Electronic and Magnetic Properties of the 8-ZGNR/h-BN(0001) Interface

The results of a density functional theory investigations of structural and electronic properties of zig-zag graphene nanoribbons 8-ZGNR/ h-BN(0001) are presented. The peculiarities of the spin state at the Fermi level and the role of the edge effect and the effect of substrate in formation of the band gap (380 meV) in 8-ZGNR/h-BN(0001) system were determined. The contributions of nanoribbon edges and the substrate in formation of the gap have been differentiated. The estimations of local magnetic moments on carbon atoms of the 8-ZGNR nanoribbon are made. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3524

Pulse Laser Deposition method for UV-Photocathode production

Production method of alkali halides UVphotocathodes durable to environment exposure was proposed. Photocathodes with highhomogeneous and adhesion photoemission layerwere made. Quantum yield measurements results ofmanufactured photocathodes are presented.Developed method is promising for creation of highaperture electron injectors and detectors

LANDSLIDES IN VITSI (FLORINA) TERRITORY

Στην εργασία αυτή εξετάζονται τα αίτια που οδήγησαν τρία πρανή σε κατολίσθηση στον δρόμο που οδηγεί από το χωριό Δροσοπηγή στην κορυφή του όρους Βίτσι στην περιοχή της Φλώρινας. Στα πλαίσια της σχετικής διερεύνησης που πραγματοποιήθηκε μελετήθηκε η σεισμικότητα, η μορφολογία, η γεωλογία, η λιθολογία και η υδρογεωλογία της περιοχής, συλλέχθηκαν στοιχεία σχετικά με το ύψος του υετού στην περιοχή ενώ παράλληλα πραγματοποιήθηκε ένα πρόγραμμα γεωτεχνικών εργασιών μέσω 3 δειγματοληπτικών γεωτρήσεων, επιτόπου μετρήσεων και εργαστηριακών δοκιμών σε επιλεγμένα εδαφικά δοκίμια προκειμένου να προσδιοριστούν τα εδαφικά χαρακτηριστικά των σχηματισμών που κατολίσθησαν. Παράλληλα, συλλέχθηκαν στοιχεία πρόσφατης σεισμικότητα της περιοχής καθότι οι κατολισθήσεις απέχουν 18- 25km από τα επίκεντρα δύο ιστορικών σεισμών μεγέθους Mw= 6.0 και 6.5. Η αποτίμηση και η επεξεργασία όλων των συλλεχθέντων πληροφοριών, μας οδήγησαν με σχετική ασφάλεια στην γενεσιουργό αιτία των υφιστάμενων κατολισθήσεων και αποτέλεσαν την βάση για την μελέτη ευστάθειας των πρανών προκειμένου να προταθούν μέτρα αντιστήριξης τους.Landslides can provoke lifeline’s performance malfunction, injuries or fatalities and may diminish accessibility to critical facilities and surrounding properties. The scope of this research is to describe and to identify the triggering factors for three landslides along the road from Drosopigi village to the top of Vitsi Mountain at Florina territory using all the available data. Several information were collected for this area, such as the annual rate of the rainfall/ snowfall, the rainfall intensity/day, the seismicity, the geomorphology, the geology, the lithology and the hydrologic conditions. Moreover, in-situ investigations of the landslides, geotechnical and laboratory tests were carried out in three geotechnical boreholes to indentify the soil formations nearby the landslides. Taking into account that the landslides are located 18km, 22km and 25km,away from the epicenters of two historical earthquakes with magnitudes Mw= 6.0 και 6.5 and also that last winter heavy rainfalls/snowfalls were observed in the area with very low temperatures (-15OC), slope’s failure may have been triggered by an earthquake, by snowfalls/rainfalls or by human activities

Beyond-Constant-Mass-Approximation Magnetic Catalysis in the Gauge Higgs-Yukawa Model

Beyond-constant-mass approximation solutions for magnetically catalyzed fermion and scalar masses are found in a gauge Higgs-Yukawa theory in the presence of a constant magnetic field. The obtained fermion masses are several orders of magnitude larger than those found in the absence of Yukawa interactions. The masses obtained within the beyond-constant-mass approximation exactly reduce to the results within the constant-mass approach when the condition $\nu \ln (\frac{1}{\hat{m}^{2}})\ll 1$ is satisfied. Possible applications to early universe physics and condensed matter are discussed.Comment: Revised numerical results. New figures. Several sections rewritte

Non-abelian plane waves and stochastic regimes for (2+1)-dimensional gauge field models with Chern-Simons term

An exact time-dependent solution of field equations for the 3-d gauge field model with a Chern-Simons (CS) topological mass is found. Limiting cases of constant solution and solution with vanishing topological mass are considered. After Lorentz boost, the found solution describes a massive nonlinear non-abelian plane wave. For the more complicate case of gauge fields with CS mass interacting with a Higgs field, the stochastic character of motion is demonstrated.Comment: LaTeX 2.09, 13 pages, 11 eps figure

Magnetic Oscillations in Dense Cold Quark Matter with Four-Fermion Interactions

The phase structures of Nambu-Jona-Lasinio models with one or two flavours have been investigated at non-zero values of $\mu$ and $H$, where $H$ is an external magnetic field and $\mu$ is the chemical potential. In the phase portraits of both models there arise infinitely many massless chirally symmetric phases, as well as massive ones with spontaneously broken chiral invariance, reflecting the existence of infinitely many Landau levels. Phase transitions of first and second orders and a lot of tricritical points have been shown to exist in phase diagrams. In the massless case, such a phase structure leads unavoidably to the standard van Alphen-de Haas magnetic oscillations of some thermodynamical quantities, including magnetization, pressure and particle density. In the massive case we have found an oscillating behaviour not only for thermodynamical quantities, but also for a dynamical quantity as the quark mass. Besides, in this case we have non-standard, i.e. non-periodic, magnetic oscillations, since the frequency of oscillations is an $H$-dependent quantity.Comment: latex, 29 pages, 8 figure

QED Effective Action at Finite Temperature: Two-Loop Dominance

We calculate the two-loop effective action of QED for arbitrary constant electromagnetic fields at finite temperature T in the limit of T much smaller than the electron mass. It is shown that in this regime the two-loop contribution always exceeds the influence of the one-loop part due to the thermal excitation of the internal photon. As an application, we study light propagation and photon splitting in the presence of a magnetic background field at low temperature. We furthermore discover a thermally induced contribution to pair production in electric fields.Comment: 34 pages, 4 figures, LaTe

Abnormal number of Nambu-Goldstone bosons in the color-asymmetric 2SC phase of an NJL-type model

We consider an extended Nambu--Jona-Lasinio model including both (q \bar q)- and (qq)-interactions with two light-quark flavors in the presence of a single (quark density) chemical potential. In the color superconducting phase of the quark matter the color SU(3) symmetry is spontaneously broken down to SU(2). If the usual counting of Goldstone bosons would apply, five Nambu-Goldstone (NG) bosons corresponding to the five broken color generators should appear in the mass spectrum. Unlike that expectation, we find only three gapless diquark excitations of quark matter. One of them is an SU(2)-singlet, the remaining two form an SU(2)-(anti)doublet and have a quadratic dispersion law in the small momentum limit. These results are in agreement with the Nielsen-Chadha theorem, according to which NG-bosons in Lorentz-noninvariant systems, having a quadratic dispersion law, must be counted differently. The origin of the abnormal number of NG-bosons is shown to be related to a nonvanishing expectation value of the color charge operator Q_8 reflecting the lack of color neutrality of the ground state. Finally, by requiring color neutrality, two massive diquarks are argued to become massless, resulting in a normal number of five NG-bosons with usual linear dispersion laws.Comment: 13 pages, 4 figures, revtex

Consistency analysis of a nonbirefringent Lorentz-violating planar model

In this work analyze the physical consistency of a nonbirefringent Lorentz-violating planar model via the analysis of the pole structure of its Feynman propagators. The nonbirefringent planar model, obtained from the dimensional reduction of the CPT-even gauge sector of the standard model extension, is composed of a gauge and a scalar fields, being affected by Lorentz-violating (LIV) coefficients encoded in the symmetric tensor $\kappa_{\mu\nu}$. The propagator of the gauge field is explicitly evaluated and expressed in terms of linear independent symmetric tensors, presenting only one physical mode. The same holds for the scalar propagator. A consistency analysis is performed based on the poles of the propagators. The isotropic parity-even sector is stable, causal and unitary mode for $0\leq\kappa_{00}<1$. On the other hand, the anisotropic sector is stable and unitary but in general noncausal. Finally, it is shown that this planar model interacting with a $\lambda|\varphi|^{4}-$Higgs field supports compactlike vortex configurations.Comment: 11 pages, revtex style, final revised versio

The Influence of an External Chromomagnetic Field on Color Superconductivity

We study the competition of quark-antiquark and diquark condensates under the influence of an external chromomagnetic field modelling the gluon condensate and in dependence on the chemical potential and temperature. As our results indicate, an external chromomagnetic field might produce remarkable qualitative changes in the picture of the color superconducting (CSC) phase formation. This concerns, in particular, the possibility of a transition to the CSC phase and diquark condensation at finite temperature.Comment: 27 pages, RevTex, 8 figures; the version accepted for the publication in PRD (few references added; new numerical results added; main conclusions are not changed