Nihat Sadik Deger

Nihat Sadik Deger
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Nihat Sadik Deger
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High Energy Physics - Theory (16)
 
General Relativity and Quantum Cosmology (6)

Publications Authored By Nihat Sadik Deger

In this paper we systematically construct simply transitive homogeneous spacetime solutions of the three-dimensional Minimal Massive Gravity (MMG) model. In addition to those that have analogs in Topologically Massive Gravity, such as warped AdS and pp-waves, there are several solutions genuine to MMG. Among them, there is a stationary Lifshitz metric with the dynamical exponent z=-1 and an anisotropic Lifshitz solution where all coordinates scale differently. Read More

We construct time and radial dependent solutions that describe p-branes in chargeless S-brane backgrounds. In particular, there are some new M5- and D3-branes among our solutions which have AdS limits and contain a cosmological singularity as well. We also find a time-dependent version of the dyonic membrane configuration in 11-dimensions by applying a Lunin-Maldacena deformation to our new M5-brane solution. Read More

We first make a Killing spinor analysis for a general three-dimensional off-shell $N=(2,0)$ supergravity and find conditions for a bosonic background to preserve some supersymmetry . We then consider a particular model, namely $N=(2,0)$ topologically massive supergravity and impose its field equations. By making a suitable ansatz on metric functions we find a large class of solutions that include spacelike, timelike and null warped $AdS_3$ among others. Read More

We construct Kundt solutions of Minimal Massive Gravity theory and show that, similar to Topologically Massive Gravity (TMG), most of them are constant scalar invariant (CSI) spacetimes, that correspond to deformations of round and warped (A)dS. We also find an explicit non-CSI Kundt solution at the merger point. Finally, we give their algebraic classification with respect to the traceless Ricci tensor (Segre classification) and show that their Segre-types match with the types of their counterparts in TMG. Read More

We first classify all supersymmetric solutions of the 3-dimensional half-maximal ungauged supergravity that possess a timelike Killing vector coming from the Killing spinor bilinear by considering their identification under the complexification of the local symmetry of the theory. It is found that only solutions that preserve $16/2^n, 1 \leq n \leq 3$ real supersymmetries are allowed. We then classify supersymmetric solutions under the real local symmetry of the theory and we are able to solve the equations of motion for all of them. Read More

We construct intersections of S-branes with waves and Kaluza-Klein monopoles. There are several possible ways to add a monopole to an S-brane solution similar to p-branes. On the other hand, one may add a wave only to the transverse space of an S-brane unlike a p-brane where wave resides on its worldvolume. Read More

We present the embedding of three-dimensional SO(4)$\ltimes\mathbb{R}^6$ gauged $N=4$ supergravity with quaternionic target space SO(4,4)$/$(SO(4)$\times$SO(4)) into $D=6$, $N=(1,0)$ supergravity coupled to a single chiral tensor multiplet through a consistent reduction on AdS$_3\times S^3$. Read More

We determine the most general form of off-shell N=(1,1) supergravity field configurations in three dimensions by requiring that at least one off-shell Killing spinor exists. We then impose the field equations of the topologically massive off-shell supergravity and find a class of solutions whose properties crucially depend on the norm of the auxiliary vector field. These are spacelike-squashed and timelike-stretched AdS_3 for the spacelike and timelike norms, respectively. Read More

We study Lunin-Maldacena deformations of cosmological backgrounds of D=11 supergravity which gives an easy way to generate solutions with nonzero 4-form flux starting from solutions of pure Einstein equations which possess at least three U(1) isometries. We illustrate this on the vacuum S-brane solution from which the usual SM2-brane solution is obtained. Applying the method again, one either gets the recently found S-brane system where contribution of the Chern-Simons term to field equations is non-zero or the SM2-SM2(0) intersection, depending on which U(1) directions are used during the process. Read More

We initiate a systematic study of the solutions of three-dimensional matter-coupled half-maximal (N=8) supergravities which admit a Killing spinor. To this end we analyze in detail the invariant tensors built from spinor bilinears, a technique originally developed and applied in higher dimensions. This reveals an intriguing interplay with the scalar target space geometry SO(8,n)/(SO(8) x SO(n)). Read More

We construct new M-theory solutions starting from those that contain 5 U(1) isometries. We do this by reducing along one of the 5-torus directions, then T-dualizing via the action of an O(4,4) matrix and lifting back to 11-dimensions. The particular T-duality transformation is a sequence of O(2,2) transformations embedded in O(4,4), where the action of each O(2,2) gives a Lunin-Maldacena deformation in 10-dimensions. Read More

We construct an intersecting S-brane solution of 11-dimensional supergravity for which the contribution of the Chern-Simons term to the field equations is non-zero. After studying some of its properties, we consider three different compactifications (each with 3 separate subcases) of this system to 4-dimensions. Two of these give accelerating cosmologies, however their expansion factors are of order unity. Read More

We first investigate intersections of an S-brane with a single p-brane and show that in addition to the already known solutions, it is possible to place the S-brane so that the radial part of the p-brane is not included in its worldvolume. This leads to a new set of solutions. Secondly, we consider intersections of an S-brane with a supersymmetric Dp_1-Dp_2 intersection and find the list of allowed solutions for both positions of the S-brane. Read More

We construct new 1/2 supersymmetric solutions in D=3, N=2, matter coupled, U(1) gauged supergravities and study some of their properties. We do this by employing a quite general supersymmetry breaking condition, from which we also redrive some of the already known solutions. Among the new solutions, we have an explicit non-topological soliton for the non-compact sigma model, a locally flat solution for the compact sigma model and a string-like solution for both types of sigma models. Read More

We construct new intersecting S-brane solutions in 11-dimensional supergravity which do not have supersymmetric analogs. They are obtained by letting brane charges to be proportional to each other. Solutions fall into two categories with respect to whether there is a non-diagonal term to be cancelled in the field equations or not. Read More

We study holographic RG flows of N=2 matter couple AdS_3 supergravities which admit both compact and non-compact sigma manifolds. For the compact case the supersymmetric domain wall solution interpolates between a conformal IR region and flat spacetime and this corresponds to a deformation of the CFT by an irrelevant operator. When it is non-compact, the solution can be interpreted as a flow between an UV fixed point and a non-conformal(singular) IR region. Read More