Partition function of the Potts model on self-similar lattices as a dynamical system and multiple transitions

We present an analytic study of the Potts model partition function on two different types of self-similar lattices of triangular shape with non integer Hausdorff dimension. Both types of lattices analyzed here are interesting examples of non-trivial thermodynamics in less than two dimensions. First, the Sierpinski gasket is considered. It is shown that, by introducing suitable geometric coefficients, it is possible to reduce the computation of the partition function to a dynamical system, whose variables are directly connected to (the arising of) frustration on macroscopic scales, and to determine the possible phases of the system. The same method is then used to analyse the Hanoi graph. Again, dynamical system theory provides a very elegant way to determine the phase diagram of the system. Then, exploiting the analysis of the basins of attractions of the corresponding dynamical systems, we construct various examples of self-similar lattices with more than one critical temperature. These multiple critical temperatures correspond to crossing phases with different degrees of frustration.Comment: 16 pages, 12 figures, 1 table; title changed, references and discussion on multiple transitions adde

High Resolution Infrared Spectroscopy Techniques for Upper Atmospheric Measurements

Infrared heterodyne techniques were considered primarily for detecting molecules predicted to be present but not yet detected in the upper atmosphere

Photoluminescence-Based Current-Voltage Characterisation of Individual Subcells in Multi-Junction Devices

We demonstrate a photoluminescence based, contactless method to determine the current-voltage characteristics of the individual subcells in a multi-junction solar cell. The method, furthers known results for single junction devices and relies upon the reciprocity relation between the absorption and emission properties on a solar cell. Laser light with a suitable energy is used to excite carriers selectively in one junction and the internal voltages are deduced from the intensity of the resulting luminescence. The IV curves obtained this way on 1J, 2J and 6J devices are compared to those obtained using electroluminescence. Good agreement is obtained at high injection conditions while discrepancies at low injection are attributed to in-plane carrier transport

Electroweak corrections to the direct detection cross section of inert higgs dark matter

The inert higgs model is a minimal extension of the Standard Model that features a viable dark matter candidate, the so-called inert higgs ($H^0$). In this paper, we compute and analyze the dominant electroweak corrections to the direct detection cross section of dark matter within this model. These corrections arise from one-loop diagrams mediated by gauge bosons that, contrary to the tree-level result, do not depend on the unknown scalar coupling $\lambda$. We study in detail these contributions and show that they can modify in a significant way the prediction of the spin-independent direct detection cross section. In both viable regimes of the model, \mh and \mh\gtrsim 500 \gev, we find regions where the cross section at one-loop is much larger than at tree-level. We also demonstrate that, over the entire viable parameter space of this model, these new contributions bring the spin-independent cross section within the reach of future direct detection experiments.Comment: 16 pages, 11 figure