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Özgür Sarıoğlu

Publications and source records attributed to Özgür Sarıoğlu.

17 recordsLinked to original sources
arXiv2026

Chern-Simons-like formulation of 3D MMG-like massive gravity models

We investigate the Chern-Simons-like formulation of 3D MMG-like massive gravity models that are "third-way consistent". Building on previous work on exotic massive gravities, we analyze a class of MMG-like theories characterized by a specific parity structure and an auxiliary field hierarchy. Focusing on the simplest non-trivial case, we solve the full set of field equations, determine the AdS background solutions, compute the central charges of the dual CFT, and perform a linearized analysis to obtain the mass spectrum. Along the chiral line, the linearized mass operator develops a rank-2 Jordan block, signaling logarithmic behavior of massive modes in the dual two-dimensional CFT. At a special degenerate point, this structure is enhanced to a rank-3 Jordan block, giving rise to two logarithmic partners and an ultra-logarithmic sector in the boundary theory.

hep-th↗
arXiv2025

Chern-Simons potentials of higher-dimensional Pontryagin densities

We develop a novel and systematic approach to computing the $(2n-1)$-form Chern-Simons potential given the Pontryagin density, i.e. the $n^{\text{th}}$ Chern character, in arbitrary even dimensions $D=2 n \geq 2$. Throughout we work with a generic affine connection, that results in a non-vanishing torsion in general, and allows for non-metricity, which accommodates the existence of non-trivial Chern characters and hence Pontryagin densities. We outline an algorithm, with its implementation as a code, which lets one to determine the Chern-Simons potential given the Pontryagin density in an arbitrary even dimension.

math-ph↗
arXiv2024

On the maximally symmetric vacua of generic Lovelock gravities

We survey elementary features of Lovelock gravity and its maximally symmetric vacuum solutions. The latter is solely determined by the real roots of a dimension-dependent polynomial. We also recover the static spherically symmetric (black hole) solutions of Lovelock gravity using Palais' symmetric criticality principle. We show how to linearize the generic field equations of Lovelock models about a given maximally symmetric vacuum, which turns out to factorize into the product of yet another dimension-dependent polynomial and the linearized Einstein tensor about the relevant background. We also describe how to compute conserved charges using linearized field equations along with the relevant background Killing isometries. We further describe and discuss the special vacua which are defined by the simultaneous vanishing of the aforementioned polynomials.

gr-qc↗
arXiv2024

Chern-Simons-Like Formulation of Exotic Massive 3D Gravity Models

We investigate the Chern-Simons-like formulation of exotic general massive gravity models within the framework of third-way to three-dimensional gravity. We classify our construction into two main approaches: one using torsional cosmological Einstein and exotic massive gravity equations, and the other a torsion-free approach. The former approach, while mathematically appealing, precludes the construction of critical exotic models where the central charges vanish. In contrast, the latter approach has a wider parameter space and allows for the construction of critical models. An explicit example of an exotic general model is provided to illustrate both methods. Our methodology represents the first step towards establishing the most general Chern-Simons-like formulation of third-way to three-dimensional gravity, which would enable the study of identifying its bulk/boundary unitary sector.

hep-th↗
arXiv2024

Rotating AdS$_3 \times$S$^3$ and Dyonic Strings from 3-Dimensions

We make a general Killing spinor analysis of a particular $D=3, \, N=4$ gauged supergravity that comes from a consistent S$^3$ reduction of $D=6, \, N=(1,0)$ supergravity coupled to a single chiral tensor multiplet. We then focus on its supersymmetric solutions with a null Killing vector and find three new ones. Two of these, namely the null warped AdS$_3$ (also known as the Schrödinger spacetime) and the charged domain wall solutions, admit non-trivial gauge fields which give rise to rotating solutions in 6-dimensions. The uplift of the first one produces an interesting AdS$_3 \times$S$^3$ background with a non-trivial rotation in the $U(1)$ fiber direction of the S$^3$ which retains the Schrödinger scale invariance that the seed solution has. The second one leads to the well-known rotating dyonic string solution. Finally, the uplift of the third one, which is a domain wall solution with no gauge fields, results in a distribution of dyonic strings.

hep-th↗
arXiv2023

Conserved charges of the Kerr black hole revisited

We revisit the Kerr black hole as cast in the Boyer-Lindquist, Kerr-Schild and Weyl canonical coordinates, and calculate its total mass/energy and total angular momentum by using linearized gravity along with its background Killing isometries. We argue that the integration of the relevant gravitational flux does not depend on the geometry of the closed and simply connected spatial boundary provided it is also piecewise smooth.

gr-qc↗
arXiv2023

Gravitational duality, Palatini variation and boundary terms: A synopsis

We consider $f(R)$ gravity and Born-Infeld-Einstein (BIE) gravity in formulations where the metric and connection are treated independently and integrate out the metric to find the corresponding models solely in terms of the connection, the archetypical treatment being that of Eddington-Schrödinger (ES) duality between cosmological Einstein and Eddington theories. For dimensions $D\ne2$, we find that this requires $f(R)$ to have a specific form which makes the model Weyl invariant, and that its Eddington reduction is then equivalent to that of BIE with certain parameters. For $D=2$ dimensions, where ES duality is not applicable, we find that both models are Weyl invariant and equivalent to a first order formulation of the bosonic string. We also discuss the form of the boundary terms needed for the variational principle to be well defined on manifolds with non-null boundaries. This requires a modification of the Gibbons-Hawking-York (GHY) boundary term for gravity. This modification also means that the dualities between metric and connection formulations are consistent and include the boundary terms.

gr-qc↗
arXiv2023

Geometry, conformal Killing-Yano tensors and conserved "currents"

In this paper we discuss the construction of conserved tensors (currents) involving conformal Killing-Yano tensors (CKYTs), generalising the corresponding constructions for Killing-Yano tensors (KYTs). As a useful preparation for this, but also of intrinsic interest, we derive identities relating CKYTs and geometric quantities. The behaviour of CKYTs under conformal transformations is also given, correcting formulae in the literature. We then use the identities derived to construct covariantly conserved ``currents''. We find several new CKYT currents and also include a known one by Penrose which shows that ``trivial'' currents are also useful. We further find that rank-$n$ currents based on rank-$n$ CKYTs $k$ must have a simple form in terms of $dk$. By construction, these currents are covariant under a general conformal rescaling of the metric. How currents lead to conserved charges is then illustrated using the Kerr-Newman and the C-metric in four dimensions. Separately, we study a rank-1 current, construct its charge and discuss its relation to the recently constructed Cotton current for the Kerr-Newman black hole.

gr-qc↗
arXiv2023

New currents with Killing-Yano tensors

New relations involving the Riemann, Ricci and Einstein tensors that have to hold for a given geometry to admit Killing-Yano tensors are described. These relations are then used to introduce novel conserved "currents" involving such Killing-Yano tensors. For a particular current based on the Einstein tensor, we discuss the issue of conserved charges and consider implications for matter coupled to gravity. The condition on the background geometry to allow asymptotic conserved charges for a current introduced by Kastor and Traschen is found and a number of other new aspects of this current are commented on. In particular we show that it vanishes for rank $(D-1)$ Killing-Yano tensors in $D$ dimensions.

hep-th↗
arXiv2023

Killing-Yano charges of asymptotically maximally symmetric black holes

We construct an asymptotic conserved charge for a current that has been defined using Killing-Yano tensors. We then calculate the corresponding conserved charges of of the Kerr and AdS-Kerr black holes, and their higher-dimensional generalizations, Myers-Perry and Gibbons-Lü-Page-Pope black holes. The new charges all turn out to be proportional to the angular momenta of their parent black holes.

gr-qc↗
arXiv2022

A comment on Metric vs Metric-Affine Gravity

We consider the sum of the Einstein-Hilbert action and a Pontryagin density (PD) in arbitrary even dimension $D$. All curvatures are functions of independent affine (torsionless) connections only. In arbitrary dimension, not only in $D=4n$, these first order PD terms are shown to be covariant divergences of "Chern-Simons" currents. The field equation for the connection leads to it being Levi-Civita, and to the metric and affine field equations being equivalent to the second order metric theory. This result is a counterexample to the theorem stating that purely metric and metric-affine models can only be equivalent for Lovelock theories.

gr-qc↗
arXiv2022

Killing-Yano Cotton Currents

We discuss conserved currents constructed from the Cotton tensor and (conformal) Killing-Yano tensors (KYTs). We consider the corresponding charges generally and then exemplify with the four-dimensional Plebański-Demiański metric where they are proportional to the sum of the squares of the electric and the magnetic charges. As part of the derivation, we also find the two conformal Killing-Yano tensors of the Plebański-Demiański metric in the recently introduced coordinates of Podolsky and Vratny. The construction of asymptotic charges for the Cotton current is elucidated and compared to the three-dimensional construction in Topologically Massive Gravity. For the three-dimensional case, we also give a conformal superspace multiplet that contains the Cotton current in the bosonic sector. In a mathematical section, we derive potentials for the currents, find identities for conformal KYTs and for KYTs in torsionful backgrounds.

hep-th↗
arXiv2022

Uses of Killing and Killing-Yano Tensors

In this contribution we have collected some facts about Killing and Killing-Yano tensors that we feel are of general interest for researchers working on problems that rely on differential geometry. We also include some of our recent studies pertaining to currents, charges and (super)invariants for particles and tensionless strings.

hep-th↗
arXiv2022

Tensionless Strings and Killing(-Yano) Tensors

We construct invariants for bosonic and spinning tensionless (null) strings in backgrounds that carry Killing tensors or Killing-Yano tensors of mixed type. This is facilitated by the close relation of these strings to point particles. We apply the construction to the Minkowski and to the Kerr-Newman backgrounds.

hep-th↗
arXiv2019

Consistent $S^3$ reductions of six-dimensional supergravity

We work out the consistent AdS$_3\times S^3$ truncations of the bosonic sectors of both the six-dimensional ${\cal N}=(1,1)$ and ${\cal N}=(2,0)$ supergravity theories. They result in inequivalent three-dimensional half-maximal ${\rm SO}(4)$ gauged supergravities describing 32 propagating bosonic degrees of freedom apart from the non-propagating supergravity multiplet. We present the full non-linear Kaluza-Klein reduction formulas and illustrate them by explicitly uplifting a number of AdS$_3$ vacua.

hep-th↗
arXiv2019

Circularly symmetric solutions of Minimal Massive Gravity at its merger point

I find all the static circularly symmetric solutions of Minimal Massive 3D Gravity at its merger point, construct stationary versions of these and discuss some of their geometric and physical properties. It turns out that apart from a static hairy black hole, there is also a static gravitational soliton, that has been overlooked in the literature.

gr-qc↗