Kinetic Scalar Curvature Extended f(R)f(R) Gravity

In this work we study a modified version of vacuum $f(R)$ gravity with a kinetic term which consists of the first derivatives of the Ricci scalar. We develop the general formalism of this kinetic Ricci modified $f(R)$ gravity and we emphasize on cosmological applications for a spatially flat cosmological background. By using the formalism of this theory, we investigate how it is possible to realize various cosmological scenarios. Also we demonstrate that this theoretical framework can be treated as a reconstruction method, in the context of which it is possible to realize various exotic cosmologies for ordinary Einstein-Hilbert action. Finally, we derive the scalar-tensor counterpart theory of this kinetic Ricci modified $f(R)$ gravity, and we show the mathematical equivalence of the two theories.Comment: NPB Accepte

Towards single-electron metrology

We review the status of the understanding of single-electron transport (SET) devices with respect to their applicability in metrology. Their envisioned role as the basis of a high-precision electrical standard is outlined and is discussed in the context of other standards. The operation principles of single electron transistors, turnstiles and pumps are explained and the fundamental limits of these devices are discussed in detail. We describe the various physical mechanisms that influence the device uncertainty and review the analytical and numerical methods needed to calculate the intrinsic uncertainty and to optimise the fabrication and operation parameters. Recent experimental results are evaluated and compared with theoretical predictions. Although there are discrepancies between theory and experiments, the intrinsic uncertainty is already small enough to start preparing for the first SET-based metrological applications.Comment: 39 pages, 14 figures. Review paper to be published in International Journal of Modern Physics

АНАЛІЗ ПІДХОДІВ ДО ФОРМУВАННЯ КОМАНДИ УПРАВЛІННЯ ПРОЕКТАМИ НА ПРИКЛАДІ ЕКІПАЖІВ МОРСЬКИХ СУДЕН

In the article, the authors examined the problematic aspects of project management; the study focuses on the optimization of the crew of the vessel — the project team based on the concept method. Within the framework of the approach proposed by the authors, a model has been developed for the formation of the crew of the vessel — the project team, which allows one to identify its composition, the most suitable and stable (balanced) for managing a specific project in terms of its competence, complementarity of crew members on the vessel (synergism) and its psychological characteristics. The use of the project management system implies the creation of a special group, the crew of a ships (project team), which becomes an independent participant of the project and manages the process of sending and forming the crew of the vessel within the project being implemented. This group is created for the period of project implementation and after its completion it is dissolved. Human resource planning — an estimate of the size and composition of human resources in the future. The project team is the main creative component of creating the end product or service in the projects. The project team is a group of employees who work directly on the project and are subordinate to the project manager. Unfortunately, there is no adequate model and method that would allow simultaneous optimization of the composition of personnel, teams, crew. The use of deterministic models and methods in solving our problem is ineffective, since there is an inability to predict the entire list of works when planning teams of projects, crews.Розглянуто проблемні аспекти управління проектами, досліджено питання оптимізації екіпажу судна — команди проекту на базисі концептуального методу. У рамках запропонованого підходу розроблено модель формування екіпажу судна — проектної команди, що дозволяє виявити її склад, найбільш придатний і стійкий (збалансований) для управління конкретним проектом щодо його компетентності, взаємодоповнюваності членів екіпажу на судні (синергізму) та його психологічних особливостей. Використання системи управління проектами передбачає створення спеціальної групи, екіпажу (команди проекту), яка стає самостійним учасником проекту і управляє процесом відправлення та формування екіпажу судна в рамках проекту, що реалізується. Ця група створюється на період реалізації проекту і після його завершення її розпускають. Планування людських (трудових) ресурсів (human resource planning) — оцінка розмірів і складу людських ресурсів у майбутньому. Проектна команда — основний креативний компонент створення кінцевого продукту або послуги у проектах. Команда проекту (project team) — група співробітників, які безпосередньо працюють над здійсненням проекту і підлеглі керівникові проекту. На жаль, адекватної моделі та методу, які б дозволили одночасно проводити комплексну оптимізацію складу персоналу, команд, екіпажу, на сьогодні не існує. Застосування детермінованих моделей і способів при вирішенні нашого завдання неефективне, оскільки неможливо передбачити весь перелік робіт при плануванні команд проектів, екіпажів суден

Introduction to Modified Gravity and Gravitational Alternative for Dark Energy

We review various modified gravities considered as gravitational alternative for dark energy. Specifically, we consider the versions of $f(R)$, $f(G)$ or $f(R,G)$ gravity, model with non-linear gravitational coupling or string-inspired model with Gauss-Bonnet-dilaton coupling in the late universe where they lead to cosmic speed-up. It is shown that some of such theories may pass the Solar System tests. On the same time, it is demonstrated that they have quite rich cosmological structure: they may naturally describe the effective (cosmological constant, quintessence or phantom) late-time era with a possible transition from decceleration to acceleration thanks to gravitational terms which increase with scalar curvature decrease. The possibility to explain the coincidence problem as the manifestation of the universe expansion in such models is mentioned. The late (phantom or quintessence) universe filled with dark fluid with inhomogeneous equation of state (where inhomogeneous terms are originated from the modified gravity) is also described.Comment: LaTeX file, 21 pages, references are added, lectures for 42 Karpacz Winter School on Theor Physic

Radiative Contributions to the Effective Action of Self-Interacting Scalar Field on a Manifold with Boundary

The effect of quantum corrections to a conformally invariant field theory for a self-interacting scalar field on a curved manifold with boundary is considered. The analysis is most easily performed in a space of constant curvature the boundary of which is characterised by constant extrinsic curvature. An extension of the spherical formulation in the presence of a boundary is attained through use of the method of images. Contrary to the consolidated vanishing effect in maximally symmetric space-times the contribution of the massless "tadpole" diagram no longer vanishes in dimensional regularisation. As a result, conformal invariance is broken due to boundary-related vacuum contributions. The evaluation of one-loop contributions to the two-point function suggests an extension, in the presence of matter couplings, of the simultaneous volume and boundary renormalisation in the effective action.Comment: 14 pages, 1 figure. Additional references and minor elucidating remarks added. To appear in Classical and Quantum Gravit

Influence of Technological Parameters on Magnetic Properties of Co-Rich Amorphous Ferromagnetic Microwires

The series of amorphous ferromagnetic glass-coated microwires of composition Co69Fe4Cr4Si12B11, manufactured by Taylor-Ulitovsky technique, was investigated. The series consisted of six types microwires fabricated under different technological conditions. The metallic nucleus and glass coating diameters of microwires ranged within 11-20 μm and 26-35 μm, respectively. Investigation of the magnetic propertiesof microwires was carried out using induction and the small-angle magnetization rotation techniques. The anisotropy field, the magnetostriction constant and the average value of the quenching stresses are estimated for all types of microwires. Based on the experimental data obtained, influence of technological parameters onthe microwire’s magnetic properties was investigated. Keywords: Amorphous ferromagnetic microwire, cobalt alloy, magnetic measurements, magnetostriction, internal stresse

Dark energy in modified Gauss-Bonnet gravity: late-time acceleration and the hierarchy problem

Dark energy cosmology is considered in a modified Gauss-Bonnet (GB) model of gravity where an arbitrary function of the GB invariant, $f(G)$, is added to the General Relativity action. We show that such theory is endowed with a quite rich cosmological structure: it may naturally lead to an effective cosmological constant, quintessence or phantom cosmic acceleration, with a possible transition from deceleration to acceleration. It is demonstrated in the paper that this theory is perfectly viable, since it is compliant with Solar System constraints. Specific properties of $f(G)$ gravity in a de Sitter universe, such as dS and SdS solutions, their entropy and its explicit one-loop quantization are studied. The issue of a possible solution of the hierarchy problem in modified gravities is addressed too.Comment: LaTeX file 20 pages, new subsections are adde

Dynamical Casimir Effect and Quantum Cosmology

We apply the background field method and the effective action formalism to describe the four-dimensional dynamical Casimir effect. Our picture corresponds to the consideration of quantum cosmology for an expanding FRW universe (the boundary conditions act as a moving mirror) filled by a quantum massless GUT which is conformally invariant. We consider cases in which the static Casimir energy is repulsive and attractive. Inserting the simplest possible inertial term, we find, in the adiabatic (and semiclassical) approximation, the dynamical evolution of the scale factor and the dynamical Casimir stress analytically and numerically (for SU(2) super Yang-Mills theory). Alternative kinetic energy terms are explored in the Appendix.Comment: 14 pages, REVTeX 4, 6 eps figure

String-inspired Gauss-Bonnet gravity reconstructed from the universe expansion history and yielding the transition from matter dominance to dark energy

We consider scalar-Gauss-Bonnet and modified Gauss-Bonnet gravities and reconstruct these theories from the universe expansion history. In particular, we are able to construct versions of those theories (with and without ordinary matter), in which the matter dominated era makes a transition to the cosmic acceleration epoch. It is remarkable that, in several of the cases under consideration, matter dominance and the deceleration-acceleration transition occur in the presence of matter only. The late-time acceleration epoch is described asymptotically by de Sitter space but may also correspond to an exact $\Lambda$CDM cosmology, having in both cases an effective equation of state parameter $w$ close to -1. The one-loop effective action of modified Gauss-Bonnet gravity on the de Sitter background is evaluated and it is used to derive stability criteria for the ensuing de Sitter universe.Comment: LaTeX20 pages, 4 figures, version to apear in PR