Second-order eikonal corrections for

The first-order eikonal approximation is frequently adopted in interpreting the results of A(e,e^′p) measurements. Glauber calculations, for example, typically adopt the first-order eikonal approximation. We present an extension of the relativistic eikonal approach to A(e,e^′p) which accounts for second-order eikonal corrections. The numerical calculations are performed within the relativistic optical model eikonal approximation. The nuclear transparency results indicate that the effect of the second-order eikonal corrections is rather modest, even at Q²≈0.2 (GeV/c)². The same applies to polarization observables, left–right asymmetries, and differential cross sections at low missing momenta. At high missing momenta, however, the second-order eikonal corrections are significant and bring the calculations in closer agreement with the data and/or the exact results from models adopting partial-wave expansions.     

Quantum gravity stability of isotropy in homogeneous cosmology

It has been shown that anisotropy of homogeneous spacetime described by the general Kasner metric can be damped by quantum fluctuations coming from perturbative quantum gravity in one-loop approximation. Also, a formal argument, not limited to one-loop approximation, is put forward in favor of stability of isotropy in the exactly isotropic case.     

Inelastic neutron scattering,Raman, vibrational analysis with anharmonic corrections,and scaled quantum mechanical force field for polycrystalline l-alanine

A scaled quantum mechanical harmonic force field (SQMFF) corrected for anharmonicity is obtained for the 23 K l-alanine crystal structure using van der Waals corrected periodic boundary condition density functional theory (DFT) calculations with the PBE functional. Scale factors are obtained with comparisons to inelastic neutron scattering (INS), Raman, and FT-IR spectra of polycrystalline l-alanine at 15–23 K. Calculated frequencies for all 153 normal modes differ from observed frequencies with a standard deviation of 6 wavenumbers. Non-bonded external k = 0 lattice modes are included, but assignments to these modes are presently ambiguous. The extension of SQMFF methodology to lattice modes is new, as are the procedures used here for providing corrections for anharmonicity and van der Waals interactions in DFT calculations on crystals. First principles Born–Oppenheimer molecular dynamics (BOMD) calculations are performed on the l-alanine crystal structure at a series of classical temperatures ranging from 23 K to 600 K. Corrections for zero-point energy (ZPE) are estimated by finding the classical temperature that reproduces the mean square displacements (MSDs) measured from the diffraction data at 23 K. External k = 0 lattice motions are weakly coupled to bonded internal modes.     

Corrections in the Measurement of Fluorescence Polarization

Abstract

Blank corrections in polarization measurements with single beam spectrofluorometers are straightforward and permit characterization of polarization spectra of samples having quantum yields of less than 0.01. Few samples require no such correction. Problems in determining what is a suitable blank are discussed. Such blanks have unfortunately been ignored in many studies, and dual phototube instruments have been advocated in which it is difficult to apply such corrections. G, the grating correction factor, is shown to vary sharply with emission wavelength, in contrast to other reports, but is independent of slit width. Therefore, a calibration curve of G vs. emission wavelength may be obtained for a given instrument, thus avoiding the need to determine G for each sample.     

Single-polaron properties in the one-dimensional Holstein and SSH models

We study the single-polaron properties of the one-dimensional Holstein and SSH model. The dynamical coherent potential approximation (under the Hartree approximation) is applied to compute the polaron dispersion, the quasi-particle residue, and the polaron?s Green?s functions. We compare our calculated results in comparison with those by the self-consistent Born approximation plus higher-order diagrams.     

New Estimates for the Rate of Convergence of the Method of Subspace Corrections

We discuss estimates for the rate of convergence of the method of successive subspace corrections in terms of condition number estimate for the method of parallel subspace corrections. We provide upper bounds and in a special case, a lower bound for preconditioners defined via the method of successive subspace corrections.     

材料非线性衰减系数的二次谐波测量方法研究

采用有限幅值法测量材料在基波和非线性引起的二次谐波作用下的衰减系数:利用准线性下的KZK方程推导基波和二次谐波的声压分布,并提取波束修正系数;采用短纯音信号进行非线性实验,对检测得到的基波和二次谐波声压进行衍射修正处理,有效抑制衍射对衰减系数测量的不利影响,继而通过线性拟合的方法计算得到更精确的基波和二次谐波的衰减系数。以水为例进行实验,研究了实验测量所得衰减系数的频率依赖关系,结果表明在非线性条件下水的衰减系数与频率间存在较强的线性关系,而线性条件下衰减系数随频率呈现二次方增长的特性则不适用于非线性条件。该研究提出了准确测量非线性声波衰减系数的方法,为更有效地应用非线性超声检测提供理论依据。     

Gauge threshold corrections in intersecting brane world models

We calculate the one‐loop corrections to gauge couplings in N = 1 supersymmetric brane world models, which are realized in an type IIA orbifold/orientifold background with several stacks of D6 branes wrapped on 3‐cycles with non‐vanishing intersections. Contributions arise from both N = 1 and N = 2 open string subsectors. In contrast to what is known from ordinary orbifold theories, N = 1 subsectors do give rise to moduli‐dependent one‐loop corrections.