Localization length of a soliton from a non-magnetic impurity in a general double-spin-chain model

A localization length of a free-spin soliton from a non-magnetic impurity is deduced in a general double-spin-chain model ($J_0-J_1-J_2-J_3$ model). We have solved a variational problem which employs the nearest-neighbor singlet-dimer basis. The wave function of a soliton is expressed by the Airy function, and the localization length $(\xi)$ is found to obey a power law of the dimerization $(J_2-J_3)$ with an exponent -1/3; $\xi\sim (J_2-J_3)^{-1/3}$. This explains why NaV_2O_5 does not show the antiferromagnetic order, while CuGeO_3 does by impurity doping. When the gap exists by the bond-dimerization, a soliton is localized and no order is expected. Contrary, there is a possibility of the order when the gap is mainly due to frustration.Comment: 4 pages, REVTeX, Figures are in eps-file

Solid motor diagnostic instrumentation

A review of typical surveillance and monitoring practices followed during the flight phases of representative solid-propellant upper stages and apogee motors was conducted to evaluate the need for improved flight diagnostic instrumentation on future spacecraft. The capabilities of the flight instrumentation package were limited to the detection of whether or not the solid motor was the cause of failure and to the identification of probable primary failure modes. Conceptual designs of self-contained flight instrumentation packages capable of meeting these reqirements were generated and their performance, typical cost, and unit characteristics determined. Comparisons of a continuous real time and a thresholded hybrid design were made on the basis of performance, mass, power, cost, and expected life. The results of this analysis substantiated the feasibility of a self-contained independent flight instrumentation module as well as the existence of performance margins by which to exploit growth option applications

M87 black hole mass and spin estimate through the position of the jet boundary shape break

We propose a new method of estimating a mass of a super massive black hole residing in the center of an active galaxy. The active galaxy M87 offers a convenient test case for the method due to the existence of a large amount of observational data on the jet and ambient environment properties in the central area of the object. We suggest that the observed transition of a jet boundary shape from a parabolic to a conical form is associated with the flow transiting from the magnetically dominated regime to the energy equipartition between plasma bulk motion and magnetic field. By coupling the unique set of observations available for the jet kinematics, environment and boundary profile with our MHD modelling under assumption on the presence of a dynamically important magnetic field in the M87 jet, we estimate the central black hole mass and spin. The method leads us to believe that the M87 super massive black hole has a mass somewhat larger than typically accepted so far.Comment: 10 pages, 1 figure, 3 tables, accepted for publication by MNRA

Vanishing of the negative-sign problem of quantum Monte Carlo simulations in one-dimensional frustrated spin systems

The negative-sign problem in one-dimensional frustrated quantum spin systems is solved. We can remove negative signs of the local Boltzmann weights by using a dimer basis that has the spin-reversal symmetry. Validity of this new basis is checked in a general frustrated double-spin-chain system, namely the J_0-J_1-J_2-J_3 model. The negative sign vanishes perfectly for $J_0 + J_1 \leq J_3$.Comment: 4 pages, REVTeX, 4 figures in eps-file

Microlensing of collimated Gamma-Ray Burst afterglows

We investigate stellar microlensing of the collimated gamma-ray burst afterglows. A spherical afterglow appears on the sky as a superluminally expanding thin ring (``ring-like'' image), which is maximally amplified as it crosses the lens. We find that the image of the collimated afterglow becomes quite uniform (``disk-like'' image) after the jet break time (after the Lorentz factor of the jet drops below the inverse of the jet opening angle). Consequently, the amplification peak in the light curve after the break time is lower and broader. Therefore detailed monitoring of the amplification history will be able to test whether the afterglows are jets or not, i.e., ``disk-like'' or not, if the lensing occurs after the break time. We also show that some proper motion and polarization is expected, peaking around the maximum amplification. The simultaneous detection of the proper motion and the polarization will strengthen that the brightening of the light curve is due to microlensing.Comment: 16 pages, 6 figures, accepted for publication in Ap

Temperature-driven transition from the Wigner Crystal to the Bond-Charge-Density Wave in the Quasi-One-Dimensional Quarter-Filled band

It is known that within the interacting electron model Hamiltonian for the one-dimensional 1/4-filled band, the singlet ground state is a Wigner crystal only if the nearest neighbor electron-electron repulsion is larger than a critical value. We show that this critical nearest neighbor Coulomb interaction is different for each spin subspace, with the critical value decreasing with increasing spin. As a consequence, with the lowering of temperature, there can occur a transition from a Wigner crystal charge-ordered state to a spin-Peierls state that is a Bond-Charge-Density Wave with charge occupancies different from the Wigner crystal. This transition is possible because spin excitations from the spin-Peierls state in the 1/4-filled band are necessarily accompanied by changes in site charge densities. We apply our theory to the 1/4-filled band quasi-one-dimensional organic charge-transfer solids in general and to 2:1 tetramethyltetrathiafulvalene (TMTTF) and tetramethyltetraselenafulvalene (TMTSF) cationic salts in particular. We believe that many recent experiments strongly indicate the Wigner crystal to Bond-Charge-Density Wave transition in several members of the TMTTF family. We explain the occurrence of two different antiferromagnetic phases but a single spin-Peierls state in the generic phase diagram for the 2:1 cationic solids. The antiferromagnetic phases can have either the Wigner crystal or the Bond-Charge-Spin-Density Wave charge occupancies. The spin-Peierls state is always a Bond-Charge-Density Wave.Comment: 12 pages, 8 EPS figures. Longer version of previous manuscript. Contains new numerical data as well as greatly expanded discussio

Consistency between renormalization group running of chiral operator and counting rule -- Case of chiral pion production operator --

In nuclear chiral perturbation theory (ChPT), an operator is defined in a space with a cutoff which may be varied within a certain range. The operator runs as a result of the variation of the cutoff [renormalization group (RG) running]. In order for ChPT to be useful, the operator should run in a way consistent with the counting rule; that is, the running of chiral counter terms have to be of natural size. We vary the cutoff using the Wilsonian renormalization group (WRG) equation, and examine this consistency. As an example, we study the s-wave pion production operator for NN\to d pi, derived in ChPT. We demonstrate that the WRG running does not generate any chiral-symmetry-violating (CSV) interaction, provided that we start with an operator which does not contain a CSV term. We analytically show how the counter terms are generated in the WRG running in case of the infinitesimal cutoff reduction. Based on the analytic result, we argue a range of the cutoff variation for which the running of the counter terms is of natural size. Then, we numerically confirm this.Comment: 28 pages, 5 figures, significantly changed, published versio

Effect of magnetic field on the phase transition in a dusty plasma

The formation of self-consistent crystalline structure is a well-known phenomenon in complex plasmas. In most experiments the pressure and rf power are the main controlling parameters in determining the phase of the system. We have studied the effect of externally applied magnetic field on the configuration of plasma crystals, suspended in the sheath of a radio-frequency discharge using the Magnetized Dusty Plasma Experiment (MDPX) device. Experiments are performed at a fixed pressure and rf power where a crystalline structure is formed within a confining ring. The magnetic field is then increased from 0 to 1.28 T. We report on the breakdown of the crystalline structure with increasing magnetic field. The magnetic field affects the dynamics of the plasma particles and first leads to a rotation of the crystal. At higher magnetic field, there is a radial variation (shear) in the angular velocity of the moving particles which we believe leads to the melting of the crystal. This melting is confirmed by evaluating the variation of the pair correlation function as a function of magnetic field.Comment: 9 pages, 5 figure

Is rejection a diffuse or localized process in small-bowel transplantation?

Utilization of endoscopy to both visualize and selectively biopsy an intestinal allograft has become the standard for early recognition and treatment of intestinal allograft rejection. Despite the widespread acceptance of the need for selective mucosal biopsies, it has not been shown that the histological features of intestinal allograft rejection are either localized or occur as part of a more diffuse phenomenon within a tubular allograft. To resolve these issues, 88 ileoscopies were performed in 12 small-bowel allograft recipients and mucosal biopsy samples were obtained at 5, 10, and 15 cm, respectively, from the ileal stoma. Each mucosal biopsy was labeled, processed, and evaluated individually for the presence and severity of any evidence for allograft rejection. The data obtained suggest that intestinal allograft rejection is a diffuse process, and biopsies obtained randomly from an ileal graft are likely to demonstrate evidence of allograft rejection when such is present. © 1994 Springer-Verlag New York Inc