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Öğe Barrow holographic dark energy models in Lyra and general relativity theories(2024) Aktaş, Arzu; Aygün, SezginThis study investigates the Barrow holographic dark energy (BHDE) matter distribution in the Bianchi I universe model in Lyra and General Relativity Theories. To this end, it obtains exact solutions by Hubble parameter, conservation equation, and BHDE energy density equation and supports them with graphics. The results show that the solutions are in harmony with the functioning of the universe and the nature of dark energy. It finally discusses the need for further research.Öğe Behaviors of dark energy and mesonic scalar field for anisotropic universe in f (R) gravity(Elsevier, 2012) Aktaş, Can; Aygün, Sezgin; Yılmaz, İhsanIn this Letter, we study behaviors of dark energy in the form of perfect fluid and mesonic scalar field for Marder space-time which is anisotropic and homogeneous in f (R) gravity. Exact solutions of the modified Einstein field equations in f (R) gravity are obtained by using anisotropic features, of Marder space-time. We do not make any assumptions about f (R) function while we are solving f (R I equations. We have investigated dark energy behaviors in f (R) gravity. We have concluded that dark energy in our model behaves like phantom type. Also we have concluded that mesonic scalar field transforms to another matters into time. In our solutions, obtained f (R) functions existed by dark energy and mesonic scalar field are same like general one accepted in the literature. Furthermore, physical and kinematical quantities are examined for two matters, separately. Finally obtained solutions are discussed. (C) 2011 Elsevier B.V. All rights reserved.Öğe Does magnetized strange quark matter exist in the early universe?(World Scientific Publ Co Pte Ltd, 2022) Kalkan, Sinem; Aktaş, Can; Aygün, SezginIn this paper, we have examined the magnetized strange quark matter (MSQM) distribution in the inhomogeneous anisotropic Einstein-Rosen universe model within the framework of f(R,T) theory and General Relativity (GR) in order to investigate whether there was a magnetic field in the first moments of the universe. With the help of the arbitrary F(r) function, we researched for solutions in both theories for various cases. We have seen that the cubic function F(r) = r(3) gives meaningful results in both theories. We have obtained magnetic field-free strange quark matter solutions for the quadratic and constant states of the arbitrary function F(r). It is seen that the choice of geometry (selection of the F(r) function) has an effect on the presence of the magnetic field. Finally, the physical results are examined on 3D graph.Öğe Domain wall with quark matters cosmological models in f(R,T) theory(Springer, 2024) Çag̃lar, Halife; Taşer, Dog̃ukan; Aygün, SezginIn this article, Ruban universe has been investigated in presence strange quark matter and normal matter coupled with domain wall for f(R, T) alternative gravitation theory. One of the classifying of f(R, T) has been used as f(R, T) = f(R) + 2 μ(T) to obtain modified Einstein field equations (MEFE’s). The solutions of MEFE’s have been attained with help of relationship between metric potentials. The model has been constructed with domain wall matter distribution in form perfect fluid and then strange quark matter and normal matter (NM) have been attached by using equations of states. Also, all solutions have been reduced from f(R, T) theory to General Relativity (GR) by assuming μ= 0 . In last section, all solutions have been concluded with physical and geometrical perspective for f(R,T) and GR theories.Öğe Higher dimensional FRW universe solutions with quark and strange quark matter in creation field cosmology(Elsevier Science Bv, 2016) Aygün, Sezgin; Aktaş, Can; Yılmaz, İhsan; Şahin, MustafaIn this study, firstly we have studied the behavior of quark and strange quark matter for a (n + 2) -dimensional Friedmann-Robertson-Walker (FRW) universe which is homogeneous and isotropic in creation field (C-field) cosmology. Using the deceleration parameter two different exact solutions of the modified Einstein equations in C-field cosmology are obtained. In addition, we obtain exact solutions of the quark and strange quark matter for a (n + 2)-dimensional homogeneous and isotropic static Einstein universe (SEU) and a maximally symmetric de Sitter vacuum universe in four dimensions. Also, using. C = 0 in C-field theory, we get the SEU and de Sitter vacuum universes in Riemann geometry. Finally, some physical and kinematical quantities are discussed. (C) 2016 The Physical Society of the Republic of China (Taiwan). Published by Elsevier B.V. All rights reserved.Öğe Investigation of the teleparallel energy momentum problem for Texture metric(Elsevier B.V., 2023) Aygün, Sezgin; Aktaş, CanIn this paper we have investigated Einstein (E), Bergmann–Thomson (BT) and Landau–Lifshitz (LL) energy–momentum distributions for Texture metric in Teleparallel gravitation (TG) theory. Although these energy–momentum complexes have different definitions, Einstein and Bergmann–Thomson energy distributions give the same result for the Texture metric in TG, while different result is obtained for the Landau–Lifshitz energy distribution. Also, we get different results for the Einstein, BT and LL momentum (M) distributions in TG. In 2010, Aygün (2010) investigated the energy–momentum distributions of Texture and Monopole metrics in General Relativity (GR). However, the same results were obtained for the Einstein and BT energy distributions. These results are the same as those in TG theory for Texture metric.Öğe Investigation of Vibration and Noise Exposures in a Lead Mine(Munzur Üniversitesi, 2024) Yazgı, Seren Türkyılmaz; Aygün, SezginThis study was carried out in 2021 and 2023 to determine the suitability of occupa-tional health and safety features of temperature and vibration, which are physical risk factors, in a lead mine in the Marmara Region. In the lead mine, noise, indoor noise, and vibration measurements were conducted in Gallery A. The obtained results were compared with relevant standards and analyzed using various tables and graphs. Personal noise measurement results decreased proportionally in 2023 compared to 2021, but were operated above the standards. Indoor noise level also increased from 2021 to 2023 and exceeded the standards in 2023. The resolution of vibration meas-urement results appeared in 2023 compared to 2021. Reducing the standards of both noise and rating values is very important to minimize serious health and safety risks for employees, and it is possible to take the necessary precautions with the necessary controls, training, changes in working methods, appropriate protective equipment and new technologiesÖğe İş güvenliği uzmanı olabilecekler için iş güvenliğinin anlamı(Çanakkale Onsekiz Mart Üniversitesi, 2017) Aygün, Sezgin; Öztürk, Ömer Farukİş yerindeki fiziki çevre şartları, çalışma ortamı gibi sebeplerden ötürü işçilerin karşılaşabilecekleri sağlık sorunları ve mesleki sorunların en aza indirilmesi veya ortadan kaldırılması için analizler ve çalışmalar yapılmasına İş Sağlığı ve Güvenliği (İSG) denir. Bu çalışmanın amacı, mühendislik ve teknik eleman adayı olan son sınıf öğrencilerinin iş güvenliği konusunda yaklaşımlarının ve bilgi seviyelerinin belirlenmesidir. Betimsel tipteki bu araştırma Çanakkale Onsekiz Mart Üniversitesi bünyesindeki üç farklı fakülteden toplam 18 bölüm ve 366 katılımcı ile yapılmıştır. Katılımcıların iş güvenliğine yaklaşımlarının belirlenebilmesi için 17 sorudan, iş güvenliği hakkında bilgi düzeylerini ölçebilmek için 20 sorudan oluşan anketler hazırlanmış ve elde edilen sonuçlara göre değerlendirme yapılmıştır. Ankete katılanların % 53'ü Mühendislik Fakültesi, % 30'u Ziraat Fakültesi ve % 17'si Fen Edebiyat Fakültesi öğrencisidir. Elde edilen sonuçlara göre katılımcıların iş güvenliği hakkında bilgi seviyelerinin düşük olduğu gözlenmiştir. Katılımcıların %77,1'i iş güvenliği dersinin üniversitelerin ilgili fakültelerinde zorunlu ders olması gerektiğini belirtmişlerdir. Geliştirilen İSG bilgi ve tutum ölçeklerinde cinsiyete göre anlamlı fark gözlenmez iken, ANOVA testi sonuçlarına göre İSG bilgi düzeylerinde bölümler arasında anlamlı fark elde edilmiştir. Ayrıca, İSG tutum ve bilgi ölçekleri güvenirlik analizi yapılmış Cronbach's Alpha (?) değeri tutum ölçeği için ?=0,838 ve bilgi ölçeği için ?=0,885 değerleri ile yüksek güvenilirlikte elde edilmiştir.Öğe Kütleli (massive) skaler alan kaynaklı bazı kozmolojik modeller ve özellikleri(Çanakkale Onsekiz Mart Üniversitesi, 2005) Aygün, Sezgin; Tarhan, İsmailoz Bu tezde; ideal akışkan, ısı akısı ve kütleli skaler alan ile dolu statik olmayan dönen Gödel tipi bir evrenin dinamiği kozmolojik sabitin varlığında ve yokluğunda incelenmektedir. Özellikle, evrenin oluşumunun ilk çağlarında etkin olduğuna inanılan skaler alanın etkileri ve davranışları özellikleri ile birlikte araştırılmaktadır. Bu amaçla; rotasyon yapan fakat statik olmayan Gödel metriği ile tanımlanan bir evreni dolduran ideal akışkan, ısı akısı ve kütleli skaler alan karışımından oluşan kozmik madde dağılımı için kozmolojik sabit içeren Einstein alan denklemleri elde edilerek çözümler araştırılmıştır. Ayrıca, temel parçacık sınıflaması ve etkileşimleri özetlenerek çözümlerden elde edilen sonuçların fiziksel ve geometrik özellikleri de tartışılmıştır. Anahtar Kelimeler: Kütleli Skaler Alan, Isı Akısı, İdeal Akışkan, Kozmolojik Sabit, Gödel Modeli, Kozmolojik Modeller, Kozmik Mikrodalga Fon Amzotropisi.Öğe Magnetized strange quark matter solutions in f(R, T) gravity with cosmological constant(Elsevier Science Bv, 2017) Aktaş, Can; Aygün, SezginIn this research, we have studied magnetized strange quark matter (SQM) solutions for Friedmann-Robertson-Walker (FRW) universe in f(R, T) gravity. To obtain exact solutions of modified field equations we have used f(R, T) = R + 2 f(T) and f(R, T) = f(1)(R) + f(2)(T) models given by Harko et al. (Harko et al. in Phys. Rev. D 84: 024020, 2011) and f(R, T) = R + f(3)(T) model (here f(3) is an arbitrary function) with cosmological constant Lambda. For t -> 8 we obtain p = -rho dark energy situation with small constant values of cosmological constant in three different f (R, T) gravitation models. In our solutions magnetic field does not observe also we have transformed our solutions from FRW universe to Static Einstein Universe (SEU) and we get f(R, T) gravity results for SEU universe. Finally we discussed our physical solutions. (C) 2016 The Physical Society of the Republic of China (Taiwan). Published by Elsevier B.V. All rights reserved.Öğe Marder type universe with bulk viscous string cosmological model inf(R;T)gravity(2017) Aygün, SezginIn this study, we have investigated homogeneous and anisotropic Marder space-time with bulk viscous stringmatter distribution inf(R;T) gravity. For this aim we have used the anisotropy feature ( xx ) of Marder space-time anda deceleration parameter in two differentf(R;T) models. We have obtained bulk viscous matter distribution solutionsinf(R;T) gravity. Finally, some kinematical and physical properties are discussed.Öğe Moller energy momentum distribution for higher dimensional Morris Thorne wormhole(Elsevier B.V., 2024) Aygün, Sezgin; Aktaş, CanIn this study, Møller energy momentum distribution is investigated for the higher dimensional Morris Thorne wormhole (MTW) in general relativity theory (GR) and results are given for the MTW in (4+1) and (5+1) dimensions. In addition, using the MTW, Møller energy and momentum distributions were investigated for 4-dimensional Morris Thorne wormhole, Hyperbolic Morris Thorne wormhole, Zero Tidal wormhole, Zero Density wormhole, Visser–Kar–Dadhich wormhole and (2+1) dimensional Morris Thorne wormhole. Except for the Zero Tidal wormhole model, we obtained the Møller energy distribution as well defined and non-zero in all other wormhole models. Besides, our results are in agreement with Aygün and Yılmaz and support Lesnner's idea for Møller energy momentum definition.Öğe Non-existence of a massive scalar field for the Marder universe in Lyra and Riemannian geometries(Elsevier, 2012) Aygün, Sezgin; Aktaş, Can; Yılmaz, İhsanIn this paper, we have studied a massive scalar field for a Marder type universe in the context of Lyra and Riemannian geometries. From the exact solutions obtained we show that the massive scalar field does not survive in Lyra and Riemannian geometries for an anisotropic Marder type universe. Therefore we have solved the massless scalar field problem in Lyra and Riemann geometries for two cases. Also we have obtained vacuum solutions for homogeneous and anisotropic Marder space time in Lyra geometry and the solutions obtained are compared by considering Lyra and Riemann geometries. Finally, some physical and kinematical properties are discussed by using graphics. (C) 2011 Elsevier B.V. All rights reserved.Öğe Quadratic equation of state solutions with Λ in f(R, T) gravitation theory(Indian Assoc Cultivation Science, 2019) Aygün, Sezgin; Aktaş, Can; Mishra, B.In this paper, we have investigated the perfect fluid matter distribution with different quadratic equation of states (EoS) parameters in the form (i) p = p(0) + alpha rho + beta rho(2), (ii) p= alpha rho + rho(2)/rho(c) and (iii) p = alpha rho(2) - rho for Marder space-time in f(R,T) theory. The field equations of f(R,T) gravity with the inclusion of cosmological parameter Lambda have been derived for the first case of Harko et al. (Phys Rev D 84(2):024020, 2011) in the form f(R,T)=R + 2f(T). The physical parameters are investigated and its properties are studied.Öğe Quark and strange quark matter solutions for higher dimensional FRW universe in Lyra geometry(Springer Heidelberg, 2015) Aygün, Sezgin; Çağlar, Halife; Taşer, Doğukan; Aktaş, CanIn this study, we have investigated the higher dimensional flat Friedmann-Robertson-Walker (FRW) universe for a cloud of string with perfect fluid attached quark and strange quark matter (SQM) in Lyra geometry. Generalized (n + 2) dimensional flat FRW universe solutions have been achieved with the aid of equation of states (EOS) and deceleration parameter (q). From the field equations, we have obtained that the cloud of string with perfect fluid does not survive. Since the string tension density vanishes (lambda = 0) for this model, as a result, the cloud of string with perfect-fluid-attached quark and strange quark matter energy-momentum tensor is automatically transformed into a perfect-fluid-attached quark and strange quark matter energy-momentum tensor. Also, our solutions agree with Halford's study. beta(2) behaves like a cosmological constant. When t -> infinity the pressure of quark matter and the density go to zero, then, the quark matter transforms into another matter with time. Also our quark matter solutions are in agreement with the present idea.Öğe Relationship between magnetic field and anisotropy parameter in gravitation theories(World Scientific Publ Co Pte Ltd, 2018) Aktaş, Can; Aygün, Sezgin; Sahoo, Pradyumn KumarThe magnetized strange quark matter (MSQM) solutions are obtained for a Marder type universe using constant deceleration parameter. The exact solutions of field equations are obtained for f(R,T) = R 2f(T) model given by [T. Harko et al., Phys. Rev. D 84, 024020 (2011)] with cosmological term. Also, we have obtained General Relativity (GR) solutions for MSQM distributions. For t -> infinity, we get the dark energy model, i.e. p -> -B-c, rho -> B-c and omega = -1. However, for t -> infinity, we find the cosmological constant A as negative in f (R, T) theory and GR. These results agree with [S. Aygun et al., Astrophys. Space Sci. 361, 380 (2016); C. Aktas and S. Aygun, Chinese T. Phys. 55, 71 (2017); P. K. Sahoo et al., Mod. Phys. Lett. A 32, 1750105 (2017)] in f(R,T) theory. The physical consequences of our obtained models are discussed at the end.Öğe Scalar Field Cosmology in f(R,T) Gravity with Λ(Pleiades Publishing, 2018) Aygün, Sezgin; Aktaş, Can; Sahoo, Pradyumn Kumar; Bishi, Binaya K.We study the behavior of cosmological parameters, massive and massless scalar fields (normal or phantom) with a scalar potential in f(R, T) theory of gravity for a flat Friedmann-Robertson-Walker (FRW) universe. To get exact solutions to the modified field equations, we use the f(R, T) = R + 2f(T) model by Harko et al. (T. Harko et al., Phys. Rev. D 84, 024020 (2011)), where R is the Ricci scalar and T is the trace of the energy momentum tensor. Our cosmological parameter solutions agree with the recent observational data. Finally, we discuss our results with various graphics. © 2018, Pleiades Publishing, Ltd.Öğe Skaler alan kaynaklı bazı kozmolojik modeller(Çanakkale Onsekiz Mart Üniversitesi, 2008) Aygün, Sezgin; Baysal, Hüsnü; Tarhan, İsmailBu çalışmada, ilk olarak statik olmayan Gödel evreninde viskoz akışkanlı, ısı akılı ve kütleli (massive) skaler alanlı madde topluluğu çözümleri kaynak yoğunluğunun değişimine göre ayrıntılı olarak incelenmiştir. Bununla beraber, yine statik olmayan Gödel metriği için sicim bulutuna iliştirilmiş acayip kuark madde (SQM), ısı akısı ve kütleli skaler alandan oluşan madde topluluğunun çözümleri kaynak yoğunluğuna bağlı olarak elde edilmiştir. Daha sonra statik Gödel evreninde kaynak yoğunluğuna göre kütleli skaler alanlı ve ideal akışkanlı çözümler ardından sicim bulutuna iliştirilmiş acayip kuark maddeli ve kütleli skaler alanlı çözümler araştırılmıştır.Öğe Strange quark matter solutions for Marder's universe in f (R, T) gravity with Λ(Springer, 2016) Aygün, Sezgin; Aktaş, Can; Yılmaz, İhsanIn this paper, we investigate homogeneous cylindrically symmetric Marder's universe in the presence of strange quark matter (SQM) source in f (R, T) gravity with cosmological constant Lambda. For this aim we have used the anisotropy feature (sigma(x)(x)/theta) of Marder type universe and equation of state (EoS) strange quark matter to obtain solutions in two classes f (R, T) gravity (Harko et al. in Phys. Rev. D 84:024020, 2011). Finally, some physical and kinematical properties are discussed.Öğe Teleparallel energy-momentum distribution of various black hole and wormhole metrics(World Scientific Publ Co Pte Ltd, 2018) Aygün, Sezgin; Baysal, Hüsnü; Aktaş, Can; Yılmaz, İhsan; Sahoo, P. K.; Tarhan, İsmailUsing the Einstein, Bergmann-Thomson (BT) and Landau-Lifshitz (LL) energy and momentum formulations in teleparallel gravity (TG), we obtain the total energy and momentum distributions for phantom black hole metric. We get different energy distributions similar to the earlier study and the momentum distributions vanish for phantom black hole metric in TG. These momentum solutions agree with the study of Sahoo et al. in general relativity. However, using Einstein, Bergmann-Thomson and Landau-Lifshitz energy and momentum complexes, we investigate regular black hole, asymptotically flat wormhole, anti-de Sitter wormhole and Ellis wormhole solutions in TG. We obtain i) same BT and LL energy density solutions for regular black hole metric, (ii) same and zero energy distribution for asymptotically flat wormhole, (iii) proportion with Einstein and BT energy density solutions for anti-de Sitter wormhole, (iv) same and negative Einstein and BT energy density solutions for Ellis wormhole in TG.
