Universality in Glassy Low-Temperature Physics

We propose a microscopic translationally invariant glass model which exhibits two level tunneling systems with a broad range of asymmetries and barrier heights in its glassy phase. Their distribution is qualitatively different from what is commonly assumed in phenomenological models, in that symmetric tunneling systems are systematically suppressed. Still, the model exhibits the usual glassy low-temperature anomalies. Universality is due to the collective origin of the glassy potential energy landscape. We obtain a simple explanation also for the mysterious {\em quantitative} universality expressed in the unusually narrow universal glassy range of values for the internal friction plateau.Comment: 4 pages, 5 figures, uses RevTeX

Local Properties of the Potential Energy Landscape of a Model Glass: Understanding the Low Temperature Anomalies

Though the existence of two-level systems (TLS) is widely accepted to explain low temperature anomalies in the sound absorption, heat capacity, thermal conductivity and other quantities, an exact description of their microscopic nature is still lacking. We performed computer simulations for a binary Lennard-Jones system, using a newly developed algorithm to locate double-well potentials (DWP) and thus two-level systems on a systematic basis. We show that the intrinsic limitations of computer simulations like finite time and finite size problems do not hamper this analysis. We discuss how the DWP are embedded in the total potential energy landscape. It turns out that most DWP are connected to the dynamics of the smaller particles and that these DWP are rather localized. However, DWP related to the larger particles are more collective

Vibrational instability, two-level systems and Boson peak in glasses

We show that the same physical mechanism is fundamental for two seemingly different phenomena such as the formation of two-level systems in glasses and the Boson peak in the reduced density of low-frequency vibrational states g(w)/w^2. This mechanism is the vibrational instability of weakly interacting harmonic modes. Below some frequency w_c << w_0 (where w_0 is of the order of Debye frequency) the instability, controlled by the anharmonicity, creates a new stable universal spectrum of harmonic vibrations with a Boson peak feature as well as double-well potentials with a wide distribution of barrier heights. Both are determined by the strength of the interaction I ~ w_c between the oscillators. Our theory predicts in a natural way a small value for the important dimensionless parameter C ~ 10^{-4} for two-level systems in glasses. We show that C ~ I^{-3} and decreases with increasing of the interaction strength I. We show that the number of active two-level systems is very small, less than one per ten million of oscillators, in a good agreement with experiment. Within the unified approach developed in the present paper the density of the tunneling states and the density of vibrational states at the Boson peak frequency are interrelated.Comment: 28 pages, 3 figure

Christian Context of Historical Novel (Zakhar Prilepin’s “Abode”)

The specificity of the synthesis of elements included in the historical narrative, and Christian motives, images in the novel of the largest contemporary Russian prose writer Zakhar Prilepin is comprehended in the article. The relevance of the article is due to the need to build a coherent and consistent history of the development of Russian literature over the past two decades, an important part of which is the legacy of the popular writers. The scientific novelty of the work lies in the fact that for the first time in Russian literary criticism “Abode” is considered from the proposed perspective: its genre specificity is analyzed in a Christian context. It has been established that, despite the presence of elements of documentary, adventurous, love-psychological novels, in terms of genre, “The Abode” can be attributed to a historical novel (it depicts a turning point in Russian history through a conflict between historical figures and fictional “average” heroes, combines historical facts and fiction). At the same time, an interest in eternal moral issues, problems of life and death, conscience and duty, love and fidelity in their Christian understanding becomes a feature of Prilepin’s understanding of the historical theme. In their work, the authors of the article used comparative historical, biographical, socio-cultural methods, as well as the method of a holistic analysis of a work of art

Noise in a Quantum Point Contact due to a Fluctuating Impurity Configuration

We propose a theoretical model for the low-frequency noise observed in a quantum point contact (QPC) electrostatically defined in the 2D electron gas at a GaAs-AlGaAs interface. In such contacts electron scattering by soft impurity- or boundary potentials coherently splits an incoming wave function between different transverse modes. Interference between these modes have been suggested to explain observed non-linearities in the QPC-conductance. In this study we invoke the same mechanism and the time-dependent current due to soft dynamical impurity scattering in order to analyze the low-frequency (telegraph-like) noise which has been observed along with a nonlinear conductance. For the simplified case of a channel with two extended (current carrying) modes, a simple analytical formula for the noise intensity is derived. Generally we have found qualitative similarities between the noise and the square of the transconductance. Nevertheless, incidentally there may be situations when noise is suppressed but transconductance enhanced.Comment: 9 revte

Quantum Statistical Physics of Glasses at Low Temperatures

We present a quantum statistical analysis of a microscopic mean-field model of structural glasses at low temperatures. The model can be thought of as arising from a random Born von Karman expansion of the full interaction potential. The problem is reduced to a single-site theory formulated in terms of an imaginary-time path integral using replicas to deal with the disorder. We study the physical properties of the system in thermodynamic equilibrium and develop both perturbative and non-perturbative methods to solve the model. The perturbation theory is formulated as a loop expansion in terms of two-particle irreducible diagrams, and is carried to three-loop order in the effective action. The non-perturbative description is investigated in two ways, (i) using a static approximation, and (ii) via Quantum Monte Carlo simulations. Results for the Matsubara correlations at two-loop order perturbation theory are in good agreement with those of the Quantum Monte Carlo simulations. Characteristic low-temperature anomalies of the specific heat are reproduced, both in the non-perturbative static approximation, and from a three-loop perturbative evaluation of the free energy. In the latter case the result so far relies on using Matsubara correlations at two-loop order in the three-loop expressions for the free energy, as self-consistent Matsubara correlations at three-loop order are still unavailable. We propose to justify this by the good agreement of two-loop Matsubara correlations with those obtained non-perturbatively via Quantum Monte Carlo simulations.Comment: 13 pages, 6 figure

Predictive value of cardiovascular risk factors in the formation of cardiovascular and all-cause mortality: results of a 27-year cohort prospective study

Aim. To study the prognostic significance of cardiovascular risk factors (RFs) in the formation of all-cause and cardiovascular mortality based on the results of a 27-year prospective cohort study of Tomsk population of both sexes aged 20-59 years.Material and methods. The object of study was random house-to-house sample of Tomsk population. In total, 1546 people (630 men and 916 women) aged 20-59 were examined. In 1988-1991, the prevalence of following cardiovascular RFs was studied: hypertension (HTN), overweight, smoking, alcohol consumption, hypercholesterolemia (HCE), low high-density lipoprotein cholesterol levels (hypo-HDL-emia), hypertriglyceridemia (HTG). All examination methods used were strictly standardized. To determine the RF, the criteria generally accepted in epidemiological studies were used. Over 27 years of follow-up, 330 deaths were recorded, including 142 due to cardiovascular disease.Results. In the multivariate Cox proportional hazard model, the following va­riables were studied: HTN, overweight, smoking, alcohol consumption, HCE, hypo-HDL-emia, HTG, coronary artery disease (CAD) (according to epi­demio­logical criteria), and age. The strongest predictor of of all-cause death was frequent alcohol use (relative risk (RR) 2,75). Smoking increased the risk of death by 2,72 times. Among former smokers, the risk of all-cause death was 1,9 times higher compared to non-smokers. HTN increases the death risk by 1,61 times. Each year of life lived increases the death risk by 1,06 times. The most significant risk factor for death from CVD was frequent alcohol consumption (RR 3,01). Smoking increases the cardiovascular death risk by 2,28 times. Among former smokers, the RR of cardiovascular death was 1,91. HTN increases the risk of cardiovascular mortality by 1,84 times compared with people with normal blood pressure. Each year of life lived increases the risk of cardiovascular death by 1,1 times. In multivariate analysis, overweight, HCE, hypo-HDL-emia, HTG did not have a significant independent effect on the all-cause and cardiovascular death risk.Conclusion. In a 27-year cohort prospective study, independent predictors of all-cause and cardiovascular mortality, along with hypertension and age, were lifestyle risk factors, such as smoking and frequent alcohol consumption

Future of superheavy element research: Which nuclei could be synthesized within the next few years?

Low values of the fusion cross sections and very short half-lives of nuclei with Z$>$120 put obstacles in synthesis of new elements. Different nuclear reactions (fusion of stable and radioactive nuclei, multi-nucleon transfers and neutron capture), which could be used for the production of new isotopes of superheavy (SH) elements, are discussed in the paper. The gap of unknown SH nuclei, located between the isotopes which were produced earlier in the cold and hot fusion reactions, can be filled in fusion reactions of $^{48}$Ca with available lighter isotopes of Pu, Am, and Cm. Cross sections for the production of these nuclei are predicted to be rather large, and the corresponding experiments can be easily performed at existing facilities. For the first time, a narrow pathway is found to the middle of the island of stability owing to possible $\beta^+$-decay of SH isotopes which can be formed in ordinary fusion reactions of stable nuclei. Multi-nucleon transfer processes at near barrier collisions of heavy (and very heavy, U-like) ions are shown to be quite realistic reaction mechanism allowing us to produce new neutron enriched heavy nuclei located in the unexplored upper part of the nuclear map. Neutron capture reactions can be also used for the production of the long-living neutron rich SH nuclei. Strong neutron fluxes might be provided by pulsed nuclear reactors and by nuclear explosions in laboratory conditions and by supernova explosions in nature. All these possibilities are discussed in the paper.Comment: An Invited Plenary Talk given by Valeriy I. Zagrebaev at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS