Skyrmions in Quantum Hall Systems with Realistic Force-Laws

We study the charged excitations of quantum Hall systems at integer filling fractions $\nu=2n+1$, for a force-law that takes account of the finite width of the electron gas. For typical values of this width, in the limit of vanishing Zeeman energy we find that the low-energy excitations are ``skyrmions'' not only at $\nu=1$ but also at higher filling fractions. Our results lead to the prediction that, in typical samples, abrupt transitions to charged excitations with very large spins should be observable at filling fractions higher than $\nu=1$ if the Zeeman energy is reduced sufficiently.Comment: 5 pages, 3 ps-figures, revtex with epsf.tex and multicol.sty. To appear in Physical Review

Quasirandom Permutations

Chung and Graham define quasirandom subsets of $\mathbb{Z}_n$ to be those with any one of a large collection of equivalent random-like properties. We weaken their definition and call a subset of $\mathbb{Z}_n$ $\epsilon$-balanced if its discrepancy on each interval is bounded by $\epsilon n$. A quasirandom permutation, then, is one which maps each interval to a highly balanced set. In the spirit of previous studies of quasirandomness, we exhibit several random-like properties which are equivalent to this one, including the property of containing (approximately) the expected number of subsequences of each order-type. We provide a few applications of these results, present a construction for a family of strongly quasirandom permutations, and prove that this construction is essentially optimal, using a result of W. Schmidt on the discrepancy of sequences of real numbers.Comment: 30 pages, 2 figures, submitted to JCT

Oil Pulling: Fact or Fad?

Problem: There is a greater need in today’s world for better oral care across all populations. In developing countries, the tradition of oil pulling has provided an affordable and accessible alternative to antimicrobial rinse agents. Western society has taken note of this and oil pulling has emerged as the latest oral hygiene fad. Methods: This review of literature used the following databases: PubMed, CINAHL and Google Scholar to identify relevant research articles. Search terms included oil pulling, coconut oil, sesame seed oil, oil swishing, oral health, periodontitis, gingivitis, and bacterial adherence. The studies reviewed used previously validated data collection methods to report their results. Articles included in this review had to be published after 2015. Major findings: Many studies have shown oil pulling to be comparable to chlorhexidine in antimicrobial properties and even reduce plaque adherence. Conclusions: Oil pulling shows to be an additional method for improving oral hygiene by reducing bacterial counts, plaque adherence, malodor and aid in enhancing overall gingival health. Although there have been promising outcomes there needs to be larger scale, long term studies to definitively prove the benefits of oil pulling in the oral cavity. Additionally, these studies need to include subjects from varied geographic locations and cultures worldwide.https://scholarscompass.vcu.edu/denh_student/1009/thumbnail.jp

To coordinate or not to coordinate?

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