We study numerically the dynamic and spectral properties of a one-dimensional quasi-periodic system, where site energies are given by k = V cos 2πf x k with x k denoting the kth quasiperiodic lattice site. When 2πf is given by the reciprocal lattice vector G(m, n) with n and m being successive Fibonacci numbers, the variance of the wavepacket is found to grow quadratically in time, regardless of the potential strength V. For other values of f , there exists a critical value of V beyond which the growth of the wavepacket variance is bounded. In particular an anomalous diffusion takes place for 2πf corresponding to G(m, n) with generic integers m and n. The level-spacing distribution is also examined, and the corresponding exponent β is observed to decrease with V .
In this paper we give a full account of the work of William Thomson (Lord Kelvin) on absolute temperature, which to this day provides the theoretical underpinnings for the most rigorous measurements of temperature. When Thomson fashioned his concepts of 'absolute' temperature, his main concern was to make the definition of temperature independent of the properties of particular thermometric substances (rather than to count temperature from an absolute zero). He tried out a succession of definitions based on the thermodynamics of ideal heat engines; most notably, in 1854 he gave the ratio of two temperatures as the ratio of quantities of heat taken in and given out at those temperatures in a Carnot cycle. But there were difficulties with using such definitions for experimental work, since it was not possible even to approximate an ideal Carnot engine in reality. More generally, it is not trivial to connect an abstract concept with concrete operations in order to make physical measurements possible. In the end, Thomson argued that an ideal gas thermometer would indicate his absolute temperature, and that the deviation of actual gas thermometers from the ideal could be estimated by means of the JouleThomson effect. However, the measurement of the Joule-Thomson effect itself required measurements of temperature, so there was a problem of circularity.
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