Search

We study dynamic processes through which the scalar hair of black holes is generated or detached in a theory with a scalar field non-minimally coupled to Gauss-Bonnet and Ricci scalar invariants. We concentrate on the nonlinear temporal evolution of a far-from-equilibrium gravitational system. In our simulations, we choose the initial spacetime to be either a bald Schwarzschild or a scalarized spherically symmetric black hole. Succeeding continuous accretion of the scalar field onto the original black hole, the final fate of the system displays intriguing features, which depend on the initial configurations, strengths of the perturbation, and specific metric parameters. In addition to the scalarization process through which the bald black hole addresses scalar hair, we observe the dynamical descalarization, which removes scalar hair from an original hairy hole after continuous scalar field accretion. We examine the temporal evolution of the scalar field, the metrics, and the Misner-Sharp mass of the spacetime and exhibit rich phase structures through nonlinear dynamical processes., Comment: 25 pages, 12 figures

In the electromagnetic channel, chaotic gravitational lensing is a peculiar phenomenon in strong gravitational lensing. In this work, we analyze the properties and emergence of chaotic gravitational lensing in the Manko-Novikov black hole spacetime. Aiming to understand better the underlying physics, we elaborate on the boundaries of the accessible region in terms of the analyses of the contours of the effective potentials. The latter is associated with the two roots of a quadratic equation. In particular, we explore its interplay with ergoregion, which leads to specific features of the effective potentials, such as the emergence of cuspy edge and the formation of {\it pocket}, that serves as a static constraint on the geodesics. Besides, we investigate the properties of the radial and angular accelerations at the turning points in photons' trajectories. Moreover, the accelerations are analyzed, which is argued to provide a kinematic constraint on the geodesics. It is concluded that the onset of the chaotic lensing is crucially related to both constraints, and as a result, an arbitrarily slight deviation in the incident photon is significantly amplified during the course of evolution through an extensive period, demonstrating the complexity in the highly nonlinear deterministic gravitational system., Comment: 18 pages, 13 figures

In this study, we investigate the effect of nonlinear electrodynamics on the shadows of charged, slowly rotating black holes with the presence of a cosmological constant. Rather than the null geodesic of the background black hole spacetime, the trajectory of a photon, as a perturbation of the nonlinear electrodynamic field, is governed by an effective metric. The latter can be derived by analyzing the propagation of a discontinuity of the electromagnetic waveform. Subsequently, the image of the black hole and its shadow can be evaluated using the backward ray-tracing technique. We explore the properties of the resultant black hole shadows of two different scenarios of nonlinear electrodynamics, namely, the logarithmic and exponential forms. In particular, the effects of nonlinear electrodynamics on the optical image are investigated, as well as the image's dependence on other metric parameters, such as the black hole spin and charge. The resulting black hole image and shadow display rich features that potentially lead to observational implications.

By analyzing the propagation of discontinuity in nonlinear electrodynamics, we numerically investigate the related black hole shadows of recently derived rotating black hole solutions in gravity. In this context, the geodesic motion of the relevant perturbations is governed by an effective geometry, which is closely related to the underlying spacetime metric. We derive the effective geometry, and the latter is used to determine the trajectory of the propagation vector of an arbitrary finite discontinuity in the electrodynamic perturbations, namely, the photon. Subsequently, the image of the black hole is evaluated using the ray-tracing technique. Moreover, we discuss the physical relevance of metric parameters, such as the nonlinear coupling, spin, and charge, by studying their impact on the resultant black hole shadows.

In this paper, we study the quasinormal mode and late-time tail of charged massless scalar perturbations of a black hole in the generalized Rastall gravity. The black hole metric in question is spherically symmetric, accompanied by a power-Maxwell field surrounded by a quintessence fluid. It is shown that the massless scalar field, when {\it dressed up} with the magnetic field, acquires an effective mass which, in turn, significantly affects the properties of the resultant quasinormal oscillations and late-time tails. To be specific, the quasinormal frequencies become distorted and might even be unstable for particular spacetime configurations. Also, the exponent of the usual power-law tail is modified in accordance with the modification in the structure of the branch cut of the retarded Green's function. In particular, as the effective mass is generated dynamically due to the presence of the magnetic field, one may consider a process through which the field is gradually removed from the spacetime configuration. In this context, while the quasinormal oscillations converge to the case of massless perturbations, we argue that the properties of resultant late-time tails do not fall back to their massless counterpart. The relevant features are investigated by numerical and analytic approaches., Accepted for publication on CPC, doi: 10.1088/1674-1137/ac7855

Made available in DSpace on 2022-04-28T19:42:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-08-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) National Natural Science Foundation of China In this study, we investigate the Hawking radiation in higher dimensional Reissner-Nordström black holes as received by an observer located at infinity. The frequency-dependent transmission rates, which deform the thermal radiation emitted in the vicinity of the black hole horizon, are evaluated numerically. In addition to those in four-dimensional spacetime, the calculations are extended to higher dimensional Reissner-Nordström metrics, and the results are observed to be sensitive to the spacetime dimension to an extent. Generally, we observe that the transmission coefficient practically vanishes when the frequency of the emitted particle approaches zero. It increases with frequency and eventually saturates to a certain value. For four-dimensional spacetime, the above result is demonstrated to be mostly independent of the metric's parameter and the orbital quantum number of the particle, when the location of the event horizon, rh, and the product of the charges of the black hole and the particle qQ are known. However, for higher-dimensional scenarios, the convergence becomes more gradual. Moreover, the difference between states with different orbital quantum numbers is observed to be more significant. As the magnitude of the product of charges qQ becomes more significant, the transmission coefficient exceeds 1. In other words, the resultant spectral flux is amplified, which results in an accelerated process of black hole evaporation. The relationship of the calculated outgoing transmission coefficient with existing results on the greybody factor is discussed. Hubei Subsurface Multi-scale Imaging Key Laboratory Institute of Geophysics and Geomatics China University of Geosciences Escola de Engenharia de Lorena Universidade de São Paulo, SP Center for Gravitation and Cosmology College of Physical Science and Technology Yangzhou University Faculadade de Engenharia de Guaratinguetá Universidade Estadual Paulista, SP School of Physics and Technology Wuhan University Instituto de Física Universidade de São Paulo Faculadade de Engenharia de Guaratinguetá Universidade Estadual Paulista, SP National Natural Science Foundation of China: 11673008 National Natural Science Foundation of China: 11805166 National Natural Science Foundation of China: 11922303

In this work, we study the optical properties of a class of magnetically charged rotating black hole spacetimes. The black holes in question are assumed to be immersed in the quintessence field, and subsequently, the resulting black hole shadows are expected to be modified by the presence of dark energy. We investigate the photon region and the black hole shadow, especially their dependence on the relevant physical conditions, such as the quintessence state parameter, angular momentum, and magnetic charge magnitude. The photon regions depend sensitively on the horizon structure and possess intricate features. Moreover, from the viewpoint of a static observer, we explore a few observables, especially those associated with the distortion of the observed black hole shadows.

This study explores the scalar and Dirac quasinormal modes pertaining to a class of black hole solutions in the scalar-tensor-Gauss-Bonnet theory. The black hole metrics in question are novel analytic solutions recently derived in the extended version of the theory, which effectively follows at the level of the action of string theory. Owing to the existence of a nonlinear electromagnetic field, the black hole solution possesses a nonvanishing magnetic charge. In particular, the metric is capable of describing black holes with distinct characteristics by assuming different values of the ADM mass and the magnetic charge. This study investigates the scalar and Dirac perturbations in these black hole spacetimes; in particular, we focus on two different types of solutions, based on distinct horizon structures. The properties of the complex frequencies of the obtained dissipative oscillations are investigated, and the stability of the metric is subsequently addressed. We also elaborate on the possible implications of this study.

In the context of event-by-event hydrodynamic description, we analyze the implications of two models characterized by distinct initial conditions. The initial energy density of the first model adopts a Gaussian-type distribution, while those of the second one are features by high energy peripheral tubes. We calibrate the initial conditions of both models so that their initial probability distribution of eccentricity are mostly identical. Subsequently, the resultant scaled probability distributions of collective flow and the correlations between flow harmonic and eccentricity coefficients are investigated. Besides, the calculations are carried out for particle correlations regarding the symmetric cumulant, mixed harmonics, and nonlinear response coefficients. Although the resultant two-particle correlations possess similar shapes, numerical calculations indicate a subtle difference between the two models. To be specific, the difference resides in more detailed observables such as the probability distributions of elliptic flow as well as Pearson correlation coefficient regarding higher-order harmonics. We discuss several essential aspects concerning the linearity and nonlinearity between initial eccentricities and final state anisotropies. Further implications are addressed., 17 pages, 5 figures

As one of the possible signals for the whereabouts of the critical point on the QCD phase diagram, recently, the multiplicity fluctuations in heavy-ion collisions have aroused much attention. It is a crucial observable of the Beam Energy Scan program of the Relativistic Heavy Ion Collider. In this work, we investigate the centrality dependence of the multiplicity fluctuations regarding the recent measurements from STAR Collaboration. By employing a hydrodynamical approach, the present study is dedicated to the noncritical aspects of the phenomenon. To be specific, in addition to the thermal fluctuations, finite volume corrections, and resonance decay at the freeze-out surface, the model is focused on the properties of the hydrodynamic expansion of the system and the event-by-event initial fluctuations. It is understood that the real signal of the critical point can only be obtained after appropriately subtracting the background, the latter is investigated in the present work. Besides the experimental data, our results are also compared to those of the hadronic resonance gas, as well as transport models., 10 pages, 2 figures. arXiv admin note: text overlap with arXiv:1910.00705

We investigate the holographic p-wave superfluid in the background metric of the AdS soliton with $RF^{2}$ corrections. Two models, namely, the Maxwell complex vector field model and Yang-Mills theory, are studied in the above context by employing the Sturm-Liouville approach as well as the shooting method. When turning on the spatial components of the gauge field, one observes that, in the probe limit, the inclusion of $RF^{2}$ corrections hinders the superfluid phase transition. On the other hand, however, in the absence of the superfluid velocity, it is found that the $RF^2$ corrections lead to distinct effects for the two models. Regardless of either the $RF^2$ correction or the spatial component of the gauge field, the phase transition of the system is observed to be always of the second order. Moreover, a linear relationship between the charge density and chemical potential is largely established near the critical point in both holographic superfluid models., 20 pages, 2 figures, 3 tables

In this paper, we study the quasinormal modes of the massless Dirac field for charged black holes in Rastall gravity. The spherically symmetric black hole solutions in question are characterized by the presence of a power-Maxwell field, surrounded by the quintessence fluid. The calculations are carried out by employing the WKB approximations up to the thirteenth order, as well as the matrix method. The temporal evolution of the quasinormal modes is investigated by using the finite difference method. Through numerical simulations, the properties of the quasinormal frequencies are analyzed, including those for the extremal black holes. Among others, we explore the case of a second type of extremal black holes regarding the Nariai solution, where the cosmical and event horizon coincide. The results obtained by the WKB approaches are found to be mostly consistent with those by the matrix method. It is demonstrated that the black hole solutions for Rastall gravity in asymptotically flat spacetimes are equivalent to those in Einstein gravity, featured by different asymptotical spacetime properties. As one of its possible consequences, we also investigate the behavior of the late-time tails of quasinormal models in the present model. It is found that the asymptotical behavior of the late-time tails of quasinormal modes in Rastall theory is governed by the asymptotical properties of the spacetimes of their counterparts in Einstein gravity., Comment: 19 pages, 6 figures, and 2 tables

We study the properties of the p-wave holographic superconductor for the scalar hairy black holes in the probe limit. The black hole solutions in question possess planar topology, which are derived from the Einstein gravity theory minimally coupled to a scalar field with a generic scalar potential. These solutions can be viewed as characterized by two independent parameters, namely, $\alpha$ and $k_0$, where AdS vacuum is manifestly restored when $\alpha\to \infty$. Consequently, the p-wave holographic superconductor is investigated by employing the above static planar black hole spacetime as the background metric, where a Maxwell field is introduced to the model by nonminimally coupling it to a complex vector field. The latter is shown to condensate and furnish the superconducting phase when the temperature is below a critical value. By numerical calculations, we examine in detail how the scalar field in the background affects the properties of the superconductivity. It is found that the critical temperature depends crucially on the parameters $\alpha$ and $k_0$, which subsequently affects the condensation process. By employing the Kubo formula, the real, as well as imaginary parts of the conductivity, are calculated and presented as functions of frequency. The results are discussed regarding the poles of the Green function, and the typical values of the BCS theory., Comment: 15 pages, 6 figures

Made available in DSpace on 2019-10-04T12:14:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-08-01 National Natural Science Foundation of China (NNSFC) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) We investigate the static, spherically symmetric regular black hole solutions in the generalized Rastall gravity. In particular, the prescription of Rastall gravity implies that the present approach does not necessarily involve nonlinear electrodynamics. Subsequently, the resulting regular black hole solutions can be electrically and magnetically neutral. The general properties of the regular black hole solutions are explored. Moreover, specific solutions are derived and discussed, particularly regarding the parameter related to the degree of violation of the energy-momentum conservation in the Rastall theory. China Univ Geosci, Hubei Subsurface Multiscale Imaging Key Lab, Inst Geophys & Geomat, Wuhan 430074, Hubei, Peoples R China Univ Sao Paulo, Escola Engn Lorena, BR-12602810 Lorena, SP, Brazil Univ Estadual Paulista, Fac Engn Guaratingueta, BR-12516410 Guaratingueta, SP, Brazil Yangzhou Univ, Ctr Gravitat & Cosmol, Coll Phys Sci & Technol, Yangzhou 225009, Jiangsu, Peoples R China Univ Estadual Paulista, Fac Engn Guaratingueta, BR-12516410 Guaratingueta, SP, Brazil National Natural Science Foundation of China (NNSFC): 11805166

In this work, we study the two-particle correlations regarding a peripheral tube model. From our perspective, the main characteristics of the observed two-particle correlations are attributed to the multiplicity fluctuations and the locally disturbed one-particle distribution associated with hydrodynamic response to the geometric fluctuations in the initial conditions. We investigate the properties of the initial conditions and collective flow concerning the proposed model. It is shown that the experimental data can be reproduced by hydrodynamical simulations using appropriately constructed initial conditions. Besides, instead of numerical calibration, we extract the model parameters according to their respective physical interpretations and show that the obtained numerical values are indeed qualitatively in agreement with the observed data. Possible implications of the present approach are discussed., 11 pages, 4 figures

Phosphorylurea molecules, which contain both phosphoryl and carbonyl groups, are considered efficient extractants for UO22+. This study aims to explain the complexation of UO22+ with carbamoylphosphoramidic acid (CPO), a simple model for phosphorylurea, for ligand design for uranium recovery from seawater using density functional theory calculations, natural bond order analysis, and the quantum theory of atoms in molecules. The results showed that, when CPO acts as a monodentate ligand, the affinity of phosphoryl for UO22+ is stronger than that of carbonyl, and CPO coordinates with UO22+ through the phosphoryl oxygen atom. When CPO serves as a bidentate ligand, both the phosphoryl and carbonyl oxygen atoms connect to UO22+, and the U–O(carbonyl) bond plays a more important role than the U–O(phosphoryl) bond in the interaction between UO22+ and CPO. This paradox may be caused by the significant charge transfer from the U–O(carbonyl) π bond orbital to the C–N σ antibond orbital of the bidentate CPO. The NH spacer between the phosphoryl and carbonyl groups could ensure the delocalization of the electron system of the molecule. The bidentate binding motif is favored by entropy and opposed by enthalpy, while the monodentate binding motif is favored by enthalpy and opposed by entropy. Ultimately, the bidentate binding motif is more favorable than the monodentate one. As expected, the interaction between UO22+ and the deprotonated CPO is stronger than that between UO22+ and the neutral CPO. Comparing the interaction between UO22+ and CPO with that between UO22+ and N-phenylcarbamoylphosphoramidic acid (PhCPO), formed by replacing one hydrogen atom from the terminal nitrogen atom of CPO with a phenyl group, the phenyl substituent at the terminal nitrogen atom of PhCPO shows a slightly negative effect on the interaction between UO22+ and PhCPO.

We study the p-wave holographic superconductor for AdS black holes with planar event horizon topology for a particular Lovelock gravity, in which the action is characterized by a self-interacting scalar field nonminimally coupled to the gravity theory which is labeled by an integer $k$. As the Lovelock theory of gravity is the most general metric theory of gravity based on the fundamental assumptions of general relativity, it is a desirable theory to describe the higher dimensional spacetime geometry. The present work is devoted to studying the properties of the p-wave holographic superconductor by including a Maxwell field which nonminimally couples to a complex vector field in a higher dimensional background metric. In the probe limit, we find that the critical temperature decreases with the increase of the index $k$ of the background black hole metric, which shows that a larger $k$ makes it harder for the condensation to form. We also observe that the index $k$ affects the conductivity and the gap frequency of the holographic superconductors., Comment: 14 pages, 6 figures

In this work, we study the centrality as well as transverse momentum dependence of the dihadron correlation for Au+Au collisions at 200A GeV. The numerical simulations are carried out by using a hydrodynamical code NeXSPheRIO, where the initial conditions are obtained from a Regge-Gribov based microscopic model, NeXuS. In our calculations, the centrality windows are evaluated regarding multiplicity. The final correlations are obtained by the background subtraction via ZYAM methods, where higher harmonics are also considered explicitly. The correlations are evaluated for the 0 - 20\%, 20\%-40\% and 60\%-92\% centrality windows. Also, the transverse momentum dependence of the dihadron correlations is investigated. The obtained results are compared with experimental data. It is observed that the centrality dependence of the "ridge" and "double shoulder" structures is in consistency with the data. Based on specific set of parameters employed in the present study, it is found that different ZYAM subtraction schemes might lead to different features in the resultant correlations., Comment: 11 pages, 5 figures

In this work, a hydrodynamic study of the di-hadron azimuthal correlations for the Au+Au collisions at 200 GeV is carried out. The correlations are evaluated using the ZYAM method for the centrality windows as well as the transverse momentum range in accordance with the existing data. Event-plane dependence of the correlation is obtained after the subtraction of contributions from the most dominant harmonic coefficients. In particular, the contribution from the triangular flow, $v_3$, is removed from the proper correlations following the procedure implemented by the STAR collaboration. The resultant structure observed in the correlations was sometimes attributed to the mini-jet dynamics, but the present calculations show that a pure hydrodynamic model gives a reasonable agreement with the main feature of the published data. A brief discussion on the physical content of the present findings is presented., Comment: 9 pages, 2 figures

In this letter, a matrix method is employed to study the scalar quasinormal modes of Kerr as well as Kerr-Sen black holes. Discretization is applied to transfer the scalar perturbation equation into a matrix form eigenvalue problem, where the resulting radial and angular equations are derived by the method of separation of variables. The eigenvalues, quasinormal frequencies $\omega$ and angular quantum numbers $\lambda$, are then obtained by numerically solving the resultant homogeneous matrix equation. This work shows that the present approach is an accurate as well as efficient method for investigating quasinormal modes., Comment: The Mathematica programs are attached in the ancillary files on the arXiv server

Made available in DSpace on 2018-11-26T15:43:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-01-01 Natural Science Foundation of China Fundamental Research Funds for the Central Universities Chongqing Postdoctoral Science Foundation Open Project Program of State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Chinese State Scholarship We investigate the gravitational quasinormal modes (QNMs) for a type of regular black hole (BH) known as phantom BH, which is a static self-gravitating solution of a minimally coupled phantom scalar field with a potential. The studies are carried out for three different spacetimes: asymptotically flat, de Sitter (dS), and anti-de Sitter (AdS). In order to consider the standard odd parity and even parity of gravitational perturbations, the corresponding master equations are derived. The QNMs are discussed by evaluating the temporal evolution of the perturbation field which, in turn, provides direct information on the stability of BH spacetime. It is found that in asymptotically flat, dS, and AdS spacetimes the gravitational perturbations have similar characteristics for both odd and even parities. The decay rate of perturbation is strongly dependent on the scale parameter.., which measures the coupling strength between phantom scalar field and the gravity. Furthermore, through the analysis of Hawking radiation, it is shown that the thermodynamics of such regular phantom BH is also influenced by b. The obtained results might shed some light on the quantum interpretation of QNM perturbation. Chongqing Univ, Coll Phys, Chongqing 401331, Peoples R China Chinese Acad Sci, Inst Theoret Phys, State Key Lab Theoret Phys, Beijing 100190, Peoples R China Univ Fed Itajuba, Inst Fis & Quim, BR-37500903 Itajuba, MG, Brazil China West Normal Univ, Dept Astron, Nanchong 637002, Sichuan, Peoples R China Univ Sao Paulo, Escola Engn Lorena, Sao Paulo, SP, Brazil Univ Estadual Paulista, Fac Engn Guaratingueta, Guaratingueta, SP, Brazil Univ Estadual Paulista, Fac Engn Guaratingueta, Guaratingueta, SP, Brazil Natural Science Foundation of China: 11205254 Natural Science Foundation of China: 11178018 Natural Science Foundation of China: 11573022 Natural Science Foundation of China: 11605015 Natural Science Foundation of China: 11375279 Fundamental Research Funds for the Central Universities: 106112016CDJXY300002 Fundamental Research Funds for the Central Universities: 106112015CDJRC131216 Chongqing Postdoctoral Science Foundation: Xm2015027 Open Project Program of State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China: Y5KF181CJ1

A novel phase shifter used to adjust the output phase of high-power microwave (HPM) is investigated. It is noticed that the waveguide wavelength and propagation constant of the TE10 mode are functions of the wide side dimension of the rectangular waveguide, and therefore the output phase of the microwave can be adjusted by changing the wide side dimension. In this paper, an HPM waveguide phase shifter with the wide side dimension adjustable is designed and analyzed numerically. No dielectric or metal pins are involved in this phase shifter, and the microwave propagates in the TE10 mode. In addition, it has a high power-handling capacity. Results show that the phase shifter could operate at a frequency of 15.2 GHz, and the phase of the wave can be adjustable in a range of 0 °-360 ° with a transmit efficiency over 96%. The dimensions of the phase shifter are 13.8 mm × 7.9 mm with a phase shifting length of 139 mm. This novel phase shifter is of interest to HPM applications and higher microwave band.

In this paper, a compact rep-rate GW pulsed power generator is developed. First, its three key subsystems are theoretically analyzed, engineering designed, and experimentally investigated, respectively. The emphases are put on these four problems: the theoretical analysis of the voltage distribution across the conical secondary windings of the high-coupling transformer, the investigation of the high energy storage density dielectric used in the pulse forming line, the choice of the gas flow velocity of the gas blowing system, and theoretical analysis of the passive stability of the pulsed power generator operated in rep-rate mode. Second, the developed pulsed power generator is described in detail. It has a 0.2-m diameter, a 1.0-m length, and a 20- Ω wave impedance. Across a 100- Ω resistive dummy load, it can steadily operate at a 300-kV output voltage in 50-Hz rep-rate and 250 kV in 150 Hz without gas blowing system. The average power is ~ 1 kW. Finally, the pulsed power generator is applied to drive a relativistic backward-wave oscillator, generating a high-power microwave with peak output power of 200 MW and duration (full-width at half-maximum) of 5 ns in 150-Hz rep-rate. These efforts set a good foundation for the development of a compact rep-rate pulsed power generator and show a promising application for the future.

Made available in DSpace on 2019-10-04T11:57:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-03-01 National Natural Science Foundation of China (NNSFC) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) We provide a comprehensive survey of possible applications of the matrix method for black hole quasinormal modes. The proposed algorithm can generally be applied to various background metrics, and in particular, it accommodates both analytic and numerical forms of the tortoise coordinates, as well as black hole spacetimes. We give a detailed account of different types of black hole metrics, master equations, and corresponding boundary conditions. Besides, we argue that the method can readily be applied to cases where the master equation is a system of coupled equations. By adjusting the number of interpolation points, the present method provides a desirable degree of precision, in reasonable balance with its efficiency. The method is flexible and can easily be adopted to various distinct physical scenarios. China Univ Geosci, Inst Geophys & Geomat, Hubei Subsurface Multiscale Imaging Key Lab, Wuhan 430074, Hubei, Peoples R China Univ Sao Paulo, Escola Engn Lorena, BR-12602810 Lorena, SP, Brazil Univ Estadual Paulista, Fac Engn Guaratingueta, BR-12516410 Guaratingueta, SP, Brazil Yangzhou Univ, Sch Phys Sci & Technol, Yangzhou 225002, Jiangsu, Peoples R China Univ Estadual Paulista, Fac Engn Guaratingueta, BR-12516410 Guaratingueta, SP, Brazil National Natural Science Foundation of China (NNSFC): 11805166

With the development of narrow-band high-power-microwave (HPM) technology, air breakdown has become a serious problem that concerns to the HPM applications. A new method is presented in this paper to determine the electric field of the microwave air breakdown near the atmosphere pressures. Two metal pins were used to strengthen the microwave electric field in a sealed waveguide, putting on the symmetry axis. Some parameters such as gas pressure, temperature, and humidity could be changed conveniently to achieve gas breakdown. Experiment was carried out at the S-band (2.86-GHz) microwave of 180-ns duration and 5-MW peak power, and typical phenomena of plasmas introduced by microwave are analyzed. Furthermore, a new definition of breakdown threshold has been proposed based on breakdown probability, and the electric field threshold is also analyzed.

Experiments on the surface flashover under 180-ns quasi-square waves with voltage of several hundred kilovolts are reported. In the experiments, employing a 280-kV 180-ns full-width at half-maximum (FWHM) voltage on the load, no flashover occurred. When the voltage was up to 350 kV, even 420 kV, surface flashover along the insulator occurred, and it started at the top part of the applied voltage pulse, so the FWHM of the output voltage of pulse generator was reduced to 150 ns, even 120 ns. Also, the experiment results show that surface flashover channel could be recovered quickly if a heteropolarity voltage was applied on the flashover channel. Finally, the characteristics of the surface flashover are present, including the flashover time, flashover current, and resistance.

Recent experimental results of three kinds of long-pulse high-power microwave (HPM) sources operating in S-, C-, and X-bands are reported. The difficulties in producing a long-pulse HPM for the O-type Cerenkov HPM source were analyzed theoretically. In S- and C-bands, single-mode relativistic backward-wave oscillators were designed to achieve long-pulse HPM outputs; in X-band, because of its shorter wavelength, an O-type Cerenkov HPM source with overmoded slow-wave systems was designed to increase power capacity. In experiments, driven by a repetitive long-pulse accelerator, both S- and C-band sources generated HPMs with power of about 2 GW and pulse duration of about 100 ns in single-shot mode, and the S-band source operated stably with output power of 1.2 GW in 20-Hz repetition mode. The X-band source generated 2 GW microwaves power with pulse duration of 80 ns in the single-shot mode and 1.2 GW microwave power with pulse duration of about 100 ns in the 20-Hz repetition mode. The experiments show good performances of the O-type Cerenkov HPM source in generating repetitive long-pulse HPMs, especially in S- and C-bands. It was suggested that explosive emissions on surfaces of designed eletrodynamic structures restrained pulse duration and operation stability.

Event-by-event hydrodynamics (or hydrodynamics with fluctuating initial conditions) has been developed in the past few years. Here we discuss how it may help to understand the various structures observed in two-particle correlations., Comment: 7 pages, 9 figures, presented at the Workshop on Saturation, the Color Glass Condensate and Glasma: What Have we Learned from RHIC?

In this work, the s-wave, p-wave and d-wave holographic superconductors in the Ho\v{r}ava-Lifshitz gravity are investigated in the probe limit. For the present approach, it is shown that the equations of motion for different wave states in Einstein gravity can be written into a unified form, and condensates take place in all three cases. This scheme is then generalized to Ho\v{r}ava-Lifshitz gravity, and an unified equation for multiple holographic states is obtained. Furthermore, the properties of the condensation and the optical conductivity are studied numerically. It is found that, in the case of Ho\v{r}ava-Lifshitz gravity, it is always possible to find some particular parameters in the corresponding Einstein case where the condensation curves are identical. For fixed scalar field mass $m$, a non-vanishing $\alpha$ becomes the condensation easier than in Einstein gravity for s-wave superconductor. However, the p-wave and d-wave superconductors have $T_c$ greater than s-wave one., Comment: published version

We perform an extensive study of the role played by the equation of state (EoS) in the hydrodynamic evolution of the matter produced in relativistic heavy ion collisions. By using the same initial conditions and freeze-out scenario, the effects of different equations of state are compared by calculating their respective hydrodynamical evolution, particle spectra, harmonic flow coefficients [Formula: see text], [Formula: see text] and [Formula: see text] and two-pion interferometry radius parameters. The equations of state investigated contain distinct features, such as the nature of the phase transition, as well as strangeness and baryon density contents, which are expected to lead to different hydrodynamic responses. The results of our calculations are compared to the data recorded at two RHIC energies, 130[Formula: see text]GeV and 200[Formula: see text]GeV. The three equations of state used in the calculations are found to describe the data reasonably well. Differences can be observed among the studied observables, but they are quite small. In particular, the collective flow parameters are found not to be sensitive to the choice of the EOS, whose implications are discussed.

This paper discusses the development and testing of a low-jitter, high-voltage, high-current, and triggered spark-gap switch, designed as part of an intense electron-beam accelerator (IEBA). The voltage/pressure (V/p) curve of the switch was measured for N2 when the gas pressure is 0.10-0.25 MPa with the main gap spacing of 10 mm. In addition, the operating ranges, delay time, and jitter of the switch were measured during the single trigger experiment when the gas pressures were 0.10, 0.15, 0.20, and 0.25 MPa and the trigger voltage was 80 kV. The experimental results showed that the operating ranges of the switch were 25%-94%, 38%-86%, 40%-88%, and 44%-88% of the switch's self-breakdown voltage, and these results also identified a suitable operating condition for the application of the switch on the IEBA. When the gas pressure was 0.25 MPa, the operating voltage was 40 kV, which was about 88% of the self-breakdown voltage, the delay time was 50 ns, and jitter was 1.28 ns. At last, the repetition rate of the switch was measured when the switch was used as the trigger switch of the IEBA. The pulse repetition rate (PRR) is 10 Hz at the operating voltage of 20 kV and peak currents of 40 kA. The PRR is 5 Hz at the operating voltage of up to 40 kV and the peak currents of up to 80 kA. The switch works steadily and reliably.

In this paper, the surface creepage of high-voltage self-breakdown switch which is used in 500 kV pulse modulator is analyzed in theory by employing the method of distributed element equivalent recurrent circuit. Moreover, the field distortion of the connecting ring of the switch is simulated by using software. According to the theoretical analysis, several methods to avoid surface creepage are obtained: 1) the outer housing of the switch should have high surface resistivity; 2) when the surface breakdown electric field is a constant, it is better to decrease the diameter of the electrode and to increase outer diameter and thickness of the outer housing; 3) in order to avoid field distortion, it is recommended, as far as possible, not to use metal connecting ring on the outer housing of the switch; and 4) there should be a clean environment for switch to work.

We investigate the effect of chemical freeze-out on identified particle spectra at 200AGeV Au-Au Collisions at RHIC, by utilizing a full three-dimensional hydrodynamical calculation. The hydrodynamical code SPheRIO we employed is based on the smoothed particle hydrodynamic algorithm. In order to describe the spectra of strange hadrons, the code has been further improved by explicitly incorporating the strangeness conservation and a chemical freeze-out mechanism. In our model, strange hadrons such as Lambda, Xi, Omega and phi undergo the chemical freeze-out immediately after the hadronization, and their multiplicities are fixed thereafter. At a lower temperature the thermal freeze-out takes place for all the particles. It is shown that the present model provides a reasonably good description for the spectra of identified particles, in particular, considerable improvement is observed for those of strange hadrons., Comment: 6 pages, 4 figures

The improved quark mass density-dependent model, which is able to provide a good description for the properties of both finite nuclei and bulk nuclear matter, is employed to investigate the properties of several possible light kaonic nuclei. The current approach is based on an extended version of the relativistic mean-field theory, where the kaon-nucleon and nucleon-nucleon interactions are treated on the same footing. In this work, the single K--nuclear states in the possible bubble nuclei are studied, with concentration on the experimentally accessible light nuclei. The K- binding energies, the decay widths, single-particle spectra, and nuclear and K- density distributions are evaluated. The calculations indicate that, when the K- meson is embedded in nuclei with speculated "bubble" structure, the depleted central nuclear density might be modified, and in certain cases, the bubble structure may even disappear. Furthermore, it is found that the properties of the kaonic nuclei are sensitive to the strength of the antikaon optical potential at saturation density.

A two-components isospin lattice gas model has been employed to study the liquid-gas phase transition for asymmetric nuclear matter. An additional degree of freedom, namely, the asymmetry parameter alpha has been considered carefully for studying the phase transition. We have shown that under the mean field approximation, the liquid-gas phase transition given by this model is of second order. The entropy continues at the phase transition point. The binodal surface is addressed., 7 pages, 4 figures

In a study of the liquid-gas phase transition in warm asymmetric nuclear matter by means of the FST model, a density-dependent nucleon-nucleon-rho-meson (NNrho) coupling is introduced. It is found that the density dependence of the effective (NNrho) coupling makes the phase transition more complicated than the constant coupling case which is usually assumed. The section of the binodal surface at a fixed temperature may be cut off at a pressure limit p(lim), above which there is no two-phase coexistence. A second-order phase transition taking place in asymmetric nuclear matter below its pressure limit changes to a first-order transition at the pressure limit.

By means of the Furnstahl, Serot and Tang's model, the effects of surface tension and Coulomb interaction on the liquid-gas phase transition for finite nuclei are investigated. A limit pressure p-lim above which the liquid-gas phase transition cannot take place has been found. It is found that comparing to the Coulomb interaction, the contribution of surface tension is dominate in low temperature regions. The binodal surface is also addressed., Comment: LaTex, 8 pages with 6 figs

The density of states for an extended MIT bag model is studied numerically by using a parameterized smooth representation which provides the best fit to the numerical data. It is found that the mass dependence of the surface term in the density of states agrees with that derived from multi-reflection theory calculation. The mass dependence of the curvature term in the density of states is extracted for finite values of the quark mass. The scaling properties of the data, assumed in the parameterization, are studied. The difference between the parameterized smooth representation determined by a best fit and the results derived from direct smoothing of the numerical data are discussed. The fluctuations in the density of states are also discussed. We provide a smooth representation of the density of states of a spherical cavity for non-relativistic particles., 9 pages 4 figures. to be published on Jour. Phys. G

In this work, a new quark-meson coupling model is employed to study the ground-state properties of axially deformed even-even nuclei. Two essential ingredients, namely, density dependence of quark mass and tensor coupling, play important roles in our approach. In particular, it is the first time that the deformed quark-meson coupling calculation with tensor coupling is applied to study the properties of finite nuclei. The present work involves a systematical study of nuclei ranging from Z = 50 to Z = 82 . The ground-state binding energies, quadrupole deformations, shape coexistence, two-neutron separation energies and the root-mean-square charge radii are calculated and compared with the experimental data. It is shown that the ground-state properties of the deformed nuclei are reasonably well reproduced by a model based on the sub-hadronic degrees of freedom.

This paper presents a two-dimensional model for studying the relativistic parapotential electron flow in a magnetically insulated transmission line oscillator (MILO). The distribution expressions of the velocity, energy, density, and self-electric and self-magnetic fields of electron flow are derived and then analyzed numerically. Results of the model show that the self-electric and self-magnetic fields and density of the electron flow are quite high near the surface of the slow-wave structure of a MILO where they may reach their peak values. In addition, the formation of the insulated electron flow requires a large current flowing through the inner conductor (cathode) of the MILO, which is identical with the previous works. It is also found that considerable increases in the absolute values of axial and radial velocities of the electron flow occur when electrons approach the surface of the slow-wave structure. The electron flow is mainly along the axial direction in between the surfaces of cathode and slow-wave structure except the regions near the two surfaces. More interestingly, the radial velocity of electron flow ran still be increased but the axial velocity decreased when the electrons go into the region in between the inner and outer radii of the slow-wave structure, where the electron flow is not always dominated by axial flow. The results of the present paper are more realistic than those of the one-dimensional model in describing the parapotential electron flow in a MILO.

An exact solution is found for the relativistic equation of motion of a charged particle driven by a circularly polarized electromagnetic wave and a constant magnetic field. The explicit expressions of particle position and velocity are obtained for certain initial conditions. The results are of interest to the interaction of the high-power laser with the magnetized plasma, electromagnetically pumped free-electron laser with a guide magnetic field, propagation of electromagnetic wave signals through a re-entry plasma sheath in the presence of a strong magnetic field, and magnetic confinement plasmas.

Collective flow observed in heavy ion collisions is largely attributed to initial geometrical fluctuations, and it is the hydrodynamic evolution of the system that transforms those initial spatial irregularities into final state momentum anisotropies. Cumulant analysis provides a mathematical tool to decompose those initial fluctuations in terms of radial and azimuthal components. It is usually thought that a specified order of azimuthal cumulant, for the most part, linearly produces flow harmonic of the same order. In this work, we carry out a systematic study on the connection between cumulants and flow harmonics using a hydrodynamic code called NeXSPheRIO. We conduct three types of calculations, by explicitly decomposing the initial conditions into components corresponding to a given eccentricity and studying the out-coming flow through hydrodynamic evolution. It is found that for initial conditions deviating significantly from Gaussian, such as those from NeXuS, the linearity between eccentricities and flow harmonics partially breaks down. Combining with the effect of coupling between cumulants of different orders, it causes the production of extra flow harmonics of higher orders. We argue that these results can be seen as a natural consequence of the non-linear nature of hydrodynamics, and they can be understood intuitively in terms of the peripheral-tube model., 19 pages, 11 figures

The STAR Collaboration reported measurements of di-hadron azimuthal correlations in medium-central Au+Au collisions at 200$A$ GeV, where the data are presented as a function of the trigger particle's azimuthal angle relative to the event plane ${\ensuremath{\phi}}_{s}$. In particular, it is observed that the away-side correlation evolves from a single- to a double-peak structure with increasing ${\ensuremath{\phi}}_{s}$. In this work, we present the calculated correlations as functions of both ${\ensuremath{\phi}}_{s}$ and the particle transverse momentum ${p}_{T}$, using the hydrodynamic code NeXSPheRIO. The results are found to be in reasonable agreement with the STAR data. We further argue that the above ${\ensuremath{\phi}}_{s}$ dependence of the correlation structure can be understood in terms of the one-tube model, as due to an interplay between the background elliptic flow caused by the initial state global geometry and the flow produced by fluctuations.

In this work, we study the quark energy spectrum in an MIT bag using the quark-meson coupling model. In particular, thermal distribution functions of quarks at finite temperature are explicitly incorporated into the calculations. It is found that when temperature is less than 50 MeV, the probability for a quark to occupy an exciting state is very rare and negligible, therefore the corresponding contributions to the thermodynamic potential undermean-field theory are strongly suppressed. In this context, if one calculates other physical quantities derived from thermodynamic potential, effects due to quark distribution functions are also likely to be unimportant. DOI: 10.1103/PhysRevC.86.068201

A unified description of the near-side and away-side structures observed in two-particle correlations as function of delta eta-delta phi is proposed for low to moderate transverse momentum. It is based on the combined effect of tubular initial conditions and hydrodynamical expansion., 4 pages, 3 figures. Contribution to QM2011

The aim of this work is to clarify the origin of the in-plane/out-of-plane effect, in the two-particle correlation function, computed with the NexSPheRIO code, in Au + Au collisions at 200 AGeV. We show that such an effect can be understood in terms of the shadowing effect caused by a peripheral high-energydensity tube.

The Blumlein pulse forming line (BPFL) consisting of an inner coaxial pulse forming line (PFL) and an outer coaxial PFL is widely used in the field of pulsed power, especially for intense electron-beam accelerators (IEBA). The output voltage waveform determines the quality and characteristics of the output beam current of the IEBA. Comparing with the conventional BPFL, an IEBA based on a helical type BPFL can increase the duration of the output voltage in the same geometrical volume. However, for the helical type BPFL, the voltage waveform on a matched load may be distorted which influences the electron-beam quality. In this paper, an IEBA based on helical type BPFL is studied theoretically. Based on telegrapher equations of the BPFL, a formula for the output voltage of IEBA is obtained when the transition section is taken into account, where the transition section is between the middle cylinder of BPFL and the load. From the theoretical analysis, it is found that the wave impedance and transit time of the transition section influence considerably the main pulse voltage waveform at the load, a step is formed in front of the main pulse, and a sharp spike is also formed at the end of the main pulse. In order to get a well-shaped square waveform at the load and to improve the electron-beam quality of such an accelerator, the wave impedance of the transition section should be equal to that of the inner PFL of helical type BPFL and the transit time of the transition section should be designed as short as possible. Experiments performed on an IEBA with the helical type BPFL show reasonable agreement with theoretical analysis.

Relativistic nuclear collisions data on two-particle correlations exhibit structures as function of relative azimuthal angle and rapidity. A unified description of these near-side and away-side structures is proposed for low to moderate transverse momentum. It is based on the combined effect of tubular initial conditions and hydrodynamical expansion. Contrary to expectations, the hydrodynamics solution shows that the high energy density tubes (leftover from the initial particle interactions) give rise to particle emission in two directions and this is what leads to the various structures. This description is sensitive to some of the initial tube parameters and may provide a probe of the strong interaction. This explanation is compared with an alternative one where some triangularity in the initial conditions is assumed. A possible experimental test is suggested., Comment: 6 pages, 6 figures

The flat voltage of the main pulse on the load of intense electron-beam accelerators (IEBA) is one of the important factors which affect the quality and characteristic of the output beam current of IEBA. In this paper, the effect of the transition section between the Blumlein pulse forming line (BPFL) and load on the output voltage of IEBA is analyzed in theory. Based on the telegraph equations of the BPFL, a formula which is used to calculate the output voltage of IEBA is obtained, and the factor which affects the output voltage is analyzed. It is found from the theoretical analysis that the wave impedance and transmission time of the transition section influence considerably the fluctuation of the main pulse voltage waveform at the load. In order to get a well-shaped square waveform at load and to improve the electron-beam quality of such an accelerator, there should be a proper wave impedance of the transition section, and the transmission time of the transition section should be designed as short as possible. At last, some experiments are performed on IEBA, and the experimental results show reasonable agreement with theoretical analysis.

We present an improved quark mass density-dependent model with the nonlinear scalar sigma field and the {omega}-meson field. By comparing with the quark-meson coupling model, we show that our model can successfully describe saturation properties, the equation of state, the compressibility and the effective nuclear mass of nuclear matter under the mean field approximation.