Long-lived Quasinormal Modes of Proper-Time Flow Black Holes Demonstrate Extended Stability

Quasinormal modes, or the characteristic ‘ringing’ of black holes after a disturbance, reveal crucial information about these enigmatic objects, and recent research explores how these modes behave in black holes described by a novel theoretical framework. Milena Skvortsova from Peoples’ Friendship University of Russia, along with colleagues, investigates these modes in black holes arising from a specific approach to gravity that allows for a smooth transition between standard black holes and more exotic, regular solutions. The team calculates the complex frequencies associated with these modes, discovering that their properties change with the mass of the disturbance and, significantly, demonstrate the potential for extraordinarily long-lived quasinormal modes. This finding challenges existing understanding of black hole decay and opens new avenues for probing the fundamental nature of gravity itself, suggesting a pathway to observe subtle effects previously hidden within the complex dynamics of these cosmic objects.

Employing both the Wentzel-Kramers-Brillouin approximation with Padé resummation and time-domain integration, researchers compute the complex frequencies for various values of the scalar field mass, multipole number, and deformation parameter, investigating the interaction between a scalar field and a regular black hole described by the Schwarzschild solution. Observations reveal that the real parts of the quasi-normal modes increase with the field mass, while the imaginary parts exhibit behaviour indicative of long-lived modes. Although quasi-resonances are not detected in the time-domain profiles due to the dominance of late-time tails, the asymptotic decay follows an oscillatory, slowly decaying behaviour with a power-law envelope.

Quasinormal Modes in Asymptotically Safe Black Holes

Scientists investigated the quasinormal modes of massive scalar fields within a regular black hole spacetime arising from asymptotically safe gravity, a framework seeking to resolve classical singularities while maintaining viable exterior geometries. The study employed a black hole metric derived from the proper-time renormalization group method, characterized by a deformation parameter that governs the strength of quantum corrections to the classical Schwarzschild solution. This metric smoothly interpolates between a near-extremal regular black hole and the Schwarzschild solution as the value of the parameter changes. To determine the quasinormal frequencies, researchers utilized two complementary techniques: the WKB approximation with Padé resummation and time-domain integration.

The WKB method, enhanced by Padé resummation, provided an analytical approach to approximate the complex frequencies for various scalar field masses, multipole numbers, and deformation parameters. Complementing this, time-domain integration directly solved the wave equation governing the scalar field’s evolution in the black hole spacetime, allowing for detailed analysis of the late-time behavior of the field. Experiments systematically varied the scalar field mass, multipole number, and the deformation parameter to map out the resulting quasinormal spectrum. The team meticulously analyzed the resulting data, observing that the real parts of the quasinormal modes increase with increasing scalar field mass.

Importantly, the imaginary parts of the modes exhibited behaviour indicative of long-lived modes, suggesting the potential for persistent oscillations around the black hole. While quasi-resonances were not directly detected in the time-domain profiles due to the dominance of late-time tails, the asymptotic decay of the field followed an oscillatory, slowly decaying pattern with a power-law envelope, revealing subtle but significant deviations from classical behavior. This detailed analysis provides valuable insight into how quantum corrections influence not only gravitational dynamics but also the propagation of scalar fields in the vicinity of black holes.

Black Hole Perturbations and Quasinormal Modes

A substantial body of work focuses on gravitational physics, black holes, and related topics, with a dominant theme being the study of black hole perturbations and quasinormal modes. These modes investigate how black holes respond to external disturbances such as gravitational waves or infalling matter and are crucial for detecting and characterizing these objects with gravitational wave detectors. Investigations, led by researchers like R. A. Konoplya, A.

Zhidenko, and M. Skvortsova, employ both analytical and numerical techniques to model the complex interactions between black holes and their surroundings. Alongside the study of quasinormal modes, research focuses on gravitational waves, particularly the theoretical modeling of waveforms emitted during black hole mergers. These studies aim to improve the accuracy of gravitational wave detection and provide insights into the properties of merging black holes. Furthermore, a growing body of work explores modified gravity theories, investigating how deviations from Einstein’s general relativity affect black hole solutions, quasinormal modes, and gravitational waves.

Researchers also investigate the possibility of wormholes and exotic solutions to Einstein’s equations, exploring their properties and stability. Numerical relativity and simulations play a crucial role in modeling the behavior of black holes and other gravitational systems, providing complex calculations to simulate black hole mergers and gravitational wave emission. Recent trends indicate a growing interest in wormholes, exotic solutions, and theoretical cosmology, alongside continued research on gravitational waves and modified gravity.

Quasinormal Mode Shifts Around Regular Black Holes

This research investigates the behaviour of scalar fields around a regular black hole, a solution arising from a specific approach within asymptotically safe gravity. By analysing quasinormal modes, the team demonstrated that the real part of the frequencies increases with the field’s mass, indicating a shift in the vibrational pattern. Simultaneously, they observed a decrease in the damping rate, suggesting the emergence of longer-lasting modes and a potential limitation of approximation methods when approaching quasi-resonance. The study employed both the WKB approximation with Padé resummation and direct time-domain integration to map the behaviour of these frequencies, considering the field’s mass, the black hole’s deformation, and the field’s angular momentum. Results reveal that the late-time evolution of the field is dominated by power-law tails, differing from those observed around standard black holes, and confirming that quantum corrections measurably alter field behaviour. The team highlights a connection between the calculated quasinormal spectra and grey-body factors, offering an alternative route to determine scattering characteristics, though this approach may be most reliable for fields with small mass.