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| Issue 12, 2024 |
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Extracts from the Internet | ||
Check of Lorentz invariance1 November 2015In projects of the theories aimed at unification of the General Relativity and the Standard Model (for example, in string theories) Lorentz invariance is often violated, which can be expressed in dependence of the velocity of light on the direction. The violation is expected near the Planck energy, but its consequences, although in a suppressed form, must manifest themselves also at lower energies. The experiments checking Lorentz invariance beginning with the Michelson – Morley experiment have up to now confirmed Lorentz invariance. In the new experiment, M. Nagel (Humboldt University of Berlin, Germany) with colleagues attained the now record accuracy of ≈ 10-18 with which the violations could be noticeable already at ≈ 100 GeV. Compared were the electromagnetic oscillation frequencies in two cavities – sapphire crystals oriented at a right angle to each other. The crystals were placed in a vacuum chamber cooled from the outside by liquid helium. Stability of the frequency was restricted by the effect of external magnetic fields on the magnetic impurities in the crystals. The setup was rotated with a period of 100 seconds. If the velocity of light depended on the direction, rotations would induce periodic frequency shifts in the cavities and the beat frequency shifts in the resultant signal. The data accumulated during the year of experiment were analyzed. The frequency shift was not detected to a relative accuracy of (9.2 ± 10.7)×10-19. This constrains the parameters responsible for a possible Lorentz invariance violation. For different parameters the obtained restrictions were 4 to 20 times better than those of the preceding experiments. Source: Nature Communications 6 8174 (2015) Quantum entanglement discillation1 November 2015Quantum entanglement distillation may in future become an important element in quantum communications and calculations. This procedure consists in the fact that from a large ensemble of weakly entangled quantum states a smaller strongly entangled subsystem is singled out. A group of research workers including scientists from the Russian quantum center in Skolkovo, MIPT (Moscow Institute of Physics and Technology (State University) and P.N. Lebedev Physical Institute demonstrated the effect of quantum entanglement distillation for EPR pairs of photons. One of the photons from the EPR pair obtained in a nonlinear crystal was mixed with an auxiliary photon in a beam-splitting plate and then both photons of the EPR pair were registered by synchrotron detection. This way of entanglement distillation known as “quantum catalysis” was earlier proposed by A.I. L’vovskii and J. Mlynek. It is of importance that continuous quantum variables (field quadratures) were distilled, which gave some advantages over the case of discrete variables. The experimental method made it possible to restore the level of entanglement after its 20-time decrease upon a loss-inducing photon passage through the channel. Source: Nature Photonics 9 764 (2015) Motion of submicron particles by slowed-down light1 November 2015M.G. Scullion (York University, Great Britain) with colleagues worked out the method of dielectric particle motion about the photon crystal surface using slowed down light. The crystal was a triangular massif of holes in a silicon plate. The group velocity of light in it was 20 times lower than that in vacuum. The particle motion was induced by an evanescent field of an electromagnetic wave, the slowed down light having a stronger effect on particles than the ordinary light. The particle motion was traced by their fluorescent radiation, and the typical measured particle velocity made up 5 µm s-1 with a radiation power of 2.5 mW. This method may turn out to be useful for manipulations with microscopic objects, including microbiological objects. Source: Optica 2 816 (2015) Observation of coherent quantum states in proteins1 November 2015Almost 50 years ago H. Frolich predicted that protein molecule oscillations can become ordered and be condensed in a process resembling Bose – Einstein condensation. Parts of the molecules then behave as a group of coupled oscillators that can be condensed to a low-frequency mode. G. Katona (University of Gothenburg, Sweden) and his colleagues received the first experimental confirmation of this effect in a protein crystal. The lysozyme enzyme was examined which had been obtained from the hen-egg protein and was subjected to crystallization. The sample was exposed to terahertz radiation and was observed by the method of X-ray crystallography. Absorption of electromagnetic radiation with a frequency of 0.4 THz caused structure changes in the crystal, namely, collective excitations of regions of protein molecules. The excitation attenuation time was three to six orders of magnitude longer then in the case of ordinary thermal relaxation. This effect is best of all explained by condensation by the Frolich mechanism. Source: Struct. Dyn. 2 054702 (2015) Constrains on intergalactic magnetic fields by gamma-ray blazars1 November 2015Intergalactic magnetic fields have not yet been measured, and existent are only constrains on their possible values 10-16 G < B < 10-9 G. One of the promising methods of magnetic field study is the search for their effect on the motion of e+ and e- in electromagnetic cascades generated by primary gamma-ray emission of blazars (the class of galaxies with active nuclei) upon their interaction with intergalactic background radiation. J.D. Finke (Naval Research Laboratory, USA) with colleagues compared the spectra of five blazars obtained at high energies by ground-based detectors with their low-energy spectra measured by E. Fermi telescope. Low magnetic fields are excluded from the requirement that the cascade gamma-ray emission generated by e± under inverse Compton scattering by relic photons should not exceed the values measured by E. Fermi telescope. Thus, the restriction B > 10-19 G was obtained, the coherence length being > 1 Mpc at the confidence level of 5 σ. B has already been earlier restricted from below by another indirect method by the absence of observed gamma-ray halos around blazars - B> 10-16 G. Souece: arXiv:1510.02485 [astro-ph.HE] |
The Extracts from the Internet is a section of Uspekhi Fizicheskih Nauk (Physics Uspekhi) — the monthly rewiew journal of the current state of the most topical problems in physics and in associated fields. The presented News is devoted to the fundamental discoveries of physics and astrophysics. Permanent editor is Yu.N. Eroshenko. It is compiled from a multitude of Internet sources. | |
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