cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Quantum critical points, lines and surfaces
Creators: name: Yu, Hui
name: Chakravarty, Sudip
Publisher: name: arXiv
Year: 2022
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: In this paper we promote the idea of quantum critical lines ({\em inter alia} surfaces) as opposed to points. A quantum critical line obtains when criticality at zero temperature is extended over a continuum in a one-dimensional line. We base our ideas on a simple but exactly solved model introduced by one of the authors involving a one-dimensional quantum transverse field Ising model with added 3-spin interaction. While many of the ideas are quite general, there are other aspects that are not. In particular, a line of criticality with continuously varying exponents is not captured. However, the exact solvability of the model gives us considerable confidence in our results. Although the pure system is analytically exactly solved, the disorder case requires numerical analyses based on exact computation of the correlation function in the Pfaffian representation. The disorder case leads to dynamic structure factor as a function of frequency and wave vector. We expect that the model is experientally realizable and perhaps many other similar models will be found to explore quantum critical lines.
description: 11 pages, 11 figures
An Efficient, Sparsity-Preserving, Online Algorithm for Low-Rank Approximation
Creators: name: Anderson, David G.
name: Gu, Ming
Publisher: name: arXiv
Year: 2016
Subjects: subject: Numerical Analysis (math.NA)
subject: FOS: Mathematics

description: Low-rank matrix approximation is a fundamental tool in data analysis for processing large datasets, reducing noise, and finding important signals. In this work, we present a novel truncated LU factorization called Spectrum-Revealing LU (SRLU) for effective low-rank matrix approximation, and develop a fast algorithm to compute an SRLU factorization. We provide both matrix and singular value approximation error bounds for the SRLU approximation computed by our algorithm. Our analysis suggests that SRLU is competitive with the best low-rank matrix approximation methods, deterministic or randomized, in both computational complexity and approximation quality. Numeric experiments illustrate that SRLU preserves sparsity, highlights important data features and variables, can be efficiently updated, and calculates data approximations nearly as accurately as possible. To the best of our knowledge this is the first practical variant of the LU factorization for effective and efficient low-rank matrix approximation.
Perceiving locations of moving objects across eye blinks.
Creators: name: Lisi, Matteo
name: Maus, Gerrit
Publisher: name: Open Science Framework
Year: 2022
Subjects: subject: Life Sciences
subject: Social and Behavioral Sciences
subject: eye-blinks
subject: prediction
subject: visual motion

description: Data and analysis scripts for "Perceiving locations of moving objects across eye blinks", by Maus, Goh & Lisi (2020).
Michel parameters in the presence of massive Dirac and Majorana neutrinos
Creators: name: Márquez, Juan Manuel
name: Castro, Gabriel López
name: Roig, Pablo
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We analyse the effects of Dirac and Majorana neutrinos on leptonic decays of muon and tau leptons using the most general four-lepton effective interaction Hamiltonian of dimension six. We calculate the specific energy and angular distribution of the final charged lepton, including the polarizations of the initial and final charged leptons. We discuss the new generalized Michel parameters and focus on the effects of the heavy neutrino masses that would lead to sizable contributions on scenarios where the new sterile neutrinos have non-negligible mixing. Specifically, the most promising scenario is found for the case of $τ$ decay with one heavy final-state neutrino with a mass around $10^2 - 10^3$ MeV, where the linear term suppression could be of order $10^{-4}$, low enough to be measured in current and forthcoming experiments.
description: 37 pages, 6 figures. Matches published version, wording corrections were made and a realistic example was added, (see new Fig. 5)
Iterative shaping of optical potentials for one-dimensional Bose-Einstein condensates
Creators: name: Deutschmann-Olek, Andreas
name: Tajik, Mohammadamin
name: Calzavara, Martino
name: Schmiedmayer, Jörg
name: Calarco, Tommaso
name: Kugi, Andreas
Publisher: name: arXiv
Year: 2022
Subjects: subject: Systems and Control (eess.SY)
subject: Quantum Gases (cond-mat.quant-gas)
subject: Optics (physics.optics)
subject: Quantum Physics (quant-ph)
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Physical sciences

description: The ability to manipulate clouds of ultra-cold atoms is crucial for modern experiments on quantum manybody systems and quantum thermodynamics as well as future metrological applications of Bose-Einstein condensate. While optical manipulation offers almost arbitrary flexibility, the precise control of the resulting dipole potentials and the mitigation of unwanted disturbances is quite involved and only heuristic algorithms with rather slow convergence rates are available up to now. This paper thus suggests the application of iterative learning control (ILC) methods to generate fine-tuned effective potentials in the presence of uncertainties and external disturbances. Therefore, the given problem is reformulated to obtain a one-dimensional tracking problem by using a quasicontinuous input mapping which can be treated by established ILC methods. Finally, the performance of the proposed concept is illustrated in a simulation scenario.
description: To appear in Proceedings of the 61st IEEE Conference on Decision and Control (CDC)
Athletic Director Leadership and Success in NCAA Division III Athletic Departments
Creators: name: Day, Brian
Publisher: name: University of North Carolina at Chapel Hill
Year: 2013

description: A need has been identified to examine leader behaviors that have a positive influence on the relationships between athletic directors and their subordinates, as well as behaviors that influence the health and effectiveness of the organization (Branch, 1990; Doherty & Danylchuk, 1996). The purpose of this study is to identify the strengths and weaknesses of Division III athletic director leadership, examine the relationship leadership has on success, and determine the leadership behaviors that are most valued. The results conclude Division III athletic directors are generally strong with interpersonal skills, yet lacking in creativity and innovation. No relationship exists between perceived leadership and success on the field, reinforcing the student-athlete experience and integration core values of Division III athletics. Finally, the study determined assistant athletic directors and head coaches value Division III athletic directors who build relationships, are visionary, fair, motivational, driven, and innovative.
Protocol for systematic review of the effects of radiofrequency electromagnetic fields on male fertility as inferred from studies on human sperm exposed in vitro
Creators: name: Pacchierotti, Francesca
name: Ardoino, Lucia
name: Benassi, Barbara
name: Brinkworth, Martin
name: Chen, Guangdi
name: Consales, Claudia
name: Cordelli, Eugenia
name: de Vries, Rob
name: Eleuteri, Patrizia
name: Hooijmans, Carlijn
name: Marino, Carmela
name: McNamee, James
name: Sciortino, Maurizio
name: Wood, Andrew
Publisher: name: Open Science Framework
Year: 2022
Subjects: subject: Environmental Public Health
subject: Public Health
subject: Medicine and Health Sciences
subject: Systematic review; Meta-analysis; Radiofrequency electromagnetic fields; Male infertility; Human sperm; In vitro studies.

description: This project aims at objectively evaluating the associations between RF-EMF exposure and impaired male fertility by a systematic review and meta-analysis of experimental studies evaluating the impact of RF-EMF on human sperm exposed in vitro.
On the Cosmic Web Elongation in Fuzzy Dark Matter Cosmologies: Effects on Density Profiles, Shapes and Alignments of Halos
Creators: name: Dome, Tibor
name: Fialkov, Anastasia
name: Mocz, Philip
name: Schäfer, Björn Malte
name: Boylan-Kolchin, Michael
name: Vogelsberger, Mark
Publisher: name: arXiv
Year: 2022
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: The fuzzy dark matter (FDM) scenario has received increased attention in recent years due to the small-scale challenges of the vanilla Lambda cold dark matter ($Λ$CDM) cosmological model and the lack of any experimental evidence for any candidate particle. In this study, we use cosmological $N$-body simulations to investigate high-redshift dark matter halos and their responsiveness to an FDM-like power spectrum cutoff on small scales in the primordial density perturbations. We study halo density profiles, shapes and alignments in FDM-like cosmologies (the latter two for the first time) by providing fits and quantifying departures from $Λ$CDM as a function of the particle mass $m$. Compared to $Λ$CDM, the concentrations of FDM-like halos are lower, peaking at an $m$-dependent halo mass and thus breaking the approximate universality of density profiles in $Λ$CDM. The intermediate-to-major and minor-to-major shape parameter profiles are monotonically increasing with ellipsoidal radius in $N$-body simulations of $Λ$CDM. In FDM-like cosmologies, the monotonicity is broken, halos are more elongated around the virial radius than their $Λ$CDM counterparts and less elongated closer to the center. Finally, intrinsic alignment correlations, stemming from the deformation of initially spherically collapsing halos in an ambient gravitational tidal field, become stronger with decreasing $m$. At $z\sim 4$, we find a $6.4 σ$-significance in the fractional differences between the isotropised linear alignment magnitudes $D_{\text{iso}}$ in the $m=10^{-22}$ eV model and $Λ$CDM. Such FDM-like imprints on the internal properties of virialised halos are expected to be strikingly visible in the high-$z$ Universe.
description: 20 pages, 10 figures, 3 tables
HALO: Loneliness and Health: The moderating role of befriending services
Creators: name: Hannigan, Caoimhe
name: Power, Joanna
name: Hanly, Paul
name: Kee, Frank
name: Lawlor, Brian
name: Holton, Eimilie
name: Walsh, Cathal
name: Scharf, Thomas
name: Coen, Robert
name: Leatham, Vicky
name: Moynihan, Sean
name: Lane, Keith
Publisher: name: Open Science Framework
Year: 2022
Subjects: subject: Social and Behavioral Sciences
subject: Psychology
subject: FOS: Psychology

description: This is a registration of the study documents at the time of submitting the study protocol for publication on HRB Open Research.
Protected ground states in short chains of coupled spins in circuit quantum electrodynamics
Creators: name: Callison, Adam
name: Grosfeld, Eytan
name: Ginossar, Eran
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: The two degenerate ground states of the anisotropic Heisenberg (XY) spin model of a chain of qubits (pseudo-spins) can encode quantum information, but their degree of protection against local perturbations is known to be only partial. We examine the properties of the system in the presence of non-local spin-spin interactions, possibly emerging from the quantum electrodynamics of the device. We find a phase distinct from the XY phase admitting two ground states which are highly protected against all local field perturbations, persisting across a range of parameters. In the context of the XY chain we discuss how the coupling between two ground states can be used to observe signatures of topological edge states in a small controlled chain of superconducting transmon qubits.
description: 10 pages, 11 figures
Tobacco cessation education in North Carolina dental hygiene programs
Creators: name: Harris, Joanna Lynn.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2008

description: The purpose of the research project was to identify the practices and perceptions of senior dental hygiene students (SDHS) in North Carolina (NC) regarding their didactic training in tobacco cessation education (TCE) and integration of TCE into their clinical dental hygiene curricula. A pilot-tested questionnaire was administered to 241 graduating SDHS enrolled in all 12 NC dental hygiene programs via mail (n=180) or email via SurveyMonkey (n=61). Response rate was 65% (n=156). Of respondents, 99% agreed that hygienists should be trained to provide TCE. Nearly all SDHS (99%) had one or more patients who smoked and 81% had one or more patients who used spit tobacco. Eighty-nine percent had one or more patients that expressed a desire to quit. Most SDHS were comfortable providing TCE to both smokers (92%) and spit tobacco users (93%). Enhancements to TCE in dental hygiene curricula may increase incorporation of TCE by hygienists' in future practice.
Entropy of rigid k-mers on a square lattice
Creators: name: Rodrigues, Lucas R.
name: Stilck, J. F.
name: Dantas, W. G.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: Using the transfer matrix technique, we estimate the entropy for a gas of rods of sizes equal to k (named k-mers), which cover completely a square lattice. Our calculations were made considering three different constructions, using periodical and helical boundary conditions. One of those constructions, which we call Profile Method, was based on the calculations performed by Dhar and Rajesh [Phys. Rev. E 103, 042130 (2021)] to obtain a lower limit to the entropy of very large chains placed on the square lattice. This method, so far as we know, was never used before to define the transfer matrix, but turned out to be very useful, since it produces matrices with smaller dimensions than those obtained using other approaches. Our results were obtained for chain sizes ranging from k=2 to k=10 and they are compared with results already available in the literature. In the case of dimers ($k=2$) our results are compatible with the exact result, for trimers ($k=3$), recently investigated by Ghosh et al [Phys. Rev. E 75, 011115 (2007)] also our results were compatible, the same happening for the simulational estimates obtained by Pasinetti et al [Physical Review E 104, 054136 (2021)] in the whole range of rod sizes. Our results are consistent with the asymptotic expression for the behavior of the entropy as a function of the size $k$, proposed by Dhar and Rajesh [Phys. Rev. E 103, 042130 (2021)] for very large rods (k>>1).
description: 12 pages, 9 figures
Ehrenfest approach to open double-well dynamics
Creators: name: Choi, Stephen
name: Onofrio, Roberto
name: Sundaram, Bala
Publisher: name: arXiv
Year: 2015
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We consider an Ehrenfest approximation for a particle in a double-well potential in the presence of an external environment schematized as a finite resource heat bath. This allows us to explore how the limitations in the applicability of Ehrenfest dynamics to nonlinear systems are modified in an open system setting. Within this framework, we have identified an environment-induced spontaneous symmetry breaking mechanism, and we argue that the Ehrenfest approximation becomes increasingly valid in the limit of strong coupling to the external reservoir, either in the form of increasing number of oscillators or increasing temperature. The analysis also suggests a rather intuitive picture for the general phenomenon of quantum tunneling and its interplay with classical thermal activation processes, which may be of relevance in physical chemistry, ultracold atom physics, and fast-switching dynamics such as in superconducting digital electronics.
description: 7 pages, 7 figures
Instrumental variable estimation of dynamic treatment effects on a duration outcome
Creators: name: Beyhum, Jad
name: Centorrino, Samuele
name: Florens, Jean-Pierre
name: Van Keilegom, Ingrid
Publisher: name: Taylor & Francis
Year: 2023
Subjects: subject: Medicine
subject: Neuroscience
subject: Biotechnology
classificationCode: 19999
subject: Mathematical Sciences not elsewhere classified
subject: Cancer
subject: Computational Biology

description: This paper considers identification and estimation of the causal effect of the time Z until a subject is treated on a duration T. The time-to-treatment is not randomly assigned, T is randomly right censored by a random variable C, and the time-to-treatment Z is right censored by T∧C. The endogeneity issue is treated using an instrumental variable explaining Z and independent of the error term of the model. We study identification in a fully nonparametric framework. We show that our specification generates an integral equation, of which the regression function of interest is a solution. We provide identification conditions that rely on this identification equation. We assume that the regression function follows a parametric model for estimation purposes. We propose an estimation procedure and give conditions under which the estimator is asymptotically normal. The estimators exhibit good finite sample properties in simulations. Our methodology is applied to evaluate the effect of the timing of a therapy for burnout.
Linking discrete and continuum diffusion models: Well-posedness and stable finite element discretizations
Creators: name: Schenk, Christina
name: Portillo, David
name: Romero, Ignacio
Publisher: name: arXiv
Year: 2022
Subjects: subject: Numerical Analysis (math.NA)
subject: Mathematical Physics (math-ph)
subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics
subject: FOS: Physical sciences

description: In the context of mathematical modeling, it is sometimes convenient to integrate models of different nature. These types of combinations, however, might entail difficulties even when individual models are well-understood, particularly in relation to the well-posedness of the ensemble. In this article, we focus on combining two classes of dissimilar diffusive models: the first one defined over a continuum and the second one based on discrete equations that connect average values of the solution over disjoint subdomains. For stationary problems, we show unconditional stability of the linked problems and then the stability and convergence of its discretized counterpart when mixed finite elements are used to approximate the model on the continuum. The theoretical results are highlighted with numerical examples illustrating the effects of linking diffusive models. As a side result, we show that the methods introduced in this article can be used to infer the solution of diffusive problems with incomplete data.
description: 22 pages, 7 figures, preprint. International Journal for Numerical Methods in Engineering (2023)
Easy-plane anisotropic-exchange magnets on a honeycomb lattice: quantum effects and dealing with them
Creators: name: Maksimov, P. A.
name: Chernyshev, A. L.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We provide analytical and numerical insights into the phase diagram and other properties of the extended Kitaev-Heisenberg model on the honeycomb lattice in the {\it easy-plane} limit, in which interactions are only between spin components that belong to the plane of magnetic ions. This parameter subspace allows for a much-needed systematic {\it quantitative} investigation of spin excitations in the ordered phases and of their generic features. Specifically, we demonstrate that in this limit one can consistently take into account magnon interactions in both zero-field zigzag and field-polarized phases. For the nominally polarized phase, we propose a regularization of the unphysical divergences that occur at the critical field and are plaguing the $1/S$-approximation in this class of models. For the explored parameter subspace, all symmetry-allowed terms of the standard parametrization of the extended Kitaev-Heisenberg model, such as $K$, $J$, and $Γ$, are significant, making the offered consideration relevant to a much wider parameter space. The dynamical structure factor near paramagnetic critical point illustrates this relevance by showing features that are reminiscent of the ones observed in $α$-RuCl$_3$, underscoring that they are not unique and should be common to a wide range of parameters of the model and, by an extension, to other materials.
description: 28 pages, 14 figures
Natural cubic splines for the analysis of Alzheimer's clinical trials
Creators: name: Donohue, M. C.
name: Langford, O.
name: Insel, P.
name: van Dyck, C. H.
name: Petersen, R. C.
name: Craft, S.
name: Sethuraman, G.
name: Raman, R.
name: Aisen, P. S.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Applications (stat.AP)
subject: FOS: Computer and information sciences

description: Mixed model repeated measures (MMRM) is the most common analysis approach used in clinical trials for Alzheimer's disease and other progressive diseases measured with continuous outcomes measured over time. The model treats time as a categorical variable, which allows an unconstrained estimate of the mean for each study visit in each randomized group. Categorizing time in this way can be problematic when assessments occur off-schedule, as including off-schedule visits can induce bias, and excluding them ignores valuable information and violates the intention to treat principle. This problem has been exacerbated by clinical trial visits which have been delayed due to the COVID19 pandemic. As an alternative to MMRM, we propose a constrained longitudinal data analysis with natural cubic splines that treats time as continuous and uses test version effects to model the mean over time. The spline model is shown to be superior, in practice and simulation studies, to categorical-time models like MMRM and models that assume a proportional treatment effect.
Creating Airy beams employing a transmissive spatial light modulator
Creators: name: Latychevskaia, Tatiana
name: Schachtler, Daniel
name: Fink, Hans-Werner
Publisher: name: arXiv
Year: 2016
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: We present a detailed study of two novel methods for shaping the light optical wavefront by employing a transmissive spatial light modulator (SLM). Conventionally, optical Airy beams are created by employing SLMs in the so-called all phase mode. In the first method, a numerically simulated lens phase distribution is loaded directly onto the SLM, together with the cubic phase distribution. An Airy beam is generated at the focal plane of the numerical lens. We provide for the first time a quantitative properties of the formed Airy beam. We derive the formula for deflection of the intensity maximum of the so formed Airy beam, which is different to the quadratic deflection typical of Airy beams. We cross-validate the derived formula by both simulations and experiment. The second method is based on the fact that a system consisting of a transmissive SLM sandwiched between two polarisers can create a transmission function with negative values. This observation alone has the potential for various other wavefront modulations where the transmission function requires negative values. As an example for this method, we demonstrate that a wavefront can be modulated by passing the SLM system with transmission function with negative values by loading an Airy function distribution directly onto SLM. Since the Airy function is a real-valued function but also with negative values, an Airy beam can be generated by direct transfer of the Airy function distribution onto such an SLM system. In this way, an Airy beam is generated immediately behind the SLM. As both new methods do not employ a physical lens, the two setups are more compact than conventional setups for creating Airy beams. We compare the performance of the two novel methods and the properties of the created Airy beams.
Valence state and lattice incorporation of Ni in Zn/Co-based magnetic oxides
Creators: name: Ney, V.
name: Henne, B.
name: de Souza, M.
name: Jantsch, W.
name: Johansen, K. M.
name: Wilhelm, F.
name: Rogalev, A.
name: Ney, A.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Ni incorporation has been studied in a comprehensive range of Zn/Co-based magnetic oxides to elucidate it valence state and lattice incorporation. The resulting structural and magnetic properties are studied in detail. To the one end Ni in incorporated by in-diffusion as well as reactive magnetron co-sputtering in wurtzite ZnO where only the Ni-diffused ZnO exhibits significant conductivity. This is complemented by Ni and Co codoping of ZnO leading. To the other end, the ZnCo$_2$O$_4$ spinel is co-doped with varying amounts of Ni. In the wurtzite oxides Ni is exclusively found on tetrahedral lattice sites in its formal 2+ oxidation state as deep donor. It behaves as an anisotropic paramagnet and a limited solubility of Ni about 10\% is found. Due to its smaller magnetic moment it can induce partial uncompensation of the Co magnetic moments due to antiferromagnetic coupling. In the spinel Ni is found to be incorporated in its formal 3+ oxidation state on octahedral sites and couples antiferromagnetically to the Co moments leading again to magnetic uncompensation of the otherwise antiferromagnetic ZnCo$_2$O$_4$ spinel and to ferrimagnetism at higher Ni concentrations. Increasing Ni even further leads to phase separation of cubic NiO resulting in an exchange-biased composite magnetic oxide.
description: 15 pages, 13 figures
A General Framework for Constructing Locally Self-Normalized Multiple-Change-Point Tests
Creators: name: Cheng, Cheuk Hin
name: Chan, Kin Wai
Publisher: name: Taylor & Francis
Year: 2023
Subjects: subject: Space Science
subject: Medicine
subject: Genetics
subject: FOS: Biological sciences
subject: Physiology
subject: Sociology
subject: FOS: Sociology
classificationCode: 69999
subject: Biological Sciences not elsewhere classified
classificationCode: 19999
subject: Mathematical Sciences not elsewhere classified
classificationCode: 110309
subject: Infectious Diseases
subject: FOS: Health sciences

description: We propose a general framework to construct self-normalized multiple-change-point tests with time series data. The only building block is a user-specified single-change-detecting statistic, which covers a large class of popular methods, including the cumulative sum process, outlier-robust rank statistics, and order statistics. The proposed test statistic does not require robust and consistent estimation of nuisance parameters, selection of bandwidth parameters, nor pre-specification of the number of change points. The finite-sample performance shows that the proposed test is size-accurate, robust against misspecification of the alternative hypothesis, and more powerful than existing methods. Case studies of the Shanghai-Hong Kong Stock Connect turnover are provided.
Magnetic activity and hot Jupiters of young Suns: the weak-line T Tauri stars V819 Tau and V830 Tau
Creators: name: Donati, JF
name: Hébrard, E
name: Hussain, G
name: Moutou, C
name: Malo, L
name: Grankin, K
name: Vidotto, AA
name: Alencar, SHP
name: Gregory, SG
name: Jardine, MM
name: Herczeg, G
name: Morin, J
name: Fares, R
name: Ménard, F
name: Bouvier, J
name: Delfosse, X
name: Doyon, R
name: Takami, M
name: Figueira, P
name: Petit, P
name: Boisse, I
name: collaboration, the MaTYSSE
Publisher: name: arXiv
Year: 2015
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri stars (wTTSs) V819 Tau and V830 Tau within the MaTYSSE programme, involving the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. At ~3 Myr, both stars dissipated their discs recently and are interesting objects for probing star and planet formation. Profile distortions and Zeeman signatures are detected in the unpolarized and circularly-polarized lines, whose rotational modulation we modelled using tomographic imaging, yielding brightness and magnetic maps for both stars. We find that the large-scale magnetic fields of V819 Tau and V830 Tau are mostly poloidal and can be approximated at large radii by 350-400 G dipoles tilted at ~30 degrees to the rotation axis. They are significantly weaker than the field of GQ Lup, an accreting classical T Tauri star (cTTS) with similar mass and age which can be used to compare the magnetic properties of wTTSs and cTTSs. The reconstructed brightness maps of both stars include cool spots and warm plages. Surface differential rotation is small, typically ~4.4x smaller than on the Sun, in agreement with previous results on wTTSs. Using our Doppler images to model the activity jitter and filter it out from the radial velocity (RV) curves, we obtain RV residuals with dispersions of 0.033 and 0.104 km/s for V819 Tau and V830 Tau respectively. RV residuals suggest that a hot Jupiter may be orbiting V830 Tau, though additional data are needed to confirm this preliminary result. We find no evidence for close-in giant planet around V819 Tau.
description: MNRAS in press (15 pages, 12 figures, 3 tables)
Generalizing intrusion detection for heterogeneous networks: A stacked-unsupervised federated learning approach
Creators: name: Bertoli, Gustavo de Carvalho
name: Junior, Lourenço Alves Pereira
name: Santos, Aldri Luiz dos
name: Saotome, Osamu
Publisher: name: arXiv
Year: 2022
Subjects: subject: Cryptography and Security (cs.CR)
subject: FOS: Computer and information sciences

description: The constantly evolving digital transformation imposes new requirements on our society. Aspects relating to reliance on the networking domain and the difficulty of achieving security by design pose a challenge today. As a result, data-centric and machine-learning approaches arose as feasible solutions for securing large networks. Although, in the network security domain, ML-based solutions face a challenge regarding the capability to generalize between different contexts. In other words, solutions based on specific network data usually do not perform satisfactorily on other networks. This paper describes the stacked-unsupervised federated learning (FL) approach to generalize on a cross-silo configuration for a flow-based network intrusion detection system (NIDS). The proposed approach we have examined comprises a deep autoencoder in conjunction with an energy flow classifier in an ensemble learning task. Our approach performs better than traditional local learning and naive cross-evaluation (training in one context and testing on another network data). Remarkably, the proposed approach demonstrates a sound performance in the case of non-iid data silos. In conjunction with an informative feature in an ensemble architecture for unsupervised learning, we advise that the proposed FL-based NIDS results in a feasible approach for generalization between heterogeneous networks. To the best of our knowledge, our proposal is the first successful approach to applying unsupervised FL on the problem of network intrusion detection generalization using flow-based data.
description: Preprint (Under revision), 35 pages. Added repository link, see https://github.com/c2dc/fl-unsup-nids
Remarkably low-energy one-dimensional fault line defects in single-layered phosphorene
Creators: name: Jang, Woosun
name: Kang, Kisung
name: Soon, Aloysius
Publisher: name: arXiv
Year: 2015
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Systematic engineering of atomic-scale low-dimensional defects in two-dimensional nanomaterials is a promising way to modulate the electronic properties of these nanomaterials. Defects at interfaces such as grain boundaries and line defects can often be detrimental to technologically important nanodevice operations and thus a fundamental understanding of how such one-dimensional defects may have an influence on its physio-chemical properties is pivotal to optimizing their device performance. Of late, two-dimensional phosphorene has attracted much attention due to its high carrier mobility and good mechanical flexibility. In this study, using density-functional theory, we investigate the temperature-dependent energetics and electronic structure of a single-layered phosphorene with various fault line defects. We have generated different line defect models based on a fault method, rather than the conventional rotation method. This has allowed us to study and identify new low-energy line defects, and we show how these low-energy line defects could well modulate the electronic band gap energies of single-layered two-dimensional phosphorene -- offering a range of metallic to semiconducting properties in these newly proposed low-energy line defects in phosphorene.
description: 16 pages, 7 figures (including TOC), Accepted in Nanoscale (RSC)
MAiVAR: Multimodal Audio-Image and Video Action Recognizer
Creators: name: Shaikh, Muhammad Bilal
name: Chai, Douglas
name: Islam, Syed Mohammed Shamsul
name: Akhtar, Naveed
Publisher: name: arXiv
Year: 2022
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences
subject: I.2.10; I.5.4; I.5.2

description: Currently, action recognition is predominately performed on video data as processed by CNNs. We investigate if the representation process of CNNs can also be leveraged for multimodal action recognition by incorporating image-based audio representations of actions in a task. To this end, we propose Multimodal Audio-Image and Video Action Recognizer (MAiVAR), a CNN-based audio-image to video fusion model that accounts for video and audio modalities to achieve superior action recognition performance. MAiVAR extracts meaningful image representations of audio and fuses it with video representation to achieve better performance as compared to both modalities individually on a large-scale action recognition dataset.
description: Peer reviewed & accepted at IEEE VCIP 2022 (http://www.vcip2022.org/)
Quantum noise spectroscopy as an incoherent imaging problem
Creators: name: Tsang, Mankei
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: I point out the mathematical correspondence between an incoherent imaging model proposed by my group in the study of quantum-inspired superresolution [Tsang, Nair, and Lu, Physical Review X 6, 031033 (2016)] and a noise spectroscopy model also proposed by us [Tsang and Nair, Physical Review A 86, 042115 (2012); Ng et al., Physical Review A 93, 042121 (2016)]. Both can be regarded as random displacement models, where the probability measure for the random displacement depends on unknown parameters. The spatial-mode demultiplexing (SPADE) method proposed for imaging is analogous to the spectral photon counting method proposed in Ng et al. (2016) for optical phase noise spectroscopy -- Both methods are discrete-variable measurements that are superior to direct displacement measurements (direct imaging or homodyne detection) and can achieve the respective quantum limits. Inspired by SPADE, I propose a modification of spectral photon counting when the input field is squeezed -- simply unsqueeze the output field before spectral photon counting. I show that this method is quantum-optimal and far superior to homodyne detection for both parameter estimation and detection, thus solving the open problems in Tsang and Nair (2012) and Ng et al. (2016).
description: 10 pages, 4 figures. v3: extended; accepted version
Unconventional Resistivity Scaling in Topological Semimetal CoSi
Creators: name: Lien, Shang-Wei
name: Garate, Ion
name: Bajpai, Utkarsh
name: Huang, Cheng-Yi
name: Hsu, Chuang-Han
name: Tu, Yi-Hsin
name: Lanzillo, Nicholas A.
name: Bansil, Arun
name: Chang, Tay-Rong
name: Liang, Gengchiau
name: Lin, Hsin
name: Chen, Ching-Tzu
Publisher: name: arXiv
Year: 2022
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Nontrivial band topologies in semimetals lead to robust surface states that can contribute dominantly to the total conduction. This may result in reduced resistivity with decreasing feature size contrary to conventional metals, which may highly impact the semiconductor industry. Here we study the resistivity scaling of a representative topological semimetal CoSi using realistic band structures and Green's function methods. We show that there exists a critical thickness d_c dividing different scaling trends. Above d_c, when the defect density is low such that surface conduction dominates, resistivity reduces with decreasing thickness; when the defect density is high such that bulk conduction dominates, resistivity increases in as conventional metals. Below d_c, the persistent remnants of the surface states give rise to decreasing resistivity down to the ultrathin limit, unlike in topological insulators. The observed CoSi scaling can apply to broad classes of topological semimetals, providing guidelines for materials screening and engineering. Our study shows that topological semimetals bear the potential of overcoming the resistivity scaling challenges in back-end-of-line interconnect applications.
Quantum detector tomography applied to the human visual system: a feasibility study
Creators: name: van der Reep, T. H. A.
name: Molenaar, D.
name: Löffler, W.
name: Pinto, Y.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Physics (quant-ph)
subject: Neurons and Cognition (q-bio.NC)
subject: Applications (stat.AP)
subject: FOS: Physical sciences
subject: FOS: Biological sciences
subject: FOS: Computer and information sciences

description: We show that quantum detector tomography can be applied to the human visual system to explore human perception of photon number states. In detector tomography, instead of using very hard to produce photon number states, the response of a detector to light pulses with known photon statistics of varying intensity is recorded, and a model is fitted to the experimental outcomes thereby inferring the detector's photon number state response. Generally, light pulses containing a Poisson-distributed number of photons are utilised, which are very easy to produce in the lab. This technique has not been explored to study the human visual system before, because it usually requires a very large number of repetitions not suitable for experiments on humans. Yet, in the present study we show that detector tomography is feasible for human experiments. Assuming a simple model for this accuracy, the results of our simulations show that detector tomography is able to reconstruct the model using Bayesian inference with as little as $5000$ trials. We then optimize the experimental parameters in order to maximise the probability of showing that the single-photon accuracy is above chance. As such, our study opens the road to study human perception on quantum level.
description: 22 pages, 15 figures (excluding subfigures). Accepted version
Multi-band character revealed from Weak-antilocalization effect in Platinum thin films
Creators: name: Jana, Subhadip
name: Senapati, T.
name: Senapati, K.
name: Samal, D.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: Platinum (Pt) has been very much used for spin-charge conversion in spintronics research due to it's large intrinsic spin-orbit interaction. Magnetoconductance originated from weak-antilocalization effect in quantum interference regime is used as a powerful tool to obtain the microscopic information of spin-orbit interaction and coherence phase breaking scattering process among itinerant electrons. To acquire the knowledge of different types of scattering processes, we have performed magnetoconductance study on Pt thin films which manifests multi-band (multi-channel) conduction. An extensive analysis of quantum interference originated weak-antilocalization effect reveals the existence of strong (weak) inter-band scattering between two similar (different) orbitals. Coherence phase breaking lengths ($l_ϕ$) and their temperature dependence are found to be significantly different for these two conducting bands. The observed effects are consistent with theoretical predication that there exist three Fermi-sheets with one $s$ and two $d$ orbital character. This study provides the evidence of two independent non-similar conducting channels and presence of anisotropic spin-orbit interaction along with $e$-$e$ correlation in Pt thin films.
description: 9 pages, 9 figure
Spatial and Temporal Dynamics of Urban Wetlands in an Indian Megacity over the Past 50 Years
Creators: name: Brinkmann, Katja
name: Hoffmann, Ellen M.
name: Buerkert, Andreas
Publisher: name: Universität Kassel
Year: 2020
Subjects: subject: lakes
subject: Bengaluru
subject: rural-urban gradient
subject: object-based classification
subject: land cover changes
subject: urbanization
subject: 630
subject: 710

description: Gefördert durch den Publikationsfonds der Universität Kassel
Assembly bias in the local PNG halo bias and its implication for $f_{\rm NL}$ constraints
Creators: name: Lazeyras, Titouan
name: Barreira, Alexandre
name: Schmidt, Fabian
name: Desjacques, Vincent
Publisher: name: arXiv
Year: 2022
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We use $N$-body simulations to study halo assembly bias (i.e., the dependence of halo clustering on properties beyond total mass) in the density and primordial non-Gaussianity (PNG) linear bias parameters $b_1$ and $b_ϕ$, respectively. We consider concentration, spin and sphericity as secondary halo properties, for which we find a clear detection of assembly bias for $b_1$ and $b_ϕ$. At fixed total mass, halo spin and sphericity impact $b_1$ and $b_ϕ$ in a similar manner, roughly preserving the shape of the linear $b_ϕ(b_1)$ relation satisfied by the global halo population. Halo concentration, however, drives $b_1$ and $b_ϕ$ in opposite directions. This induces significant changes to the $b_ϕ(b_1)$ relation, with higher concentration halos having higher amplitude of $b_ϕ(b_1)$. For $z=0.5$ and $b_1 \approx 2$ in particular, the population comprising either all halos, those with the $33\%$ lowest or those with the $33\%$ highest concentrations have a PNG bias of $b_ϕ\approx 3$, $b_ϕ\approx -1$ and $b_ϕ\approx 9$, respectively. Varying the halo concentration can make $b_ϕ$ very small and even change its sign. These results have important ramifications for galaxy clustering constraints of the local PNG parameter $f_{\rm NL}$ that assume fixed forms for the $b_ϕ(b_1)$ relation. We illustrate the significant impact of halo assembly bias in actual data using the BOSS DR12 galaxy power spectrum: assuming that BOSS galaxies are representative of all halos, the $33\%$ lowest or the $33\%$ highest concentration halos yields $σ_{f_{\rm NL}} = 44, 165, 19$, respectively. Our results suggest taking host halo concentration into account in galaxy selection strategies to maximize the signal-to-noise on $f_{\rm NL}$. They also motivate more simulation-based efforts to study the $b_ϕ(b_1)$ relation of halos and galaxies.
description: 21 pages, 4 figures, comments welcome; V2 minor modifications throughout, published in JCAP
Explainability in subgraphs-enhanced Graph Neural Networks
Creators: name: Guerra, Michele
name: Spinelli, Indro
name: Scardapane, Simone
name: Bianchi, Filippo Maria
Publisher: name: arXiv
Year: 2022
Subjects: subject: Machine Learning (cs.LG)
subject: FOS: Computer and information sciences

description: Recently, subgraphs-enhanced Graph Neural Networks (SGNNs) have been introduced to enhance the expressive power of Graph Neural Networks (GNNs), which was proved to be not higher than the 1-dimensional Weisfeiler-Leman isomorphism test. The new paradigm suggests using subgraphs extracted from the input graph to improve the model's expressiveness, but the additional complexity exacerbates an already challenging problem in GNNs: explaining their predictions. In this work, we adapt PGExplainer, one of the most recent explainers for GNNs, to SGNNs. The proposed explainer accounts for the contribution of all the different subgraphs and can produce a meaningful explanation that humans can interpret. The experiments that we performed both on real and synthetic datasets show that our framework is successful in explaining the decision process of an SGNN on graph classification tasks.
description: The source code implementing our workflow is publicly available online at https://github.com/MicheleUIT/Explaining_SGNN
Spatial patterns of urbanising landscapes in the North Indian Punjab show features predicted by fractal theory
Creators: name: Nguyen, Thanh Thi
name: Hoffmann, Ellen M.
name: Buerkert, Andreas
Publisher: name: Universität Kassel
Year: 2022
Subjects: subject: 300
subject: 630
subject: Punjab (Indien)
subject: Verstädterung
subject: Siedlung
subject: Landschaft
subject: Nachhaltigkeit
subject: Fraktalgeometrie
subject: Stadtentwicklung
subject: Stadtplanung
subject: Sierpiński-Teppich

description: Gefördert durch den Publikationsfonds der Universität Kassel
Constraints on the hosts of UHECR accelerators
Creators: name: Muzio, Marco Stein
name: Farrar, Glennys R.
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: Interactions of ultrahigh energy cosmic rays in the surroundings of their accelerators can naturally explain the observed spectrum and composition of UHECRs, including the abundance of protons below the ankle. We show that astrophysical properties of the UHECR source environment such as the temperature, size, and magnetic field can be constrained by UHECR and neutrino data. Applying this to candidate sources with a simple structure shows that starburst galaxies are consistent with these constraints, but galaxy clusters may be in tension with them. For multi-component systems like AGNs and GRBs the results are indicative but customized analysis is needed for definitive conclusions.