The role of interaction vertices in bound state calculations

In recent studies of the one and two-body Greens' function for scalar interactions it was shown that crossed ladder and ``crossed rainbow'' (for the one-body case) exchanges play a crucial role in nonperturbative dynamics. In this letter we use exact analytical and numerical results to show that the contribution of vertex dressings to the two-body bound state mass for scalar QED are cancelled by the self-energy and wavefunction normalization. This proves, for the first time, that the mass of a two-body bound state given by the full theory can in a very good approximation be obtained by summing only ladder and crossed ladder diagrams using a bare vertex and a constant dressed mass. We also discuss the implications of the remarkable cancellation between rainbow and crossed rainbow diagrams that is a feature of one-body calculations.Comment: 9 pages, 5 figure

Quark-Antiquark Bound States in the Relativistic Spectator Formalism

The quark-antiquark bound states are discussed using the relativistic spectator (Gross) equations. A relativistic covariant framework for analyzing confined bound states is developed. The relativistic linear potential developed in an earlier work is proven to give vanishing meson$\to$ $q+\bar{q}$ decay amplitudes, as required by confinement. The regularization of the singularities in the linear potential that are associated with nonzero energy transfers (i.e. $q^2=0,q^{\mu}\neq0$) is improved. Quark mass functions that build chiral symmetry into the theory and explain the connection between the current quark and constituent quark masses are introduced. The formalism is applied to the description of pions and kaons with reasonable results.Comment: 31 pages, 16 figure

Kent meydanı kullanım nedenlerinin Antalya Cumhuriyet Meydanı örneğinde irdelenmesi

Kent meydanları, birçok kişi tarafından bilinen ve kolaylıkla bulunabilen, kentin veya bulundukları alanın merkezi noktasında konumlanan, estetik ve işlevsel açıdan birçok özelliğe sahip mekânlardır. Aynı zamanda kent meydanları kullanıcılara gereksinimleri doğrultusunda çeşitli katkılar sağlayan alanlardır. Cumhuriyet Meydanı Antalya kentinin kent merkezinde konumlanan ve günün hemen hemen her saatinde yerli ve yabancı kullanıcılar tarafından yoğun bir şekilde kullanılan bir meydandır. Meydanın yakın çevresinde çeşitli kamu kurum ve kuruluşları, alışveriş ve iş merkezleri, özel eğitim kurumları, restoran vb. gibi kullanımlar yer almaktadır. Bu araştırmada kullanıcıların kent meydanlarını kullanma nedenleri Antalya Cumhuriyet Meydanı örneğinde anket çalışması ile irdelenmiştir. Çalışma sonucunda Cumhuriyet Meydanı gibi toplanma ve odak noktası olma özelliğine sahip bir alanın, yaşam tarzlarına bağlı olarak günümüzde en çok “zorunlu geçiş yapmak’ için kullanıldığı sonucuna ulaşılmıştır. Anahtar kelimeler: Kent meydanı, Kentsel tasarım, Antalya Cumhuriyet Meydan

Normalization of the covariant three-body bound state vertex function

The normalization condition for the relativistic three nucleon Bethe-Salpeter and Gross bound state vertex functions is derived, for the first time, directly from the three body wave equations. It is also shown that the relativistic normalization condition for the two body Gross bound state vertex function is identical to the requirement that the bound state charge be conserved, proving that charge is automatically conserved by this equation.Comment: 24 pages, 9 figures, published version, minor typos correcte

Feynman-Schwinger representation approach to nonperturbative physics

The Feynman-Schwinger representation provides a convenient framework for the cal culation of nonperturbative propagators. In this paper we first investigate an analytically solvable case, namely the scalar QED in 0+1 dimension. With this toy model we illustrate how the formalism works. The analytic result for the self energy is compared with the perturbative result. Next, using a $\chi^2\phi$ interaction, we discuss the regularization of various divergences encountered in this formalism. The ultraviolet divergence, which is common in standard perturbative field theory applications, is removed by using a Pauli-Villars regularization. We show that the divergence associated with large values of Feynman-Schwinger parameter $s$ is spurious and it can be avoided by using an imaginary Feynman parameter $is$.Comment: 26 pages, 9 figures, minor correctio

Confinement and the analytic structure of the one body propagator in Scalar QED

We investigate the behavior of the one body propagator in SQED. The self energy is calculated using three different methods: i) the simple bubble summation, ii) the Dyson-Schwinger equation, and iii) the Feynman-Schwinger represantation. The Feynman-Schwinger representation allows an {\em exact} analytical result. It is shown that, while the exact result produces a real mass pole for all couplings, the bubble sum and the Dyson-Schwinger approach in rainbow approximation leads to complex mass poles beyond a certain critical coupling. The model exhibits confinement, yet the exact solution still has one body propagators with {\it real} mass poles.Comment: 5 pages 2 figures, accepted for publication in Phys. Rev.

Pole Term and Gauge Invariance in Deep Inelastic Scattering

In this paper we reconcile two contradictory statements about deep inelastic scattering (DIS) in manifestly covariant theories: (i) the scattering must be gauge invariant, even in the deep inelastic limit, and (ii) the pole term (which is not gauge invariant in a covariant theory) dominates the scattering amplitude in the deep inelastic limit. An ``intermediate'' answer is found to be true. We show that, at all energies, the gauge dependent part of the pole term cancels the gauge dependent part of the rescattering term, so that both the pole and rescattering terms can be separately redefined in a gauge invariant fashion. The resulting, redefined pole term is then shown to dominate the scattering in the deep inelastic limit. Details are worked out for a simple example in 1+1 dimensions.Comment: 10 figure

Vector Meson Photoproduction with an Effective Lagrangian in the Quark Model

A quark model approach to the photoproduction of vector mesons off nucleons is proposed. Its starting point is an effective Lagrangian of the interaction between the vector meson and the quarks inside the baryon, which generates the non-diffractive s- and u- channel resonance contributions. Additional t-channel $\pi^0$ and $\sigma$ exchanges are included for the $\omega$ and $\rho^0$ production respectively to account for the large diffractive behavior in the small $t$ region as suggested by Friman and Soyeur. The numerical results are presented for the $\omega$ and $\rho$ productions in four isospin channels with the same set of parameters, and they are in good agreement with the available data not only in $\omega$ and $\rho^0$ productions but also in the charged $\rho$ productions where the additional t-channel $\sigma$ exchange does not contribute so that it provides an important test to this approach. The investigation is also extended to the $\phi$ photoproduction, and the initial results show that the non-diffractive behavior of the $\phi$ productions in the large $t$ region can be described by the s- and u- channel contributions with significantly smaller coupling constants, which is consistent with the findings in the similar studies in the QHD framework. The numerical investigation has also shown that polarization observables are essential for identifying so-called "missing resonances".Comment: 36 pages, 10 PS figures, extended version of nucl-th/9711061 and nucl-th/9803021, submitted to PR

A Study On Young Disabled People’s Use Of Common Areas in The University Campuses Example Of Olbia Culture Center in Akdeniz University

Biyolojik, psikolojik ve sosyal değişim ve gelişim sürecini içeren “gençlik döneminde” bulunan bireylerin özellikle üniversite döneminde, kampüs alanlarının büyük bir önemi vardır. Bu dönemi yaşayan engelli gençler dikkate alındığında kampüs alanların önemi daha da artmaktadır. Araştırma Akdeniz Üniversitesi Olbia Kültür Merkezi’ni n engelli bireylerin kullanımı açısından uygunluğu, kullanımında yaşayabileceği sorunları ve alandan beklentilerini ortaya koymayı amaçlamıştır. Araştırmanın sonucunda engelli bireylerin üniversite döneminde sosyal gereksinimlerini karşılamada kampüs alanının önemi belirlenmiş ancak bunun yanında engelli bireylerin söz konusu alanları rahat kullanamamakla beraber bu alanları diğer bireylerle yeterince paylaşamadıkları saptanmıştır.Campus areas are of great importance for people studying at the university during their adolescence when biological, psychological and social changes take place. When disabled people at this period are taken into consideration, these areas become more significant. This research aims to demonstrate the suitability of Olbia Culture Center of Akdeniz University for the disabled people’s use while drawing attention to both the problems that can be encountered in the use of the area and the expectations from it. As a result of this research, it has been determined that campus areas are essential to meet people’s social needs ; however, disabled people can neither take full advantage of the mentioned areas nor share that space with other individuals

Performance Estimation of Organic Rankine Cycle by Using Soft Computing Technics

In this study, the thermal efficiency values of Organic Rankine cycle system were estimated depending on the condenser temperature and the evaporator temperatures values by adaptive network fuzzy interference system (ANFIS) and artificial neural networks system (ANN). Organic Rankine cycle (ORC) fluids of R365-mfc and SES32 were chosen to evaluate as the system fluid. The performance values of ANN and ANFIS models are compared with actual values. The R2 values are determined between 0.97 and 0.99 for SES36 and R365-mfc, and this is satisfactory. Although it was observed that both ANN and ANFIS models obtained a good statistical prediction performance through coefficient of determination variance, the accuracies of ANN predictions were usually imperceptible better than those of ANFIS predictions