Finite volume study of electric polarizabilities from lattice QCD

Knowledge of the electric polarizability is crucial to understanding the interactions of hadrons with electromagnetic fields. The neutron polarizability is very sensitive to the quark mass and is expected to diverge in the chiral limit. Here we present results for the electric polarizability of the neutron, neutral pion, and neutral kaon on eight ensembles with nHYP-smeared clover dynamical fermions with two different pion masses (227 and 306 MeV). These are currently the lightest pion masses used in polarizability studies. For each pion mass we compute the polarizability at four different volumes and perform an infinite volume extrapolation for the three hadrons. Along with the infinite volume extrapolation we conduct a chiral extrapolation for the kaon polarizability to the physical point. We compare our results for the neutron polarizability to predictions from chiral perturbation theory.Comment: 7 pages, 11 figure

Incommensurate spin density wave in Co-doped BaFe2As2

57Fe Mossbauer spectroscopy measurements are presented in the underdoped Ba(Fe{1-x}Cox)2As2 series for x=0.014 (T_c < 1.4K) and x=0.03 and 0.045 (T_c ~ 2 and 12K respectively). The spectral shapes in the so-called spin-density wave (SDW) phase are interpreted in terms of incommensurate modulation of the magnetic structure, and allow the shape of the modulation to be determined. In undoped BaFe2As2, the magnetic structure is commensurate, and we find that incommensurability is present at the lowest doping level (x=0.014). As Co doping increases, the low temperature modulation progressively loses its "squaredness" and tends to a sine-wave. The same trend occurs for a given doping level, as temperature increases. We find that a magnetic hyperfine component persists far above the SDW transition, its intensity being progressively tranferred to a paramagnetic component on heating.Comment: 7 pages, 8 figures, published in EP

Impurity Scattering of Wave Packets on a Lattice

Quantum transport in a lattice is distinct from its counterpart in continuum media. Even a free wave packet travels differently in a lattice than in the continuum. We describe quantum scattering in a one dimensional lattice using three different formulations and illustrate characteristics of quantum transport such as resonant transmission. We demonstrate the real time propagation of a wave packet and its phase shift due to impurity configurations. Spin-flip scattering is also taken into account in a spin chain system. We show how individual spins in the chain evolve as a result of a spin-flip interaction between an incoming electron and a spin chain.Comment: submitted to Phys. Rev.

Low lying yrast states of 32S

From angular correlation measurements with the 29Si(α, nγ) 32S reaction the 6 762-keV level has been assigned Jπ = 5-. Four new levels of 32S have been observed at Ex = 7 567-, 8 345-, 9 464- and 9 637-keV. The 7 567-keV level has been assigned Jπ = 5+ and the 8 345-keV level is a good candidate for the lowest 6+ state. The two higher levels are probably negative parity high spin states

Magnetic Behavior in RRhX (R = rare earths; X=B, C) Compounds

We report on the magnetic behavior of RRhB (R = La, Ce, Pr, Nd, Gd, Tb and Tm) and RRhC (R = La, Ce, Pr and Gd) compounds crystallizing in the cubic perovskite type structure with space group Pm3m. The heat capacity data on Pauli-paramagnetic LaRhB and LaRhC indicate a high frequency vibrating motion of boron and carbon atoms in the unit cell. Ce is in -like nonmagnetic state in both the compounds. Pr compounds show a dominant crystal field effect with a nonmagnetic singlet ground state in PrRhB and a nonmagnetic quadrupolar doublet in PrRhC. Compounds with other rare earths order ferromagnetically at low temperatures except TmRhB in which the zero field evolution of magnetic interactions is relatively more complicated. The electrical resistivity of GdRhB decreases with increasing temperature in the paramagnetic state in the vicinity of T, which is rarely seen in ferromagnets. The behavior is discussed to be arising due to the short range spin fluctuation and a possible contribution from Fermi surface geometry.Comment: 14 Figs and a text fil

The HI and Ionized Gas Disk of the Seyfert Galaxy NGC 1144 = Arp 118: A Violently Interacting Galaxy with Peculiar Kinematics

We present observations of the distribution and kinematics of neutral and ionized gas in NGC 1144, a galaxy that forms part of the Arp 118 system. Ionized gas is present over a huge spread in velocity (1100 km/s) in the disk of NGC 1144, but HI emission is detected over only 1/3 of this velocity range, in an area that corresponds to the NW half of the disk. In the nuclear region of NGC 1144, a jump in velocity in the ionized gas component of 600 km/s is observed. Faint, narrow HI absorption lines are also detected against radio sources in the SE part of the disk of NGC 1144, which includes regions of massive star formation and a Seyfert nucleus. The peculiar HI distribution, which is concentrated in the NW disk, seems to be the inverse of the molecular distribution which is concentrated in the SE disk. Although this may partly be the result of the destruction of HI clouds in the SE disk, there is circumstantial evidence that the entire HI emission spectrum of NGC 1144 is affected by a deep nuclear absorption line covering a range of 600 km/s, and is likely blueshifted with respect to the nucleus. In this picture, a high column-density HI stream is associated with the nuclear ionized gas velocity discontinuity, and the absorption effectively masks any HI emission that would be present in the SE disk of NGC 1144.Comment: manuscript, arp118.ps: 28 pages; 1 Table: arp118.tab1.ps; 16 Figures: arp118.fig1-16.ps; Accepted to Ap

Information Horizons in Networks

We investigate and quantify the interplay between topology and ability to send specific signals in complex networks. We find that in a majority of investigated real-world networks the ability to communicate is favored by the network topology on small distances, but disfavored at larger distances. We further discuss how the ability to locate specific nodes can be improved if information associated to the overall traffic in the network is available.Comment: Submitted top PR