An automated system for creep testing

A completely automated data collection system was devised to measure, analyze, and graph creep versus time using a PC, a 16 channel multiplexed analog to digital converter, and low friction potentiometers to measure length. The sampling rate for each experiment can be adjusted in the software to meet the needs of the material tested. Data is collected and stored on a diskette for permanent record and also for later data analysis on a different machine

Renyi Entropy and Parity Oscillations of the Anisotropic Spin-s Heisenberg Chains in a Magnetic Field

Using the density matrix renormalization group, we investigate the Renyi entropy of the anisotropic spin-s Heisenberg chains in a z-magnetic field. We considered the half-odd integer spin-s chains, with s=1/2,3/2 and 5/2, and periodic and open boundary conditions. In the case of the spin-1/2 chain we were able to obtain accurate estimates of the new parity exponents $p_{\alpha}^{(p)}$ and $p_{\alpha}^{(o)}$ that gives the power-law decay of the oscillations of the $\alpha-$Renyi entropy for periodic and open boundary conditions, respectively. We confirm the relations of these exponents with the Luttinger parameter $K$, as proposed by Calabrese et al. [Phys. Rev. Lett. 104, 095701 (2010)]. Moreover, the predicted periodicity of the oscillating term was also observed for some non-zero values of the magnetization $m$. We show that for $s>1/2$ the amplitudes of the oscillations are quite small, and get accurate estimates of $p_{\alpha}^{(p)}$ and $p_{\alpha}^{(o)}$ become a challenge. Although our estimates of the new universal exponents $p_{\alpha}^{(p)}$ and $p_{\alpha}^{(o)}$ for the spin-3/2 chain are not so accurate, they are consistent with the theoretical predictions.Comment: revised version, accepted to PRB. 9 pages, 3 Figures, 4 Table