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| Issue 1, 2026 |
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Extracts from the Internet | ||
Interaction of solar neutrinos with 13C1 January 2026A flux of boric neutrinos νe from the Sun has already been registered in experiments in the channel of neutral currents and also by elastic scattering. Interactions of solar boric νe with 13C nuclei were recorded for the first time by the underground SNO+ detector (Sudbury, Canada) in the charged current channel [1]. The detector contains 800 tons of liquid scintillator viewed by 9000 photomultipliers. Electrons and positrons from successive 13C+νe → 13N+e− and 13N → 13C+e++νe reactions were singled out by the coincidence method. The registration is significant up to 4.2σ, and the measured cross section of the νe interaction with 13C with the formation of 13N at the ground energy level corresponds to theoretical calculations. The obtained results are completely consistent with the standard model of the Sun with allowance for neutrino oscillations. The interaction between Earth-origin νe and 13C has already been analyzed in the KARMEN experiment (Karlsruhe, Germany), but for much higher energies and totally for all the levels of the 13N nucleus. [1] Abreu M et al. Phys. Rev. Lett. 135 241803 (2025) Einstein—Bohr experiment with a movable slit1 January 2026In the 1927 debates of A Einstein with N Bohr, an idea was born to supplement the interferential double-slit experiment with an additional movable slit. Then, the scattered photon momentum might be measured by movable slit recoil momentum. Such a thought scheme could not be reproduced earlier. Y-C Zhang (University of Science and Technology of China) and his co-authors were the first to conduct an experiment, fully realizing the Einstein-Bohr idea [2]. The role of a movable photon-scattering slit was played by a single 87Rb atom trapped by an optical tweezer. The atom was cooled by the Raman scattering method in a lateral band, and the uncertainty of its momentum in the ground state was comparable with the single photon momentum, which is inadmissible for macroscopic objects. With weakening the atom fixation force in the trap, the single photon behavior changes from wave to corpuscular. This confirmed N Bohr’s explanation: upon momentum measuring, the information on slit position is lost and the interference pattern smears out. According to the authors of paper [2], in future experiments of the kind, an increase in the mass of an object, which is a mobile slit, will make it possible to analyze the interrelation between decoherence and quantum entanglement. [2] Zhang Y-C et al. Phys. Rev. Lett. 135 230202 (2025) Superion Fe-C alloy at high pressures1 January 2026Y Huang (Sichuan University, China) and their co-authors examined the iron-carbon alloy under conditions close to those in the Earth’s inner core [3]. Upon collision at a velocity of 77 km s−1 of a shell onto an iron-carbon sample, a pressure of 140 GPa and a temperature of 2600 K were reached. The measurements showed that the hexagonal closely packed Fe-C (the carbon mass fraction ≈ 1.5 %) alloy appearing under these conditions has a superion (intermedium between liquid and a solid crystal) character, where carbon atoms can flow relative to the iron, the shear wave velocity Vs is lower by 23 % than in pure iron, and the Poisson ratio has a high value μ =0.43. The superion Fe-C alloy with such characteristics was theoretically proposed earlier to explain the data of seismic observations of Earth’s inner core. Thus, the experiment [3] yields a weighty confirmation of the superion model. The Earth core mainly consists of an iron-nickel alloy with an impurity of C, O, and H. The diffusion of light elements through iron in a superion alloy is important for understanding the state and dynamics of the Earth core, in particular, the moving mechanisms of geodynamo – the magnetic field generation. [3] Huang Y et al. National Science Review 12 nwaf419 (2025) Realization of the Letokhov-Chebotaev spectroscopic method1 January 2026One of the main problems in spectroscopy of atoms and molecules is the Doppler frequency shift due to particle motion [4]. To solve this problem, for example, two-photon transitions in the field of colliding laser beams are applied. The method for weakening the influence of the Doppler effect through capture of molecules was applied. In their papers [5, 6], Letokhov and Chebotaev developed a method for weakening the influence of the Doppler effect through capture of molecules in an electromagnetic standing-wave field in a cavity. The particle must either have a low absolute velocity or move at a very small angle to the wave front. This method was demonstrated by W Ubachs (Free University Amsterdam, Netherlands) and their co-authors for H2 molecules in the cavity [7]. Optical heterodyne spectroscopy was used to examine a weak quadrupole overtone transition S(0)(2-0) in H2. The measured transition width was four orders of magnitude less than the Doppler broadening, which shows a successful realization of the Letokhov-Chebotaev method. The demonstrated effect of 1D trapping of molecules may become a part of the instruments of precision molecular spectroscopy. [4] Letokhov V S, Chebotaev V P Sov. Phys. Usp. 17 467 (1975); UFN 113 385 (1974) [5] Letokhov V S, JETP Letters 7 272 (1968) [6] Letokhov V S, Chebotayev V P, Nonlinear Laser Spectroscopy, Springer Series in optical sciences, Vol. 4 (Springer Verlag, 1977). [7] Ubachs W et al. Phys. Rev. Lett. 135 223201 (2025) New cosmological observations1 January 2026A refined value of the Hubble constant H0=73.7±0.06( stat.)±1.1( syst.) km s−1 Mpc−1 was obtained using the DESI (Dark Energy Spectroscopic Instrument) spectrograph on the 4-meter telescope of the Kitt Peak observatory (USA) [8]. This value was found from the observations of peculiar galactic velocity with the use of the Tully-Fisher relation and the so-called fundamental galactic plane together with the redshift measurements. Measurements of distances to galaxies makes it possible to distinguish between the contribution of peculiar velocities and the cosmological Universe expansion. Although the normalization is performed using Ia supernovae, the measurement results are largely independent of other methods of determining H0. Another independent method is observation of strong gravitational lensing with time lag measurements. The TDCOSMO-2025 collaboration investigated eight lensed quasars using stellar velocity dispersion data in lens galaxies, allowing the density profile to be reconstructed [9]. The obtained value H0=71.6+3.9−3.3 km s−1 Mpc −1 is consistent with other H0 measurements at the error level. The gravitational lensing method may reach the accuracy of 1 % in future, which will help clarify a number of fundamental effects in cosmology, such as the “Hubble tension” (the discrepancy between H0 measurements for processes in the early and modern Universe. [8] Carr A et al., arXiv:2512.03232 [astro-ph.CO] [9] Birrer S et al. Astron. & Astrophys. 704 A63 (2025) |
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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