Description of Four-Body Breakup Reaction with the Method of Continuum-Discretized Coupled-Channels

We present a method for smoothing discrete breakup $S$-matrix elements calculated by the method of continuum-discretized coupled-channels (CDCC). This smoothing method makes it possible to apply CDCC to four-body breakup reactions. The reliability of the smoothing method is confirmed for two cases, $^{58}$Ni($d$, $p n$) at 80 MeV and the $E1$ transition of $^6$He. We apply CDCC with the smoothing method to $^6$He breakup reaction at 22.5 MeV. Multi-step breakup processes are found to be important.Comment: 19 pages, 7 figures, published in Progress of Theoretical Physic

Coulomb breakup effects on the elastic cross section of 6^6He+209^{209}Bi scattering near Coulomb barrier energies

We accurately analyze the $^6$He+$^{209}$Bi scattering at 19 and 22.5 MeV near the Coulomb barrier energy, using the continuum-discretized coupled-channels method (CDCC) based on the $n$+$n$+$^4$He+$^{209}$Bi four-body model. The three-body breakup continuum of $^6$He is discretized by diagonalizing the internal Hamiltonian of $^6$He in a space spanned by the Gaussian basis functions. The calculated elastic and total reaction cross sections are in good agreement with the experimental data, while the CDCC calculation based on the di-neutron model of $^6$He, i.e., the $^2n$+$^{4}$He+$^{209}$Bi three-body model, does not reproduce the data.Comment: 5 pages, 5 figures, uses REVTeX 4, submitted to Phys. Rev.

Effects of magnetism and doping on the electron-phonon coupling in BaFe2_{2}As2_{2}

We calculate the effect of local magnetic moments on the electron-phonon coupling in BaFe$_{2}$As$_{2}+\delta$ using the density functional perturbation theory. We show that the magnetism enhances the total electron-phonon coupling by $\sim 50$, up to $\lambda \lesssim 0.35$, still not enough to explain the high critical temperature, but strong enough to have a non-negligible effect on superconductivity, for instance, by frustrating the coupling with spin fluctuations and inducing order parameter nodes. The enhancement comes mostly from a renormalization of the electron-phonon matrix elements. We also investigate, in the rigid band approximation, the effect of doping, and find that $\lambda$ versus doping does not mirror the behavior of the density of states; while the latter decreases upon electron doping, the former does not, and even increases slightly.Comment: 4 pages, 3 figure

A Herschel Study of 24 micron-Selected AGNs and Their Host Galaxies

We present a sample of 290 24-micron-selected active galactic nuclei (AGNs) mostly at z ~ 0.3 -- 2.5, within 5.2 square degrees distributed as 25' X 25' fields around each of 30 galaxy clusters in the Local Cluster Substructure Survey (LoCuSS). The sample is nearly complete to 1 mJy at 24 microns, and has a rich multi-wavelength set of ancillary data; 162 are detected by Herschel. We use spectral templates for AGNs, stellar populations, and infrared emission by star forming galaxies to decompose the spectral energy distributions (SEDs) of these AGNs and their host galaxies, and estimate their star formation rates (SFRs), AGN luminosities, and host galaxy stellar masses. The set of templates is relatively simple: a standard Type-1 quasar template; another for the photospheric output of the stellar population; and a far infrared star-forming template. For the Type-2 AGN SEDs, we substitute templates including internal obscuration, and some Type-1 objects require a warm component (T > 50 K). The individually Herschel- detected Type-1 AGNs and a subset of 17 Type-2 ones typically have luminosities > 10^{45} ergs/s, and supermassive black holes of ~ 3 X 10^8 Msun emitting at ~ 10% of the Eddington rate. We find them in about twice the numbers of AGN identified in SDSS data in the same fields, i.e., they represent typical high luminosity AGN, not an infrared-selected minority. These AGNs and their host galaxies are studied further in an accompanying paper

PhoSim-NIRCam: Photon-by-photon image simulations of the James Webb Space Telescope's Near-Infrared Camera

Recent instrumentation projects have allocated resources to develop codes for simulating astronomical images. Novel physics-based models are essential for understanding telescope, instrument, and environmental systematics in observations. A deep understanding of these systematics is especially important in the context of weak gravitational lensing, galaxy morphology, and other sensitive measurements. In this work, we present an adaptation of a physics-based ab initio image simulator: The Photon Simulator (PhoSim). We modify PhoSim for use with the Near-Infrared Camera (NIRCam) -- the primary imaging instrument aboard the James Webb Space Telescope (JWST). This photon Monte Carlo code replicates the observational catalog, telescope and camera optics, detector physics, and readout modes/electronics. Importantly, PhoSim-NIRCam simulates both geometric aberration and diffraction across the field of view. Full field- and wavelength-dependent point spread functions are presented. Simulated images of an extragalactic field are presented. Extensive validation is planned during in-orbit commissioning

Macroscopic Quantum Dynamics of a Free Domain Wall in a Ferromagnet

We study macroscopic quantum dynamics of a free domain wall in a quasi-one-dimensional ferromagnet by use of the spin-coherent-state path integral in {\it discrete-time} formalism. Transition amplitudes between typical states are quantitatively discussed by use of {\it stationary-action approximation} with respect to collective degrees of freedom representing the center position and the chirality of the domain wall. It is shown that the chirality may be loosely said to be canonically conjugate to the center position; the latter moves with a speed depending on the former. It is clarified under what condition the center position can be regarded as an effective free-particle position, which exhibits the phenomenon of wave-packet spreading. We demonstrate, however, that in some case the non-linear character of the spin leads to such a dramatic phenomenon of a non-spreading wave packet as to completely invalidate the free-particle analogy. In the course of the discussion, we also point out various difficulties associated with the continuous-time formalism.Comment: 23 pages, REVTEX, 4 figures, submitted to Phys. Rev.