Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis F (metric-Affine) Gravity: Disformal and Cross-Curvature Effects(Izmir Institute of Technology, 2019) Samaner, Çağlar; Demir, Durmuş Ali; Demir, Durmuş AliThe present thesis consists of two main studies, in the first part, after giving a brief formulation of gravity theories on the metric, affine and metric-affine frameworks, we study the effects of the disformal coupling term \epsilon R_{\mu\nu} V^mu V^nu. We track the effects of disformal term up to field equations, then construct the Einstein tensor G_{\mu\nu} and subsequently identify an effective energy-momentum tensor T_{\mu\nu} to extract effective energy density and pressure. We conclude the first part by comparing the results of metric-affine disformal theory with metrical disformal theory. In the second part, we study the cosmological effects of cross-curvature theory with the functional F (R,R). We derive the both Friedmann equations with the general functional F (R, R) and compare our findings with the known F (R) theory results.Master Thesis Adaptation of Digital Electronic Into Detector Systems Numexo2 in Exotic Nuclei Research(Izmir Institute of Technology, 2017) Şahin, Elif; Demir, Durmuş Ali; Ertürk, SefaThe main purpose of this thesis is to introduce and show the performance and capabilities of the newly developed digital electronic namely NUMEXO2, which has been tested, coupled with EXOGAM2 (EXOtic GAMma array) detector at GANIL in France. This electronic has been developed due to the necessity of high rate signal transferring capacity when a radioactive ion beam is applied in order to produce exotic nuclei and to understand their nuclear structure. NUMEXO2 will be used both with stable beam and radioactive beam experiment not only to have high rate digital experimental data during the experiment but also will be used to obtain good high resolution both for energy and time. In this thesis, we will try to explain the design, verification, and performance of the NUMEXO2. In order to show the performance of NUMEXO2, we will present the result from test experiment performed in France at GANIL, nuclear research centre.Master Thesis The Higgs Boson and Right-Handed Neutrinos in Supersymmetric Models(Izmir Institute of Technology, 2016) Özdal, Özer; Demir, Durmuş AliThe results represented in this thesis are based on our work in [1], where the predictions on the mass spectrum and Higgs boson decays are investigated in the supersymmetric standard model extended by U(1)B-L symmetry (BLSSM). The model requires two singlet Higgs fields, which are responsible for the radiative breaking of U(1)B-L symmetry. Radiative breaking of U(1)B-L symmetry yields right-handed neutrino of mass at the TeV scale. It predicts degenerate right-handed neutrino masses (1:7 2.2TeV) as well as the right-handed sneutrinos of mass . 4 TeV. The presence of right-handed neutrinos and sneutrinos trigger the baryon and lepton number violation processes, until they decouple from the Standard model particles. Besides, the model predicts rather heavy colored particles; m~t;m~b & 1:5 TeV, whilem~ & 100 GeV andm~ 1 & 600 GeV. Even though the implications on the SM-like Higgs boson are similar to minimal supersymmetric standard model (MSSM), BLSSM can predict another Higgs boson lighter than 150 GeV. We find that the second Higgs boson can be degenerate with the lightest CP-even Higgs boson of mass about 125 GeV and contribute to the Higgs decay into two photons. In addition, if it is not degenerate, it can provide a possible explanation for the excess in h ! 4l at the mass scale 145 GeV.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.Master Thesis Entropic Tunneling Time and Its Applications(Izmir Institute of Technology, 2014) Güner, Tuğrul; Demir, Durmuş AliQuantum tunneling is one of the most interesting consequences of quantum behaviour. However, even though it is known and understood well, due to non-existence of a time operator in quantum mechanics, estimating what time it takes for a particle to cross a barrier remains an open question. There are some attempts like phase time, dwell time, Larmor clock, Buttiker-Landauer, and Feynman Path Integral approaches. These definitions do not agree with each other and with experiment. In this thesis work, tunneling time problem is studied in a rather new context. Knowing time necessitates momentum, we deal with momentum state vectors and define entropy accordingly. This entropy, which gives a temperature, defines a thermal energy in the tunneling region. With this thermal energy and uncertainty principle, resulting time deviation of the particle from the classically instantaneous is stated as our tunneling time, entropic tunneling time. Moreover, we compare this tunneling time with recent experiments in detail, and find that, it is in very good agreement with the data. Then, we apply this entropic tunneling time to α - decay, STM and creation of universe from nothing to predict natural time scale of these processes.Master Thesis Tunneling in Polymer Quantization and Quantum Zeno Effect(Izmir Institute of Technology, 2014) Sargın, Ozan; Demir, Durmuş AliPolymer quantization is a non-standard and exotic representation of the canonical commutation relations which is introduced in the context of loop quantum gravity to investigate the low energy limit of this non-perturbative quantization of gravity. It is one of the representations of the Weyl-Heisenberg algebra which is inequivalent to the standard Schr¨odinger representation. Since this representation is inequivalent to Schr¨odinger mechanics, by Stone-von Neuman uniqueness theorem there should not be a one to one correspondence between the operators of the two representations. It turns out that, one can not define the position and momentum operators simultaneously in this construction. In this work, we use the standard position operator and a second operator which is the analog of ^p. To define an operator similar to the momentum operator ^p, one needs to use a regularization length scale which can not be removed and stays as a free parameter in the theory. This free parameter is interpreted to descend from the fundamental discreteness of space in loop quantum gravity. As another application of the polymer quantization scheme, in this work we investigate the one dimensional quantum mechanical tunneling phenomenon from the perspective of polymer representation of a non-relativistic point particle, derive the transmission and reflection coefficients and show that they add up to one which is the requirement of probability conservation. Since any tunneling phenomenon inevitably evokes a tunneling time we attempt an analytical calculation of tunneling times by defining an operator well suited in discrete spatial geometry. We expand our time expression in a Maclaurin series around zero polymer length scale and arrive at results which hint at appearance of the Quantum Zeno Effect in polymer framework. Quantum Zeno effect is the inhibition of a quantum system from making a transition from an initial state to a final state. And in summary, as a result of our work we can say that discretization of space leads to the Quantum Zeno effect.Master Thesis The Higgs Sector of the Mssm With General Soft Breaking Terms(Izmir Institute of Technology, 2008) Sabancı, Aslı; Demir, Durmuş AliThis thesis is basically established upon an analysis of determining the effects of the non-holomorphic soft supersymmetry breaking terms on the mass spectrum of the minimal supersymmetric Standard Model (MSSM). We give an overview concerning the fundamental concepts of supersymmetry (SUSY) after providing a brief discussion about the problems of Standard Model (SM) of particle physics. Then we discuss in detail that SUSY is not the exact symmetry of nature and it must be broken. In general, the breakdown of the global supersymmetry is parameterized by a set of operators. These operators could be both holomorphic or non-holomorphic in structure. Hence, in theories like the (MSSM) that do not contain any gauge singlets, these non-holomorphic supersymmetry breaking terms are soft and do not pose any problem for gauge hierarchy.In this thesis, in particular we study the impacts of the non-holomorphic softbreaking with the chargino sector so as to single out the effects of non-holomorphic trilinear couplings from the . parameters. Since the aforementioned sectors are two of the prime concerns of experiments at the LHC, we expect that our results will be testable in near future.Master Thesis Family Non-Universal U(1)' Model(Izmir Institute of Technology, 2008) Hayreter, Alper; Demir, Durmuş AliThis thesis work is devoted to an analysis of dilepton signatures of family nonuniversal U(1)' model. We first provide a brief overview of Standard Model of particle physics and Supersymmetry then we give an introduction to basic concepts of Minimal Supersymmetric StandardModel (MSSM) and necessities to extend theMSSMwith additional symmetry groups. Later we review various existing U(1). models, then we discuss the effects and results of family non-universality in current and future colliders. The supersymmetric models extending theMSSMby an additional Abelian gauge factor U(1). in order to solve the . problem do generically suffer from anomalies disrupting the gauge coupling unification found in the MSSM. The anomalies are absent if the minimal matter content necessitated by the . problem is augmented with exotic matter species having appropriate quantum numbers. Recently, it has been shown that anomaly cancellation can also be accomplished by introducing family non-universal U(1). charges and non-holomorphic soft-breaking terms (Demir, et al. 2005) and keeping the matter content minimal without exotic particles. We discuss collider signatures of anomaly-free family non-universal U(1). model by analyzing dilepton production in future colliders. We notice that, both at LHC and NLC, one can establish existance (or absence) of such a Z. boson by simply comparing the number of dilepton production events for electron, muon and tau lepton (Hayreter 2007).Master Thesis Higher Curvature Gravity in Large Extra Dimension: Phenomenological Implications(Izmir Institute of Technology, 2007) Tanyıldızı, Şükrü Hanif; Demir, Durmuş AliThis thesis is devoted to a detailed study of the higher curvature gravity and its phenomenological implications in large extra dimensions. This work is intended as a discussion of effective interactions among brane matter induced by modifications of higher dimensional Einstein gravity via the replacement of Einstein-Hilbert term with a generic function f(R) of the curvature scalar R.In this work, following the introductory chapters on extra dimensions and higher curvature gravity in large extra dimensions, we derive the graviton propagator and then we analyze impact of virtual graviton exchange on interactions among brane matter. We find that f(R) gravity effects are best probed by high-energy processes involving massivegauge bosons, heavy fermions or the Higgs boson. We perform a comparative analysis of the predictions of f(R) gravity and of Arkani.Hamed, Dimopoulos and Dvali (ADD) scenario, and find that the former competes with the latter when f00(0) is positive and comparable to the fundamental scale of gravity in higher dimensions (Demir and Tanyıldızı 2006). In addition, we briefly discuss graviton emission from the brane as well as itsdecays into brane-localized matter and we find that they hardly compete with the ADD expectations.Consequently, we discussed that possible existence of higher-curvature gravitational interactions in large extra spatial dimensions opens up various signatures to be confronted with existing and future collider experiments.Master Thesis Renormalization Group Invariants in Minimal Supersymmetric Standard Model(Izmir Institute of Technology, 2006) Mutlu, Sevdiye; Demir, Durmuş AliThis thesis work is devoted to a detailed study of the renormalization group invariants (RG invariants) in minimal supersymmetric standard model (MSSM). The RG invariants are those Lagrangian parameters or combinations of the parameters, which exhibit no dependence on the energy scale up to the loop order with which the renormalization group equations (RGEs) are constructed. In this work, following an introductory chapter on standard model of electroweak and strong interactions as well as supersymmetry and supersymmetric field theories, we discuss construction of renormalization group equations in supersymmetric models, in particular, the minimal supersymmetric standard model with holomorphic and non-holomorphic soft terms. We finally concentrate on construction and phenomenological implications of the RG invariants in the minimal supersymmetric standard model with and without non-holomorphic supersymmetry breaking terms.