Continuous time crystal in an electron-nuclear spin system: stability and melting of periodic auto-oscillations

Crystals spontaneously break the continuous translation symmetry in space, despite the invariance of the underlying energy function. This has triggered suggestions of time crystals analogously lifting translational invariance in time. Originally suggested for closed thermodynamic systems in equilibrium, no-go theorems prevent the existence of time crystals. Proposals for open systems out of equilibrium led to the observation of discrete time crystals subject to external periodic driving to which they respond with a sub-harmonic response. A continuous time crystal is an autonomous system that develops periodic auto-oscillations when exposed to a continuous, time-independent driving, as recently demonstrated for the density in an atomic Bose-Einstein condensate with a crystal lifetime of a few ms. Here we demonstrate an ultra-robust continuous time crystal in the nonlinear electron-nuclear spin system of a tailored semiconductor with a coherence time exceeding hours. Varying the experimental parameters reveals huge stability ranges of this time crystal, but allows one also to enter chaotic regimes, where aperiodic behavior appears corresponding to melting of the crystal. This novel phase of matter opens the possibility to study systems with nonlinear interactions in an unprecedented way.Comment: 12 figures, 17 page

A new class of sum rules for products of Bessel functions

In this paper we derive a new class of sum rules for products of the Bessel functions of first kind. Using standard algebraic manipulations we extend some of the well known properties of $J_n$. Some physical applications of the results are also discussed. A comparison with the Newberger[J. Math. Phys. \textbf{23} (1982) 1278] sum rules is performed on a typical example.Comment: Published in Journal of Mathematical Physics, 9 pages, no picture

The Effect of Complex Alloying of a Biocompatible Titanium Alloy Based on the Ti-Nb System on the Structure and Properties Formed during Annealing

The effect of complex alloying of Zr, Sn, Ta alloy of Ti-Nb system based on β-solid solution in cold-rolled state on the evolution of structure and properties (microhardness and contact modulus of elasticity) during recrystallization annealing is investigated.Исследование выполнено за счет гранта Российского научного фонда (проект № 18-13-00220)

THE EFFECT OF TEMPERATURE-TIME PARAMETERS OF ANNEALING ON THE STRUCTURE AND YOUNG’S MODULUS OF A COLD-ROLLING BIOCOMPATIBLE TITANIUM ALLOY

The evolution of the structure, physical and mechanical properties after annealing of a cold-rolled biocompatible Ti-41 wt alloy% Nb with a total degree of deformation of 75% at various temperatures (700, 850 ° C) and holding time (2-32 min) was investigated.Работа выполнена при поддержке контракта № 02.A03.21.0006, финансируемого в рамках постановления № 211 Правительства Российской Федерации

Auxetity Analysis of a Beta-Solid Solution with a BCC Lattice in BIocompatible Titanium Alloys

The auxetity of a β-solid solution with a BCC lattice was analyzed for various compositions of Ti-(Nb, Mo, Ta) and Ti-(Nb, Mo, Ta)-(Zr, Sn) binary Ti-based systems , which are widely used in medicine for the production of implants.Исследование выполнено за счет гранта Российского научного фонда (проект № 18-13-00220)

Principles of Building Pedagogical Interaction in the Conditions of Distance Learning

В марте 2020 года российская система образования внезапно оказалась в ситуации, когда нужно было не разрабатывать онлайн-курсы в дополнение к очному обучению, а реконструировать очную среду обучения и процессы полностью в онлайн-пространстве. Рассмотрены принципы построения педагогического взаимодействия в условиях дистанционной формы обучения. Обобщены принципы педагогического взаимодействия в традиционном, аудиторном формате. Описаны особенности построения педагогического взаимодействия с применением современных информационно-коммуникативных технологий и цифровых средств осуществления образовательного процесса. Проанализированы особенности и принципы коммуникации в онлайн-среде в условиях вынужденного перехода на дистанционное обучение в марте 2020 года.This article is devoted to the identification of the principles of building pedagogical interaction in the conditions of distance learning

Radiation requirements and testing of cryogenic thermometers for the ILC

Large quantity of cryogenic temperature sensors will be used for operation of the International Linear Collider (ILC). Most of them will be subject to high radiation doses during the accelerator lifetime. Understanding of particle energy spectra, accumulated radiation dose in thermometers and its impact on performance are vital in establishing technical specification of cryogenic thermometry for the ILC. Realistic MARS15 computer simulations were performed to understand the ILC radiation environment. Simulation results were used to establish radiation dose requirements for commercially available cryogenic thermometers. Two types of thermometers, Cernox{reg_sign} and TVO, were calibrated prior to irradiation using different technique. The sensors were subjected then to up to 200 kGy electron beam irradiation with kinetic energy of 5 MeV, a representative of the situation at the ILC operation. A post-irradiation behavior of the sensors was studied. The paper describes the MARS15 model, simulation results, cryogenic test set-up, irradiation tests, and cryogenic test results