cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
IEEE PES Webinar Series: A Refresher talk on Electrical Safety (Slides)
Creators: Koti Reddy B.
Publisher: name: IEEE
Year: 2020

Electricity is very useful for mankind since its invention. We are using it in our domestic life and Industries for lighting, Heating, Ventilation, Air- Conditioning, Fans, and to drive Pumps, Compressors etc. We know the importance of human life and so the safety precautions when working with electricity. This talk aims to highlight the hazards associated with electricity and the precautions to be taken. Contents: Type of electric accidents, Causes of accidents, voltage levels and hazards, effects of elec. Current, body resistance, arc flash safety, safety measures and audit and codes/standards.
Electricity is very useful for mankind since its invention. We are using it in our domestic life and Industries for lighting, Heating, Ventilation, Air- Conditioning, Fans, and to drive Pumps, Compressors etc. We know the importance of human life and so the safety precautions when working with electricity. This talk aims to highlight the hazards associated with electricity and the precautions to be taken. Contents: Type of electric accidents, Causes of accidents, voltage levels and hazards, effects of elec. Current, body resistance, arc flash safety, safety measures and audit and codes/standards.
A Neutron diffraction study of multiferroics RMn2O5
Creators: name: Radaelli, P. G.
name: Chapon, L. C.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: The magnetic properties of RMn2O5 multiferrroics as obtained by unpolarized and polarized neutron diffraction experiments are reviewed. We discuss the qualitative features of the magnetic phase diagram both in zero magnetic field and in field and analyze the commensurate magnetic structure and its coupling to an applied electric field. The origin of ferrolectricity is discussed based on calculations of the ferroelectric polarization predicted by different microscopic coupling mechanisms (exchange striction and cycloidal spin-orbit models). A minimal model containing a small set of parameters is also presented in order to understand the propagation of the magnetic structure along the c-direction.
description: IOP Review
The Spin and Orientation of the Black Hole in XTE J1908$+$094
Creators: name: Draghis, Paul A.
name: Miller, Jon M.
name: Zoghbi, Abderahmen
name: Kammoun, Elias S.
name: Reynolds, Mark T.
name: Tomsick, John A.
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: NuSTAR observed the black hole candidate XTE J1908$+$094 during its 2013 and 2019 outbursts. We use relativistic reflection to measure the spin of the black hole through 19 different assumptions of relxill flavors and parameter combinations. The most favored model in terms of Deviance Information Criterion (DIC) measures the spin of the black hole to be $a = 0.55^{+0.29}_{-0.45}$, and an inclination of $θ=27^{+2}_{-3}$ degrees ($1σ$ statistical errors). We look at the effects of coronal geometry assumptions and density of the accretion disk on the spin prediction. All 19 tested models provide consistent spin estimates. We discuss the evolution of spin measurement techniques using relativistic reflection in X-ray binaries and discuss the implications of this spin measurement in reconciling the distributions of stellar mass black hole spin measurements made through X-ray and gravitational wave observations.
description: 16 pages, 7 figures, 3 tables. Accepted for publication in ApJ
Signals of the QCD phase transition in core-collapse supernovae
Creators: name: Sagert, I.
name: Hempel, M.
name: Pagliara, G.
name: Schaffner-Bielich, J.
name: Fischer, T.
name: Mezzacappa, A.
name: Thielemann, F. -K.
name: Liebendörfer, M.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We explore the implications of the QCD phase transition during the postbounce evolution of core-collapse supernovae. Using the MIT bag model for the description of quark matter and assuming small bag constants, we find that the phase transition occurs during the early postbounce accretion phase. This stage of the evolution can be simulated with general relativistic three-flavor Boltzmann neutrino transport. The phase transition produces a second shock wave that triggers a delayed supernova explosion. If such a phase transition happens in a future galactic supernova, its existence and properties should become observable as a second peak in the neutrino signal that is accompanied by significant changes in the energy of the emitted neutrinos. In contrast to the first neutronization burst, this second neutrino burst is dominated by the emission of anti-neutrinos because the electron-degeneracy is lifted when the second shock passes through the previously neutronized matter.
description: 5 pages, 3 figures, 1 table, submitted to PRL
PES Web-based Tutorial Series: Understanding Transient Recovery Voltages and Their Measurement in Substations, Session 1: Transient Recovery Voltage Basics (Slides)
Creators: Dr. David Peelo & Dr. Farnoosh Rahmatian
Publisher: name: IEEE
Year: 2020

Transient recovery voltages (TRVs) are the voltages imposed on circuit breakers immediately after current interruption. The principal cases of interest are the interruption of the currents associated with terminal faults, short line faults and out-of-phase switching and breaking capacitive and inductive load currents. Each case is discussed in detail explaining the origin and derivation of the attributes associated with the TRVs including pole factors, amplitude factors, two and four parameter representations and travelling waves where applicable. Instrumentation for field measurement of TRVs will be discussed. Practical field issues such as sensor size and location, the challenge of using electric sensors that effectively change the circuit under test will be discussed. Use of optical voltage and current measurement techniques for non-intrusive measurement will be discussed in detail.
Transient recovery voltages (TRVs) are the voltages imposed on circuit breakers immediately after current interruption. The principal cases of interest are the interruption of the currents associated with terminal faults, short line faults and out-of-phase switching and breaking capacitive and inductive load currents. Each case is discussed in detail explaining the origin and derivation of the attributes associated with the TRVs including pole factors, amplitude factors, two and four parameter representations and travelling waves where applicable. Instrumentation for field measurement of TRVs will be discussed. Practical field issues such as sensor size and location, the challenge of using electric sensors that effectively change the circuit under test will be discussed. Use of optical voltage and current measurement techniques for non-intrusive measurement will be discussed in detail.
Bragg spectroscopy and Ramsey interferometry with an ultracold Fermi gas
Creators: name: Deh, B.
name: Marzok, C.
name: Slama, S.
name: Zimmermann, C.
name: Courteille, Ph. W.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Other Condensed Matter (cond-mat.other)
subject: FOS: Physical sciences

description: We report on the observation of Bragg scattering of an ultracold Fermi gas of 6Li atoms at a dynamic optical potential. The momentum states produced in this way oscillate in the trap for time scales on the order of seconds, nearly unperturbed by collisions, which are absent for ultracold fermions due to the Pauli principle. In contrast, interactions in a mixture with 87Rb atoms lead to rapid damping. The coherence of these states is demonstrated by Ramsey-type matter wave interferometry. The signal is improved using an echo pulse sequence, allowing us to observe coherence times longer than 100 mus. Finally we use Bragg spectroscopy to measure the in-situ momentum distribution of the 6Li cloud. Signatures for the degeneracy of the Fermi gas can be observed directly from the momentum distribution of the atoms inside the trap.
description: 19 pages, 10 figures
title: Front Matter, Table of Contents, Preface, Conference Organization
Creators: name: Cabello, Sergio
name: Chen, Danny Z.
Publisher: name: Schloss Dagstuhl – Leibniz-Zentrum für Informatik
Year: 2020
Subjects: subject: Front Matter
subject: Table of Contents
subject: Preface
subject: Conference Organization
subject: Theory of computation → Computational geometry
subject: Theory of computation → Design and analysis of algorithms
subject: Mathematics of computing → Combinatorics
subject: Mathematics of computing → Graph algorithms

description: Front Matter, Table of Contents, Preface, Conference Organization
description: LIPIcs, Vol. 164, 36th International Symposium on Computational Geometry (SoCG 2020), pages 0:i-0:xx
IEEE PES Webinar Series: A kinetic Monte Carlo Approach for Computing Cascading Failure Probabilities (slides)
Creators: Dr. Mihai Anitescu
Publisher: name: IEEE
Year: 2020

In power grid planning, operating points are set so that power generation can safely satisfy projected power demand until the next setpoint. Between setpoints (~10 minutes), the grid is subject to parametric uncertainty in demand and generation levels. These variations can cause the grid's autonomous feedback systems to initiate fault-protection mechanisms that may de-energize infrastructure components and spread throughout the network. In severe cases, these sequences of actions may result in the loss of power in significant portions of the grid. Such cascading failures are rare and difficult to study empirically, and in this talk, we discuss one approach for characterizing the distribution of cascade severity due to parametric uncertainty in demand and generation. Specifically, using a stochastically perturbed, first-principles dynamical model of the power grid, we build a kinetic Monte Carlo (kMC) model of component failure, which in turns allow to much more efficiently simulate from the distribution of cascading failures. To do compute the kMC model, we utilize results from large deviation theory in combination with simulation tools developed for studying chemical reactions; the cost of computing the conditional probability of one failure (one transition) is roughly the cost of one Optimal AC Power Flow calculation. We will discuss possible extensions and usage of such information for operations and planning.
In power grid planning, operating points are set so that power generation can safely satisfy projected power demand until the next setpoint. Between setpoints (~10 minutes), the grid is subject to parametric uncertainty in demand and generation levels. These variations can cause the grid's autonomous feedback systems to initiate fault-protection mechanisms that may de-energize infrastructure components and spread throughout the network. In severe cases, these sequences of actions may result in the loss of power in significant portions of the grid. Such cascading failures are rare and difficult to study empirically, and in this talk, we discuss one approach for characterizing the distribution of cascade severity due to parametric uncertainty in demand and generation. Specifically, using a stochastically perturbed, first-principles dynamical model of the power grid, we build a kinetic Monte Carlo (kMC) model of component failure, which in turns allow to much more efficiently simulate from the distribution of cascading failures. To do compute the kMC model, we utilize results from large deviation theory in combination with simulation tools developed for studying chemical reactions; the cost of computing the conditional probability of one failure (one transition) is roughly the cost of one Optimal AC Power Flow calculation. We will discuss possible extensions and usage of such information for operations and planning.
Additional file 1 of Neighborhood disadvantage and individual-level life stressors in relation to breast cancer incidence in US Black women
Creators: name: Barber, Lauren E.
name: Zirpoli, Gary R.
name: Cozier, Yvette C.
name: Rosenberg, Lynn
name: Petrick, Jessica L.
name: Bertrand, Kimberly A.
name: Palmer, Julie R.
Publisher: name: figshare
Year: 2021
Subjects: subject: Medicine
subject: Biotechnology
subject: Cancer
subject: Science Policy
subject: 111714 Mental Health
subject: FOS: Health sciences

description: Additional file 1: Table S1. Distributions of the factors that contribute to neighborhood SES and neighborhood concentrated disadvantage scores, at baseline in 1995.
PES Web-based Tutorial Series: Understanding Transient Recovery Voltages and Their Measurement in Substations, Session 3: Load Current Switching Transient Recovery Voltages (Slides)
Creators: Dr. David Peelo & Dr. Farnoosh Rahmatian
Publisher: name: IEEE
Year: 2020

Transient recovery voltages (TRVs) are the voltages imposed on circuit breakers immediately after current interruption. The principal cases of interest are the interruption of the currents associated with terminal faults, short line faults and out-of-phase switching and breaking capacitive and inductive load currents. Each case is discussed in detail explaining the origin and derivation of the attributes associated with the TRVs including pole factors, amplitude factors, two and four parameter representations and travelling waves where applicable. Instrumentation for field measurement of TRVs will be discussed. Practical field issues such as sensor size and location, the challenge of using electric sensors that effectively change the circuit under test will be discussed. Use of optical voltage and current measurement techniques for non-intrusive measurement will be discussed in detail.
Transient recovery voltages (TRVs) are the voltages imposed on circuit breakers immediately after current interruption. The principal cases of interest are the interruption of the currents associated with terminal faults, short line faults and out-of-phase switching and breaking capacitive and inductive load currents. Each case is discussed in detail explaining the origin and derivation of the attributes associated with the TRVs including pole factors, amplitude factors, two and four parameter representations and travelling waves where applicable. Instrumentation for field measurement of TRVs will be discussed. Practical field issues such as sensor size and location, the challenge of using electric sensors that effectively change the circuit under test will be discussed. Use of optical voltage and current measurement techniques for non-intrusive measurement will be discussed in detail.
Complexity of Hybrid Logics over Transitive Frames
Creators: name: Mundhenk, Martin
name: Schneider, Thomas
name: Schwentick, Thomas
name: Weber, Volker
Publisher: name: arXiv
Year: 2008
Subjects: subject: Logic in Computer Science (cs.LO)
subject: FOS: Computer and information sciences
subject: F.4.1

description: This paper examines the complexity of hybrid logics over transitive frames, transitive trees, and linear frames. We show that satisfiability over transitive frames for the hybrid language extended with the downarrow operator is NEXPTIME-complete. This is in contrast to undecidability of satisfiability over arbitrary frames for this language (Areces, Blackburn, Marx 1999). It is also shown that adding the @ operator or the past modality leads to undecidability over transitive frames. This is again in contrast to the case of transitive trees and linear frames, where we show these languages to be nonelementarily decidable. Moreover, we establish 2EXPTIME and EXPTIME upper bounds for satisfiability over transitive frames and transitive trees, respectively, for the hybrid Until/Since language. An EXPTIME lower bound is shown to hold for the modal Until language over both frame classes.
description: 21 pages, 6 figures (only 2 thereof are in external files)
IEEE PES Publications Webinar Series - Impedance of Three-phase Systems in DQ, Sequence, and Phasor Domains (Slides)
Creators: Shahil Shah
PhD
Publisher: name: IEEE
Year: 2020

This webinar will explore relationships between the impedance of three-phase systems in DQ, sequence, and phasor domains. Each of these domains have been used separately for modeling, stability analysis, fault analysis, and protection design of power systems; however, the relationships between them are not thoroughly understood. This webinar will show that the impedance in all the three domains are mathematically related and so-called frequency coupling effects play an important role in how they are related. The webinar will also discuss how the dc and ac side power systems are dynamically coupled through an HVDC converter. Impedance measurements of utility-scale wind turbines and inverters will be presented to experimentally demonstrate the relationship between the dq and sequence domains.
This webinar will explore relationships between the impedance of three-phase systems in DQ, sequence, and phasor domains. Each of these domains have been used separately for modeling, stability analysis, fault analysis, and protection design of power systems; however, the relationships between them are not thoroughly understood. This webinar will show that the impedance in all the three domains are mathematically related and so-called frequency coupling effects play an important role in how they are related. The webinar will also discuss how the dc and ac side power systems are dynamically coupled through an HVDC converter. Impedance measurements of utility-scale wind turbines and inverters will be presented to experimentally demonstrate the relationship between the dq and sequence domains.
Finding the Right Bricks for Molecular Lego: A Data Mining Approach to Organic Semiconductor Design
Creators: name: Kunkel, Christian
name: Schober, Christoph
name: Margraf, Johannes T.
name: Reuter, Karsten
name: Oberhofer, Harald
Publisher: name: arXiv
Year: 2021
Subjects: subject: Chemical Physics (physics.chem-ph)
subject: Computational Physics (physics.comp-ph)
subject: FOS: Physical sciences

description: Improving charge carrier mobilities in organic semiconductors is a challenging task that has hitherto primarily been tackled by empirical structural tuning of promising core compounds. Knowledge-based methods can greatly accelerate such local exploration, while a systematic analysis of large chemical databases can point towards promising design strategies. Here, we demonstrate such data mining by clustering an in-house database of >64.000 organic molecular crystals for which two charge-transport descriptors, the electronic coupling and the reorganization energy, have been calculated from first principles. The clustering is performed according to the Bemis-Murcko scaffolds of the constituting molecules and according to the sidegroups with which these molecular backbones are functionalized. In both cases, we obtain statistically significant structure-property relationships with certain scaffolds (sidegroups) consistently leading to favorable charge-transport properties. Functionalizing promising scaffolds with favorable sidegroups results in engineered molecular crystals for which we indeed compute improved charge-transport properties.
On characterizing terrain visibility graphs
Creators: name: Evans, William
name: Saeedi, Noushin
Publisher: name: Journal of Computational Geometry
Year: 2015

description: A terrain is an $x$-monotone polygonal line in the $xy$-plane. Two vertices of a terrain are mutually visible if and only if there is no terrain vertex on or above the open line segment connecting them. A graph whose vertices represent terrain vertices and whose edges represent mutually visible pairs of terrain vertices is called a terrain visibility graph. We would like to find properties that are both necessary and sufficient for a graph to be a terrain visibility graph; that is, we would like to characterize terrain visibility graphs. Abello et al. [Discrete and Computational Geometry, 14(3):331--358, 1995] showed that all terrain visibility graphs are “persistent”. They showed that the visibility information of a terrain point set implies some ordering requirements on the slopes of the lines connecting pairs of points in any realization, and as a step towards showing sufficiency, they proved that for any persistent graph $M$ there is a total order on the slopes of the (pseudo) lines in a generalized configuration of points whose visibility graph is $M$. We give a much simpler proof of this result by establishing an orientation to every triple of vertices, reflecting some slope ordering requirements that are consistent with $M$ being the visibility graph, and prove that these requirements form a partial order. We give a faster algorithm to construct a total order on the slopes. Our approach attempts to clarify the implications of the graph theoretic properties on the ordering of the slopes, and may be interpreted as defining properties on an underlying oriented matroid that we show is a restricted type of $3$-signotope.
description: Journal of Computational Geometry, Vol. 6 No. 1 (2015)
A Catalog of Host Galaxies for WISE-Selected AGN: Connecting Host Properties with Nuclear Activity and Identifying Contaminants
Creators: name: Barrows, R. Scott
name: Comerford, Julia M.
name: Stern, Daniel
name: Assef, Roberto J.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We present a catalog of physical properties for galaxies hosting active galactic nuclei (AGN) detected by the Wide-field Infrared Survey Explorer (WISE). By fitting broadband spectral energy distributions of sources in the WISE AGN Catalog (Assef et al. 2018) with empirical galaxy and AGN templates, we derive photometric redshifts, AGN bolometric luminosities, measures of AGN obscuration, host galaxy stellar masses, and host galaxy star formation rates (SFRs) for 695,273 WISE AGN. The wide-area nature of this catalog significantly augments the known number of obscured AGN out to redshifts of z~3 and will be useful for studies focused on AGN or their host galaxy physical properties. We first show that the most likely non-AGN contaminants are galaxies at redshifts of z=0.2-0.3, with relatively blue W1-W2 colors, and with high specific SFRs for which the dust continuum emission is elevated in the W2 filter. Toward increasingly lower redshifts, WISE AGN host galaxies have systematically lower specific SFRs, relative to those of normal star forming galaxies, likely due to decreased cold gas fractions and the time delay between global star formation and AGN triggering. Finally, WISE AGN obscuration is not strongly correlated with AGN bolometric luminosity but shows a significant negative correlation with Eddington ratio. This result is consistent with a version of the `receding torus' model in which the obscuring material is located within the supermassive black hole gravitational sphere of influence and the dust inner radius increases due to radiation pressure.
description: 21 pages, 17 figures. Accepted for publication in the Astrophysical Journal. The full catalog is available from the publisher or from the corresponding author upon request
Effects of phase transitions in devices actuated by the electromagnetic vacuum force
Creators: name: Benassi, A.
name: Calandra, C.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We study the influence of the electromagnetic vacuum force on the behaviour of a model device based on materials, like germanium tellurides, that undergo fast and reversible metal-insulator transitions on passing from the crystalline to the amorphous phase. The calculations are performed at finite temperature and fully accounting for the behaviour of the material dielectric functions. The results show that the transition can be exploited to extend the distance and energy ranges under which the device can be operated without undergoing stiction phenomena. We discuss the approximation involved in adopting the Casimir expression in simulating nano- and micro- devices at finite temperature.
Additional file 1 of COVID-19 vaccine acceptance, hesitancy, and determinants among physicians in a university-based teaching hospital in Thailand
Creators: name: Sirikalyanpaiboon, May
name: Ousirimaneechai, Krittin
name: Phannajit, Jeerath
name: Pitisuttithum, Panyavee
name: Jantarabenjakul, Watsamon
name: Chaiteerakij, Roongruedee
name: Paitoonpong, Leilani
Publisher: name: figshare
Year: 2021
Subjects: subject: Immunology
subject: FOS: Clinical medicine

description: Additional file 1: Appendix A. English-translated version of the questionnaire.
Front instabilities in evaporatively dewetting nanofluids
Creators: name: Vancea, I.
name: Thiele, U.
name: Pauliac-Vaujour, E.
name: Stannard, A.
name: Martin, C. P.
name: Blunt, M. O.
name: Moriarty, P. J.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Chemical Physics (physics.chem-ph)
subject: FOS: Physical sciences

description: Various experimental settings that involve drying solutions or suspensions of nanoparticles -- often called nanofluids -- have recently been used to produce structured nanoparticle layers. In addition to the formation of polygonal networks and spinodal-like patterns, the occurrence of branched structures has been reported. After reviewing the experimental results we use a modified version of the Monte Carlo model first introduced by Rabani et al. [Nature 426, 271 (2003)] to study structure formation in evaporating films of nanoparticle solutions for the case that all structuring is driven by the interplay of evaporating solvent and diffusing nanoparticles. After introducing the model and its general behavior we focus on receding dewetting fronts which are initially straight but develop a transverse fingering instability. We analyze the dependence of the characteristics of the resulting branching patterns on the driving chemical potential, the mobility and concentration of the nanoparticles, and the interaction strength between liquid and nanoparticles. This allows us to understand the underlying instability mechanism.
description: 35 pages, 28 figures
IEEE PES Webinar Series: Graph Database and Graph Computing for Power System Applications
Creators: Renchang Dai
Publisher: name: IEEE
Year: 2020

The increasing penetration of distributed generation and the reliability requirements of sub-transmission power system bring up a need to model and analyze transmission and sub-transmission networks together. To meet the high computation efficiency requirements of power system applications for transmission and sub-transmission network, the IEEE Power and Energy Society (PES) Power System Operation, Planning, and Economics (PSOPE) committee Technologies & Innovations Sub-Committee Faster Than Real-Time Computing Task Force studied an innovative graph computing technology based on graph database which will be presented in this Webinar. The concept and approach of the graph nodal and hierarchical parallelism will be introduced. The graph computing technologies are applied to topology analysis, state estimation, power flow, contingency analysis and one line diagram automation generation applications. It has great potentials on transient simulations and power system optimizations.
The increasing penetration of distributed generation and the reliability requirements of sub-transmission power system bring up a need to model and analyze transmission and sub-transmission networks together. To meet the high computation efficiency requirements of power system applications for transmission and sub-transmission network, the IEEE Power and Energy Society (PES) Power System Operation, Planning, and Economics (PSOPE) committee Technologies & Innovations Sub-Committee Faster Than Real-Time Computing Task Force studied an innovative graph computing technology based on graph database which will be presented in this Webinar. The concept and approach of the graph nodal and hierarchical parallelism will be introduced. The graph computing technologies are applied to topology analysis, state estimation, power flow, contingency analysis and one line diagram automation generation applications. It has great potentials on transient simulations and power system optimizations.
Quark matter in compact stars: astrophysical implications and possible signatures
Creators: name: Bombaci, I.
Publisher: name: arXiv
Year: 2008
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Astrophysics (astro-ph)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: After a brief non technical introduction of the basic properties of strange quark matter (SQM) in compact stars, we consider some of the late important advances in the field, and discuss some recent astrophysical observational data that could shed new light on the possible presence of SQM in compact stars. We show that above a threshold value of the gravitational mass a neutron star (pure hadronic star) is metastable to the decay (conversion) to an hybrid neutron star or to a strange star. We explore the consequences of the metastability of "massive" neutron stars and of the existence of stable compact "quark" stars (hybrid neutron stars or strange stars) on the concept of limiting mass of compact stars, and we give an extension of this concept with respect to the "classical" one given in 1939 by Oppenheimer and Volkoff.
description: Invited talk at "the Eleventh Marcel Grossman Meeting on General Relativity", Berlin 2006
XMM-Newton observations of the Small Magellanic Cloud: Be/X-ray binary pulsars active between October 2006 and June 2007
Creators: name: Haberl, F.
name: Eger, P.
name: Pietsch, W.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: (abridged) We analysed eight XMM-Newton observations toward the Small Magellanic Cloud (SMC), performed between October 2006 and June 2007, to investigate high mass X-ray binary systems. We found new X-ray binary pulsars with periods of 202 s (XMMU J005929.0-723703), 342 s (XMMU J005403.8-722632), 645 s (XMMU J005535.2-722906) and 325 s (XMMU J005252.1-721715), in the latter case confirming the independent discovery in Chandra data. In addition we detected sixteen known Be/X-ray binary pulsars and six ROSAT-classified candidate high mass X-ray binaries. From one of the candidates, RX J0058.2-7231, we discovered X-ray pulsations with a period of 291 s which makes it the likely counterpart of XTE J0051-727. From the known pulsars, we revise the pulse period of CXOU J010206.6-714115 to 967 s, and we detected the 18.37 s pulsar XTE J0055-727 (= XMM J004911.4-724939) in outburst, which allowed us to localise the source. The pulse profiles of the X-ray pulsars show a large variety of shapes from smooth to highly structured patterns and differing energy dependence. For all the candidate high mass X-ray binaries optical counterparts can be identified with magnitudes and colours consistent with Be stars. Twenty of the Be/X-ray binaries were detected with X-ray luminosities in the range 1.5x10^35 erg/s - 5.5x10^36 erg/s. The majority of the spectra is well represented by an absorbed power-law with an average power-law index of 0.93. The absorption (in addition to the Galactic foreground value) varies over a wide range between a few 10^20 H cm^-2 and several 10^22 H cm^-2. An overall correlation of the absorption with the total SMC HI column density suggests that the absorption seen in the X-ray spectra is often largely caused by interstellar gas.
description: Accepted for publication in A&A, 22 pages, 12 figures
Thermodynamic Limit for Spin Glasses. Beyond the Annealed Bound
Creators: name: Contucci, Pierluigi
name: Starr, Shannon
Publisher: name: arXiv
Year: 2008
Subjects: subject: Mathematical Physics (math-ph)
subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: FOS: Physical sciences

description: Using a correlation inequality of Contucci and Lebowitz for spin glasses, we demonstrate existence of the thermodynamic limit for short-ranged spin glasses, under weaker hypotheses than previously available, namely without the assumption of the annealed bound.
description: 8 pages
On the complexity of minimum-link path problems
Creators: name: Kostitsyna, Irina
name: Löffler, Maarten
name: Polishchuk, Valentin
name: Staals, Frank
Publisher: name: Journal of Computational Geometry
Year: 2017

description: We revisit the minimum-link path problem: Given a polyhedral domain and two points in it, connect the points by a polygonal path with minimum number of edges. We consider settings where the vertices and/or the edges of the path are restricted to lie on the boundary of the domain, or can be in its interior. Our results include bit complexity bounds, a novel general hardness construction, and a polynomial-time approximation scheme. We fully characterize the situation in 2 dimensions, and provide first results in dimensions 3 and higher for several variants of the problem. Concretely, our results resolve several open problems. We prove that computing the minimum-link diffuse reflection path, motivated by ray tracing in computer graphics, is NP-hard, even for two-dimensional polygonal domains with holes. This has remained an open problem [Ghosh et al.'2012] despite a large body of work on the topic. We also resolve the open problem from [Mitchell et al.'1992] mentioned in the handbook [Goodman and Rourke'2004] (see Chapter 27.5, Open problem 3) and The Open Problems Project [http://maven.smith.edu/~orourke/TOPP/] (see Problem 22): "What is the complexity of the minimum-link path problem in 3-space?" Our results imply that the problem is NP-hard even on terrains (and hence, due to discreteness of the answer, there is no FPTAS unless P=NP), but admits a PTAS.
description: Journal of Computational Geometry, Vol. 8 No. 2 (2017): Special Issue of Selected Papers from SoCG 2016
Transverse oscillations of systems of coronal loops
Creators: name: Luna, M.
name: Terradas, J.
name: Oliver, R.
name: Ballester, J. L.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We study the collective kinklike normal modes of a system of several cylindrical loops using the T-matrix theory. Loops that have similar kink frequencies oscillate collectively with a frequency which is slightly different from that of the individual kink mode. On the other hand, if the kink frequency of a loop is different from that of the others, it oscillates individually with its own frequency. Since the individual kink frequency depends on the loop density but not on its radius for typical 1 MK coronal loops, a coupling between kink oscillations of neighboring loops take place when they have similar densities. The relevance of these results in the interpretation of the oscillations studied by \citet{schrijver2000} and \citet{verwichte2004}, in which transverse collective loop oscillations seem to be detected, is discussed. In the first case, two loops oscillating in antiphase are observed; interpreting this motion as a collective kink mode suggests that their densities are roughly equal. In the second case, there are almost three groups of tubes that oscillate with similar periods and therefore their dynamics can be collective, which again seems to indicate that the loops of each group share a similar density. All the other loops seem to oscillate individually and their densities can be different from the rest.
Spin dynamics in the pseudogap state of a high-temperature superconductor
Creators: name: Hinkov, V.
name: Bourges, P.
name: Pailhes, S.
name: Sidis, Y.
name: Ivanov, A.
name: Frost, C. D.
name: Perring, T. G.
name: Lin, C. T.
name: Chen, D. P.
name: Keimer, B.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: The pseudogap is one of the most pervasive phenomena of high temperature superconductors. It is attributed either to incoherent Cooper pairing setting in above the superconducting transition temperature Tc, or to a hidden order parameter competing with superconductivity. Here we use inelastic neutron scattering from underdoped YBa(2)Cu(3)O(6.6) to show that the dispersion relations of spin excitations in the superconducting and pseudogap states are qualitatively different. Specifically, the extensively studied "hour glass" shape of the magnetic dispersions in the superconducting state is no longer discernible in the pseudogap state and we observe an unusual "vertical" dispersion with pronounced in-plane anisotropy. The differences between superconducting and pseudogap states are thus more profound than generally believed, suggesting a competition between these two states. Whereas the high-energy excitations are common to both states and obey the symmetry of the copper oxide square lattice, the low-energy excitations in the pseudogap state may be indicative of collective fluctuations towards a state with broken orientational symmetry predicted in theoretical work.
description: 6 pages, 8 figures, contains supplementary information. Some data from V. Hinkov et al., arXiv:cond-mat/0601048, is included
Optical and infrared flares from a transient Galactic soft gamma-ray repeater
Creators: name: Castro-Tirado, A. J.
name: Postigo, A. de Ugarte
name: Gorosabel, J.
name: Jelinek, M.
name: Fatkhullin, T. A.
name: Sokolov, V. V.
name: Ferrero, P.
name: Kann, D. A.
name: Klose, S.
name: Sluse, D.
name: Bremer, M.
name: Winters, J. M.
name: Nuernberger, D.
name: Perez-Ramirez, D.
name: Guerrero, M. A.
name: French, J.
name: Melady, G.
name: Hanlon, L.
name: McBreen, B.
name: Aceituno, F. J.
name: Cunniffe, R.
name: Kubanek, P.
name: Vitek, S.
name: Schulze, S.
name: Wilson, A. C.
name: Hudec, R.
name: Gonzalez-Perez, J. M.
name: Shahbaz, T.
name: Guziy, S.
name: Pandey, S. B.
name: Pavlenko, L.
name: Sonbas, E.
name: Trushkin, S. A.
name: Bursov, N. N.
name: Nizhelskij, N. A.
name: Sabau-Graziati, L.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: Soft gamma-ray repeaters (SGRs) are a rare type of gamma-ray transient sources that are ocasionally detected as bursts in the high-energy sky. They are thought to be produced by magnetars, young neutron stars with very strong magnetic fields of the order of 10^(14-15) G. Only three such objects are known in our Galaxy, and a fourth one is associated with the supernova remnant N49 in the Large Magellanic Cloud. In none of these cases has an optical counterpart to either the gamma-ray flares or the quiescent source been identified. Here we present multi-wavelength observations of a puzzling source, SWIFT J195509+261406, for which we detected more than 40 flaring episodes in the optical band over a time span of 3 days, plus a faint infrared flare 11 days later, after which it returned to quiescence. We propose that SWIFT J195509+261406 is a member of a subgroup of SGRs for which the long-term X-ray emission is transient in nature. Furthermore, it is the first SGR for which bursts have been detected in the optical and near-infrared bands and maybe the link between the "persistent" SGRs and the dim isolated neutron stars.
description: Version submitted to Nature on 31 Jan 2008. A substantially revised version of this work has been published in Nature, vol. 455 issue 7212 pp 506-509 under the title "Flares from a Galactic magnetar suggest a missing link to dim isolated neutron stars"
On some block ciphers and imprimitive groups
Creators: name: Caranti, A.
name: Volta, F. Dalla
name: Sala, M.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Group Theory (math.GR)
subject: FOS: Mathematics
subject: 20B15

description: The group generated by the round functions of a block ciphers is a widely investigated problem. We identify a large class of block ciphers for which such group is easily guaranteed to be primitive. Our class includes the AES and the SERPENT.
Characterizing Learning Dynamics of Deep Neural Networks via Complex Networks
Creators: name: La Malfa, Emanuele
name: La Malfa, Gabriele
name: Nicosia, Giuseppe
name: Latora, Vito
Publisher: name: arXiv
Year: 2021
Subjects: subject: Machine Learning (cs.LG)
subject: Social and Information Networks (cs.SI)
subject: FOS: Computer and information sciences

description: In this paper, we interpret Deep Neural Networks with Complex Network Theory. Complex Network Theory (CNT) represents Deep Neural Networks (DNNs) as directed weighted graphs to study them as dynamical systems. We efficiently adapt CNT measures to examine the evolution of the learning process of DNNs with different initializations and architectures: we introduce metrics for nodes/neurons and layers, namely Nodes Strength and Layers Fluctuation. Our framework distills trends in the learning dynamics and separates low from high accurate networks. We characterize populations of neural networks (ensemble analysis) and single instances (individual analysis). We tackle standard problems of image recognition, for which we show that specific learning dynamics are indistinguishable when analysed through the solely Link-Weights analysis. Further, Nodes Strength and Layers Fluctuations make unprecedented behaviours emerge: accurate networks, when compared to under-trained models, show substantially divergent distributions with the greater extremity of deviations. On top of this study, we provide an efficient implementation of the CNT metrics for both Convolutional and Fully Connected Networks, to fasten the research in this direction.
description: IEEE/ICTAI2021 (full paper)
Enhancing Taxonomy Completion with Concept Generation via Fusing Relational Representations
Creators: name: Zeng, Qingkai
name: Lin, Jinfeng
name: Yu, Wenhao
name: Cleland-Huang, Jane
name: Jiang, Meng
Publisher: name: arXiv
Year: 2021
Subjects: subject: Computation and Language (cs.CL)
subject: FOS: Computer and information sciences

description: Automatic construction of a taxonomy supports many applications in e-commerce, web search, and question answering. Existing taxonomy expansion or completion methods assume that new concepts have been accurately extracted and their embedding vectors learned from the text corpus. However, one critical and fundamental challenge in fixing the incompleteness of taxonomies is the incompleteness of the extracted concepts, especially for those whose names have multiple words and consequently low frequency in the corpus. To resolve the limitations of extraction-based methods, we propose GenTaxo to enhance taxonomy completion by identifying positions in existing taxonomies that need new concepts and then generating appropriate concept names. Instead of relying on the corpus for concept embeddings, GenTaxo learns the contextual embeddings from their surrounding graph-based and language-based relational information, and leverages the corpus for pre-training a concept name generator. Experimental results demonstrate that GenTaxo improves the completeness of taxonomies over existing methods.
Non-rational Narain CFTs from codes over $F_4$
Creators: name: Dymarsky, Anatoly
name: Sharon, Adar
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Information Theory (cs.IT)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: We construct a map between a class of codes over $F_4$ and a family of non-rational Narain CFTs. This construction is complementary to a recently introduced relation between quantum stabilizer codes and a class of rational Narain theories. From the modular bootstrap point of view we formulate a polynomial ansatz for the partition function which reduces modular invariance to a handful of algebraic easy-to-solve constraints. For certain small values of central charge our construction yields optimal theories, i.e. those with the largest value of the spectral gap.
Cavity Quantum Electrodynamics Design with Single Photon Emitters in Hexagonal Boron Nitride
Creators: name: Wang, Yanan
name: Lee, Jaesung
name: Berezovsky, Jesse
name: Feng, Philip X. -L.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Optics (physics.optics)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Hexagonal boron nitride (h-BN), a prevalent insulating crystal for dielectric and encapsulation layers in two-dimensional (2D) nanoelectronics and a structural material in 2D nanoelectromechanical systems (NEMS), has also rapidly emerged as a promising platform for quantum photonics with the recent discovery of optically active defect centers and associated spin states. Combined with measured emission characteristics, here we propose and numerically investigate the cavity quantum electrodynamics (cavity-QED) scheme incorporating these defect-enabled single photon emitters (SPEs) in h-BN microdisk resonators. The whispering-gallery nature of microdisks can support multiple families of cavity resonances with different radial and azimuthal mode indices simultaneously, overcoming the challenges in coinciding a single point defect with the maximum electric field of an optical mode both spatially and spectrally. The excellent characteristics of h-BN SPEs, including exceptional emission rate, considerably high Debye-Waller factor, and Fourier transform limited linewidth at room temperature, render strong coupling with the ratio of coupling to decay rates g/max(γ,\k{appa}) predicated as high as 500. This study not only provides insight into the emitter-cavity interaction, but also contributes toward realizing h-BN photonic components, such as low-threshold microcavity lasers and high-purity single photon sources, critical for linear optics quantum computing and quantum networking applications.
description: 9 Pages, 5 Figures
Observations of Isolated Neutron Stars with the ESO Multi-Conjugate Adaptive Optics Demonstrator
Creators: name: Mignani, R. P.
name: Falomo, R.
name: Moretti, A.
name: Treves, A.
name: Turolla, R.
name: Sartore, N.
name: Zane, S.
name: Arcidiacono, C.
name: Lombini, M.
name: Farinato, J.
name: Baruffolo, A.
name: Ragazzoni, R.
name: Marchetti, E.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: High-energy observations have unveiled peculiar classes of isolated neutron stars which, at variance with radio pulsars, are mostly radio silent and not powered by the star rotation. Among these objects are the magnetars, hyper-magnetized neutron stars characterized by transient X-ray/gamma-ray emission, and neutron stars with purely thermal, and in most cases stationary, X-ray emission (a.k.a., X-ray dim isolated neutron stars or XDINSs). While apparently dissimilar in their high-energy behavior and age, both magnetars and XDINSs have similar periods and unusually high magnetic fields. This suggests a tantalizing scenario where the former evolve into the latter.Discovering so far uninvestigated similarities between the multi-wavelength properties of these two classes would be a further step forward to establish an evolutionary scenario. A most promising channels is the near infrared (NIR) one, where magnetars are characterized by a distinctive spectral flattening with respect to the extrapolation of the soft X-ray spectrum.We observed the two XDINSs RX J0420.0-5022 and RX J1856.5-3754 with the Multi-Conjugate Adaptive Optics Demonstrator (MAD) at the Very Large Telescope (VLT) as part of the instrument guaranteed time observations program, to search for their NIR counterparts. Both RX J1856.5-3754 and RX J0420.0-5022 were not detected down to K_s ~20 and Ks ~21.5, respectively. In order to constrain the relation between XDINSs and magnetars it would be of importance to perform deeper NIR observations. A good candidate is 1RXS J214303.7+065419 which is the XDINS with the highest inferred magnetic field.
description: Accepted for publication in Astronomy and Astrophysics