5,533 research outputs found
The Hamilton-Jacobi Approach to Teleparallelism
We intend to analyse the constraint structure of Teleparallelism employing
the Hamilton-Jacobi formalism for singular systems. This study is conducted
without using an ADM 3+1 decomposition and without fixing time gauge condition.
It can be verified that the field equations constitute an integrable system.Comment: 12 pages, no figur
Destruction of long-range antiferromagnetic order by hole doping
We study the renormalization of the staggered magnetization of a
two-dimensional antiferromagnet as a function of hole doping, in the framework
of the t-J model. It is shown that the motion of holes generates decay of spin
waves into ''particle-hole'' pairs, which causes the destruction of the
long-range magnetic order at a small hole concentration. This effect is mainly
determined by the coherent motion of holes. The value obtained for the critical
hole concentration, of a few percent, is consistent with experimental data for
the doped copper oxide high-Tc superconductors.Comment: 12 pages, 2 figure
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Composite polymer membranes for laserinduced fluorescence thermometry
We demonstrate a modified version of laser-induced fluorescence thermometry (LIFT) for mapping temperature gradients in the vicinity of small photothermal devices. Our approach is based on temperature sensitive fluorescent membranes fabricated with rhodamine B and polydimethylsiloxane (PDMS). Relevant membrane features for LIFT, such as temperature sensitivity, thermal quenching and photobleaching are presented for a range of 25 °C to 90 °C, and their performance is evaluated upon obtaining the temperature gradients produced in the proximity of optical fiber micro-heaters. Our results show that temperature measurements in regions as small as 750 μm x 650 μm, with a temperature resolution of 1 °C, can be readily obtained
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