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[Display omitted] • High-temperature annealing (1000 °C) of Ag island film results in embeddence of AgNPs into c-Si. • Inverted, elongated hexagonal, truncated triangular pyramidal AgNPs were obtained in c-Si (100), (110), (111), respectively. • Embedding mechanism of AgNPs occurs due to the simultaneous processes of silicon oxidation and diffusion. • Quasinormal modes demonstrated the manifestation of LSPR modes of pyramidal and triangular pyramidal AgNPs in c-Si. Embedded silver nanoparticles (AgNPs) into single-crystal silicon (c-Si) were obtained by galvanic displacement reaction and annealing at 1000 °C in H 2 O for 5–180 min. The stages of AgNPs embedding into c-Si were studied and the process mechanism was proposed which was supported by energy-dispersive X-ray and transmission infrared spectroscopies. The sizes, shapes of the embedded AgNPs and the growth rates of SiO 2 were analyzed depending on the Ag volume ratio and the crystallographic orientation of c-Si. Thus, inverted, elongated hexagonal, truncated triangular pyramidal AgNPs in c-Si (100), (110), (111) were obtained, respectively. Using spectroscopic ellipsometry, the positions of localized surface plasmon resonance (LSPR) were determined from 400 nm to 1000 nm. Optical anisotropy of pyramidal AgNPs in c-Si (110) was revealed depending on the sample rotation angle relative to the plane of incidence. Using quasinormal modes theory formalism, the positions of the LSPR multipoles for piramid and truncated triangular pyramid AgNP were determined depending on its size (50–250 nm). Also, the field enhancement factor for these shapes of AgNP with a size of 100–250 nm demonstrate values ∼ 108 in the spectral range of 650–780 nm. We believe that such structures may find application in surface-enhanced Raman spectroscopy, photovoltaics, and nonlinear optics. [ABSTRACT FROM AUTHOR]

This study derives a novel family of charged black hole solutions featuring short- and long-range modifications. These are achieved through a Yukawa-like gravitational potential modification and a nonsingular electric potential incorporation. The short-range corrections encode quantum gravity effects, while the long-range adjustments simulate gravitational effects akin to those attributed to dark matter. Our investigation reveals that the total mass of the black hole undergoes corrections owing to the apparent presence of dark matter mass and the self-adjusted electric charge mass. Two distinct solutions are discussed: a regular black hole solution characterizing small black holes, where quantum effects play a crucial role, and a second solution portraying large black holes at considerable distances, where the significance of Yukawa corrections comes into play. Notably, these long-range corrections contribute to an increase in the total mass and hold particular interest as they can emulate the role of dark matter. Finally, we explore the phenomenological aspects of the black hole. Specifically, we examine the influence of electric charge and Yukawa parameters on thermodynamic quantities, the quasinormal modes for the charged scalar perturbations as well as for the vector perturbations, analysis of the geodesics of light/massive particles, and the accretion of matter onto the charged black hole solution. [ABSTRACT FROM AUTHOR]

We calculate the quasinormal modes of scalar and neutrino perturbations around a charged black hole in Asymptotically Safe Gravity. Our results demonstrate that both the charge and coupling constant significantly alter the quasinormal spectrum. The quality factor of the quantum-corrected black hole indicates a better oscillator than its classical counterpart. The charge increases both the real oscillation frequency and the damping rate of the perturbations. In the high-frequency (eikonal) limit, we derive an explicit analytic formula for the quasinormal modes, confirming the correspondence between null circular geodesics and eikonal quasinormal frequencies. Additionally, we show that previous calculations of scalar quasinormal modes in this background suffer from a large numerical error that exceeds the effect, namely, the deviations of the frequencies from their Schwarzschild limits. [ABSTRACT FROM AUTHOR]

In this study, we investigate the signatures of a non-commutative black hole solution. Initially, we calculate the thermodynamic properties of the system, including entropy, heat capacity, and Hawking radiation. For the latter quantity, we employ two distinct methods: surface gravity and the topological approach. Additionally, we examine the emission rate and remnant mass within this context. Remarkably, the lifetime of the black hole, after reaching its final state due to the evaporation process, is expressed analytically up to a grey-body factor. We estimate the lifetime for specific initial and final mass configurations. Also, we analyze the tensorial quasinormal modes using the 6th-order WKB method. Finally, we study the deflection angle, i.e., gravitational lensing, in both the weak and strong deflection limits. [ABSTRACT FROM AUTHOR]

In this paper, we thoroughly explore two crucial aspects of a quantum Schwarzschild black solution within four-dimensional space–time: (i) the weak deflection angle, (ii) the rigorous greybody factor and, (iii) the Dirac quasinormal modes. Our investigation involves employing the Gauss–Bonnet theorem to precisely compute the deflection angle and establishing its correlation with the Einstein ring. Additionally, we derive the rigorous bounds for greybody factors through the utilization of general bounds for reflection and transmission coefficients in the context of Schrodinger-like one-dimensional potential scattering. We also compute the corresponding Dirac quasinormal modes using the WKB approximation. We reduce the Dirac equation to a Schrodinger-like differential equation and solve it with appropriate boundary conditions to obtain the quasinormal frequencies. To visually underscore the quantum effect, we present figures that illustrate the impact of varying the parameter r 0 , or more specifically, in terms of the parameter α. This comprehensive examination enhances our understanding of the quantum characteristics inherent in the Schwarzschild black solution, shedding light on both the deflection angle and greybody factors in a four-dimensional space–time framework. [ABSTRACT FROM AUTHOR]

This work investigates the shadow and quasinormal modes of a novel rotating Born–Infeld-type black hole. First, we study the effect of interaction between nonlinear electrodynamic fields and photons on shadow radius and show that it is less than the error of shadow measurements in Event Horizon Telescope (EHT) observations. Then, we obtain a rotating metric using the Newman–Janis algorithm, starting with the initial metric of the nonrotating novel Born–Infeld black hole solution. Next, we analyze the null geodesics to determine the celestial coordinates. The black hole's shadow radius is determined by using celestial coordinates. The mass, spin, charge, and nonlinearity parameters all influence the shape and size of the black hole shadow. An increase in the spin parameter results in a gradual reduction in the size of black hole shadows and further distortion of the shadows. Furthermore, constraints on the spin and electric charge of black holes, as well as the nonlinearity parameter, are derived through the utilization of the shadow sizes of supermassive black holes Sagittarius (Sgr) A* and M87* obtained from observations of the EHT. Also, we investigate the correlation between the standard shadow radius and the equatorial and polar quasinormal modes for revolving black holes. Finally, we analyze the emission energy rate from the black hole based on different spacetime parameters. Our observation indicates that the emission energy rate decreases as the values of spin and nonlinearity parameters increase, keeping the charge-to-mass ratios of the Born–Infeld black hole constant. [ABSTRACT FROM AUTHOR]

In the present paper, we investigate the quasinormal modes of an Einstein–Maxwell power-Yang–Mills black hole in four dimensions, considering a specific value of the power parameter p = 1 / 2. This particular case represents a black hole with both Abelian and Non-Abelian charges and is asymptotically non-flat. We begin by deriving the effective potential for both a neutral massless particle and a neutral Dirac particle using the aforementioned black hole solution. Subsequently, employing the sixth-order WKB approximation method, we calculate the (scalar) quasinormal modes. Our numerical analysis indicates that these modes are stable within the considered parameter range. This result is also confirmed using the eikonal approximation. Furthermore, we calculate the shadow radius for this class of BH and derive constraints on the electric and Yang–Mills charges (Q , Q Y M ) by using imaging observational data for Sgr A ⋆ , provided by the Event Horizon Telescope Collaboration. We observe that as the electric charge Q increases, the allowed range shifts towards negative values of Q Y M. For instance, for the maximum value Q ≈ 1. 1 obtained, the allowed range becomes − 0. 171 ≲ Q Y M ≲ − 0. 087 consistent with KECK and VLTI data, while still retaining a non-vanishing horizon. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate a comprehensive study of the optical properties of hemispherical Ag nanoparticles (AgNPs) on a single-crystal (c-Si) wafer. The fabricated method involves a galvanic displacement reaction of Ag on c-Si and annealing in oxygen atmosphere at 500 °C. Substrates with different morphological parameters of AgNPs were obtained by varying the volume ratio of Ag in the deposition solution. Using the quasinormal modes (QNMs) theory formalism, the localized surface plasmon resonance (LSPR) multipole positions were determined as a function of the AgNP size and incidence angle. Also, the effective field approximation and QNMs methods were used to calculate the specular reflectance of the disordered hemispherical array on c-Si. Thus, the experimentally obtained LSPR positions in the reflectance spectra were described. Finally, surface-enhanced Raman scattering (SERS) demonstrated reliable detection of brilliant green triphenylmethane dye (1 nM), methyl red dye (10 nM) and hemoglobin from bovine blood (1 mM). The dependence of the SERS enhancement factor on the LSPR position and the absorption band of the analyte was established, the maximum value of which was 1.1 × 10 7. In summary, this study suggests that the numerical and experimental investigation of the optical properties of hemispherical AgNPs on c-Si contributes to the field of optical sensing. [Display omitted] • Hemispherical AgNPs on c-Si have been fabricated by GDR and annealing in O 2. • Positions of the LSPR multipoles were determined using quasinormal modes (QNMs). • EFA and QNMs were used to calculate reflectance of the disordered AgNPs array on c-Si. • Dependence of EF on LSPR position and absorption band of the analyte was established. • SERS showed reliable detection of BG (1 nM) and MR (10 nM) solutions with EFs ∼ 10 7 and ∼ 10 6. [ABSTRACT FROM AUTHOR]

We show that perturbations of a scalar field in the background of the spherically symmetric black hole obtained with the Starobinsky-Bel-Robinson Gravity are unstable unless the dimensionless coupling β describing the compactification of M-theory is small enough. In the sector of stability quasinormal spectrum show peculiar behavior both in the frequency and time domains: the ringing consists of two stages where two different modes dominate. The WKB method does not reproduce part of the spectrum including the fundamental mode, which is responsible for the first stage of the ringing. As a result, the correspondence between the high frequency quasinormal modes and characteristics of the null geodesics reproduces only one branch of the eikonal spectrum. The frequencies are obtained with the help of three methods (Frobenius, WKB and time-domain integration) with excellent agreement among them. [ABSTRACT FROM AUTHOR]

In this work, the quasinormal modes of a 5-D black hole in Einstein Gauss–Bonnet Bumblebee theory of gravity have been investigated with the help of the Padé averaged higher order WKB approximation method and the validity of Hod's conjecture has been studied. It is found that the presence of Lorentz symmetry breaking due to the Bumblebee field favours Hod's conjecture. But in the case of the Gauss–Bonnet term, an increase in the coupling parameter increases the chances of violation of Hod's conjecture. We further investigated the optical properties of the black hole viz. , shadow and emission rate. It is found that a black hole with a lower lifetime favours Hod's conjecture. [ABSTRACT FROM AUTHOR]

We investigate the role that quasinormal modes can play in kink–antikink collisions, via an example based on a deformation of the ϕ 4 model. We find that narrow quasinormal modes can store energy during collision processes and later return it to the translational degrees of freedom. Quasinormal modes also decay, which leads to energy leakage, causing a closing of resonance windows and an increase of the critical velocity. We observe similar phenomena in an effective model, a small modification of the collective-coordinate approach to the ϕ 4 model. [ABSTRACT FROM AUTHOR]

The current study aims to examine the impact of the boundary term on the bending angle of light for a static spherically symmetric black hole in the modified gravity described by the f (T , B) function. To accomplish this objective, we employ the Ishihara et al. method, which enables us to compute the deflection angle of light for a receiver and source situated at finite distances from a lens object in a non-asymptotically flat spacetime. This method considers the receiver's viewpoint, and the resulting deflection angle diverges as the distance from the lens object increases, owing to the non-asymptotically flat spacetime. Nevertheless, the divergence can be regulated by the boundary term parameter c 0. For lower values of the parameter c 0 , the divergence can be minimized within the finite range of the observer and source. Furthermore, we calculate the quasinormal modes of massless scalar perturbations in the black hole's background using the asymptotic iteration method (AIM) and Padé averaged sixth-order Wentzel–Kramers–Brillouin (WKB) approximation method. Our findings indicate that the real quasinormal modes and damping rates are significantly impacted by the model parameter c 0. Subsequently, we investigate two optical characteristics of the black hole, namely the shadow and the emission rate. Our results show that with an increase in the boundary term parameter c 0 , both the shadow's size and the evaporation rate decrease. [ABSTRACT FROM AUTHOR]

Symmergent gravity is an emergent gravity framework in which gravity emerges guided by gauge invariance, accompanied by new particles, and reconciled with quantum fields. In this paper, we perform a detailed study of the quasinormal modes and greybody factors of the black holes in symmergent gravity. Its relevant parameters are the quadratic curvature term c O and the vacuum energy parameter α. In our analyses, effects of the both parameters are investigated. Our findings suggest that, in both positive and negative direction, large | c O | values of the parameter on the quasinormal modes parallel the Schwarzschild black hole. Moreover, the quasinormal model spectrum is found to be sensitive to the symmergent parameter α. We contrast the asymptotic iteration and WKB methods in regard to their predictions for the quasinormal frequencies, and find that they differ (agree) slightly at small (large) multipole moments. We analyze time-domain profiles of the perturbations, and determine the greybody factor of the symmergent black hole in the WKB regime. The symmergent parameter α and the quadratic curvature term c O are shown to impact the greybody factors significantly. We provide also rigorous limits on greybody factors for scalar perturbations, and reaffirm the impact of model parameters. [ABSTRACT FROM AUTHOR]

The elegant predictions of loop quantum gravity are obscured by the free Immirzi parameter ( γ ). Dreyer (2003), considering the asymptotic quasinormal modes spectrum of a black hole, proposed that γ may be fixed by letting the j = 1 transitions of spin networks as the dominant processes contributing to the black hole area, as opposed to the expected j = 1 / 2 transitions. This suggested that the gauge group of the theory might be SO ( 3 ) rather than SU ( 2 ) . Corichi (2003), maintaining SU ( 2 ) as the underlying gauge group, and invoking the principle of local fermion-number conservation, reported the same value of γ for j = 1 processes as obtained by Dreyer. In this note, preserving the SU ( 2 ) structure of the theory, and considering j = 1 transitions as the dominant processes, we point out that the value of γ is in fact twice the value reported by these authors. We arrive at this result by assuming the asymptotic quasinormal modes themselves as dynamical systems obeying SU ( 2 ) symmetry. [ABSTRACT FROM AUTHOR]

Abstract: We study the perturbation of the scalar field interacting with the Maxwell field in the background of d-dimensional charged AdS black hole and AdS soliton. Different from the single classical field perturbation, which always has the decay mode in the black hole background, we observe the possible growing mode when the perturbation of the scalar field strongly couples to the Maxwell field. Our results disclose the signature of how the phase transition happens when the interaction among classical fields is strong. The sudden change of the perturbation to growing mode is also observed in the AdS soliton with electric potential. However in the magnetic charged AdS soliton background, we observe the consistent perturbation behavior when the interaction between scalar field and Maxwell field is considered. This implies that for the magnetic charged AdS soliton configuration, unlike the situation with electric potential, there is no scalar field condensation which causes the phase change. [Copyright &y& Elsevier]

Abstract: We study the quasinormal modes of the massless scalar perturbation in the background of a deformed black hole in the Hořava–Lifshitz gravity with coupling constant . Our results show that the quasinormal frequencies depend on the parameter in the Hořava–Lifshitz gravity and the behavior of the quasinormal modes is different from those in the Reissner–Norström and Einstein–Born–Infeld black hole spacetimes. The absolute value of imaginary parts is smaller and the scalar perturbations decay more slowly in the deformed Hořava–Lifshitz black hole spacetime. This information can help us understand more about the Hořava–Lifshitz gravity. [Copyright &y& Elsevier]

Abstract: The determination of the quantum area spectrum of a black hole horizon by means of its asymptotic quasinormal frequencies has been explored recently. We believe that for D-dimensional de Sitter horizon we must study if the idea works. Thus taking into account the local description of the thermodynamics of horizons proposed by Padmanabhan and the results of Hod, Kunstatter, and Maggiore we study the area spectrum of the D-dimensional de Sitter horizon. [Copyright &y& Elsevier]

One of the notable modifications of General Relativity (GR) is the Rastall gravity. We have studied the quasinormal modes of black holes in Rastall gravity in presence of non-linear electrodynamic sources. Here the impacts of cosmological field, dust field, phantom field, quintessence field and radiation field on the quasinormal modes in presence of electrodynamic sources have been investigated. Apart from this, we have also checked the dependency of quasinormal modes with the Rastall parameter λ , black hole structural constant N s and charge of the black hole Q. The study shows that the quasinormal modes corresponding to the black hole with non-linear electrodynamic sources show significant deviations from a general charged black hole in Rastall gravity under certain conditions. Further, the behaviour of black holes and hence the quasinormal modes depend on the type of surrounding field considered. [ABSTRACT FROM AUTHOR]

Abstract: Motivated by the recent work about a new physical interpretation of quasinormal modes by Maggiore, we investigate the quantization of near-extremal Schwarzschild–de Sitter black holes in the four-dimensional spacetime. Following Kunstatter''s method, we derive the area and entropy spectrum of near-extremal Schwarzschild–de Sitter black holes which differs from Setare''s result. Furthermore, we find that the derived area spectrum is equally spaced. [Copyright &y& Elsevier]

In this study, we investigate the solutions of the massive and massless Dirac equation, at first, in the 2 + 1 dimensional gravitational wave background and then in the background with the presence of a constant magnetic field. In both situations, using the solutions obtained in terms of the confluent Heun functions, we calculate the quasinormal modes (QNMs) and discuss the stability conditions of the background. Comparing the quality factors derived from the QNMs in the existence of Dirac field mass and constant magnetic field with together, we see that the magnetic field plays a very important role in reducing the number of the gravitational wave oscillations because of its damping or screening effect, but there is no magnetic field effect on the proper oscillations of the gravitational wave. In addition, we acquire quasi-resonance modes (QRMs) for the massive test field in the absence of magnetic field and massless Dirac field in the presence of magnetic field from these QNMs. In both situations, the gravitational wave (GW) background becomes a good oscillator because the quality factor is very high. Moreover, we discuss the gravitational redshift for the wave background. Finally, we see that the obtained the GW frequencies and redshift values in the context of the study are compatible with the observational data. [ABSTRACT FROM AUTHOR]