卷 193, 编号 11 (2023)

The current state of the problem of the origin and transport of ‘heavy’ ($A>4$) chemical elements in the Universe is discussed. The beginning of stellar nucleosynthesis (SNS) dates apparently to $z\gtrsim 20$ redshift epochs (age of the Universe $t_U\lesssim 180$ Myr). Presently, SNS traces are observed in some cases in galaxies at redshift $z\sim 10-15$ ($t_U\sim 500-270$ Myr). A massive redistribution of chemical elements from galaxies over the entire Universe became possible, primarily under the action of powerful explosions, in the reionization period at $z\lesssim 6$ {($t_U\gtrsim 940$ Myr). A correct interpretation of observational data requires an in-depth understanding of the transport and mixing dynamics of chemical elements in the Universe. Theoretical models predict their extremely nonuniform distribution in a range from the interstellar medium on spatial scales of a few hundred light years to the intergalactic medium spanning tens of millions of light years. This is observed in absorption spectra of quasars up to redshift $z\sim 6$ and results in observational selection. The review focuses on the early stages of the history of the Universe's chemical enrichment as it is currently understood given the observational selection effects. Observational data and theoretical ideas underlying the modern understanding of the complex process of the Universe's chemical evolution are outlined.

Precise control for individual quantum systems, such as individual photons, atoms, or ions, opens the door to a range of quantum technologies. The goal of this concept is to create devices that, due to quantum effects, will be able to solve prob„lems of data processing and secure information transfer and high-precision measurements of parameters of the surrounding world more effectively than existing approaches do. The key step in the advent of quantum technologies was the pioneering work of the second half of the twentieth century, which, first, showed the paradoxical nature and correctness of the quantum mechanical description of nature and, second, laid down and introduced the basic experimental approaches that became the basis of modern quantum technologies. The Nobel Prize in Physics 2022 was awarded to Alain Aspect, John Clauser, and Anton Zeilinger for their experiments with entangled photons, establishing the violation of Bell inequalities, and pioneering quantum information science.

We present a detailed analysis of the available data on the laser reduction of graphene oxide (GO). Issues of GO synthesis, structural models, and methods for controlling the properties of the material are considered. The chemical and thermal reduction mechanisms, the two main photoinduced mech„anisms for the transformation of dielectric GO films into conducting structures, are described, and their combined effect is illustrated. The impact of laser radiation parameters on the local functionalization of the material, which determines its properties, is critically analyzed. A summary table of the available data on the laser effect on GO is presented. Various applications are outlined, such as electronics, photovoltaics, energy, and flexible sensors, including medical applications. This study systematizes the results presented in the literature and contributes to the further study of the interaction of laser radiation with carbon materials, their transformation, control of properties, and the potential for application in all-carbon electronics.

We consider a theory which contains massless scalar fields with different sound speeds. For these theories we derive unitarity relations for partial wave amplitudes of $ 2 \to 2$ scattering, with explicit formulas for contributions of two-particle intermediate states. We also obtain unitarity bounds both in the most general case and in the case considered in the literature for the speed of sound, equal to unity. We illustrate our unitarity relations by explicit one-loop calculation to the first nontrivial order in couplings in a simple model of two scalar fields with different sound speeds. Obtained unitarity bounds can be used to estimating the strong coupling scale of a pertinent effective field theory (EFT).

Fundamental constants play an important role in nature. They determine many high-energy processes. It turns out that these constants also set bounds for the ‘ordinary’ properties of condensed matter, such as viscosity, thermal conductivity, elastic moduli, and the speed of sound. Kinematic viscosity has a global minimum point on the $(P, T)$ diagram, and the same is true for the thermal diffusivity of substances (except at the critical point). The minimum values of these quantities are determined only by the Planck constant $\hbar $ and the masses of the electron $m$ and the atom or molecule $ M$. A nontrivial conclusion is that the kinematic viscosity values for ordinary fluids and for quark–gluon plasma are close to each other. Similarly, the extrema of the elastic characteristics of substances, the mechanical properties of materials, and the speed of sound are also determined only by the Planck constant, the masses of the electron and ions, and the electron charge. The use of fundamental constants allows proposing reasonable estimates for the speed of sound of substances and the elastic characteristics of low-dimensional systems. We also note a possible connection between extreme values of macroscopic quantities and the anthropic principle.