269,209 research outputs found
Approximate Theoretical Calculation of Continuum Opacities
An approxhnate procedure is described for the theoretical calculation of the spectral absorption
coefficient produced by bound-free and free-free transitions in plasmas containing polyelectronic
atoms and ions. Our method of calculation is based on the assumption that only two ionized species make important contributions to the opacity and that these two ionic
constituents are present in equal concentrations. The approximate formulas are shown to yield results that are in good accord with estimates based on detailed numerical computations for nitrogen
Perfect colourings of isonemal fabrics by thin striping
Perfect colouring of isonemal fabrics by thin striping of warp and weft and
the closely related topic of isonemal prefabrics that fall apart are
reconsidered and their relation further explored. The catalogue of isonemal
prefabrics that fall apart is extended to order 20 for those of even genus.Comment: 25 pages, 20 figure
Magnetic trapping of neutral particles: Classical and Quantum-mechanical study of a Ioffe-Pritchard type trap
Recently, we developed a method for calculating the lifetime of a particle
inside a magnetic trap with respect to spin flips, as a first step in our
efforts to understand the quantum-mechanics of magnetic traps. The 1D toy model
that was used in this study was physically unrealistic because the magnetic
field was not curl-free. Here, we study, both classically and
quantum-mechanically, the problem of a neutral particle with spin S, mass m and
magnetic moment mu, moving in 3D in an inhomogeneous magnetic field
corresponding to traps of the Ioffe-Pritchard, `clover-leaf' and `baseball'
type. Defining by omega_p, omega_z and omega_r the precessional, the axial and
the lateral vibrational frequencies, respectively, of the particle in the
adiabatic potential, we find classically the region in the $(\omega_{r}%
(omega_r -- omega_z) plane where the particle is trapped.
Quantum-mechanically, we study the problem of a spin-one particle in the same
field. Treating omega_r / omega_p and omega_z / omega_p as small parameters for
the perturbation from the adiabatic Hamiltonian, we derive a closed-form
expression for the transition rate 1/T_{esc} of the particle from its trapped
ground-state. We find that in the extreme cases, the expression for 1/T_{esc}
is dominated by the largest of the two frequencies omega_r and omega_z.Comment: 25 pages + 1 EPS figur
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The implication of the hyperbolic discount model for annuitisation decisions
The low demand for immediate annuities at retirement has been a long-standing puzzle. We show that a hyperbolic discount model can explain this behaviour and results in the attractiveness of long-term deferred annuities. With a set of benchmark assumptions, we find that retirees would be willing to pay a much higher price than the actuarial fair price for annuities with longer deferred periods. Moreover, if governments were to introduce a pre-commitment device which requires pensioners to make annuitisation decisions around ten years before retirement, the take up rate of annuities could become higher
Mandating Disclosure in Municipal Securities Issues: Proposed New York Legislation
This article surveys the existing mechanisims (primarily stemming from federal law) resulting in financial disclosure in connection with the offering and sale to the public of securities of New York municipal issuers. It also describes and compares alternative models for regimes of municipal issuer financial disclosure, such as the MFOA Guidelines, the federal Williams Bill and Industrial Bond Act and New York\u27s Disclosure Proposals. The article ultimately concludes that although the isolated purpose of protecting investors in a municipal securities market that is largely national could most effectively be pursued by the imposition of uniform disclosure requirements through federal law, the Disclosure Proposals are not demonstrably inadequate to this purpose, and the intrustion into the affiars of the state and local governments of New York that would accompany the federal law approach makes the enactment of the Disclosure Proposals a more attractive alternative
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