 |
RSS feeds |
|
|||||
| Issue 11, 2024 |
|
||||||
|
|
|
||||||
Extracts from the Internet | ||
Possible observation of the Higgs boson1 August 2012ATLAS and CMS collaborations presented the latest LHC data supporting the discovery of a particle whose properties correspond to predictions for the Higgs boson. The Higgs boson is a quantum of the Higgs field which imparts mass to particles in the process of spontaneous breaking of gauge symmetry. The sighting of the Higgs boson would bring to completion the experimental confirmation of the Standard Model of elementary particles in which only the Higgs boson remained unconfirmed among all the predicted particles. The confidence level of the discovery of the new short-lived boson — which may indeed prove to be the missing Higgs boson — is about 5 σ at the mass of 125-126 GeV/ñ2; the data in various decay channels are in good agreement. Even though the confidence level of confirmation is sufficient for announcing a discovery, it cannot be excluded that as new data is stored and processed, some correction may become necessary. Source: CERN Press Release M-modification of carbon1 August 2012The experiment conducted by Y. Wang (Yale University, USA) et al. confirmed that cold compression at room temperature transforms graphite into crystalline M-carbon modification whose existence was predicted in 2006. This transition is due to the destruction of π bonds between atoms and the formation of new σ bonds. The work used x-ray diffraction techniques and Raman spectroscopy. Such structural changes in carbon in the course of cold compression were observed previously but it was impossible to establish which specific modification of carbon had been produced. Theoretical calculations predicted about a dozen possible outcomes. The structural transition in the new experiment occurred at 19.2 GPa, and the relaxation to the new state lasted for several hours. According to the totality of the data, the compression created Ì-carbon while all other suggested modifications are ruled out. In contrast to diamond, the synthesis of M-carbon requires compression only and heating is not needed; note that the hardness of M-carbon thus obtained equals that of diamond. Source: Scientific Reports 2 520 (2012) Giant spin Seebeck effect1 August 2012The phenomenon known as the spin Seebeck effect (discoverd in 2008 by researchers of Tohoku University (Japan)) consists in temperature gradient causing spin current. Previously, this effect was observed only in materials with magnetic ordering (ferromagnets, semiconductors and insulators). In the new experiment Ñ.Ì. Jaworski (Ohio University) and his colleagues observed the spin Seebeck effect of very large magnitude in a nonmagnetic material. The measurements were performed at temperatures of 2-20 K in 3 T magnetic field on a specimen of semiconducting InSb doped with tellurium atoms. The Seebeck effect in InSb is greater by three orders of magnitude (8 mV/K) than in other known materials, hence it was given the name “giant spin Seebeck effect”. The authors of the experiment believe that the effect is so large because electron-phonon interactions enhance the spin-orbital interaction of electrons. The observed effect may lead to the creation of efficient thermoelectric generators. Source: Nature 487 210 (2012) Superconducting parametric amplifier1 August 2012Precision measurements require good amplifiers of electric signals. Alas, transistor amplifiers, even cryogenic ones, are characterized by significant intrinsic noise, while the dynamic range and bandwidth of parametric amplifiers designed so far were too narrow. Researchers at the California Institute of Technology and NASA Jet Propulsion Laboratory constructed a new superconductor-based parametric amplifier in which all these shortcomings have been largely eliminated. Amplification is produced in a nonlinear kinetic inductance in the superconducting transmission line. This nonlinearity arises as current approaches the critical value, as predicted in both the Ginzburg – Landau and the BCS theories. The amplifier design is based on a superconducting 0.8 m long NbTiN helix through which are passed the mixture of the pump signal and the signal to be amplified. Nonlinearity produces additional phase shift which results in parametric amplification. The gain in the frequency range of 8-14 GHz reaches 20 dB, while the noise level is only 3.4 photons, which is close to the quantum limit due to the zero-point fluctuations. Operating frequency of amplifiers built using this concept may in the future reach ≈ 1 THz. The amplifier was designed primarily to boost very weak signals in radio astronomy, but may find applications in quantum mechanics experiments owing to its extremely low noise. Source: Nature Physics 8 623 (2012) Dark galaxies1 August 2012Direct observations of small dark galaxies at redshifts z > 2 were carried out for the first time using the 8.2-meter VLT telescope of the European Southern Observatory in Chile. Their masses are ≈ 109 M☉ and mostrly consist of dark matter and gas with a small number of stars. In the past only indirect evidence of their existence was detected in absorption lines in the spectra of quasars. New observations using the VLT recorded fluorescent Lyα-gas emission in twelve such galaxies. The emission is caused by the radiation from the quasar ÍÅ 0109-3518 at redshift z = 2.4. The quasar illuminates nearby galaxies and the gas contained in them re-emits the incident light in the process of fluorescence. To isolate this weak signal against the noisy the background, a frequency filter with narrow transmission band was used. The rate of star formation in these galaxies is about 100 times slower than in typical galaxies of the same era. Source: arXiv:1204.5753v2 [astro-ph.CO] |
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. | |
|
© 1918–2024 Uspekhi Fizicheskikh Nauk Email: ufn@ufn.ru Editorial office contacts About the journal Terms and conditions |