cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
The effect of vanadium substitution on the structural and magnetic properties of (Fe$_{1-x}$V$_{x}$)$_{3}$Ga$_{4}$
Creators: name: Wilfong, Brandon
name: Sharma, Vaibhav
name: Bishop, Omar
name: Fedorko, Adrian
name: Heiman, Don
name: Barua, Radhika
name: Jamer, Michelle E.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Fe$_{3}$Ga$_{4}$ displays a complex magnetic phase diagram that is sensitive and tunable with both electronic and crystallographic structure changes. In order to explore this tunability, vanadium-doped (Fe$_{1-x}$V$_{x}$)$_{3}$Ga$_{4}$ has been synthesized and characterized. High-resolution synchrotron X-ray diffraction and Rietveld refinement show that samples up to 20\% V-doping remain isostructural to Fe$_{3}$Ga$_{4}$ and display a linear increase in unit cell volume as doping is increased. Magnetic measurements reveal a suppression of the antiferromagnetic helical spin-density wave (SDW) with V-doping, revealed by changes in both the low-temperature ferromagnetic-antiferromagentic (FM-AFM) transition (T$_{1}$) and high-temperature AFM-FM transition (T$_{2}$). At 7.5\% V-doping, the metamagnetic behavior of the helical AFM SDW phase is no longer observed. These results offer an avenue to effective tuning of the magnetic order in Fe$_{3}$Ga$_{4}$ for devices, as well as increased understanding of the magnetism in this system.
A polymer-tethered particle confined in a slit
Creators: name: Staszewski, T.
name: Borówko, M.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: Shape transformations of hairy nanoparticles under confinement are studied using molecular dynamic simulations. We discuss the behavior of these particles in slits with inert or attractive walls. We assume that only chain-wall interactions are attractive. The impact of the strength of interactions with the walls and the width of the slits on the particle configuration is shown. In the case of attractive surfaces, we found new structures in which the chains are connected with both walls and form bridges between them: pillars, symmetrical and asymmetrical spools, and hourglasses. In wide pores with strongly attractive walls, hairy particles adsorb on one of the surfaces and form "mounds" or starfish-like strucures.
description: 11 pages, 7 figures
Transport of solid particles in deterministic lateral displacement systems
Creators: name: Du, Siqi
Publisher: name: No Publisher Supplied
Year: 2018

description: Deterministic Lateral Displacement (DLD) exploits the experimental observation that in microfluidics, particles of different sizes forced through a periodic array of cylindrical posts may migrate in different directions thus leading to separation. In this dissertation, we propose various modifications on DLD systems and discuss the potential of using one of the more radically modified DLD systems to filter particulate matter air pollution. We first propose a flow-driven DLD system with a rotating circle at the center of the obstacle array. This model system can be easily reconfigured to establish an arbitrary orientation between the average flow field and the array of obstacles comprising the stationary phase (forcing angle). We show that this reconfigurable design preserves the size separation functionality of traditional DLD device and hugely improves the reusability of DLD devices. We then extend the length of the posts in the obstacle array and construct a 3D-DLD setup which allows the particle to move not only in-plane (in the basal plane of the obstacle array) but also out-of-plane (along the direction of the posts). We show that the (projected) in-plane motion of the particles is completely analogous to that observed in 2D-DLD systems. More importantly, we observe significant differences in the out-of-plane displacement depending on particle size for certain orientations of the driving force. Therefore, taking advantage of both the in-plane and out-of-plane motion of the particles, it is possible to achieve the simultaneous fractionation of a polydisperse suspension into multiple streams. Last, we present a radical departure from traditional system and use an array of anchored liquid-bridges as the stationary phase in the DLD device. We show that the non-linear particle dynamics observed in traditional DLD systems is also present in the anchored-liquid case, enabling analogous size-based separation of suspended particles. Interestingly, preliminary experiments show that the proposed liquid DLD system can function excellently well as a particulate matter air filtration device when subjected to a cross directional particle-laden flow. In particular, we uncover the deciding factors, namely particle incoming offset and Stokes number, related to particle capture efficiency and lay out future plans to further the exploration in the domain of air filtration using arrays of anchored liquid bridges.
Gefängnis und die Folgen: Indentitätsentwicklung und Kriminelles Handeln während und nach Verbüßung einer Jugendstrafe.
Das Erhebungsinstrument der standardisierten Befragung JuSt-Bericht Nr. 3
Creators: name: Hosser, Daniela
name: Greve, Werner
Publisher: name: Universität Tübingen
Year: 1999
Subjects: subject: Jugendstrafe
subject: 360

description: Zweitveröffentlichung. Download von https://kfn.de/publikationen/kfn-forschungsberichte
Chaotic cold accretion on to black holes in rotating atmospheres
Creators: name: Gaspari, M.
name: Brighenti, F.
name: Temi, P.
Publisher: name: arXiv
Year: 2014
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: Chaotic cold accretion (CCA) profoundly differs from classic black hole accretion models. Using 3D high-resolution simulations, we probe the impact of rotation on the hot and cold accretion flow in a typical massive galaxy. In the hot mode, with or without turbulence, the pressure-dominated flow forms a geometrically thick rotational barrier, suppressing the accretion rate to ~1/3 of the Bondi rate. When radiative cooling is dominant, the gas loses pressure support and quickly circularizes in a cold thin disk. In the more common state of a turbulent and heated atmosphere, CCA drives the dynamics if the gas velocity dispersion exceeds the rotational velocity, i.e., turbulent Taylor number < 1. Extended multiphase filaments condense out of the hot phase via thermal instability and rain toward the black hole, boosting the accretion rate up to 100 times the Bondi rate. Initially, turbulence broadens the angular momentum distribution of the hot gas, allowing the cold phase to condense with prograde or retrograde motion. Subsequent chaotic collisions between the cold filaments, clouds, and a clumpy variable torus promote the cancellation of angular momentum, leading to high accretion rates. The simulated sub-Eddington accretion rates cover the range inferred from AGN cavity observations. CCA predicts inner flat X-ray temperature and $r^{-1}$ density profiles, as recently discovered in M 87 and NGC 3115. The synthetic Hα images reproduce the main features of cold gas observations in massive ellipticals, as the line fluxes and the filaments versus disk morphology. Such dichotomy is key for the long-term AGN feedback cycle. As gas cools, filamentary CCA develops and boosts AGN heating; the cold mode is thus reduced and the rotating disk remains the sole cold structure. Its consumption leaves the atmosphere in hot mode with suppressed accretion and feedback, reloading the cycle.
description: 18 pages, 21 figures, published in A&A; fully revised version with new major results related to H{\alpha} and X-ray observations
A holographic study of the characteristics of chaos and correlation in the presence of backreaction
Creators: name: Chakrabortty, Shankhadeep
name: Hoshino, Hironori
name: Pant, Sanjay
name: Sil, Karunava
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: In this work, we perform a holographic study to estimate the effect of backreaction on the correlation between two subsystems forming the thermofield double (TFD) state. Each of these subsystems is described as a strongly coupled large-$N_c$ thermal field theory, and the backreaction imparted to it is sourced by the presence of a uniform distribution of heavy static quarks. The TFD state we consider here holographically corresponds to an entangled state of two AdS blackholes, each of which is deformed by a uniform distribution of static strings. In order to make a holographic estimation of correlation between two entangled boundary field theories in presence of backreaction we compute the holographic mutual information in the backreacted eternal blackhole. The late time exponential growth of an early perturbation is a signature of chaos in the boundary thermal field theory. Using the shock wave analysis in the dual bulk theory, we characterize this chaotic behavior by computing the holographic butterfly velocity. We find that there is a reduction in the butterfly velocity due to a correction term that depends on the backreaction parameter. The late time exponential growth of an early perturbation destroys the two-sided correlation, whereas the backreaction always acts in favour of it. Finally we compute the entanglement velocity that essentially encodes the rate of disruption of correlation between two boundary theories.
description: 17 pages, 8 figures
Asymptotic theory for density ridges
Creators: name: Chen, Yen-Chi
name: Genovese, Christopher R.
name: Wasserman, Larry
Publisher: name: arXiv
Year: 2014
Subjects: subject: Methodology (stat.ME)
subject: Statistics Theory (math.ST)
subject: FOS: Computer and information sciences
subject: FOS: Mathematics

description: The large sample theory of estimators for density modes is well understood. In this paper we consider density ridges, which are a higher-dimensional extension of modes. Modes correspond to zero-dimensional, local high-density regions in point clouds. Density ridges correspond to $s$-dimensional, local high-density regions in point clouds. We establish three main results. First we show that under appropriate regularity conditions, the local variation of the estimated ridge can be approximated by an empirical process. Second, we show that the distribution of the estimated ridge converges to a Gaussian process. Third, we establish that the bootstrap leads to valid confidence sets for density ridges.
description: Published at http://dx.doi.org/10.1214/15-AOS1329 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org)
Hybrid Dielectric-Plasmonic Nanoantenna with Multiresonances for Subwavelength Photon Sources
Creators: name: Dmitriev, Pavel A.
name: Lassalle, Emmanuel
name: Ding, Lu
name: Pan, Zhenying
name: Neo, Darren C. J.
name: Valuckas, Vytautas
name: Paniagua-Dominguez, Ramón
name: Yang, Joel K. W.
name: Demir, Hilmi Volkan
name: Kuznetsov, Arseniy I.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: The enhancement of the photoluminescence of quantum dots induced by an optical nanoantenna has been studied considerably, but there is still significant interest in optimizing and miniaturizing such structures, especially when accompanied by an experimental demonstration. Most of the realizations use plasmonic platforms, and some also use all-dielectric nanoantennas, but hybrid dielectric-plasmonic (subwavelength) nanostructures have been very little explored. In this paper, we propose and demonstrate single subwavelength hybrid dielectric-plasmonic optical nanoantennas coupled to localized quantum dot emitters that constitute efficient and bright unidirectional photon sources under optical pumping. To achieve this, we devised a silicon nanoring sitting on a gold mirror with a 10 nm gap in-between, where an assembly of colloidal quantum dots is embedded. Such a structure supports both (radiative) antenna mode and (nonradiative) gap mode resonances, which we exploit for the dual purpose of out-coupling the light emitted by the quantum dots into the far-field with out-of-plane directivity, and for enhancing the excitation of the dots by the optical pump. Moreover, almost independent control of the resonance spectral positions can be achieved by simple tuning of geometrical parameters such as the ring inner and outer diameters, allowing us to conveniently adjust these resonances with respect to the quantum dots emission and absorption wavelengths. Using the proposed architecture, we obtain experimentally average fluorescence enhancement factors up to $654\times$ folds mainly due to high radiative efficiencies, and associated with a directional emission of the photoluminescence into a cone of $\pm 17\degree$ in the direction normal to the sample plane. We believe the solution presented here to be viable and relevant for the next generation of light-emitting devices.
description: 39 pages, 4 figures
The Static Lengthscale Characterizing the Glass Transition at Lower Temperatures
Creators: name: Gutiérrez, Ricardo
name: Karmakar, Smarajit
name: Pollack, Yoav G.
name: Procaccia, Itamar
Publisher: name: arXiv
Year: 2014
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: The existence of a static lengthscale that grows in accordance with the dramatic slowing down observed at the glass transition is a subject of intense interest. A recent publication compared two proposals for this length scale, one based on the point-to-set correlation technique and the other on the scale where the lowest eigenvalue of the Hessian matrix becomes sensitive to disorder. The conclusion was that both approaches lead to the same lengthscale, but the former is easier to measure at higher temperatures and the latter at lower temperatures. But even after using both methods together, the range of increase in the observed lengthscales was limited by the relaxation times reachable by standard molecular dynamics techniques (i.e. about 4-5 orders of magnitude). In this paper we therefore attempt to explore the typical scale at even lower temperatures, testing for this purpose two approaches, one based on the idea of vapor deposition and the other on a swap Monte Carlo technique. We conclude that the first approach does not help in getting to lower temperatures, but the second one does so quite effectively. We can reach a typical lengthscale that grows in accordance with at least $15$ orders of magnitude increase in the relaxation time, competing with the best experimental conditions. We conclude by discussing the relationship between the observed lengthscale and various models of the relaxation time.
description: Submitted to EPL. The original arXiv publication was split into two separate works. The discussion of Vapor Deposition was completely removed and will appear in a more detailed study in a future publication. This publication now focuses on the static lengthscale as found from swap Monte Carlo simulations. Additional tests of equilibration of the supercooled liquid are included
LaRa: Latents and Rays for Multi-Camera Bird's-Eye-View Semantic Segmentation
Creators: name: Bartoccioni, Florent
name: Zablocki, Éloi
name: Bursuc, Andrei
name: Pérez, Patrick
name: Cord, Matthieu
name: Alahari, Karteek
Publisher: name: arXiv
Year: 2022
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: Artificial Intelligence (cs.AI)
subject: Robotics (cs.RO)
subject: FOS: Computer and information sciences
subject: 68T45

description: Recent works in autonomous driving have widely adopted the bird's-eye-view (BEV) semantic map as an intermediate representation of the world. Online prediction of these BEV maps involves non-trivial operations such as multi-camera data extraction as well as fusion and projection into a common topview grid. This is usually done with error-prone geometric operations (e.g., homography or back-projection from monocular depth estimation) or expensive direct dense mapping between image pixels and pixels in BEV (e.g., with MLP or attention). In this work, we present 'LaRa', an efficient encoder-decoder, transformer-based model for vehicle semantic segmentation from multiple cameras. Our approach uses a system of cross-attention to aggregate information over multiple sensors into a compact, yet rich, collection of latent representations. These latent representations, after being processed by a series of self-attention blocks, are then reprojected with a second cross-attention in the BEV space. We demonstrate that our model outperforms the best previous works using transformers on nuScenes. The code and trained models are available at https://github.com/valeoai/LaRa
Nonasymptotic Convergence Rates for Cooperative Learning Over Time-Varying Directed Graphs
Creators: name: Nedić, Angelia
name: Olshevsky, Alex
name: Uribe, César A.
Publisher: name: arXiv
Year: 2014
Subjects: subject: Optimization and Control (math.OC)
subject: FOS: Mathematics

description: We study the problem of distributed hypothesis testing with a network of agents where some agents repeatedly gain access to information about the correct hypothesis. The group objective is to globally agree on a joint hypothesis that best describes the observed data at all the nodes. We assume that the agents can interact with their neighbors in an unknown sequence of time-varying directed graphs. Following the pioneering work of Jadbabaie, Molavi, Sandroni, and Tahbaz-Salehi, we propose local learning dynamics which combine Bayesian updates at each node with a local aggregation rule of private agent signals. We show that these learning dynamics drive all agents to the set of hypotheses which best explain the data collected at all nodes as long as the sequence of interconnection graphs is uniformly strongly connected. Our main result establishes a non-asymptotic, explicit, geometric convergence rate for the learning dynamic.
A Toolbox for Linear Optics in a 1D Lattice via Minimal Control
Creators: name: Compagno, Enrico
name: Banchi, Leonardo
name: Bose, Sougato
Publisher: name: arXiv
Year: 2014
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Tight binding lattices offer a unique platform in which particles may be either static or mobile depending on the potential barrier between the sites. How to harness this mobility in a many-site lattice for useful operations is still an open question. We show how effective linear optics-like operations between arbitrary lattice sites can be implemented by a minimal local control which introduces a local impurity in the middle of the lattice. In particular we show how striking is the difference of the two possible correlations with and without the impurity. Our scheme enables the observation of the Hong-Ou-Mandel effect between distant wells without moving them next to each other with, e.g., tweezers. Moreover, we show that a tunable Mach-Zehnder interferometer is implemented adding a step-like potential, and we prove the robustness of our linear optics scheme to inter-particle interactions.
description: 11 pages, 11 figures
BOTAN: BOnd TArgeting Network for prediction of slow glassy dynamics by machine learning relative motion
Creators: name: Shiba, Hayato
name: Hanai, Masatoshi
name: Suzumura, Toyotaro
name: Shimokawabe, Takashi
Publisher: name: arXiv
Year: 2022
Subjects: subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: Soft Condensed Matter (cond-mat.soft)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: Recent developments in machine learning have enabled accurate predictions of the dynamics of slow structural relaxation in glass-forming systems. However, existing machine-learning models for these tasks are mostly designed such that they learn a single dynamic quantity and relate it to the structural features of glassy liquids. In this study, we propose a graph neural network model, ``BOnd TArgeting Network (BOTAN)'', that learns relative motion between neighboring pairs of particles, in addition to the self-motion of particles. By relating the structural features to these two different dynamical variables, the model autonomously acquires the ability to discern how different dynamical processes, strain fluctuations and particle rearrangements, affect the self-motion of particles undergoing slow relaxation, and thus can predict with high precision how slow structural relaxation develops in space and time.
description: 11 pages, 10 figures, a typo fixed in the title; accepted in J. Chem. Phys
La biologia del SARS-Cov-2 - Hoja de trabajo
Creators: Liliana Fernández-Suárez
Publisher: name: HHMI BioInteractive Educator Resource Library
Year: 2023

Esta modificación incluye clarificaciones de términos de genética y un enfoque en la descripción y comprensión de la estructura del virus SARS-CoV-2. Algunas actividades han sido adaptadas para facilitar la discusión entre pares.
Josephson and Persistent Spin Currents in Bose-Einstein Condensates of Magnons
Creators: name: Nakata, Kouki
name: van Hoogdalem, Kevin A.
name: Simon, Pascal
name: Loss, Daniel
Publisher: name: arXiv
Year: 2014
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Quantum Gases (cond-mat.quant-gas)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: Using the Aharonov-Casher (A-C) phase, we present a microscopic theory of the Josephson and persistent spin currents in quasi-equilibrium Bose-Einstein condensates (BECs) of magnons in ferromagnetic insulators. Starting from a microscopic spin model that we map onto a Gross-Pitaevskii Hamiltonian, we derive a two-state model for the Josephson junction between the weakly coupled magnon-BECs. We then show how to obtain the alternating-current (ac) Josephson effect with magnons as well as macroscopic quantum self-trapping in a magnon-BEC. We next propose how to control the direct-current (dc) Josephson effect electrically using the A-C phase, which is the geometric phase acquired by magnons moving in an electric field. Finally, we introduce a magnon-BEC ring and show that persistent magnon-BEC currents flow due to the A-C phase. Focusing on the feature that the persistent magnon-BEC current is a steady flow of magnetic dipoles that produces an electric field, we propose a method to directly measure it experimentally.
description: 8 pages, 6 figures, updated into published version
Entanglement between uncoupled modes with time-dependent complex frequencies
Creators: name: Cius, D.
name: Uhdre, G. M.
name: de Castro, A. S. M.
name: Andrade, F. M.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Physics (quant-ph)
subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: In this work we present the general unified description for the unitary time-evolution generated by time-dependent non-Hermitian Hamiltonians embedding the bosonic representations of $\mathfrak{su}(1,1)$ and $\mathfrak{su}(2)$ Lie algebras. We take into account a time-dependent Hermitian Dyson maps written in terms of the elements of those algebras with the relation between non-Hermitian and its Hermitian counterpart being independent of the algebra realization. As a direct consequence, we verify that a time-evolved state of uncoupled modes modulated by a time-dependent complex frequency may exhibits a non-zero entanglement even when the cross-operators, typical of the interaction between modes, are absent. This is due the non-local nature of the non-trivial dynamical Hilbert space metric encoded in the time-dependent parameters of the general Hermitian Dyson map, which depend on the imaginary part of the complex frequency.
description: 11 pages, 7 figures
X-ray imaging and radiation transport effects on cylindrical implosions
Creators: name: Pérez-Callejo, G.
name: Bailly-Grandvaux, M.
name: Florido, R.
name: Walsh, C. A.
name: Gigosos, M. A.
name: Beg, F. N.
name: McGuffey, C.
name: Mancini, R. C.
name: Suzuki-Vidal, F.
name: Vlachos, C.
name: Bradford, P.
name: Santos, J. J.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Plasma Physics (physics.plasm-ph)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: Magnetization of inertial confinement implosions is a promising means of improving their performance, owing to the potential reduction of energy losses within the target and mitigation of hydrodynamic instabilities. In particular, cylindrical implosions are useful for studying the influence of a magnetic field thanks to their axial symmetry. Here we present experimental results from cylindrical implosions on the OMEGA-60 laser using a 40-beam, 14.5 kJ, 1.5 ns drive and an initial seed magnetic field of B0=24 T along the axis of the targets, compared with reference results without an imposed B-field. Implosions were characterized using time-resolved X-ray imaging from two orthogonal lines of sight. We found that the data agree well with magnetohydrodynamic simulations once radiation transport within the imploding plasma is considered. We show that for a correct interpretation of the data in this type of experiments, explicit radiation transport must be taken into account.
Koopman-Model Predictive Control with Signal Temporal Logic Specifications for Temperature Regulation of a Warm-Water Supply System
Creators: name: Miyashita, Ryo
name: Susuki, Yoshihiko
name: Ishigame, Atsushi
Publisher: name: arXiv
Year: 2022
Subjects: subject: Systems and Control (eess.SY)
subject: Dynamical Systems (math.DS)
subject: Optimization and Control (math.OC)
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Mathematics

description: Control of warm-water supply for dialysis treatment in a hospital environment is typical of safety-critical control problems. In order to guarantee the continuity of warm-water supply satisfying physical specifications for a wide range of operating conditions, it is inevitable to consider the nonlinearity involved in a dynamic model of a warm-water supply system for the control design. In this paper, we propose to incorporate control specifications described by signal temporal logic, which is a temporal logic with semantics over finite-time signals in formal methods, into the so-called Koopman-Model Predictive Control (MPC) as a novel technique of nonlinear MPC based on the Koopman operator framework for nonlinear systems. This enables us to generate a sequence of optimal inputs such that the controlled state of a nonlinear system can satisfy the specifications. The proposal is applied to the temperature regulation of warm-water supply, and its effectiveness is established numerically.
description: 12 pages, 5 figures
From Lattice Gauge Theories to Hydrogen Atoms
Creators: name: Mathur, Manu
name: Sreeraj, T. P.
Publisher: name: arXiv
Year: 2014
Subjects: subject: High Energy Physics - Lattice (hep-lat)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: High Energy Physics - Theory (hep-th)
subject: Atomic Physics (physics.atom-ph)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We construct canonical transformations to obtain a complete and most economical realization of the physical Hilbert space ${\cal H}^p$ of pure $SU(2)_{2+1}$ lattice gauge theory in terms of Wigner coupled Hilbert spaces of hydrogen atoms. One hydrogen atom is assigned to every plaquette of the lattice. A complete orthonormal description of the Wilson loop basis in ${\cal H}^p$ is obtained by all possible angular momentum Wigner couplings of hydrogen atom energy eigenstates $\vert n~l~m\rangle$ describing electric fluxes on the loops. The SU(2) gauge invariance implies that the total angular momenta of all hydrogen atoms vanish. The canonical transformations also enable us to rewrite the Kogut-Susskind Hamiltonian in terms of fundamental Wilson loop operators and their conjugate electric fields. The resulting loop Hamiltonian has a global SU(2) invariance and a simple weak coupling ($g^2\rightarrow 0$) continuum limit. The canonical transformations leading to the loop Hamiltonian are valid for any SU(N). The ideas and techniques can also be extended to higher dimension.
description: 8 pages, 5 figures. minor typos corrected, minor changes in abstract
Nonstationary data stream classification with online active learning and siamese neural networks
Creators: name: Malialis, Kleanthis
name: Panayiotou, Christos G.
name: Polycarpou, Marios M.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Machine Learning (cs.LG)
subject: FOS: Computer and information sciences

description: We have witnessed in recent years an ever-growing volume of information becoming available in a streaming manner in various application areas. As a result, there is an emerging need for online learning methods that train predictive models on-the-fly. A series of open challenges, however, hinder their deployment in practice. These are, learning as data arrive in real-time one-by-one, learning from data with limited ground truth information, learning from nonstationary data, and learning from severely imbalanced data, while occupying a limited amount of memory for data storage. We propose the ActiSiamese algorithm, which addresses these challenges by combining online active learning, siamese networks, and a multi-queue memory. It develops a new density-based active learning strategy which considers similarity in the latent (rather than the input) space. We conduct an extensive study that compares the role of different active learning budgets and strategies, the performance with/without memory, the performance with/without ensembling, in both synthetic and real-world datasets, under different data nonstationarity characteristics and class imbalance levels. ActiSiamese outperforms baseline and state-of-the-art algorithms, and is effective under severe imbalance, even only when a fraction of the arriving instances' labels is available. We publicly release our code to the community.
description: Keywords: Incremental learning, Active learning, Data streams, Concept drift, Class imbalance
Mitigation of quasiparticle loss in superconducting qubits by phonon scattering
Creators: name: Bargerbos, Arno
name: Splitthoff, Lukas Johannes
name: Pita-Vidal, Marta
name: Wesdorp, Jaap J.
name: Liu, Yu
name: Krogstrup, Peter
name: Kouwenhoven, Leo P.
name: Andersen, Christian Kraglund
name: Grünhaupt, Lukas
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Physics (quant-ph)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Quantum error correction will be an essential ingredient in realizing fault-tolerant quantum computing. However, most correction schemes rely on the assumption that errors are sufficiently uncorrelated in space and time. In superconducting qubits this assumption is drastically violated in the presence of ionizing radiation, which creates bursts of high energy phonons in the substrate. These phonons can break Cooper-pairs in the superconductor and, thus, create quasiparticles over large areas, consequently reducing qubit coherence across the quantum device in a correlated fashion. A potential mitigation technique is to place large volumes of normal or superconducting metal on the device, capable of reducing the phonon energy to below the superconducting gap of the qubits. To investigate the effectiveness of this method we fabricate a quantum device with four nominally identical nanowire-based transmon qubits. On the device, half of the niobium-titanium-nitride ground plane is replaced with aluminum (Al), which has a significantly lower superconducting gap. We deterministically inject high energy phonons into the substrate by voltage biasing a galvanically isolated Josephson junction. In the presence of the low gap material, we find a factor of 2-5 less degradation in the injection-dependent qubit lifetimes, and observe that undesired excited qubit state population is mitigated by a similar factor. We furthermore turn the Al normal with a magnetic field, finding no change in the phonon-protection. This suggests that the efficacy of the protection in our device is not limited by the size of the superconducting gap in the Al ground plane. Our results provide a promising foundation for protecting superconducting qubit processors against correlated errors from ionizing radiation.
description: Main: 9 pages, 4 figures. Supp: 10 pages, 6 figures
The Sherwood-Relics simulations: overview and impact of patchy reionization and pressure smoothing on the intergalactic medium
Creators: name: Puchwein, Ewald
name: Bolton, James S.
name: Keating, Laura C.
name: Molaro, Margherita
name: Gaikwad, Prakash
name: Kulkarni, Girish
name: Haehnelt, Martin G.
name: Iršič, Vid
name: Šoltinský, Tomáš
name: Viel, Matteo
name: Aubert, Dominique
name: Becker, George D.
name: Meiksin, Avery
Publisher: name: arXiv
Year: 2022
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We present the Sherwood-Relics simulations, a new suite of large cosmological hydrodynamical simulations aimed at modelling the intergalactic medium (IGM) during and after the cosmic reionization of hydrogen. The suite consists of over 200 simulations that cover a wide range of astrophysical and cosmological parameters. It also includes simulations that use a new lightweight hybrid scheme for treating radiative transfer effects. This scheme follows the spatial variations in the ionizing radiation field, as well as the associated fluctuations in IGM temperature and pressure smoothing. It is computationally much cheaper than full radiation hydrodynamics simulations and circumvents the difficult task of calibrating a galaxy formation model to observational constraints on cosmic reionization. Using this hybrid technique, we study the spatial fluctuations in IGM properties that are seeded by patchy cosmic reionization. We investigate the relevant physical processes and assess their impact on the z > 4 Lyman-alpha forest. Our main findings are: (i) Consistent with previous studies patchy reionization causes large scale temperature fluctuations that persist well after the end of reionization, (ii) these increase the Lyman-alpha forest flux power spectrum on large scales, and (iii) result in a spatially varying pressure smoothing that correlates well with the local reionization redshift. (iv) Structures evaporated or puffed up by photoheating cause notable features in the Lyman-alpha forest, such as flat-bottom or double-dip absorption profiles.
description: Version accepted for publication in MNRAS, some discussions added, data added to Fig. 8. 24 pages, 15 figures. Images and movies may be viewed at https://www.nottingham.ac.uk/astronomy/sherwood-relics/
The noncommutative factor theorem for lattices in product groups
Creators: name: Boutonnet, Rémi
name: Houdayer, Cyril
Publisher: name: arXiv
Year: 2022
Subjects: subject: Operator Algebras (math.OA)
subject: Dynamical Systems (math.DS)
subject: Group Theory (math.GR)
subject: FOS: Mathematics

description: We prove a noncommutative Bader-Shalom factor theorem for lattices with dense projections in product groups. As an application of this result and our previous works, we obtain a noncommutative Margulis factor theorem for all irreducible lattices $Γ< G$ in higher rank semisimple algebraic groups. Namely, we give a complete description of all intermediate von Neumann subalgebras $\operatorname{L}(Γ) \subset M \subset \operatorname{L}(Γ\curvearrowright G/P)$ sitting between the group von Neumann algebra and the group measure space von Neumann algebra associated with the action on the Furstenberg-Poisson boundary.
description: 12 pages. To appear in J. \'Ec. polytech. Math
Coupled spin-valley, Rashba effect and hidden persistent spin polarization in WSi$_2$N$_4$ family
Creators: name: Sheoran, Sajjan
name: Gill, Deepika
name: Phutela, Ankita
name: Bhattacharya, Saswata
Publisher: name: arXiv
Year: 2022
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: The new two-dimensional materials, MoSi$_2$N$_4$ and WSi$_2$N$_4$ are experimentally synthesized successfully and various similar structures are predicted theoretically. Here, we report the electronic properties with a special focus on the band splitting in WA$_2$Z$_4$ (A=Si, Ge; Z=N, P, As), using state-of-the-art density functional theory and many-body perturbation theory (within the framework of G$_0$W$_0$ and BSE). Due to the broken inversion symmetry and strong spin-orbit coupling effects, we detect coupled spin-valley effects at the corners of the first Brillouin zone (BZ). Additionally, we observe cubically and linearly split bands around the $Γ$ and M points, respectively. Interestingly, the in-plane mirror symmetry ($σ_h$) and the reduced symmetry of arbitrary $k$-point, enforce the persistent spin textures (PST) to occur in full BZ. We induce the Rashba splitting by breaking the $σ_h$ through an out-of-plane external electric field (EEF). The inversion asymmetric site point group of the W atom introduces the hidden spin polarization in centrosymmetric layered bulk counterparts. Therefore, the spin-layer locking effect, namely, energy degenerate opposite spins spatially segregated in the top and bottom W layers, has been identified. Our low energy $k.p$ model demonstrates that the PST along the M-K line is robust to EEF and layer thickness, making them suitable for applications in spintronics and valleytronics.
SPRAT: A Spatially-Explicit Marine Ecosystem Model Based on Population Balance Equations
Creators: name: Johanson, Arne N.
name: Oschlies, Andreas
name: Hasselbring, Wilhelm
name: Hasselbring, Wilhelm
name: Worm, Boris
Publisher: name: arXiv
Year: 2022
Subjects: subject: Populations and Evolution (q-bio.PE)
subject: Computational Engineering, Finance, and Science (cs.CE)
subject: FOS: Biological sciences
subject: FOS: Computer and information sciences
subject: I.6.5

description: To successfully manage marine fisheries using an ecosystem-based approach, long-term predictions of fish stock development considering changing environmental conditions are necessary. Such predictions can be provided by end-to-end ecosystem models, which couple existing physical and biogeochemical ocean models with newly developed spatially-explicit fish stock models. Typically, Individual-Based Models (IBMs) and models based on Advection-Diffusion-Reaction (ADR) equations are employed for the fish stock models. In this paper, we present a novel fish stock model called SPRAT for end-to\hyp{}end ecosystem modeling based on Population Balance Equations (PBEs) that combines the advantages of IBMs and ADR models while avoiding their main drawbacks. SPRAT accomplishes this by describing the modeled ecosystem processes from the perspective of individuals while still being based on partial differential equations. We apply the SPRAT model to explore a well-documented regime shift observed on the eastern Scotian Shelf in the 1990s from a cod-dominated to a herring-dominated ecosystem. Model simulations are able to reconcile the observed multitrophic dynamics with documented changes in both fishing pressure and water temperature, followed by a predator-prey reversal that may have impeded recovery of depleted cod stocks. We conclude that our model can be used to generate new hypotheses and test ideas about spatially interacting fish populations, and their joint responses to both environmental and fisheries forcing.
description: 20 pages
An Analytical Framework for Device-to-Device Communication in Cellular Networks
Creators: name: George, Geordie
name: Mungara, Ratheesh K.
name: Lozano, Angel
Publisher: name: arXiv
Year: 2014
Subjects: subject: Information Theory (cs.IT)
subject: FOS: Computer and information sciences

description: This paper presents a framework that enables characterizing analytically the spectral efficiency achievable by D2D (device-to-device) communication integrated with a cellular network. This framework is based on a stochastic geometry formulation with a novel approach to the modeling of interference and with the added possibility of incorporating exclusion regions to protect cellular receivers from excessive interference from active D2D transmitters. To illustrate the potential of the framework, a number of examples are provided. These examples confirm the potential of D2D communication in situations of strong traffic locality as well as the effectiveness of properly sized exclusion regions.
description: 14 pages, 13 figures, to appear in the IEEE Transactions on Wireless Communications, 2015
Bose-Einstein-Like condensation of deformed random matrix: A replica approach
Creators: name: Ikeda, Harukuni
Publisher: name: arXiv
Year: 2022
Subjects: subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: In this work, we investigate a symmetric deformed random matrix, which is obtained by perturbing the diagonal elements of the Wigner matrix. The eigenvector $\mathbf{x}_{\rm min}$ of the minimal eigenvalue $λ_{\rm min}$ of the deformed random matrix tends to condensate at a single site. In certain types of perturbations and in the limit of the large components, this condensation becomes a sharp phase transition, the mechanism of which can be identified with the Bose-Einstein condensation in a mathematical level. We study this Bose-Einstein like condensation phenomenon by means of the replica method. We first derive a formula to calculate the minimal eigenvalue and the statistical properties of $\mathbf{x}_{\rm min}$. Then, we apply the formula for two solvable cases: when the distribution of the perturbation has the double peak, and when it has a continuous distribution. For the double peak, we find that at the transition point, the participation ratio changes discontinuously from a finite value to zero. On the contrary, in the case of a continuous distribution, the participation ratio goes to zero either continuously or discontinuously, depending on the distribution.
description: 20 pages, 11 figures
Boltzmann equations for astrophysical Stochastic Gravitational Wave Backgrounds scattering off of massive objects
Creators: name: Pizzuti, Lorenzo
name: Tomella, Alessandro
name: Carbone, Carmelita
name: Calabrese, Matteo
name: Baccigalupi, Carlo
Publisher: name: arXiv
Year: 2022
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: This work presents a set of coupled Boltzmann equations describing the intensity and polarisation Stokes parameters of the SGWB. Collision terms, which account for gravitational Compton scattering off of massive objects, are also included. This set resembles that for the CMB Stokes parameters, but the different spin nature of the gravitational radiation and the physics involved in the scattering process determine crucial differences. In this case, due to the Rutherford angular dependence of the cross section, all the SGWB intensity multipoles of order $\ell$ are scattered out, producing outgoing intensity anisotropies of any order $\ell$ if they are present in the incoming radiation. On the other hand, SGWB linear polarisation modes can be expanded in a basis of spherical harmonics with $m=\pm 4$ and $\ell\ge 4$. This means that SGWB polarisation modes can be generated from unpolarised anisotropic radiation only with $m=\pm 4$, therefore requiring at least a hexadecapole anisotropy ($\ell\ge 4$) in the incoming intensity. Assuming a simplified toy model, we solve analytically the set of coupled Boltzmann equations to get explicit expressions for the intensity and polarisation angular power spectra. We confirm the contribution of the gravitational Compton scattering to the SGWB anisoptropies is extremely small for collisions with compact objects in the frequency range of current and upcoming surveys. The system of coupled Boltzmann equations presented here provides a way to an accurate estimate of the total amount of anisotropies generated by multiple SGWB scattering processes off of massive objects, as well as the interplay between polarisation and intensity, during the GW propagation across the LSS of the universe. These results will be useful for the full treatment of the astrophysical SWGB anisotropies in view of upcoming gravitational waves observatories.
description: 28 pages, 2 tables, 2 figures. Matches the accepted version in JCAP
Confinement in non-Abelian lattice gauge theory via persistent homology
Creators: name: Spitz, Daniel
name: Urban, Julian M.
name: Pawlowski, Jan M.
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Lattice (hep-lat)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Theory (hep-th)
subject: Algebraic Topology (math.AT)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: We investigate the structure of confining and deconfining phases in SU(2) lattice gauge theory via persistent homology, which gives us access to the topology of a hierarchy of combinatorial objects constructed from given data. Specifically, we use filtrations by traced Polyakov loops, topological densities, holonomy Lie algebra fields, as well as electric and magnetic fields. This allows for a comprehensive picture of confinement. In particular, topological densities form spatial lumps which show signatures of the classical probability distribution of instanton-dyons. Signatures of well-separated dyons located at random positions are encoded in holonomy Lie algebra fields, following the semi-classical temperature dependence of the instanton appearance probability. Debye screening discriminating between electric and magnetic fields is visible in persistent homology and pronounced at large gauge coupling. All employed constructions are gauge-invariant without a priori assumptions on the configurations under study. This work showcases the versatility of persistent homology for statistical and quantum physics studies, barely explored to date.
description: 22 pages, 15 figures, published version
Spatial Markov Semigroups Admit Hudson-Parthasarathy Dilations
Creators: name: Skeide, Michael
Publisher: name: arXiv
Year: 2008
Subjects: subject: Operator Algebras (math.OA)
subject: Probability (math.PR)
subject: FOS: Mathematics
subject: 46L55, 46L53, 60J25, 81S25

description: We present, for the first time, the result (from 2008) that (normal, strongly continuous) Markov semigroups on $\mathscr{B}(G)$ ($G$ a separable Hilbert space) admit a Hudson-Parthasarathy dilation (that is, a dilation to a cocycle perturbation of a noise) if and only if the Markov semigroup is spatial (that is, if it dominates an elementary CP-semigroup). The proof is by general abstract nonsense (taken from Arveson's classification of $E_0$-semigroups on $\mathscr{B}(H)$ by Arveson systems up to cocycle conjugacy) and not, as usual, by constructing the cocycle as a solution of a quantum stochastic differential equation in the sense of Hudson and Parthasarathy. All other results that make similar statements (especially, [Mem. Amer. Math. Soc. 240 (2016), vi+126 pages, arXiv:0901.1798]) for more general $C^*$-algebras) have been proved later by suitable adaptations of the methods exposed here. (They use Hilbert module techniques, which we carefully avoid here in order to make the result available without any appeal to Hilbert modules.)
Power Series Solutions of Non-Linear q-Difference Equations and the Newton-Puiseux Polygon
Creators: name: Cano, José
name: Ayuso, Pedro Fortuny
Publisher: name: arXiv
Year: 2012
Subjects: subject: Algebraic Geometry (math.AG)
subject: FOS: Mathematics
subject: 39A13

description: Adapting the Newton-Puiseux Polygon process to nonlinear q-difference equations of any order and degree, we compute their power series solutions, study the properties of the set of exponents of the solutions and give a bound for their $q-$Gevrey order in terms of the order of the original equation.