Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 31 - 60 of 175

Full-Text Articles in Physical Sciences and Mathematics

Kerr Spinning Particle, A. Burinskii Jan 2000

Kerr Spinning Particle, A. Burinskii

Turkish Journal of Physics

We give a brief review of the problems connected with the model of spinning particle based on the Kerr geometry. We consider peculiarities of the Kerr rotating black hole solution in gravity, supergravity and low energy string theory. A non-trivial supergeneralization of the Kerr-Newman solution to broken N=2 supergravity is considered. \par The problem of source of the Kerr geometry is discussed, and we consider some arguments in favor of the supersymmetric Fermi-ball model for the Kerr source based on the Witten $U(1)\times U(\tilde 1)$ field model for superconducting strings.


Global Results In Space Of Inter-Monomer Interactions For Hp Lattice Model, M. R. Ejtehadi̇, V. Shahrezaei̇, N. Hamedani̇ Jan 2000

Global Results In Space Of Inter-Monomer Interactions For Hp Lattice Model, M. R. Ejtehadi̇, V. Shahrezaei̇, N. Hamedani̇

Turkish Journal of Physics

Using the ground state candidates for Hydrophobic-Polar lattice model on a two dimensional square lattice, we exactly enumerate the native states of proteins with length up to 20 for a wide range of energy parameters. We find the reduced set of contact maps, ground state candidates, perfectly stable sequences and designability of configurations.


The Statistics Of Energy States Of A Hookean Model For Proteins, Ayşe Erzan, Erkan Tüzel Jan 2000

The Statistics Of Energy States Of A Hookean Model For Proteins, Ayşe Erzan, Erkan Tüzel

Turkish Journal of Physics

A generic model of a random polypeptide chain, with discrete torsional degrees of freedom and Hookean springs connecting pairs of hydrophobic residues, reproduces the energy probability distribution of real proteins over a very large range of energies. We show that this system with harmonic interactions, under dissipative dynamics driven by random noise, leads to a distribution of energy states obeying a modified one-dimensional Ornstein-Uhlenbeck process with reflecting boundary conditions, and giving rise to distributions of the Wigner or inverse Gaussian form. A continuum approximation leads to a path integral formulation of the problem. PACS 5.65+b,5.70Ln,87.17.Aa


Gauge Invariant Reduction And Integrability Of Sl(2 ,R)/ U(1) Wznw Theory, Chris Ford, George Jorjadze, Gerhard Weigt Jan 2000

Gauge Invariant Reduction And Integrability Of Sl(2 ,R)/ U(1) Wznw Theory, Chris Ford, George Jorjadze, Gerhard Weigt

Turkish Journal of Physics

The general solution of $SL(2,{\bf R})/U(1)$ WZNW theory is constructed by a gauge invariant reduction. This is done within both Lagrangian and Hamiltonian frameworks.


Canonical Quantisation Of The Sl(2,R)/ U(1) Gauged Wznw Black Hole Model, Christopher Ford, George Jorjadze, Gerhard Weigt Jan 2000

Canonical Quantisation Of The Sl(2,R)/ U(1) Gauged Wznw Black Hole Model, Christopher Ford, George Jorjadze, Gerhard Weigt

Turkish Journal of Physics

Gauged WZNW models are integrable conformal field theories with non-local canonical free-field transformations. Canonical quantisation requires quantum deformations.


Multi-Species Asymmetric Exclusion Process In Ordered Sequential Update, M. Ebrahi̇m Fouladvand, Farhad Jafarpour Jan 2000

Multi-Species Asymmetric Exclusion Process In Ordered Sequential Update, M. Ebrahi̇m Fouladvand, Farhad Jafarpour

Turkish Journal of Physics

A multi-species generalization of the asymmetric simple exclusion process (ASEP) is studied in ordered sequential and sub-lattice parallel updating schemes. In this model, particles hop with their own specific probabilities to their rightmost empty site and fast particles overtake slow ones with a definite probability. Using Matrix Product Ansatz (MPA), we obtain the relevant algebra, and study the uncorrelated stationary state of the model both for an open system and on a ring. A complete comparison between the physical results in these updates and those of random sequential introduced in [20,21] is made.


A Detour In De Sitter Space While Calculating Vacuum Fluctuatins, M. Hortaçsu Jan 2000

A Detour In De Sitter Space While Calculating Vacuum Fluctuatins, M. Hortaçsu

Turkish Journal of Physics

{We study vacuum fluctuations of different gravitational waves by taking a detour in de Sitter space in the intermediate steps. We find finite contributions when the coupling constant is dimensionless, whereas null result persists in the cases with dimensional coupling constants. We also test our method for exactly solvable cases, and show that no spurious perturbative effects are introduced through our method.


Product Integral Representations Of Wilson Lines And Wilson Loops And Non-Abelian Stokes Theorem, Robert L. Karp, Freydoon Mansouri, Jung S. Rno Jan 2000

Product Integral Representations Of Wilson Lines And Wilson Loops And Non-Abelian Stokes Theorem, Robert L. Karp, Freydoon Mansouri, Jung S. Rno

Turkish Journal of Physics

We make use of product integrals to provide an unambiguous mathematical representation of Wilson line and Wilson loop operators. Then, drawing upon various properties of product integrals, we discuss such properties of Wilson lines and Wilson loops as approximating them with partial sums, their convergence, and their behavior under gauge transformations. We also obtain a surface product integral representation for the Wilson loop operator. The result can be interpreted as the non-abelian version of Stokes theorem.


On Integrable Systems Related To Semisimple Lie Groups, G. A. Keri̇mov Jan 2000

On Integrable Systems Related To Semisimple Lie Groups, G. A. Keri̇mov

Turkish Journal of Physics

Quantum scattering systems related to the noncompact semisimple Lie groups G in the sense that the Hamiltonian of the system can be written as a function of the Casimir operator of G are considered. The S-matrix for such systems are defined in terms of an interwining operator of underling symmetry group G.


Nonabelian Cosmic Strings From So(3) Gauge Symmetry, Mehmet Koca Jan 2000

Nonabelian Cosmic Strings From So(3) Gauge Symmetry, Mehmet Koca

Turkish Journal of Physics

The nature of $SO(3)$ breaking into its closed subgroups and the emergence of nonabelian cosmic strings are discussed. Relevance to GUT breaking and thereby to cosmology is pointed out. Classification of cosmic strings are associated with the affine ADE Lie algebras.


Spinors And Positive Mass, Malcolm Ludvigsen Jan 2000

Spinors And Positive Mass, Malcolm Ludvigsen

Turkish Journal of Physics

As an example of how spinor methods can be applied to the positive-mass theorem, a simple, spinor-based proof of the theorem is presented for the case of a single black hole. Generalisations of the theorem are also discussed.


Cosmological Adiabatic Geometric Phase Of A Scalar Field In A Bianchi Spacetime, Ali̇ Mostafazadeh Jan 2000

Cosmological Adiabatic Geometric Phase Of A Scalar Field In A Bianchi Spacetime, Ali̇ Mostafazadeh

Turkish Journal of Physics

A two-component formulation of the Klein-Gordon equation is used to investigate the cyclic and noncyclic adiabatic geometric phases due to spatially homogeneous (Bianchi) cosmological models. It is shown that no adiabatic geometric phases arise for Bianchi type I models. For general Bianchi type IX models the problem of the adiabatic geometric phase is shown to be equivalent to the one for nuclear quadrupole interactions of a spin. For these models nontrivial non-Abelian adiabatic geometrical phases may occur in general.


From Antibracket To Equivariant Characteristic Classes, Armen Nersessian Jan 2000

From Antibracket To Equivariant Characteristic Classes, Armen Nersessian

Turkish Journal of Physics

We equip the exterior algebra of Riemann manifold by the odd symplectic structure. Then, by its use we construct the equivariant even (pre)symplectic structure, whose Poincare - Cartan invariants of the second structure define the equivariant Euler classes of the surfaces.


On The Duality Of Quantum Liouville Field Theory, L. O'Raifeartaigh, J. M. Pawlowski, V. V. Sreedhar Jan 2000

On The Duality Of Quantum Liouville Field Theory, L. O'Raifeartaigh, J. M. Pawlowski, V. V. Sreedhar

Turkish Journal of Physics

It has been found empirically that the Virasoro centre and 3-point functions of quantum Liouville field theory with potential $e^{2b\phi(x)}$ and external primary fields exp($\alpha\phi(x)$) are invariant with respect to the duality transformations $\hbar \alpha\rightarrow q-\alpha$ where $q=b^{-1}+b$. The steps leading to this result (via the Virasoro algebra and 3-point functions) are reviewed in the path-integral formalism. The duality stems from the fact that the quantum relationship between the $\alpha$ and the conformal weights $\Delta_\alpha$ is two-to-one. As a result the quantum Liouville potential may actually contain two exponentials (with related parameters). It is shown that in the two-exponential theory …


Gauge Transformations In General Relativity - A Report, L. C. Shepley, J. M. Pons, D. C. Salisbury Jan 2000

Gauge Transformations In General Relativity - A Report, L. C. Shepley, J. M. Pons, D. C. Salisbury

Turkish Journal of Physics

We take as our basic principle that the Lagrangian and the Hamiltonian formulations of general relativity should be equivalent. It is then possible to choose the gauge transformations so as to be projectable under the Legendre map from configuration-velocity space (the tangent bundle) to phase space (the cotangent bundle). This projectability requirement then implies that gauge transformations in general relativity (we study in particular spacetimes with a Yang-Mills field) must depend in a specific way on the lapse and shift of the metric. This talk outlines the arguments and presents some of the results of the application of these principles.


Chaos In Closed Isotropic Cosmological Models With Steep Scalar Field Potential, A. V. Toporensky Jan 2000

Chaos In Closed Isotropic Cosmological Models With Steep Scalar Field Potential, A. V. Toporensky

Turkish Journal of Physics

The dynamics of closed scalar field FRW cosmological models is studied for several types of exponentially and more than exponentially steep potentials. The parameters of scalar field potentials which allow a chaotic behaviour are found from numerical investigations. It is argued that analytical studies of equation of motion at the Euclidean boundary can provide an important information about the properties of chaotic dynamics. Several types of transition from chaotic to regular dynamics are described.


Coherent States For The Hydrogen Atom, Nuri̇ Ünal Jan 2000

Coherent States For The Hydrogen Atom, Nuri̇ Ünal

Turkish Journal of Physics

We obtained the coherent states for the hydrogen atom by transforming the problem onto the four oscillators in the parametric time at the classical level and quantizing these oscillators. We showed that for the coherent states the mean values of the physical position of the electron satisfy the Keplerian ellipsis and the dispersions of them oscillate in the parametric time.


Parameterized Absolute Parallelism: A Geometry For Physical Applications, Mamdouh Ishaac Wanas Jan 2000

Parameterized Absolute Parallelism: A Geometry For Physical Applications, Mamdouh Ishaac Wanas

Turkish Journal of Physics

Absolute parallelism (AP) geometry is frequently used for physical applications. Although it is wider than the Riemannian geometry, it has two main defects. The first is that its path equation does not represent physical trajectories of any test particle. The second is the identical vanishing of its curvature tensor. The present work shows that parameterizing this geometry would solve the two problems. Furthermore, the resulting parameterized (AP)-structure is more general than both the conventional (AP)-structure and the Riemannian structure. Also, it is shown that it can be reduced to one or the other, of these two geometric structures, in some …


Skyrmions From Harmonic Maps, Wojtek Zakrzewski Jan 2000

Skyrmions From Harmonic Maps, Wojtek Zakrzewski

Turkish Journal of Physics

We describe some relations between solitonic solutions of various models in different dimensions. We present some examples and then concentrate on some of our recent work (performed in collaboration with Ioannidou and Piette) \cite{IPZ} \cite{us2} which shows how some harmonic maps from $S^2$ to $CP^{N-1}$ can be used to find nontrivial spherically symmetric static solutions of the $SU(N)$ Skyrme model in 3 dimensions and to generate some of its low energy field configurations.


Time Evolution Of Fast Particles During Decay Of Hadronic Systems, Mohamed Tarek Hussein, Nabila Mohamed Hassan, Nagla El-Harby Jan 2000

Time Evolution Of Fast Particles During Decay Of Hadronic Systems, Mohamed Tarek Hussein, Nabila Mohamed Hassan, Nagla El-Harby

Turkish Journal of Physics

A phenomenological model is presented based on the formation of a nuclear thermodynamic system during the collision of intermediate and high energy heavy ions. The formulation and the dynamic picture are determined by solving the Vlasov equation. The solution is dressed in the form of a power series the first term of which being the equilibrium distribution in phase space. The rest, are time dependent perturbation terms due to the multiple strong interactions inside the system. The temperature gradient and the derivatives of the phase function are calculated. The time dependence of the angular emission of the produced particles is …


The Radius Cutoff For Relativistic Clusters, M. Hafizi Jan 2000

The Radius Cutoff For Relativistic Clusters, M. Hafizi

Turkish Journal of Physics

In this work we consider an isothermic relativistic kinetic gas under relativistic conditions, as a model for high center density galaxies. We apply the radius cutoff of the Emden type, in order to remove infinities. Numerically we find some theoretical configurations with very high values of masses concentrated in small volumes. Profiles of some thermodynamic quantities such as density, presure, will be independent from the choice of radius cutoff, whereas temperature and gravitational potential depend essentially on the cutoff value.


The Decay Of A Black Hole As A Quantum Dissipative Process, Carl Wolf Jan 2000

The Decay Of A Black Hole As A Quantum Dissipative Process, Carl Wolf

Turkish Journal of Physics

By considering the decay of a black hole as a result of the interaction of a quantum system with a dissipative vacuum, or in terms of string theory, the interaction of localized string modes with non-local string modes, we demonstrate how the single parameter representing dissipation can be calculated in terms of known fundamental constants. In view of the uncertainty embodied in all the present theories of black hole decay it is suggested that the approach of this note might provide fresh insight to the problem of black hole decay. P.A.C.S.: 98.80-Dr Cosmology


Associations Of X-Ray Binaries With Open Clusters And Supernova Remnants, Eni̇s Tuncer, H. Guseinov, Ü. Kiziloğlu, A. O. Allakhverdiev Jan 2000

Associations Of X-Ray Binaries With Open Clusters And Supernova Remnants, Eni̇s Tuncer, H. Guseinov, Ü. Kiziloğlu, A. O. Allakhverdiev

Turkish Journal of Physics

Searching for X-ray binaries projected on open clusters (OCs) and supernova remnants (SNRs), associations of X-ray binaries with OCs and SNRs in the Galaxy are discussed. Three of the high mass X-ray binaries (HMXBs) and four of the low mass X-ray binaries (LMXBs) are projected on open clusters. Five of HMXBs and six of LMXBs are projected on SNRs. The number of the HMXB projections are less than the LMXBs, which is not expected and is surprising since the objects in this study, except the LMXBs, are all young objects. Such associations help us improve distance and age estimates of …


Positron Annihilation And Xrd Studies On Deformed Al-Alloys With Low Concentration Of Mg, Emad A. Badawi, M. A. Abdel-Rahman, S. A. Mahmoud, A. A. Ramadan Jan 2000

Positron Annihilation And Xrd Studies On Deformed Al-Alloys With Low Concentration Of Mg, Emad A. Badawi, M. A. Abdel-Rahman, S. A. Mahmoud, A. A. Ramadan

Turkish Journal of Physics

Positron behaviour at grain boundaries is characterized by their bulk diffusibility D, their bulk free lifetime $\tau_f$ and their trapped lifetime $\tau_t$ ($\tau_t > \tau_f).$ Al-Mgx samples (x = 0-1.4 at \%) have been homogenized at 573 K for 12 hours. The mean lifetime, as (indirectly) measured at various concentrations, show a good fitting with Sigmodel giving $\tau_t$ = 180.664 ps and $\tau_{f}$ = 163.9 ps. The mean lifetime was found to vary exponentially with the degree of deformation. The XRD study showed that preferred orientation occurred at degrees of deformation $>$ 32 \%, whereas the peak intensity then increases …


A Glancing Incidence Exafs Study Of Evaporated Silver Films On Glass, Ahmet Bulut, Bünyami̇n Karabulut, Engi̇n Başaran, James Robinson Jan 2000

A Glancing Incidence Exafs Study Of Evaporated Silver Films On Glass, Ahmet Bulut, Bünyami̇n Karabulut, Engi̇n Başaran, James Robinson

Turkish Journal of Physics

A glancing incidence EXAFS experiment has been carried out with evaporated silver films on glass substrates. Prior to EXAFS data collection, a reflectivity curve was performed from which the critical angle for total external reflection of x-rays from surface were determined. The analysed EXAFS data revealed that there is a reduction in the coordination number and an increase in Debye-Waller factor compared to bulk values. These changes were explained in terms of grain size effect and the surface effects of the silver film.


Ferromagnetic Transitions In Ni-Mn Alloys, F. Boakye, R. K. Nkum Jan 2000

Ferromagnetic Transitions In Ni-Mn Alloys, F. Boakye, R. K. Nkum

Turkish Journal of Physics

Ferromagnetic transitions in nickel and nickel-manganese alloys have been studied using resistivity-temperature measurements from 800 to 77 K. The results establish the transition temperature of nickel as 610 K and the transition temperature is shifted to lower values as the concentration of Mn in the alloy is increased. Analysis of the resistivity results near the ordering temperature \( (T


The Effect Of Potassium Doping On Resistive Transitions And Transport Critical Current Of Bulk Ybco High-Tc Superconductors, S. Çelebi̇, A. Öztürk, İ. Karaca, U. Kölemen Jan 2000

The Effect Of Potassium Doping On Resistive Transitions And Transport Critical Current Of Bulk Ybco High-Tc Superconductors, S. Çelebi̇, A. Öztürk, İ. Karaca, U. Kölemen

Turkish Journal of Physics

We report on observations of the effect of potassium in YBCO (123) high temperature superconductors with nominal composition Y\( _{1-0,2x} \) Ba\( _{2-0.2x} \) K\( _{x} \) Cu\( _{3} \) O\( _{y} \). The electrical resistivity measurements show that the critical temperature T$_{c} \) (R=0) shifted slightly to lower temparature due to the K doping process. This process also decreases the transport critical current density and the activation energy for thermally activated flux flow. The magnetic field dependence of \( j_{c} \) was measured at 77 K after zero field cooling (ZFC) when the applied magnetic field is impressed (ZFCV) …


Internal Photoemission Spectroscopy For A Ptsi/P-Si Schottky Junction, Bülent Aslan, Raşi̇t Turan Jan 2000

Internal Photoemission Spectroscopy For A Ptsi/P-Si Schottky Junction, Bülent Aslan, Raşi̇t Turan

Turkish Journal of Physics

Properties of internal photoemission in a PtSi-Si Schottky junction have been studied. The traditional Fowler plot of a detector's photoyield is found to be nonlinear for values close to the barrier height of the junction. It is shown that the model that takes all scattering mechanisms into account provides a successful description for the experimental results. It is also shown that the photoemission spectrum is independent of temperature in agreement with this model. The properties of detector's ambient influence the photoemission spectrum for wavelength of 3 $\mu$m or less. A strong loss in the detector's response is observed at around …


^{87}Rb Nmr Relaxation And Vortex Dynamics In Rb_3c_{60}, Fügen Tabak, Maurizio Corti̇ Jan 2000

^{87}Rb Nmr Relaxation And Vortex Dynamics In Rb_3c_{60}, Fügen Tabak, Maurizio Corti̇

Turkish Journal of Physics

^{87}Rb NMR relaxation measurements in superconducting fullerene Rb_{3}C_{60} for various values of the external field are reported. In the normal state the results are in agreement with T_{1}T= Constant. Below T_{c}, while no evidence of Hebel-Slichter peak is present in temperature dependence of T_{1}^{-1} , maxima are observed in \( T_{2}^{-1} at T=22K characteristic of vortex field fluctuation. T_{1} shows an anomalous field dependence not yet explained.


Topological Unitarity Identities In The Theory Of Scalar Charged Particles Interacting Through A Pure C-S Gauge Field, Müge Boz, V. Ya Fainberg Jan 2000

Topological Unitarity Identities In The Theory Of Scalar Charged Particles Interacting Through A Pure C-S Gauge Field, Müge Boz, V. Ya Fainberg

Turkish Journal of Physics

Starting from the theory of relativistic scalar charged particles interacting via C-S field, it is verified that the gauge invariant sum of the imaginary parts of all Feynman diagrams with C-S photon lines on the mass shell vanish.