cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
The limits of SDP relaxations for general-valued CSPs
Creators: name: Thapper, Johan
name: Zivny, Stanislav
Publisher: name: arXiv
Year: 2016
Subjects: subject: Computational Complexity (cs.CC)
subject: Logic in Computer Science (cs.LO)
subject: FOS: Computer and information sciences
subject: F.2.0

description: It has been shown that for a general-valued constraint language $Γ$ the following statements are equivalent: (1) any instance of $\operatorname{VCSP}(Γ)$ can be solved to optimality using a constant level of the Sherali-Adams LP hierarchy; (2) any instance of $\operatorname{VCSP}(Γ)$ can be solved to optimality using the third level of the Sherali-Adams LP hierarchy; (3) the support of $Γ$ satisfies the "bounded width condition", i.e., it contains weak near-unanimity operations of all arities. We show that if the support of $Γ$ violates the bounded width condition then not only is $\operatorname{VCSP}(Γ)$ not solved by a constant level of the Sherali-Adams LP hierarchy but it is also not solved by $Ω(n)$ levels of the Lasserre SDP hierarchy (also known as the sum-of-squares SDP hierarchy). For $Γ$ corresponding to linear equations in an Abelian group, this result follows from existing work on inapproximability of Max-CSPs. By a breakthrough result of Lee, Raghavendra, and Steurer [STOC'15], our result implies that for any $Γ$ whose support violates the bounded width condition no SDP relaxation of polynomial-size solves $\operatorname{VCSP}(Γ)$. We establish our result by proving that various reductions preserve exact solvability by the Lasserre SDP hierarchy (up to a constant factor in the level of the hierarchy). Our results hold for general-valued constraint languages, i.e., sets of functions on a fixed finite domain that take on rational or infinite values, and thus also hold in notable special cases of $\{0,\infty\}$-valued languages (CSPs), $\{0,1\}$-valued languages (Min-CSPs/Max-CSPs), and $\mathbb{Q}$-valued languages (finite-valued CSPs).
description: Full version of a LICS'17 paper. Builds on and extends arXiv:1606.02577. arXiv admin note: text overlap with arXiv:1606.02577
Crystal field splittings in rare earth-based hard magnets: an ab initio approach
Creators: name: Delange, Pascal
name: Biermann, Silke
name: Miyake, Takashi
name: Pourovskii, Leonid
Publisher: name: arXiv
Year: 2017
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We apply the first-principles density functional theory + dynamical mean field theory framework to evaluate the crystal field splitting on rare earth sites in hard magnetic intermetallics. An atomic (Hubbard-I) approximation is employed for local correlations on the rare earth 4$f$ shell and self-consistency in the charge density is implemented. We reduce the density functional theory self-interaction contribution to the crystal field splitting by properly averaging the 4$f$ charge density before recalculating the one-electron Kohn-Sham potential. Our approach is shown to reproduce the experimental crystal field splitting in the prototypical rare earth hard magnet SmCo$_5$. Applying it to $R$Fe$_{12}$ and $R$Fe$_{12}X$ hard magnets ($R=$Nd, Sm and $X=$N, Li), we obtain in particular a large positive value of the crystal field parameter $A_2^0\langle r^2\rangle$ in NdFe$_{12}$N resulting in a strong out-of-plane anisotropy observed experimentally. The sign of $A_2^0\langle r^2\rangle$ is predicted to be reversed by substituting N with Li, leading to a strong out-of-plane anisotropy in SmFe$_{12}$Li. We discuss the origin of this strong impact of N and Li interstitials on the crystal field splitting on rare earth sites.
description: 17 pages, 11 figures
Valley Isospin Controlled Fractional Quantum Hall States in Bilayer Graphene
Creators: name: Huang, Ke
name: Fu, Hailong
name: Hickey, Danielle Reifsnyder
name: Alem, Nasim
name: Lin, Xi
name: Watanabe, Kenji
name: Taniguchi, Takashi
name: Zhu, Jun
Publisher: name: arXiv
Year: 2021
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: A two-dimensional electron system placed in a magnetic field develops Landau levels, where strong Coulomb interactions lead to the appearance of many-body correlated ground states. Quantum numbers similar to the electron spin enable the understanding and control of complex ground state order and collective excitations. Owing to its spin, valley and orbital degrees of freedom, Bernal-stacked bilayer graphene offers a rich platform to pursue correlated phenomena in two dimensions. In this work, we fabricate dual-gated Bernal-stacked bilayer graphene devices and demonstrate unprecedented fine control over its valley isospin degrees of freedom using a perpendicular electric field. Higher sample quality enables us to probe regimes obscured by disorder in previous studies. We present evidence for a new even-denominator fractional quantum Hall state at filling factor ν = 5/2. The 5/2 state is found to be spontaneously valley polarized in the limit of vanishing valley Zeeman splitting, consistent with a theoretical prediction made regarding the spin polarization of the Moore-Read state. In the vicinity of the even-denominator fractional quantum Hall states, we observe the appearance of the predicted Levin-Halperin daughter states of the Moore-Read Pfaffian wave function at ν= 3/2, 7/2, and -1/2 and of the anti-Pfaffian at ν= 5/2. These observations suggest the breaking of particle-hole symmetry in bilayer graphene. We construct a comprehensive valley polarization phase diagram for the Jain sequence fractional states surrounding filling factor 3/2. These results are well explained by a two-component composite fermion model, further demonstrating the SU(2) nature of the valley isospin in bilayer graphene. Our experiment paves the path for future efforts of manipulating the valley isospin in bilayer graphene to engineer exotic topological orders and quantum information processes.
description: 24 pages, 14 figures. The changes reported in the erratum are included in the latest version
Pairing symmetries in the Zeeman-coupled extended attractive Hubbard model
Creators: name: Nayak, Swagatam
name: Batra, Navketan
name: Kumar, Sanjeev
Publisher: name: arXiv
Year: 2021
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: By introducing the possibility of equal- and opposite-spin pairings concurrently, we show that the extended attractive Hubbard model (EAHM) exhibits rich ground state phase diagrams with a variety of singlet, triplet, and mixed parity superconducting orders. We study the competition between these superconducting pairing symmetries invoking an unrestricted Hartree-Fock- Bogoliubov-de Gennes (HFBdG) mean-field approach, and we use the d-vector formalism to characterize the nature of the stabilized superconducting orders. We discover that, while all other types of orders are suppressed, a non-unitary triplet order dominates the phase space in the presence of an in-plane external magnetic field. We also find a transition between a non-unitary to unitary superconducting phase driven by the change in average electron density. Our results serve as a reference for identifying and understanding the nature of superconductivity based on the symmetries of the pairing correlations. The results further highlight that EAHM is a suitable effective model for describing most of the pairing symmetries discovered in different materials.
A metrical approach to Finsler geometry
Creators: name: Minguzzi, E.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Differential Geometry (math.DG)
subject: FOS: Mathematics

description: In the standard approach to Finsler geometry the metric is defined as a vertical Hessian and the Chern or Cartan connections appear as just two among many possible natural linear connections on the pullback tangent bundle. Here it is shown that the Hessian nature of the metric, the non-linear connection and the Chern or Cartan connections can be derived from a few compatibility axioms between metric and Finsler connection. This result provides a metrical formulation of Finsler geometry which is well adapted to field theory, and which has proved useful in Einstein-Cartan-like approaches to Finsler gravity.
description: Latex, 24 pages. v2: minor changes in the introduction
Combining Machine Learning Classifiers for Stock Trading with Effective Feature Extraction
Creators: name: Ullah, A. K. M. Amanat
name: Imtiaz, Fahim
name: Ihsan, Miftah Uddin Md
name: Alam, Md. Golam Rabiul
name: Majumdar, Mahbub
Publisher: name: arXiv
Year: 2021
Subjects: subject: Trading and Market Microstructure (q-fin.TR)
subject: Computational Engineering, Finance, and Science (cs.CE)
subject: Machine Learning (cs.LG)
subject: FOS: Economics and business
subject: FOS: Computer and information sciences

description: The unpredictability and volatility of the stock market render it challenging to make a substantial profit using any generalised scheme. Many previous studies tried different techniques to build a machine learning model, which can make a significant profit in the US stock market by performing live trading. However, very few studies have focused on the importance of finding the best features for a particular trading period. Our top approach used the performance to narrow down the features from a total of 148 to about 30. Furthermore, the top 25 features were dynamically selected before each time training our machine learning model. It uses ensemble learning with four classifiers: Gaussian Naive Bayes, Decision Tree, Logistic Regression with L1 regularization, and Stochastic Gradient Descent, to decide whether to go long or short on a particular stock. Our best model performed daily trade between July 2011 and January 2019, generating 54.35% profit. Finally, our work showcased that mixtures of weighted classifiers perform better than any individual predictor of making trading decisions in the stock market.
Automatic skin lesion segmentation with fully convolutional-deconvolutional networks
Creators: name: Yuan, Yading
Publisher: name: arXiv
Year: 2017
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: This paper summarizes our method and validation results for the ISBI Challenge 2017 - Skin Lesion Analysis Towards Melanoma Detection - Part I: Lesion Segmentation
description: ISIC2017 challenge, 4 pages
On the algebra of symmetries of Laplace and Dirac operators
Creators: name: De Bie, Hendrik
name: Oste, Roy
name: Van der Jeugt, Joris
Publisher: name: arXiv
Year: 2017
Subjects: subject: Mathematical Physics (math-ph)
subject: Representation Theory (math.RT)
subject: FOS: Physical sciences
subject: FOS: Mathematics
subject: 81Q80, 81R10, 81R99, 47L90

description: We consider a generalization of the classical Laplace operator, which includes the Laplace-Dunkl operator defined in terms of the differential-difference operators associated with finite reflection groups called Dunkl operators. For this Laplace-like operator, we determine a set of symmetries commuting with it, which are generalized angular momentum operators, and we present the algebraic relations for the symmetry algebra. In this context, the generalized Dirac operator is then defined as a square root of our Laplace-like operator. We explicitly determine a family of graded operators which commute or anti-commute with our Dirac-like operator depending on their degree. The algebra generated by these symmetry operators is shown to be a generalization of the standard angular momentum algebra and the recently defined higher rank Bannai-Ito algebra.
description: 39 pages, final version
Optimal behavior of weighted Hardy operators on rearrangement-invariant spaces
Creators: name: Mihula, Zdeněk
Publisher: name: arXiv
Year: 2021
Subjects: subject: Functional Analysis (math.FA)
subject: FOS: Mathematics
subject: 46E30 (Primary) 47G10 (Secondary)

description: The behavior of certain weighted Hardy-type operators on rearrangement-invariant function spaces is thoroughly studied with emphasis being put on the optimality of the obtained results. First, the optimal rearrangement-invariant function spaces (that is, the best possible function spaces within the class of rearrangement-invariant function spaces) guaranteeing the boundedness of the operators from/to a given rearrangement-invariant function space are described. Second, the optimal rearrangement-invariant function norms being sometimes complicated, the question of whether and how they can be simplified to more manageable expressions, arguably more useful in practice, is addressed. Last, iterated weighted Hardy-type operators are also studied. Besides aiming to provide a comprehensive treatment of the optimal behavior of the operators on rearrangement-invariant function spaces in one place, the paper is motivated by its applicability in various fields of mathematical analysis, such as harmonic analysis, extrapolation theory or the theory of Sobolev-type spaces.
description: 44 pages
Strong solutions to SPDEs with monotone drift in divergence form
Creators: name: Marinelli, Carlo
name: Scarpa, Luca
Publisher: name: arXiv
Year: 2016
Subjects: subject: Analysis of PDEs (math.AP)
subject: Probability (math.PR)
subject: FOS: Mathematics

description: We prove existence and uniqueness of strong solutions, as well as continuous dependence on the initial datum, for a class of fully nonlinear second-order stochastic PDEs with drift in divergence form. Due to rather general assumptions on the growth of the nonlinearity in the drift, which, in particular, is allowed to grow faster than polynomially, existing techniques are not applicable. A well-posedness result is obtained through a combination of a priori estimates on regularized equations, interpreted both as stochastic equations as well as deterministic equations with random coefficients, and weak compactness arguments. The result is essentially sharp, in the sense that no extra hypotheses are needed, bar continuity of the nonlinear function in the drift, with respect to the deterministic theory.
description: 27 pages
Selecting the number of clusters, clustering models, and algorithms. A unifying approach based on the quadratic discriminant score
Creators: name: Coraggio, Luca
name: Coretto, Pietro
Publisher: name: arXiv
Year: 2021
Subjects: subject: Machine Learning (stat.ML)
subject: Machine Learning (cs.LG)
subject: FOS: Computer and information sciences

description: Cluster analysis requires many decisions: the clustering method and the implied reference model, the number of clusters and, often, several hyper-parameters and algorithms' tunings. In practice, one produces several partitions, and a final one is chosen based on validation or selection criteria. There exist an abundance of validation methods that, implicitly or explicitly, assume a certain clustering notion. Moreover, they are often restricted to operate on partitions obtained from a specific method. In this paper, we focus on groups that can be well separated by quadratic or linear boundaries. The reference cluster concept is defined through the quadratic discriminant score function and parameters describing clusters' size, center and scatter. We develop two cluster-quality criteria called quadratic scores. We show that these criteria are consistent with groups generated from a general class of elliptically-symmetric distributions. The quest for this type of groups is common in applications. The connection with likelihood theory for mixture models and model-based clustering is investigated. Based on bootstrap resampling of the quadratic scores, we propose a selection rule that allows choosing among many clustering solutions. The proposed method has the distinctive advantage that it can compare partitions that cannot be compared with other state-of-the-art methods. Extensive numerical experiments and the analysis of real data show that, even if some competing methods turn out to be superior in some setups, the proposed methodology achieves a better overall performance.
description: Supplemental materials are included at the end of the paper
Information scrambling at an impurity quantum critical point
Creators: name: Dóra, Balázs
name: Werner, Miklós Antal
name: Moca, Catalin Pascu
Publisher: name: arXiv
Year: 2017
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Quantum Gases (cond-mat.quant-gas)
subject: FOS: Physical sciences

description: The two-channel Kondo impurity model realizes a local non-Fermi liquid state with finite residual entropy. The competition between the two channels drives the system to an impurity quantum critical point. We show that the out-of-time-ordered (OTO) commutator for the impurity spin reveals markedly distinct behaviour depending on the low energy impurity state. For the one channel Kondo model with Fermi liquid ground state, the OTO commutator vanishes for late times, indicating the absence of the butterfly effect. For the two channel case, the impurity OTO commutator is completely temperature independent and saturates quickly to its upper bound 1/4, and the butterfly effect is maximally enhanced. These compare favourably to numerics on spin chain representation of the Kondo model. Our results imply that a large late time value of the OTO commutator does not necessarily diagnose quantum chaos.
description: 8 pages, 6 figures
The most metal-rich stars in the universe: chemical contributions of low and intermediate mass asymptotic giant branch stars with metallicities between $0.04 \leq Z \leq 0.10.$
Creators: name: Cinquegrana, Giulia C.
name: Karakas, Amanda I.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Low and intermediate mass stars with super solar metallicities comprise a known portion of the universe. Yet yields for asymptotic giant branch (AGB) stars with metallicities greater than $Z=0.04$ do not exist in the literature. This contributes a significant uncertainty to galactic chemical evolution simulations. We present stellar yields of AGB stars for $M=1-8$$M_\odot$ and $Z=0.04-0.10$. We also weight these yields to represent the chemical contribution of a metal-rich stellar population. We find that as metallicity increases, the efficiency of the mixing episodes (known as the third dredge up) on the thermally pulsing AGB (TP-AGB) decrease significantly. Consequently, much of the nucleosynthesis that occurs on the TP-AGB is not represented on the surface of very metal-rich stars. It instead remains locked inside the white dwarf remnant. The temperatures at the base of the convective envelope also decrease with increasing metallicity. For the intermediate mass models, this results in the occurrence of only partial hydrogen burning at this location, if any burning at all. We also investigate heavy element production via the slow neutron capture process (s-process) for three 6$M_\odot$ models: $Z=0.04, 0.05$ and $0.06$. There is minor production at the first s-process peak at strontium, which decreases sharply with increasing metallicity. We find the chemical contributions of our models are dominated by proton capture nucleosynthesis, mixed to the surface during first and second dredge up events. This conclusion is mirrored in our stellar population yields, weighted towards the lower mass regime to reflect the mass distribution within a respective galaxy.
Hyperspectral Image Classification with Markov Random Fields and a Convolutional Neural Network
Creators: name: Cao, Xiangyong
name: Zhou, Feng
name: Xu, Lin
name: Meng, Deyu
name: Xu, Zongben
name: Paisley, John
Publisher: name: arXiv
Year: 2017
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: This paper presents a new supervised classification algorithm for remotely sensed hyperspectral image (HSI) which integrates spectral and spatial information in a unified Bayesian framework. First, we formulate the HSI classification problem from a Bayesian perspective. Then, we adopt a convolutional neural network (CNN) to learn the posterior class distributions using a patch-wise training strategy to better use the spatial information. Next, spatial information is further considered by placing a spatial smoothness prior on the labels. Finally, we iteratively update the CNN parameters using stochastic gradient decent (SGD) and update the class labels of all pixel vectors using an alpha-expansion min-cut-based algorithm. Compared with other state-of-the-art methods, the proposed classification method achieves better performance on one synthetic dataset and two benchmark HSI datasets in a number of experimental settings.
Oracle Teacher: Leveraging Target Information for Better Knowledge Distillation of CTC Models
Creators: name: Yoon, Ji Won
name: Kim, Hyung Yong
name: Lee, Hyeonseung
name: Ahn, Sunghwan
name: Kim, Nam Soo
Publisher: name: arXiv
Year: 2021
Subjects: subject: Machine Learning (cs.LG)
subject: Audio and Speech Processing (eess.AS)
subject: Image and Video Processing (eess.IV)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: Knowledge distillation (KD), best known as an effective method for model compression, aims at transferring the knowledge of a bigger network (teacher) to a much smaller network (student). Conventional KD methods usually employ the teacher model trained in a supervised manner, where output labels are treated only as targets. Extending this supervised scheme further, we introduce a new type of teacher model for connectionist temporal classification (CTC)-based sequence models, namely Oracle Teacher, that leverages both the source inputs and the output labels as the teacher model's input. Since the Oracle Teacher learns a more accurate CTC alignment by referring to the target information, it can provide the student with more optimal guidance. One potential risk for the proposed approach is a trivial solution that the model's output directly copies the target input. Based on a many-to-one mapping property of the CTC algorithm, we present a training strategy that can effectively prevent the trivial solution and thus enables utilizing both source and target inputs for model training. Extensive experiments are conducted on two sequence learning tasks: speech recognition and scene text recognition. From the experimental results, we empirically show that the proposed model improves the students across these tasks while achieving a considerable speed-up in the teacher model's training time.
description: Accepted by IEEE/ACM Transactions on Audio, Speech and Language Processing
On a Stochastic Fundamental Lemma and Its Use for Data-Driven Optimal Control
Creators: name: Pan, Guanru
name: Ou, Ruchuan
name: Faulwasser, Timm
Publisher: name: arXiv
Year: 2021
Subjects: subject: Systems and Control (eess.SY)
subject: Optimization and Control (math.OC)
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Mathematics

description: Data-driven control based on the fundamental lemma by Willems et al. is frequently considered for deterministic LTI systems subject to measurement noise. However, besides measurement noise, stochastic disturbances might also directly affect the dynamics. In this paper, we leverage Polynomial Chaos Expansions (PCE) to extend the deterministic fundamental lemma towards stochastic systems. This extension allows to predict future statistical distributions of the inputs and outputs for stochastic LTI systems in data-driven fashion, i.e., based on the knowledge of previously recorded input-output-disturbance data and of the disturbance distribution we perform data-driven uncertainty propagation. Finally, we analyze data-driven stochastic optimal control problems and we propose a conceptual framework for data-driven stochastic predictive control. Numerical examples illustrate the efficacy of the proposed concepts.
A Novel Motion Detection Method Resistant to Severe Illumination Changes
Creators: name: Yousefi, Sahar
name: Shalmani, M. T. Manzuri
name: Lin, Jeremy
name: Staring, Marius
Publisher: name: arXiv
Year: 2016
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: Recently, there has been a considerable attention given to the motion detection problem due to the explosive growth of its applications in video analysis and surveillance systems. While the previous approaches can produce good results, an accurate detection of motion remains a challenging task due to the difficulties raised by illumination variations, occlusion, camouflage, burst physical motion, dynamic texture, and environmental changes such as those on climate changes, sunlight changes during a day, etc. In this paper, we propose a novel per-pixel motion descriptor for both motion detection and dynamic texture segmentation which outperforms the current methods in the literature particularly in severe scenarios. The proposed descriptor is based on two complementary three-dimensional-discrete wavelet transform (3D-DWT) and three-dimensional wavelet leader. In this approach, a feature vector is extracted for each pixel by applying a novel three dimensional wavelet-based motion descriptor. Then, the extracted features are clustered by a clustering method such as well-known k-means algorithm or Gaussian Mixture Model (GMM). The experimental results demonstrate the effectiveness of our proposed method compared to the other motion detection approaches from the literature. The application of the proposed method and additional experimental results for the different datasets are available at (http://dspl.ce.sharif.edu/motiondetector.html).
Floquet-engineering topological transitions in a twisted transition metal dichalcogenide homobilayer
Creators: name: Vogl, Michael
name: Rodriguez-Vega, Martin
name: Flebus, Benedetta
name: MacDonald, Allan H.
name: Fiete, Gregory A.
Publisher: name: The University of Texas at Austin
Year: 2021
Subjects: Floquet

description: Motivated by the recent experimental realization of twisted transition metal dichalcogenide bilay- ers, we study a simpliﬁed model driven by diﬀerent forms of monochromatic light. As a concrete and representative example we use parameters that correspond to a twisted MoTe2 homobilayer. First, we consider irradiation with circularly polarized light in free space and demonstrate that the corre- sponding Floquet Hamiltonian takes the same form as the static Hamiltonian, only with a constant overall shift in quasi-energy. This is in stark contrast to twisted bilayer graphene, where new terms are typically generated under an analagous drive. Longitudinal light, on the other hand, which can be generated from the transverse magnetic mode in a waveguide, has a much more dramatic eﬀect–it renormalizes the tunneling strength between the layers, which eﬀectively permits the tuning of the twist angle in-situ. We ﬁnd that, by varying the frequency and amplitude of the drive, one can induce a topological transition that cannot be obtained with the traditional form of the Floquet drive in free space. Furthermore, we ﬁnd that strong drives can have a profound eﬀect on the layer pseudo-spin texture of the twisted system, which coincides with multiple simultaneous band gap closings in the inﬁnite-frequency limit. Surprisingly, these bandgap closings are not associated with topological transitions. For high but ﬁnite drive frequencies near 0.7eV, the inﬁnite-frequency band crossings become band gap minima of the order of 10−6 eV or smaller.
New second-order optimality conditions in sub-Riemannian Geometry
Creators: name: Jóźwikowski, Michał
Publisher: name: arXiv
Year: 2022
Subjects: subject: Differential Geometry (math.DG)
subject: Optimization and Control (math.OC)
subject: FOS: Mathematics
subject: 53C17, 49K15

description: We study the geometry of the second-order expansion of the extended end-point map for the sub-Riemannian geodesic problem. Translating the geometric reality into equations we derive new second-order necessary optimality conditions in sub-Riemannian Geometry. In particular, we find an ODE for velocity of an abnormal sub-Riemannian geodesics. It allows to divide abnormal minimizers into two classes, which we propose to call 2-normal and 2-abnormal extremals. In the 2-normal case the above ODE completely determines the velocity of a curve, while in the 2-abnormal case the velocity is undetermined at some, or at all points. With some enhancement of the presented results it should be possible to prove the regularity of all 2-normal extremals (the 2-abnormal case seems to require study of higher-order conditions) thus making a step towards solving the problem of smoothness of sub-Riemannian abnormal geodesics. As a by-product we present a new derivation of Goh conditions. We also prove that the assumptions weaker than these used in [Boarotto, Monti, Palmurella, 2020] to derive third-order Goh conditions, imply piece-wise-$C^2$ regularity of an abnormal extremal.
description: Vastly improved presentation and proof, to appear in ESAIM Control Optim. Calc. Var
Simple Pricing Schemes for the Cloud
Creators: name: Kash, Ian A.
name: Key, Peter
name: Suksompong, Warut
Publisher: name: arXiv
Year: 2017
Subjects: subject: Computer Science and Game Theory (cs.GT)
subject: FOS: Computer and information sciences

description: The problem of pricing the cloud has attracted much recent attention due to the widespread use of cloud computing and cloud services. From a theoretical perspective, several mechanisms that provide strong efficiency or fairness guarantees and desirable incentive properties have been designed. However, these mechanisms often rely on a rigid model, with several parameters needing to be precisely known in order for the guarantees to hold. In this paper, we consider a stochastic model and show that it is possible to obtain good welfare and revenue guarantees with simple mechanisms that do not make use of the information on some of these parameters. In particular, we prove that a mechanism that sets the same price per time step for jobs of any length achieves at least 50% of the welfare and revenue obtained by a mechanism that can set different prices for jobs of different lengths, and the ratio can be improved if we have more specific knowledge of some parameters. Similarly, a mechanism that sets the same price for all servers even though the servers may receive different kinds of jobs can provide a reasonable welfare and revenue approximation compared to a mechanism that is allowed to set different prices for different servers.
description: To appear in the 13th Conference on Web and Internet Economics (WINE), 2017. A preliminary version was presented at the 12th Workshop on the Economics of Networks, Systems and Computation (NetEcon), 2017
Voltage-Controlled Magnetic Reversal in Orbital Chern Insulators
Creators: name: Zhu, Jihang
name: Su, Jung-Jung
name: MacDonald, Allan H.
Publisher: name: The University of Texas at Austin
Year: 2020
Subjects: chern

description: Chern insulator ferromagnets are characterized by a quantized anomalous Hall eﬀect (QAHE), and have so far been identiﬁed experimentally in magnetically-doped topological insulator (MTI) thin ﬁlms and in bilayer graphene moiré superlattices. We classify Chern insulator ferromagnets as either spin or orbital, depending on whether the orbital magnetization (OM) results from spontaneous spin-polarization combined with spin-orbit interactions, as in the MTI case, or directly from spontaneous orbital currents, as in the moiré superlattice case. We argue that in a given magnetic state, characterized for example by the sign of the anomalous Hall eﬀect (AHE), the magnetization of an orbital Chern insulator will often have opposite signs for weak 𝑛 and weak 𝑝 electrostatic or chemical doping. This property enables pure electrical switching of a magnetic state in the presence of a ﬁxed magnetic ﬁeld.
Floquet engineering of twisted double bilayer graphene
Creators: name: Rodriguez-Vega, Martin
name: Vogl, Michael
name: Fiete, Gegory A.
Publisher: name: American Physical Society
Year: 2020
Subjects: Floquet

description: Motivated by the recent experimental realization of twisted double bilayer graphene (TDBG) samples, we study, both analytically and numerically, the effects of circularly polarized light propagating in free space and conﬁned in a waveguide on the band structure and topological properties of these systems. These two complementary Floquet protocols allow us to selectively tune different parameters of the system by varying the intensity and light frequency. For the drive protocol in free space, in the high-frequency regime, we ﬁnd that in TDBG with AB/BA stacking, we can selectively close the zone-center quasienergy gaps around one valley while increasing the gaps near the opposite valley by tuning the parameters of the drive. In TDBG with AB/AB stacking, a similar effect can be obtained upon the application of a perpendicular static electric ﬁeld. Furthermore, we study the topological properties of the driven system in different settings, provide accurate effective Floquet Hamiltonians, and show that relatively strong drives can generate ﬂat bands. On the other hand, longitudinal light conﬁned in a waveguide couples to the components of the interlayer hopping that are perpendicular to the TDBG sheet, allowing for selective engineering of the bandwidth of Floquet zone-center quasienergy bands without breaking the symmetries of the static system.
MECHANISMS FOR DEVELOPING PRACTICAL COMPETENCES OF FUTURE MUSIC TEACHERS
Creators: name: Mo'minov, Elyor
Publisher: name: Zenodo
Year: 2025

description: This article analyzes the process of developing the practical competence of future music teachers from the point of view of scientific and theoretical foundations. Effective mechanisms for improving the performing, methodological and didactic skills of teachers in the music education system are highlighted, and the role of innovative technologies and interactive methods is revealed. The importance of practical training for music teachers, pedagogical approaches and modern educational methods that serve to improve their professional skills are also analyzed. The results of the study include recommendations aimed at improving the professional training of future music teachers.
Double spend races
Creators: name: Grunspan, Cyril
name: Pérez-Marco, Ricardo
Publisher: name: arXiv
Year: 2017
Subjects: subject: Cryptography and Security (cs.CR)
subject: Probability (math.PR)
subject: FOS: Computer and information sciences
subject: FOS: Mathematics
subject: 68M01, 60G40, 91A60, 33B20

description: We correct the double spend race analysis given in Nakamoto's foundational Bitcoin article and give a closed-form formula for the probability of success of a double spend attack using the Regularized Incomplete Beta Function. We give a proof of the exponential decay on the number of confirmations, often cited in the literature, and find an asymptotic formula. Larger number of confirmations are necessary compared to those given by Nakamoto. We also compute the probability conditional to the known validation time of the blocks. This provides a finer risk analysis than the classical one.
description: 35 pages, 5 figures, 7 tables. Final published version
A Large Dimensional Analysis of Least Squares Support Vector Machines
Creators: name: Liao, Zhenyu
name: Couillet, Romain
Publisher: name: arXiv
Year: 2017
Subjects: subject: Machine Learning (stat.ML)
subject: FOS: Computer and information sciences

description: In this article, a large dimensional performance analysis of kernel least squares support vector machines (LS-SVMs) is provided under the assumption of a two-class Gaussian mixture model for the input data. Building upon recent advances in random matrix theory, we show, when the dimension of data $p$ and their number $n$ are both large, that the LS-SVM decision function can be well approximated by a normally distributed random variable, the mean and variance of which depend explicitly on a local behavior of the kernel function. This theoretical result is then applied to the MNIST and Fashion-MNIST datasets which, despite their non-Gaussianity, exhibit a convincingly close behavior. Most importantly, our analysis provides a deeper understanding of the mechanism into play in SVM-type methods and in particular of the impact on the choice of the kernel function as well as some of their theoretical limits in separating high dimensional Gaussian vectors.
description: 14 pages, 13 figures, 1 table, partially presented at ICASSP 2017
Subgap two-particle spectral weight in disordered $s$-wave superconductors: Insights from mode coupling approach
Creators: name: Poduval, Prathyush P.
name: Samanta, Abhisek
name: Gupta, Prashant
name: Trivedi, Nandini
name: Sensarma, Rajdeep
Publisher: name: arXiv
Year: 2022
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We study the two-particle spectral functions and collective modes of weakly disordered superconductors using a disordered attractive Hubbard model on square lattice. We show that the disorder induced scattering between collective modes leads to a finite subgap spectral weight in the long wavelength limit. In general, the spectral weight is distributed between the phase and the Higgs channels, but as we move towards half-filling the Higgs contribution dominates. The inclusion of the density fluctuations lowers the frequency at which this mode occurs, and results in the phase channel gaining a larger contribution to this subgap mode. Near half-filling, the proximity of the system to the charge density wave (CDW) instability leads to strong fluctuations of the effective disorder at the commensurate wave-vector ($[π,π]$). We develop an analytical mode coupling approach where the pure Goldstone mode in the long wavelength limit couples to the collective mode at $[π,π]$. This provides insight into the location and distribution of the two-particle spectral weights between the Higgs and the phase channels.
Stable accretion from a cold disc in highly magnetized neutron stars
Creators: name: Tsygankov, S. S.
name: Mushtukov, A. A.
name: Suleimanov, V. F.
name: Doroshenko, V.
name: Abolmasov, P. K.
name: Lutovinov, A. A.
name: Poutanen, J.
Publisher: name: arXiv
Year: 2017
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: The aim of this paper is to investigate the transition of a strongly magnetized neutron star into the accretion regime with very low accretion rate. For this purpose we monitored the Be-transient X-ray pulsar GRO J1008-57 throughout a full orbital cycle. The current observational campaign was performed with the Swift/XRT telescope in the soft X-ray band (0.5-10 keV) between two subsequent Type I outbursts in January and September 2016. The expected transition to the propeller regime was not observed. However, the transitions between different regimes of accretion were detected. In particular, after an outburst the source entered a stable accretion state characterised by the accretion rate of ~10^14-10^15 g/s. We associate this state with accretion from a cold (low-ionised) disc of temperature below ~6500 K. We argue that a transition to such accretion regime should be observed in all X-ray pulsars with certain combination of the rotation frequency and magnetic field strength. The proposed model of accretion from a cold disc is able to explain several puzzling observational properties of X-ray pulsars.
description: 8 pages, 3 figures, 1 table, accepted by A&A
Die Computertomographie zur Detektion von Infektfoci bei hospitalisierten Patient:innen mit Sepsis: Status quo der klinischen Versorgung und Ansätze zur Optimierung
Creators: name: Pohlan, Julian
Publisher: name: Charité - Universitätsmedizin Berlin
Year: 2024
Subjects: subject: Sepsis
subject: Computed tomography
subject: 600 Technik, Medizin, angewandte Wissenschaften::610 Medizin und Gesundheit::610 Medizin und Gesundheit

description: In dieser Arbeit wurde die Rolle der Computertomographie (CT) zur Detektion von Infektquellen bei Patient:innen mit Sepsis untersucht. Die vorliegende Arbeit charakterisiert zunächst den aktuellen Stand der Diagnostik septischer Patient:innen mittels CT-Bildgebung. Die CT wird auf Basis der durchgeführten Untersuchungen als relevantes diagnostisches Verfahren zur Infektfokussuche bestätigt, das bspw. durch die Mikrobiologie komplementiert wird. Für unterschiedliche Settings wie die Rettungsstelle, die Normalstation und die Intensivstation konnte die wenige verfügbare Literatur ergänzt werden um Informationen zur Häufigkeitsverteilung bildgebend detektierter Infektfoci. Weiterhin konnte ermittelt werden, dass eine klinische und/oder auf Basis von Laborwerten generierte Einschätzung in allen untersuchten Settings nicht hinreichend prädiktiv für das Auftreten eines im CT detektierbaren Infektfokus ist. Es wurde festgestellt, dass sich in Abhängigkeit von der CT-Befundsicherheit vorhersagen lässt, ob die im CT registrierten Infektfoci den finale Foci, d.h. den im Arztbrief angegebenen Entlassdiagnosen, entsprechen. In einem relevanten Anteil der Patient:innen mit nachgewiesenem Infektfokus wurden zudem therapeutische Konsequenzen identifiziert, die sich auf die Diagnostik zurückführen ließen. In den Studien wurden die Morbidität und die Mortalität von Patient:innen mit Sepsis unter Berücksichtigung der CT-Bildgebung ausführlich untersucht und assoziierte Faktoren beschrieben. Um prognostisch relevante bildgebende Faktoren zu charakterisieren, untersuchten wir außerdem cerebrovaskuläre Ereignisse, die bei Patient:innen mit Sepsis gehäuft auftreten. Dabei konnten wir erstmalig die Prävalenz cerebrovaskulärer Ereignisse bei Sepsis beschreiben und die Relevanz für das Patient:innen-Outcome analysieren. Ein weiterer wichtiger Schritt in der vorliegenden Arbeit war die Untersuchung der Qualität der bildgebenden Diagnostik von Patient:innen der Intensivstation. Hierbei konnte der Nutzen des interdisziplinären Austauschs in MDCs mit strukturiertem Feedback gezeigt werden. So stellten wir eine Reduktion des Auftretens von QM-Ereignissen fest nach Einführung eines neuen, regelmäßigen und strukturierten Konferenzformats.
China’s social credit systems and public opinion: Explaining high levels of approval
Creators: name: Kostka, Genia
Publisher: name: Freie Universität Berlin
Year: 2019
Subjects: subject: China
subject: public opinion
subject: rating systems
subject: reputational systems
subject: social credit system
subject: social management
subject: 300 Social sciences::300 Social sciences, Sociology, Anthropology::304 Factors affecting social behavior
subject: 300 Social sciences::320 Political science::320 Political science

description: A variety of commercial and local government social credit systems (SCSs) are now being implemented in China in order to steer the behavior of Chinese individuals, businesses, social organizations, and government agencies. Previous research finds that these SCSs are employed by the Chinese state as “surveillance infrastructure” and for social management. This article focuses on a different angle: the public’s opinion of SCSs. Based on a cross-regional survey, the study finds a surprisingly high degree of approval of SCSs across respondent groups. Interestingly, more socially advantaged citizens (wealthier, better-educated, and urban residents) show the strongest approval of SCSs, along with older people. While one might expect such knowledgeable citizens to be most concerned about the privacy implications of SCS, they instead appear to embrace SCSs because they interpret it through frames of benefit-generation and promoting honest dealings in society and the economy instead of privacy-violation.
Informational Geodesics as the Origin of Field Geometry and Quantum Measurement Unified Theory of Higgs-Based Spacetime Emergence
Creators: name: Chatterjee, Dristi
Publisher: name: Zenodo
Year: 2025

description: This paper proposes a mathematically rigorous framework where the Higgs fieldgoverns mass, gravity, time, and space through coherent quantum dynamics. We con-struct a Theory of Everything grounded in three core principles: (1) the Higgs fieldconfers mass and mediates gravity through stabilization of its vacuum configuration;(2) time emerges as a rate of quantum basis change slowed by quantum Zeno dynam-ics; (3) space emerges as an entanglement network of Higgs field degrees of freedom,with geometry encoded by informational geodesics. We formalize the theory usingopen quantum systems, Lindblad master equations, Fisher information geometry, anda variational action principle unifying general relativity and quantum field theory. Wederive field equations linking the emergent metric to entanglement and decoherencerates, compute stress-energy tensors, simulate emergent curvature in a lattice model,assess compatibility with experimental constraints, and propose testable predictionswith realistic parameters and feasibility assessments.
COLOUR, LIPID AND PROTEIN OXIDATION IN BREAST AND THIGH MEAT OF BROILERS RAISED IN FOUR PRODUCTION SYSTEMS IN BELGIUM
Creators: name: Ali, Zeshan
name: Kowalski, Eline
name: De Smet, Stefaan
Publisher: name: Zenodo
Year: 2023

description: Worldwide, broilers are raised in different production systems from extensive to intensive, covering a range of genetics and management practices. Influence of the production system on the oxidative stability of meat has not been widely studied [1]. Oxidation of myoglobin, lipids and protein are major causes of quality deterioration in meat [2]. Differences in in vivo and postmortem muscle metabolism may affect the endogenous antioxidant defense system and the release of pro-oxidants and reactive oxygen species, resulting in potential differences in resistance against oxidation. The main objective of the present study was to compare oxidation in breast and thigh meat from broilers produced in four divergent production systems in Belgium.
Social Media, PSB, and the European Public Sphere: The informative role of social media platforms in improving European democracy.
Creators: name: Yilmaz, Kutlu Emre
Publisher: name: figshare
Year: 2023
Subjects: Sociology not elsewhere classified
Political science not elsewhere classified

description: MA Dissertation
 MA Media and Communications
 KUTLU EMRE YILMAZ
 Supervisor: Professor Petros Iosifidis
 City University London, September 2015
Unitary Design of Quantum Spin Networks for Robust Routing, Entanglement Generation, and Phase Sensing
Creators: name: Alsulami, Abdulsalam H.
name: D'Amico, Irene
name: Estarellas, Marta P.
name: Spiller, Timothy P.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Physics (quant-ph)
subject: Computational Physics (physics.comp-ph)
subject: FOS: Physical sciences

description: Spin chains can be used to describe a wide range of platforms for quantum computation and quantum information. They enable the understanding, demonstration, and modeling of numerous useful phenomena, such as high fidelity transfer of quantum states, creation and distribution of entanglement, and creation of resources for measurement-based quantum processing. In this paper, a more complex spin system, a 2D spin network (SN) engineered by applying suitable unitaries to two uncoupled spin chains, is studied. Considering only the single-excitation subspace of the SN, it is demonstrated that the system can be operated as a router, directing information through the SN. It is also shown that it can serve to generate maximally entangled states between two sites. Furthermore, it is illustrated that this SN system can be used as a sensor device able to determine an unknown phase applied to a system spin. A detailed modeling investigation of the effects of static disorder in the system shows that this system is robust against different types of disorder.
description: An erratum has been published for the journal paper. This updated arXiv version presents the corrected version of the published paper. The main conclusions of the paper are not affected by this correction