Spin-lattice relaxation of deuterated methyl groups: Implications of the pauli principle

The high-field spin-lattice relaxation of deuterated methyl groups undergoing rotational tunneling is investigated theoretically. It is found that for systems showing a tunneling frequency comparable to accessible Larmor frequencies the relaxation to equilibrium of the Zeeman energy does not follow a simple exponential time dependence even in powdered samples due to a finite coupling to the relaxation of the tunneling system. This finding contrasts to the high-temperature behavior of reorienting methyl groups which undergo simple exponential relaxation. The nonexponentiality has its origin in the statistical coupling of the three deuteron spins due to the Pauli principle.     

New experimental test of the pauli exclusion principle using accelerator mass spectrometry

We report the results of a new experimental search for the Pauli-forbidden 1s(4) state of Be, denoted by Be ('). Using the Accelerator Mass Spectrometer facility at Purdue University, we set limits on the abundance of Be (') in metallic Be, Be ore, natural gas, and air. Our results improve on those obtained in a previous search for Be (') by a factor of approximately 300.     

Derivation of an adiabatic time-dependent Hartree-Fock formalism from a variational principle

A derivation of the adiabatic time-dependent Hartree-Fock formalism is given, which is based on a variational principle analogous to Hamilton's principle in classical mechanics. The method leads to a Hamiltonian for collective motion which separates into a potential and a kinetic energy and gives mass and potential parameters in terms of the nucleon-nucleon interaction. The adiabatic approximation assumes slow motion but not small amplitudes and can therefore describe anharmonic effects. The RPA is a limiting case where both amplitudes and velocities are small. The variational approach provides a consistent way of extracting coordinates and momenta from the density matrix and of obtaining equations of motion when particular trial forms for this density matrix are chosen. One such choice leads to Thouless-Valatin formula. An other choice leads to irrotational hydrodynamics.     

Nuclear transparency due to the pauli exclusion principle and the study of densities in the nuclear interior

24.5 MeV proton elastic scattering data for ³²S, ¹¹⁸Sn and ²⁰⁸Pb are analyzed in the framework of an optical-model potential. This potential is calculated by a folding procedure using interactions corrected for Pauli effects and Fermi motion. Neutron densities are extracted in a model-independent fashion. The sensitivity of low-energy proton scattering to the density in the nuclear interior due to the long mean free path is established.     

An action principle and canonical formalism for the Neveu Schwarz-Ramond string

A Lagrangian giving the constraints and boundary conditions of the Neveu Schwarz-Ramond model is presented.     

SUSY formalism for the symmetric double well potential

Using first- and second-order supersymmetric Darboüx formalism and starting with symmetric double well potential barrier we have obtained a class of exactly solvable potentials subject to moving boundary condition. The eigenstates are also obtained by the same technique.     

An axiomatic deduction of the pauli spinor theory

Pauli's spinor theory is deduced entirely from a postulate relating to the two-valuedness of the spectrum of the Pauli spin operators, without explicit use of the theory of group representations, or any assumption concerning the angular momentum properties of these operators.     

Investigations of the pion-nucleus optical potential from pionic atoms

The explicit dependence of the zero-energy π^?-nucleus optical potential on its various parameters, as well as its implicit dependence on neutron radii, is investigated for a selected set of particularly accurate level shift and width data. Among the various effects studied are some possible variations in the form of the Lorentz-Lorenz term, terms induced by the so-called “angle-transformation”, and the smearing of the π 2N terms which allows for a finite range in the absorption process. The pionic atom data are equally well fitted by any of the several forms used for the optical potential, with the persistent failure to fit the recently reported widths of 3d levels in ¹⁸¹Ta, Re and ²⁰⁹Bi and the width of the 1s level in ²³Na.     

Corrections to the Casimir–Polder potential arising from electric octupole coupling

ABSTRACT

Molecular QED theory is employed to derive a generalised formula for the dispersion potential between two molecules with mixed electric multipole polarisability tensors of arbitrary order at each centre. This expression is used to readily extract the pair energy shift between an electric dipole polarisable molecule and a mixed electric dipole–octupole polarisable one, and that between two mixed electric dipole–octupole polarisable species. This is done to see whether these interaction energies give rise to higher-order corrections to the Casimir–Polder potential, as was found in the previously calculated case of the dispersion energy shift between an electric dipole polarisable molecule and an electric octupole polarisable one. Interestingly, for orientationally averaged species, both of the computed interaction energies are independent of the octupole weight-3 term, are retarded, and may be interpreted as higher-order corrections in the fine structure constant to the leading dipole–dipole dispersion potential.     

Anderson localization from the replica formalism

We study Anderson localization in quasi-one-dimensional disordered wires within the framework of the replica sigma model. Applying a semiclassical approach (geodesic action plus Gaussian fluctuations) recently introduced within the context of supersymmetry by Lamacraft, Simons, and Zirnbauer, we compute the exact density of transmission matrix eigenvalues of superconducting wires (of symmetry class CI.) For the unitary class of metallic systems (class A) we are able to obtain the density function, save for its large transmission tail.     

Problems arising in the development of optical communication systems

The report starts with a survey of methods and feasibilities for the application of optical transmission systems in present and in future communication networks. Transmission systems with 1.12 Gbit/s offer new prospects for developing integrated communication systems. Therefore for this bitrate the use of optical components and the attainable repeater distances are discussed in detail. Finally an experimental model of an integrated broadband network is presented allowing to study the unsolved problems of using optical transmission channels in complex transmission and switching systems.     

光纤通信光开关的物理基础

光开关是光交换系统的基本元件，也是一种基本的控光器件，本文综述了目前光纤通信中所研究和开发的光通信开关器件的物理原理，并给出各类光开关的阈值条件和典型参量。     

光纤通信光开关的物理基础(续)

3.2　定向耦合器电光开关定向耦合器电光开关是在电光材料 (如L i Nb O3、化合物半导体、有机聚合物 )的衬底上制作 1对条形波导和 1对电极构成 ,如图 5所示 .当不加电压时 ,它是 1个具有 2条波导和 4个端口的定向耦合器 .一般称 1 -3和 2 -4为直通臂 ,1 -4和 2 -3为交叉臂 .图 5　定向耦合器型光开关假设两波导的耦合较弱 ,各自保持独立存在时的场分布和传输系数 ,耦合的影响只表现在场的振幅随耦合长度的变化 .设两波导中的复数振幅分别为 E1(z)和 E2 (z) ,相位常量是β1和 β2 ,其变化规律可用一阶微分方程组表示 [3]d E1(z)dz =-ik12…     

光纤通信光开关的物理基础(续)

4　热光开关热光开关和电光开关的结构可以相同 ,但是产生开关效应的机理不同 .这里的热光效应是指通过电流加热的方法 ,使介质的温度变化 ,导致光在介质中传播的折射率和相位发生改变的物理效应 .折射率随温度的变化关系为n(T) =n0 +Δn(T) =n0 + n TΔT=n0 +αΔT(6 9)式中 n0 为温度变化之前的折射率 ,ΔT为温度的变化 ,α为热光系数 ,它与材料的种类有关 .表 3是几种材料的热光系数 .表 3　几种材料的热光系数材料 α/ (10 - 4K- 1 )L i Nb O30 .0 4 3Si 2Si O2 1.1聚合物 1　　Δn将引起相位变化为Δφ=2 πΔn L/ λ0 =2 παL…     

From nuclear stopping to interatomic potential via the power law formalism

A general method for inverting the energy-dependent nuclear stopping cross sections S_n(?) to derive the interatomic potential V(x) is described. A correspondence between ? and x is derived for mapping S_n(?) to V(x) and vice versa. The method is illustrated by using the recent range-energy data of keV indium and xenon ions in amorphous silicon to self-consistently deduce the In-Si and Xe-Si potentials.     

Covariant conservation laws from the palatini formalism

Covariant conservation laws in the Palatini formalism are derived. The result indicates that the gravitational part of conserved charges in general relativity should be calculated from a combination of Komar's strongly conserved current and the Einstein tensor. This implies that the set of complete diffeomorphism charges of a gravitating system consisting of scalar matter is described by Komar's vector density, and that the identification of gravitational energy and momentum reduces to two choices: a choice of relative weights of the contributions resulting from Komar's current and from the Einstein tensor, and a choice of preferred vector fields in space-time. A proposal is made which yields energy and momentum as scalars under diffeomorphisms and as a Lorentz vector in tangent space. Furthermore, the result can be used to identify covariant conservation laws holding separately for the matter contributions to diffeomorphism charges.     

Information hiding based on the optical interference principle

An information hiding method based on the optical interference principle is proposed. In this method, a secret image can be obtained by two light beams' interference. One of the beams is modulated by our assigned host image; and the other is modulated by a noise-like complex distribution, which is regard as the encrypted image. The transmission of the encrypted image can be implemented by hiding it in the host image to prevent the communication from being perceived by unauthorized person. In addition, this method can also realize simultaneous encryption and hiding for two images. A series of numerical simulation results are presented to verify the feasibility of our proposed method.