43,547 research outputs found
Non-equilibrium radiation nuclear reactor
An externally moderated thermal nuclear reactor is disclosed which is designed to provide output power in the form of electromagnetic radiation. The reactor is a gaseous fueled nuclear cavity reactor device which can operate over wide ranges of temperature and pressure, and which includes the capability of processing and recycling waste products such as long-lived transuranium actinides. The primary output of the device may be in the form of coherent radiation, so that the reactor may be utilized as a self-critical nuclear pumped laser
g-factor of a tightly bound electron
We study the hyperfine splitting of an electron in hydrogen-like . It is found that the hfs energy splitting can be explained well by
considering the g-factor reduction due to the binding effect of a bound
electron. We determine for the first time the experimental value of the
magnetic moment of a tightly bound electron.Comment: 6 pages, Latex, Phys. Rev. A in pres
On the role of shake-off in single-photon double ionization
The role of shake-off for double ionization of atoms by a single photon with
finite energy has become the subject of debate. In this letter, we attempt to
clarify the meaning of shake-off at low photon energies by comparing different
formulations appearing in the literature and by suggesting a working
definition. Moreover, we elaborate on the foundation and justification of a
mixed quantum-classical ansatz for the calculation of single-photon double
ionization
Luttinger liquids with boundaries: Power-laws and energy scales
We present a study of the one-particle spectral properties for a variety of
models of Luttinger liquids with open boundaries. We first consider the
Tomonaga-Luttinger model using bosonization. For weak interactions the boundary
exponent of the power-law suppression of the spectral weight close to the
chemical potential is dominated by a term linear in the interaction. This
motivates us to study the spectral properties also within the Hartree-Fock
approximation. It already gives power-law behavior and qualitative agreement
with the exact spectral function. For the lattice model of spinless fermions
and the Hubbard model we present numerically exact results obtained using the
density-matrix renormalization-group algorithm. We show that many aspects of
the behavior of the spectral function close to the boundary can again be
understood within the Hartree-Fock approximation. For the repulsive Hubbard
model with interaction U the spectral weight is enhanced in a large energy
range around the chemical potential. At smaller energies a power-law
suppression, as predicted by bosonization, sets in. We present an analytical
discussion of the crossover and show that for small U it occurs at energies
exponentially (in -1/U) close to the chemical potential, i.e. that bosonization
only holds on exponentially small energy scales. We show that such a crossover
can also be found in other models.Comment: 16 pages, 9 figures included, submitted for publicatio
Gravitational Lensing by Power-Law Mass Distributions: A Fast and Exact Series Approach
We present an analytical formulation of gravitational lensing using familiar
triaxial power-law mass distributions, where the 3-dimensional mass density is
given by . The deflection angle and magnification factor are
obtained analytically as Fourier series. We give the exact expressions for the
deflection angle and magnification factor. The formulae for the deflection
angle and magnification factor given in this paper will be useful for numerical
studies of observed lens systems. An application of our results to the Einstein
Cross can be found in Chae, Turnshek, & Khersonsky (1998). Our series approach
can be viewed as a user-friendly and efficient method to calculate lensing
properties that is better than the more conventional approaches, e.g.,
numerical integrations, multipole expansions.Comment: 24 pages, 3 Postscript figures, ApJ in press (October 10th
Torque magnetometry on single-crystal high temperature superconductors near the critical temperature: a scaling approach
Angular-dependent magnetic torque measurements performed near the critical
temperature on single crystals of HgBa_{2}CuO_{4+y}, La_{2-x}Sr{x}CuO_{4}, and
YBa_{2}Cu_{3}O_{6.93} are scaled, following the 3D XY model, in order to
determine the scaling function dG^{\pm}(z)/dz which describes the universal
critical properties near T_{c}. A systematic shift of the scaling function with
increasing effective mass anisotropy \gamma = (m_{ab}*/m_{c}*)^{1/2} is
observed, which may be understood in terms of a 3D-2D crossover. Further
evidence for a 3D-2D crossover is found from temperature-dependent torque
measurements carried out in different magnetic fields at different field
orientations \delta, which show a quasi 2D "crossing region'' (M*,T*). The
occurrence of this "crossing phenomenon'' is explained in a phenomenological
way from the weak z dependence of the scaling function around a value z = z*.
The "crossing'' temperature T* is found to be angular-dependent. Torque
measurements above T_{c} reveal that fluctuations are strongly enhanced in the
underdoped regime where the anisotropy is large, whereas they are less
important in the overdoped regime.Comment: 9 pages, 10 figures, submitted to PR
Isotope effects in underdoped cuprate superconductors: a quantum phenomenon
We show that the unusual doping dependence of the isotope effects on
transition temperature and zero temperature in - plane penetration depth
naturally follows from the doping driven 3D-2D crossover, the 2D quantum
superconductor to insulator transition (QSI) in the underdoped limit and the
change of the relative doping concentration upon isotope substitution. Close to
the QSI transition both, the isotope coefficient of transition temperature and
penetration depth approach the coefficient of the relative dopant
concentration, and its divergence sets the scale. These predictions are fully
consistent with the experimental data and imply that close to the underdoped
limit the unusual isotope effect on transition temperature and penetration
depth uncovers critical phenomena associated with the quantum superconductor to
insulator transition in two dimensions.Comment: 6 pages, 3 figure
Origin of Lagrangian Intermittency in Drift-Wave Turbulence
The Lagrangian velocity statistics of dissipative drift-wave turbulence are
investigated. For large values of the adiabaticity (or small collisionality),
the probability density function of the Lagrangian acceleration shows
exponential tails, as opposed to the stretched exponential or algebraic tails,
generally observed for the highly intermittent acceleration of Navier-Stokes
turbulence. This exponential distribution is shown to be a robust feature
independent of the Reynolds number. For small adiabaticity, algebraic tails are
observed, suggesting the strong influence of point-vortex-like dynamics on the
acceleration. A causal connection is found between the shape of the probability
density function and the autocorrelation of the norm of the acceleration
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