Exponential clogging time for a one dimensional DLA

When considering DLA on a cylinder it is natural to ask how many particles it takes to clog the cylinder, e.g. modeling clogging of arteries. In this note we formulate a very simple DLA clogging model and establish an exponential lower bound on the number of particles arriving before clogging appears

Second Wave Positive Psychology: Exploring the Positive–Negative Dialectics of Wellbeing

Positive psychology has tended to be defined in terms of a concern with ‘positive’ psychological qualities and states. However, critics of the field have highlighted various problems inherent in classifying phenomena as either ‘positive’ or ‘negative.’ For instance, ostensibly positive qualities (e.g., optimism) can sometimes be detrimental to wellbeing, whereas apparently negative processes (like anxiety) may at times be conducive to it. As such, over recent years, a more nuanced ‘second wave’ of positive psychology has been germinating, which explores the philosophical and conceptual complexities of the very idea of the ‘positive.’ The current paper introduces this emergent second wave by examining the ways in which the field is developing a more subtle understanding of the ‘dialectical’ nature of flourishing (i.e., involving a complex and dynamic interplay of positive and negative experiences). The paper does so by problematizing the notions of positive and negative through seven case studies, including five salient dichotomies (such as optimism versus pessimism) and two complex processes (posttraumatic growth and love). These case studies serve to highlight the type of critical, dialectical thinking that characterises this second wave, thereby outlining the contours of the evolving field

Frequency control of photonic crystal membrane resonators by mono-layer deposition

We study the response of GaAs photonic crystal membrane resonators to thin film deposition. Slow spectral shifts of the cavity mode of several nanometers are observed at low temperatures, caused by cryo-gettering of background molecules. Heating the membrane resets the drift and shielding will prevent drift altogether. In order to explore the drift as a tool to detect surface layers, or to intentionally shift the cavity resonance frequency, we studied the effect of self-assembled monolayers of polypeptide molecules attached to the membranes. The 2 nm thick monolayers lead to a discrete step in the resonance frequency and partially passivate the surface.Comment: 3 pages, 4 figures, submitted to Appl. Phys. Let

Partial Identification of Heterogeneity in Preference Orderings Over Discrete Choices

We study a variant of a random utility model that takes a probability distribution over preference relations as its primitive. We do not model products using a space of observed characteristics. The distribution of preferences is only partially identified using cross-sectional data on varying budget sets. Imposing monotonicity in product characteristics does not restore full identification. Using a linear programming approach to partial identification, we show how to obtain bounds on probabilities of any ordering relation. We also do constructively point identify the proportion of consumers who prefer one budget set over one or two others. This result is useful for welfare. Panel data and special regressors are two ways to gain full point identification.

Erratum: "Doppler Broadening and its Contribution to Compton Energy-Absorption Cross Sections: An Analysis of the Compton Component in Terms of Mass-Energy Absorption Coefficient" [J. Phys. Chem. Ref. Data <b>31</b>, 769 (2002)]

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Leader Election in Anonymous Rings: Franklin Goes Probabilistic

We present a probabilistic leader election algorithm for anonymous, bidirectional, asynchronous rings. It is based on an algorithm from Franklin, augmented with random identity selection, hop counters to detect identity clashes, and round numbers modulo 2. As a result, the algorithm is finite-state, so that various model checking techniques can be employed to verify its correctness, that is, eventually a unique leader is elected with probability one. We also sketch a formal correctness proof of the algorithm for rings with arbitrary size

Simultaneous Ad Auctions

We consider a model with two simultaneous VCG ad auctions A and B where each advertiser chooses to participate in a single ad auction. We prove the existence and uniqueness of a symmetric equilibrium in that model. Moreover, when the click rates in A are pointwise higher than those in B, we prove that the expected revenue in A is greater than the expected revenue in B in this equilibrium. In contrast, we show that this revenue ranking does not hold when advertisers can participate in both auctions

On the effect of adding epsilon-Bernoulli percolation to everywhere percolating subgraphs of Z^d

We show that adding epsilon-Bernoulli percolation to an everywhere percolating subgraph of Z^2 results in a graph which has large scale geometry similar to that of supercritical Bernoulli percolation, in various specific senses. We conjecture similar behavior in higher dimensions.Comment: Author home pages: http://www.wisdom.weizmann.ac.il/~itai http://www.math.chalmers.se/~olleh http://www.wisdom.weizmann.ac.il/~schram

Extended h-Index Parameterized Data Structures for Computing Dynamic Subgraph Statistics

We present techniques for maintaining subgraph frequencies in a dynamic graph, using data structures that are parameterized in terms of h, the h-index of the graph. Our methods extend previous results of Eppstein and Spiro for maintaining statistics for undirected subgraphs of size three to directed subgraphs and to subgraphs of size four. For the directed case, we provide a data structure to maintain counts for all 3-vertex induced subgraphs in O(h) amortized time per update. For the undirected case, we maintain the counts of size-four subgraphs in O(h^2) amortized time per update. These extensions enable a number of new applications in Bioinformatics and Social Networking research

Interaction Effect in the Kondo Energy of the Periodic Anderson-Hubbard Model

We extend the periodic Anderson model by switching on a Hubbard $U_d$ for the conduction electrons. The nearly integral valent (Kondo) limit of the Anderson--Hubbard model is studied with the Gutzwiller variational method. The new formula for the Kondo energy contains the $U_d$-dependent chemical potential of the Hubbard subsystem in the exponent, and the correlation-induced band narrowing in the prefactor. Both effects tend to suppress the Kondo scale, which can be understood to result from the blocking of hybridization (this behaviour is the opposite of that found for Kondo--Hubbard models). At half-filling, we find a Brinkman--Rice-type transition which leads from a small-gap Kondo insulator to a Mott insulator.Comment: 4 pages (ReVTeX), submitted for publicatio