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| Issue 5, 2024 |
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Extracts from the Internet | ||
Rydberg levels of a hydrogen atom in an electric field1 April 2024The proton charge radius rp, measured in the muon hydrogen atom on the basis of the Lamb shift effect, where the electron is replaced by a muon, is smaller than the one measured in ordinary hydrogen. This divergence is known as the “proton radius puzzle”. rp Is found in an indirect way from measurements of the Rydberg constant R∞, the electron wave function being partially found in the proton volume, and rp and R∞ must correlate. In this connection, experiments with highly excited Rydberg states sensitive to R∞ but almost indifferent to rp are of importanñe for resolving the rp problem. However, such measurements would require a very high frequency resolution. S Scheidegger and F Merkt (ETH Zurich) have overcome this difficulty by studying hydrogen in an electric field [1]. Transitions to Rydberg states (with the known correction due to the Stark effect) with quantum numbers n=20 and n=24 were measured. The ionization energy was found with record precision for a two-body system, and the Rydberg frequency cR∞ was obtained by a method insensitive to rp. The result indirectly confirms the rp value obtained in the experiment with muon hydrogen. New data will possibly help resolve the rp problem. It is preliminarily concluded that it is not related to the effects beyond the Standard Model, which may be responsible for the difference in the properties of ordinary and muon hydrogen. [1] Scheidegger S, Merkt F Phys. Rev. Lett. 132 113001 (2024) Miassite superconductivity1 April 2024The rear mineral miassite Rh17S15 was first found in a deposit in the upper reaches of the Miass river (Southern Urals, Russia). It is one of the few compounds in nature, which can be superconducting. As a matter of fact, superconductivity was revealed in pure miassite synthesized in laboratory, because the natural compounds include many impurities and do not form large crystals. Miassite superconductivity has several remarkable features, namely, an anomalously heigh upper critical field of Hc2, a large jump of thermal conductivity, etc. R Prozorov (University of Iowa, USA) and his colleagues proved the existence of a nontraditional type of Rh17S15 superconductivity, which is not described by the Bardeen-Cooper-Schrieffer theory [2]. A synthesized miassite single crystal showed a linear temperature dependence of the London penetration depth Δλ(T) (in ordinary superconductors Δλ(T)=const at low T). Tc and Hc2 were found to be suppressed by nonmagnetic defects induced by an electron beam. The results of measurements agree with the presence of nodes in the energy gap, which are a distinctive feature of the nontraditional superconductivity. An unconventional type of superconductivity was shown by a number of substances, for instance, high-temperature superconductors – cuprates, but these materials are products of synthetic chemistry and, as distinct from miassites, do not exist in nature. [2] Kim H et al. Communications Materials 5 17 (2024) A fundamental limit for radiation absorption in a medium1 April 2024The radiative and absorbing properties of media are important for many practical applications in information transmission, energetics, etc. A fundamental constraint on the absorbing layer thickness and the wavelength range width for absorption in the medium of radiation reflected from the metal surface was obtained earlier in the theoretical work of the Russian physicist K N Rozanov (Institute of Theoretical and Applied Electrodynamics of RAS) [3]. K N Rozanov’s approach was used further to investigate some other configurations. Also largely based on K N Rozanov’s calculations, a group of researchers from the Duke University (USA) obtained a new limit relating the width of the absorption band to the thickness of homogeneous layers of the absorbing medium without a reflective surface [4]. To this end, the analytical properties of reflection and transmission coefficients were considered using the Kramers – Kronig relations. The obtained result was confirmed in particular cases by the transmission matrix method and numerical simulations of wave passage through dielectric metamaterials. [3] Rozanov K N IEEE Trans. Antennas Propag. 48 1230 (2000) [4] Padilla W J et al. Nanophotonics, online publication of March 8, 2024 Dark matter density spikes around supermassive black holes1 April 2024According to theoretical models, supermassive black holes (SMBH) in galactic centers must be surrounded by dark-matter density spikes. Researchers M N Chan and C M Lee (Educational University of Hong Kong, China) were possibly the first to discover such a spike for a binary SMBH in the system OJ 287 [5]. The measured rate of decrease in the orbital period of this system is higher than it should be due to gravitational wave radiation only. If an additional decrease is assumed to be explained by the dynamic SMBH friction in the dark matter, then it follows that the spike profile has the exponent γsp=2.351+0.032−0.045 well agreeable with the theoretical value γsp=2.333. More exact information about the density spikes will be possible to obtain from observation of stars in the vicinity of SMBH and from further measurements of low-frequency gravitational waves emitted by pairs of SMBH. [5] Chan M H, Lee C M, arXiv:2402.03751 [astro-ph.GA] Constraints on the epoch of reionization using the kinematic Sunyaev – Zel’dovich effect1 April 2024The kinematic Sunyaev – Zel’dovich (kSZ) effect is related to the scattering of cosmic microwave background radiation (CMB) photons by moving electron clouds. After the Universe reionization was over, the kSZ effect was revealed from mutual CMB correlation and galaxy distribution maps. In the reionization epoch, the kSZ signal must be modulated by the velocity field and create nongaussian corrections at CMB maps. S Raghunathan (Center for Astrophysics, National Center for Supercomputing Applications, Urbana, Illinois, USA) and their co-authors presented the results of the analysis of the kSZ trispectrum using the CMB temperature maps obtained by the South Pole Telescope and Herschel-SPIRE [6]. The main contribution to the trispectrum is made by CMB lensing signals and astrophysical foreground. No kSZ heightening above the level of this background has been revealed, which, together with the data obtained using the Gun-Peterson effect, allowed setting the upper limit on the reionization duration Δz<4.5. The result obtained agrees with the data of M Planck space telescope. For the Syunyaev – Zel’dovich effect and other Ya B Zel’dovich’s works, see [7]. [6] Raghunathan S et al., arXiv:2403.02337 [astro-ph.CO] [7] Vikhlinin A A, Kravtsov A V, Markevich M L, Sunyaev R A, Churazov E M Phys. Usp. 57 317 (2014); UFN 184 339 (2014) |
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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