Pressure inside the proton
1 July 2018
The quark-gluon interactions inside a proton determine its mechanical properties, including the internal pressure. The pressure can be found from the experimental data on electron scattering by quarks inside a proton ep→e'p'γ and registration of outgoing particles by the coincidence method (the method of “deeply virtual Compton scattering”). Using the available data and applying the new computational approach, the researchers from Jefferson Laboratory (USA) V.D. Burkert, L. Elouadrhiri, and F.X. Girod determined the pressure as a function of the distance r to the proton center. At small r the pressure is positive, at r ≈ 0,6 fm it passes through zero, and farther becomes negative binding quarks in the proton. The
dependence p(r) is well consistent with the prediction of the quark-soliton model.
Source: Nature 557 396 (2018)
Neutrino oscillations in MiniBooNE experiment
1 July 2018
Reported are the new and most complete data obtained in MiniBooNE experiment at Fermilab (USA) on muon neutrino and antineutrino oscillations to the corresponding electron νe and anti-νe. A neutrino beam is generated in the interaction of protons with a beryllium target and is registered in a mineral-oil-filled detector through observing Vavilov – Cherenkov radiation and the scintillation signal. Confirmed was an excess of νe and anti-νe over their expected number at energies of 200 to 1250 MeV that had already been noticed before in LSND and MiniBooNE experiments. The LSND and MiniBooNE data together testify to the presence of the excessive events at the confidence level of 6.1 σ. This excess can be indicative of sterile neutrinos, but the result has not yet been confirmed in other neutrino experiments.
Source: arXiv:1805.12028 [hep-ex]
A test of the General Relativity Theory
1 July 2018
The researchers from the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder (USA) N. Ashby, T.E. Parker, and B.R. Patla performed a new test of the local position invariance principle which is a part of the equivalence principle and claims that nongravitational experiments conducted in differently located and oriented reference frames will give identical results. They examined stability of transition frequency between the levels of hyperfine splitting of H and Cs atoms for 14 years. During this time, the gravitational potential varies with distance of the Earth from the Sun upon its motion along the elliptic orbit. The gravitational field of Jupiter was also taken into account. The structure of H and Cs nuclei is different, and therefore they are convenient for seeking violations of the equivalence principle. The data on four hydrogen masers located in NIST and on eight cesium frequency standards at metrological laboratories in different countries were used. The obtained limit on the correction to the relative frequency shift β = (2.2 ± 2.5) × 10−7 is twice as good as the previous limits. Thus, no deviations from the General Relativity predictions have as yet been found.
Source: Nature Physics, online publication of June 4, 2018
A quantum Maxwell’s demon
1 July 2018
W.-B. Wang (Tsinghua University, China) with colleagues examined the quantum Maxwell’s demon (the thought experiment considered by Maxwell in 1867) realized on a nitrogen-substituted vacancy in a diamond (NV-center) in a magnetic field. The spin state in this quantum cell can be controlled by radio pulses, and the states were measured using quantum tomography. The demon’s memory coded by the electron spin was only 1 bit. It controlled the opening and closure of the logic cell. The measurements confirmed that in the general entropy balance the information contained in demon’s memory should be taken into account. In the second experiment, the demon was quantum entangled with the auxiliary system, i.e., the spin of 14N nucleus, and the important role of quantum entanglement in demon’s work was shown for the first time. Quantum entanglement can be interpreted as a reservoir with negative entropy in a quantum thermodynamic process.
Source: Chin. Phys. Lett. 35 040301 (2018)
A new component in electronics
1 July 2018
In usual bipolar and field-effect transistors, the input current or voltage control the output current, and to transfer the output current to the output voltage the load circuit is needed. S. Lee (Pusan University, South Korea) considered theoretically the new device in which input signals must directly control the output voltage. Although not yet realized in practice, the new active component is proposed to be referred to as the trancitor (transfer + capacitor). The trancitor may possibly be designed on the basis of the Hall effect. The combination of transistors and trancitors in electron devices may simplify considerably the circuit-creation technique and increase the device operation speed compared to the purely transistor circuits. By the calculations due to S. Lee the use of trancitors will change the empirical Moore’s law according to which the number of transistors in a microcircuitdoubles every 2 years.
Source: arXiv:1805.05842 [physics.app-ph]
Free energy from a nonequilibrium trajectory
1 July 2018
The fluctuation-dissipation theorems express the difference of equilibrium free energies of the system in final states in terms of its work upon nonequilibrium evolution. Measurement of the work typically encounters difficulties, but a method was proposed referred to as “relaxation fluctuation spectroscopy” in which the work need not be measured and the analysis of stochastic trajectories of the system under its relaxation is sufficient. D. Ross (NIST) et al. were the first to realize this method. In their experiment, a DNA molecule moved along a ladder-shaped substrate consisting of several stairs. Upon thermal fluctuations (Brownian motion) the molecule predominantly moved down the stairs, but sometimes it moved upwards. From the character of its motion, which was fixed by the fluorescence microscopy method, the probability distribution was found and the free energy measured.
Source: Nature Physics, online publication of May 28, 2018
Stars in distant galaxies
1 July 2018
The study of most distant galaxies provides insight into the physical conditions in the early Universe. T. Hashimoto (Osaka University and the National Astronomical Observatory of Japan) with colleagues used ALMA complex of radio telescopes (Chile) to perform spectroscopic observations of the gravitationally lensed galaxy MACS1149-JD1. The oxygen emission line with red shift z = 9.1096 ± 0.0006 was revealed in the far IR range. This made it possible to establish that the galactic spectrum reddening revealed earlier with the Spitzer telescope is due to the stars born at z ≈ 15, i.e., in the epoch when the Universe was about 250 mln years old, and two successive star formation episodes are needed to account for the spectrum shape.
Source: Nature 557 392 (2018)
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.