6,190 research outputs found
Supersymmetric quantum mechanics and the Korteweg-de Vries hierarchy
The connection between supersymmetric quantum mechanics and the Korteweg- de
Vries (KdV) equation is discussed, with particular emphasis on the KdV
conservation laws. It is shown that supersymmetric quantum mechanics aids in
the derivation of the conservation laws, and gives some insight into the Miura
transformation that converts the KdV equation into the modified KdV equation.
The construction of the -function by means of supersymmetric quantum
mechanics is discussed.Comment: 16 pages, latex, EFI 93/2
Multiple transonic solutions and a new class of shock transitions in solar and stellar winds
The steady isothermal solar wind equations are shown to admit, under certain circumstances, mutliple transonic solutions when, for example, momentum deposition gives rise to multiplee critical points in the flow. These multiple solutions consist of a continuous solution and solutions which involve shock transitions between critical solutions. The ambiguity arising from the multiplicity of the solutions can be resolved by following the time evolution of a wind profile with one critical point. Results of the numerical integration of the time-dependent equations with momentum addition show that each of these multiple solutions is physically accessible and depends on the rate of change of momentum deposition. These results suggest that standing shocks are likely to be present in the inner solar wind flow
Formation of standing shocks in stellar winds and related astrophysical flows
Stellar winds and other analogous astrophysical flows can be described, to lowest order, by the familiar one dimensional hydrodynamic equations which, being nonlinear, admit in some instances discontinuous as well as continuous transonic solutions for identical inner boundary conditions. The characteristics of the time dependent differential equations of motion are described to show how a perturbation changes profile in time and, under well defined conditions, develops into a stationary shock discontinuity. The formation of standing shocks in wind type astrophysical flows depends on the fulfillment of appropriate necessary conditions, which are determined by the conservation of mass, momentum and energy across the discontinuity, and certain sufficient conditions, which are determined by the flow's history
Recent Results in Bottomonium
Great strides have been made in the understanding of bound states of a bottom
quark and its antiquark since the discovery of the first
resonances in 1977. These {\it bottomonium} bound states have a rich
spectrum whose masses and transition amplitudes shed valuable light on the
strong interactions. The present article reviews some recent developments in
bottomonium physics. These include the discovery of the spin-singlet states
and , the first D-wave states, one or more candidates for
spin-triplet excitations, and above-threshold states with strong
transitions to states below threshold. Information on transitions, production,
and signatures of new physics is also presented.Comment: 47 pages, 2 figures, to be submitted to Annual Review of Nuclear and
Particle Scienc
Electroweak Constraints from Atomic Parity Violation and Neutrino Scattering
Precision electroweak physics can provide fertile ground for uncovering new
physics beyond the Standard Model (SM). One area in which new physics can
appear is in so-called "oblique corrections", i.e., next-to-leading order
expansions of bosonic propagators corresponding to vacuum polarization. One may
parametrize their effects in terms of quantities and that discriminate
between conservation and non-conservation of isospin. This provides a means of
comparing the relative contributions of precision electroweak experiments to
constraints on new physics. Given the prevalence of strongly -sensitive
experiments, there is an acute need for further constraints on , such as
provided by atomic parity-violating experiments on heavy atoms. We evaluate
constraints on arising from recently improved calculations in the Cs atom.
We show that the top quark mass provides stringent constraints on
within the context of the Standard Model. We also consider the potential
contributions of next-generation neutrino scattering experiments to improved
constraints.Comment: 10 pages, 4 figures, final corrected version to be published in
Physical Review
NaCoO in the x -> 0 Regime: Coupling of Structure and Correlation effects
The study of the strength of correlations in NaCoO is extended to the
x=0 end of the phase diagram where Mott insulating behavior has been widely
anticipated. Inclusion of correlation as modeled by the LDA+U approach leads to
a Mott transition in the subband if U is no less than U=2.5 eV. Thus
U smaller than U is required to model the metallic, nonmagnetic CoO
compound reported by Tarascon and coworkers. The orbital-selective Mott
transition of the state, which is essentially degenerate with the
states, occurs because of the slightly wider bandwidth of the
bands. The metal-insulator transition is found to be strongly coupled to the
Co-O bond length, due to associated changes in the bandwidth, but the
largest effects occur only at a reduced oxygen height that lies below the
equilibrium position.Comment: 8 pages with 9 embedded figure
On the electronic structure of CaCuO2 and SrCuO2
Recent electronic structure calculations for the prototypical lowdimensional
cuprate compounds CaCuO2 ans SrCuO2 performed by Wu et. al. (J. Phys.: Condens.
Matter v. 11 p.4637 (1999))are critically reconsidered, applying high precision
full-potential bandstructure methods. It is shown that the bandstructure
calculations presented by the authors contain several important
inconsistencies, which make their main conclusions highly questionable.Comment: 4 pages, 3 figures, submitted to J. Phys. Condens. Matte
Computer Program for the Calculation of Multicomponent Convective Diffusion Deposition Rates from Chemically Frozen Boundary Layer Theory
The computer program based on multicomponent chemically frozen boundary layer (CFBL) theory for calculating vapor and/or small particle deposition rates is documented. A specific application to perimter-averaged Na2SO4 deposition rate calculations on a cylindrical collector is demonstrated. The manual includes a typical program input and output for users
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