Approximate Treatment of Hermitian Effective Interactions and a Bound on the Error

The Hermitian effective interaction can be well-approximated by (R+R^dagger)/2 if the eigenvalues of omega^dagger omega are small or state-independent(degenerate), where R is the standard non-Hermitian effective interaction and omega maps the model-space states onto the excluded space. An error bound on this approximation is given.Comment: 13 page

Enhancement of singly and multiply strangeness in p-Pb and Pb-Pb collisions at 158A GeV/c

The idea that the reduction of the strange quark suppression in string fragmentation leads to the enhancement of strange particle yield in nucleus-nucleus collisions is applied to study the singly and multiply strange particle production in p-Pb and Pb-Pb collisions at 158A GeV/c. In this mechanism the strange quark suppression factor is related to the effective string tension, which increases in turn with the increase of the energy, of the centrality and of the mass of colliding system. The WA97 observation that the strange particle enhancement increases with the increasing of centrality and of strange quark content in multiply strange particles in Pb-Pb collisions with respect to p-Pb collisions was accounted reasonably.Comment: 8 pages, 3 PostScript figures, in Latex form. submitted to PR

CMBR Constraint on a Modified Chaplygin Gas Model

In this paper, a modified Chaplygin gas model of unifying dark energy and dark matter with exotic equation of state $p=B\rho-\frac{A}{\rho^{\alpha}}$ which can also explain the recent accelerated expansion of the universe is investigated by the means of constraining the location of the peak of the CMBR spectrum. We find that the result of CMBR measurements does not exclude the nonzero value of parameter $B$, but allows it in the range $-0.35\lesssim B\lesssim0.025$.Comment: 4 pages, 3 figure

Investigating the intrinsic noise limit of Dayem bridge NanoSQUIDs

NanoSQUIDs made from Nb thin films have been produced with nanometre loop sizes down to 200 nm, using weak-link junctions with dimensions less than 60 nm. These composite (W/Nb) single layer thin film devices, patterned by FIB milling, show extremely good low-noise performance ∼170 nΦ0 at temperatures between 5 and 8.5 K and can operate in rather high magnetic fields (at least up to 1 T). The devices produced so far have a limited operating temperature range, typically only 1–2 K. We have the goal of achieving operation at 4.2 K, to be compatible with the best SQUID series array (SSA) preamplifier available. Using the SSA to readout the nanoSQUIDs provides us with a means of investigating the intrinsic noise of the former. In this paper we report improved white noise levels of these nanoSQUIDs, enabling potential detection of a single electronic spin flip in a 1-Hz bandwidth. At low frequencies the noise performance is already limited by SSA preamplifier noise

Density-functional theory for 1D harmonically trapped Bose-Fermi mixture

We present a density-functional theory for the one dimensional harmonically trapped Bose-Fermi mixture with repulsive contact interactions. The ground state density distribution of each component is obtained by solving the Kohn-Sham equations numerically based on the Local Density Approximation and the exact solution for the homogeneous system given by Bethe ansatz method. It is shown that for strong enough interaction, a considerable amount of fermions are repelled out of the central region of the trap, exhibiting partial phase separation of Bose and Fermi components. Oscillations emerge in the Bose density curves reflecting the strong correlation with Fermions. For infinite strong interaction, the ground state energy of the mixture and the total density are consistent with the scenario that all atoms in the mixture are fully fermionized.Comment: 10 pages, 8 figure

Phenomenological theory of a scalar electronic order: application to skutterudite PrFe4P12

By phenomenological Landau analysis, it is shown that a scalar order parameter with the point-group symmetry $\Gamma_{1g}$ explains most properties associated with the phase transition in PrFe$_4$P$_{12}$ at 6.5 K. The scalar-order model reproduces magnetic and elastic properties in PrFe$_4$P$_{12}$ consistently such as (i) the anomaly of the magnetic susceptibility and elastic constant at the transition temperature, (ii) anisotropy of the magnetic susceptibility in the presence of uniaxial pressure, and (iii) the anomaly in the elastic constant in magnetic field. An Ehrenfest relation is derived which relates the anomaly of the magnetic susceptibility to that of the elastic constant at the transition.Comment: 16 pages, 9 figure

Quantum Monte Carlo study of a magnetic-field-driven 2D superconductor-insulator transition

We numerically study the superconductor-insulator phase transition in a model disordered 2D superconductor as a function of applied magnetic field. The calculation involves quantum Monte Carlo calculations of the (2+1)D XY model in the presence of both disorder and magnetic field. The XY coupling is assumed to have the form -J\cos(\theta_i-\theta_j-A_{ij}), where A_{ij} has a mean of zero and a standard deviation \Delta A_{ij}. In a real system, such a model would be approximately realized by a 2D array of small Josephson-coupled grains with slight spatial disorder and a uniform applied magnetic field. The different values \Delta A_{ij} then corresponds to an applied field such that the average number of flux quanta per plaquette has various integer values N: larger N corresponds to larger \Delta A_{ij}. For any value of \Delta A_{ij}, there appears to be a critical coupling constant K_c(\Delta A_{ij})=\sqrt{[J/(2U)]_c}, where U is the charging energy, above which the system is a Mott insulator; there is also a corresponding critical conductivity \sigma^*(\Delta A_{ij}) at the transition. For \Delta A_{ij}=\infty, the order parameter of the transition is a renormalized coupling constant g. Using a numerical technique appropriate for disordered systems, we show that the transition at this value of \Delta A_{ij} takes place from an insulating (I) phase to a Bose glass (BG) phase, and that the dynamical critical exponent characterizing this transition is z \sim 1.3. By contrast, z=1 for this model at \Delta A_{ij}=0. We suggest that the superconductor to insulator transition is actually of this I to BG class at all nonzero \Delta A_{ij}'s, and we support this interpretation by both numerical evidence and an analytical argument based on the Harris criterion.Comment: 17 pages, 23 figures, accepted for publication in Phys. Rev.

Wearable activity sensors and early pain after total joint arthroplasty.

A prospective observational cohort of 20 primary total hip arthroplasty (n = 12) and total knee arthroplasty (n = 8) patients (mean age: 63 ± 6 years) was passively monitored with a consumer-level wearable activity sensor before and 6 weeks after surgery. Patients were clustered by minimal change or decreased activity using sensor data. Decreased postoperative activity was associated with greater pain reduction (-5.5 vs -2.0, P = .03). All patients surpassed minimal clinical benefit thresholds of total joint arthroplasty (TJA) (Hip Disability and Osteoarthritis Score Junior 30.5 vs 20.8, P = .23; Knee Injury and Osteoarthritis Outcome Score Junior 23.3 vs 18.2, P = .77) within 6 weeks. Patients who objectively "take it easy" after TJA may experience less pain with no difference in early subjective outcome. Remote, passive analysis of outpatient wearable sensor data may permit real-time detection of early problems after TJA