Intrinsic-Density Functionals

The Hohenberg-Kohn theorem and Kohn-Sham procedure are extended to functionals of the localized intrinsic density of a self-bound system such as a nucleus. After defining the intrinsic-density functional, we modify the usual Kohn-Sham procedure slightly to evaluate the mean-field approximation to the functional, and carefully describe the construction of the leading corrections for a system of fermions in one dimension with a spin-degeneracy equal to the number of particles N. Despite the fact that the corrections are complicated and nonlocal, we are able to construct a local Skyrme-like intrinsic-density functional that, while different from the exact functional, shares with it a minimum value equal to the exact ground-state energy at the exact ground-state intrinsic density, to next-to-leading order in 1/N. We briefly discuss implications for real Skyrme functionals.Comment: 15 page

Trispectrum versus Bispectrum in Single-Field Inflation

In the standard slow-roll inflationary cosmology, quantum fluctuations in a single field, the inflaton, generate approximately Gaussian primordial density perturbations. At present, the bispectrum and trispectrum of the density perturbations have not been observed and the probability distribution for these perturbations is consistent with Gaussianity. However, Planck satellite data will bring a new level of precision to bear on this issue, and it is possible that evidence for non-Gaussian effects in the primordial distribution will be discovered. One possibility is that a trispectrum will be observed without evidence for a non-zero bispectrum. It is not difficult for this to occur in inflationary models where quantum fluctuations in a field other than the inflaton contribute to the density perturbations. A natural question to ask is whether such an observation would rule out the standard scenarios. We explore this issue and find that it is possible to construct single-field models in which inflaton-generated primordial density perturbations have an observable trispectrum, but a bispectrum that is too small to be observed by the Planck satellite. However, an awkward fine tuning seems to be unavoidable.Comment: 15 pages, 3 figures; journal versio

Changes in r-process abundances at late times

We explore changes in abundance patterns that occur late in the r process. As the neutrons available for capture begin to disappear, a quasiequilibrium funnel shifts material into the large peaks at A=130 and A=195, and into the rare-earth "bump" at A=160. A bit later, after the free-neutron abundance has dropped and beta-decay has begun to compete seriously with neutron capture, the peaks can widen. The degree of widening depends largely on neutron-capture rates near closed neutron shells and relatively close to stability. We identify particular nuclei the capture rates of which should be examined experimentally, perhaps at a radioactive beam facility.Comment: 8 pages, 14 figures included in tex

Capture of solar and higher-energy neutrinos by 127I

We discuss and improve a recent treatment of the absorption of solar neutrinos by 127I, in connection with a proposed solar neutrino detector. With standard-solar-model fluxes and an in-medium value of -1.0 for the axial-vector coupling constant gA, we obtain a 8neutrino cross section of 3.3×10^-42, about 50% larger than in our previous work, and a 7Be cross section that is less certain but nevertheless also larger than before. We then apply the improved techniques to higher incoming energies that obtain at the LAMPF beam dump, where an experiment is underway to finalize a calibraiton of the 127I with electron neutrinos from muon decay. We find that forbidden operators, which play no role in solar-neutrino absorption, contribute nonnegligibly to the LAMPF cross section, and that the preliminary LAMPF mean value is significantly larger than our prediction

On the jets, kinks, and spheromaks formed by a planar magnetized coaxial gun

Measurements of the various plasma configurations produced by a planar magnetized coaxial gun provide insight into the magnetic topology evolution resulting from magnetic helicity injection. Important features of the experiments are a very simple coaxial gun design so that all observed geometrical complexity is due to the intrinsic physical dynamics rather than the source shape and use of a fast multiple-frame digital camera which provides direct imaging of topologically complex shapes and dynamics. Three key experimental findings were obtained: (1) formation of an axial collimated jet [Hsu and Bellan, Mon. Not. R. Astron. Soc. 334, 257 (2002)] that is consistent with a magnetohydrodynamic description of astrophysical jets, (2) identification of the kink instability when this jet satisfies the Kruskal-Shafranov limit, and (3) the nonlinear properties of the kink instability providing a conversion of toroidal to poloidal flux as required for spheromak formation by a coaxial magnetized source [Hsu and Bellan, Phys. Rev. Lett. 90, 215002 (2003)]. A new interpretation is proposed for how the n=1 central column instability provides flux amplification during spheromak formation and sustainment, and it is shown that jet collimation can occur within one rotation of the background poloidal field.Comment: Physics of Plasmas (accepted

Does Law School Still Make Economic Sense?: An Empirical Analysis of Big Law Firm Partnership Prospects and the Relationship to Law School Attended

Prospective law students and those in the legal community are often precluded from properly evaluating the potential likelihood that their choice of law school can measurably and tangibly impact their prospects for big law firm partnership 1 and its attendant, anticipated economic rewards. In an effort to answer the question of whether law school makes sense from an economic decision-making rationale - if one assumes (and we can certainly argue about this assumption) that one objective to attending law school is to become a partner in a large (and generally lucrative) law firm setting - this Study examines the characteristics of partners at large law firms across the country according to five main variable

Quantum oscillations observed in graphene at microwave frequencies

We have measured the microwave conductance of mechanically exfoliated graphene at frequencies up to 8.5 GHz. The conductance at 4.2 K exhibits quantum oscillations, and is independent of the frequency

Possible origin of the 0.5 plateau in the ballistic conductance of quantum point contacts

A non-equilibrium Green function formalism (NEGF) is used to study the conductance of a side-gated quantum point contact (QPC) in the presence of lateral spin-orbit coupling (LSOC). A small difference of bias voltage between the two side gates (SGs) leads to an inversion asymmetry in the LSOC between the opposite edges of the channel. In single electron modeling of transport, this triggers a spontaneous but insignificant spin polarization in the QPC. However, the spin polarization of the QPC is enhanced substantially when the effect of electron-electron interaction is included. The spin polarization is strong enough to result in the occurrence of a conductance plateau at 0.5G0 (G0 = 2e2/h) in the absence of any external magnetic field. In our simulations of a model QPC device, the 0.5 plateau is found to be quite robust and survives up to a temperature of 40K. The spontaneous spin polarization and the resulting magnetization of the QPC can be reversed by flipping the polarity of the source to drain bias or the potential difference between the two SGs. These numerical simulations are in good agreement with recent experimental results for side-gated QPCs made from the low band gap semiconductor InAs