cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
What drives transient behaviour in complex systems?
Creators: name: Grela, Jacek
Publisher: name: arXiv
Year: 2017
Subjects: subject: Chaotic Dynamics (nlin.CD)
subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: We study transient behaviour in the dynamics of complex systems described by a set of non-linear ODE's. Destabilizing nature of transient trajectories is discussed and its connection with the eigenvalue-based linearization procedure. The complexity is realized as a random matrix drawn from a modified May-Wigner model. Based on the initial response of the system, we identify a novel stable-transient regime. We calculate exact abundances of typical and extreme transient trajectories finding both Gaussian and Tracy-Widom distributions known in extreme value statistics. We identify degrees of freedom driving transient behaviour as connected to the eigenvectors and encoded in a non-orthogonality matrix $T_0$. We accordingly extend the May-Wigner model to contain a phase with typical transient trajectories present. An exact norm of the trajectory is obtained in the vanishing $T_0$ limit where it describes a normal matrix.
description: 9 pages, 5 figures
Three Different Formalisations of Einstein's Relativity Principle
Creators: name: Madarász, Judit X.
name: Székely, Gergely
name: Stannett, Mike
Publisher: name: arXiv
Year: 2017
Subjects: subject: Classical Physics (physics.class-ph)
subject: Logic (math.LO)
subject: FOS: Physical sciences
subject: FOS: Mathematics
subject: 03B30, 03B10, 83A05

description: We present three natural but distinct formalisations of Einstein's special principle of relativity, and demonstrate the relationships between them. In particular, we prove that they are logically distinct, but that they can be made equivalent by introducing a small number of additional, intuitively acceptable axioms.
description: 20 pages
The concept of Cheeger deformations on fiber bundles with compact structure group
Creators: name: Cavenaghi, Leonardo F.
name: Grama, Lino
name: Sperança, Llohann D.
Publisher: name: arXiv
Year: 2018
Subjects: subject: Differential Geometry (math.DG)
subject: FOS: Mathematics

description: The purpose of this paper is two-fold: we systematically introduce the notion of Cheeger deformations on fiber bundles with compact structure groups, and recover in a very simple and unified fashion several results that either already appear in the literature or are known by experts, though are not explicitly written elsewhere. We re-prove: Schwachhöfer--Tuschmann Theorem on bi-quotients, many results due to Fukaya and Yamaguchi, as well as, naturally extend the work of Searle--Solórzano--Wilhelm on regularization properties of Cheeger deformations, among others. In this sense, this paper should be understood as a survey intended to demonstrate the power of Cheeger deformations. Even though some of the results here appearing may not be known as stated in the presented form, they were already expected, being our contribution to the standardization and spread of the technique via a unique language.
description: We have followed anonymous referee criticism and chose to present the paper mostly as a survey, though it does contain original content. This version contains some new references and changes to the abstract and introduction
Model selection and local geometry
Creators: name: Evans, Robin J.
Publisher: name: arXiv
Year: 2018
Subjects: subject: Statistics Theory (math.ST)
subject: FOS: Mathematics

description: We consider problems in model selection caused by the geometry of models close to their points of intersection. In some cases---including common classes of causal or graphical models, as well as time series models---distinct models may nevertheless have identical tangent spaces. This has two immediate consequences: first, in order to obtain constant power to reject one model in favour of another we need local alternative hypotheses that decrease to the null at a slower rate than the usual parametric $n^{-1/2}$ (typically we will require $n^{-1/4}$ or slower); in other words, to distinguish between the models we need large effect sizes or very large sample sizes. Second, we show that under even weaker conditions on their tangent cones, models in these classes cannot be made simultaneously convex by a reparameterization. This shows that Bayesian network models, amongst others, cannot be learned directly with a convex method similar to the graphical lasso. However, we are able to use our results to suggest methods for model selection that learn the tangent space directly, rather than the model itself. In particular, we give a generic algorithm for learning Bayesian network models.
The disk physical conditions of 48 Persei constrained by contemporaneous Hα spectroscopy and interferometry
Creators: name: Jones, C. E.
name: Sigut, T. A. A.
name: Grzenia, B. J.
name: Tycner, C.
name: Zavala, R. T.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We utilize a multi-step modelling process to produce synthetic interferometric and spectroscopic observables, which are then compared to their observed counterparts. Our extensive set of interferometric observations of the Be star 48 Per, totaling 291 data points, were obtained at the Navy Precision Optical Interferometer from 2006 Nov 07 to 2006 Nov 23. Our models were further constrained by comparison with contemporaneous H$α$ line spectroscopy obtained at the John S. Hall Telescope at Lowell Observatory on 2006 Nov 1. Theoretical spectral energy distributions, SEDs, for 48~Per were confirmed by comparison with observations over a wavelength regime of 0.4 to 60 microns from Touhami et al. (2010) and Vieira et al. (2017). Our best-fitting combined model from H$α$ spectroscopy, H$α$ interferometry and SED fitting has a power law density fall off, $n$, of 2.3 and an initial density at the stellar surface of $ρ_0 = 1.0 \times 10^{-11} \rm{g\,cm}^{-3}$ with a inclination constrained by H$α$ spectroscopy and interferometry of 45$^{\circ} \pm 5^{\circ}$. The position angle for the system, measured east from north, is 121$^{\circ}$ $\pm$ 1$^{\circ}$. Our best-fit model shows that the disk emission originates in a moderately large disk with a radius of 25 R$_{*}$ which is consistent with a disk mass of approximately 5 $\times$ 10$^{24}$ g or 3 $\times$ 10$^{-10}$ M$_{*}$. Finally, we compare our results with previous studies of 48~Per by Quirrenbach et al. (1997) with agreement but find, with our much larger data set, that our disk size contradicts the findings of Delaa et al. (2011).
description: 26 pages, 9 figures
A dynamical trichotomy for structured populations experiencing positive density-dependence in stochastic environments
Creators: name: Schreiber, Sebastian J.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Populations and Evolution (q-bio.PE)
subject: Dynamical Systems (math.DS)
subject: Probability (math.PR)
subject: FOS: Biological sciences
subject: FOS: Mathematics
subject: 92D25, 60J05

description: Positive density-dependence occurs when individuals experience increased survivorship, growth, or reproduction with increased population densities. Mechanisms leading to these positive relationships include mate limitation, saturating predation risk, and cooperative breeding and foraging. Individuals within these populations may differ in age, size, or geographic location and thereby structure these populations. Here, I study structured population models accounting for positive density-dependence and environmental stochasticity i.e. random fluctuations in the demographic rates of the population. Under an accessibility assumption (roughly, stochastic fluctuations can lead to populations getting small and large), these models are shown to exhibit a dynamical trichotomy: (i) for all initial conditions, the population goes asymptotically extinct with probability one, (ii) for all positive initial conditions, the population persists and asymptotically exhibits unbounded growth, and (iii) for all positive initial conditions, there is a positive probability of asymptotic extinction and a complementary positive probability of unbounded growth. The main results are illustrated with applications to spatially structured populations with an Allee effect and age-structured populations experiencing mate limitation.
Self-intersections of Laurent polynomials and the density of Jordan curves
Creators: name: Kalmykov, Sergei
name: Kovalev, Leonid V.
Publisher: name: arXiv
Year: 2019
Subjects: subject: Complex Variables (math.CV)
subject: FOS: Mathematics
subject: 30B60 (Primary), 12D10, 42A05 (Secondary)

description: We extend Quine's bound on the number of self-intersection of curves with polynomial parameterization to the case of Laurent polynomials. As an application, we show that circle embeddings are dense among all maps from a circle to a plane with respect to an integral norm.
description: 10 pages
On the Surjectivity of Certain Maps III: The Unital Set Condition
Creators: name: Kumar, C P Anil
Publisher: name: arXiv
Year: 2019
Subjects: subject: Number Theory (math.NT)
subject: Commutative Algebra (math.AC)
subject: Algebraic Geometry (math.AG)
subject: FOS: Mathematics
subject: Primary 13A15, 51N30, Secondary 11D79, 11B25, 16U60

description: In this article, for generalized projective spaces with any weights, we prove four main theorems in three different contexts where the Unital Set Condition USC (Definition $2.8$) on ideals is further examined. In the first context we prove, in the first main Theorem $A$, the surjectivity of the Chinese remainder reduction map associated to the generalized projective space of an ideal $\mathcal{I}=\underset{i=1}{\overset{k}{\prod}}\mathcal{I}_k$ with a given factorization into mutually co-maximal ideals $\mathcal{I}_j,1\leq j\leq k$ where $\mathcal{I}$ satisfies the USC, using the key concept of choice multiplier hypothesis (Definition $4.10$) which is satisfied. In the second context, for a positive $k$, we prove in the second main Theorem $Λ$, the surjectivity of the reduction map $SP_{2k}(\mathcal{R})\rightarrow SP_{2k}(\frac{\mathcal{R}}{\mathcal{I}})$ of strong approximation type for a ring $\mathcal{R}$ quotiented by an ideal $\mathcal{I}$ which satisfies the USC. In the third context, for a positive integer $k$, we prove in the thrid main Theorem $Ω$, the surjectivity of the map from special linear group of degree $(k+1)$ to the product of generalized projective spaces of $(k+1)$-mutually co-maximal ideals $\mathcal{I}_j,0\leq j\leq k$ associating the $(k+1)$-rows or $(k+1)$-columns, where the ideal $\mathcal{I}=\underset{j=0}{\overset{k}{\prod}}\mathcal{I}_j$ satisfies the USC. In the fourth main Theorem $Σ$, for a positive integer $k$, we prove the surjectivity of the map from the symplectic group of degree $2k$ to the product of generalized projective spaces of $(2k)$-mutually co-maximal ideals $\mathcal{I}_j,1\leq j\leq 2k$ associating the $(2k)$-rows or $(2k)$-columns where the ideal $\mathcal{I}=\underset{j=1}{\overset{2k}{\prod}}\mathcal{I}_j$ satisfies the USC. The answers to Questions [1.1,1.2,1.3] in a greater generality are not known.
description: 39 pages, Sequel to arXiv: 1810.03474
On arithmetic intersection numbers on self-products of curves
Creators: name: Wilms, Robert
Publisher: name: arXiv
Year: 2019
Subjects: subject: Algebraic Geometry (math.AG)
subject: Number Theory (math.NT)
subject: FOS: Mathematics
subject: 14G40

description: We give a close formula for the Néron-Tate height of tautological integral cycles on Jacobians of curves over number fields as well as a new lower bound for the arithmetic self-intersection number $\hatω^2$ of the dualizing sheaf of a curve in terms of Zhang's invariant $φ$. As an application, we obtain an effective Bogomolov-type result for the tautological cycles. We deduce these results from a more general combinatorial computation of arithmetic intersection numbers of adelic line bundles on higher self-products of curves, which are linear combinations of pullbacks of line bundles on the curve and the diagonal bundle.
description: 22 pages. Comments are welcome!
Machine Learning Construction: implications to cybersecurity
Creators: name: Yousef, Waleed A.
Publisher: name: arXiv
Year: 2019
Subjects: subject: Machine Learning (cs.LG)
subject: Machine Learning (stat.ML)
subject: FOS: Computer and information sciences

description: Statistical learning is the process of estimating an unknown probabilistic input-output relationship of a system using a limited number of observations. A statistical learning machine (SLM) is the algorithm, function, model, or rule, that learns such a process; and machine learning (ML) is the conventional name of this field. ML and its applications are ubiquitous in the modern world. Systems such as Automatic target recognition (ATR) in military applications, computer aided diagnosis (CAD) in medical imaging, DNA microarrays in genomics, optical character recognition (OCR), speech recognition (SR), spam email filtering, stock market prediction, etc., are few examples and applications for ML; diverse fields but one theory. In particular, ML has gained a lot of attention in the field of cyberphysical security, especially in the last decade. It is of great importance to this field to design detection algorithms that have the capability of learning from security data to be able to hunt threats, achieve better monitoring, master the complexity of the threat intelligence feeds, and achieve timely remediation of security incidents. The field of ML can be decomposed into two basic subfields: \textit{construction} and \textit{assessment}. We mean by \textit{construction} designing or inventing an appropriate algorithm that learns from the input data and achieves a good performance according to some optimality criterion. We mean by \textit{assessment} attributing some performance measures to the constructed ML algorithm, along with their estimators, to objectively assess this algorithm. \textit{Construction} and \textit{assessment} of a ML algorithm require familiarity with different other fields: probability, statistics, matrix theory, optimization, algorithms, and programming, among others.f
Microstructure under the Microscope: Tools to Survive and Thrive in The Age of (Too Much) Information
Creators: name: Kashyap, Ravi
Publisher: name: arXiv
Year: 2017
Subjects: subject: Trading and Market Microstructure (q-fin.TR)
subject: FOS: Economics and business

description: Market Microstructure is the investigation of the process and protocols that govern the exchange of assets with the objective of reducing frictions that can impede the transfer. In financial markets, where there is an abundance of recorded information, this translates to the study of the dynamic relationships between observed variables, such as price, volume and spread, and hidden constituents, such as transaction costs and volatility, that hold sway over the efficient functioning of the system. "My dear, here we must process as much data as we can, just to stay in business. And if you wish to make a profit you must process at least twice as much data." - Red Queen to Alice in Hedge-Fund-Land. In this age of (Too Much) Information, it is imperative to uncover nuggets of knowledge (signal) from buckets of nonsense (noise). To aid in this effort to extract meaning from chaos and to gain a better understanding of the relationships between financial variables, we summarize the application of the theoretical results from (Kashyap 2016b) to microstructure studies. The central concept rests on a novel methodology based on the marriage between the Bhattacharyya distance, a measure of similarity across distributions, and the Johnson Lindenstrauss Lemma, a technique for dimension reduction, providing us with a simple yet powerful tool that allows comparisons between data-sets representing any two distributions. We provide an empirical illustration using prices, volumes and volatilities across seven countries and three different continents. The degree to which different markets or sub groups of securities have different measures of their corresponding distributions tells us the extent to which they are different. This can aid investors looking for diversification or looking for more of the same thing.
description: arXiv admin note: substantial text overlap with arXiv:1603.09060
Machine Learning Assessment: implications to cybersecurity
Creators: name: Yousef, Waleed A.
Publisher: name: arXiv
Year: 2019
Subjects: subject: Machine Learning (stat.ML)
subject: Machine Learning (cs.LG)
subject: FOS: Computer and information sciences

description: This chapter is dedicated to the assessment and performance estimation of machine learning (ML) algorithms, a topic that is equally important to the construction of these algorithms, in particular in the context of cyberphysical security design. The literature is full of nonparametric methods to estimate a statistic from just one available dataset through resampling techniques, e.g., jackknife, bootstrap and cross validation (CV). Special statistics of great interest are the error rate and the area under the ROC curve (AUC) of a classification rule. The importance of these resampling methods stems from the fact that they require no knowledge about the probability distribution of the data or the construction details of the ML algorithm. This chapter provides a concise review of this literature to establish a coherent theoretical framework for these methods that can estimate both the error rate (a one-sample statistic) and the AUC (a two-sample statistic). The resampling methods are usually computationally expensive, because they rely on repeating the training and testing of a ML algorithm after each resampling iteration. Therefore, the practical applicability of some of these methods may be limited to the traditional ML algorithms rather than the very computationally demanding approaches of the recent deep neural networks (DNN). In the field of cyberphysical security, many applications generate structured (tabular) data, which can be fed to all traditional ML approaches. This is in contrast to the DNN approaches, which favor unstructured data, e.g., images, text, voice, etc.; hence, the relevance of this chapter to this field.%
Interplay between magnetism, superconductivity, and orbital order in a 5-pocket model for iron-based superconductors - a parquet renormalization group study
Creators: name: Classen, Laura
name: Xing, Rui-Qi
name: Khodas, Maxim
name: Chubukov, Andrey V.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We report the results of the parquet renormalization group (RG) analysis of the phase diagram of the most general 5-pocket model for Fe-based superconductors. We use as an input the orbital structure of excitations near the five pockets made out of $d_{xz}$, $d_{yz}$, and $d_{xy}$ orbitals and argue that there are 40 different interactions between low-energy fermions in the orbital basis. All interactions flow under RG, as one progressively integrates out fermions with higher energies. We find that the low-energy behavior is amazingly simple, despite the large number of interactions. Namely, at low-energies the full 5-pocket model effectively reduces either to a 3-pocket model made of one $d_{xy}$ hole pocket and two electron pockets, or a 4-pocket model made of two $d_{xz}/d_{yz}$ hole pockets and two electron pockets. The leading instability in the effective 4-pocket model is a spontaneous orbital (nematic) order, followed by $s^{+-}$ superconductivity. In the effective 3-pocket model orbital fluctuations are weaker, and the system develops either $s^{+-}$ superconductivity or stripe SDW. In the latter case, nematicity is induced by composite spin fluctuations.
description: 5+12 pages, 3+9 figures
Positive Ricci curvature on fiber bundles with compact structure group
Creators: name: Cavenaghi, Leonardo Francisco
name: Sperança, Llohann Dallagnol
Publisher: name: arXiv
Year: 2019
Subjects: subject: Differential Geometry (math.DG)
subject: FOS: Mathematics

description: The aim of this paper is to present a direct and simple proof of a result concerning the existence of metrics of positive Ricci curvature on the total space of fiber bundles with compact structure groups. In particular, it also generalizes and puts in a unified framework the results in Nash \cite{nash} and Poor \cite{poor}. With the intention of disseminating this result, we apply it to build new examples of manifolds with positive Ricci curvature, including bundles whose base consists of gradient shrinking Ricci solitons.
description: Exposition substantially improved. Examples added
Algebraic Properties of Gaussian HTC-identifiable Graphs
Creators: name: Yao, Bohao
name: Evans, Robin
Publisher: name: arXiv
Year: 2019
Subjects: subject: Statistics Theory (math.ST)
subject: FOS: Mathematics

description: In this paper, we explore some algebraic properties of linear structural equation modelsthat can be represented by an HTC-identifiable graph. In particular, we prove that all mixedgraphs are HTC-identifiable if and only if all the regression coefficients can be recovered fromthe covariance matrix using straightforward linear algebra operations. We also find a set ofpolynomials that generates the ideal that encompasses all the equality constraints of the modelon the cone of positive definite matrices. We further prove that this set of polynomials are theminimal generators of said ideal for a subset of HTC-identifiable graphs.
High efficiency deep-UV emission at 219 nm from ultrathin MBE GaN/AlN quantum heterostructures
Creators: name: Islam, SM
name: Protasenko, Vladimir
name: Lee, Kevin
name: Rouvimov, Sergei
name: Verma, Jai
name: Huili
name: Xing
name: Jena, Debdeep
Publisher: name: arXiv
Year: 2017
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Deep ultraviolet (UV) optical emission below 250 nm (~5 eV) in semiconductors is traditionally obtained from high aluminum containing AlGaN alloy quantum wells. It is shown here that high-quality epitaxial ultrathin binary GaN quantum disks embedded in an AlN matrix can produce efficient optical emission in the 219-235 nm (~5.7 to 5.3 eV) spectral range, far above the bulk bandgap (3.4 eV) of GaN. The quantum confinement energy in these heterostructures is larger than the bandgaps of traditional semiconductors, made possible by the large band offsets. These MBE-grown extreme quantum-confinement GaN/AlN heterostructures exhibit internal quantum efficiency as high as 40% at wavelengths as short as 219 nm. These observations, together with the ability to engineer the interband optical matrix elements to control the direction of photon emission in such new binary quantum disk active regions offers unique advantages over alloy AlGaN quantum well counterparts for the realization of deep-UV light-emitting diodes and lasers.
description: 5 pages, 4 figures
Private Summation in the Multi-Message Shuffle Model
Creators: name: Balle, Borja
name: Bell, James
name: Gascon, Adria
name: Nissim, Kobbi
Publisher: name: arXiv
Year: 2020
Subjects: subject: Cryptography and Security (cs.CR)
subject: FOS: Computer and information sciences

description: The shuffle model of differential privacy (Erlingsson et al. SODA 2019; Cheu et al. EUROCRYPT 2019) and its close relative encode-shuffle-analyze (Bittau et al. SOSP 2017) provide a fertile middle ground between the well-known local and central models. Similarly to the local model, the shuffle model assumes an untrusted data collector who receives privatized messages from users, but in this case a secure shuffler is used to transmit messages from users to the collector in a way that hides which messages came from which user. An interesting feature of the shuffle model is that increasing the amount of messages sent by each user can lead to protocols with accuracies comparable to the ones achievable in the central model. In particular, for the problem of privately computing the sum of $n$ bounded real values held by $n$ different users, Cheu et al. showed that $O(\sqrt{n})$ messages per user suffice to achieve $O(1)$ error (the optimal rate in the central model), while Balle et al. (CRYPTO 2019) recently showed that a single message per user leads to $Θ(n^{1/3})$ MSE (mean squared error), a rate strictly in-between what is achievable in the local and central models. This paper introduces two new protocols for summation in the shuffle model with improved accuracy and communication trade-offs. Our first contribution is a recursive construction based on the protocol from Balle et al. mentioned above, providing $\mathrm{poly}(\log \log n)$ error with $O(\log \log n)$ messages per user. The second contribution is a protocol with $O(1)$ error and $O(1)$ messages per user based on a novel analysis of the reduction from secure summation to shuffling introduced by Ishai et al. (FOCS 2006) (the original reduction required $O(\log n)$ messages per user).
description: Published at CCS'20
Anti-Unwinding Sliding Mode Attitude Maneuver Control for Rigid Spacecraft
Creators: name: Dong, Rui-Qi
name: Wu, Ai-Guo
name: Zhang, Ying
Publisher: name: arXiv
Year: 2020
Subjects: subject: Systems and Control (eess.SY)
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: In this paper, anti-unwinding attitude maneuver control for rigid spacecraft is considered. First, in order to avoid the unwinding phenomenon when the system states are restricted to the switching surface, a novel switching function is constructed by hyperbolic sine functions such that the switching surface contains two equilibriums. Then, a sliding mode attitude maneuver controller is designed based on the constructed switching function to ensure the robustness of the closed-loop attitude maneuver control system to disturbance. Another important feature of the developed attitude control law is that a dynamic parameter is introduced to guarantee the anti-unwinding performance before the system states reach the switching surface. The simulation results demonstrate that the unwinding problem is settled during attitude maneuver for rigid spacecraft by adopting the newly constructed switching function and proposed attitude control scheme.
description: 8 pages, 8 figures
Portfolio-driven Resource Management for Transient Cloud Servers
Creators: name: Sharma, Prateek
name: Irwin, David
name: Shenoy, Prashant
Publisher: name: arXiv
Year: 2017
Subjects: subject: Distributed, Parallel, and Cluster Computing (cs.DC)
subject: FOS: Computer and information sciences

description: Cloud providers have begun to offer their surplus capacity in the form of low-cost transient servers, which can be revoked unilaterally at any time. While the low cost of transient servers makes them attractive for a wide range of applications, such as data processing and scientific computing, failures due to server revocation can severely degrade application performance. Since different transient server types offer different cost and availability tradeoffs, we present the notion of server portfolios that is based on financial portfolio modeling. Server portfolios enable construction of an "optimal" mix of severs to meet an application's sensitivity to cost and revocation risk. We implement model-driven portfolios in a system called ExoSphere, and show how diverse applications can use portfolios and application-specific policies to gracefully handle transient servers. We show that ExoSphere enables widely-used parallel applications such as Spark, MPI, and BOINC to be made transiency-aware with modest effort. Our experiments show that allowing the applications to use suitable transiency-aware policies, ExoSphere is able to achieve 80\% cost savings when compared to on-demand servers and greatly reduces revocation risk compared to existing approaches.
Sliding Mode Attitude Maneuver Control for Rigid Spacecraft without Unwinding
Creators: name: Dong, Rui-Qi
name: Wu, Ai-Guo
name: Zhang, Ying
Publisher: name: arXiv
Year: 2020
Subjects: subject: Systems and Control (eess.SY)
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: In this paper, attitude maneuver control without unwinding phenomenon is investigated for rigid spacecraft. First, a novel switching function is constructed by a hyperbolic sine function. It is shown that the spacecraft system possesses the unwinding-free performance when the system states are on the sliding surface. Based on the designed switching function, a sliding mode controller is developed to ensure the robustness of the attitude maneuver control system. Another essential feature of the presented attitude control law is that a dynamic parameter is introduced to guarantee the unwinding-free performance when the system states are outside the sliding surface. The simulation results demonstrate that the unwinding phenomenon is avoided during the attitude maneuver of a rigid spacecraft by adopting the constructed switching function and the proposed attitude control scheme.
description: 8 Pages, 8 figures. arXiv admin note: text overlap with arXiv:2004.07001
Solution of Relativistic Feshbach-Villars Spin-1/2 Equations
Creators: name: Wingard, D.
name: Vallejo, A. Garcia
name: Papp, Z.
Publisher: name: arXiv
Year: 2024
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We propose method for studying relativistic spin-$1/2$ particles by solving the corresponding Feshbach-Villars equation. We have found that the Feshbach-Villars spin-$1/2$ equations can be formulated as spin-coupled Feshbach-Villars spin-$0$ equations, that results in a Hamiltonian eigenvalue problem. We adopted an integral equation formalism. The potential operators are represented in a discrete Hilbert space basis and the relevant Green's operator has been calculated by a matrix continued fraction.
description: 7 pages
Finding the elephant in the room
Creators: name: Research, Nature
Publisher: name: Manara - Qatar Research Repository
Year: 2023
Subjects: classificationCode: 32
subject: Biomedical and clinical sciences
classificationCode: 3202
subject: Clinical sciences

description: Filariasis affects 120 million people in tropical and sub-tropical countries and involves infection, by means of a mosquito bite, with microscopic worms called microfilaria. These worms enter through the skin and travel to the lymph vessels, where they can grow into adults and live for up to seven years. When adults mate, they release millions of microfilaria into the blood stream.Most people with filariasis don’t have any symptoms, but sometimes these worms block the lymph vessels and cause severe swellings. Extreme cases lead to elephant-looking limbs, a condition called elephantiasis An Indian man working in Qatar for two years, where filariasis has only been reported once previously, was recently diagnosed with the disease. His physicians say his case demonstrates the importance of having a high degree of clinical suspicion while evaluating patients with unusual signs and symptoms.The 38-year-old man was admitted into Hamad General Hospital in Doha with fever, chills, shortness of breath and a tender, warm swelling on his right thigh. An ultrasound performed on the swelling revealed the “filarial dance sign”, which shows the twirling movement of microfilaria. Although rarely documented, this is considered a diagnostic sign of filariasis. Fine-needle aspiration from the swelling confirmed the presence of microfilaria.Both of these findings are unusual in cases of filariasis, which is usually diagnosed by finding microfilaria in the bloodstream. However, they did not show up in blood tests done on this patient.The patient was admitted to hospital and given a single dose of the anti-parasitic worm drug ivermectin. He was also given a diuretic to get rid of water accumulation in the body due to lymphatic obstruction, which was causing the patient’s chest and breathing symptoms. The leg swelling was also opened and drained the following day. The patient was kept in hospital and given anti-filaria treatment for two weeks, after which he was discharged from hospital due to resolution of his signs and symptoms. He was only put on an antibiotic for a further four weeks.“The diagnosis of filariasis can be easily missed if physicians are unaware of its possible presence, especially in cases where presentation is atypical and unusual”, write the physicians in their case report published in the Qatar Medical Journal. The team believe the case demonstrates the importance of diagnostic tools such as ultrasound and fine needle aspiration, along with thorough clinical analysis, in evaluating patients with soft tissue lesions.Other InformationPublished in: QScience.com Highlights, Published by Nature Research for Hamad bin Khalifa University Press (HBKU Press)
License: http://creativecommons.org/licenses/by/4.0
Tweet for Behavior Change: Using Social Media for the Dissemination of Public Health Messages
Creators: name: Gough, Aisling
name: Hunter, Ruth F
name: Ajao, Oluwaseun
name: Jurek, Anna
name: McKeown, Gary
name: Hong, Jun
name: Barrett, Eimear
name: Ferguson, Marbeth
name: McElwee, Gerry
name: McCarthy, Miriam
name: Kee, Frank
Publisher: name: arXiv
Year: 2017
Subjects: subject: Social and Information Networks (cs.SI)
subject: FOS: Computer and information sciences
subject: K.4.2; H.3.3; H.2.8

description: Background: Social media public health campaigns have the advantage of tailored messaging at low cost and large reach, but little is known about what would determine their feasibility as tools for inducing attitude and behavior change. Objective: The aim of this study was to test the feasibility of designing, implementing, and evaluating a social media-enabled intervention for skin cancer prevention. Conclusions: Social media-disseminated public health messages reached more than 23% of the Northern Ireland population. A Web-based survey suggested that the campaign might have contributed to improved knowledge and attitudes toward skin cancer among the target population. Findings suggested that shocking and humorous messages generated greatest impressions and engagement, but information-based messages were likely to be shared most. The extent of behavioral change as a result of the campaign remains to be explored, however, the change of attitudes and knowledge is promising. Social media is an inexpensive, effective method for delivering public health messages. However, existing and traditional process evaluation methods may not be suitable for social media.
description: 17 pages published in Journal of Medical Internet Research - JMIR Public Health Surveillance, March 2017
A characterization of graphs with regular distance-$2$ graphs
Creators: name: Gaar, Elisabeth
name: Krenn, Daniel
Publisher: name: arXiv
Year: 2020
Subjects: subject: Combinatorics (math.CO)
subject: FOS: Mathematics
subject: 05C75, 05C12, 05C07, 05C30, 05C76

description: For non-negative integers~$k$, we consider graphs in which every vertex has exactly $k$ vertices at distance~$2$, i.e., graphs whose distance-$2$ graphs are $k$-regular. We call such graphs $k$-metamour-regular motivated by the terminology in polyamory. While constructing $k$-metamour-regular graphs is relatively easy -- we provide a generic construction for arbitrary~$k$ -- finding all such graphs is much more challenging. We show that only $k$-metamour-regular graphs with a certain property cannot be built with this construction. Moreover, we derive a complete characterization of $k$-metamour-regular graphs for each $k=0$, $k=1$ and $k=2$. In particular, a connected graph with~$n$ vertices is $2$-metamour-regular if and only if $n\ge5$ and the graph is a join of complements of cycles (equivalently every vertex has degree~$n-3$), a cycle, or one of $17$ exceptional graphs with $n\le8$. Moreover, a characterization of graphs in which every vertex has at most one metamour is acquired. Each characterization is accompanied by an investigation of the corresponding counting sequence of unlabeled graphs.
Physiological, anatomical, and behavioral investigations on the bed nucleus of the stria terminalis
Creators: name: Rodríguez-Sierra, Olga E.
Publisher: name: No Publisher Supplied
Year: 2014

description: The anterior part of the bed nucleus of the stria terminalis (BNST-A) has emerged as a critical structure mediating fear and anxiety-like behavior. It is strategically situated to integrate information from limbic forebrain regions such as the amygdala, prefrontal cortex and hippocampus; and influence major fear and stress output effectors. Previous pharmacobehavioral studies have assumed that the BNST is a homogeneous structure despite the fact that anatomical studies contradict this assumption. The work presented in this thesis aimed to systematically examine the functional organization of BNST-A and its relation to anxiety-like behavior. In the first chapter, I examined the electroresponsive and morphological properties of BNST-A neurons. I showed that there are two dominant BNST-A cell types intermingled with at least other three less numerous cell types. In the second chapter, I investigated the intrinsic connections of BNST-A with the use of glutamate uncaging (GU). Overall, GU usually elicited inhibitory postsynaptic potentials and the incidence of intraregional connections was higher than interregional links. Lastly, I investigated the physiological properties of BNST-A neurons in a rat model of post-traumatic stress disorder. I show that neurons in BNST-A regions exhibit opposing alterations in synaptic responsiveness, supporting the idea that BNST-A is physiologically heterogeneous, with some regions exerting anxiolytic and others anxiogenic influences.
Backdoors in Neural Models of Source Code
Creators: name: Ramakrishnan, Goutham
name: Albarghouthi, Aws
Publisher: name: arXiv
Year: 2020
Subjects: subject: Machine Learning (cs.LG)
subject: Cryptography and Security (cs.CR)
subject: Machine Learning (stat.ML)
subject: FOS: Computer and information sciences

description: Deep neural networks are vulnerable to a range of adversaries. A particularly pernicious class of vulnerabilities are backdoors, where model predictions diverge in the presence of subtle triggers in inputs. An attacker can implant a backdoor by poisoning the training data to yield a desired target prediction on triggered inputs. We study backdoors in the context of deep-learning for source code. (1) We define a range of backdoor classes for source-code tasks and show how to poison a dataset to install such backdoors. (2) We adapt and improve recent algorithms from robust statistics for our setting, showing that backdoors leave a spectral signature in the learned representation of source code, thus enabling detection of poisoned data. (3) We conduct a thorough evaluation on different architectures and languages, showing the ease of injecting backdoors and our ability to eliminate them.
A Square Equal-area Map Projection with Low Angular Distortion, Minimal Cusps, and Closed-form Solutions
Creators: name: Petroff, Matthew A.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Graphics (cs.GR)
subject: Geophysics (physics.geo-ph)
subject: FOS: Computer and information sciences
subject: FOS: Physical sciences

description: A novel square equal-area map projection is proposed. The projection combines closed-form forward and inverse solutions with relatively low angular distortion and minimal cusps, a combination of properties not manifested by any previously published square equal-area projection. Thus, the new projection has lower angular distortion than any previously published square equal-area projection with a closed-form solution. Utilizing a quincuncial arrangement, the new projection places the north pole at the center of the square and divides the south pole between its four corners; the projection can be seamlessly tiled. The existence of closed-form solutions makes the projection suitable for real-time visualization applications, both in cartography and in other areas, such as for the display of panoramic images.
description: 17 pages, 6 figures, 1 table; corrections to Appendix A
Behavioral and physiological assessment of an animal model of post-traumatic stress disorder
Creators: name: Goswami, Sonal
Publisher: name: No Publisher Supplied
Year: 2013

description: Post-traumatic stress disorder (PTSD) is an anxiety disorder triggered by exposure to a traumatic event. Despite recent progress, the causes and pathophysiology of PTSD remain poorly understood, partly because of ethical limitations inherent to human studies. One approach to circumvent this obstacle is to study PTSD in a valid animal model of the human syndrome. In one such model, extreme and long-lasting behavioral manifestations of anxiety develop in a subset of Lewis rats after exposure to an intense predator threat (PT) that mimics the type of life-or-death situation known to precipitate PTSD in humans. Thus, the first half of this thesis tested whether the Lewis rat model reproduces salient features of human PTSD. The results of these studies established the model’s face validity. The second half of this thesis used this model to identify alterations in the physiological properties of amygdala neurons that underlie the expression of PTSD. These studies revealed that PTSD is associated with differences in the synaptic responsiveness of central amygdala (CeA) neurons. Overall, these results suggest that the Lewis rat model of PTSD can be used to gain mechanistic insights in the pathophysiology of PTSD.
Inverse problems on low-dimensional manifolds
Creators: name: Alberti, Giovanni S.
name: Arroyo, Ángel
name: Santacesaria, Matteo
Publisher: name: arXiv
Year: 2020
Subjects: subject: Functional Analysis (math.FA)
subject: Analysis of PDEs (math.AP)
subject: Differential Geometry (math.DG)
subject: FOS: Mathematics
subject: 35R30, 58C25

description: We consider abstract inverse problems between infinite-dimensional Banach spaces. These inverse problems are typically nonlinear and ill-posed, making the inversion with limited and noisy measurements a delicate process. In this work, we assume that the unknown belongs to a finite-dimensional manifold: this assumption arises in many real-world scenarios where natural objects have a low intrinsic dimension and belong to a certain submanifold of a much larger ambient space. We prove uniqueness and Hölder and Lipschitz stability results in this general setting, also in the case when only a finite discretization of the measurements is available. Then, a Landweber-type reconstruction algorithm from a finite number of measurements is proposed, for which we prove global convergence, thanks to a new criterion for finding a suitable initial guess. These general results are then applied to several examples, including two classical nonlinear ill-posed inverse boundary value problems. The first is Calderón's inverse conductivity problem, for which we prove a Lipschitz stability estimate from a finite number of measurements for piece-wise constant conductivities with discontinuities on an unknown triangle. A similar stability result is then obtained for Gel'fand-Calderón's problem for the Schrödinger equation, in the case of piece-wise constant potentials with discontinuities on a finite number of non-intersecting balls.
description: 70 pages, 5 figures. This revised version contains the application of the abstract results to the Calder\'on problem with a triangular inclusion and to the Gel'fand-Calder\'on problem with piecewise constant potentials on non-intersecting balls
Holomorphic Function Spaces on Homogeneous Siegel Domains
Creators: name: Calzi, Mattia
name: Peloso, Marco M.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Complex Variables (math.CV)
subject: FOS: Mathematics
subject: 42B35, 32M15

description: We study several connected problems of holomorphic function spaces on homogeneous Siegel domains. The main object of our study concerns weighted mixed norm Bergman spaces on homogeneous Siegel domains of type II. These problems include: sampling, atomic decomposition, duality, boundary values, boundedness of the Bergman projectors. Our analysis include the Hardy spaces, and suitable generalizations of the classical Bloch and Dirichlet spaces. One of the main novelties in this work is the generality of the domains under consideration, that is, homogeneous Siegel domains, extending many results from the more particular cases of the upper half-plane, Siegel domains of tube type over irreducible cones, or symmetric, irreducible Siegel domains of type II.
description: 135 pages + Corrigendum
Non-reciprocal quantum Hall devices with driven edge magnetoplasmons in 2-dimensional materials
Creators: name: Bosco, Stefano
name: DiVincenzo, David Peter
Publisher: name: arXiv
Year: 2017
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We develop a theory that describes the response of non-reciprocal devices employing 2-dimensional materials in the quantum Hall regime capacitively coupled to external electrodes. As the conduction in these devices is understood to be associated to the edge magnetoplasmons (EMPs), we first investigate the EMP problem by using the linear response theory in the random phase approximation. Our model can incorporate several cases, that were often treated on different grounds in literature. In particular, we analyze plasmonic excitations supported by smooth and sharp confining potential in 2-dimensional electron gas, and in monolayer graphene, and we point out the similarities and differences in these materials. We also account for a general time-dependent external drive applied to the system. Finally, we describe the behavior of a non-reciprocal quantum Hall device: the response contains additional resonant features, which were not foreseen from previous models.
Projectors separating spectra for $L^2$ on pseudounitary groups $U(p,q)$
Creators: name: Neretin, Yury A.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Representation Theory (math.RT)
subject: Functional Analysis (math.FA)
subject: Group Theory (math.GR)
subject: FOS: Mathematics
subject: 22E30, 22E46, 43A30, 43A80, 43A85

description: The spectrum of $L^2$ on a pseudo-unitary group $U(p,q)$ (we assume $p\ge q$ naturally splits into $q+1$ types. We write explicitly orthogonal projectors in $L^2$ to subspaces with uniform spectra (this is an old question formulated by Gelfand and Gindikin). We also write two finer separations of $L^2$. In the first case pieces are enumerated by $r=0$, 1,..., $q$ and representations of discrete series of $U(p-r,q-r)$, where $r=0$, \dots, $q$. In the second case pieces are enumerated by all discrete parameters of the tempered spectrum of $U(p,q)$.
description: 24p