental research carried out on them, artificial atoms continue to be a source of surprise. The intersection between the electrons in a quantum dot and a nearby sea of electrons can create unusual many-body states. A spectroscopic study now makes these states observable.

    • N. A. J. M. Kleemans
    • , J. van Bree
    • , A. O. Govorov
    • , J. G. Keizer
    • , G. J. Hamhuis
    • , R. Nötzel
    • , A. Yu. Silov
    •  & P. M. Koenraad
  • Article |

    Networks have been widely explored in the context of classical statistical mechanics. But when quantum effects are added, qualitatively different behaviours emerge, even for the simplest cases.

    • S. Perseguers
    • , M. Lewenstein
    • , A. Acín
    •  & J. I. Cirac
  • Article |

    Differences in diffusion constants of activator and inhibitor species can destabilize biological and chemical processes, leading to the spontaneous emergence of periodic spatial patterns. A general framework now provides the tools for studying such so-called Turing patterns in systems organized in complex networks.

    • Hiroya Nakao
    •  & Alexander S. Mikhailov

Addendum

Correction

Addendum