Non-exponential decay in quantum field theory and in quantum mechanics: the case of two (or more) decay channels

We study the deviations from the exponential decay law, both in quantum field theory (QFT) and quantum mechanics (QM), for an unstable particle which can decay in (at least) two decay channels. After a review of general properties of non-exponential decay in QFT and QM, we evaluate in both cases the decay probability that the unstable particle decays in a given channel in the time interval between $t$ and $t+dt.$ An important quantity is the ratio of the probability of decay into the first and the second channel: this ratio is constant in the Breit-Wigner limit (in which the decay law is exponential) and equals the quantity $\Gamma_{1}/\Gamma_{2}$, where $\Gamma_{1}$ and $\Gamma_{2}$ are the respective tree-level decay widths. However, in the full treatment (both for QFT and QM) it is an oscillating function around the mean value $\Gamma_{1}/\Gamma_{2}$ and the deviations from this mean value can be sizable. Technically, we study the decay properties in QFT in the context of a superrenormalizable Lagrangian with scalar particles and in QM in the context of Lee Hamiltonians, which deliver formally analogous expressions to the QFT case.Comment: 32 pages, 10 figures. To appear in "Foundations of Physics

Projecting the urbanization effect on soil organic carbon stocks in polar and steppe areas of European Russia by remote sensing

This paper describes the effect of urbanization on soil organic carbon (SOC) stocks by projecting the main urban land cover classes over the initial pre-urban soil maps. Two cities different in climate and soil conditions as well as in availability of SOC data were chosen as the case studies. Rostov-on-Don is the center of Russian South, where croplands and natural steppes have been conventionally thoroughly studied by soil scientists. In contrast, soils of Murmansk located in Russian Arctics have always been overlooked due to low suitability for agriculture. Global, national and regional soil maps and databases were used to estimate pre-urban SOC stocks in the areas. The outcomes based on Harmonized World Soil Database were highly uncertain, underestimating 0-100 cm SOC stocks in the polar region and overestimating them in the steppe region, whereas the results based on Digital Soil Map of Russia and regional maps were comparable. Land cover structures of Rostov-on-Don and Murmansk were mapped based on the stepwise per-pixel and sub-pixel classification algorithms applied to Sentinel-2 and included the following classes: sealed soils, green lawns, trees and shrubs, bare soils and water. Murmansk was dominated by trees and shrubs (58.1%) with the proportion of area 17.5% covered by sealed soils. In Rostov-on-Don, less than 30% of the total area was covered by trees and shrubs which is also comparable with bare soils (19.6%)_and lawns (23.4%), whereas almost one third of the territory was sealed (27.6%). These land cover structures had a different impact on the topsoil SOC stocks: a 30-50% increase in Murmansk compared to the 18% decrease in Rostov-on-Don. An increase of the 0-100 cm SOC stocks was shown for both regions, however in the polar conditions it was two times higher compared to the steppe. In polar conditions, conversion of natural soils into urban non-sealed soils increased SOC stocks from 30% to more than 4 times in 0-10 cm layer and from 47% to almost 3 times in the 0-100 cm layer. The highest increase was reported for the lawns, whereas SOC under trees and shrublands were considerably lower. In Rostov-on-Don, sealed and bare soils stored less SOC compared to the initial natural soils. The conversion of natural areas into urban green infrastructure increased SOC up to 50-70%. Although the absolute SOC values based on the global and national legacy data are highly uncertain, especially for the polar areas, the research outcomes clearly reveal possible patterns in SOC changes induced by different urbanization pathways in contrast climatic conditions and highlight the complexity of the urbanization effect on soils © 2021 Elsevier B.V

Synthesis of hybrid compounds by benzylation of acylhydrazones with 3,5-di-tert-butyl-4-hydroxybenzyl acetate

N-Benzylation of acylhydrazones of the hydroxybenzaldehyde series with 3,5-di-tert-butyl-4-hydroxybenzyl acetate was performed at room temperature in the absence of acid or base catalysts. Carboxamides do not react with 3,5-di-tert-butyl-4-hydroxybenzyl acetate under similar conditions. N-Benzylation of isoniazid and (diphenylphosphoryl)acetic acid hydrazones was shown to be an efficient method for the synthesis of new hybrid compounds containing moieties of biologically active acylhydrazones and sterically hindered phenols. N-Benzyl derivatives of isoniazid and (diphenylphosphoryl)acetic acid hydrazones containing a hydroxy group at the ortho position of the aromatic ring are formed as individual E isomers with respect to the C-N double bond

Systematic trends of neutron skin thickness versus relative neutron excess

7 pags., 4 figs., 1 tab.Available experimental neutron skin thicknesses of even-even stable Ca, Ni, Sn, Pb, and Cd isotopes are evaluated, and separate trends of neutron skin thickness versus relative neutron excess δ=(N-Z)/A are observed for different isotopic chains. This phenomenon is quantitatively reproduced by the deformed Skyrme Hartree-Fock + Bardeen-Cooper-Schrieffer model with SLy4 force.This work is supported in part by the NSFC (12022504, 11775273, U1932140,12121005), by the CAS Pioneer Hundred Talents Program, by the CAS Open Research Project of large research infrastructures, by the CAS Maintenance and Reform of Large Research Infrastructures (DSS-WXGZ2018-0002), and by the Max Plank Society. Y.A.L. acknowledges the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 682841 “ASTRUm”) and P.S. acknowledges MCI/AEI/FEDER, UE (Spain) (Grant no. PGC2018-093636-B-I00

Determining neutron-induced reaction cross sections through surrogate reactions at storage rings

International audienceDetermining the cross sections of neutron-induced reactions on short-lived nuclei is imperative to rate calculations in stellar nucleosynthesis and applications of nuclear physics. It is also an immense experimental challenge due to the radioactivity of the targets involved. Our goal is to circumvent this obstacle by using surrogate reactions in inverse kinematics at the heavy-ion storage rings of GSI/FAIR. We present here preliminary results from the first proof of principle experiment, where a beam of $^{208}$Pb impinged on a H$_{2}$ gas jet target in the Experimental Storage Ring (ESR)