Local dynamics of a randomly pinned crack front: A numerical study

We investigate numerically the dynamics of crack propagation along a weak plane using a model consisting of fibers connecting a soft and a hard clamp. This bottom-up model has previously been shown to contain the competition of two crack propagation mechanisms: coalescence of damage with the front on small scales and pinned elastic line motion on large scales. We investigate the dynamical scaling properties of the model, both on small and large scale. The model results compare favorable with experimental results

Snow and leverage

Using a sample of highly (over-)leveraged Austrian ski hotels undergoing debt restructurings, we show that reducing a debt overhang leads to a significant improvement in operating performance (return on assets, net profit margin). In particular, a reduction in leverage leads to a decrease in overhead costs, wages, and input costs, and to an increase in sales. Changes in leverage in the debt restructurings are instrumented with Unexpected Snow, which captures the extent to which a ski hotel experienced unusually good or bad snow conditions prior to the debt restructuring. Effectively, Unexpected Snow provides lending banks with the counterfactual of what would have been the ski hotel's operating performance in the absence of strategic default, thus allowing to distinguish between ski hotels that are in distress due to negative demand shocks ("liquidity defaulters") and ski hotels that are in distress due to debt overhang ("strategic defaulters")

Unequal Error Protection in BICM with QAM Constellations: Interleaver and Code Design

In this paper we present a general methodology for the interleaver and code design for QAM-based BICM transmissions. We develop analytical bounds on the bit error rate and we use them to predict the performance of BICM when unequal error protection (UEP) is introduced by the constellation labeling. Based on these bounds, the optimum design of interleaver and code is presented. The improvements obtained reached 2~dB for the analyzed cases, and are obtained without complexity increase. Although previous works noted the influence of the interleaver design and the UEP, to the best of our knowledge, this paper is the first to analyze formally this problem for BICM transmissions

Onset of Localization in Heterogeneous Interfacial Failure

We study numerically the failure of an interface joining two elastic materials under load using a fiber bundle model connected to an elastic half space. We find that the breakdown process follows the equal load sharing fiber bundle model without any detectable spatial correlations between the positions of the failing fibers until localization sets in. The onset of localization is an instability, not a phase transition. Depending on the elastic constant describing the elastic half space, localization sets in before or after the critical load causing the interface to fail completely, is reached. There is a crossover between failure due to localization or failure without spatial correlations when tuning the elastic constant, not a phase transition. Contrary to earlier claims based on models different from ours, we find that a finite fraction of fibers must fail before the critical load is attained, even in the extreme localization regime, i.e.\ for very small elastic constant. We furthermore find that the critical load remains finite for all values of the elastic constant in the limit of an infinitely large system.Comment: 4 pages, 5 figure

SU(3) Anderson impurity model: A numerical renormalization group approach exploiting non-Abelian symmetries

We show how the density-matrix numerical renormalization group (DM-NRG) method can be used in combination with non-Abelian symmetries such as SU(N), where the decomposition of the direct product of two irreducible representations requires the use of a so-called outer multiplicity label. We apply this scheme to the SU(3) symmetrical Anderson model, for which we analyze the finite size spectrum, determine local fermionic, spin, superconducting, and trion spectral functions, and also compute the temperature dependence of the conductance. Our calculations reveal a rich Fermi liquid structure.Comment: 18 pages, 9 figure

Snow and Leverage

Using a sample of highly (over-)leveraged Austrian ski hotels undergoing debt restructurings, we show that reducing a debt overhang leads to a significant improvement in operating performance (return on assets, net profit margin). In particular, a reduction in leverage leads to a decrease in overhead costs, wages, and input costs, and to an increase in sales. Changes in leverage in the debt restructurings are instrumented with Unexpected Snow , which captures the extent to which a ski hotel experienced unusually good or bad snow conditions prior to the debt restructuring. Effectively, Unexpected Snow provides lending banks with the counterfactual of what would have been the ski hotel’s operating performance in the absence of strategic default, thus allowing to distinguish between ski hotels that are in distress due to negative demand shocks (“liquidity defaulters”) and ski hotels that are in distress due to debt overhang (“strategic defaulters”).