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Primordial black hole (PBH) binaries in the stellar mass range may still contribute a fraction of the detectable compact object binaries by LIGO and future GW observatories. PBH binaries at formation typically have very high eccentricities. In this paper, we study the eccentricity of stellar mass range PBH binaries from all formation channels and account for all evolutionary pathways. We simulate large samples of PBH binaries, tracking their full orbital evolution up to their merger or to the present day. For those that merge, we compute their GW strain, detectability, and eccentricity distributions for LISA, DECIGO, ET, CE, and aLIGO. We find that PBH binaries that evolve in isolation completely circularize by the time their GWs enter any GW band except for LISA's, where residual eccentricities of order $O(10^{-2})$ can exist. Binaries that become part of dark matter halos can have multiple binary-single interactions with other PBHs, especially if they reside in the more dense environments among them and can have higher eccentricities even at their late inspiral phase, probed by the GW observatories. Considering the current limits on the abundance of stellar mass range PBHs, we predict that LISA and DECIGO together would be able to probe $O(10^2)$ such binaries with $e>0.01$. If these future GW observatories in space can exclude such eccentric binaries, then limits on the PBH abundance can be improved by an order of magnitude.

The discovery of the accelerated expansion of the cosmos has sparked great interest in studying the nature of the mysterious force behind this effect, often called dark energy. Several theories were proposed to study the nature of dark energy, and holographic dark energy stands out among them due to the relation between dark energy density and the principles of quantum gravity and holography. Recent progress made in fractional cosmology has led to the addition of fractional correction terms to the definition of holographic dark energy. Based on such progress, in this study, we investigate the behavior of fractional holographic dark energy in forming exotic spacetimes, especially traversable wormholes, which represent intriguing solutions of Einstein's field equations connecting distinct regions of spacetime. In the present article, a new class of Morris--Thorne wormhole solutions is obtained under the consideration of fractional holographic dark energy as the source of the gravitational field with a varying redshift function in the context of Einstein gravity. To study the nature of wormholes, their geometry, viability, and thermodynamic behavior, a shape function is obtained, and the wormholes are analyzed in detail via embedding diagrams, throat geometry, active gravitational mass, compactness, exoticity factor, energy conditions, conservation law, volume integral quantifier, Kretschmann invariant, and complexity factor. Moreover, thermodynamic properties of the wormholes are studied via the examination of several parameters, including Hawking temperature, wormhole temperature, entropy, energy, work density, and heat flux, aiming to understand the influence of fractional holographic corrections on the stability and evolution of traversable wormhole structures.

We present a directional dark matter search using the MIMAC (Micro-tpc Matrix of Chambers) detector at the Modane Underground Laboratory. Operating a low-pressure gas mixture of i-C4H10 and 50% CHF3 at 30 mbar, without any shielding, the detector allows the reconstruction of the 3D tracks of nuclear recoils produced in the 6-liter active volume. Directionality is a crucial tool to discriminate true WIMP signals from those of background producing identical recoils, such as neutrons. We analyze data from two independent chambers with effective exposures of 495.1 and 354.2 days, respectively. To estimate the background directly from the data, we apply a standard ON/OFF spatial analysis. By projecting the reconstructed tracks onto the galactic map and applying a moving kinematic energy cut depending on the WIMP mass, we compare the event rate in the signal direction with multiple OFF-source regions. Finding no significant excess of events in the direction of the Cygnus constellation, we set an upper limit on the spin-dependent WIMP-protoncross section.

DESI DR2 BAO combined with CMB and Type~Ia supernovae in the Chevallier--Polarski--Linder (CPL) parameterisation prefers evolving dark energy over $Λ$CDM at roughly $2.8$--$4.2σ$. We reconstruct the same late-time expansion history with a hierarchical Gaussian process (GP) that co-samples the kernel hyperparameters $(σ_f,l)$ together with $(H_0, Ω_m, Ω_k, ω_b h^2)$, coupling BAO, compressed Planck distance priors, and Pantheon+ through a Monte-Carlo effective likelihood conditioned on 37 cosmic-chronometer $H(z)$ points. The baseline posterior gives $w(z\simeq 0)=-0.80^{+0.26}_{-0.23}$ (68\%~C.L.), about $0.8σ$ from $w=-1$, with $l=3.79^{+0.81}_{-1.12}$. A CPL fit on the identical compressed Planck pipeline improves nested $Λ$CDM by only $Δχ^2\sim 1$ ($\sim 1σ$). Ablations that fix $(σ_f,l)$, drop SN or LRG1/2 BAO, replace the radial-basis kernel by Matérn-$5/2$, or tighten the prior on $l$ leave the median $w(0)$ within $\lesssim 1σ$ of $-1$. The mild preference reported here is therefore specific to this compressed-CMB analysis and does not address DESI's full Planck-likelihood result.

We investigate scalar-induced gravitational waves (SIGWs) in an inflationary model with symmetry breaking, in which charged scalar fields are coupled to an isotropic triplet of Abelian gauge fields through a kinetic function. Such SIGWs can be enhanced to a detectable level when the mixing between the inflaton and gauge-field perturbations is sufficiently large. We find that the longitudinal mode and the charge-dependent mixing between perturbations become relevant only when the gauge-field excitation occurs sufficiently late during inflation. In this regime, the corresponding SIGWs are shifted to ultra-high frequencies, typically can around the GHz band. We show that the parameters characterizing the effects of the longitudinal mode and charge-dependent mixing affect the signal in qualitatively different ways. This provides characteristic signatures for distinguishing the neutral case from the charged one through the frequency profile of the stochastic gravitational-wave background.

We use the non-linearly coupled Einstein-matter field equations to prove four theorems that bound from above the dimensionless force function ${\cal F}=4πr^2\cdot p(r)$ in spatially regular curved spacetimes of spherically symmetric self-gravitating matter configurations [here $p(r)$ is the radially-dependent pressure inside the spatially regular matter configurations]. In particular, for generic (not necessarily isotropic) matter configurations it is proved that: (i) ${\cal F}\leq 2$ for matter fields that satisfy the dominant energy condition, and (ii) ${\cal F}\leq 1$ for matter fields with a non-positive energy-momentum trace. In addition, for self-gravitating isotropic matter configurations we derive the stronger upper bounds: (iii) ${\cal F}\leq 1$ for matter fields that satisfy the dominant energy condition, and (iv) ${\cal F}\leq 1/2$ for matter fields with a non-positive energy-momentum trace. Our analytically derived results are in accord with the spirit of the maximum force conjecture in general relativity.

Magnetic fields in interplanetary coronal mass ejections (ICMEs) often display a flux rope structure at large scales and a turbulent cascade of fluctuations at smaller scales. However, the nature of fluctuations at transition scales between the flux rope and turbulence - i.e., at mesoscales - has not been previously examined in detail. Mesoscale fluctuations of the magnetic field in 142 ICME intervals with clear flux rope signatures at 1 au have been examined using wavelet power spectra, with "mesoscale" defined here as spacecraft-frame frequencies $10^{-4}\ \text{Hz}<f_\mathrm{sc}< 10^{-3}\ \text{Hz}$, equivalent to timescales $2.8\ \text{hr}\gtrsim τ\gtrsim 17\ \text{min}$. The spectra were found to be significantly less steep at mesoscales than at larger and smaller scales, with an average spectral slope close to $-1$ at these intermediate scales. The mesoscale fluctuations had relatively high cross helicity magnitudes and low compressibility, suggesting a significant degree of Alfvénicity, while also having more negative residual energy than the turbulent fluctuations found at smaller scales. Uncertainties in the spectral slope values at mesoscales were used to distinguish between spectra showing a relatively smooth power-law behavior or (less commonly) a more bumpy trend; the smoother power-law intervals had a balanced cross helicity distribution while the more bumpy spectra had a predominantly antisunward cross helicity. Slow wind intervals were similarly analyzed, and showed similar properties to the ICMEs. These results indicate that a spectrally narrow $1/f$ range is typically present in ICMEs at mesoscales.

The formation, extension, and morphology of extra-tidal stars around globular clusters depend on the internal kinematics of the host cluster and the Galactic potential. Tracing the kinematics of faint tidal tails sheds light on their formation and contribution to the Milky Way halo. NGC 7492 is an outer halo globular cluster with conflicting evidence regarding the presence of tidal tails. If present, the tails are expected to be faint and overlap on the sky with the Sagittarius stream, located at a similar heliocentric distance but with distinct kinematics. We carried out a GIRAFFE spectroscopic follow-up of ten fields covering the expected tidal tails of NGC 7492. Gaia parallaxes were used to remove foreground contaminants, while only loose proper-motion constraints were applied in the target selection. Radial velocities and metallicities were derived for more than 700 stars, from the red giant branch to the upper main sequence. Cluster and extra-tidal stars were identified from their proper motions, radial velocities, and metallicities. This population extends at least 1.8 deg from the cluster center, confirming the tidal tails previously detected only photometrically, with positions consistent with particle-spray models of the cluster disruption. The Sagittarius stream is clearly identified through its distinct proper motions, radial velocities, and more metal-rich population. Despite the low spatial density of the extra-tidal stars, their kinematic signature is clearly detected, demonstrating that the tidal tails overlap on the sky with the Sagittarius stream but are physically unrelated. This spectroscopic dataset provides a robust basis for future studies of the tails at larger angular extents and fainter magnitudes.

We investigate the equivalence of the Jordan and Einstein frames of the Brans--Dicke theory before and after relational deparametrization of the constrained Hamiltonian system. Although the two conformal formulations are equivalent at the covariant level and related by a canonical transformation on the standard ADM phase space, their equivalence after reduction with respect to an internal clock is nontrivial. Using the Brans--Dicke scalar as a relational clock, we show that the apparent discrepancy between the reduced Hamiltonians does not indicate a physical inequivalence of the two frames. Instead, it arises from a mismatch in the canonical embedding of the clock sector prior to reduction. While the scalar configuration variable is preserved under the conformal transformation, its conjugate momentum is shifted by a contribution involving the gravitational momentum trace. Consequently, relational dynamics are determined not by the clock variable $T$ alone, but by the complete canonical clock pair $(T,P_T)$. We construct a frame-adapted canonical chart in which the clock sector is consistently transformed prior to deparameterization. The resulting reduced Hamiltonian coincides with that of the Einstein frame, restoring the equivalence of the reduced relational dynamics. Our results identify the canonical clock sector as the fundamental structure governing relational evolution in Brans--Dicke theory and provide a general framework for understanding frame dependence in scalar--tensor gravity and reduced phase-space quantization.

We propose a novel approach for the timing of pulsars orbiting a supermassive black hole, which implements the fully relativistic calculations of the photon travel time into a robust timing model. We generate realistic mock catalogs of pulsar times of arrival for several putative pulsars on tight orbits around the Galactic Center supermassive black hole, Sagittarius A* (Sgr A*). Then, we perform a proof-of-concept sensitivity analysis to forecast the accuracy that future observational facilities, like the Square Kilometre Array, will achieve in the characterization of the parameters of our timing model. Our analysis shows how the observation of pulsars at the Galactic Center will open an incredibly promising avenue for the characterization of the physical properties of Sgr A*, which can improve by at least 3 orders of magnitude the current constraints on the black hole's mass achieved with S-stars and event-horizon scale observations.

In this paper we quantify the ability of the Laser Interferometer Space Antenna (LISA) to test the presence of non-tensorial polarizations as well as modifications to the tensor ones in gravitational waves emitted from massive black hole binaries. We employ the Parametrized Post-Einsteinian (PPE) formalism to model deviations from General Relativity (GR) for tensor, vector, and scalar polarizations. Our PPE parametrization is inspired by post-Newtonian waveforms from four modified gravity theories: Horndeski, Einstein-aether, Rosen's bimetric, and Lightman-Lee. We consistently implement these modifications during the inspiral, ensuring proper waveform alignment and tapering at merger. Subsequently, we perform Fisher forecasts to derive expected constraints on deviations from General Relativity and map these constraints to the parameter spaces of the four gravity theories. For tensor polarizations, LISA achieves constraints on amplitude modifications ranging between ~ 10<SUP>-4</SUP> - 10<SUP>-2</SUP> precision level, depending on the frequency evolution of the modifications, for systems with 10<SUP>5</SUP> - 10<SUP>7</SUP> M<SUB>⊙</SUB> at z = 1. We find that LISA can distinguish breathing and longitudinal scalar polarizations, a capability that current ground-based detectors do not possess, only for relatively light binaries with M ≲ 10<SUP>4</SUP> M<SUB>⊙</SUB>, beyond which these modes become degenerate in the detector response. Importantly, constraints on vector polarizations are approximately 2--3 times more precise than for scalar polarizations. For both vector and scalar modes, amplitude measurements reach precisions ranging between ~ 10<SUP>-8</SUP> - 10<SUP>-2</SUP>, depending on the frequency evolution of the modifications, for systems with 10<SUP>5</SUP> - 10<SUP>7</SUP> M<SUB>⊙</SUB> at z = 1. These results demonstrate LISA's potential to probe gravity in the emission process of gravitational waves.

An additional term of the form $λ\mathbf{T} \cdot \mathbf{C} \cdot \mathbf{T}$ in the Einstein-Hilbert Lagrangian was introduced to explain the interaction between matter and pure gravitational field [H. W. Lee and A. Qadir, Motion of test particle for Weyl-interaction gravity, {\it Int. Jour. Mod. Phys. D} {\bf 28}(16) (2019) 2040014], the modified relativistic dynamics (MORD). In this paper, we estimate the shadow parameters of black hole in a spherically symmetric static spacetime within the MORD framework. As a first approximation, we assume that the black hole is surrounded by a constant-density baryonic matter halo. The analysis is then extended by introducing a homogeneous plasma background. We compute the shadow radii for various black hole masses and analyze their dependence on the WIG coupling parameter $λ$. In addition, we compute the fundamental quasi-normal mode (QNM) frequencies under test-field approximation, and perform a time-domain integration analysis.

We investigate ghost dark energy (GDE) in a cosmological framework derived from Kaniadakis entropy. By applying the first law of thermodynamics to the FRW apparent horizon, we obtain modified Friedmann equations that include a correction term characterized by the Kaniadakis parameter $λ$. We then study the evolution of a flat universe containing pressureless matter and interacting GDE within this modified gravity setup. Our numerical analysis reveals that the Kaniadakis correction mildly affects the dark energy equation of state and shifts the transition to cosmic acceleration. Stability analysis via the squared sound speed shows the model remains generally unstable, though the instability is moderated for larger $λ$. Statefinder diagnostics indicate that the model approaches the $Λ$CDM fixed point in the future, with deviations decreasing as $λ$ increases.

Planck-scale signatures of quantum gravity may emerge semiclassically not only through modifications of spacetime geometry but also through the geometry of momentum space. In this work, we develop a $(2+1)$-dimensional framework in which a noncommutative algebra of spacetime localization operators reconstructs a locally anti-de Sitter momentum-space geometry in the classical limit. The resulting momentum-space curvature deforms the phase-space structure, modifies particle kinematics, and leads to a finite renormalization of the particle mass. Using an effective configuration-space action, we derive the corresponding stress-energy tensor that consistently sources the classical Einstein equations without modifying the gravitational dynamics. The resulting spacetime is a deformed BTZ black hole whose conserved mass, horizon radius, Hawking temperature, and Bekenstein-Hawking entropy acquire finite Planck-scale corrections. We further investigate Hawking radiation using the Hamilton-Jacobi tunneling formalism and show that the return time of an emitted massless particle receives two distinct contributions: a geometric correction induced by curved momentum space and a dynamical correction arising from Hawking backreaction. Remarkably, the null geodesic equations remain unchanged, indicating that the observable effects originate entirely from the deformation of the effective spacetime geometry rather than from modifications of particle trajectories. These results provide a concrete semiclassical mechanism through which quantum kinematics encoded in curved momentum space can generate observable gravitational phenomena without requiring a quantization of spacetime itself, thereby offering a phenomenological bridge between quantum geometry and black-hole physics.

We investigate the cosmological signatures of two-field dark energy with curved field-space geometry. We numerically solve the background and linear perturbation equations and assess the validity of the effective single-field description. We examine three distinct dark-energy clustering mechanisms: effective sound-speed suppression, dynamical excitation of the heavy mode, and tachyonic instabilities induced by field-space curvature, and explore their possible imprints on the matter power spectrum and cosmic microwave background anisotropies. Our analysis establishes multifield dark energy as a rich and testable extension of quintessence, with observable clustering signatures relevant to current and future cosmological surveys.

We study static, spherically symmetric self-gravitating non-Abelian 't Hooft-Polyakov monopoles in Einstein-scalar-Gauss-Bonnet gravity for two classes of scalar-Gauss-Bonnet coupling functions. We demonstrate that the branch structure of the monopole solutions depends sensitively on the choice of the coupling function. For the polynomial coupling, we show that, for sufficiently large values of the coupling parameter, the principal part of the field equations becomes locally degenerate at a critical radius, leading to a critical solution that signals a geometric phase transition. By contrast, the exponential coupling acts as a natural regulator, preventing the degeneration of the principal part and preserving smooth field profiles. Finally, we discuss a possible physical interpretation of the critical solution, in which spacetime separates into an inner region where quantum-gravitational effects may become important and an outer region that remains well described by classical general relativity.

We present Hermes, an in situ multiresolution framework for efficient and flexible measurements of cosmic large-scale-structure statistics from discrete catalogues. Hermes reconstructs a catalogue as a continuous density field in a compact scaling-function basis and replaces explicit counting of particle tuples with algebraic operations among window-filtered fields. Standard binning schemes for counts-in-cells, two-point and higher-order correlation functions are thereby expressed through choices of window functions, while new statistics can be constructed by modifying the kernels without redesigning the estimator. We introduce PyHermes, an open-source Python implementation combining multiresolution reconstruction, FFT-based convolution, MPI/thread parallelism, and GPU acceleration. It supports isotropic and anisotropic two-point statistics, marked correlations, standard and multipole three-point functions, filtered statistics, and differential operators for derived physical fields. Tests with cosmological N-body halo catalogues demonstrate a range of clustering measurements and quantify the computational efficiency and scalability of the approach. By separating field representation from statistical windows, a single reconstructed field can be reused for many standard and customised measurements, making Hermes well suited to large data sets from current and future galaxy surveys.

Several inequivalent thermodynamic formulations of spacetimes with NUT charge obey their own first laws and Smarr relations, so macroscopic consistency alone does not fix the black hole state space. We introduce a two-horizon sector diagnostic whose temperatures are fixed by harmonic-mean relations rather than adjusted as potentials. For uncharged Taub-NUT, the sum sector closes with the mass and NUT charge, whereas the difference sector closes, within a restricted homogeneous diagnostic class tested here, only after including the rotation-like thermodynamic secondary hair $J_n=mn$. Thus, within this sector diagnostic, the NUT parameter enters through both $N=n$ and the homogeneous combination $J_n=mn$. The secondary hair is defined off shell in the homogeneous mass representation, not as a new metric parameter or asymptotic charge. Hidden conformal symmetry of the rotating Kerr-NUT parent gives a consistency check, without assuming a holographic dual.

In this study, we study static and spherically-symmetric wormhole configurations within the recently proposed class of extended symmetric teleparallel gravities characterised by the functional form $f(Q,T)=αQ+βT+γT^{2}$, where $Q$ is the non-metricity scalar, $T$ is the trace of the energy-momentum tensor, and ($α,β,γ$) are constant coupling parameters. By varying the action with respect to the metric, we derive the modified field equations and cast them in an effective Einstein-like form containing additional geometric contributions that depend on $Q$ and $T$. We conclude that the $f(Q,T)=αQ+βT+γT^{2}$ framework offers a viable arena for constructing physically realistic wormholes without invoking severe energy condition violations, opening new pathways for connecting modified gravity phenomenology with astrophysical signatures of non-trivial spacetime topologies.

Context. A significant fraction (>30%) of planet-forming disks and planetary are misaligned with respect to the rotational axis of their host stars, yet the dominant mechanism responsible for these misalignments remains unclear. Aims. We aim to observationally constrain the angular momentum of Class II protoplanetary disks and assess whether late-stage infall of material can bring sufficient angular momentum to tilt them. Methods. We first computed the angular momenta of 15 disks with surface density profiles inferred from dynamical modeling of high angular resolution ALMA observations. Based on this sample, we derived a relation linking disk angular momentum to stellar mass, disk mass, and the radius enclosing 90% of the 13CO flux and used it to estimate angular momenta of 18 more disks. We then compared disk values with theoretical predictions for late-stage accretion from clouds and observed streamers. Results. Angular momentum for most disks is lower than what theoretical models predict for late infall. This is also in qualitative agreement with comparison with streamer observations, however, characterization of mass of reservoirs feeding the streamers is needed to confirm this picture. Conclusions. Interactions with nearby clouds, resulting in late-stage infall of material onto Class II disks, can potentially explain the observed misalignments within disks and planetary systems.

The influence of relativistic motion on quantum entanglement is commonly attributed to acceleration-induced thermal noise. Here we show that, for asymmetric multipartite states, the topology of entanglement can become equally important. Considering a three-qubit Star state in the Unruh-DeWitt detector framework, we compare two inequivalent acceleration configurations in which either the central or a peripheral qubit undergoes uniform acceleration. We demonstrate that these physically equivalent accelerations lead to qualitatively different entanglement dynamics: acceleration of a peripheral qubit induces a revival of one-tangle that is absent when the central qubit accelerates, whereas genuine tripartite entanglement decays monotonically but with markedly different robustness. Our results uncover a topology-dependent mechanism for relativistic entanglement degradation, showing that the response of multipartite quantum correlations is determined jointly by Unruh thermalization and the structural role of the accelerated subsystem. This work identifies asymmetric quantum networks as a distinct platform for controlling relativistic quantum resources.