Hole Configurations Research Articles

Black hole thermodynamics is extensive with variable Newton constant

Inspired by the recent studies on the thermodynamics of AdS black holes in the restricted phase space formalism, we propose a similar formalism for the thermodynamics of non-AdS black holes with variable Newton constant. It is shown that, by introducing the new variables N,μ, where N is proportional to the inverse Newton constant and μ its conjugate variable, referred to as the chemical potential, the black hole thermodynamics can be formulated in a form which is consistent with the standard extensive thermodynamics for open macroscopic systems, with the first law and the Euler relation hold simultaneously. This formalism has profound implications, in particular, the mass is a homogeneous function of the first order in the extensive variables and the intensive variables are zeroth order homogeneous functions. The chemical potential is shown to be closely related to the Euclidean action evaluated at the black hole configuration.

Quenching of Gamow-Teller strengths and two-particle–two-hole configurations

We apply the charge-exchange subtracted second random-phase approximation (SSRPA), based on Skyrme functionals, to investigate Gamow-Teller resonances in several closed-shell and closed-subshell nuclei, located in different regions of the nuclear chart. After having discussed the SSRPA findings obtained within different approximation schemes in $^{48}$Ca, we compare our results with {\it{ab-initio}} coupled-cluster predictions available for C and O isotopes, where two-body currents are included. Our integrated strenghts, obtained by using one-body transition operators, are lower compared to the corresponding {\it{ab-initio}} results. This indicates that, within our model, quenching effects are mainly driven by the inclusion of two particle - two hole configurations and that the role of a two-body contribution in the transition operator is less important than in the coupled-cluster approach. By analyzing heavier nuclei, $^{90}$ Zr and $^{132}$Sn, we confirm the same conclusions that we have recently drawn for $^{48}$Ca: the inclusion of two particle - two hole configurations is very effective in our model for providing strengths which are significantly more quenched than in other theoretical models and, thus, in better agreement with the experimental measurements. This occurs because two particle - two hole configurations have a density which strongly increases with the excitation energy. Their inclusion thus pushes a significant amount of the strength to higher energies, compared to what happens in other theoretical models, reducing in this way the cumulative sum of the strength up to excitation energies around 20-30 MeV.

Accessible high-performance double nanohole tweezers.

Nanohole optical tweezers have been used by several groups to trap and analyze proteins. In this work, we demonstrate that it is possible to create high-performance double nanohole (DNH) substrates for trapping proteins without the need for any top-down approaches (such as electron microscopy or focused-ion beam milling). Using polarization analysis, we identify DNHs as well as determine their orientation and then use them for trapping. We are also able to identify other hole configurations, such as single, trimers and other clusters. We explore changing the substrate from glass to polyvinyl chloride to enhance trapping ability, showing 7 times lower minimum trapping power, which we believe is due to reduced surface repulsion. Finally, we present tape exfoliation as a means to expose DNHs without damaging sonication or chemical methods. Overall, these approaches make high quality optical trapping using DNH structures accessible to a broad scientific community.

Quantum geometric information flows and relativistic generalizations of G. Perelman thermodynamics for nonholonomic Einstein systems with black holes and stationary solitonic hierarchies

We investigate classical and quantum geometric information flow theories (respectively, GIFs and QGIFs) when the geometric flow evolution and field equations for nonholonomic Einstein systems, NES, are derived from Perelman-Lyapunov type entropic type functionals. In this work, the term NES encodes models of gravitational and matter fields interactions and their geometric flow evolution subjected to nonholonomic (equivalently, non-integrable, anholonomic) constraints. There are used canonical geometric variables which allow a general decoupling and integration of systems of nonlinear partial differential equations describing GIFs and QGIFs and (for self-similar geometric flows) Ricci soliton type configurations. Our approach is different from the methods and constructions elaborated for special classes of solutions characterized by area--hypersurface entropy, related holographic and dual gauge--gravity models, and conformal field theories, involving generalizations of the Bekenstein-Hawking entropy and black hole thermodynamics. We formulate the theory of QGIFs which in certain quasi-classical limits encodes GIFs and models with flow evolution of NES. There are analysed the most important properties (inequalities) for NES and defined and computed QGIF versions of the von Neumann, relative and conditional entropy; mutual information, (modified) entanglement and R\'{e}nyi entropy. We construct explicit examples of generic off-diagonal exact and parametric solutions describing stationary solitonic gravitational hierarchies and deformations of black hole configurations. Finally, we show how Perelman's entropy and geometric thermodynamic values, and extensions to GIF and QGIF models can be computed for various new classes of exact solutions which cannot be described following the Bekenstein-Hawking approach.

Jet Impingement Heat Transfer Characteristics with Variable Extended Jet Holes under Strong Crossflow Conditions

In this paper, detailed flow patterns and heat transfer characteristics of a jet impingement system with extended jet holes are experimentally and numerically studied. The jet holes in the jet plate present an inline array of 16 × 5 rows in the streamwise (i.e., the crossflow direction) and spanwise directions, where the streamwise and spanwise distances between adjacent holes, which are normalized by the jet hole diameter (xn/d and yn/d), are 8 and 5, respectively. The jets impinge onto a smooth target plate with a normalized distance (zn/d) of 3.5 apart from the jet plate. The jet holes are extended by inserting stainless tubes throughout the jet holes and the extended lengths are varied in a range of 1.0d–2.5d, depending on the jet position in the streamwise direction. The experimental data is obtained by using the transient thermochromic liquid crystal (TLC) technique for wide operating jet Reynolds numbers of (1.0 × 104)–(3.0 × 104). The numerical simulations are well-validated using the experimental data and provide further insight into the flow physics within the jet impingement system. Comparisons with a traditional baseline jet impingement scheme show that the extended jet holes generate much higher local heat transfer levels and provide more uniform heat transfer distributions over the target plate, resulting in the highest improvement of approximately 36% in the Nusselt number. Although the extended jet hole configuration requires a higher pumping power to drive the flow through the impingement system, the gain of heat transfer prevails over the penalty of flow losses. At the same pumping power consumption, the extended jet hole design also has more than 10% higher heat transfer than the baseline scheme.

Planar black holes configurations and shear viscosity in arbitrary dimensions with shift and reflection symmetric scalar-tensor theories

In higher dimensions, we explore planar hairy black hole configurations for a special subclass of the Horndeski theory defined by two coupling functions depending on the kinetic term and enjoying shift symmetry and reflection symmetry. For this analysis, we derive a set of new solutions given by time-dependent as well as time-independent scalar field configurations. Additionally, we calculate their thermodynamic quantities by using Wald formalism satisfying the first law of thermodynamics as well as a Smarr relation. Together with the above, the Wald procedure allows us to compute the shear viscosity, showing that for a suitable choice of the coupling functions the Kovtun-Son-Starinets bound is violated.

Controlled and localized antibiotics delivery using magnetic-responsive beads for synergistic treatment of orthopedic infection.

Antibiotic-loaded bone cement beads have been a reliable passive delivery system for the localized treatment of osteomyelitis; however, low, and unregulated drug release rates limit the ability of this system to maintain therapeutic concentrations. This problem is further amplified by drug-resistant pathogens that might invade or evolve under these conditions. Furthermore, currently available bone cements are incompatible with some antibiotics. The proposed device resembles conventional bone cement beads but contains an on-demand drug delivery magnetic sponge that provides actively controlled release of antibiotics. The slightly porous structure facilitates some drug diffusion while further drug release may be controlled remotely via magnetic actuation. Additionally, a combination of silver nitrate and gentamicin are used in the device as these agents are shown to display a synergistic antibacterial activity in vitro using checkerboard and time-kill assays. The device releases gentamicin and silver in both actuation and diffusion modes over 7 days. The in vitro bacterial studies demonstrate the efficacy of the released agents alone, and synergistically in combination, against Methicillin-resistant Staphylococcus aureus and Escherichia coli. The proposed device offers a facile fabrication process which allows control of the release profile by engineering hole configurations or manipulating magnetic field strength to provide the most effective therapy.

Aerodynamics effect of holes in UAV wings modified for VTOL capability

This research investigates the possibility of modifying the X8 Skywalker from a fixed-wing unoccupied aerial vehicle into a convertiplane to utilize the advantages of vertical take-off and landing and maintain the benefits of fixed-wing design. In this study two configurations were tested; the first one includes sharp holes embedded in the wings for the propellers and the second one has filleted holes. The purpose of the study is to analyze the new configurations’ ability to generate enough lift after reducing the wings area. The aerodynamic coefficients are calculated through computational fluid dynamics. Simulation results were validated experimentally by using the wind tunnel. Even though the holes reduced the wing area by about 20%, the proposed modifications could lead to a lift to drag ratio around 7. The results showed that the new configurations can generate five times the lift compared to the drag, while the maximum lift to drag ratio dropped by 50% compared to the original design. At the same time, the filleted hole configuration showed less drag and turbulence effects, especially at a low angle of attack, compared to the sharp hole configuration.

Effect of Hole Configuration on Heat Transfer through a Hollow Block Subjected to Solar Flux

In this paper, some effort is provided to optimize the geometry of a concrete hollow brick (used in the construction of building roofs) in order to increase the related thermal resistance, thereby reducing energy consumption. The analysis is conducted for three different configurations of the hollow concrete bricks. Coupling of conduction, natural convection and thermal radiation phenomena is considered. Moreover, the flows are assumed to be laminar and two-dimensional for the whole range of parameters examined. The conservation equations are solved by a finite difference method based on the control volumes approach and the SIMPLE algorithm for velocity-pressure coupling. The results show that the aspect ratio affects neither the nature of the fluid flow nor the number of convective cells. However, the extension of the circulation cells increases with this parameter. Moreover, the cavities with a large aspect ratio lead to significant reductions in the heat transfer through the hollow block, these reductions reaching approximately 14%.

Visual outcome of macular hole surgery based on pre-operative hole configuration in optical coherence tomography from a developing country-Nepal

Visual outcome of macular hole surgery based on pre-operative hole configuration in optical coherence tomography from a developing country-Nepal

Effect of three and five holes nozzle on thermal efficiency and emission characters of DI-CI diesel engine with lemongrass biodiesel as alternate fuel

The performance and emissions characters of Diesel engine behavior depend largely on several criteria, fuel injection nozzle plays a vital role in the proper combustion of Diesel engines. This research analyzes the impact of a nozzle hole configuration on the features of a biodiesel-fuelled Diesel engine. Therefore, the causes are dependent on the modification that the nozzle hole was selected from three-hole and five-hole nozzles, while the engine characteristics of the lemongrass biodiesel blend with diesel were examined. Lemongrass biodiesel with 20% blend, LGB B20, has been investigated experimentally with different engine loads with respect to brake power, three-hole, and five-hole nozzles. The experimental investigation showed an improvement in peak i.e. highest heat release rate of 12.5% for three- and five-hole nozzle and brake specific fuel consumption of 15% is increased in single hole nozzle and it is observed it?s diminished in three- and five-holed nozzle. Further, the brake thermal efficiency is increased in the five-hole nozzle in comparison to the three-hole nozzle at full load condition. Furthermore emission characteristics like HC, CO, and smoke are de-creased with an increase in the number of nozzles, at the penalty of increase in NOx emissions has been observed.

Possible existence of multiple wobbling modes in A≈60 nuclei

The nuclear multiple wobbling modes in $A\ensuremath{\approx}60$ mass region are explored by the adiabatic and configuration-fixed constrained covariant density functional theory for nickel isotopes for the first time. The potential-energy curves and deformation parameters $\ensuremath{\beta}$ and $\ensuremath{\gamma}$ of the ground and excited states of $^{57\text{--}62}\mathrm{Ni}$ are obtained to search for the possible wobbling candidates. It is shown that there are suitable triaxial deformations and high-$j$ particle(s) or hole(s) configurations in $^{57\text{--}62}\mathrm{Ni}$, which are beneficial to the appearance of wobbling motion, including the simple, longitudinal and transverse modes. Moreover, possible multiple wobbling motions based on different high-$j$ configurations might coexist in one single nucleus, which provides a promising basis for future experiments to find wobbling bands in the $A\ensuremath{\approx}60$ mass region. Finally, taking the nucleus $^{62}\mathrm{Ni}$ as an example, the experimental energy spectra, the angular momentum components, and the azimuthal plots are investigated by the combination of the covariant density functional theory and quantum particle rotor model. The transverse wobbling mode is suggested in this nucleus.

Can We Prescribe the Physical Parameters of Multiple Black Holes?

The parabolic-hyperbolic form of the constraints and superposed Kerr-Schild black holes have already been used to provide a radically new initialization of binary black hole configurations. The method generalizes straightforwardly to multiple black hole systems. This paper is to verify that each of the global Arnowitt-Deser-Misner quantities of the constructed multiple black hole initial data can always be prescribed, as desired, in advance of solving the constraints. These global charges are shown to be uniquely determined by the physical parameters of the involved individual Kerr-Schild black holes.

Complexity conjecture of regular electric black holes

Recently, the action growth rate of a variety of four-dimensional regular magnetic black holes in F frame is obtained in [1]. Here, we study the action growth rate of a four-dimensional regular electric black hole in P frame that is the Legendre transformation of F frame. We also investigate the action growth rates of the Wheeler-De Witt patch for such black hole configurations at the late time and examine the Lloyd bound on the rate of quantum computation. We show that although the form of the Lloyd bound formula remains unaltered, the energy modifies due to a non-vanishing trace of the energy-momentum tensor and some extra terms may appear in the total growth action. We also investigate the asymptotic behavior of complexity in two conjectures for static and rotating regular black holes.

Critical effective radius for holes in thin films: Energetic and dynamic considerations

Questions regarding the stability of holes and arrays of holes in solid thin films have attracted much attention over the past few decades since an absence of holes is necessary for certain devices to operate properly and a presence of holes is needed in various industrial applications. Here, we study the energetic and dynamic stability of a single axisymmetric grain with a hole at its center, under the assumption that the exterior surface evolves by surface diffusion. Our energetic considerations enable us to formulate a criterion in terms of a critical effective hole radius, which distinguishes between energetically stable and unstable steady state hole configurations and which, somewhat surprisingly, is independent of the contact angle at the substrate and should be readily measurable in experiments. The set of steady states for the system is characterized in terms of admissible nodoidal surfaces, whose dynamic stability is studied via numerical simulation of the full non-linear dynamic problem for zero-volume perturbations. Our dynamic stability study confirms and extends our conclusions based on energetic considerations. Our results, moreover, confirm and extend the classical results of Srolovitz and Safran [J. Appl. Phys. 60, 247–254 (1986); J. Appl. Phys. 60, 255–260 (1986)] and Wong et al. [J. Appl. Phys. 81, 6091–6099 (1997); Acta Mater. 45, 2477–2484 (1997)]. Furthermore, our studies of the steady states and their stability contribute to our understanding of various phenomena observed in experiments: void formation, hillock formation, hole induction and propagation, ligament formation and evolution, blistering prior to film rupture, etc. Importantly, our study shows that in order to relate theory with experiments, careful monitoring of spatial variations in the mean curvature in experiments is required.

Black hole initial data by numerical integration of the parabolic–hyperbolic form of the constraints

The parabolic–hyperbolic form of the constraints is integrated numerically. The applied numerical stencil is fourth-order accurate (in the spatial directions) while “time”-integration is made by using the method of lines with a fourth-order order accurate Runge–Kutta scheme. The proper implementation of the applied numerical method is verified by convergence tests and monitoring the relative and absolute errors is determined by comparing numerically and analytically known solutions of the constraints involving boosted and spinning vacuum single black hole configurations. The main part of our investigations is, however, centered on the construction of initial data for distorted black holes which, in certain cases, have non-negligible gravitational wave content. Remarkably, the applied new method is unprecedented in that it allows to construct initial data for highly boosted and spinning black holes, essentially for the full physical allowed ranges of these parameters. In addition, the use of the evolutionary form of the constraints is free from applying any sort of boundary conditions in the strong field regime.

Entanglement entropy of asymptotically flat non-extremal and extremal black holes with an island

The island rule for the entanglement entropy is applied to an eternal Reissner–Nordström black hole. The key ingredient is that the black hole is assumed to be in thermal equilibrium with a heat bath of an arbitrary temperature and so the generalized entropy is treated as being off-shell. Taking the on-shell condition to the off-shell generalized entropy, we find the generalized entropy and then obtain the entanglement entropy following the island rule. For the non-extremal black hole, the entanglement entropy grows linearly in time and can be saturated after the Page time as expected. The entanglement entropy also has a well-defined Schwarzschild limit. In the extremal black hole, the island prescription provides a logarithmically growing entanglement entropy in time and a constant entanglement entropy after the Page time. In the extremal black hole, the boundary of the island hits the curvature singularity where the semi-classical approximations appear invalid. To avoid encountering the curvature singularity, we apply this procedure to the Hayward black hole regular at the origin. Consequently, the presence of the island in extremal black holes can provide a finite entanglement entropy, which might imply non-trivial vacuum configurations of extremal black holes.

Many accelerating distorted black holes

An analytical solution of four-dimensional General Relativity, representing an array of collinear and accelerating black holes, is constructed with the inverse scattering method. The metric can be completely regularised from any conical singularity, thanks to the presence of an external gravitational field. Therefore the multi-black hole configuration can be maintained at equilibrium without the need of strings or struts. Some notable subcases such as the accelerating distorted Schwarzschild black hole and the distorted double C-metric are explicitly presented. The Smarr law and the thermodynamics of these systems is studied. The Bonnor–Swaminarayan and the Bičák–Hoenselaers–Schmidt particle metrics are recovered, through appropriate limits, from the multi-black holes solutions.

Rotating spacetimes generalizing Lifshitz black holes

We present a spinning black hole solution in d dimensions with a maximal number of rotation parameters in the context of the Einstein–Maxwell-Dilaton theory. An interesting feature of such a solution is that it accommodates Lifshitz black holes when the rotation parameters are set to zero. We verify the rotating nature of the black hole solution by performing the quasi-local analysis of conserved charges and defining the corresponding angular momenta. In addition, we perform the thermodynamical analysis of the black hole configuration, show that the first law of thermodynamics is completely consistent, and obtain a Smarr-like formula. We further study the thermodynamic stability of the constructed solution from a local viewpoint, by computing the associated specific heats, and from a global perspective, by using the so-called new thermodynamic geometry. We finally make some comments related to a pathology found in the causal structure of the obtained rotating black hole spacetime and compute some of its curvature invariants.

Isolation of flexural waves in a wide and low frequency range using a phononic beam with acoustic black hole configuration

We propose a phononic beam to realize flexural wave bandgaps in wide and low frequency regimes. A unit cell of the phononic beam consists of two uniform parts and a tapered part with acoustic black hole configuration sandwiched between uniform parts. We identify the effects of geometrical parameters of the ABH-based phononic beam on band structures and determine those geometrical parameters to obtain a bandgap from 3.6 Hz to 237.9 Hz with a lattice constant of 1/33 wavelength. For experimental realization, the displacement transmission of the phononic beam is measured by impact hammer test, and the result shows that low transmission of –35 dB to i–10 dB could be achieved in the wide bandgap.