Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

Browse

Filters

2009 - 200912010 - 20163

Settings

Publisher: search.filters.publisher.Springer VerlagScopus Q: search.filters.scopusQuartile.Q3

Search Results

Now showing 1 - 4 of 4
  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Electronic Structure and Correlations of Vitamin B12 Studied Within the Haldane-Anderson Impurity Model
    (Springer Verlag, 2016) Kandemir, Zafer; Mayda, Selma; Bulut, Nejat
    We study the electronic structure and correlations of vitamin B12 (cyanocobalamine) by using theframework of the multi-orbital single-impurity Haldane-Anderson model of atransition-metal impurity in a semiconductor host. The parameters of the effectiveHaldane-Anderson model are obtained within the Hartree-Fock (HF) approximation. Thequantum Monte Carlo (QMC) technique is then used to calculate the one-electron andmagnetic correlation functions of this effective model. We observe that new states forminside the semiconductor gap found by HF due to the intra-orbital Coulomb interaction atthe impurity 3d orbitals. In particular, the lowest unoccupiedstates correspond to an impurity bound state, which consists of states from mainly the CNaxial ligand and the corrin ring as well as the Co eg-like orbitals. We alsoobserve that the Co (3d) orbitals can develop antiferromagneticcorrelations with the surrounding atoms depending on the filling of the impurity boundstates. In addition, we make comparisons of the HF+QMC data with the density functionaltheory calculations. We also discuss the photoabsorption spectrum of cyanocobalamine.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Merger Dynamics in Three-Agent Games
    (Springer Verlag, 2011) Rador, Tonguç; Derici, R.
    We present the effect of mergers, a term which we use to mean a temporary alliance, in the dynamics of the three-agent model studied by Ben-Naim, Kahng and Kim and by Rador and Mungan. Mergers are possible in three-agent games because two agents can combine forces against the third player and thus increase their probability to win a competition. We implement mergers in this three-agent model via resolving merger and no-merger units of competition in terms of a two-agent unit. This way one needs only a single parameter which we have called the competitiveness parameter. We have presented an analytical solution in the fully competitive limit. In this limit the score distribution of agents is stratified and self-similar.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 6
    Hartree-Fock Approximation of Bipolaron State in Quantum Dots and Wires
    (Springer Verlag, 2010) Senger, Ramazan Tuğrul; Kozal, B.; Chatterjee, A.; Erçelebi, Atilla
    The bipolaronic ground state of two electrons in a spherical quantum dot or a quantum wire with parabolic boundaries is studied in the strong electron-phonon coupling regime. We introduce a variational wave function that can conveniently conform to represent alternative ground state configurations of the two electrons, namely, the bipolaronic bound state, the state of two individual polarons, and two nearby interacting polarons confined by the external potential. In the bipolaron state the electrons are found to be separated by a finite distance about a polaron size. We present the formation and stability criteria of bipolaronic phase in confined media. It is shown that the quantum dot confinement extends the domain of stability of the bipolaronic bound state of two electrons as compared to the bulk geometry, whereas the quantum wire geometry aggravates the formation of stable bipolarons. © 2010 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.
  • Article
    Citation - WoS: 21
    Citation - Scopus: 22
    Vacuum Energy as the Origin of the Gravitational Constant
    (Springer Verlag, 2009) Demir, Durmuş Ali
    We develop a geometro-dynamical approach to the cosmological constant problem (CCP) by invoking a geometry induced by the energy-momentum tensor of vacuum, matter and radiation. The construction, which utilizes the dual role of the metric tensor that it structures both the spacetime manifold and energy-momentum tensor of the vacuum, gives rise to a framework in which the vacuum energy induced by matter and radiation, instead of gravitating, facilitates the generation of the gravitational constant. The non-vacuum sources comprising matter and radiation gravitate normally. At the level of classical gravitation, the mechanism deadens the CCP yet quantum gravitational effects, if strong, can keep it existent.