Russian physicists from VNIIFTRI SINP MSU and ITEP studied the acoustic effects from entry bunch of electrons in a substance. Interest in him is linked with the possibility of acoustic detection of ultrahigh-energy cosmic neutrinos.
Neutrino – trudnoulovimye most of the known elementary particles. Neutrino detectors (often called neutrino telescopes) are the big tanks of water (or ice, for example, IceCube in Antarctica), in which the many “electronic eyes” – photomultiplier. These detectors are so deep under the ground (under water, under the Antarctic ice), that no other particles, except neutrinos, they can not reach.

The vast majority of neutrinos pass a detector thoroughly, leaving no trace, and only rarely are they the same? Face? on matter, it turns into electrons. If the original neutrinos possess great energy, this electron generates electromagnetic downpour – the flow of electrons and positrons lesser energy. When driving through water, they are due to Cherenkov radiation, provides a flash of light, which registers and photomultiplier. After processing the data from all photomultiplier can restore full brightness of the flash, hence the total energy of a downpour, and the mean energy of the original neutrino.

This method of “catch” neutrinos have long-established and well-proven, but it has one major drawback (as with most experiments on registration of elementary particles): it uses very expensive equipment. Therefore, it would be interesting to find a different, simpler and cheaper way to record and evaluate their neutrino characteristics.

Some time ago there was an idea that could help in this … sound beams of elementary particles during their movement through the material. This idea immediately gained many supporters (see bibliography on acoustic detection of neutrinos, a thesis on the topic pages and projects SAUND and ACORNE, which will be implemented this idea).

Indeed, appeared suddenly in the water and high-energy electrons generated by electromagnetic downpour they not only lead to ionization and radiation, but also caused a sharp point on the water? Attack inside?. As it was predicted even a half-century ago, the Soviet physicist Gurgenom Askaryanom (Gurgen_Askaryan), this attack is a short sound in kilogertsevom range, which means that it can register a conventional hydrophone, which was done a couple of decades later (though in these experiments were used proton beams).

To use this effect in neutrino telescopes alone the knowledge that the “flying neutrinos,” is not enough. Preferably, for example, find out how “sound” of electrons depends on the neutrino energy and direction of its arrival. In other words, the need for a systematic study of acoustic effects with the passage of electron bunches through the water.

Researchers from the Research Institute of Nuclear Physics. DV Skobeltsyna (SINP MSU), the Institute of Theoretical and Experimental Physics. AI Alikhanova (ITEP) and the All-Russia Research Institute of Physical-Technical and Radio Engineering Measurements (VNIIFTRI) that, in the village near Moscow Mendeleevo, took up this challenge. Their initial results are described in a recent e-print physics/0610241. Physics conducted a simple experiment: water-bombing cell clot and studied the electronic dissemination of the chamber erupted in sound waves. Electronic clots contain approximately 1011 particles with an energy of 50 MeV in the particle and simulated a well-developed electromagnetic shower, which could arise from the ultrahigh-energy neutrinos coming to us from deep space.

It was found that the electron beam enters the water, produces a sound – or rather, a click – in two stages: immediately at the site entrance on Wednesday and then along its trajectory. As a result, the sound vibrations constitute the imposition of hemispherical waves, going from the wall at the site entrance beam, and cylindrical waves, divergent from the channel through which it passed. Using the analogy of electrodynamics, one can say that the click was able to decompose into two components: transitional acoustic radiation at the entrance of air into the water and its own radiation electron bunch when it moves in the water. The authors note that the imposition of these sound waves leads to an interesting acoustic interference effects, and plan to study them in detail.

The next step after being subjected to the methodology should be checking how the “e-click” change with the change of energy and the number of electrons. If the unique relationship between these variables is proved, then physics, working on the neutrino telescopes will be available to new, much cheaper method of studying neutrinos. However, remember that it can help only if the registration is very high-energy neutrinos.

Scientists from the Low Temperature Laboratory of Helsinki University of Technology investigated the heat transfer between two small metal samples, coupled superconductor. They found that at very low temperatures heat is distributed via electromagnetic radiation, reported EurekAlert.

Dr. Matthias Bags (Matthias Meschke), prof. Jukka Pekola (Jukka Pekola) and their colleagues studied the spread of heat in the micro-devices and nanorazmera based on conventional silicon chips, at a temperature of 0.1 degrees above absolute zero. During the study, scientists found that at very low temperatures heat is distributed through the superconductor through the electromagnetic radiation. At the same coefficient of thermal conductivity can only accept a strictly defined quantum values.

To measure the temperature of the sample, which is only 100 nm in cross section, fixed tunneling current from its surface. As the value of tunneling current determines the distribution of energy and temperature of electrons.

The fundamental phenomenon that scientists watched, does not have immediate practical applications. However, this effect should be taken into account in the design of sensitive radiation detectors for astronomical observations, for which work at very low temperatures will significantly influence the heat exchange with the environment.

Lianksing Wen (Lianxing Wen) from the New York University (State University of New York at Stony Brook) showed that the internal radius of the solid core of Earth grew over a decade for one – one and a half kilometers (0,98 – 1,75 km), at least in one area – under the central Africa. The basis for such finding were data from two earthquakes in 1993 and 2003 in the area of the South Sandwich Islands.

It turned out that the seismic waves generated by earthquakes and reflected from the surface of inner core in 2003, reached the three seismic stations in Russia and Kyrgyzstan on 39 – 70 milliseconds faster than in 1993.

This suggests a local increase in the radius of inner core in the area, located midway between the epicenter of the earthquake and seismic stations, which is under central Africa. It is believed that the growth of inner core occurs due to hardening of internal layers of the molten outer core.

Local changes in the radius of inner core may be explained not only by its “growth” but also that the inner core may have rough surface with protrusions and depressions.

Some data indicate that the inner core rotates about the Earth’s outer layers. Therefore, the observed effect could be explained by the fact that the nucleus for 10 years, turned in such a way that, under central Africa to be more “elevated” station. That was reported by Radio Liberty.