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Showing 1–5 of 5 results
Advanced filters: Author: L. Tibaldo Clear advanced filters

  • A recent survey suggests that reducing the number of meetings and conferences is a viable way to address concerns about the effectiveness of the modern scientific collaboration process, its effects on the environment and the well-being of the community.

    • L. Tibaldo
    • E. Prandini
    • A. Nelles
    Comments & Opinion
    Nature Astronomy
    Volume: 7, P: 1408-1411

  • Lorentz invariance — the postulate that all observers measure exactly the same speed of light in vacuum, independent of photon energy — is a cornerstone of Einstein's special relativity, but it has been suggested that it might break near the Planck scale. A possible variation of photon speed with energy is a key test for this proposed violation; here, by studying sharp features in γ-ray burst light-curves to look for even tiny variations in photon speed, no evidence for the violation of Lorentz invariance is found.

    • A. A. Abdo
    • M. Ackermann
    • M. Ziegler
    Research
    Nature
    Volume: 462, P: 331-334

  • It is widely accepted that strong and variable radiation detected over all accessible energy bands in a number of active galaxies arises from a relativistic, Doppler-boosted jet pointing close to our line of sight. However, the size of the emitting zone and the location of this region relative to the central supermassive black hole are poorly understood. Here, the coincidence of a γ-ray flare with a dramatic change of optical polarization angle is reported, providing evidence for co-spatiality of optical and γ-ray emission regions and indicating a highly ordered jet magnetic field.

    • A. A. Abdo
    • M. Ackermann
    • M. Sikora
    Research
    Nature
    Volume: 463, P: 919-923

  • Cosmic Rays (CRs) with energy below 1 PeV are believed to originate in the Milky Way, but recent gamma-ray observations by Fermi Large Area Telescope challenge the interpretation of CR diffusion mechanisms across the galaxy. The authors propose that a harder-than-expected slope of the diffuse gamma-ray emission spectrum in the inner Galaxy may be due to unresolved sources, suggested to be TeV-bright pulsar wind nebulae.

    • Vittoria Vecchiotti
    • Giulia Pagliaroli
    • Francesco Lorenzo Villante
    ResearchOpen Access
    Communications Physics
    Volume: 5, P: 1-9