scholarly journals Constraints on quasinormal modes and bounds for critical points from pole-skipping

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Navid Abbasi ◽  
Matthias Kaminski
Keyword(s):  
Critical Points ◽  
Thermal State ◽  
Quasinormal Modes ◽  
Scalar Perturbation ◽  
Black Brane ◽  
Massive Scalar ◽  
Dual Operator ◽  
Conformal Dimension ◽  
Scalar Operator ◽  
First Time

Abstract We consider a holographic thermal state and perturb it by a scalar operator whose associated real-time Green’s function has only gapped poles. These gapped poles correspond to the non-hydrodynamic quasinormal modes of a massive scalar perturbation around a Schwarzschild black brane. Relations between pole-skipping points, critical points and quasinormal modes in general emerge when the mass of the scalar and hence the dual operator dimension is varied. First, this novel analysis reveals a relation between the location of a mode in the infinite tower of quasinormal modes and the number of pole-skipping points constraining its dispersion relation at imaginary momenta. Second, for the first time, we consider the radii of convergence of the derivative expansions about the gapped quasinormal modes. These convergence radii turn out to be bounded from above by the set of all pole-skipping points. Furthermore, a transition between two distinct classes of critical points occurs at a particular value for the conformal dimension, implying close relations between critical points and pole-skipping points in one of those two classes. We show numerically that all of our results are also true for gapped modes of vector and tensor operators.

scholarly journals Instability of charged massive scalar fields in bound states around Kerr–Sen black holes

2015 ◽  
Vol 24 (14) ◽  
pp. 1550102 ◽  
Author(s):  
Haryanto M. Siahaan
Keyword(s):  
Black Holes ◽  
Bound States ◽  
Gordon Equation ◽  
Scalar Fields ◽  
Bound State ◽  
Imaginary Component ◽  
Scalar Perturbation ◽  
Massive Scalar ◽  
Massive Scalar Field ◽  
Klein Gordon

In this paper, we show the instability of a charged massive scalar field in bound states around Kerr–Sen black holes. By matching the near and far region solutions of the radial part in the corresponding Klein–Gordon equation, one can show that the frequency of bound state scalar fields contains an imaginary component which gives rise to an amplification factor for the fields. Hence, the unstable modes for a charged and massive scalar perturbation in Kerr–Sen background can be shown.

ASYMPTOTIC QUASINORMAL MODES IN EINSTEIN–GAUSS–BONNET GRAVITY

2011 ◽  
Vol 26 (16) ◽  
pp. 2783-2794 ◽  
Author(s):  
J. SADEGHI ◽  
A. BANIJAMALI ◽  
M. R. SETARE ◽  
H. VAEZ
Keyword(s):  
Scalar Field ◽  
Effective Potential ◽  
Quasinormal Modes ◽  
Space Time ◽  
Massive Scalar ◽  
Massive Scalar Field ◽  
Momentum Vector ◽  
Five Dimensions ◽  
Bonnet Gravity ◽  
Temperature Scalar

In this paper we consider a massive scalar field on the boundary of AdS space–time and calculate the quasinormal modes for the string inspired Einstein–Gauss–Bonnet gravity in five dimensions. We study the effects of Gauss–Bonnet parameter, temperature, scalar field's mass and momentum vector on the effective potential and quasinormal modes.

scholarly journals Massive scalar field quasinormal modes of a Schwarzschild black hole surrounded by quintessence

Open Physics ◽  
2008 ◽  
Vol 6 (2) ◽  
Author(s):  
Chunrui Ma ◽  
Yuanxing Gui ◽  
Wei Wang ◽  
Fujun Wang
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Quasinormal Modes ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Massive Scalar ◽  
Schwarzschild Black Hole ◽  
Third Order ◽  
Massive Scalar Field ◽  
Absolute Value

AbstractWe present the quasinormal frequencies of the massive scalar field in the background of a Schwarzchild black hole surrounded by quintessence with the third-order WKB method. The mass of the scalar field u plays an important role in studying the quasinormal frequencies, the real part of the frequencies increases linearly as mass of the field u increases, while the imaginary part in absolute value decreases linearly which leads to damping more slowly than the massless scalar field. The frequencies have a limited value, so it is easier to detect the quasinormal modes. Moreover, owing to the presence of the quintessence, the massive scalar field damps more slowly.

scholarly journals Учет влияния перекоса в зазоре между плунжером и втулкой на величину утечек в авиационном аксиально-плунжерном насосе

2021 ◽  
pp. 24-31
Author(s):  
Владимир Николаевич Доценко ◽  
Иван Григорьевич Лихошерст
Keyword(s):  
Thermal State ◽  
Relative Length ◽  
Theoretical Research ◽  
Cylinder Block ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Plunger Pump ◽  
Finite Element Software ◽  
First Time ◽  
Axial Piston

The subject of study in the article is the amount of leaks of the working fluid in the gap between the plunger and the bushing of an aircraft axial-plunger pump, depending on the position of the plunger relative to the bushing. The level of fluid leaks in the gap between the plunger and the cylinder block bushing is a component of volumetric losses, affects the thermal state, wear, the state of the plunger-bushing pair, as well as the level of pressure pulsations of the working fluid and, ultimately, the change in the efficiency of the axial-plunger pump. Researches deal with the influence of piston defects in a bushing on losses through a gap between them that is not discovered in existent literature. The aim of this work is theoretical research of the influence of piston defect on the leakage of working liquid through a gap between the piston and cylindrical bushing in aviation axial-piston pump under workloads. The tasks are: it is necessary to define the losses quantity for the three cases: the axes of piston and bushing coincide; piston is displaced (axes are parallel) with a maximal eccentricity ε = 0.99; piston is twisted in a bushing so that the edges of piston touch a bushing. For the problem-solving methods as follows were used. The task of thin film laminar flow in a gap between piston and bushing was solved by a numeral method in finite-element software. Losses on a piston are considered as a sum of the losses, related to the motion of the piston at a speed W and losses due to the pressure gradient dp/dz. The results are: to obtain the laws of geometrical parameters influence on the losses amount investigation for one piston was undertaken in the first part of the study. It is marked that most losses take place for piston displaced in parallel, and the least - for twisted. Total losses for the real pump on different operational behaviors are considered and volume loss-of-flows are obtained in the second part of the article. Conclusions. Dependences of losses through a gap at the different gap sizes and relative length of bushing for twisted piston are first time obtained. The results allow estimating the losses quantity in a pump on the efficiency of his work at planning and exploitation.

scholarly journals Quasinormal modes of a semi-holographic black brane and thermalization

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Sukrut Mondkar ◽  
Ayan Mukhopadhyay ◽  
Anton Rebhan ◽  
Alexander Soloviev
Keyword(s):  
Degrees Of Freedom ◽  
Mutual Coupling ◽  
Zero Mode ◽  
Quasinormal Modes ◽  
Dissipative System ◽  
Black Brane ◽  
Full System ◽  
Strongly Coupled ◽  
Constant Rate ◽  
Two Sectors

Abstract We study the quasinormal modes and non-linear dynamics of a simplified model of semi-holography, which consistently integrates mutually interacting perturbative and strongly coupled holographic degrees of freedom such that the full system has a total conserved energy. We show that the thermalization of the full system can be parametrically slow when the mutual coupling is weak. For typical homogeneous initial states, we find that initially energy is transferred from the black brane to the perturbative sector, later giving way to complete transfer of energy to the black brane at a slow and constant rate, while the entropy grows monotonically for all time. Larger mutual coupling between the two sectors leads to larger extraction of energy from the black brane by the boundary perturbative system, but also quicker irreversible transfer of energy back to the black brane. The quasinormal modes replicate features of a dissipative system with a softly broken symmetry including the so-called k-gap. Furthermore, when the mutual coupling is below a critical value, there exists a hybrid zero mode with finite momentum which becomes unstable at higher values of momentum, indicating a Gregory-Laflamme type instability. This could imply turbulent equipartitioning of energy between the boundary and the holographic degrees of freedom in the presence of inhomogeneities.

scholarly journals Superradiant stability of five and six-dimensional extremal Reissner–Nordstrom black holes

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
Jia-Hui Huang ◽  
Tian-Tian Cao ◽  
Mu-Zi Zhang
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Numerical Methods ◽  
Effective Potential ◽  
Scalar Perturbation ◽  
Polynomial Equations ◽  
Potential Well ◽  
Massive Scalar ◽  
Higher Dimensional ◽  
The Stability

AbstractWe revisit the superradiant stability of five and six-dimensional extremal Reissner–Nordstrom black holes under charged massive scalar perturbation with a new analytical method. In each case, it is analytically proved that the effective potential experienced by the scalar perturbation has only one maximum outside the black hole horizon and no potential well exists for the superradiance modes. So the five and six-dimensional extremal Reissner–Nordstrom black holes are superradiantly stable. The new method we developed is based on the Descartes’ rule of signs for the polynomial equations. Our result provides a complementary support of previous studies on the stability of higher dimensional extremal Reissner–Nordstrom black holes based on numerical methods.

scholarly journals Stability and phase transition of rotating Kaluza–Klein black holes

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
Seyed Hossein Hendi ◽  
Somayeh Hajkhalili ◽  
Mubasher Jamil ◽  
Mehrab Momennia
Keyword(s):  
Black Hole ◽  
Black Hole Solution ◽  
Canonical Ensemble ◽  
Quasinormal Modes ◽  
Scalar Perturbation ◽  
Thermodynamic Quantities ◽  
Resonance Modes ◽  
Maxwell Electrodynamics ◽  
The Stability ◽  
Kaluza Klein

AbstractIn this paper, we investigate the thermodynamics and phase transitions of a four-dimensional rotating Kaluza–Klein black hole solution in the presence of Maxwell electrodynamics. Calculating the conserved and thermodynamic quantities shows that the first law of thermodynamics is satisfied. To find the stable black hole’s criteria, we check the stability in the canonical ensemble by analyzing the behavior of the heat capacity. We also consider a massive scalar perturbation minimally coupled to the background geometry of the four-dimensional static Kaluza–Klein black hole and investigate the quasinormal modes by employing the Wentzel–Kramers–Brillouin (WKB) approximation. The anomalous decay rate of the quasinormal modes spectrum is investigated by using the sixth-order WKB formula and quasi-resonance modes of the black hole are studied with averaging of Padé approximations as well.

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