Holographic Schwinger effect in spinning black hole backgrounds

We perform a potential analysis for the holographic Schwinger effect in spinning Myers-Perry black holes.We compute the potential between the produced pair by evaluating the classical action of a string attached on a probe D3-brane at an intermediate position in the AdS bulk.We find that increasing the angular momentum reduces the potential barrier,thus enhancing the Schwinger effect,consistent with previous findings obtained via the local Lorentz transformation.In particular,these effects are more visible for the particle pair lying in the transversal plane compared with that along the longitudinal orientation.In addition,we discuss how the Schwinger effect changes with the shear viscosity to entropy density ratio at strong coupling under the influence of angular momentum.

Holographic Schwinger effect in an anisotropic background with Gauss-Bonnet corrections

Using the anti-de Sitter/conformal field theory(AdS/CFT)correspondence,we study the holographic Schwinger effect in an anisotropic background with the Gauss-Bonnet term.As the background geometry is anisotropic,we consider both cases of the test particle pair and the electric field perpendicular to and parallel to the anisotropic direction.It is shown that the Schwinger effect is enhanced in the perpendicular case when anisotropy rises.In the parallel case,this effect is reversed.Additionally,the potential barrier and the critical electric field in the parallel case are more significantly modified by anisotropy compared to the perpendicular case.We also find that the presence of the Gauss-Bonnet coupling tends to increase the Schwinger effect.

R^4 corrections to holographic Schwinger effect

We consider R^4 corrections to the holographic Schwinger effect in an AdS black hole background and a confining D3-brane background. The potential between a test particle pair are performed for both backgrounds. We find there is no potential barrier ill the critical electric field, which means that the system becomes catastrophically unstable. It is shown that for both backgrounds, increasing the inverse ＇t Hooft coupling parameter 1/λ enhances the Schwinger effect. We also discuss the possible relation between the Schwinger effect and the viscosity-entropy ratio η/s in strong coupling.

Holographic Schwinger effect in a rotating strongly coupled medium

We perform a potential analysis on the holographic Schwinger effect in a rotating deformed AdS blackhole background.We calculate the total potential of a quark-antiquark(QQ)pair in an external electric field and evaluate the critical electric field from Dirac-Born-Infeld action.It is shown that the inclusion of angular velocity decreases the potential barrier,thus enhancing the Schwinger effect,which contrasts with the effect of the confining scale.Moreover,increasing the angular velocity decreases the critical electric field,above which these pairs are produced freely without suppression.Furthermore,we conclude that QQ pair production would be easier in a rotating medium.

A comparison of condensate mass of QCD vacuum between Wilson line approach and Schwinger effect

We studied the condensate mass of QCD vacuum through the duality approach via dilaton wall back-ground in the presence of the parameter c,which represents the condensation in a holographic set up.First,fromWilson line calculation,we found m_(0)^(2)(i.e.,the condensate parameter in mixed non-local condensation),whose beha-vior mimics that of QCD.The value of m_(0)^(2)that we found by this approach is in agreement with QCD data.Second we considered the produced mass m via the Schwinger effect mechanism in the presence of the parameter c.We show that vacuum condensation generally contributes the mass dominantly and that the produced mass via Schwing.er effect is suppressed by m_(0).

Holographic Schwinger effect in a soft wall AdS/QCD model

We perform a potential analysis for the holographic Schwinger effect in a deformed AdS5 model with conformal invariance broken by a background dilaton.We evaluated the static potential by analyzing the classical action of a string attached to a rectangular Wilson loop on a probe D3 brane located at an intermediate position in the bulk AdS space.We observed that the inclusion of the chemical potential tends to enhance the production rate,which is opposite to the effect of the confining scale.In addition,we calculated the critical electric field based on the Dirac-Born-Infeld(DBI)action.

A Heuristic Approach to the Far-Future State of a Universe Dominated by Phantom Energy

This work is based on a cosmological scenario of a universe dominated by phantom energy with equation of state parameter w﹤-1 and the analysis of its asymptotic behaviour in the far-future. The author discusses whether a Big Rip singularity could be reached in the future. Working in the context of general relativity, it is argued that the Big Rip singularity could be avoided due to the gravitational Schwinger pair-production, even if no other particle-creating contribution takes place. In this model, the universe is described in its far-future by a state of a constant but large Hubble rate and energy density, as well as of a constant but low horizon entropy. Similar conditions existed at the beginning of the universe. Therefore, according to this analysis, not only the Big Rip singularity could be avoided in the far-future but also the universe could asymptotically be led to a new inflationary phase, after which more and more universes could be created.

基于FFT方法的复合材料有效性能预报

将复合材料平衡方程求解问题转化为含极化应力的各向同性材料平衡方程求解问题,利用适用于各向同性材料求解的Lippmann-Schwinger方程实现其形式解,通过FFT方法实现其数值计算,给出其运算法则,实现了复合材料有效性能预报程序化。通过对单向增强复合材料有效性能进行预报与文献中报道的实验结果和其他数值计算结果进行对比验证,表明FFT方法可较精确地预报复合材料的有效性能;讨论了分辨率和尺寸效应对FFT方法的影响,研究结果表明分辨率对FFT方法有一定的影响,尺寸效应对FFT方法无影响。

有限温度及运动背景下的全息Schwinger效应

本文利用势分析的方法研究超标度破坏因子θ和动力学指数z对全息Schwinger效应的影响.其中θ描述对偶场理论中超标度的破坏,z描述系统在相变附近的行为.结果表明,随着θ的增加,Schwinger效应减弱,而动力学指数z增强了Schwinger效应.此外,还发现背景电荷Q(或化学势)和速度β的存在也增强Schwinger效应.

Refined symmetry-resolved Page curve and charged black holes

The Page curve plotted using the typical random state approximation is not applicable to a system with conserved quantities,such as the evaporation process of a charged black hole,during which the electric charge does not macroscopically radiate out with a uniform rate.In this context,the symmetry-resolved entanglement entropy may play a significant role in describing the entanglement structure of such a system.We attempt to impose constraints on microscopic quantum states to match the macroscopic phenomenon of charge radiation during black hole evaporation.Specifically,we consider a simple qubit system with conserved spin/charge serving as a toy model for the evaporation of charged black holes.We propose refined rules for selecting a random state with conserved quantities to simulate the distribution of charges during the different stages of evaporation and obtain refined Page curves that exhibit distinct features in contrast to the original Page curve.We find that the refined Page curve may have a different Page time and exhibit asymmetric behavior on both sides of the Page time.Such refined Page curves may provide a more realistic description for the entanglement between the charged black hole and radiation during the evaporation process.

非均匀强激光场下正负电子对的产生

随着强激光技术领域的不断突破,使得能量转化成物质的施温格过程的实验指日可待.在这样的背景下,在接近实际强激光的模型中理论研究施温格效应至关重要.本文采用量子场论模拟方法在非均匀电场中研究施温格效应的空间特性.首先,发现在能量保持不变的情况下电场的空间尺度显著影响正负电子对的产生率、动量和空间分布.正负电子对的动量和空间分布显示,当电场的空间尺度增大时,因为电场强度变小,所以产生的正负电子对无法及时被分开,抑制正负电子对的产生.最后,用连续性方程研究正负电子对的产生位置分布,发现正负电子对的产生位置分布与电场强度分布是对应的,电子和正电子的产生位置分离一个康普顿波长.此研究结果展示了施温格效应的空间特性,同时解释了弱电场下施温格效应的抑制机制.这些结论在人们常采用的均匀电场近似研究中无法得到.我们的研究对检测施温格实验中的正负电子对具有重要的指导意义.

Super Gaussian enhancers in the Schwinger mechanism

We study the Schwinger mechanism in the presence of an additional uniformly oriented,weak super Gaussian of integer order 4 N+2.Using the worldline approach,we determine the relevant critical points to compute the leading order exponential factor analytically.We show that increasing the parameter N gives rise to a strong dynamical enhancement.For N=2,this effect turns out to be larger compared to a weak contribution of the Sauter type.For higher orders,specifically,for the rectangular barrier limit,i.e.N→∞,we approach the Lorentzian case as an upper bound.Although the mentioned backgrounds significantly differ in Minkowski spacetime,we show that the found coincidence applies due to identical reflection points in the Euclidean instanton plane.In addition,we also treat the background in perturbation theory following recent ideas.By doing so,we show that the parameter N determines whether the weak contribution behaves perturbatively or nonperturbatively with respect to the field strength ratio,and,hence,reveals an interesting dependence on the background shape.In particular,we show that for backgrounds,for which higher orders in the field strength ratio turn out to be relevant,a proposed integral condition is not fulfilled.In view of these findings,the latter may serve as an indicator for the necessity for higher-order contributions.

Chiral phase transition from the Dyson-Schwinger equations in a finite spherical volume

Within the framework of the Dyson-Schwinger equations and by means of Multiple Reflection Expansion,we study the effect of finite volume on the chiral phase transition in a sphere, and discuss in particular its influence on the possible location of the critical end point(CEP). According to our calculations, when we take a sphere instead of a cube, the influence of finite volume on phase transition is not as significant as previously calculated. For instance,as the radius of the spherical volume decreases from infinite to 2 fm, the critical temperature T c, at zero chemical potential and finite temperature, drops only slightly. At finite chemical potential and finite temperature, the location of CEP shifts towards smaller temperature and higher chemical potential, but the amplitude of the variation does not exceed 20%. As a result, we find that not only the size of the volume but also its shape have a considerable impact on the phase transition.

Towards critical and supercritical electromagnetic fields

The availability of ever stronger,laser-generated electromagnetic fields underpins continuing progress in the study and application of nonlinear phenomena in basic physical systems,ranging from molecules and atoms to relativistic plasmas and quantum electrodynamics.This raises the question:how far will we be able to go with future lasers?One exciting prospect is the attainment of field strengths approaching the Schwinger critical field Ecr in the laboratory frame,such that the field invariant E^(2)−c^(2)B^(2)>E_(cr)^(2) is reached.The feasibility of doing so has been questioned,on the basis that cascade generation of dense electron–positron plasma would inevitably lead to absorption or screening of the incident light.Here we discuss the potential for future lasers to overcome such obstacles,by combining the concept of multiple colliding laser pulses with that of frequency upshifting via a tailored laser–plasma interaction.This compresses the electromagnetic field energy into a region of nanometre size and attosecond duration,which increases the field magnitude at fixed power but also suppresses pair cascades.Our results indicate that laser facilities with peak power of tens of PW could be capable of reaching Ecr.Such a scenario opens up prospects for the experimental investigation of phenomena previously considered to occur only in the most extreme environments in the universe.

Dynamic entanglement for continuous variables in an electric field background

Quantum entanglement is a typical nonclassical correlation.Here,we use this concept to analyze quantum entanglement for continuous variables generated by the Schwinger pair production for constant and pulsed electric fields.An initial two-mode entangled state evolves into a three-mode entangled state through a Gaussian channel of the Schwinger effect,which encodes the information about the Schwinger effect.By detecting the entanglement of the output three-mode state,we obtain the optimal parameters for easier to generate particle-antiparticle pairs.We find that the generated 1→2 entanglement is more sensitive to the parameters than the generated 1→1 entanglement.Therefore,we should choose the generated 1→2 entanglement to extract information.We argue that extracting the optimal parameters from quantum entanglement may guide future experiments.

超强场下的正负电子对产生

随着现代强激光技术的迅速发展,激光场强已经进入到了强相对论区域,并正在向产生正负电子对的施温格临界场强逼近。文章着重介绍了超强场下真空失稳产生正负电子对的问题,从历史及其发展的脉络中梳理出有重要价值的研究方法和有趣的研究成果,对目前的研究现状做了综述,并对未来的研究进行展望。

人们能够建成最强的激光吗?

"理论预言激光足够强时可以从真空中产生正负电子对,但没有人知道是否可以实现".本文回顾了从真空中产生正负电子对相关的理论发展,以及理论上要求的激光条件,和目前激光达到的条件:施温格推导出当准静电场达到量子电动力学关键场E_s=me^2c^3/e?=1.32×10^(16) V/cm(对应场强I_s=4.65×10^(29) W/cm^2)时,正负电子对可以从真空中产生;单束聚焦激光产生正负电子对阈值光强约为5×10^(27) W/cm^2;两束相向传输的激光同时聚焦到同一点,对应的单束光强阈值约为10^(26) W/cm^2.考虑到只要有一对正负电子产生,其在激光场作用下的级联过程将耗尽激光场能,使最高的激光场强不能高于约3×10^(26) W/cm^2.目前国际上最高激光功率是由钛蓝宝石激光经过多级啁啾脉冲放大获得,为5.13 PW,对应光强在10^(24) W/cm^2.国际上有几个大的激光项目,近几年目标是10~15 PW,远期目标百拍瓦到艾瓦.远期目标获得的光强可以产生正负电子对,但是能否实现仍然未知.