Top arXiv papers

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Toggle navigation SciRateSign inSign uparXiv.orgAstrophysicsEarth and Planetary AstrophysicsHigh Energy Astrophysical PhenomenaCosmology and Nongalactic AstrophysicsInstrumentation and Methods for AstrophysicsSolar and Stellar AstrophysicsAstrophysics of GalaxiesCondensed MatterStatistical MechanicsSoft Condensed MatterMaterials ScienceOther Condensed MatterStrongly Correlated ElectronsSuperconductivityQuantum GasesMesoscale and Nanoscale PhysicsDisordered Systems and Neural NetworksGeneral Relativity and Quantum CosmologyHEP - ExperimentHEP - LatticeHEP - PhenomenologyHEP - TheoryMathematical PhysicsNonlinear SciencesPattern Formation and SolitonsCellular Automata and Lattice GasesChaotic DynamicsExactly Solvable and Integrable SystemsAdaptation and Self-Organizing SystemsNuclear ExperimentNuclear TheoryMore PhysicsApplied PhysicsHistory and Philosophy of PhysicsGeneral PhysicsData Analysis, Statistics and ProbabilityOpticsMedical PhysicsGeophysicsPhysics and SocietyFluid DynamicsPopular PhysicsBiological PhysicsPlasma PhysicsClassical PhysicsAtomic PhysicsPhysics EducationInstrumentation and DetectorsChemical PhysicsComputational PhysicsAccelerator PhysicsSpace PhysicsAtomic and Molecular ClustersAtmospheric and Oceanic PhysicsQuantum PhysicsMathematicsAnalysis of PDEsStatistics TheoryNumber TheoryOperator AlgebrasSymplectic GeometryK-Theory and HomologyInformation TheoryCombinatoricsLogicAlgebraic GeometryRepresentation TheoryMathematical PhysicsComplex VariablesQuantum AlgebraNumerical AnalysisOptimization and ControlMetric GeometryGeometric TopologyDifferential GeometryDynamical SystemsGroup TheoryHistory and OverviewCategory TheoryAlgebraic TopologyClassical Analysis and ODEsGeneral TopologyFunctional AnalysisCommutative AlgebraSpectral TheoryProbabilityGeneral MathematicsRings and AlgebrasComputer ScienceComputational ComplexityInformation TheoryComputers and SocietyMachine LearningComputer Vision and Pattern RecognitionInformation RetrievalSoundSoftware EngineeringSocial and Information NetworksDatabasesNeural and Evolutionary ComputingMultiagent SystemsFormal Languages and Automata TheorySystems and ControlNumerical AnalysisHuman-Computer InteractionDistributed, Parallel, and Cluster ComputingHardware ArchitectureCryptography and SecurityArtificial IntelligenceComputer Science and Game TheoryProgramming LanguagesSymbolic ComputationComputational Engineering, Finance, and ScienceDiscrete MathematicsOther Computer ScienceComputation and LanguageNetworking and Internet ArchitectureEmerging TechnologiesGraphicsRoboticsPerformanceMultimediaGeneral LiteratureOperating SystemsDigital LibrariesLogic in Computer ScienceComputational GeometryData Structures and AlgorithmsMathematical SoftwareQuantitative BiologyNeurons and CognitionGenomicsBiomoleculesPopulations and EvolutionTissues and OrgansCell BehaviorQuantitative MethodsMolecular NetworksOther Quantitative BiologySubcellular ProcessesQuantitative FinanceEconomicsPricing of SecuritiesComputational FinancePortfolio ManagementRisk ManagementStatistical FinanceTrading and Market MicrostructureMathematical FinanceGeneral FinanceStatisticsStatistics TheoryMethodologyMachine LearningApplicationsComputationOther StatisticsEconomicsGeneral EconomicsEconometricsTheoretical EconomicsTop arXiv paperssign in to customizeGate Set TomographyErik Nielsen, John King Gamble, Kenneth Rudinger, Travis Scholten, Kevin Young, Robin Blume-Kohout Sep 17 2020 quant-ph arXiv:2009.07301v1 ScitedScite!9 Copy Citation PDFGate set tomography (GST) is a protocol for detailed, predictive characterization of logic operations (gates) on quantum computing processors. Early versions of GST emerged around 2012-13, and since then it has been refined, demonstrated, and used in a large number of experiments. This paper presents the foundations of GST in comprehensive detail. The most important feature of GST, compared to older state and process tomography protocols, is that it is calibration-free. GST does not rely on pre-calibrated state preparations and measurements. Instead, it characterizes all the operations in a gate set simultaneously and self-consistently, relative to each other. Long sequence GST can estimate gates with very high precision and efficiency, achieving Heisenberg scaling in regimes of practical interest. In this paper, we cover GST s intellectual history, the techniques and experiments used to achieve its intended purpose, data analysis, gauge freedom and fixing, error bars, and the interpretation of gauge-fixed estimates of gate sets. Our focus is fundamental mathematical aspects of GST, rather than implementation details, but we touch on some of the foundational algorithmic tricks used in the pyGSTi implementation.Extended flag gadgets for low-overhead circuit verificationDripto M. Debroy, Kenneth R. Brown Sep 17 2020 quant-ph arXiv:2009.07752v1 ScitedScite!8 Copy Citation PDFFlag verification techniques are useful in quantum error correction for detecting critical faults. Here we present an application of flag verification techniques to improving post-selected performance of near-term algorithms. We extend the definition of what constitutes a flag by creating error-detection gadgets based on known transformations of unitary operators. In the case of Clifford or near-Clifford circuits, these unitary operators can be chosen to be controlled Pauli gates, leading to gadgets which require only a small number of additional Clifford gates. We show that such flags can improve circuit fidelities by up to a factor of 2 after post selection, and demonstrate their effectiveness over error models featuring single-qubit depolarizing noise, crosstalk, and two-qubit coherent overrotation.On the Hardness of Detecting Macroscopic SuperpositionsScott Aaronson, Yosi Atia, Leonard Susskind Sep 17 2020 quant-ph gr-qc arXiv:2009.07450v1 ScitedScite!8 Copy Citation PDFWhen is decoherence effectively irreversible ? Here we examine this central question of quantum foundations using the tools of quantum computational complexity. We prove that, if one had a quantum circuit to determine if a system was in an equal superposition of two orthogonal states (for example, the $|$Alive$\rangle$ and $|$Dead$\rangle$ states of Schrödinger s cat), then with only a slightly larger circuit, one could also $\mathit{swap}$ the two states (e.g., bring a dead cat back to life). In other words, observing interference between the $|$Alive$\rangle$and $|$Dead$\rangle$ states is a necromancy-hard problem, technologically infeasible in any world where death is permanent. As for the converse statement (i.e., ability to swap implies ability to detect interference), we show that it holds modulo a single exception, involving unitaries that (for example) map $|$Alive$\rangle$ to $|$Dead$\rangle$ but $|$Dead$\rangle$ to -$|$Alive$\rangle$. We also show that these statements are robust---i.e., even a $\mathit{partial}$ ability to observe interference implies partial swapping ability, and vice versa. Finally, without relying on any unproved complexity conjectures, we show that all of these results are quantitatively tight. Our results have possible implications for the state dependence of observables in quantum gravity, the subject that originally motivated this study.Efficient Approximate Quantum State Tomography with Basis Dependent Neural-NetworksAlistair W. R. Smith, Johnnie Gray, M. S. Kim Sep 17 2020 quant-ph cs.LG arXiv:2009.07601v1 ScitedScite!3 Copy Citation PDFWe use a meta-learning neural-network approach to predict measurement outcomes of a quantum state in arbitrary local bases and thus carry out an approximate quantum state tomography. Each stage of this procedure can be performed efficiently, allowing it to be used effectively on large systems. We demonstrate this approach on the most recent noisy intermediate-scale IBM Quantum devices, achieving an accurate generative model for a 6-qubit state s measurement outcomes with only 100 random measurement settings as opposed to the 729 settings required for full tomography. This reduction in the required number of measurements scales favourably, with around 200 measurement settings yielding good results for a 10 qubit state that would require 59,049 settings for full quantum state tomography. This reduction in the number of measurement settings coupled with the efficiency of the procedure could allow for estimations of expectation values and state fidelities in practicable times on current quantum devices. For suitable states, this could then help in increasing the speed of other optimization schemes when attempting to produce states on noisy quantum devices at a scale where traditional maximum likelihood based approaches are impractical.Quantum teleportation of a spin-mapped Majorana zero mode qubitHe-Liang Huang, Marek Narozniak, Futian Liang, Youwei Zhao, Anthony D.Castellano, Ming Gong, Yulin Wu, Jin Lin, Yu Xu, Hui Deng, Hao Rong, Jonathan P. Dowling, Cheng-Zhi Peng, Tim Byrnes, Xiaobo Zhu, Jian-Wei Pan Sep 17 2020 quant-ph arXiv:2009.07590v1 ScitedScite!2 Copy Citation PDFQuantum error correction is widely considered to be an essential ingredient for overcoming decoherence and achieving large-scale quantum computation. Topological quantum computation based on anyons is a promising approach to achieve fault-tolerant quantum computing. The Majorana zero modes in the Kitaev chain are an example of non-Abelian anyons where braiding operations can be used to perform quantum gates. Here we demonstrate in a superconducting quantum processor that the spin-mapped version of the Majorana zero modes can be used to perform quantum teleportation. The teleportation transfers the quantum state encoded on two-qubit Majorana zero mode states between two Kitaev chains, using only braiding operations. The Majorana encoding is a quantum-error-detecting code for phase flip errors, which is used to improve the average fidelity of the teleportation for six distinct states from $70.76 \pm 0.35 \% $ to $84.60 \pm 0.11 \%$, well beyond the classical bound in either case.Typical and Extremal Aspects of Friends-and-Strangers GraphsNoga Alon, Colin Defant, Noah Kravitz Sep 17 2020 math.CO cs.DM arXiv:2009.07840v1 ScitedScite!1 Copy Citation PDFGiven graphs $X$ and $Y$ with vertex sets $V(X)$ and $V(Y)$ of the same cardinality, the friends-and-strangers graph $\mathsf{FS}(X,Y)$ is the graph whose vertex set consists of all bijections $\sigma:V(X)\to V(Y)$, where two bijections $\sigma$ and $\sigma $ are adjacent if they agree everywhere except for two adjacent vertices $a,b \in V(X)$ such that $\sigma(a)$ and $\sigma(b)$ are adjacent in $Y$. The most fundamental question that one can ask about these friends-and-strangers graphs is whether or not they are connected; we address this problem from two different perspectives. First, we address the case of typical $X$ and $Y$ by proving that if $X$ and $Y$ are independent Erdős-Rényi random graphs with $n$ vertices and edge probability $p$, then the threshold probability guaranteeing the connectedness of $\mathsf{FS}(X,Y)$ with high probability is $p=n^{-1/2+o(1)}$. Second, we address the case of extremal $X$ and $Y$ by proving that the smallest minimum degree of the $n$-vertex graphs $X$ and $Y$ that guarantees the connectedness of $\mathsf{FS}(X,Y)$ is between $3n/5+O(1)$ and $9n/14+O(1)$. When $X$ and $Y$ are bipartite, a parity obstruction forces $\mathsf{FS}(X,Y)$ to be disconnected. In this bipartite setting, we prove analogous typical and extremal results concerning when $\mathsf{FS}(X,Y)$ has exactly $2$ connected components; for the extremal question, we obtain a nearly exact result.The controlled SWAP test for determining quantum entanglementSteph Foulds, Viv Kendon, Tim Spiller Sep 17 2020 quant-ph arXiv:2009.07613v1 ScitedScite!1 Copy Citation PDFQuantum entanglement is essential to the development of quantum computation, communications and technology. The controlled SWAP test, widely used for state comparison, can be adapted to an efficient and general test for entanglement of a pure state. Here we show that the test can evidence the presence of entanglement (and further, genuine $n$-qubit entanglement), can distinguish entanglement classes, and generates the concurrence in the case of a 2-qubit state. We also propose a multipartite degree of entanglement, related to the test s probability outputs. The average number of measurements required to detect entanglement increases with decreased entanglement. Maximally entangled states require fewer measurements the larger the system, two on average for eight or more qubits. Furthermore, the results are robust to second order when typical small errors are introduced to the state under investigation.Landscape of Sparse Linear Network: A Brief InvestigationDachao Lin, Ruoyu Sun, Zhihua Zhang Sep 17 2020 cs.LG stat.ML arXiv:2009.07439v1 ScitedScite!1 Copy Citation PDFNetwork pruning, or sparse network has a long history and practical significance in modern application. A major concern for neural network training is that the non-convexity of the associated loss functions may cause bad landscape. We focus on analyzing sparse linear network generated from weight pruning strategy. With no unrealistic assumption, we prove the following statements for the squared loss objective of sparse linear neural networks: 1) every local minimum is a global minimum for scalar output with any sparse structure, or non-intersect sparse first layer and dense other layers with whitened data; 2) sparse linear networks have sub-optimal local-min for only sparse first layer or three target dimensions.How to unloop a sticky tapeTwan J.S. Wilting, Martin H. Essink, Hanneke Gelderblom, Jacco H. Snoeijer Sep 17 2020 cond-mat.soft arXiv:2009.07323v1 ScitedScite!1 Copy Citation PDFBy folding two adhesive sides of a tape together a loop is formed, which one expects to unloop by pulling on its free ends. Surprisingly, the loop does not immediately open up but shrinks in size, held together by a tenuous contact region that propagates along the tape. This adhesive contact region only ruptures once the loop is reduced to a critical size. We experimentally show that the shrinkage of the loop results from an interaction between the peeling front and the loop across the contact zone, accompanied by a highly nonlinear increase of the peeling force. Loop opening only occurs once the curvatures on both sides of the contact zone are equal. The interactions across the contact zone call for a description beyond the classical elastica theory. We propose a mechanical model that captures the experimental observations such as the scaling law for the critical loop size. Our results reveal and quantify the increased force required to remove loops in self-adherent media, which is of importance in applications ranging from blister removal to exfoliation of graphene sheets.Space-efficient binary optimization for variational computingAdam Glos, Aleksandra Krawiec, Zoltán Zimborás Sep 17 2020 quant-ph cond-mat.stat-mech arXiv:2009.07309v1 ScitedScite!1 Copy Citation PDFIn the era of Noisy Intermediate-Scale Quantum (NISQ) computers it is crucial to design quantum algorithms which do not require many qubits or deep circuits. Unfortunately, the most well-known quantum algorithms are too demanding to be run on currently available quantum devices. Moreover, even the state-of-the-art algorithms developed for the NISQ era often suffer from high space complexity requirements for particular problem classes. In this paper, we show that it is possible to greatly reduce the number of qubits needed for the Traveling Salesman Problem (TSP), a paradigmatic optimization task, at the cost of having deeper variational circuits. While the focus is on this particular problem, we claim that the approach can be generalized for other problems where the standard bit-encoding is highly inefficient. Finally, we also propose encoding schemes which smoothly interpolate between the qubit-efficient and the circuit depth-efficient models. All the proposed encodings remain efficient to implement within the Quantum Approximate Optimization Algorithm framework.Continuous measurements for control of superconducting quantum circuitsShay Hacohen-Gourgy, Leigh S. Martin Sep 17 2020 quant-ph arXiv:2009.07297v1 ScitedScite!1 Copy Citation PDFDevelopments over the last two decades have opened the path towards quantum technologies in many quantum systems, such as cold atoms, trapped ions, cavity-quantum electrodynamics (QED), and circuit-QED. However the fragility of quantum states to the effects of measurement and decoherence still poses one of the greatest challenges in quantum technology. An imperative capability in this path is quantum feedback, as it enhances the control possibilities and allows for prolonging coherence times through quantum error correction. While changing parameters from shot to shot of an experiment or procedure can be considered feedback, quantum mechanics also allows for the intriguing possibility of performing feedback operations during the measurement process itself. This broader approach to measurements leads to the concepts of weak measurement, quantum trajectories and numerous types of feedback with no classical analogues. These types of processes are the primary focus of this review. We introduce the concept of quantum feedback in the context of circuit QED, an experimental platform with significant potential in quantum feedback and technology. We then discuss several experiments and see how they elucidate the concepts of continuous measurements and feedback. We conclude with an overview of coherent feedback, with application to fault-tolerant error correction.Lower Bounds for Policy Iteration on Multi-action MDPsKumar Ashutosh, Sarthak Consul, Bhishma Dedhia, Parthasarathi Khirwadkar, Sahil Shah, Shivaram Kalyanakrishnan Sep 17 2020 cs.LG stat.ML arXiv:2009.07842v1 ScitedScite!0 Copy Citation PDFPolicy Iteration (PI) is a classical family of algorithms to compute an optimal policy for any given Markov Decision Problem (MDP). The basic idea in PI is to begin with some initial policy and to repeatedly update the policy to one from an improving set, until an optimal policy is reached. Different variants of PI result from the (switching) rule used for improvement. An important theoretical question is how many iterations a specified PI variant will take to terminate as a function of the number of states $n$ and the number of actions $k$ in the input MDP. While there has been considerable progress towards upper-bounding this number, there are fewer results on lower bounds. In particular, existing lower bounds primarily focus on the special case of $k = 2$ actions. We devise lower bounds for $k \geq 3$. Our main result is that a particular variant of PI can take $\Omega(k^{n/2})$ iterations to terminate. We also generalise existing constructions on $2$-action MDPs to scale lower bounds by a factor of $k$ for some common deterministic variants of PI, and by $\log(k)$ for corresponding randomised variants.Event-plane decorrelation of photons produced in the early stage of heavy-ion collisionsCharles Gale, Jean-François Paquet, Björn Schenke, Chun Shen Sep 17 2020 nucl-th arXiv:2009.07841v1 ScitedScite!0 Copy Citation PDFWe study photon production in the early stage of heavy-ion collisions using a multistage model combining IP-Glasma, KøMPøST and relativistic hydrodynamics. We discuss the small momentum anisotropy of these photons, highlighting the role of the photon-hadron event-plane decorrelation. We comment that this singular characteristic of early photons could be used to provide dynamical information on the complex pre-hydrodynamics phase of heavy-ion collisions.Text Generation by Learning from Off-Policy DemonstrationsRichard Yuanzhe Pang, He He Sep 17 2020 cs.CL cs.LG arXiv:2009.07839v1 ScitedScite!0 Copy Citation PDFCurrent approaches to text generation largely rely on autoregressive models and maximum likelihood estimation. This paradigm leads to (i) diverse but low-quality samples due to mismatched learning objective and evaluation metric (likelihood vs. quality) and (ii) exposure bias due to mismatched history distributions (gold vs. model-generated). To alleviate these problems, we frame text generation as a reinforcement learning (RL) problem with expert demonstrations (i.e., the training data), where the goal is to maximize quality given model-generated histories. Prior RL approaches to generation often face optimization issues due to the large action space and sparse reward. We propose GOLD (generation by off-policy learning from demonstrations): an algorithm that learns from the off-policy demonstrations by importance weighting and does not suffer from degenerative solutions. We find that GOLD outperforms the baselines according to automatic and human evaluation on summarization, question generation, and machine translation, including attaining state-of-the-art results for CNN/DailyMail summarization. Further, we show that models trained by GOLD are less sensitive to decoding algorithms and the generation quality does not degrade much as the length increases.FairFace Challenge at ECCV 2020: Analyzing Bias in Face RecognitionTomáš Sixta, Julio C. S. Jacques Junior, Pau Buch-Cardona, Eduard Vazquez, Sergio Escalera Sep 17 2020 cs.CV arXiv:2009.07838v1 ScitedScite!0 Copy Citation PDFThis work summarizes the 2020 ChaLearn Looking at People Fair Face Recognition and Analysis Challenge and provides a description of the top-winning solutions and analysis of the results. The aim of the challenge was to evaluate accuracy and bias in gender and skin colour of submitted algorithms on the task of 1:1 face verification in the presence of other confounding attributes. Participants were evaluated using an in-the-wild dataset based on reannotated IJB-C, further enriched by 12.5K new images and additional labels. The dataset is not balanced, which simulates a real world scenario where AI-based models supposed to present fair outcomes are trained and evaluated on imbalanced data. The challenge attracted 151 participants, who made more than 1.8K submissions in total. The final phase of the challenge attracted 36 active teams out of which 10 exceeded 0.999 AUC-ROC while achieving very low scores in the proposed bias metrics. Common strategies by the participants were face pre-processing, homogenization of data distributions, the use of bias aware loss functions and ensemble models. The analysis of top-10 teams shows higher false positive rates (and lower false negative rates) for females with dark skin tone as well as the potential of eyeglasses and young age to increase the false positive rates too.Transport, destruction and growth of pebbles in the gas envelope of a protoplanetAnders Johansen, Åke Nordlund Sep 17 2020 astro-ph.EP arXiv:2009.07837v1 ScitedScite!0 Copy Citation PDFWe analyse the size evolution of pebbles accreted into the gaseous envelope of a protoplanet growing in a protoplanetary disc, taking into account collisions driven by the relative sedimentation speed as well as the convective gas motion. Using a simple estimate of the convective gas speed based on the pebble accretion luminosity, we find that the speed of the convective gas is higher than the sedimentation speed for all particles smaller than 1 mm. This implies that both pebbles and pebble fragments are strongly affected by the convective gas motion and will be transported by large-scale convection cells both towards and away from the protoplanet s surface. We present a simple scheme for evolving the characteristic size of the pebbles, taking into account the effects of erosion, mass transfer and fragmentation. Including the downwards motion of convective cells for the transport of pebbles with an initial radius of 1 millimeter, we find pebble sizes between 100 microns and 1 millimeter near the surface of the protoplanet. These sizes are generally amenable to accretion at the base of the convection flow. Small protoplanets far from the star ( 30 AU) nevertheless erode their pebbles to sizes below 10 microns; future hydrodynamical simulations will be needed to determine whether such small fragments can detach from the convection flow and become accreted by the protoplanet.Induced superconductivity in the fractional quantum Hall edgeÖnder Gül, Yuval Ronen, Si Young Lee, Hassan Shapourian, Jonathan Zauberman, Young Hee Lee, Kenji Watanabe, Takashi Taniguchi, Ashvin Vishwanath, Amir Yacoby, Philip Kim Sep 17 2020 cond-mat.mes-hall arXiv:2009.07836v1 ScitedScite!0 Copy Citation PDFTopological superconductors represent a phase of matter with nonlocal properties which cannot smoothly change from one phase to another, providing a robustness suitable for quantum computing. Substantial progress has been made towards a qubit based on Majorana modes, non-Abelian anyons of Ising ($Z_2$) topological order whose exchange$-$braiding$-$produces topologically protected logic operations. However, because braiding Ising anyons does not offer a universal quantum gate set, Majorana qubits are computationally limited. This drawback can be overcome by introducing parafermions, a novel generalized set of non-Abelian modes ($Z_n$), an array of which supports universal topological quantum computation. The primary route to synthesize parafermions involves inducing superconductivity in the fractional quantum Hall (fqH) edge. Here we use high-quality graphene-based van der Waals devices with narrow superconducting niobium nitride (NbN) electrodes, in which superconductivity and robust fqH coexist. We find crossed Andreev reflection (CAR) across the superconductor separating two counterpropagating fqH edges which demonstrates their superconducting pairing. Our observed CAR probability of the integer edges is insensitive to magnetic field, temperature, and filling, which provides evidence for spin-orbit coupling inherited from NbN enabling the pairing of the otherwise spin-polarized edges. FqH edges notably exhibit a CAR probability higher than that of integer edges once fully developed. This fqH CAR probability remains nonzero down to our lowest accessible temperature, suggesting superconducting pairing of fractional charges. These results provide a route to realize novel topological superconducting phases with universal braiding statistics in fqH-superconductor hybrid devices based on graphene and NbN.On The Biomass Required To Produce Phosphine Detected In The Cloud Decks Of VenusManasvi Lingam, Abraham Loeb Sep 17 2020 astro-ph.EP astro-ph.IM arXiv:2009.07835v1 ScitedScite!0 Copy Citation PDFThe putative detection of phosphine in the atmosphere of Venus at an abundance of $\sim 20$ ppb suggests that this gas is being generated by either indeterminate abiotic pathways or biological processes. We consider the latter possibility, and explore whether the amount of biomass required to produce the observed flux of phosphine may be reasonable. We find that the typical biomass densities predicted by our simple model are several orders of magnitude lower than the average biomass density of Earth s aerial biosphere. We briefly discuss how small spacecraft could sample the Venusian cloud decks and search for biomarkers. On account of certain weakly constrained variables as well as the heuristic nature of our model, the results presented herein should be viewed with due caution.Immutable Log Storage as a Service on Private and Public BlockchainsWilliam Pourmajidi, Lei Zhang, John Steinbacher, Tony Erwin, Andriy Miranskyy Sep 17 2020 cs.SE cs.CR cs.DC arXiv:2009.07834v1 ScitedScite!0 Copy Citation PDFDuring the normal operation of a Cloud solution, no one pays attention to the logs except the system reliability engineers, who may periodically check them to ensure that the Cloud platform s performance conforms to the Service Level Agreements (SLA). However, the moment a component fails, or a customer complains about a breach of SLA, the importance of logs increases significantly. All departments, including management, customer support, and even the actual customer, may turn to logs to determine the cause and timeline of the issue and to find the party responsible for the issue. The party at fault may be motivated to tamper with the logs to hide their role. Given the number and volume of logs generated by the Cloud platforms, many tampering opportunities exist. We argue that the critical nature of logs calls for immutability and verification mechanism without the presence of a single trusted party. This paper proposes such a mechanism by describing a blockchain-based log system, called Logchain, which can be integrated with existing private and public blockchain solutions. Logchain uses the immutability feature of blockchain to provide a tamper-resistance storage platform for log storage. Additionally, we propose a hierarchical structure to combine the hash-binding of two blockchains to address blockchains scalability issues. To validate the mechanism, we integrate Logchain into two different types of blockchains. We choose Ethereum as a public, permission-less blockchain and IBM Blockchain as a private, permission-based one. We show that the solution is scalable on both the private and public blockchains. Additionally, we perform the analysis of the cost of ownership for private and public blockchains implementations to help a reader selecting an implementation that would be applicable to their needs.Layered Neural Rendering for Retiming People in VideoErika Lu, Forrester Cole, Tali Dekel, Weidi Xie, Andrew Zisserman, David Salesin, William T. Freeman, Michael Rubinstein Sep 17 2020 cs.CV cs.GR arXiv:2009.07833v1 ScitedScite!0 Copy Citation PDFWe present a method for retiming people in an ordinary, natural video---manipulating and editing the time in which different motions of individuals in the video occur. We can temporally align different motions, change the speed of certain actions (speeding up/slowing down, or entirely freezing people), or erase selected people from the video altogether. We achieve these effects computationally via a dedicated learning-based layered video representation, where each frame in the video is decomposed into separate RGBA layers, representing the appearance of different people in the video. A key property of our model is that it not only disentangles the direct motions of each person in the input video, but also correlates each person automatically with the scene changes they generate---e.g., shadows, reflections, and motion of loose clothing. The layers can be individually retimed and recombined into a new video, allowing us to achieve realistic, high-quality renderings of retiming effects for real-world videos depicting complex actions and involving multiple individuals, including dancing, trampoline jumping, or group running.Did NANOGrav see a signal from primordial black hole formation?Ville Vaskonen, Hardi Veermäe Sep 17 2020 astro-ph.CO arXiv:2009.07832v1 ScitedScite!0 Copy Citation PDFWe show that the recent NANOGrav result can be interpreted as a stochastic gravitational wave signal associated to formation of primordial black holes from high-amplitude curvature perturbations. The indicated amplitude and power of the gravitational wave spectrum agrees well with formation of primordial seeds for supermassive black holes.On $G$-crossed Frobenius $\star$-algebras and fusion rings associated with braided $G$-actionsPrashant Arote, Tanmay Deshpande Sep 17 2020 math.QA arXiv:2009.07831v1 ScitedScite!0 Copy Citation PDFFor a finite group $G$, Turaev introduced the notion of a braided $G$-crossed fusion category. The classification of braided $G$-crossed extensions of braided fusion categories was studied by Etingof, Nikshych and Ostrik in terms of certain group cohomological data. In this paper we will define the notion of a $G$-crossed Frobenius $\star$-algebra and give a classification of (strict) $G$-crossed extensions of a commutative Frobenius $\star$-algebra $R$ equipped with a given action of $G$, in terms of the second group cohomology $H^2(G,R^\times)$. Now suppose that $\mathcal{B}$ is a non-degenerate braided fusion category equipped with a braided action of a finite group $G$. We will see that the associated $G$-graded fusion ring is in fact a (strict) $G$-crossed Frobenius $\star$-algebra. We will describe this $G$-crossed fusion ring in terms of the classification of braided $G$-actions by Etingof, Nikshych, Ostrik and derive a Verlinde formula to compute its fusion coefficients.On a generalization of one Kramer s theoremViachaslau I. Murashka Sep 17 2020 math.GR arXiv:2009.07830v1 ScitedScite!0 Copy Citation PDFYangming Li and Xianhua Li in 2012 proposed a conjecture that generalizes O.U. Kramer s result about supersoluble groups. Here we proved that this conjecture is false in the general case and true for groups with the trivial Frattini subgroup.Integrable systems and the boundary dynamics of higher spin gravity on AdS$_3$Emilio Ojeda, Alfredo Pérez Sep 17 2020 hep-th gr-qc arXiv:2009.07829v1 ScitedScite!0 Copy Citation PDFWe introduce a new set of boundary conditions for three-dimensional higher spin gravity with gauge group $SL(3,\mathbb{R})\times SL(3,\mathbb{R})$, where its dynamics at the boundary is described by the members of the modified Boussinesq integrable hierarchy. In the asymptotic region the gauge fields are written in the diagonal gauge, where the excitations go along the generators of the Cartan subalgebra of $sl(3,\mathbb{R})\oplus sl(3,\mathbb{R})$. We show that the entire integrable structure of the modified Boussinesq hierarchy, i.e., the phase space, the Poisson brackets and the infinite number of commuting conserved charges, are obtained from the asymptotic structure of the higher spin theory. Furthermore, its known relation with the Boussinesq hierarchy is inherited from our analysis once the asymptotic conditions are re-expressed in the highest weight gauge. Hence, the Miura map is recovered from a purely geometric construction in the bulk. Black holes that fit within our boundary conditions, the Hamiltonian reduction at the boundary, and the generalization to higher spin gravity with gauge group $SL(N,\mathbb{R})\times SL(N,\mathbb{R})$ are also discussed.Human biases in body measurement estimationKirill Martynov, Kiran Garimella, Robert West Sep 17 2020 cs.SI cs.HC arXiv:2009.07828v1 ScitedScite!0 Copy Citation PDFBody measurements, including weight and height, are key indicators of health. Being able to visually assess body measurements reliably is a step towards increased awareness of overweight and obesity and is thus important for public health. Nevertheless it is currently not well understood how accurately humans can assess weight and height from images, and when and how they fail. To bridge this gap, we start from 1,682 images of persons collected from the Web, each annotated with the true weight and height, and ask crowd workers to estimate the weight and height for each image. We conduct a faceted analysis taking into account characteristics of the images as well as the crowd workers assessing the images, revealing several novel findings: (1) Even after aggregation, the crowd s accuracy is overall low. (2) We find strong evidence of contraction bias toward a reference value, such that the weight (height) of light (short) people is overestimated, whereas that of heavy (tall) people is underestimated. (3) We estimate workers individual reference values using a Bayesian model, finding that reference values strongly correlate with workers own height and weight, indicating that workers are better at estimating people similar to themselves. (4) The weight of tall people is underestimated more than that of short people; yet, knowing the height decreases the weight error only mildly. (5) Accuracy is higher on images of females than of males, but female and male workers are no different in terms of accuracy. (6) Crowd workers improve over time if given feedback on previous guesses. Finally, we explore various bias correction models for improving the crowd s accuracy, but find that this only leads to modest gains. Overall, this work provides important insights on biases in body measurement estimation as obesity related conditions are on the rise.Multiple Exemplars-based Hallucinationfor Face Super-resolution and EditingKaili Wang, Jose Oramas, Tinne Tuytelaars Sep 17 2020 cs.CV arXiv:2009.07827v1 ScitedScite!0 Copy Citation PDFGiven a really low-resolution input image of a face (say 16x16 or 8x8 pixels), the goal of this paper is to reconstruct a high-resolution version thereof. This, by itself, is an ill-posed problem, as the high-frequency information is missing in the low-resolution input and needs to be hallucinated, based on prior knowledge about the image content. Rather than relying on a generic face prior, in this paper, we explore the use of a set of exemplars, i.e. other high-resolution images of the same person. These guide the neural network as we condition the output on them. Multiple exemplars work better than a single one. To combine the information from multiple exemplars effectively, we intro-duce a pixel-wise weight generation module. Besides standard face super-resolution, our method allows to perform subtle face editing simply by replacing the exemplars with another set with different facial features. A user study is conducted and shows the super-resolved images can hardly be distinguished from real images on the CelebA dataset. A qualitative comparison indicates our model outperforms methods proposed in the literature on the CelebA and WebFace daAlumina coating for dispersion management in ultra-high Q microresonatorsMarvyn Inga, Laís Fujii, José Maria C. da Silva Filho, João Henrique Q. Palhares, Andre S. Ferlauto, Francisco C. Marques, Thiago P. Mayer Alegre, Gustavo S. Wiederhecker Sep 17 2020 physics.optics arXiv:2009.07826v1 ScitedScite!0 Copy Citation PDFSilica optical microspheres often exhibit ultra-high quality factors, yet, their group velocity dispersion, which is crucial for nonlinear optics applications, can only be coarsely tuned. We experimentally demonstrate that group-velocity dispersion of a silica microsphere can be engineered by coating it with conformal nanometric layers of alumina, yet preserving its ultra-high optical quality factors (\num∼e7) at telecom wavelengths. Using the atomic layer deposition technique for the dielectric coating, which ensures nm-level thickness control, we not only achieve a fine dispersion tailoring but also maintain a low surface roughness and material absorption to ensure a low optical loss. Numerical simulations supporting our experimental results show that the alumina layer thickness is a promising technique for precise tuning of group-velocity dispersion. As an application we demonstrate the generation of Kerr optical frequency combs, showing that the alumina coatings can also sustain the high optical intensities necessary for nonlinear optical phenomena.Multiport Rapid Charging Power ConverterYikun Chen, Ahmad Elkhateb Sep 17 2020 eess.SY cs.SY arXiv:2009.07825v1 ScitedScite!0 Copy Citation PDFRapid charger is getting more and more important as the electric vehicle (EV) getting popular. The rapid charging technique plays an important part in the electric vehicle development. Multiport converter is used in the rapid charging technique to reduce the required current and also provides some other advantages. In this paper, the literature review form multiport converter to the rapid charger of electric vehicle is introduced. Some topologies of multiport converter are discussed in the literature review. Triple active bridge topology (TAB) is selected as it is useful and commonly used. The feasibility of using Sinusoidal Pulse Width Modulation (SPWM) to control the converter is also discussed in the simulation part. A simple hardware design and experiment is included at the end.ArielRad: the Ariel Radiometric ModelLorenzo V. Mugnai, Enzo Pascale, Billy Edwards, Andreas Papageorgiou, Subhajit Sarkar Sep 17 2020 astro-ph.IM astro-ph.EP astro-ph.SR arXiv:2009.07824v1 ScitedScite!0 Copy Citation PDFArielRad, the Ariel radiometric model, is a simulator developed to address the challenges in optimising the space mission science payload and to demonstrate its compliance with the performance requirements. Ariel, the Atmospheric Remote-Sensing Infrared Exoplanet Large-survey, has been selected by ESA as the M4 mission in the Cosmic Vision programme and, during its 4 years primary operation, will provide the first unbiased spectroscopic survey of a large and diverse sample of transiting exoplanet atmospheres. To allow for an accurate study of the mission, ArielRad uses a physically motivated noise model to estimate contributions arising from stationary processes, and includes margins for correlated and time-dependent noise sources. We show that the measurement uncertainties are dominated by the photon statistic,and that an observing programme with about 1000 exoplanetary targets can be completed during the primary mission lifetime.GOCor: Bringing Globally Optimized Correspondence Volumes into Your Neural NetworkPrune Truong, Martin Danelljan, Luc Van Gool, Radu Timofte Sep 17 2020 cs.CV arXiv:2009.07823v1 ScitedScite!0 Copy Citation PDFThe feature correlation layer serves as a key neural network module in numerous computer vision problems that involve dense correspondences between image pairs. It predicts a correspondence volume by evaluating dense scalar products between feature vectors extracted from pairs of locations in two images. However, this point-to-point feature comparison is insufficient when disambiguating multiple similar regions in an image, severely affecting the performance of the end task. We propose GOCor, a fully differentiable dense matching module, acting as a direct replacement to the feature correlation layer. The correspondence volume generated by our module is the result of an internal optimization procedure that explicitly accounts for similar regions in the scene. Moreover, our approach is capable of effectively learning spatial matching priors to resolve further matching ambiguities. We analyze our GOCor module in extensive ablative experiments. When integrated into state-of-the-art networks, our approach significantly outperforms the feature correlation layer for the tasks of geometric matching, optical flow, and dense semantic matching. The code and trained models will be made available at github.com/PruneTruong/GOCor.Ultra Buck DC/DC Converter for Electric VehiclesLuoqi Chen, Ahmad Elkhateb, Nikolaos Athanasopoulos Sep 17 2020 eess.SY cs.SY arXiv:2009.07822v1 ScitedScite!0 Copy Citation PDFA critical challenge in power conversion in electric vehicles is the efficient use of DC-DC buck converters that need to provide 12-V supply for load systems from 400/800-V batteries. This paper presents a literature review on the development of DC-DC buck converters. Moreover, one novel four-phase interleaved step-down topology is selected for simulation and hardware experiments. Based on the four-phase interleaved structure, an extended-phase topology is proposed, which has a higher voltage conversion ratio. Control techniques are also applied to it. Theoretical analyses and simulation results are provided to verify the improved converter. A 400V-to-12V and 150W output power hardware prototype is implemented to verify its performanceBiHom-Akivis algebrasSylvain Attan Sep 17 2020 math.RA arXiv:2009.07821v1 ScitedScite!0 Copy Citation PDFBiHom-Akivis algebras are introduced. The BiHom-commutator-BiHom-associator algebra of a regular BiHom-algebra is a BiHom-Akivis algebra. It is shown that BiHom-Akivis algebras can be obtained from Akivis algebras by twisting along two algebra endomorphisms. It is pointed out that a BiHom-Akivis algebra associated to a regular BiHom-alternative algebra is a BiHom-Malcev algebra.The Interplay between Ambipolar Diffusion and Hall Effect on Magnetic Field Decoupling and Protostellar Disc FormationBo Zhao, Paola Caselli, Zhi-Yun Li, Ruben Krasnopolsky, Hsien Shang, Ka Ho Lam Sep 17 2020 astro-ph.SR astro-ph.EP astro-ph.GA arXiv:2009.07820v1 ScitedScite!0 Copy Citation PDFNon-ideal MHD effects have been shown recently as a robust mechanism of averting the magnetic braking catastrophe and promoting protostellar disc formation. However, the magnetic diffusivities that determine the efficiency of non-ideal MHD effects are highly sensitive to microphysics. We carry out non-ideal MHD simulations to explore the role of microphysics on disc formation and the interplay between ambipolar diffusion (AD) and Hall effect during the protostellar collapse. We find that removing the smallest grain population ($\lesssim$10 nm) from the standard MRN size distribution is sufficient for enabling disc formation. Further varying the grain sizes can result in either a Hall-dominated or an AD-dominated collapse; both form discs of tens of AU in size regardless of the magnetic field polarity. The direction of disc rotation is bimodal in the Hall dominated collapse but unimodal in the AD-dominated collapse. We also find that AD and Hall effect can operate either with or against each other in both radial and azimuthal directions, yet the combined effect of AD and Hall is to move the magnetic field radially outward relative to the infalling envelope matter. In addition, microphysics and magnetic field polarity can leave profound imprints both on observables (e.g., outflow morphology, disc to stellar mass ratio) and on the magnetic field characteristics of protoplanetary discs. Including Hall effect relaxes the requirements on microphysics for disc formation, so that prestellar cores with cosmic-ray ionization rate of $\lesssim$2--3$\times10^{-16}$ s$^{-1}$ can still form small discs of $\lesssim$10 AU radius. We conclude that disc formation should be relatively common for typical prestellar core conditions, and that microphysics in the protostellar envelope is essential to not only disc formation, but also protoplanetary disc evolution.Improved Neural Network Monte Carlo SimulationI-Kai Chen, Matthew D. Klimek, Maxim Perelstein Sep 17 2020 hep-ph hep-ex physics.comp-ph stat.ML arXiv:2009.07819v1 ScitedScite!0 Copy Citation PDFThe algorithm for Monte Carlo simulation of parton-level events based on an Artificial Neural Network (ANN) proposed in arXiv:1810.11509 is used to perform a simulation of $H\to 4\ell$ decay. Improvements in the training algorithm have been implemented to avoid numerical instabilities. The integrated decay width evaluated by the ANN is within 0.7% of the true value and unweighting efficiency of 26% is reached. While the ANN is not automatically bijective between input and output spaces, which can lead to issues with simulation quality, we argue that the training procedure naturally prefers bijective maps, and demonstrate that the trained ANN is bijective to a very good approximation.Trajectory planning with a dynamic obstacle clustering strategy using Mixed-Integer Linear ProgrammingVinicius Antonio Battagello, Nei Yoshihiro Soma, Rubens Junqueira Magalhaes Afonso Sep 17 2020 eess.SY cs.SY arXiv:2009.07818v1 ScitedScite!0 Copy Citation PDFIn this paper we propose a technique that assigns obstacles to clusters used for collision avoidance via Mixed-Integer Programming. This strategy enables a reduction in the number of binary variables used for collision avoidance, thus entailing a decrease in computational cost, which has been a hindrance to the application of Model Predictive Control approaches with Mixed-Integer Programming formulations in real-time. Moreover, the assignment of obstacles to clusters and the sizes of the clusters are decided within the same optimization problem that performs the trajectory planning, thus yielding optimal cluster choices. Simulation results are presented to illustrate an application of the proposal.Scalar resonance in graviton-graviton scattering at high-energies: the graviballD. Blas, J. Martin Camalich, J.A. Oller Sep 17 2020 hep-th gr-qc hep-ph arXiv:2009.07817v1 ScitedScite!0 Copy Citation PDFWe study graviton-graviton scattering in partial-wave amplitudes after unitarizing their Born terms. In order to apply S-matrix techniques, based on unitarity and analyticity, we introduce an S-matrix free of infrared divergences. This is achieved by removing a diverging phase factor related to the infinite-range character of the interactions mediated by graviton exchange in the crossed channels. A scalar graviton-graviton resonance with vacuum quantum numbers (J^PC=0^++) is obtained as a pole in the nonperturbative S-wave amplitude, which we call the \it graviball. Its resonant effects along the physical real s axis may peak at values much lower than the UV cutoff of the theory. For some scenarios, this phenomenon could have phenomenological consequences at relatively low-energy scales.A Human-Computer Duet System for Music PerformanceYuen-Jen Lin, Hsuan-Kai Kao, Yih-Chih Tseng, Ming Tsai, Li Su Sep 17 2020 cs.MM cs.AI arXiv:2009.07816v1 ScitedScite!0 Copy Citation PDFVirtual musicians have become a remarkable phenomenon in the contemporary multimedia arts. However, most of the virtual musicians nowadays have not been endowed with abilities to create their own behaviors, or to perform music with human musicians. In this paper, we firstly create a virtual violinist, who can collaborate with a human pianist to perform chamber music automatically without any intervention. The system incorporates the techniques from various fields, including real-time music tracking, pose estimation, and body movement generation. In our system, the virtual musician s behavior is generated based on the given music audio alone, and such a system results in a low-cost, efficient and scalable way to produce human and virtual musicians co-performance. The proposed system has been validated in public concerts. Objective quality assessment approaches and possible ways to systematically improve the system are also discussed.Beyond the Western Core-Periphery Model: Analysing Scientific Mobility and Collaboration in the Middle East and North AfricaJamal El Ouahi, Nicolas Robinson-Garcia, Rodrigo Costas Sep 17 2020 cs.DL arXiv:2009.07815v1 ScitedScite!0 Copy Citation PDFThis study investigates the scientific mobility and international collaboration networks in the Middle East and North Africa (MENA) region between 2008 and 2017. The main goal is to establish mobility and collaboration profiles at the region and country levels. By using affiliation metadata available in scientific publications, we track international scientific mobility and collaboration networks in the region. Three complementary approaches allow us to obtain a detailed characterization of scientific mobility. First, we study the mobility flows for each country to uncover the main destinations and origins of mobile scholars. Results reveal geographical, cultural, historical, and linguistic proximities. Cooperation and exchange programs also contribute to explain some of the observed flows. Second, we introduce mobile scientists academic age. The average academic age of migrant scholars in MENA between 2008 and 2017 was about 12.4 years. For most countries, immigrants are relatively younger than emigrants, except for Iran, Palestine, Lebanon, and Turkey. Scholars who migrated to Gulf Cooperation Council (GCC) countries, Jordan and Morocco were in average younger than emigrants by 1.5 year from the same countries. The academic age group 6-to-10 years is the most common for both emigrant and immigrant scholars. Third, we analyse gender differences of scholars. We observe a clear gender gap in terms of scientific mobility: Male scholars represent the largest group of migrants in MENA countries. We conclude discussing the policy relevance of the scientific mobility and collaboration aspects and discuss limitations and further research.Framework for analysis of next generation, polarised CMB data sets in the presence of galactic foregrounds and systematic effectsClara Vergès, Josquin Errard, Radek Stompor Sep 17 2020 astro-ph.CO arXiv:2009.07814v1 ScitedScite!0 Copy Citation PDFReaching the sufficient sensitivity to detect primordial B-modes requires modern CMB polarisation experiments to rely on new technologies, necessary for the deployment of arrays thousands of detectors with a broad frequency coverage and operating them for extended periods of time. This increased complexity of experimental design unavoidably introduces new instrumental and systematic effects, which may impact performance of the new instruments. In this work we extend the standard data analysis pipeline by including a (parametric) model of instrumental effects directly in the data model. We then correct for them in the analysis, accounting for the additional uncertainty in the final results. We embed these techniques within a general, end-to-end formalism for estimating the impact of the instrument and foreground models on constraints on the amplitude of the primordial B-mode signal. We focus on the parametric component separation approach which we generalize to allow for simultaneous estimation of instrumental and foreground parameters. We demonstrate the framework by studying the effects induced by an achromatic half-wave plate (HWP), which lead to a frequency-dependent variation of the instrument polarisation angle, and experimental bandpasses which define observational frequency bands. We assume a typical Stage-3 CMB polarisation experiment, and show that maps recovered from raw data collected at each frequency band will unavoidably be linear mixtures of the Q and U Stokes parameters. We then derive a new generalized data model appropriate for such cases, and extend the component separation approach to account for it. We find that some of the instrumental parameters, in particularly those describing the HWP can be successfully constrained by the data themselves without need for external information, while others, like bandpasses, need to be known with good precision in advance.Dark Matter Simulations with Primordial Black Holes in the Early UniverseMaxim Tkachev, Sergey Pilipenko, Gustavo Yepes Sep 17 2020 astro-ph.CO gr-qc hep-ph arXiv:2009.07813v1 ScitedScite!0 Copy Citation PDFPrimordial Black Holes (PBH) with masses of order $10-30 M_\odot$ have been proposed as a possible explanation of the gravitational waves emission events recently discovered by the LIGO observatory. If true, then PBHs would constitute a sizeable fraction of the dark matter component in the Universe. Using a series of cosmological N-body simulations which include both dark matter and a variable fraction of PBHs ranging from $f_{PBH} = 10^{-4}$ to $f_{PBH} = 1$, we analyse the processes of formation and disruption of gravitationally bound PBH pairs, as well as the merging of both bound and unbound pairs, and estimate the probabilities of such events. We show that they are in good agreement with the constrains to the PBH abundance obtained by the LIGO and other research groups. We find that pair stability, while being a main factor responsible for the merger rate, is significantly affected by the effects of dark matter halo formation and clustering. As a side result, we also evaluate the effects of numerical errors in the stability of bound pairs, which can be useful for future research using this methodology.Ramified optimal transportation with payoff on the boundaryQinglan Xia, Shaofeng Xu Sep 17 2020 math.OC math.AP arXiv:2009.07812v1 ScitedScite!0 Copy Citation PDFThis paper studies a variant of ramified/branched optimal transportation problems. Given the distributions of production capacities and market sizes, a firm looks for an allocation of productions over factories, a distribution of sales across markets, and a transport path that delivers the product to maximize its profit. Mathematically, given any two measures $\mu$ and $\nu$ on $X$, and a payoff function $h$, the planner wants to minimize $\mathbf{M}_{\alpha }(T)-\int_{X}hd(\partial T)$ among all transport paths $T$ from $\tilde{\mu}$ to $\tilde{\nu}$ with $\tilde{\mu}\preceq \mu $ and $\tilde{\nu}\preceq \nu $, where $\mathbf{M}_{\alpha }$ is the standard cost functional used in ramified transportation. After proving the existence result, we provide a characterization of the boundary measures of the optimal solution. They turn out to be the original measures restricted on some Borel subsets up to a Delta mass on each connected component. Our analysis further finds that as the boundary payoff increases, the corresponding solution of the current problem converges to an optimal transport path, which is the solution of the standard ramified transportation.Probabilistic Value-Deviation-Bounded Source-Dependent Bit-Level Channel Adaptation for Approximate CommunicationBilgesu Arif Bilgin, Phillip Stanley-Marbell Sep 17 2020 eess.SP arXiv:2009.07811v1 ScitedScite!0 Copy Citation PDFComputing systems that can tolerate effects of errors in their communicated data values can trade this tolerance for improved resource efficiency. Many important applications of computing, such as embedded sensor systems, can tolerate errors that are bounded in their distribution of deviation from correctness (distortion). We present a channel adaptation technique which modulates properties of I/O channels typical in embedded sensor systems, to provide a tradeoff between I/O power dissipation and distortion of communicated data. We provide an efficient-to-compute formulation for the distribution of integer distortion accounting for the distribution of transmitted values. Using this formulation we implement our value-deviation-bounded (VDB) channel adaptation. We experimentally quantify the achieved reduction in power dissipation on a hardware prototype integrated with the required programmable channel modulation circuitry. We augment these experimental measurements with an analysis of the distributions of distortions. We show that our probabilistic VDB channel adaptation can provide up to a 2$\times$ reduction in I/O power dissipation. When synthesized for a miniature low-power FPGA intended for use in sensor interfaces, a register transfer level implementation of the channel adaptation control logic requires only 106 flip-flops and 224 4-input LUTs for implementing per-bit channel adaptation on serialized streams of 8-bit sensor data.CoDEx: A Comprehensive Knowledge Graph Completion BenchmarkTara Safavi, Danai Koutra Sep 17 2020 cs.CL cs.AI cs.IR cs.LG arXiv:2009.07810v1 ScitedScite!0 Copy Citation PDFWe present CoDEx, a set of knowledge graph Completion Datasets Extracted from Wikidata and Wikipedia that improve upon existing knowledge graph completion benchmarks in scope and level of difficulty. In terms of scope, CoDEx comprises three knowledge graphs varying in size and structure, multilingual descriptions of entities and relations, and tens of thousands of hard negative triples that are plausible but verified to be false. To characterize CoDEx, we contribute thorough empirical analyses and benchmarking experiments. First, we analyze each CoDEx dataset in terms of logical relation patterns. Next, we report baseline link prediction and triple classification results on CoDEx for five extensively tuned embedding models. Finally, we differentiate CoDEx from a popular link prediction benchmark by showing that CoDEx covers more diverse and interpretable content, and contains fewer relation patterns that can be covered by trivial frequency-based rules. Data, code, and pretrained models are available at https://github.com/tsafavi/codex.Predictions for the Angular Dependence of Gas Mass Flow Rate and Metallicity in the Circumgalactic MediumCeline Peroux, Dylan Nelson, Freeke van de Voort, Annalisa Pillepich, Federico Marinacci, Mark Vogelsberger, Lars Hernquist Sep 17 2020 astro-ph.GA arXiv:2009.07809v1 ScitedScite!0 Copy Citation PDFWe use cosmological hydrodynamical simulations to examine the physical properties of the gas in the circumgalactic media (CGM) of star-forming galaxies as a function of angular orientation. We utilise TNG50 of the IllustrisTNG project, as well as the EAGLE simulation to show that observable properties of CGM gas correlate with azimuthal angle, defined as the galiocentric angle with respect to the central galaxy. Both simulations are in remarkable agreement in predicting a strong modulation of flow rate direction with azimuthal angle: inflow is more substantial along the galaxy major axis, while outflow is strongest along the minor axis. The absolute rates are noticeably larger for higher (log(M_* / M_sun) ~ 10.5) stellar mass galaxies, up to an order of magnitude compared to M^dot 1 M_sun/yr/sr for log(M_* / M_sun) ~ 9.5 objects. Notwithstanding the different numerical and physical models, both TNG50 and EAGLE predict that the average metallicity of the CGM is higher along the minor versus major axes of galaxies. The angular signal is robust across a wide range of galaxy stellar mass 8.5 log(M_* / M_sun) 10.5 at z 1. This azimuthal dependence is particularly clear at larger impact parameters b 100 kpc. Our results present a global picture whereby, despite the numerous mixing processes, there is a clear angular dependence of the CGM metallicity. We make forecasts for future large survey programs that will be able to compare against these expectations. Indeed, characterising the kinematics, spatial distribution and metal content of CGM gas is key to a full understanding of the exchange of mass, metals, and energy between galaxies and their surrounding environments.Spin-Crossover From a Well-Behaved, Low-Cost meta-GGA Density FunctionalDaniel Mejia-Rodriguez, S.B. Trickey Sep 17 2020 physics.chem-ph arXiv:2009.07808v1 ScitedScite!0 Copy Citation PDFThe recent major modification, r$^2$SCAN, of the SCAN (strongly constrained and appropriately normed) meta-GGA exchange-correlation functional is shown to give substantially better spin-crossover electronic energies (high spin minus low spin) on a benchmark data set than the original SCAN. The deorbitalized counterpart r$^2$SCAN-L is almost as good as SCAN and much faster in periodically bounded systems. A combination strategy for balanced treatment of molecular and periodic spin-crossover therefore is recommended.Explicit coverings of families of elliptic surfaces by squares of curvesColin Ingalls, Adam Logan, Owen Patashnick Sep 17 2020 math.AG math.NT arXiv:2009.07807v1 ScitedScite!0 Copy Citation PDFWe show that, for each $n 0$, there is a family of elliptic surfaces which are covered by the square of a curve of genus $2n+1$, and whose Hodge structures have an action by ${\mathbb Q}(\sqrt{-n})$. By considering the case $n=3$, we show that one particular family of K3 surfaces are covered by the square of genus $7$. Using this, we construct a correspondence between the square of a curve of genus $7$ and a general K3 surface in ${\mathbb P}^4$ with $15$ ordinary double points up to isogeny. This gives an explicit proof of the Kuga-Satake-Deligne correspondence for these K3 surfaces and any K3 surfaces isogenous to them, and further, a proof of the Hodge conjecture for the squares of these surfaces. We conclude that the motives of these surfaces are Kimura-finite. Our analysis gives a birational equivalence between a moduli space of curves with additional data and the moduli space of these K3 surfaces with a specific elliptic fibration.Transformer Based Multi-Source Domain AdaptationDustin Wright, Isabelle Augenstein Sep 17 2020 cs.LG cs.CL stat.ML arXiv:2009.07806v1 ScitedScite!0 Copy Citation PDFIn practical machine learning settings, the data on which a model must make predictions often come from a different distribution than the data it was trained on. Here, we investigate the problem of unsupervised multi-source domain adaptation, where a model is trained on labelled data from multiple source domains and must make predictions on a domain for which no labelled data has been seen. Prior work with CNNs and RNNs has demonstrated the benefit of mixture of experts, where the predictions of multiple domain expert classifiers are combined; as well as domain adversarial training, to induce a domain agnostic representation space. Inspired by this, we investigate how such methods can be effectively applied to large pretrained transformer models. We find that domain adversarial training has an effect on the learned representations of these models while having little effect on their performance, suggesting that large transformer-based models are already relatively robust across domains. Additionally, we show that mixture of experts leads to significant performance improvements by comparing several variants of mixing functions, including one novel mixture based on attention. Finally, we demonstrate that the predictions of large pretrained transformer based domain experts are highly homogenous, making it challenging to learn effective functions for mixing their predictions.An Intrinsic Treatment of Stochastic Linear RegressionYu-Lin Chou Sep 17 2020 math.ST stat.TH arXiv:2009.07805v1 ScitedScite!0 Copy Citation PDFLinear regression is perhaps one of the most popular statistical concepts, which permeates almost every scientific field of study. Due to the technical simplicity and wide applicability of linear regression, attention is almost always quickly directed to the algorithmic or computational side of linear regression. In particular, the underlying mathematics of stochastic linear regression itself as an entity usually gets either a peripheral treatment or a relatively in-depth but ad hoc treatment depending on the type of concerned problems; in other words, compared to the extensiveness of the study of mathematical properties of the derivatives of stochastic linear regression such as the least squares estimator, the mathematics of stochastic linear regression itself seems to have not yet received a due intrinsic treatment. Apart from the conceptual importance, a consequence of an insufficient or possibly inaccurate understanding of stochastic linear regression would be the recurrence for the role of stochastic linear regression in the important (and more sophisticated) context of structural equation modeling to be misperceived or taught in a misleading way. We believe this pity is rectifiable when the fundamental concepts are correctly classified. Accompanied by some illustrative, distinguishing examples and counterexamples, we intend to pave out the mathematical framework for stochastic linear regression, in a rigorous but non-technical way, by giving new results and pasting together several fundamental known results that are, we believe, both enlightening and conceptually useful, and that had not yet been systematically documented in the related literature. As a minor contribution, the way we arrange the fundamental known results would be the first attempt in the related literature.Extending CSR Decomposition to Tropical Inhomogeneous Matrix ProductsArthur Kennedy-Cochran-Patrick, Sergei Sergeev Sep 17 2020 math.CO math.RA arXiv:2009.07804v1 ScitedScite!0 Copy Citation PDFThis article presents an attempt to extend the CSR decomposition, previously introduced for tropical matrix powers, to tropical inhomogeneous matrix products. The CSR terms for inhomogeneous matrix products are introduced, then a case is described where an inhomogeneous product admits such CSR decomposition after some length and give a bound on this length. In the last part of the paper a number of counterexamples are presented to show that inhomogeneous products do not admit CSR decomposition under more general conditions.Pentagon Functions for Scattering of Five Massless ParticlesDmitry Chicherin, Vasily Sotnikov Sep 17 2020 hep-ph hep-th arXiv:2009.07803v1 ScitedScite!0 Copy Citation PDFWe complete the analytic calculation of the full set of two-loop Feynman integrals required for computation of massless five-particle scattering amplitudes. We employ the method of canonical differential equations to construct a minimal basis set of transcendental functions, pentagon functions, which is sufficient to express all planar and nonplanar massless five-point two-loop Feynman integrals in the whole physical phase space. We find analytic expressions for pentagon functions which are manifestly free of unphysical branch cuts. We present a public library for numerical evaluation of pentagon functions suitable for immediate phenomenological applications. Previous 1 2 3 4 5 6 7 8 9 10 11 12 Next Date PublishedThu 17 Sep 2020UTCPrev dayNext day1d3d1w1m1yRecent commentsForecasting timelines of quantum computingC. Jess Riedel Sep 15 2020 19:25 UTCThanks!Forecasting timelines of quantum computingWeilei Zeng Sep 15 2020 17:40 UTCThey actually work by copying and pasting, but the embedded URLs leads to the wrong places.Forecasting timelines of quantum computingWeilei Zeng Sep 15 2020 17:37 UTCInteresting result. Just as a feedback, the two google links on Page 4 are not available.Fiber Bundle Codes: Breaking the $N^{1/2} \operatorname{polylog}(N)$ Barr...Anthony Leverrier Sep 10 2020 13:23 UTCAh yes! Thanks for the explanation. Fiber Bundle Codes: Breaking the $N^{1/2} \operatorname{polylog}(N)$ Barr...Matt Hastings Sep 10 2020 12:58 UTCGlad you like it! I must admit, we also thought it was N^{5/8} for a while. But, I think N^{3/5} is indeed what follows from balancing. Though, if we miss something, please let us know so we can get that extra 0.025 power in the exponent.Ignoring polylogs, one has distances N^{1/2} and N^{3/4 ...(continued)Fiber Bundle Codes: Breaking the $N^{1/2} \operatorname{polylog}(N)$ Barr...Anthony Leverrier Sep 10 2020 11:55 UTCAmazing! Unless I'm missing something, the distance should even be $N^{5/8}$ instead of $N^{3/5}$, unless the balancing trick (or the final weight reduction) causes the expected distance to decrease.Quantum coherence as a signature of chaosNamit Anand Sep 10 2020 05:30 UTCYes, please do post it here if you find something interesting -- you're also welcome to just send me an email! Also, thanks for pointing to its role as a biodiversity measure -- I never would have found that (in fact, they use the entire family of Rényi entropies).Quantum coherence as a signature of chaosBlake Stacey Sep 10 2020 03:09 UTCThanks for the reply!The first time I encountered a quantity of the form $\sum_i p(i)^2$ was in the context of Rényi entropy, and then as a [biodiversity measure](https://www.maths.ed.ac.uk/~tl/mdiss.pdf), so it defintely does appear under many names! I'll look around for earlier references conn ...(continued)Quantum coherence as a signature of chaosNamit Anand Sep 08 2020 18:05 UTCHi Blake, thanks for the comment. In fact, the connection between $l_2$-norm of coherence and participation ratio was already used in a previous paper by a subset of the authors: https://arxiv.org/abs/1906.09242; see Appendix C (where it is implicitly used). But for some reason, we had forgotten to ...(continued)Quantum coherence as a signature of chaosBlake Stacey Sep 08 2020 17:28 UTCIn Eq. (5), the authors state that given a pure state and a basis, the second moment of the probabilities for that state measured in that basis is equal to 1 minus the [$l_2$-norm of coherence](https://arxiv.org/abs/1311.0275), and they say that "To the best of our knowledge", they make that connect ...(continued) Blog About Code of Conduct Legal

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