Smooth window functions are often applied to strain data when inferring the parameters describing the astrophysical sources of gravitational-wave transients. Within the LIGO-Virgo-KAGRA collaboration, it is conventional to include a term to account for power loss due to this window in the likelihood function. We show that the inclusion of this factor leads to biased inference. The simplest solution

We present a new class of warp bubble geometries that are both interior-flat and segmented into Gaussian cylinders (interchangeably called ‘nacelles’1throughout the paper), providing an alternative to the continuous toroidal energy distribution of the Alcubierre model. Using the ADM 3+1 formalism, we derive the extrinsic curvature, York time, momentum densities, and energy density for both the Alcubierre

Motivated by a geometric understanding of the angular velocity of a Kerr black hole in terms of a quasi-conformal map that describes a 2d Beltrami fluid flow, a new way to construct initial data sets for binary rotating black holes by prescribing the angular velocities of the two black holes at their horizons is discussed. A set of elliptic equations with prescribed Dirichlet boundary conditions at

We present results for the numerical evaluation of scalar quasinormal modes in Taub-NUT-AdS4 spacetimes. To achieve this we consider angular modes that correspond to non-unitary highest weight SU(2) representations since global regularity is not consistent with the presence of complex quasinormal modes. We show that for any non-zero value of the NUT charge n there exists a region in the complex plane

We investigate the quasinormal modes (QNMs) of static and spherically symmetric black holes (BHs) in vacuum within the framework of f(ℚ)=ℚ+αℚ2 gravity, and compare them with those in f(T)=T+αT2 gravity. Based on the symmetric teleparallel equivalent of general relativity, we notice that the gravitational effects arise from non-metricity (the covariant derivative of metrics) in f(ℚ) gravity rather

We extend the usual vacuum Metric-Affine f(R) gravity by supplementing it with all parity even quadratic invariants in torsion and non-metricity. As we show explicitly this supplementation drastically changes the status of the theory which now propagates an additional scalar degree of freedom on top of the graviton. This scalar degree of freedom has a geometric origin as it relates to spacetime torsion

The local primordial density fluctuations caused by quantum vacuum fluctuations during inflation grow into stars and galaxies in the late Universe and, if they are large enough, also produce primordial black holes (BHs). We study the formation of the primordial BHs in k-essence inflation models with a potential characterized by an inflection point. The background and perturbation equations are integrated

We study null hypersurfaces approaching null infinity in asymptotically flat spacetimes within the Bondi–Sachs gauge. The null Raychaudhuri constraint is shown to asymptote to the Bondi mass-loss formula, interpreted as a stress tensor conservation law. This stress tensor, the null Brown–York tensor, yields a Carrollian stress tensor at null infinity from the bulk. Furthermore, we establish that the

Yes and maybe. In contrast to the fluid particles of this perfect fluid spacetime which follow non-geodesic world-lines and escape to infinity, we prove that freely-falling test particles of McVittie spacetime can reach the black hole horizon in finite proper time. We review the relevant evidence and argue that the fate of an extended test body is less clear. More precisely: we consider expanding McVittie

In the absence of gravity, Coleman’s theorem states that the O(4)-symmetric instanton solution, which is regular at the origin and exponentially decays at infinity, gives the lowest action. Perturbatively, this implies that any small deformation from O(4)-symmetry gives a larger action. In this letter we investigate the possibility of extending this theorem to the situation where the O(4)-symmetric

In this work, some properties of spherically symmetric charged black holes in Bumblebee gravity are studied and analyzed. The evolution of massive and massless scalar fields around these black holes indicates their stability for σ > 0. We identify two distinct behaviors in the late-time decay: massive fields exhibit an oscillatory polynomial tail, while massless fields present a purely polynomial tail

Torsion pendulums have vital applications in gravitational experiments. Seismic cross-coupling is one of the important noises, which can be suppressed by the eddy current damper, but this technology is still inadequate for torsion pendulums suspended by high-Q fused silica fiber. In this paper, we analyze the seismic cross-coupling for different-shaped torsion pendulums with eddy current dampers. The

Due to the processing accuracy of the test mass (TM) in gravitational reference sensors, the electrostatic force in the non-sensitive direction of the TM will produce a cross-coupling effect in the sensitive direction. This paper quantifies the impact of TM geometric imperfections (parallelism and perpendicularity) on electrostatic cross-coupling noise. The electrostatic coupling effects are examined

In the context of the general effort to model black hole (BH) dynamics, and in particular their return-to-equilibrium through quasi-normal modes (QNMs), it is crucial to understand how much test-field perturbations deviate from physical perturbations in modified gravity scenarios. On the one hand, physical perturbations follow the modified Einstein equations of the considered extension of general relativity

We present exact solutions describing a fake Schwarzschild black hole that cannot be distinguished from the Schwarzschild black hole by observations. They are constructed by attaching a spherically symmetric dynamical interior solution with a matter field to the Schwarzschild exterior solution at the event horizon without a lightlike thin shell. The dynamical region inside a Killing horizon of a static

In this work, we revisit/reinterpret/extend the model-independent analysis method (which we now call spread—luminosity distance fitting) from our previous work. We apply it to the updated supernova type Ia catalog, Pantheon+ and recent gamma ray bursts compilations. The procedure allows us, using only Friedmann-Lemaitre-Robertson-Walker (FLRW) assumption, to construct good approximations for expansion

The Laser Interferometer Space Antenna (LISA) will be a space-borne gravitational wave observatory that consists of three spacecraft, separated by several million kilometers, which tracks the separation between inertial test masses via laser interferometry. In this architecture strict requirements exist on the design of the orbits, the ability to accommodate laser frequency noise, the ability to provide

We study anisotropic Bianchi-I cosmology, incorporating quantum gravitational corrections into the Einstein equation through the scale-dependent Newton coupling and cosmological term, as determined by the flow equation of the effective action for gravity. For the classical cosmological constant Λ0 = 0, we derive the quantum mechanically corrected, or quantum-improved power-series solution for a general

We discuss and formalize topological means by which the initial singularity might be mollified, at the level of the spacetime manifold’s structure, in classical cosmological models of a homogeneous expanding Universe. One construction, dubbed a ‘reflective’ topological big bang, generalizes Schrödinger’s elliptic de Sitter space and is built to be compatible with the standard Friedmann–Lemaitre–Robertson–Walker

We consider Lorentzian general relativity in a cavity with a timelike boundary, with conformal boundary conditions and also a generalization of these boundary conditions. We focus on the linearized gravitational dynamics about the static empty cavity whose boundary has spherical spatial geometry. It has been recently shown that there exist dynamical instabilities, whose angular dependence is given

Next-generation gravitational-wave detectors are expected to constrain the properties of extreme density matter via observations of static and dynamical tides in binary neutron star inspirals. The required modelling is straightforward in Newtonian gravity—where the tide can be represented in terms of a sum involving the star’s oscillation modes—but not yet fully developed in general relativity—where

Due to its low mechanical loss and high refractive index, amorphous silicon is a very promising material to realize highly-reflective coatings with low thermal-noise, such as required for gravitational-wave detection. However, the optical absorption of amorphous silicon is too high, leading to heating of cryogenically cooled mirrors. Previous work on reducing the optical absorption has indicated correlations

The accelerated expansion of the Universe poses a significant challenge to General Relativity. Non-local modifications to gravity have emerged as a compelling class of theories to address this dark energy puzzle. Building upon earlier proposals (Deser and Woodard 2007 Phys. Rev. Lett. 99 111301; Deser and Woodard 2013 J. Cosmol. Astropart. Phys. 11 036; Dodelson and Park 2014 Phys. Rev. D 90 043535;

DECIGO (DECi-hertz Interferometer Gravitational Wave Observatory) is a space-based gravitational wave antenna concept targeting the 0.1–10 Hz band. It consists of three spacecraft arranged in an equilateral triangle with 1000 km sides, forming Fabry–Pérot cavities between them. A precursor mission, B-DECIGO, is also planned, featuring a smaller 100 km triangle. Operating these cavities requires ultra-precise

It has recently been shown that one can derive consistent thermodynamical expressions in the Lorentzian Taub–NUT spacetime keeping the Misner-string singularities and taking into account their contributions in the Komar integrals. We show how the same results are obtained when the Misner-string singularities are removed by using Misner’s procedure because, even though the complete spacetime has no

Landau’s criterion for superfluidity is a special case of a broader principle: A moving fluid cannot be stopped by frictional forces if its state of motion is a local minimum of the grand potential. We employ this general thermodynamic criterion to derive a set of inequalities that any superfluid mixture (with an arbitrary number of order parameters) must satisfy for a certain state of motion to be

Releasing the test mass (TM) is a critical phase of inertial sensors for gravitational wave detection. The grabbing positioning and release mechanism inevitably generates large initial momentum making TM capture control particularly challenging. To maximize the controllable range, this paper presents a time-division control strategy for the TM release phase. Simulation results show that the proposed

A ray model has been developed to characterize how a new, redundant fiber optic harness (FOH) design affects the UV light propagation in the Laser Interferometer Space Antenna (LISA) charge management system. LISA will be the first gravitational wave (GW) observatory in space, detecting GWs in the 0.1 mHz–1 Hz range. The endpoint of each LISA interferometer arm is a free-falling test mass (TM), which

In quantum mechanics, the time evolution of particles is given by the Schrödinger equation. It is valid in a nonrelativistic regime where the interactions with the particle can be modelled by a potential and quantised fields are not required. This has been verified in countless experiments when the interaction is of electromagnetic origin, but also corrections due to the quantised field are readily

In early 2024, European Space Agency formally adopted the Laser Interferometer Space Antenna (LISA) space mission with the aim of measuring gravitational waves emitted in the millihertz range. The constellation employs three spacecraft (SC) that exchange laser beams to form interferometric measurements over a distance of 2.5 million km. The measurements will then be telemetered down to Earth at a lower

Twistless-torsional Newton–Cartan (TTNC) geometry exists in two variants, type I and type II, which differ by their gauge transformations. In TTNC geometry there exists a specific locally Galilei-invariant function, called by different names in existing literature, that we dub the ‘locally Galilei-invariant potential’. We show that in both types of TTNC geometry, there always exists a local gauge transformation

This paper investigates the geometric consequences of equality in area-charge inequalities for spherical minimal surfaces and, more generally, for marginally outer trapped surfaces, within the framework of the Einstein–Maxwell equations. We show that, under appropriate energy and curvature conditions, saturation of the inequality A⩾4π(QE2+QM2) imposes a rigid geometric structure in a neighborhood

The discovery of the accelerated expansion of the Universe highlighted General Relativity’s inability to naturally account for dark energy without invoking a finely tuned cosmological constant. In response, a wide range of alternative paradigms have been proposed. Among these, Teleparallel Gravity (TG) and Symmetric TG, which depart from the Riemannian framework of General Relativity and instead rely

We present a covariant scalar-field framework that unifies the space-time singularity regularization with dynamical dark energy. The theory extends general relativity by introducing a scalar field Φ whose potential couples to the Lorentz-invariant quantity X≡uαuβTmatterαβ, ensuring manifest covariance. The resulting density-responsive scalar energy ρΦ exhibits dual behavior: (i) in high-density regimes

We present RoMOND (Rotating Modified Newtonian Dynamics), a relativistic extension of MOND constructed on a stationary, axisymmetric spacetime with a non-vanishing frame-dragging term. The framework introduces a scalar and a unit-timelike vector field, coupled through a disformal relation, and reduces to GR in the Newtonian limit while reproducing MOND phenomenology at low accelerations. The MOND acceleration

We study the scattering behavior of scalar and spinor fields in the background of a gravitating cosmic string spacetime. The model explored here for the background vortex is non-abelian, becoming abelian in an appropriate limiting case. We adopted the formalism we developed in Silva and Mohammadi (2021 Class. Quantum Grav. 38 205006), modifying the standard partial wave approach. We apply the method

While homogeneous cosmologies have long been studied in the group field theory (GFT) approach to quantum gravity, including a quantum description of cosmological perturbations is highly non-trivial. Here we apply a recent proposal for reconstructing an effective spacetime metric in GFT to the case of a metric with small inhomogeneities over a homogeneous background. We detail the procedure and give

One of the limiting noise sources of ground-based gravitational wave detectors at frequencies below 30 Hz is control-induced displacement noise. Compact laser interferometric sensors are a prime candidate for improved local displacement sensing. In this paper we present the design of an experiment that aims to demonstrate the advantages of interferometric sensors over shadow sensors. We mount two such

In this work, we put forward an analysis of the theoretical framework and indicate applications of symmetric Yang–Mills fields to cosmology. We analyse the coset-space dimensional reduction scheme to construct pure Yang–Mills fields on spacetimes given as cylinders over cosets. Particular cases of foliations using Hn, dSn and AdSn slices as non-compact symmetric spaces are solved, compared to previous

A regular black hole (BH), unconstrained by the weak cosmic censorship conjecture, can exceed its critical spin limit and transition into a superspinar. In this paper, we investigate the observational appearance of a rotating regular BH, specifically the Ghosh BH and its superspinar counterpart, when surrounded by a thin accretion disk. The resulting images reveal distinct features: the BH closely

In space exploration missions, mechanisms often contain essential systems that perform critical operations, requiring ground testing of their functionality and performance prior to mission launch. The TianQin space-based gravitational wave detection mission will deploy three satellites forming an equilateral triangle, with the primary payload consisting of high-precision inertial sensors and free-floating

We investigate the emergence of quantum coherence and quantum correlations in a two-particle system with deformed symmetries arising from the quantum nature of spacetime. We demonstrate that the deformation of energy-momentum composition induces a momentum-dependent interaction that counteracts the decoherence effects described by the Lindblad equation in quantum spacetime. This interplay leads to

Utilizing the covariant formulation of Penrose’s plane wave limit by Blau et al, we construct for any semi-Riemannian metric g a family of ‘plane wave limits.’ These limits are taken along any geodesic of g, yield simpler metrics of Lorentzian signature, and are isometric invariants. We show that they generalize Penrose’s limit to the semi-Riemannian regime and, in certain cases, encode g’s tensorial

One striking feature of binary black hole (BBH) mergers observed in the first decade of gravitational-wave astronomy is an excess of events with component masses around 35M⊙. Multiple formation channels have been proposed to explain this excess. To distinguish among these channels, it is essential to examine their predicted population-level distributions across additional parameters. In this work

We combine the well-known Beltrami–Klein model of non-Euclidean geometry on a two-dimensional disk, where the geodesics are the chords of the disk, with the two—dimensional de Sitter space. The geometry of the de Sitter space is defined on the complement of the Beltrami–Klein disk in the plane, with the de Sitter metric being the unique Lorentzian Einstein metric whose light cones form cones tangent

We propose a minimal, fully thermal mechanism that resolves the long-standing tension between achieving the observed dark-matter relic abundance and explaining the astrophysical signatures of self-interactions. The framework introduces two mediators: a light scalar φ (MeV scale) that yields the required, velocity-dependent self-interactions, and a heavy scalar resonance Φh (TeV scale) with mass mΦh≈2mχ

Gravitational optical properties are here investigated under the hypothesis of spherically-symmetric spacetimes behaving as media. To do so, we first consider two different definitions of the refractive index, n, of a spacetime medium and show how to pass from one definition to another by means of a coordinate transformation. Accordingly, the corresponding physical role of n is discussed by virtue

The existence of black holes in the Universe is nowadays established on the grounds of a blench of astrophysical observations, most notably those of gravitational waves from binary mergers and the imaging of supermassive objects at the heart of M87 and Milky Way galaxies. However, this success of Einstein’s general relativity (GR) to connect theory of black holes with observations is also the source

We investigate the generation rate of the quantum entanglement in a system composed of multiple massive particles with large spin, where the mass of a single particle can be split into multiple trajectories by a generalized Stern–Gerlach interferometer. Taking the coherent spin states as the initial state and considering the gravitational interaction due to Newtonian potential, we compute the generation

We investigate the gravitational Poissonian spontaneous localization (GPSL) model, a hybrid classical-quantum model in which classical Newtonian gravity emerges from stochastic collapses of the mass density operator, and consistently couples to quantum matter. Unlike models based on continuous weak measurement schemes, we show that GPSL ensures vacuum stability; this, together with its applicability

The field of gravitational wave (GW) detection is progressing rapidly, with several next-generation observatories on the horizon, including LISA. GW data is challenging to analyze due to highly variable signals shaped by source properties and the presence of complex noise. These factors emphasize the need for robust, advanced analysis tools. In this context, we have initiated the development of a low-latency

There has been much recent interest in the necessity of an observer degree of freedom in the description of local algebras in semiclassical gravity. In this work, we describe an example where the observer can be constructed intrinsically from the quantum fields. This construction involves the slow-roll inflation example recently analyzed by Chen and Penington, in which the gauge-invariant gravitational

Is gravity quantum mechanical? If so, we argue that nonlinear effects in black hole ringdowns—notably second harmonic generation—generates gravitational waves in non-classical states. While quantum features of these states such as sub-Poissonian statistics or entanglement could in principle be measured at interferometric detectors, the tiny coupling of gravity to matter makes this extremely challenging

Stray light represents a significant noise source for gravitational wave detectors, requiring an accurate modeling and mitigation to preserve the experiment’s sensitivity. In this article, we present an updated and improved analysis of the stray-light induced noise in the Einstein Telescope main arm. The results presented here supersede previous studies taking into account a number of improvements

In this work we establish a version of the Bartnik Splitting Conjecture in the context of Lorentzian length spaces. In precise terms, we show that under an appropriate timelike completeness condition, a globally hyperbolic Lorentzian length space of the form Σ×R with Σ compact splits as a metric Lorentzian product, provided it has non-negative timelike curvature bounds. This is achieved by showing

We apply the perturbation methods of the post-Newtonian approximation to obtain equations for gravitation derived from the Rastall Theory, a modification of the Einstein Field Equations. This method allows us to get the components of the space-time metric in terms of the generalized potentials. Once obtained, we use the results to construct equations of gravitation in vector form, analogous to the

In this study, we consider a beam summation method adapted from the semiclassical regime of quantum mechanics to study the classical properties of thin light bundles in gravity. In Newtonian paraxial optics, this method has been shown to encapsulate the wave properties of the light beams. In our case, the wave function assigned to the light bundle can be viewed as a coarse-grained description that

Various noise sources will impact the laser interferometer space antenna (LISA) interferometric measurements, particularly laser frequency noise, which will dominate by several orders of magnitude. To achieve the required sensitivity for gravitational wave detection, noise reduction methods, such as the time-delay interferometry (TDI) algorithm, must be employed and tested using both computer and instrumental

Accurate and reliable calibration of the Advanced LIGO detectors has enabled a plethora of gravitational-wave discoveries in the detectors’ first decade of operation, starting with the ground-breaking discovery, GW150914. In the first decade of operation, the calibrated strain data from Advanced LIGO detectors has become available at a lower latency and with more reliability. In this paper, we discuss

This work focuses on the emergence of dark phases (dark energy-induced phases) in the radial wave function of scalar particles. We achieve this by presenting novel solutions to the Klein–Gordon equation in a spherically symmetric spacetime, which encompasses a black hole, a quintessential fluid, and a cloud of strings. We determine the exact solution for the spacetime metric, analyze the admissible