WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
Browse
20 results
Search Results
Now showing 1 - 10 of 20
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].Other Citation - WoS: 1Türkiye’de Lisansüstü Eğitim Üzerine Gözlem ve Öneriler: Inter-university Modeli(2021) Erdem, RecaiTürkiye'deki henüz gelişimini tamamlamamış üniversitelerde de bilimsel ve akademik yeterlilikleri üst düzeyde öğretim üyeleri bulunabilmektedir. Fakat söz konusu üniversitelerdeki hem toplam öğretim üyesi sayısının hem de uluslararası düzeydeki öğretim üyesi oranının düşüklüğü nedeniyle bu üniversitelerdeki lisansüstü eğitiminin yeterli düzeyde olup olmadığı konusu zaman zaman tartışılabilmektedir. Öte yandan, uluslararası düzeydeki öğretim üyesi sayımızın ihtiyacımızın çok gerisinde olması nedeniyle henüz gelişimini tamamlamamış üniversitelerdeki kaliteli öğretim üyesi potansiyelini etkin bir şekilde kullanmamız gerekmektedir. Bu yazıda, üniversitelerimizdeki, özellikle de gelişme sürecindeki üniversitelerimizdeki öğretim üyesi potansiyelini lisansüstü eğitimin kalitesini artırmada etkin bir şekilde kullanmayı amaçlayan inter-university modeli tartışılmaya açılmaktadır. Bu bağlamda, bu makalede önce, ABD, Kanada, Hindistan gibi ülkelerde uygulanmakta olan çeşitli inter-university modellerine değinilmiş ve daha sonra ise Türkiye'nin ihtiyaçları ve şartlarına uygun bir inter-university modelinin ana hatları önerilmiştir.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.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.Conference Object Can Cpt Be Violated Through Extended Time Reversal?(World Scientific Publishing, 2001) Erdem, Recai; Ufuktepe, ÜnalWe consider the implications of the extension of time reversal through Wigner types and group extensions. We clarify its physical content and apply the results in a toy model. Finally we point out the possibility of violation of CPT in this framework.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.Article Citation - WoS: 607Citation - Scopus: 736Black Holes, Gravitational Waves and Fundamental Physics: a Roadmap(IOP Publishing, 2019) Barack, Leor; Cardoso, Vitor; Nissanke, Samaya; Sotiriou, Thomas P.; Askar, Abbas; Belczynski, Chris; Erdem, RecaiThe grand challenges of contemporary fundamental physics dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'.Article Citation - WoS: 9Citation - Scopus: 9Is It Possible To Obtain Cosmic Accelerated Expansion Through Energy Transfer Between Different Energy Densities?(Elsevier Ltd., 2017) Erdem, RecaiThe equation of state of an energy density may be significantly modified by coupling it to another energy density. In the light of this observation we check the possibility of producing cosmic accelerated expansion in this way. In particular we consider the case where matter is converted to radiation (or vice versa by particle physics processes). We find that cosmic accelerated expansion can be obtained in this way only if an intermediate state with negative equation of state forms during the conversion.Article It Is Sufficient To Set the Cosmological Constant To Zero or To a Small Number at an Initial Time(TUBITAK, 2016) Erdem, RecaiI point out a simple but usually overlooked fact about the cosmological constant problem: to solve the cosmological constant problem it is sufficient to find a symmetry or mechanism that sets the cosmological constant to zero or to a tiny value at some time in the past, provided that general relativity is the relevant theory of gravity, and the energy-momentum tensor (excluding the part of the form of a cosmological constant) is conserved. The relevant symmetry or mechanism need not be applicable today. Any additional cosmological constant term induced by a phase transition in the energy-momentum tensor in this case is compensated by a shift in the cosmological constant term of gravitational origin.Article Citation - WoS: 1Citation - Scopus: 2Finite Number of Kaluza-Klein Modes, All With Zero Masses(World Scientific Publishing Co. Pte Ltd, 2010) Erdem, RecaiKaluzaKlein modes of fermions in a five-dimensional toy model are considered. The number of Kaluza-Klein modes that survive after integration over extra dimensions is finite in this space. Moreover, the extra dimensional piece of the kinetic part of the Lagrangian in this space induces no mass for the higher Kaluza-Klein modes on contrary to the standard lore. © 2010 World Scientific Publishing Company.