A Second Relativistic Mean Field and Virial Equation of State for Astrophysical Simulations

We generate a second equation of state (EOS) of nuclear matter for a wide range of temperatures, densities, and proton fractions for use in supernovae, neutron star mergers, and black hole formation simulations. We employ full relativistic mean field (RMF) calculations for matter at intermediate density and high density, and the Virial expansion of a non-ideal gas for matter at low density. For this EOS we use the RMF effective interaction FSUGold, whereas our earlier EOS was based on the RMF effective interaction NL3. The FSUGold interaction has a lower pressure at high densities compared to the NL3 interaction. We calculate the resulting EOS at over 100,000 grid points in the temperature range $T$ = 0 to 80 MeV, the density range $n_B$ = 10$^{-8}$ to 1.6 fm$^{-3}$, and the proton fraction range $Y_p$ = 0 to 0.56. We then interpolate these data points using a suitable scheme to generate a thermodynamically consistent equation of state table on a finer grid. We discuss differences between this EOS, our NL3 based EOS, and previous EOSs by Lattimer-Swesty and H. Shen et al for the thermodynamic properties, composition, and neutron star structure. The original FSUGold interaction produces an EOS, that we call FSU1.7, that has a maximum neutron star mass of 1.7 solar masses. A modification in the high density EOS is introduced to increase the maximum neutron star mass to 2.1 solar masses and results in a slightly different EOS that we call FSU2.1. The EOS tables for FSU1.7 and FSU2.1 are available for download.Comment: updated version according to referee's comments. Phys. Rev. C in pres

Free vibrations of delaminated beams

Free vibration of laminated composite beams is studied. The effect of interply delaminations on natural frequencies and mode shapes is evaluated both analytically and experimentally. A generalized vibrational principle is used to formulate the equation of motion and associated boundary conditions for the free vibration of a composite beam with a delamination of arbitrary size and location. The effect of coupling between longitudinal vibration and bending vibration is considered. This coupling effect is shown to significantly affect the calculated natural frequencies and mode shapes of the delaminated beam

Lowest eigenvalue of the nuclear shell model Hamiltonian

In this paper we investigate regular patterns of matrix elements of the nuclear shell model Hamiltonian $H$, by sorting the diagonal matrix elements from the smaller to larger values. By using simple plots of non-zero matrix elements and lowest eigenvalues of artificially constructed "sub-matrices" $h$ of $H$, we propose a new and simple formula which predicts the lowest eigenvalue with remarkable precisions.Comment: six pages, four figures, Physical Review C, in pres

Tunable coupling scheme for flux qubits at the optimal point

We discuss a practical design for tunably coupling a pair of flux qubits via the quantum inductance of a third high-frequency qubit. The design is particularly well suited for realizing a recently proposed microwave-induced parametric coupling scheme. This is attractive because the qubits can always remain at their optimal points. Furthermore, we will show that the resulting coupling also has an optimal point where it is insensitive to low-frequency flux noise. This is an important feature for the coherence of coupled qubits. The presented scheme is an experimentally realistic way of carrying out two-qubit gates and should be easily extended to multiqubit systems.Comment: 8 pages, 6 figures, minor change

Development of high critical current density in multifilamentary round-wire Bi2Sr2CaCu2O8+x by strong overdoping

Bi2Sr2CaCu2O8+x is the only cuprate superconductor that can be made into a round-wire conductor form with a high enough critical current density Jc for applications. Here we show that the Jc(5 T,4.2 K) of such Ag-sheathed filamentary wires can be doubled to more than 1.4x10^5 A/cm^2 by low temperature oxygenation. Careful analysis shows that the improved performance is associated with a 12 K reduction in transition temperature Tc to 80 K and a significant enhancement in intergranular connectivity. In spite of the macroscopically untextured nature of the wire, overdoping is highly effective in producing high Jc values.Comment: 4 figure

Unconventional magnetic phase separation in γ\gamma-CoV2_2O6_6

We have explored the magnetism in the non-geometrically frustrated spin-chain system $\gamma$-CoV$_{2}$O$_{6}$ which possesses a complex magnetic exchange network. Our neutron diffraction patterns at low temperatures ($T$ $\leqslant$ $T_{\mathrm{N}}$ = 6.6 K) are best described by a model in which two magnetic phases coexist in a volume ratio 65(1) : 35(1), with each phase consisting of a single spin modulation. This model fits previous studies and our observations better than the model proposed by Lenertz $et$ $al$ in J. Phys. Chem. C 118, 13981 (2014), which consisted of one phase with two spin modulations. By decreasing the temperature from $T_{\mathrm{N}}$, the minority phase of our model undergoes an incommensurate-commensurate lock-in transition at $T^{*}$ = 5.6 K. Based on these results, we propose that phase separation is an alternative approach for degeneracy-lifting in frustrated magnets

High Resolution VSOP Imaging of a Southern Blazar PKS 1921-293 at 1.6 GHz

We present a high resolution 1.6 GHz VSOP image of the southern blazar PKS 1921-293. The image shows a typical core-jet morphology, consistent with ground-based VLBI images. However, the addition of data from the space antenna has greatly improved the angular resolution (especially along the north-south direction for this source), and thus allowed us to clearly identify the core. Model fitting reveals an inner jet component ~1.5 mas north of the core. This jet feature may be moving on a common curved path connecting the jet within a few parsecs to the 10-parsec-scale jet. The compact core has a brightness temperature of 2.6*10**12 K (in the rest frame of the quasar), an indication of relativistic beaming. We analyzed the source in terms of three models, involving the inverse Compton catastrophe, an inhomogeneous relativistic jet, and the equipartition of energy between the radiating particles and the magnetic field. Our analysis of this gamma-ray-quiet blazar shows no preference to any particular one of these models.Comment: 7 pages including 2 figures and 1 table, PASJLaTeX, accepted for publication in PAS

The Destruction of Bars by Central Mass Concentrations

More than two thirds of disk galaxies are barred to some degree. Many today harbor massive concentrations of gas in their centers, and some are known to possess supermassive black holes (SMBHs) and their associated stellar cusps. Previous theoretical work has suggested that a bar in a galaxy could be dissolved by the formation of a mass concentration in the center, although the precise mass and degree of central concentration required is not well-established. We report an extensive study of the effects of central masses on bars in high-quality N-body simulations of galaxies. We have varied the growth rate of the central mass, its final mass and degree of concentration to examine how these factors affect the evolution of the bar. Our main conclusions are: (1) Bars are more robust than previously thought. The central mass has to be as large as several percent of the disk mass to completely destroy the bar on a short timescale. (2) For a given mass, dense objects cause the greatest reduction in bar amplitude, while significantly more diffuse objects have a lesser effect. (3) The bar amplitude always decreases as the central mass is grown, and continues to decay thereafter on a cosmological time-scale. (4) The first phase of bar-weakening is due to the destruction by the CMC of lower-energy, bar-supporting orbits, while the second phase is a consequence of secular changes to the global potential which further diminish the number of bar-supporting orbits. We provide detailed phase-space and orbit analysis to support this suggestion. Thus current masses of SMBHs are probably too small, even when dressed with a stellar cusp, to affect the bar in their host galaxies. The molecular gas concentrations found in some barred galaxies are also too diffuse to affect the amplitude of the bar significantly.Comment: AASTeX v5.0 preprint; 44 pages, including 1 table and 16 figures. To appear in ApJ. High resolution version can be found at http://www.physics.rutgers.edu/~shen/bar_destruct/paper_high_res.pd