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191.
192.
We have designed and tested a new relativistic Lagrangian hydrodynamics code, which treats gravity in the conformally flat
approximation to general relativity. We have tested the resulting code extensively, finding that it performs well for calculations
of equilibrium single-star models, collapsing relativistic dust clouds, and quasi-circular orbits of equilibrium solutions.
By adding a radiation reaction treatment, we compute the full evolution of a coalescing binary neutron star system. We find
that the amount of mass ejected from the system, much less than a per cent, is greatly reduced by the inclusion of relativistic
gravitation. The gravity wave energy spectrum shows a clear divergence away from the Newtonian point-mass form, consistent
with the form derived from relativistic quasi-equilibrium fluid sequences. 相似文献
193.
通过仔细研究俘获加速CAS(captureandaccelerationscenario)机制中电子束团的输出特性,发现其出射电子有3类不同的运动轨道即掠过(pass-by)、非弹性散射(IS)、CAS.由于实际入射电子束团的线度远大于强激光脉冲的线度,因此只有位于入射电子束团中心区域的电子才可能被俘获加速.对于目前所能获得的聚焦激光场强(~1021W/cm2)和实际的电子束团(~108个电子)而言,最大的输出能量可达到450MeV以上,同时被加速电子的数目可达到104—105个.这表明CAS可望发展成为小型台式加速器的新加速原理 相似文献
194.
195.
为了探索超热电子的加热机制,利用光学CCD相机和OMA光学多道分析仪,分别在靶背法线方向测量了光学渡越辐射(OTR)积分成像图案和光谱。实验在100 TW掺钛蓝宝石激光器上进行,飞秒激光与铜膜靶作用后,靶表面发光信号由空间分辨装置聚焦成像并引到CCD或OMA谱仪的狭缝上。测得的积分成像图案呈圆环状,光斑形成区域直径约为225 μm,在圆环边缘附近出现局部化明亮光信号,该现象表明,超热电子在传输的过程中存在成丝效应,其分布也不均匀。光谱在300~500 nm之间出现一系列非周期锐利尖峰,在400 nm(2ω0)附近出现的尖峰应归因于v×B加热机制产生的超热电子引起的相干渡越辐射(CTR)。 相似文献
196.
Poor convergence behavior is usually encountered when numerical computations on turbulent separated flow are performed. A design of self‐adjusted stepsize concept both in time span and spatial coordinate systems to achieve faster convergence is demonstrated in this study. The determination of the time stepsize based on the concept of minimization of residuals using the Bi‐CGSTAB algorithm is proposed. The numerical results show that the time stepsize adjusted by the proposed method indeed improves the convergence rate for turbulent separated flow computations using advanced turbulence models in low‐Reynolds number forms. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
197.
198.
G. A. Alekseev 《Theoretical and Mathematical Physics》2005,144(2):1065-1074
We elucidate the integrability structures of the matrix generalizations of the Ernst equation for Hermitian or complex symmetric
(d×d)-matrix Ernst potentials. These equations arise in string theory as the equations of motion for the truncated bosonic
parts of the low-energy effective action for the respective dilaton and d×d matrix of moduli fields or for a string gravity
model with a scalar (dilaton) field, a U(1) gauge vector field, and an antisymmetric 3-form field, all depending on only two
space-time coordinates. We construct the corresponding spectral problems based on the overdetermined 2d×2d linear systems
with a spectral parameter and the universal (i.e., solution-independent) structures of the canonical Jordan forms of their
matrix coefficients. The additionally imposed existence conditions for each of these systems of two matrix integrals with
appropriate symmetries provide specific (coset) structures of the related matrix variables. We prove that these spectral problems
are equivalent to the original field equations, and we envisage an approach for constructing multiparametric families of their
solutions.
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Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 144, No. 2, pp. 214–225, August, 2005. 相似文献
199.
K. A. Bronnikov S. A. Kononogov V. N. Melnikov 《General Relativity and Gravitation》2006,38(7):1215-1232
We discuss possible variations of the effective gravitational constant with length scale, predicted by most of alternative theories of gravity and unified models of physical interactions. After giving a brief general exposition, we review in more detail the predicted corrections to Newton’s law of gravity in diverse brane world models. We consider various configurations in 5 dimensions (flat, de Sitter and AdS branes in Einstein and Einstein–Gauss–Bonnet theories, with and without induced gravity and possible incomplete graviton localization), 5D multi-brane systems and some models in higher dimensions. A common feature of all models considered is the existence of corrections to Newton’s law at small radii comparable with the bulk characteristic length: at such radii, gravity on the brane becomes effectively multidimensional. Many models contain superlight perturbation modes, which modify gravity at large scale and may be important for astrophysics and cosmology. 相似文献
200.
利用激光单缝衍射技术测量大气飘尘的真比重,具有精度高和测试方法简便易行的特点。本文采用此法测量了飘尘样品的真比重,以满意的结果证明了该法的可行性。 相似文献