Four-dimensional CP1+^1+ U(1) lattice gauge theory for 3D antiferromagnets: Phase structure, gauge bosons and spin liquid

In this paper we study the lattice CP$^1$ model in (3+1) dimensions coupled with a dynamical compact U(1) gauge field. This model is an effective field theory of the $s={1 \over 2}$ antiferromagnetic Heisenberg spin model in three spatial dimensions. By means of Monte Carlo simulations, we investigate its phase structure. There exist the Higgs, Coulomb and confinement phases, and the parameter regions of these phases are clarified. We also measure magnetization of O(3) spins, energy gap of spin excitations, and mass of gauge boson. Then we discuss the relationship between these three phases and magnetic properties of the high-$T_{\rm c}$ cuprates, in particular the possibility of deconfined-spinon phase. Effect of dimer-like spin exchange coupling and ring-exchange coupling is also studied.Comment: 4pages, 10 figure

Evaluation of the region 1 field-aligned current from the low-latitude boundary layer using the 1989 Tsyganenko model

On the basis of the 1989 Tsyganenko magnetic field model, the field-aligned current (FAC) density distribution in the low-latitude boundary layer (LLBL) is numerically evaluated by assuming the entry of magnetosheath particles into the LLBL. The calculated FAC density/intensity profiles are consistent with observations. This FAC generation arises from the divergence of the magnetic drift current density carried by LLBL particles, and the current intensity is then increased with their kinetic energy density. The FAC generation occurs at the inner edge of the LLBL whenever sheath particles penetrate into the magnetosphere, regardless of the entry process. It is also emphasized that the LLBL FAC production is an inevitable consequence of the formation of the magnetopause, because the magnetopause currents act to shield the magnetic field originating from the currents inside the closed region of the magnetosphere, causing the LLBL inner edge to intersect the magnetic drift paths. This simple situation can be illustrated by calculating the distribution of the flux tube volume in the Tsyganenko model

Distortion of the nightside boundary of the "firmly-closed" region in the 1996 Tsyganenko magnetic field model

This paper proposes that the outer boundary of the "firmly-closed" region should be represented by field lines with the adiabaticity parameter, K, equal to unity at the equator, where K^2 is the ratio between the radius of the field-line curvature and the Larmor radius of an ion with 1 keV of energy. Just outside the boundary where K = 1, plasma particles (primarily ions) can be nonadiabatically accelerated in the presence of the dawn-to-dusk electric field. An inwardly convecting flux tube will attain the maximum content of nonadiabatically accelerated particles when it passes the K - 1 boundary. Thus, the K = 1 boundary outlines the region of the plasma population with a maximum content of nonadiabatically accelerated particles. In addition, the field lines with K = 1 are shown to have a minimum field strength of roughly 1 nT at the equator. From this fact, a field line with k < 1 may not be considered as being "firmly-closed" in the sense that such a field line may easily merge with an interplanetary field line. The outer boundary of the nightside firmly-closed region in the Tsyganenko model has an IMF Bz dependence that is consistent with observations. Moreover, this boundary is found to be "distorted", favoring the generation of region 1 field-aligned currents

Latitudinal structure of the nightside region 1 field-aligned current observed from the EXOS-D satellite

The average pattern of region 1 field-aligned current (FAC) of IIJIMA and POTEMRA (J. Geophys. Res., 81, 2165, 1976a; J. Geophys. Res., 83, 599, 1978) spans 2-3° in magnetic latitude. Using the magnetic field data acquired with the EXOS-D satellite, we notice that sharp variations of magnetic field perturbation, showing the high current densities of several micro-amperes per squared meter at the ionospheric height, are included in the region 1 current zone. In this paper, we focus our analysis on a sharp gradient of magnetic field change within 1° in latitude. In the 20-04 MLT sector, the thin current sheet as an important part of the region 1 FAC system is often found to be just equatorward of the boundary FAC system (FuKUNism et al, J. Geophys. Res., 98, 11235, 1993). A statistical survey of more than 200 satellite\u27s crossings of the region 1 zone (in the 17-05 MLT range) shows that about 60% of the identified region 1 current systems have the latitudinal structure of a thin (on average, 0.5°) current sheet with current intensity greater than one third of the total FAC intensity of the region 1 system

Searching for a Companion Star of Tycho's Type Ia Supernova with Optical Spectroscopic Observations

We report our first results of photometric and spectroscopic observations for Tycho's supernova remnant (SNR Tycho) to search for the companion star of a type Ia supernova (SN Ia). From photometric observations using Suprime-Cam on the Subaru Telescope, we have picked up stars brighter than 22 mag (in $V$-band) for spectroscopy, which are located within a circular region with the radius of 30" around the center of SNR Tycho. If the ejecta of young supernova remnants, such as SNR Tycho, have a sufficient amount of Fe I, we should be able to detect absorption lines at 3720 \AA and 3860 \AA associated with transitions from the ground state of Fe I in the spectrum of the companion star. To identify the companion star of a SN Ia using these characteristic absorption lines of Fe I, we made optical low-resolution spectroscopy of their targets using FOCAS on the Subaru Telescope. In our spectroscopic observations, we obtained spectra of 17 stars in the SNR Tycho region and compare them with template stellar spectra. We detect significant absorption lines from two stars at 3720 \AA. Since widths of their absorption lines are broad, it is likely that the detected absorptions are due to Fe I in the expanding ejecta of SNR Tycho. However, none of stars exhibits a clear red wing in the observed profiles of the absorption, though a star in the background of the SNR should show it. Hence, we suggest another interpretation that the detected absorption lines might be caused by the peculiarity of stars. A star named Tycho(E) has the absorption line at 3720 \AA and its projected position is close to the center of SNR Tycho. Based on our observations, Tycho(E) is a new candidate as the companion star of Tycho's supernova.Comment: 17 pages, 28 figures, accepted for publication in PAS

Distortion of the outer boundary of the closed region in the Tsyganenko magnetic field model

Using the Tsyganenko magnetic field model (TSYGANENKO, Planet. Space Sci., 37, 5, 1989) we make an attempt to determine the outer boundary of the closed region when the interplanetary magnetic field (IMF) is southward. As a simple magnetic field model including the effect of IMF B_z<0, the B_z component of a constant value of minus a few nanoTeslas is added to the magnetic field in the Tsyganenko model with low K_p values. In this paper, if the magnetic field strength, B, is not less than 2 nT in the whole range of a field line (namely the minimum B along a field line is greater than 2 nT), this field line is judged to be "firmly" closed. The firmly closed field lines are thought to be definitely closed as long as the fluctuation amplitude of B_z (around its average level) in the interplanetary (solar wind) magnetic field is less than 2 nT. The outer boundary of the firmly closed region is then constituted by field lines with the minimum B of 2 nT. This boundary is found to be close to (just inside of) the open-closed boundary, which can be determined with accuracy of 0.01° in latitude of the foot point of a field line. It is found that a circle with the center at a latitude of about 85° on the midnight meridian can be fitted to the outer boundary of the firmly closed region, as it is projected to the ionosphere. Interestingly this circle coincides with a typical auroral circle; the auroral circles are those delineating the poleward boundary of the quiet auroral belt, which were earlier identified from the statistical analysis of satellites\u27 auroral images by MENG et al. (J. Geophys. Res., 82, 164, 1977). Importantly we find that the outer boundary of the firmly closed region is "distorted" on the nightside in the sense that the ionospheric projection of the average magnetic drift velocity of a plasma with isotropic pressure is not parallel to the boundary; more specifically, that of an isotropic ion fluid has an equatorward component on the duskside boundary and a poleward one on the dawnside boundary, respectively. This kind of the boundary distortion may be one of the possible causes of the generation of the nightside region 1 field-aligned current, which has been first suggested by HRUSKA (J. Geophys. Res., 91, 371, 1986) and recently, further studied by YAMAMOTO and INOUE (Proc. NIPR Symp. Upper Atmos. Phys., 11, 106, 1998)

TGF-β1 and IL-4 induce CCL11 production

Transforming growth factor (TGF)-β1 is a multifunctional cytokine, which can control certain functions of various kinds of cells. However, it is unclear whether TGF-β1 affects T-cell migration in periodontal lesions. The aim of this study was to examine the effects of TGF-β1 on the production of C-C chemokine ligand (CCL)11, which is a T-helper 2-type chemokine, in human periodontal ligament cells (HPDLC). Interleukin (IL)-4 induced CCL11 production, but TGF-β1 did not, in HPDLC. However, TGF-β1 enhanced CCL11 production in IL-4-stimulated HPDLC. Western blot analysis showed that the signal transducer and activator of transcription 6 (STAT6) pathway was highly activated in HPDLC that had been stimulated with both IL-4 and TGF-β1. Mitogen-activated protein kinase activation did not differ between the HPDLC treated with a combination of IL-4 and TGF-β1 and those treated with IL-4 or TGF-β1 alone. Moreover, a STAT6 inhibitor significantly inhibited CCL11 production in HPDLC that had been stimulated with IL-4 and TGF-β1. The current study clearly demonstrated that TGF-β1 enhanced IL-4-induced CCL11 production in HPDLC. The STAT6 pathway is important for CCL11 production in IL-4- and TGF-β1-treated HPDLC

The Polymethoxy Flavonoid Sudachitin Inhibits Interleukin-1β-Induced Inflammatory Mediator Production in Human Periodontal Ligament Cells

Sudachitin, which is a polymethoxylated flavonoid found in the peel of Citrus sudachi, has some biological activities. However, the effect of sudachitin on periodontal resident cells is still uncertain. The aim of this study was to examine if sudachitin could decrease the expression of inflammatory mediators such as cytokines, chemokines, or matrix metalloproteinase (MMP) in interleukin- (IL-) 1β-stimulated human periodontal ligament cells (HPDLC). Sudachitin inhibited IL-1β-induced IL-6, IL-8, CXC chemokine ligand (CXCL)10, CC chemokine ligand (CCL)2, MMP-1, and MMP-3 production in HPDLC. On the other hand, tissue inhibitor of metalloproteinase- (TIMP-) 1 expression was increased by sudachitin treatment. Moreover, we found that the nuclear factor- (NF-) κB and protein kinase B (Akt) pathways in the IL-1β-stimulated HPDLC were inhibited by sudachitin treatment. These findings indicate that sudachitin is able to reduce inflammatory mediator production in IL-1β-stimulated HPDLC by inhibiting NF-κB and Akt pathways