Cosmological implications of Higgs near-criticality

The Standard Model electroweak (EW) vacuum, in the absence of new physics below the Planck scale, lies very close to the boundary between stability and metastability, with the last option being the most probable. Several cosmological implications of this so-called ‘near-criticality’ are discussed. In the metastable vacuum case, the main challenges that the survival of the EW vacuum faces during the evolution of the Universe are analysed. In the stable vacuum case, the possibility of implementing Higgs inflation is critically examined. This article is part of the Theo Murphy meeting issue ‘Higgs cosmology’.

Asymptotical null structure of an electro-vacuum spacetime with a cosmological constant

Bondi–Sachs (BS) framework is a powerful tool to analyze the asymptotical null structure of a spacetime. Based on Bondi’s outgoing boundary condition, the asymptotical null structure of an electro-vacuum spacetime without a cosmological constant has been constructed clearly. Recently more and more observations imply that the Einstein equation should be modified with an nonzero cosmological constant. It is interesting to investigate the asymptotical null structure of a spacetime with a cosmological constant. In this paper, we extend our previous result from vacuum case to electro-vacuum case. We find that the gravitational sector of the asymptotical null structure depends strongly on the boundary conditions, while the electrical sector is independent of the boundary condition.

Testing of the Superconducting Magnet and Cryogenics for the AMS-02 Experiment

The superconducting magnet, cryogenics, and detector systems of the AMS experiment was fully integrated and tested in test beam at CERN during 2009. In Spring 2010 the experiment underwent thermal vacuum tests at ESTEC, where it was operated in conditions simulating those that will pertain in orbit. All elements of the superconducting magnet and cryogenics performed as designed, and equilibrium operation was attained at several values of vacuum case temperature. Details of the tests are presented. A thermal model of the overall cryogenic system was calibrated from those measurements. The model was used to predict the cryogenic lifetime of the experiment, as it would be staged on ISS, to be (28 ± 6) months.

HYDRODYNAMICS OF THE VACUUM

Hydrodynamics is the appropriate "effective theory" for describing any fluid medium at sufficiently long length scales. This paper treats the vacuum as such a medium and derives the corresponding hydrodynamic equations. Unlike a normal medium the vacuum has no linear sound-wave regime; disturbances always "propagate" nonlinearly. For an "empty vacuum" the hydrodynamic equations are familiar ones (shallow water-wave equations) and they describe an experimentally observed phenomenon — the spreading of a clump of zero-temperature atoms into empty space. The "Higgs vacuum" case is much stranger; pressure and energy density, and hence time and space, exchange roles. The speed of sound is formally infinite, rather than zero as in the empty vacuum. Higher-derivative corrections to the vacuum hydrodynamic equations are also considered. In the empty-vacuum case the corrections are of quantum origin and the post-hydrodynamic description corresponds to the Gross–Pitaevskii equation. We conjecture the form of the post-hydrodynamic corrections in the Higgs case. In the (1+1)-dimensional case the equations possess remarkable "soliton" solutions and appear to constitute a new exactly integrable system.