Local cosmic strings in Brans-Dicke theory with a cosmological constant

It is known that Vilenkin's phenomenological equation of state for static straight cosmic strings is inconsistent with Brans-Dicke theory. We will prove that, in the presence of a cosmological constant, this equation of state is consistent with Brans-Dicke theory. The general solution of the full nonlinear field equations, representing the interior of a cosmic string with a cosmological constant is also presented.Comment: 5 pages, Revte

Multi-Scalar-Tensor Equivalents for Modified Gravitational Actions

A general scheme of constructing scalar-tensor equivalents to modified gravitational actions are studied using the algebra of exterior differential forms and the first order formalism that allows an independent connection and coframe. By introducing appropriate constraints on the connection, pseudo-Riemannian cases as well as non-Riemannian cases are discussed for various gravitational models. The issue of the dynamical degree of freedom for the resulting scalar fields is discussed at the level of the field equations. Explicit scalar-tensor equivalents for gravitational models based on $f(R)$ models, the quadratic curvature lagrangians and the models involving the gradients of the scalar curvature are presented. In particular, explicit ST equivalence for gravitational lagrangians popular in some cosmological models are constructed.Comment: V1:17 pages in two column format, revtex; V2: 19 pages, an appendix and references added, published versio

Catalogue Note on Taner Ceylan's 1879 (2011)

In this recent piece from his Lost Painting Series, following 1881 (2010) and 1923 (2010), the photorealist painter Taner Ceylan engages with the questions of history and Orientalism by creating yet another visual allegory. The mischievous gaze of the smoking Ottoman boy in 1881 and the homoerotic farewell scene in 1923 are followed this time by an ingenious montage of Pascal Sébah's photograph from the 1880s and Gustave Courbet's L'Origine du monde (The Origin of the World, 1866). In this intricately crafted oil painting, Ceylan juxtaposes different yet related histories of artistic style and connoisseurship to trigger a rethinking of Orientalism, femininity, the veil and the gaze. Recovering and drawing together forgotten legacies and silenced voices in a brilliantly imagined new setting, Ceylan invites the viewer to look behind the veil of Orientalism and the politics of representation. Rather than offering a corrective, the artist amalgamates irony, playfulness and realism to recast Orientalism as heterogeneous and susceptible to negotiation, contestation and even subversion

On Stationary Axially Symmetric Solutions in Brans-Dicke Theory

Stationary, axially symmetric Brans-Dicke-Maxwell solutions are reexamined in the framework of the Brans-Dicke (BD) theory. We see that, employing a particular parametrization of the standard axially symmetric metric simplifies the procedure of obtaining the Ernst equations for axially symmetric electrovacuum space-times for this theory. This analysis also permits us to construct a two parameter extension in both Jordan and Einstein frames of an old solution generating technique frequently used to construct axially symmetric solutions for BD theory from a seed solution of general relativity. As applications of this technique, several known and new solutions are constructed including a general axially symmetric BD-Maxwell solution of Plebanski-Demianski with vanishing cosmological constant, i.e. the Kinnersley solution and general magnetized Kerr-Newman--type solutions. Some physical properties and the circular motion of test particles for a particular subclass of Kinnersley solution, i.e., a Kerr-Newman-NUT--type solution for BD theory, are also investigated in some detail.Comment: V2: 18 pages, published version; some references and section VI is added. V1:17 pages, Revte

Linearized modified gravity theories with a cosmological term: advance of perihelion and deflection of light

Two different ways of generalizing Einstein's general theory of relativity with a cosmological constant to Brans-Dicke type scalar-tensor theories are investigated in the linearized field approximation. In the first case a cosmological constant term is coupled to a scalar field linearly whereas in the second case an arbitrary potential plays the role of a variable cosmological term. We see that the former configuration leads to a massless scalar field whereas the latter leads to a massive scalar field. General solutions of these linearized field equations for both cases are obtained corresponding to a static point mass. Geodesics of these solutions are also presented and solar system effects such as the advance of the perihelion, deflection of light rays and gravitational redshift were discussed. In general relativity cosmological constant has no role on these phenomena. We see that for the Brans-Dicke theory the cosmological constant has also no effect on these phenomena. This is because solar system observations require very large values of the Brans-Dicke parameter and the correction terms to these phenomena becomes identical to GR for these large values of this parameter. This result is also observed for the theory with arbitrary potential if the mass of the scalar field is very light. For a very heavy scalar field, however, there is no such limit on the value of this parameter and there are ranges of this parameter where these contributions may become relevant in these scales. Galactic and intergalactic dynamics is also discussed for these theories at the latter part of the paper with similar conclusions.Comment: 25 pages, Revtex. V2: two new sections discussing galactic and intergalactic phenomena are added, discussion is extended, references added, Published version

Brans-Dicke-Maxwell Solutions for Higher Dimensional Static Cylindrical Symmetric Spacetime

In this paper, Brans-Dicke-Maxwell type vacuum solutions are considered for a static cylindrically symmetric spacetime in arbitrary dimensions. Exact solutions are obtained by directly solving the field equations for the case where an azimuthal magnetic field is present. Other configurations such as axial magnetic field case can be obtained by suitably relabeling the coordinates. We have also considered conformally related "Einstein frame" to relate the solutions we have obtained with the dilaton-Maxwell type solutions that exist in the literature. We see that for a special case the general solution we present reduces to Dilaton-Melvin spacetime. The General Relativistic limit of these solutions are also discussed and we found that this limit is different from the four dimensional case.Comment: 9 Pages, articl

Antropoloji Penceresinden Hukuk : Basit Toplumlarda Akrabalık İktidar ve Çıkar İlişkileri

Antropoloji çalışmaları, insan topluluklarının tamamına yakınının çatışma ve ihtilaf içinde yaşadıklarını göstermektedir. Tüm toplumlarda gözlemlenmesi nedeniyle bazı yazarlar olgunun insan kültürü için en az cinsiyet kadar temel bir unsur olduğu iddiasını dile getirmiştir. Bizler ihtilaf ve çatışmanın olmadığı hiçbir toplumu bilmiyoruz. Çünkü kültürel örüntüler aracılığıyla işleyen kontrol şekilleri dışında toplumsal ahlaka ya da yasalara itaati temin edecek herhangi bir içgüdü yoktur. Hukuk, evrensel niteliğe sahip bu olgunun yok edilemeyeceği gerçeği üzerine inşa edilmiştir. İnsan toplulukları çatışmalardan arınmanın imkansız olduğu gerçeğiyle yüz yüze kaldığında çatışmaları denetim altına alma ve yönlendirme yolunu seçer