Формування північно-східних кордонів Румунії: міжнародно-правове забезпечення інкорпорації бессарабських земель до складу Королівства (кінець 1919 – перша половина 1920 рр.

The foreign policy of Romania throughout the first decades of the 20th century was not either unplanned or spontaneous. It was pursued by the Kingdom’s leadership within the framework of the idea of establishing the “Greater Romania”. Generally, the policy of official Bucharest during the war period and the period of the formation of the Versailles system of international relations was concentrated on defending national interests and gaining the status of a regional leader in the Balkans. The purpose of the article is to analyze the political struggle around the “Bessarabia” issue at the Paris Peace Conference throughout December 1919 – March 1920. Indeed, exactly this timeframe became decisive for the Romanian Kingdom in terms of the recognition by the international community of its sole priority to rule Bessarabia. Great amount of relevant information and materials enabled authors of the article to analyze a comparatively short-term period of proceedings of the Paris Conference as it clearly demonstrates the tense atmosphere of the process of creating a new geopolitical map of post-war Europe. As a whole, Alexandru Vaida-Voevod’s activities in solving the “Bessarabia” problem had positive outcomes for Romania. On March 12-th, the National Assembly directed the decision on this issue to the government in Bucharest. Taking into account preliminary conclusions and “yearning” of Bessarabia population the Allies in general declared for the reunification of Bessarabia and Romania. At the same time, they demanded that official Bucharest guarantee legitimate interests of Bessarabia on the same conditions as for other parts of the Kingdom.Зовнішня політика Румунії впродовж перших десятиліть ХХ ст. не була випадковою чи спонтанною. Вона реалізовувалася керівництвом Королівства в межах ідеї створення «Великої Румунії». Загалом політика Бухаресту в роки війни та в період формування Версальської системи міжнародних відносин стала показовою з точки зору відстоювання національних інтересів та завоювання статусу регіонального лідера на Балканах. Метою статті є аналіз політичної боротьби навколо «бессарабського» питання на Паризькій мирній конференції впродовж грудня 1919 – березня 1920 рр. Фактично саме цей проміжок часу став вирішальним для королівської Румунії у питанні визнання міжнародною спільнотою її виключного права на володіння Бессарабією. Зважаючи на значний обсяг матеріалу авторами був взятий відносно нетривалий період роботи конференції в Парижі, оскільки він яскраво демонструє у якій напруженій атмосфері формувалася нова геополітична карта повоєнної Європи. В цілому діяльність А. Вайди-Воєводи у вирішенні «бессарабської» проблеми мала позитивні результати для Румунії. 12 березня Верховна Рада направила бухарестському уряду своє рішення з цього питання. Враховуючи попередні висновки та «прагнення» населення краю, союзники в цілому висловлювалися на користь возз’єднання Бессарабії з Румунією. Водночас, вони наполягали, що Бухарест має забезпечити законні інтереси краю на тих же умовах, як і в інших частинах Королівства

A study on correlation effects in two dimensional topological insulators

We investigate correlation effects in two dimensional topological insulators (TI). In the first part, we discuss finite size effects for interacting systems of different sizes in a ribbon geometry. For large systems, there are two pairs of well separated massless modes on both edges. For these systems, we analyze the finite size effects using a standard bosonization approach. For small systems, where the edge states are massive Dirac fermions, we use the inhomogeneous dynamical mean field theory (DMFT) combined with iterative perturbation theory as an impurity solver to study interaction effects. We show that the finite size gap in the edge states is renormalized for weak interactions, which is consistent with a Fermi-liquid picture for small size TIs. In the second part, we investigate phase transitions in finite size TIs at zero temperature focusing on the effects of possible inter-edge Umklapp scattering for the edge states within the inhomogeneous DMFT using the numerical renormalization group. We show that correlation effects are effectively stronger near the edge sites because the coordination number is smaller than in the bulk. Therefore, the localization of the edge states around the edge sites, which is a fundamental property in TIs, is weakened for strong coupling strengths. However, we find no signs for "edge Mott insulating states" and the system stays in the topological insulating state, which is adiabatically connected to the non-interacting state, for all interaction strengths smaller than the critical value. Increasing the interaction further, a nearly homogeneous Mott insulating state is stabilized.Comment: 20 page

Superconductivity of Quasi-One and Quasi-Two Dimensional Tight-Binding Electrons in Magnetic Field

The upper critical field $H_{c2}(T)$ of the tight-binding electrons in the three-dimensional lattice is investigated. The electrons make Cooper pairs between the eigenstates with the same energy in the strong magnetic field. The transition lines in the quasi-one dimensional case are shown to deviate from the previously obtained results where the hopping matrix elements along the magnetic field are neglected. In the absence of the Pauli pair breaking the transition temperature $T_c(H)$ of the quasi-two dimensional electrons is obtained to oscillationally increase as the magnetic field becomes large and reaches to $T_c(0)$ in the strong field as in the quasi-one dimensional case.Comment: 4pages,4figures,to be published in J.Phys.Soc.Jp

Spin-density-wave instabilities in the organic conductor (TMTSF)_2ClO_4: Role of anion ordering

We study the spin-density-wave instabilities in the quasi-one-dimensional conductor (TMTSF)_2ClO_4. The orientational order of the anions ClO_4 doubles the unit cell and leads to the presence of two electrnic bands at the Fermi level. From the Ginzburg-Landau expansion of the free energy, we determine the low-temperature phase diagram as a function of the strength of the Coulomb potential due to the anions. Upon increasing the anion potential, we first find a SDW phase corresponding to an interband pairing. This SDW phase is rapidly supressed, the metallic phase being then stable down to zero temperature. The SDW instability is restored when the anion potential becomes of the order of the hopping amplitude. The metal-SDW transition corresponds to an intraband pairing which leaves half of the Fermi surface metallic. At lower temperature, a second transition, corresponding to the other intraband pairing, takes place and opens a gap on the whole Fermi surface. We discuss the consequences of our results for the experimental phase diagram of (TMTSF)_2ClO_4 at high magnetic field.Comment: 13 pages, 10 figures, Version 2 with minor correction

Organization of rural tourism as a factor of rural development

This article is an attempt to study the agricultural tourism and developing recommendations on their organization in the regions of Russia. In the Belgorod region, the development of rural tourism is of fundamental importance for small businesses, which can be traced in regional development program

System of strategic management of the development of the organization

The article discusses the process of organizing and developing the modern system of management strategy and de-velopment of the organization in terms of mobility and instability in the market secto

Fractional ac Josephson effect in unconventional superconductors

For certain orientations of Josephson junctions between two p_x-wave or two d-wave superconductors, the subgap Andreev bound states produce a 4pi-periodic relation between the Josephson current I and the phase difference phi: I ~ sin(phi/2). Consequently, the ac Josephson current has the fractional frequency eV/h, where V is the dc voltage. In the tunneling limit, the Josephson current is proportional to the first power (not square) of the electron tunneling amplitude. Thus, the Josephson current between unconventional superconductors is carried by single electrons, rather than by Cooper pairs. The fractional ac Josephson effect can be observed experimentally by measuring frequency spectrum of microwave radiation from the junction.Comment: 8 pages, 3 figures, RevTEX 4; v2. - minor typos corrected in proof

Neutron scattering and superconducting order parameter in YBa2Cu3O7

We discuss the origin of the neutron scattering peak at 41 meV observed in YBa$_2$Cu$_3$O$_7$ below $T_c$. The peak may occur due to spin-flip electron excitations across the superconducting gap which are enhanced by the antiferromagnetic interaction between Cu spins. In this picture, the experiment is most naturally explained if the superconducting order parameter has $s$-wave symmetry and opposite signs in the bonding and antibonding electron bands formed within a Cu$_2$O$_4$ bilayer.Comment: In this version, only few minor corrections and the update of references were done in order to make perfect correspondence with the published version. RevTeX, psfig, 5 pages, and 3 figure

Edge states and determination of pairing symmetry in superconducting Sr2RuO4

We calculate the energy dispersion of the surface Andreev states and their contribution to tunneling conductance for the order parameters with horizontal and vertical lines of nodes proposed for superconducting Sr2RuO4. For vertical lines, we find double peaks in tunneling spectra reflecting the van Hove singularities in the density of surface states originating from the turning points in their energy dispersion. For horizontal lines, we find a single cusp-like peak at zero bias, which agrees very well with the experimental data on tunneling in Sr2RuO4.Comment: 6 pages, 6 figures. V.2: comparison with experiment added and discussion of horizontal nodes expanded. v.3: significant expansion: 1 figure and 2 pages added. v.4: acknowledgements added. Additional viewgraphs with experimental and theoretical curves superimposed are available at http://www2.physics.umd.edu/~yakovenk/talks/Sr2RuO4

From Luttinger to Fermi liquids in organic conductors

This chapter reviews the effects of interactions in quasi-one dimensional systems, such as the Bechgaard and Fabre salts, and in particular the Luttinger liquid physics. It discusses in details how transport measurements both d.c. and a.c. allow to probe such a physics. It also examine the dimensional crossover and deconfinement transition occurring between the one dimensional case and the higher dimensional one resulting from the hopping of electrons between chains in the quasi-one dimensional structure.Comment: To be published In the book "The Physics of Organic Conductors and Superconductors", Springer, 2007, ed. A. Lebe