Green function techniques in the treatment of quantum transport at the molecular scale

The theoretical investigation of charge (and spin) transport at nanometer length scales requires the use of advanced and powerful techniques able to deal with the dynamical properties of the relevant physical systems, to explicitly include out-of-equilibrium situations typical for electrical/heat transport as well as to take into account interaction effects in a systematic way. Equilibrium Green function techniques and their extension to non-equilibrium situations via the Keldysh formalism build one of the pillars of current state-of-the-art approaches to quantum transport which have been implemented in both model Hamiltonian formulations and first-principle methodologies. We offer a tutorial overview of the applications of Green functions to deal with some fundamental aspects of charge transport at the nanoscale, mainly focusing on applications to model Hamiltonian formulations.Comment: Tutorial review, LaTeX, 129 pages, 41 figures, 300 references, submitted to Springer series "Lecture Notes in Physics

The Relation of Brexit with the UK's QE Decisions and its Impact on the Eurozone

This paper aims to provide some insights into the way that the recent referendum held on June 23rd about the Brexit could affect the UK's perspective to proceed to a new round of QE. Moreover, the effects of the latter on the Eurozone are under scrutiny. Transmission channels of the shock that the Brexit has brought about on the EU and the Eurozone, as well as possible scenarios about the future relationship between the UK and the EU are presented. To the best of our knowledge, this is the first academic piece of work that makes a direct link between the consequences of the Brexit on decisions about proceeding in further QE actions or not in the UK and at the same time studies how this could result in affecting the Eurozone's economy and its decision-making about adopting further unconventional policies. © Central Bank of Montenegro 2017

Spillovers between Russia's and Turkey's Geopolitical Risk during the 2000-2021 Putin Administration

This paper sets out to explore the nexus between Russia and Turkey regarding their geopolitical uncertainty measures (GPR) during the Putin Administration era in Russia. The innovative Caldara and Iacoviello indices and the Vector Autoregressive (VAR) methodology are adopted. This study sheds light on the series of geopolitical events that have taken place in Russia and Turkey in recent decades. Empirical outcomes reveal that Turkish geopolitical uncertainty is a weak influencer that increases Russian GPR in the short-term while decreasing it in the medium-term. The reverse effect does not hold. The nexus between geopolitical risk in Turkey and Russia is found to be unstable. Uncertainty in Turkey constitutes both a negative and a positive determinant of geopolitical stability in Russia, depending on the time horizon of the impact. Russia could take advantage of Turkish positive effects in the medium-run. This could be alarming for investors but could also prove beneficial as they should not invest in Russian assets when the country's geopolitical risk is elevated due to Turkey's geopolitical instability. Additionally, it is documented that energy financial markets in Russia are not influential on geopolitical uncertainty. © 2021 Walter de Gruyter GmbH, Berlin/Boston

Achieving sustainable financial transactions under regimes without a central bank—an intertemporal comparison

In this paper, by performing an intertemporal comparison, we investigate two monetary policy regimes where a central bank is absent, and we further refer on the mechanisms they developed so as to ensure the reliability of transactions between the parties involved. In particular, we mainly focus on the economic–monetary institutions of Athens during the Classical period (508–322 BCE) and we argue that (in principle) there are inter-temporal similarities between the Athenian and the current digital currencies regimes regarding the auditing principles with which the reliability of financial transactions is ensured. We found that in both cases, what is crucial for the success of the system is to achieve trust on the currency. By focusing on Classical Athens, we analyze the nature of the mechanisms and the auditing techniques used to ensure reliable commercial transactions. We also briefly analyze the modern cryptocurrency techniques. We found that the success of both financial regimes was based on achieving: low transactional costs, speed in commercial transactions, and what we characterize as security regarding the commercial transactions. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Brexit and new perspectives of an unconventional way of Eurozone revival

In the aftermath of the UK referendum on June 23rd, 2016 that resulted in a sonorous negative decision regarding the willingness of the British people to remain in the EU, a significant number of alarming questions have emerged. Although Europe should have forged in crises, nowadays, many compromises have to be made in order to maintain the European construction as intact as possible. The question we attempt to answer is whether a new phase of unconventional monetary policy in the form of QE would be appropriate to lessen the threat of an upcoming crisis. This is why we examine Eurozone QE perspectives through the prism of the new EU era without the UK in order to highlight the pros and cons of the historical Brexit decision. As new rounds of unconventional monetary policy are believed to be essential for supporting the weaker countries in the European south, perspectives of non-conventional success could alter and optimal policies be substantially reformulated subject to the newly-arising constraints. Based on the main scenarios about the UK's relations to the European Union in the near future, we estimate how a new round of non-conventional measures could affect the Britons as well as the European citizens. Moreover, we try to assess the viability of each of these outcomes through the spectrum of a monetary-driven decision-making. © 2019 Nikolaos A. Kyriazis et al., published by Sciendo

The Impacts of Geopolitical Uncertainty on Turkish Lira during the Erdoğan Administration

This paper sets out to explore whether the Turkish geopolitical uncertainty exhibits significant linkages with fluctuations in the Turkish lira (TRY) values against other currencies. The period examined covers the Erdoğan administration (March 2003 up to the present). The innovative geopolitical uncertainty index by Caldara and Iacoviello and modern GARCH methodologies are adopted in order to explore how geopolitical risk influences currency values and the overall economy during this turbulent period. Econometric outcomes reveal that geopolitical uncertainty leads to devaluation of TRY against the US dollar, the Swiss franc and the Swedish krona but in a non-significant manner whereas mixed results emerge concerning the impacts of macroeconomic or financial variables. © 2021 Informa UK Limited, trading as Taylor & Francis Group

Weak field galvanomagnetic measurements to distinguish cubic from non-cubic environments

Procedures utilizing an extension of the Van der Pauw technique are developed to distinguish by weak field galvanomagnetic measurements cubic and non-cubic symmetries. We consider (001), (110) and (111) oriented layers for which analytic expressions are given. Planar circular samples may be used. We have also found that in general when B = (Bu, Bv, Bw) a skewed behaviour is expected such that the principal directions of the surface of the resistivity magnitude and the crystallographic axes lie in different directions.Des procédures qui utilisent une extension de la technique Van der Pauw sont développées pour distinguer, par des mesures galvanomagnétiques de champ faible, des symétries cubiques et non cubiques. Nous considérons les couches orientées (001), (110) et (111) pour lesquelles les expressions analytiques sont données. Des échantillons plats, en forme de cercle peuvent être utilisés. Nous avons aussi trouvé que, en général, quand B = (Bu, Bv, Bw) un comportement de torsion est attendu, tel que, les directions principales de la surface de résistivité et les axes crystallographiques se trouvent dans des directions différentes

Weak-field magnetoresistance coefficients and the related magnetoresistance skewness effect

This work presents an overall view of the measurements concerning the galvanomagnetic coefficients in the weak-field case with an attempt to emphasize the physical significance of the results. The method is based on the anisotropy induced in the electrical behaviour by the magnetic field. Emphasis is also given in explaining the magnetoresistance skewness effect. A comparison with the classical method is also presented to indicate the advantage of the method. Finally the method is analyzed for measurements on n-type Ge for which the energy band model is derived to obtain the ml/m t ratio which in return is used to obtain the scattering factor, the carrier density and the drift mobility. The results are in accordance with previous findings.Ce travail présente une vue d'ensemble des mesures concernant les coefficients galvanomagnétiques dans le cas du champ faible afin de préciser la signification physique des résultats. La méthode est basée sur 1'anisotropie induite dans le comportement électrique à cause du champ magnétique. L'accent est mis aussi sur l'explication de l'effet de magnétorésistance oblique. Une comparaison avec la méthode classique est présentée pour indiquer les avantages de notre méthode. Celle-ci est appliquée à des mesures sur Ge de type n pour lequel le modèle des bandes d'énergie permet de déduire le quotient ml/mt ; ce quotient est utilisé pour obtenir le facteur de scattering, la densité et la mobilité des porteurs. Les résultats obtenus sont en accord avec les résultats antérieurs