General Relativity and Quantum Cosmology Papers

ALT We extend the horizon wave-function (HWF) formalism to a spherically symmetric, charged, spinless quantum source in D + 1 dimensional spacetime geometry and construct the HWFs associated with inner- as well as outer-horizons of the Tangherlini–Reissner–Nordström (TRN) black hole. The corresponding black hole formation probabilities, P_BH±, are also calculated and their sensitivities due to various source parameters including charge, mass, and D are analysed as well. Our analysis reveals that the ratio of inner- to outer-horizon probabilities, P_BH⁻/P_BH⁺, changes drastically from being unity as the source departs away from being in the extremal limit defined by α (→ 1 for extremal case). Furthermore, black hole formation probabilities are found to be highly suppressed for higher values of D, particularly for the source mass, m ≲ Λ_D, e.g., for α=0.5, the ratio, P_BH⁺(D = 5)/P_BH⁺(D=10) turn out to be approximately associated with D spatial-dimensions.

ALT The interplay between black hole thermodynamics and topology provides a strong, coordinate-independent framework for discovering the underlying structure of black hole phase transitions as well as their universal features. We explore the thermodynamic topology of the anisotropic Kerr-Newman-AdS black hole using Duan's φ-mapping theory and a complex residue approach. By creating the generalized off-shell free energy, we propose a thermodynamic vector field in the parameter space with zero points corresponding to equilibrium black hole states. The winding numbers associated with these defects are utilized to calculate the black hole's global topological number. We begin with an analysis of the entire anisotropic Kerr-Newman-AdS black hole, followed by two limiting examples. Setting the anisotropic parameter K = 0 produces the Kerr-Newman-AdS black hole, while eliminating the AdS contribution produces the Kerr-Newman black hole. The anisotropic Kerr-Newman-AdS and Kerr-Newman-AdS black ho

ALT The horizon shear of a near-extremal Kerr black hole perturbed by an eccentric extreme mass ratio inspiral shows low amplitude, high frequency oscillations (”wiggles") after periapsis passage. Previous works are unable to tie the frequency of the wiggles to the orbit, and argue they cannot be quasinormal modes (QNMs). We show that they are Kerr QNMs belonging to the damped-mode branch — that is, modes whose decay rate stays finite as the spin approaches extremality. For an equatorial prograde orbit with p = 3M and e = 0.85 and spins ranging from a/M = 0.999 to a/M = 0.99999, fits to the time-domain shear identify the fundamental (ℓ,m) = (2,1) and (3,2) modes as the dominant and first subdominant excitations. Fitting each multipole separately gives frequencies to within two standard deviations of the Kerr values and provides evidence for the excitation of the fundamental (3,1), (4,1) and (4,2) modes, though these are not resolvable in the full signal. We further argue that the same wigg

ALT We investigate axial quasinormal modes of black holes embedded in Hernquist halos, using an established analytic static geometry with an inner vacuum cavity extending to 4M_BH and solving for frame dragging to first order in rotation. We compute the fundamental and first overtone branches for mass ratios ε≡ M_BH/Mₕₐₗₒ of 0.1 and 0.01, and halo compactness C≡ Mₕₐₗₒ/a₀ in the range 10⁻⁴≤C≤0.3. The cavity geometry gives a local Kerr estimate in which redshift rescales the vacuum frequencies, horizon angular momentum sets the rotational splitting, and uniform frame dragging adds a real frequency shift. At zero spin, the cavity redshift reproduces the complex ℓ=2 frequencies with relative residuals below 0.04% for the fundamental and 0.31% for the first overtone. Its leading weak compactness behavior, 1-C, explains the weak mass ratio dependence in dilute halos; at larger compactness, the exact redshift accounts for most of the separation between the two mass ratio sequences. At fixed total

ALT We formulate the static, spherically symmetric vacuum equations of power-law metric f(R) gravity as a covariant autonomous system using the (1+1+2) formalism. The finite critical sets include the scale-invariant Clifton–Barrow solution, a Minkowski endpoint shared by the Schwarzschild family, and degenerate boundaries of the normalized chart. The Clifton–Barrow equilibrium is an outward-radial attractor over a positive interval of the power-law parameter, whereas the Schwarzschild endpoint is a saddle of the polynomially extended system. Poincaré compactification, supplemented by secondary and weighted charts, resolves several asymptotic regimes. In particular, normally attracting sheets at large normalized curvature occur in the positive-curvature sector and are separated from the negative-curvature Clifton–Barrow equilibrium. Metric reconstruction also identifies a selected scalar-flat family with a regular throat, one asymptotically flat end, and a curvature-singular end. These resu

ALT Space-based gravitational-wave detectors compare laser phases exchanged between distant spacecraft. Offset phase locking keeps beatnotes in the phasemeter band, while time-delay interferometry suppresses laser frequency noise. A disturbance of one reference can degrade the functions that depend on it, making robustness an additional criterion for choosing a phase-reference architecture. We introduce a quantitative comparison based on established cascade equations and percolation measures, with directed reference graphs and Erdős–Rényi support layers. Under uniform disturbances, the robustness score is determined by the reference-depth distribution. Under nonuniform disturbances and partial dependence, the connected-support criterion can select a different configuration from both the published depth and local-lock criteria and a reference-path baseline. The phase-locking comparisons favor configurations that limit accumulated degradation and supply downstream lasers from references reta

ALT We extend the analysis of local horizon remnants in quadratic non-metricity gravity to a specific matter trace theory with the functional form f(Q) = Q + alpha Q² + 16 pi lambda T. Here, the matter trace is defined by contracting the energy-momentum tensor with the metric from the original matter action. In the absence of explicit lambda-corrections, the theory inherits the vacuum logarithmic-connection hairy branch. To obtain a non-zero trace, we introduce polynomial non-linear electrodynamics and construct an exact magnetic branch in coincident Cartesian Kerr-Schild coordinates. The non-metricity scalar of this branch vanishes, while its matter trace is proportional to the inverse eighth power of the distance. Its metric component function is given by 1 - 2M/r + q²/r² + C/r⁶, where the correction term C equals xi(1 - 4 lambda)q⁴ / 10. Consequently, the quadratic non-metricity coupling is sterile on this branch. We derive the metric and matter equations, the Euclidean temperature, the

ALT We build an acoustic black hole in a lattice model: a draining vortex evolved by the local collide-and-stream rule of a lattice-Boltzmann model, with no acoustic metric imposed, the geometry being measured from the steady state. A horizon emerges, first located from the measured Mach profile and then confirmed by phonon ray tracing on the measured metric, and the ringdown after a perturbation follows approximately the quasinormal frequencies of the draining bathtub. The residual departures are traced to the cell-scale structure of the horizon, which is not an ideal absorber. We model it in two ways: as a reflective horizon on the ideal bathtub, with two free parameters (the modulus and phase of the reflectivity), and as the sonic point of the realised flow absorbing in its own frame, with no adjustable parameter. The second describes the horizon and the non-rotating spectrum best. Superradiance has two ingredients: the emergent geometry, which amplifies in a loss-free calculation on th

ALT We construct anisotropic self-bound stellar configurations through gravitational decoupling in the minimal geometric deformation framework and investigate their stability against linear radial perturbations. Retaining the Tolman IV temporal potential, we impose the generalized linear equation of state Pᵣ=η(ρ-ρₛ) on the complete matter distribution. Central regularity and Schwarzschild matching determine the radial geometry and relate the surface density to the compactness and stellar radius. Closed-form solutions are obtained for η=1,1/2,1/3,1/4, including the MIT bag radial relation when η=1/3 and ρₛ=4B. Since the equilibrium anisotropy does not determine its dynamical response, we introduce two material prescriptions that preserve either the anisotropy of each fluid layer or its ratio to ρ+Pᵣ. Including metric perturbations, we compute the fundamental mode and three overtones for twelve equilibrium configurations under both prescriptions. All 24 background response combinations have

ALT We construct complete vacuum initial data sets with prescribed asymptotically flat exterior geometry, including the gluing of two Schwarzschild exterior regions with small masses (which need not be positive). The construction allows for arbitrarily slow leading decay and nonzero second fundamental form. For leading terms with a fixed radial power, we first construct localized seed data sets whose constraint errors decay to any prescribed finite order, then apply the projection and stability theorems of our companion papers. The resulting vacuum data sets differ from seeds by harmonic terms controlled by Hamiltonian and momentum silhouettes, and by super-harmonic corrections. This difference of harmonic terms is measured by a relative notion of ADM energy-momentum, which is defined even for slowly-decaying data sets that do not admit an ADM energy-momentum. Upon adjusting seed data sets by either harmonic-decaying terms or compact transverse-traceless terms, we freely control this relat