Sampling rare fluctuations of height in the Oslo ricepile model

We have studied large deviations of the height of the pile from its mean value in the Oslo ricepile model. We sampled these very rare events with probabilities of order $10^{-100}$ by Monte Carlo simulations using importance sampling. These simulations check our qualitative arguement [Phys. Rev. E, {\bf 73}, 021303, 2006] that in steady state of the Oslo ricepile model, the probability of large negative height fluctuations $\Delta h=-\alpha L$ about the mean varies as $\exp(-\kappa {\alpha}^4 L^3)$ as $L \to \infty$ with $\alpha$ held fixed, and $\kappa > 0$.Comment: 7 pages, 8 figure

Phenomenological Consequences of Right-handed Down Squark Mixings

The mixings of $d_R$ quarks, hidden from view in Standard Model (SM), are naturally the largest if one has an Abelian flavor symmetry. With supersymmetry (SUSY) their effects can surface via $\tilde d_R$ squark loops. Squark and gluino masses are at TeV scale, but they can still induce effects comparable to SM in $B_d$ (or $B_s$) mixings, while $D^0$ mixing could be close to recent hints from data. In general, CP phases would be different from SM, as may be indicated by recent B Factory data. Presence of non-standard soft SUSY breakings with large $\tan\beta$ could enhance $b\to d\gamma$ (or $s\gamma$) transitions.Comment: Version to appear in Phys. Rev. Let

Evidence for Factorization in Three-body B --> D(*) K- K0 Decays

Motivated by recent experimental results, we use a factorization approach to study the three-body B --> D(*) K- K0 decay modes. Two mechanisms are proposed for kaon pair production: current-produced (from vacuum) and transition (from B meson). The Bbar0 --> D(*)+ K- K0 decay is governed solely by the current-produced mechanism. As the kaon pair can be produced only by the vector current, the matrix element can be extracted from e+ e- --> K Kbar processes via isospin relations. The decay rates obtained this way are in good agreement with experiment. Both current-produced and transition processes contribute to B- --> D(*)0 K- K0 decays. By using QCD counting rules and the measured B- --> D(*)0 K- K0 decay rates, the measured decay spectra can be understood.Comment: 17 pages, 6 figure

Non-invertible transformations and spatiotemporal randomness

We generalize the exact solution to the Bernoulli shift map. Under certain conditions, the generalized functions can produce unpredictable dynamics. We use the properties of the generalized functions to show that certain dynamical systems can generate random dynamics. For instance, the chaotic Chua's circuit coupled to a circuit with a non-invertible I-V characteristic can generate unpredictable dynamics. In general, a nonperiodic time-series with truncated exponential behavior can be converted into unpredictable dynamics using non-invertible transformations. Using a new theoretical framework for chaos and randomness, we investigate some classes of coupled map lattices. We show that, in some cases, these systems can produce completely unpredictable dynamics. In a similar fashion, we explain why some wellknown spatiotemporal systems have been found to produce very complex dynamics in numerical simulations. We discuss real physical systems that can generate random dynamics.Comment: Accepted in International Journal of Bifurcation and Chao

Phenomenological constraints on minimally coupled exotic lepton triplets

By introducing a set of new triplet leptons (with nonzero hypercharge) that can Yukawa couple to their Standard Model counterparts, new sources of tree-level flavor changing currents are induced via mixing. In this work, we study some of the consequences of such new contributions on processes such as the leptonic decays of gauge bosons, $\ell \rightarrow 3\ell'$ and $\ell \rightarrow \ell' \gamma$ which violate lepton flavor, and mu-e conversion in atomic nuclei. Constraints are then placed on the parameters associated with the exotic triplets by invoking the current low-energy experimental data. Moreover, the new physics contribution to the lepton anomalous magnetic moments is calculated.Comment: 17 pages, 1 figure, 2 tables (REVTeX4.1); v2: refs added, to appear in PR

Imaging Oxygen Defects and their Motion at a Manganite Surface

Manganites are technologically important materials, used widely as solid oxide fuel cell cathodes: they have also been shown to exhibit electroresistance. Oxygen bulk diffusion and surface exchange processes are critical for catalytic action, and numerous studies of manganites have linked electroresistance to electrochemical oxygen migration. Direct imaging of individual oxygen defects is needed to underpin understanding of these important processes. It is not currently possible to collect the required images in the bulk, but scanning tunnelling microscopy could provide such data for surfaces. Here we show the first atomic resolution images of oxygen defects at a manganite surface. Our experiments also reveal defect dynamics, including oxygen adatom migration, vacancy-adatom recombination and adatom bistability. Beyond providing an experimental basis for testing models describing the microscopics of oxygen migration at transition metal oxide interfaces, our work resolves the long-standing puzzle of why scanning tunnelling microscopy is more challenging for layered manganites than for cuprates.Comment: 7 figure

Whole Transcriptome Analysis of the Coral Acropora millepora Reveals Complex Responses to CO2-driven Acidification during the Initiation of Calcification

n/

Low-Mass Baryon-Antibaryon Enhancements in B Decays

The nature of low-mass baryon-antibaryon enhancements seen in B decays is explored. Three possibilities include (i) states near threshold as found in a model by Nambu and Jona-Lasinio, (ii) isoscalar states with $J^{PC} = 0^{\pm +}$ coupled to a pair of gluons, and (iii) low-mass enhancements favored by the fragmentation process. Ways of distinguishing these mechanisms using angular distributions and flavor symmetry are proposed.Comment: 8 pages, LaTeX, no figures, to be submitted to Phys. Rev. D. One reference adde