Gültekin, Kemal
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Gultekin, Kemal
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04.05. Department of Pyhsics
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Former Staff
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Scholarly Output
8
Articles
5
Views / Downloads
31001/2115
Supervised MSc Theses
1
Supervised PhD Theses
1
WoS Citation Count
12
Scopus Citation Count
12
Patents
0
Projects
0
WoS Citations per Publication
1.50
Scopus Citations per Publication
1.50
Open Access Source
7
Supervised Theses
2
| Journal | Count |
|---|---|
| European Physical Journal C | 2 |
| European Physical Journal Plus | 2 |
| Journal of Cosmology and Astroparticle Physics | 1 |
| Modern Physics Letters A | 1 |
Current Page: 1 / 1
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8 results
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Now showing 1 - 8 of 8
Article Citation - WoS: 2Citation - Scopus: 2Particle Physics Processes in Cosmology Through an Effective Minkowski Space Formulation and the Limitations of the Method(Springer, 2021) Erdem, Recai; Gültekin, KemalWe introduce a method where particle physics processes in cosmology may be calculated by the usual perturbative flat space quantum field theory through an effective Minkowski space description at small time intervals provided that the running of the effective particle masses are sufficiently slow. We discuss the necessary conditions for the applicability of this method and illustrate the method through a simple example. This method has the advantage of avoiding the effects of gravitational particle creation in the calculation of rates and cross sections i.e. giving directly the rates and the cross sections due to the scatterings or the decay processes.Correction Correction To: “curved Space and Particle Physics Effects on the Formation of Bose–einstein Condensation Around a Reissner–nordstrøm Black Hole”(Springer, 2022) Erdem, Recai; Demirkaya, Betül; Gültekin, KemalAfter this correction Fig. 1 in [1] is replaced by Fig. 1 above which is essentially the same as the one in [1]. Figure 2 in [1] now becomes irrelevant. Figure 3 in [1] is replaced by Fig. 2 above which is essentially the same as the one in [1].Article Citation - WoS: 2Citation - Scopus: 2Curved Space and Particle Physics Effects on the Formation of Bose-Einstein Condensation Around a Reissner-Nordstrom Black Hole(Springer, 2021) Erdem, Recai; Demirkaya, Betül; Gültekin, KemalWe consider two scalar fields interacting through a chi*chi phi*phi term in the presence of a Reissner-Nordstrom black hole. Initially, only chi particles are present. We find that the produced phi particles are localized in a region around the black hole and have a tendency toward condensation provided that phi particles are much heavier than the chi particles. We also find that such a configuration is phenomenologically viable only if the scalars and the black hole have dark electric charges.Master Thesis Affine Dynamics With Torsion(Izmir Institute of Technology, 2016) Gültekin, Kemal; Demir, Durmuş AliIn this study, we give a thorough analysis of a general affine gravity with torsion. After a brief exposition of the affine gravities considered by Eddington and Schr¨odinger, we construct and analyze different affine gravities based on determinants of the Ricci tensor, the torsion tensor, the Riemann tensor and their combinations. In each case we reduce equations of motion to their simplest forms and give a detailed analysis of their solutions. Our analyses lead to the construction of the affine connection in terms of the curvature and torsion tensors. Our solutions of the dynamical equations show that the curvature tensors at different points are correlated via non-local, exponential rescaling factors determined by the torsion tensor.Article Citation - WoS: 2Citation - Scopus: 3Affine Dynamics With Torsion(Springer Verlag, 2016) Gültekin, KemalIn this study, we give a thorough analysis of a general affine gravity with torsion. After a brief exposition of the affine gravities considered by Eddington and Schrödinger, we construct and analyze different affine gravities based on the determinants of the Ricci tensor, the torsion tensor, the Riemann tensor, and their combinations. In each case we reduce equations of motion to their simplest forms and give a detailed analysis of their solutions. Our analyses lead to the construction of the affine connection in terms of the curvature and torsion tensors. Our solutions of the dynamical equations show that the curvature tensors at different points are correlated via non-local, exponential rescaling factors determined by the torsion tensor.Article A Metric for Gravitational Collapse Around a Schwarzschild Black Hole(World Scientific Publishing, 2023) Erdem, Recai; Demirkaya, Betül; Gültekin, KemalWe consider the problem of gravitational collapse of a fluid under the effect of a small Schwarzschild black hole (e.g. a primordial one). We assume the fluid initially may be approximated by a uniform homogeneous dust. Starting from this configuration we obtain a class of metrics under some physically justified assumptions. We find that the metric we obtain includes the dust collapse as a subcase. After discussing some basic properties of the solution, we discuss the case of dust collapse in more detail. We find that the radial and tangential pressures outside the horizon may take positive or negative values depending on the values of the parameters.Doctoral Thesis Bose-Einstein Condensation and Black Holes in Dark Matter and Dark Energy(01. Izmir Institute of Technology, 2023) Gültekin, Kemal; Erdem, RecaiThe main aim of this study is to reveal curved space and particle physics effects on the formation of Bose-Einstein condensate scalar fields in cosmology and around a black hole. Cosmological scalar fields for dark energy and dark matter may be considered as a result of Bose-Einstein condensation. In this regard, our main attention will be devoted to Bose-Einstein condensates in curved space. By considering the dynamics of a scalar Bose-Einstein condensation at a microscopic level, we first study the initial phase of the formation of condensation in cosmology. To this end, we initially introduce an effective Minkowski space formulation that enables considering only the effect of particle physics processes, excluding the effect of gravitational particle production and enabling us to see cosmological evolution more easily. Then, by using this formulation, we study a model with a trilinear coupling that induces the processes. After considering the phase evolution of the produced particles, we find that they evolve towards the formation of a Bose-Einstein condensate if some specific conditions are satisfied. In principle, the effective Minkowski space formulation introduced in this study can be applied to particle physics processes in any sufficiently smooth spacetime. In this regard, we also analyse if a condensate scalar field is realized in the spacetime around a Reissner - Nordstrøm black hole. We find that the produced particles of particle physics processes are localized in a region around the black hole and have a tendency toward condensation if the emerged particles are much heavier than ingoing particles. We also find that such a configuration is phenomenologically viable only if the scalars and the black hole have dark electric charges. Finally, we consider gravitational collapse around Schwarzschild black holes and form a first step towards a study in future about the effects of gravitational collapse on Bose-Einstein condensation.Article Citation - WoS: 6Citation - Scopus: 5A Mechanism for Formation of Bose-Einstein Condensation in Cosmology(IOP Publishing, 2019) Erdem, Recai; Gültekin, KemalWe introduce a toy model of scalar particles with a trilinear scalar coupling in cosmology. The trilinear coupling phi(2)chi causes production of non-relativistic phi particles through the process chi chi -> phi phi where, initially, only relativistic chi particles are present. We consider the initial times of chi chi -> phi phi and observe that the curved space effects promote formation of Bose-Einstein condensate of phi particles.