Nuclear and Atomic Physics


Matter-Antimatter Symmetry Test in Liquid Helium

Authors: George Rajna

Why is so much more matter than antimatter present in the universe? A clue to this mystery may be provided by a sensitive search for a separation of positive and negative charges inside the neutron, which is referred to as the neutron's "electric dipole moment" (EDM). [15] A multi-institutional team of researchers has discovered novel magnetic behavior on the surface of a specialized material that holds promise for smaller, more efficient devices and other advanced technology. [14] When light interacts with matter, it may be deflected or absorbed, resulting in the excitation of atoms and molecules; but the interaction can also produce composite states of light and matter which are neither one thing nor the other, and therefore have a name of their own – polaritons. These hybrid particles, named in allusion to the particles of light, photons, have now been prepared and accurately measured for the first time in the field of hard X-rays by researchers of DESY, ESRF in Grenoble, Helmholtz Institute in Jena and University of Jena. In the journal Nature Photonics, they describe the surprising discoveries they made in the process. [13] Condensed-matter physicists often turn to particle-like entities called quasiparticles—such as excitons, plasmons, magnons—to explain complex phenomena. Now Gil Refael from the California Institute of Technology in Pasadena and colleagues report the theoretical concept of the topological polarition, or " topolariton " : a hybrid half-light, half-matter quasiparticle that has special topological properties and might be used in devices to transport light in one direction. [12] Solitons are localized wave disturbances that propagate without changing shape, a result of a nonlinear interaction that compensates for wave packet dispersion. Individual solitons may collide, but a defining feature is that they pass through one another and emerge from the collision unaltered in shape, amplitude, or velocity, but with a new trajectory reflecting a discontinuous jump. Working with colleagues at the Harvard-MIT Center for Ultracold Atoms, a group led by Harvard Professor of Physics Mikhail Lukin and MIT Professor of Physics Vladan Vuletic have managed to coax photons into binding together to form molecules – a state of matter that, until recently, had been purely theoretical. The work is described in a September 25 paper in Nature.

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[v1] 2016-08-01 10:22:19

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