8,427 research outputs found

    Bounded gaps between primes in special sequences

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    We use Maynard's methods to show that there are bounded gaps between primes in the sequence {nα}\{\lfloor n\alpha\rfloor\}, where α\alpha is an irrational number of finite type. In addition, given a superlinear function ff satisfying some properties described by Leitmann, we show that for all mm there are infinitely many bounded intervals containing mm primes and at least one integer of the form f(q)\lfloor f(q)\rfloor with qq a positive integer.Comment: 14 page

    Related Studies in Long Term Lithium Battery Stability

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    The continuing growth of the use of lithium electrochemical systems in a wide variety of both military and industrial applications is primarily a result of the significant benefits associated with the technology such as high energy density, wide temperature operation and long term stability. The stability or long term storage capability of a battery is a function of several factors, each important to the overall storage life and, therefore, each potentially a problem area if not addressed during the design, development and evaluation phases of the product cycle. Design (e.g., reserve vs active), inherent material thermal stability, material compatibility and self-discharge characteristics are examples of factors key to the storability of a power source

    Network Kriging

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    Network service providers and customers are often concerned with aggregate performance measures that span multiple network paths. Unfortunately, forming such network-wide measures can be difficult, due to the issues of scale involved. In particular, the number of paths grows too rapidly with the number of endpoints to make exhaustive measurement practical. As a result, it is of interest to explore the feasibility of methods that dramatically reduce the number of paths measured in such situations while maintaining acceptable accuracy. We cast the problem as one of statistical prediction--in the spirit of the so-called `kriging' problem in spatial statistics--and show that end-to-end network properties may be accurately predicted in many cases using a surprisingly small set of carefully chosen paths. More precisely, we formulate a general framework for the prediction problem, propose a class of linear predictors for standard quantities of interest (e.g., averages, totals, differences) and show that linear algebraic methods of subset selection may be used to effectively choose which paths to measure. We characterize the performance of the resulting methods, both analytically and numerically. The success of our methods derives from the low effective rank of routing matrices as encountered in practice, which appears to be a new observation in its own right with potentially broad implications on network measurement generally.Comment: 16 pages, 9 figures, single-space

    Galactic Escape Speeds in Mirror and Cold Dark Matter Models

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    The mirror dark matter (MDM) model of Berezhiani et al. has been shown to reproduce observed galactic rotational curves for a variety of spiral galaxies, and has been presented as an alternative to cold dark matter (CDM) models. We investigate possible additional tests involving the properties of stellar orbits, which may be used to discriminate between the two models. We demonstrate that in MDM and CDM models fitted equally well to a galactic rotational curve, one generally expects predictable differences in escape speeds from the disc. The recent radial velocity (RAVE) survey of the Milky Way has pinned down the escape speed from the solar neighbourhood to vesc=54446+64v_{esc}=544^{+64}_{-46} km s1^{-1}, placing an additional constraint on dark matter models. We have constructed an MDM model for the Milky Way based on its rotational curve, and find an escape speed that is just consistent with the observed value given the current errors, which lends credence to the viability of the MDM model. The Gaia-ESO spectroscopic survey is expected to lead to an even more precise estimate of the escape speed that will further constrain dark matter models. However, the largest differences in stellar escape speeds between both models are predicted for dark matter dominated dwarf galaxies such as DDO 154, and kinematical studies of such galaxies could prove key in establishing, or abolishing, the validity of the MDM model.Comment: Accepted for publication in the European Physical Journal

    Ultra-high-frequency piecewise-linear chaos using delayed feedback loops

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    We report on an ultra-high-frequency (> 1 GHz), piecewise-linear chaotic system designed from low-cost, commercially available electronic components. The system is composed of two electronic time-delayed feedback loops: A primary analog loop with a variable gain that produces multi-mode oscillations centered around 2 GHz and a secondary loop that switches the variable gain between two different values by means of a digital-like signal. We demonstrate experimentally and numerically that such an approach allows for the simultaneous generation of analog and digital chaos, where the digital chaos can be used to partition the system's attractor, forming the foundation for a symbolic dynamics with potential applications in noise-resilient communications and radar

    Teleportation and Dense Coding with Genuine Multipartite Entanglement

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    We present an explicit protocol E0{\cal E}_0 for faithfully teleporting an arbitrary two-qubit state via a genunie four-qubit entangled state. By construction, our four-partite state is not reducible to a pair of Bell states. Its properties are compared and contrasted with those of the four-party GHZ and W states. We also give a dense coding scheme D0{\cal D}_0 involving our state as a shared resource of entanglement. Both D0{\cal D}_0 and E0{\cal E}_0 indicate that our four-qubit state is a likely candidate for the genunine four-partite analogue to a Bell state.Comment: 9 pages, 0 figur

    Gas Discharge Lamps Are Volatile Memristors

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    Discharge lamps can be classified as high-pressure and low-pressure lamps, which operate under different scientific principles. They have exhibited the well-known fingerprints of memristors. This paper describes the mathematical models of both of high- and low-pressure discharge lamps based on their respective physical nature and behaviors, and then explains how these models can be unified into a generalized mathematical framework that confirms their memristor characteristics. Practical and theoretical results from high-pressure and low-pressure lamps are included to illustrate their 3 fingerprints of the memristor characteristics. The results indicate that gas discharge lamps are not ideal but volatile memristors.published_or_final_versio

    A new neurosurgical tool incorporating differential geometry and cellular automata techniques

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    Using optical coherence imaging, it is possible to visualize seizure progression intraoperatively. However, it is difficult to pinpoint an exact epileptic focus. This is crucial in attempts to minimize the amount of resection necessary during surgical therapeutic interventions for epilepsy and is typically done approximately from visual inspection of optical coherence imaging stills. In this paper, we create an algorithm with the potential to pinpoint the source of a seizure from an optical coherence imaging still. To accomplish this, a grid is overlaid on optical coherence imaging stills. This then serves as a grid for a two-dimensional cellular automation. Each cell is associated with a Riemannian curvature tensor representing the curvature of the brain's surface in all directions for a cell. Cells which overlay portions of the image which show neurons that are firing are considered "depolarized"
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