1,222 research outputs found

    A Perturbative Approach to Neutron Stars in f(T,T)f(T, \mathcal{T})-Gravity

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    We derive a Tolman-Oppenheimer-Volkoff equation in neutron star systems within the modified f(T,T)f(T, \mathcal{T})-gravity class of models using a perturbative approach. In our approach f(T,T)f(T, \mathcal{T})-gravity is considered to be a static spherically symmetric space-time. In this instance the metric is built from a more fundamental tetrad vierbein which can be used to relate inertial and global coordinates. A linear function f=T(r)+T(r)+χh(T,T)+O(χ2)f = T(r) + \mathcal{T}(r) + \chi h(T, \mathcal{T}) + \mathcal{O}(\chi^{2}) is taken as the Lagrangian density for the gravitational action. Finally we impose the polytropic equation of state of neutron star upon the derived equations in order to derive the mass profile and mass-central density relations of the neutron star in f(T,T)f(T, \mathcal{T})-gravity.Comment: arXiv admin note: text overlap with arXiv:1701.0476

    Bayesian Model Search for Nonstationary Periodic Time Series

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    We propose a novel Bayesian methodology for analyzing nonstationary time series that exhibit oscillatory behaviour. We approximate the time series using a piecewise oscillatory model with unknown periodicities, where our goal is to estimate the change-points while simultaneously identifying the potentially changing periodicities in the data. Our proposed methodology is based on a trans-dimensional Markov chain Monte Carlo (MCMC) algorithm that simultaneously updates the change-points and the periodicities relevant to any segment between them. We show that the proposed methodology successfully identifies time changing oscillatory behaviour in two applications which are relevant to e-Health and sleep research, namely the occurrence of ultradian oscillations in human skin temperature during the time of night rest, and the detection of instances of sleep apnea in plethysmographic respiratory traces.Comment: Received 23 Oct 2018, Accepted 12 May 201

    A Coriolis force in an inertial frame

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    Particles in rotating saddle potentials exhibit precessional motion which, up to now, has been explained by explicit computation. We show that this precession is due to a hidden Coriolis-like force which, unlike the standard Coriolis force, is present in the inertial frame. We do so by finding a hodograph-like "guiding center" transformation using the method of normal form. We also point out that the transformation cannot be of contact type in principle, thus showing that the standard (in applied literature) heuristic averaging gives the correct result but obscures the fact that the transformation of the position must involve the velocity

    They Were Meant for Each Other: Professor Edward Cooper and the Rules Enabling Act

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    This introduction to the essays in this Symposium illuminates Professor Ed Cooper\u27s years as Reporter to the Civil Rules Committee by first briefly describing those who preceded him in the position and his own background. We then describe some of Ed Cooper\u27s many contributions to the Civil Rules Committee, the Federal Rules, rulemaking, and civil procedure by examining the present state of the Rules Committees\u27 work under the Rules Enabling Act. We conclude that after almost eighty years of experience under that Act, it is working well in large part because of the sound leadership provided by Ed Cooper over his twenty years as Reporter. It was during these years that the Committee developed an approach to rulemaking that was at once transparent and empirical, with multiple opportunities for participation by members of the public, the bench, the academy, and the bar; with many informal opportunities for consultation with members of Congress and the Executive Branch; and with an understanding by the Committee of its role in relation to the courts, Congress, and the Executive. Two episodes of recent rulemaking and related activity are described as examples of how well the Rules Enabling Act is working, in large part because of the very flexibility and discretion the Act has provided since 1934. One of those episodes occurred when Judge Anthony Scirica chaired the Standing Committee and then- Judge David Levi chaired the Civil Rules Committee. The other occurred when Judge Lee Rosenthal and Judge Mark Kravitz were the chairs of the Standing and Civil Rules Committees, respectively. Both episodes provide a basis for optimism about the future. And they make clear Ed Cooper\u27s continued steady role in supporting and cultivating the robust good health of the rulemaking process and the institutional values it protects