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## Novel energy scale in the interacting two-dimensional electron system evidenced from transport and thermodynamic measurements

We study how the non-Fermi-liquid two-phase state reveals itself in transport properties of high-mobility Si-MOSFETs. We have found features in zero-field transport, magnetotransport, and thermodynamic spin magnetization in a 2D correlated electron system that may be directly related with the two-phase state. The features manifest above a density dependent temperature T* that represents a novel high-energy scale, apart from the Fermi energy. More specifically, in magnetoconductivity, we found a sharp onset of the {\cb novel} regime \delta \sigma(B,T) ~ (B/T)^2 above a density-dependent temperature T_{kink}(n),

a high-energy behavior that ``mimics'' the low-temperature diffusive interaction regime. The zero-field resistivity temperature dependence exhibits an inflection point T_{infl}(n). In thermodynamic magnetization, the weak-field spin susceptibility per electron, d \chi /d n changes sign at T_{dM/dn}(n). All three notable temperatures, T_{kink}, T_{infl}, and T_{dM/dn}, behave critically ~ (n-n_c), are close to each other, and are intrinsic to high-mobility samples solely; we therefore associate them

with an energy scale T* caused by interactions in the 2DE system.

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Experimental and theoretical studies of the coherent spin dynamics of two-dimensional GaAs/AlGaAs electron gas were performed. The system in the quantum Hall ferromagnet state exhibits a spin relaxation mechanism that is determined by many-particle Coulomb interactions. In addition to the spin exciton with changes in the spin quantum numbers of δS=δSz=−1, the quantum Hall ferromagnet supports a Goldstone spin exciton that changes the spin quantum numbers to δS=0 and δSz=−1, which corresponds to a coherent spin rotation of the entire electron system to a certain angle. The Goldstone spin exciton decays through a specific relaxation mechanism that is unlike any other collective spin state.

Strongly interacting two-dimensional (2D) carrier system has a tendency to spontaneous spin magnetization and mass divergence. Numerous experiments aimed to reveal these instabilities were not entirely convincing. In particular, spin susceptibility of itinerant electrons, determined from quantum oscillations, remains finite at the critical density of the 2D metal-insulator transition (MIT), n = n (c) . In contrast, the susceptibility and effective mass determined from high field magnetotransport were reported to diverge. Later, it became clear that as interactions grow, the homogeneous 2D Fermi liquid breaks into a two phase state which hampers interpretation of the experimental data. The thermodynamic magnetization measurements have revealed spontaneous formation of the spin-polarized collective electron droplets ("nanomagnets") in the correlated 2D Fermi liquid, while the spin susceptibility of itinerant electrons in the surrounding 2D "Fermi sea" remains finite. Here, we report how the non Fermi-liquid two-phase state (dilute ferromagnet) reveals itself in magnetotransport and zero field transport. We found in the correlated 2D system a novel energy scale T (au)< T (F) . At TaeT (au) the in-plane field magnetotransport and zero field transport exhibit features. Finally, in thermodynamic magnetization, the spin susceptibility per electron, a, chi/a, n changes sign at TaeT (au). All three notable temperatures are close to each other, behave critically, ; we associate, therefore, T (au) with a novel energy scale caused by interactions in the two-phase 2DE system.

Physics of many-body systems where particles are restricted to move in two spatial dimensions is challenging and even controversial: On one hand, neither long-range order nor Bose condensation may appear in innite uniform 2D systems at nite temperature, on the other hand this does not prohibit super uidity or superconductivity. Moreover, 2D superconductors, such as cuprates, are among the systems with highest critical temperatures. Ultracold atoms are a platform for studying 2D physics. Uniquely to other physical systems, quantum statistics may be completely changed in an ultracold gas: an atomic Fermi gas may be smoothly crossed over into a gas of Bose molecules (or dimers) by tuning interatomic interactions. We review recent experiments where such crossover has been demonstrated as well as critical phenomena in the Fermi-to-Bose crossover. We also present simple theoretical models describing the gas at different points of the crossover and compare the data to these and more advanced models.

The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.

Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.

This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .

The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.