WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Conference Object Towards the Solution of Cosmological Constant and Zero Point Energy Problems Through Metric Reversal Symmetry(IOP Publishing Ltd., 2009) Erdem, RecaiIn this talk I review my studies on metric reversal symmetry and their further implications. The talk is mainly concentrated on the relevance of the metric reversal symmetry to the solutions of the cosmological constant and zero point energies. However the use of metric reversal symmetry to hide higher Kaluza-Klein modes at the scales larger than the size of extra dimensions is also discussed, and speculations on its possible relevance to Pauli-Villars and Lee-Wick model are also briefly mentioned.Article Citation - WoS: 7Citation - Scopus: 8A Way To Get Rid of Cosmological Constant and Zero-Point Energy Problems of Quantum Fields Through Metric Reversal Symmetry(IOP Publishing Ltd., 2008) Erdem, RecaiIn this paper, a framework is introduced to remove the huge discrepancy between the empirical value of the cosmological constant and the contribution to the cosmological constant predicted from the vacuum energy of quantum fields. An extra-dimensional space with metric reversal symmetry and R2 gravity (that reduces to the usual R gravity after integration over extra dimensions) is considered to this end. The resulting four-dimensional energy-momentum tensor (obtained after integration over extra dimensions) consists of terms that contain off-diagonally coupled pairs of Kaluza-Klein modes. This, in turn, generically results in the vanishing of the vacuum expectation value of the energy-momentum tensor for quantum fields, and offers a way to solve the problem of huge contribution of quantum fields to the vacuum energy density.Article Citation - WoS: 8Citation - Scopus: 9A Symmetry for the Vanishing Cosmological Constant(IOP Publishing Ltd., 2007) Erdem, RecaiTwo different realizations of a symmetry principle that impose a zero cosmological constant in an extra-dimensional set-up are studied. The symmetry is identified by multiplication of the metric by minus one. In the fist realization of the symmetry this is provided by a symmetry transformation that multiplies the coordinates by the imaginary number i. In the second realization this is accomplished by a symmetry transformation that multiplies the metric tensor by minus one. In both realizations of the symmetry the requirement of the invariance of the gravitational action under the symmetry selects out the dimensions given by D ≤ 2(2n + 1), n ≤ 0, 1, 2..., and forbids a bulk cosmological constant. Another attractive aspect of the symmetry is that it seems to be more promising for quantization when compared to the usual scale symmetry. The second realization of the symmetry principle is more attractive in that it is possible to make a possible brane cosmological constant zero in a simple way by using the same symmetry, and the symmetry may be identified by reflection symmetry in extra dimensions.Article 1/Nc Expansion and Anomaly Cancellation in the Presence of Electroweak Interactions(IOP Publishing Ltd., 1998) Erdem, RecaiWe study the question of a consistent formulation of the 1/Nc expansion in the presence of electroweak interactions. We show that in some cases the previous formulation leads to an unrealistic picture. We improve the scheme. We derive the corresponding hypercharge and electric charge values of fermions under the requirement that the standard model in the large-Nc limit should be free of chiral gauge anomalies. We find that the resulting hypercharge and the electric charge values for quarks are the same as for the standard model.