Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 0706.3212

Linear Stability of Closed Timelike Geodesics

Valéria M. Rosa·Patricio S. Letelier
View original source ↗Read source document ↗Export metadata ↓

Abstract

The linear stability of closed timelike geodesics (CTGs) is analyzed in two spacetimes with cylindrical sources, an infinite rotating dust cylinder, and a cylindrical cloud of static cosmic strings with a central spinning string. We also study the existence and linear stability of closed timelike curves in spacetimes that share some common features with the Gödel universe (Gödel-type spacetimes). In this case the existence of CTGs depends on the `background' metric. The CTGs in a subclass of inhomogeneous stationary cosmological solutions of the Einstein-Maxwell equations with topology $ S^3\times \mathbb R$ are also examined.

Explore related subjects

gr-qc

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Valéria M. Rosa, Patricio S. Letelier. 2011-01-25. Linear Stability of Closed Timelike Geodesics. https://arxiv.org/abs/0706.3212

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Scalar Backreaction from Gravitational Waves in a Degenerate $f(R,G)$ Sector

We investigate the high-frequency backreaction of gravitational waves in the Hessian-degenerate sector of four-dimensional $f(R,G)$ gravity defined by $f(R,G)=F(R+G/M^2)$. The degeneracy of the Hessian reduces the Legendre representation to a single scalar degree of freedom and maps the theory into a scalar--Gauss--Bonnet subclass of Horndeski gravity. We derive the tensor quadratic action and obtain the modified kinetic and gradient coefficients $Q_T=ϕ+4H\dotϕ/M^2$ and $F_T=ϕ+4\ddotϕ/M^2$ in units where the overall factor $\mpl^2$ is extracted. We then use the general Horndeski scalar--tensor--tensor cubic action to identify the induced scalar channel generated by a stochastic transverse-traceless gravitational-wave background. The scalar source is generically nonzero and, importantly, it is not determined solely by the tensor-speed deviation: it can remain nonzero even on a rolling de Sitter background for which $c_T^2=1$. For an exact analytic rolling de Sitter solution, we find $c_T^2=c_S^2=1$ and obtain a nonzero leading scalar source, $\mathcal S_{\mathcal R}^{\rm GW}=\langle\dot h_{ij}\dot h_{ij}\rangle/8+O(H/ω)$. The finite-wavenumber scalar response scales as $\mathcal R_{\bf k}^{(2)}\sim\mathcal S_{\mathcal R,\bf k}^{\rm GW}/ω_S^2$ in the geometric-optics regime. We do not identify this finite-$k$ response with a universal homogeneous Hubble shift; such a conversion requires an explicit zero-mode projection and averaging prescription. We emphasize that the result does not constitute a proof of global ghost freedom or a complete nonlinear treatment of the theory.

gr-qc↗
arXiv2026

When do quantum systems source gravity and how can we test it?

We argue that semiclassical gravity can be made consistent if quantum systems source gravity only when they participate in non-gravitational interactions that can lead to environment-induced decoherence, and which select conditional states that lead them to source such a field. If they do not participate in those interactions, systems do not contribute their stress-energy to the semiclassical equations, where regions lacking a gravitational field may remain flat. This proposal of conditional gravity is testable by probing the gravitational field sourced by systems, which should depend entirely on environment-induced decoherence in this context; by gravity not mediating entanglement in the Bose-Marletto-Vedral (BMV) experiment; and by how the reversibility of the initial state in this experiment would depend solely on this decoherence, distinguishing it from competing approaches. Our approach involves different theories. A distinct one involves chains of causally ordered interactions between quantum matter fields, which may show how gravity arises from QFT, and provide benefits to other areas of physics. To distinguish between the different theories that our approach allows for, and possibly test them, we present a generalization of the process operator and quantum causal models, which is applicable to quantum measurements in QFT implemented via the Fewster-Verch framework. However, we will also propose another approach. These different theories can be seen as arising from different ways quantum operations are classically controlled, since outcomes obtained along this chain determine which quantum operations are implemented next. We propose an experiment to test them using quantum circuits, which may allow us to probe how precisely gravity arises from quantum systems. We thus propose another application of quantum computers, which is to control the sourcing of gravity by quantum systems.

gr-qc↗
arXiv2026

Testing the wormhole echo hypothesis for GW231123

The short-duration gravitational-wave (GW) event GW231123 has component masses inferred to lie in the pair-instability mass gap and exhibits a burst-like morphology without a clear inspiral phase, making it an interesting target for testing alternatives to the standard binary black hole (BBH) interpretation. Motivated by its phenomenological similarity to GW190521, we test a wormhole-echo interpretation by modeling a leading echo pulse with a phenomenological \texttt{sine-Gaussian} wavepacket. Bayesian model comparison against a BBH interpretation described by the \texttt{IMRPhenomXPHM-SpinTaylor} waveform yields $\ln \mathcal{B}^{\rm Echo}_{\rm BBH}=1.87$. This preference is sensitive to the BBH waveform family and Echo-prior choices, and the observed statistic is not unusual within the targeted BBH-null ensembles. The positive Bayes factor therefore does not provide robust evidence for a wormhole-echo interpretation, with the analyses considered here supporting the standard BBH interpretation of GW231123.

gr-qc↗