Spin diffusion of the t-J model

The spin-diffusion constant of the 2D $t-J$ model is calculated for the first time using an analytical approach at high temperatures and a recently-developed numerical method based on the Lanczos technique combined with random sampling in the intermediate temperature regime. A simple relation, $\sigma = D_s\chi$, between spin conductivity and spin diffusion is established and used to calculate the latter. In the high-temperature and low-doping limit the calculated diffusion constant agrees with known results for the Heisenberg model. At small hole doping, $D_s$ increases approximately linearly with doping, which leads us to an important conclusion that hopping processes enhance spin diffusion at high temperatures. At modest hole doping, $\delta\sim 0.25$, diffusion exhibits a nonmonotonic temperature dependence, which indicates anomalous spin dynamics at small frequencies.Comment: 12 pages with figure

Suppression of forward dilepton production from an anisotropic quark-gluon plasma

We calculate the rapidity dependence of leading-order medium dilepton yields resulting from a quark-gluon plasma which has a local time-dependent anisotropy in momentum space. We present a phenomenological model which includes temporal evolution of the plasma anisotropy parameter, xi, and the hard momentum scale, p_hard. Our model interpolates between 1+1 dimensional collisionally-broadened expansion at early times and 1+1 dimensional ideal hydrodynamic expansion at late times. Using our model, we find that at LHC energies, forward high-energy medium dilepton production would be suppressed by up to a factor of 3 if one assumes an isotropization/thermalization time of 2 fm/c. Therefore, it may be possible to use forward dilepton yields to experimentally determine the time of onset of locally isotropic hydrodynamic expansion of the quark-gluon plasma as produced in ultrarelativistic heavy-ion collisions.Comment: 12 pages, 5 figure

Spin-Orbit Couplinq Force for 14N Elastic Scattering

開始ページ、終了ページ: 冊子体のページ付