cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Leveraging Ensembles and Self-Supervised Learning for Fully-Unsupervised Person Re-Identification and Text Authorship Attribution
Creators: name: Bertocco, Gabriel
name: Theophilo, Antônio
name: Andaló, Fernanda
name: Rocha, Anderson
Publisher: name: arXiv
Year: 2022
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: Learning from fully-unlabeled data is challenging in Multimedia Forensics problems, such as Person Re-Identification and Text Authorship Attribution. Recent self-supervised learning methods have shown to be effective when dealing with fully-unlabeled data in cases where the underlying classes have significant semantic differences, as intra-class distances are substantially lower than inter-class distances. However, this is not the case for forensic applications in which classes have similar semantics and the training and test sets have disjoint identities. General self-supervised learning methods might fail to learn discriminative features in this scenario, thus requiring more robust strategies. We propose a strategy to tackle Person Re-Identification and Text Authorship Attribution by enabling learning from unlabeled data even when samples from different classes are not prominently diverse. We propose a novel ensemble-based clustering strategy whereby clusters derived from different configurations are combined to generate a better grouping for the data samples in a fully-unsupervised way. This strategy allows clusters with different densities and higher variability to emerge, reducing intra-class discrepancies without requiring the burden of finding an optimal configuration per dataset. We also consider different Convolutional Neural Networks for feature extraction and subsequent distance computations between samples. We refine these distances by incorporating context and grouping them to capture complementary information. Our method is robust across both tasks, with different data modalities, and outperforms state-of-the-art methods with a fully-unsupervised solution without any labeling or human intervention.
description: This work has been accepted for publication in the IEEE Transactions on Information Forensics and Security
Proxima Centauri reloaded: Unravelling the stellar noise in radial velocities
Creators: name: Damasso, M.
name: Del Sordo, F.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: The detection and characterisation of Earth-like planets with Doppler signals of the order of 1 m/s currently represent one of the greatest challenge for extrasolar-planet hunters. As results for such findings are often controversial, it is desirable to provide independent confirmations of the discoveries. Testing different models for the suppression of non-Keplerian stellar signals usually plaguing radial velocity data is essential to ensuring findings are robust and reproducible. Using an alternative treatment of the stellar noise to that discussed in the discovery paper, we re-analyse the radial velocity dataset that led to the detection of a candidate terrestrial planet orbiting the star Proxima Centauri. We aim to confirm the existence of this outstanding planet, and test the existence of a second planetary signal. Our technique jointly modelled Keplerian signals and residual correlated signals in radial velocities using Gaussian processes. We analysed only radial velocity measurements without including other ancillary data in the fitting procedure. In a second step, we have compared our outputs with results coming from photometry, to provide a consistent physical interpretation. Our analysis was performed in a Bayesian framework to quantify the robustness of our findings. We show that the correlated noise can be successfully modelled as a Gaussian process regression, and contains a periodic term modulated on the stellar rotation period and characterised by an evolutionary timescale of the order of one year. Both findings appear to be robust when compared with results obtained from archival photometry, thus providing a reliable description of the noise properties. We confirm the existence of a coherent signal described by a Keplerian orbit equation that can be attributed to the planet Proxima b [...]
description: Times of inferior conjunction were re-calculated to closer Epochs. Few typos corrected
Learning Similarity Metrics for Volumetric Simulations with Multiscale CNNs
Creators: name: Kohl, Georg
name: Chen, Li-Wei
name: Thuerey, Nils
Publisher: name: arXiv
Year: 2022
Subjects: subject: Machine Learning (cs.LG)
subject: Data Analysis, Statistics and Probability (physics.data-an)
subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Computer and information sciences
subject: FOS: Physical sciences

description: Simulations that produce three-dimensional data are ubiquitous in science, ranging from fluid flows to plasma physics. We propose a similarity model based on entropy, which allows for the creation of physically meaningful ground truth distances for the similarity assessment of scalar and vectorial data, produced from transport and motion-based simulations. Utilizing two data acquisition methods derived from this model, we create collections of fields from numerical PDE solvers and existing simulation data repositories. Furthermore, a multiscale CNN architecture that computes a volumetric similarity metric (VolSiM) is proposed. To the best of our knowledge this is the first learning method inherently designed to address the challenges arising for the similarity assessment of high-dimensional simulation data. Additionally, the tradeoff between a large batch size and an accurate correlation computation for correlation-based loss functions is investigated, and the metric's invariance with respect to rotation and scale operations is analyzed. Finally, the robustness and generalization of VolSiM is evaluated on a large range of test data, as well as a particularly challenging turbulence case study, that is close to potential real-world applications.
description: Published at AAAI 2023, source code available at https://github.com/tum-pbs/VOLSIM and further information at https://ge.in.tum.de/publications/2022-volsim-kohl
A scoping review of return-to-work interventions for people with acquired physical disabilities
Creators: name: Zainal, Mohamad Nizar Bin
Publisher: name: OSF Registries
Year: 2024
Subjects: subject: Medicine and Health Sciences
subject: Social and Behavioral Sciences

description: Our proposed scoping review aims to map the literature on existing vocational rehabilitation (VR) programs that support adults with acquired physical disabilities in their return-to-work (RTW) process.
Measurement of antiproton annihilation on Cu, Ag and Au with emulsion films
Creators: name: Aghion, S.
name: Amsler, C.
name: Ariga, A.
name: Ariga, T.
name: Bonomi, G.
name: Braunig, P.
name: Brusa, R. S.
name: Cabaret, L.
name: Caccia, M.
name: Caravita, R.
name: Castelli, F.
name: Cerchiari, G.
name: Comparat, D.
name: Consolati, G.
name: Demetrio, A.
name: Di Noto, L.
name: Doser, M.
name: Ereditato, A.
name: Evans, C.
name: Ferragut, R.
name: Fesel, J.
name: Fontana, A.
name: Gerber, S.
name: Giammarchi, M.
name: Gligorova, A.
name: Guatieri, F.
name: Haider, S.
name: Hinterberger, A.
name: Holmestad, H.
name: Huse, T.
name: Kawada, J.
name: Kellerbauer, A.
name: Kimura, M.
name: Krasnicky, D.
name: Lagomarsino, V.
name: Lansonneur, P.
name: Lebrun, P.
name: Malbrunot, C.
name: Mariazzi, S.
name: Matveev, V.
name: Mazzotta, Z.
name: Muller, S. R.
name: Nebbia, G.
name: Nedelec, P.
name: Oberthaler, M.
name: Pacifico, N.
name: Pagano, D.
name: Penasa, L.
name: Petracek, V.
name: Pistillo, C.
name: Prelz, F.
name: Prevedelli, M.
name: Ravelli, L.
name: Rienaecker, B.
name: Rohne, O. M.
name: Rotondi, A.
name: Sacerdoti, M.
name: Sandaker, H.
name: Santoro, R.
name: Scampoli, P.
name: Simon, M.
name: Smestad, L.
name: Sorrentino, F.
name: Testera, G.
name: Tietje, I. C.
name: Vamosi, S.
name: Vladymyrov, M.
name: Widmann, E.
name: Yzombard, P.
name: Zimmer, C.
name: Zmeskal, J.
name: Zurlo, N.
Publisher: name: arXiv
Year: 2017
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: The characteristics of low energy antiproton annihilations on nuclei (e.g. hadronization and product multiplicities) are not well known, and Monte Carlo simulation packages that use different models provide different descriptions of the annihilation events. In this study, we measured the particle multiplicities resulting from antiproton annihilations on nuclei. The results were compared with predictions obtained using different models in the simulation tools GEANT4 and FLUKA. For this study, we exposed thin targets (Cu, Ag and Au) to a very low energy antiproton beam from CERN's Antiproton Decelerator, exploiting the secondary beamline available in the AEgIS experimental zone. The antiproton annihilation products were detected using emulsion films developed at the Laboratory of High Energy Physics in Bern, where they were analysed at the automatic microscope facility. The fragment multiplicity measured in this study is in good agreement with results obtained with FLUKA simulations for both minimally and heavily ionizing particles.
Performance Analysis of Intelligent Reflecting Surface Assisted Opportunistic Communications
Creators: name: Yashvanth, L.
name: Murthy, Chandra R.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Information Theory (cs.IT)
subject: Signal Processing (eess.SP)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: Intelligent reflecting surfaces (IRSs) are a promising technology for enhancing coverage and spectral efficiency, both in the sub-6 GHz and the millimeter wave (mmWave) bands. Existing approaches to leverage the benefits of IRS involve the use of a resource-intensive channel estimation step followed by a computationally expensive algorithm to optimize the reflection coefficients at the IRS. In this work, focusing on the sub-6 GHz band of communications, we present and analyze several alternative schemes, where the phase configuration of the IRS is randomized and multi-user diversity is exploited to opportunistically select the best user at each point in time for data transmission. We show that the throughput of an IRS assisted opportunistic communication (OC) system asymptotically converges to the optimal beamforming-based throughput under fair allocation of resources, as the number of users gets large. We also introduce schemes that enhance the rate of convergence of the OC rate to the beamforming rate with the number of users. For all the proposed schemes, we derive the scaling law of the throughput in terms of the system parameters, as the number of users gets large. Following this, we extend the setup to wideband channels via an orthogonal frequency division multiplexing (OFDM) system and discuss two OC schemes in an IRS assisted setting that clearly elucidate the superior performance that IRS aided OC systems can offer over conventional systems, at very low implementation cost and complexity.
description: 17 pages, 9 figures
Criticality and Phase Diagram of Quantum Long-Range $\text{O(N)}$ models
Creators: name: Defenu, Nicolo
name: Trombettoni, Andrea
name: Ruffo, Stefano
Publisher: name: arXiv
Year: 2017
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: FOS: Physical sciences

description: Several recent experiments in atomic, molecular and optical systems motivated a huge interest in the study of quantum long-range %spin systems. Our goal in this paper is to present a general description of their critical behavior and phases, devising a treatment valid in $d$ dimensions, with an exponent $d+σ$ for the power-law decay of the couplings in the presence of an $O(N)$ symmetry. By introducing a convenient ansatz for the effective action, we determine the phase diagram for the $N$-component quantum rotor model with long-range interactions, with $N=1$ corresponding to the Ising model. The phase diagram in the $σ-d$ plane shows a non trivial dependence on $σ$. As a consequence of the fact that the model is quantum, the correlation functions are anisotropic in the spatial and time coordinates for $σ$ smaller than a critical value and in this region the isotropy is not restored even at criticality. Results for the correlation length exponent $ν$, the dynamical critical exponent $z$ and a comparison with numerical findings for them are presented.
description: 10 Pages, 7 figures
Thermodynamic bounds on the ultra- and infra-affinity of Hsp70 for its substrates
Creators: name: Nguyen, Basile
name: Hartich, David
name: Seifert, Udo
name: Rios, Paolo De Los
Publisher: name: arXiv
Year: 2017
Subjects: subject: Biomolecules (q-bio.BM)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Biological Physics (physics.bio-ph)
subject: FOS: Biological sciences
subject: FOS: Physical sciences

description: The 70 kDa Heat Shock Proteins Hsp70 have several essential functions in living systems, such as protecting cells against protein aggregation, assisting protein folding, remodeling protein complexes and driving the translocation into organelles. These functions require high affinity for non-specific amino-acid sequences that are ubiquitous in proteins. It has been recently shown that this high affinity, called ultra-affinity, depends on a process driven out of equilibrium by ATP hydrolysis. Here we establish the thermodynamic bounds for ultra-affinity, and further show that the same reaction scheme can in principle be used both to strengthen and to weaken affinities (leading in this case to infra-affinity). We show that cofactors are essential to achieve affinity beyond the equilibrium range. Finally, biological implications are discussed.
description: 14 pages, 5 figures
title: Primary sternal Ewing’s sarcoma with lung and adrenal metastasis
Creators: name: Sebastian, Stallon
Publisher: name: EURORAD
Year: 2023
Subjects: subject: Musculoskeletal system
subject: Musculoskeletal bone
subject: Musculoskeletal soft tissue
subject: Paediatric
subject: Conventional radiography
subject: CT
subject: Biopsy
subject: Metastases
subject: Multidisciplinary cancer care
subject: Clinical Cases

description: Clinical History: A thirteen-year-old boy presented with progressive painful swelling over the centre of the chest for 3 months. His vitals were stable on presentation at the hospital. Examination confirmed a firm tender swelling over anterior chest covering the sternum. A chest radiograph followed by a contrast-enhanced CT of the chest and upper abdomen was done.

description: 13 years, male
Automated differential equation solver based on the parametric approximation optimization
Creators: name: Hvatov, Alexander
name: Tikhonova, Tatiana
Publisher: name: arXiv
Year: 2022
Subjects: subject: Numerical Analysis (math.NA)
subject: Machine Learning (cs.LG)
subject: FOS: Mathematics
subject: FOS: Computer and information sciences

description: The numerical methods for differential equation solution allow obtaining a discrete field that converges towards the solution if the method is applied to the correct problem. Nevertheless, the numerical methods have the restricted class of the equations, on which the convergence with a given parameter set or range is proved. Only a few "cheap and dirty" numerical methods converge on a wide class of equations without parameter tuning with the lower approximation order price. The article presents a method that uses an optimization algorithm to obtain a solution using the parameterized approximation. The result may not be as precise as an expert one. However, it allows solving the wide class of equations in an automated manner without the algorithm's parameters change.
Nonnegative scalar curvature on manifolds with at least two ends
Creators: name: Cecchini, Simone
name: Räde, Daniel
name: Zeidler, Rudolf
Publisher: name: arXiv
Year: 2022
Subjects: subject: Differential Geometry (math.DG)
subject: Geometric Topology (math.GT)
subject: FOS: Mathematics
subject: 53C21, 53C23 (Primary) 53C24, 57R65, 57R90 (Secondary)

description: Let $M$ be an orientable connected $n$-dimensional manifold with $n\in\{6,7\}$ and let $Y\subset M$ be a two-sided closed connected incompressible hypersurface which does not admit a metric of positive scalar curvature (abbreviated by psc). Moreover, suppose that the universal covers of $M$ and $Y$ are either both spin or both non-spin. Using Gromov's $μ$-bubbles, we show that $M$ does not admit a complete metric of psc. We provide an example showing that the spin/non-spin hypothesis cannot be dropped from the statement of this result. This answers, up to dimension $7$, a question by Gromov for a large class of cases. Furthermore, we prove a related result for submanifolds of codimension two. We deduce as special cases that, if $Y$ does not admit a metric of psc and $\dim(Y) \neq 4$, then $M := Y\times\mathbb{R}$ does not carry a complete metric of psc and $N := Y \times \mathbb{R}^2$ does not carry a complete metric of uniformly psc provided that $\dim(M) \leq 7$ and $\dim(N) \leq 7$, respectively. This solves, up to dimension $7$, a conjecture due to Rosenberg and Stolz in the case of orientable manifolds.
description: 19 pages; v2: minor improvements. To appear in J. Topol
VALUABLE Scientific Publications 1
Creators: name: LORENZEN, JAN
Publisher: name: Zenodo
Year: 2023

description: (Draft deliverable; not yet approved by the European Commission)

In the first project period, from September 2022 until the end of December 2023, one scientific publication has been issued in an open-access, peer reviewed journal, while an additional publication is currently in the finalisation process. The two publications are namely “Bioconversion of a Lignocellulosic Hydrolysate to Single Cell Oil for Biofuel Production in a Cost-Efficient Fermentation Process” (Rerop, Stellner et al. 2023) and “From diverse substrate spectrum to versatile applications – A landscape perspective on the sustainability of Cutaneotrichosporon oleaginosus lipids”.
$K_{S}^{0}-K_{L}^{0}$ asymmetries in $D$-meson decays
Creators: name: Wang, Di
name: Yu, Fu-Sheng
name: Guo, Peng-Fei
name: Jiang, Hua-Yu
Publisher: name: arXiv
Year: 2017
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences

description: The $K_{S}^{0}-K_{L}^{0}$ asymmetries in the $D$ meson decays, induced by the interference between the Cabibbo-favored and the doubly Cabibbo-suppressed amplitudes, can help to understand the dynamics of charm decays. All possible processes of two-body non-leptonic $D$ decays into one neutral kaon and another pseudoscalar or vector meson are considered. We study the $K_{S}^{0}-K_{L}^{0}$ asymmetries and the branching fractions of corresponding processes in the factorization-assisted topological-amplitude approach in which significant flavor $SU(3)$ symmetry breaking effects are included. The branching fractions of $K_{L}^{0}$ modes are predicted. It is first found that the $K_{S}^{0}-K_{L}^{0}$ asymmetries in the $D^0$-meson decays are shifted by the $D^0-\overline D^0$ mixing parameter $y_{D}\simeq0.006$, to be $0.113\pm0.001$ for all the relevant $D^{0}$ decay modes. Our results on $K_{S}^{0}-K_{L}^{0}$ asymmetries are consistent with the current data and could be tested by experiments in the future.
description: 19 pages, 1 figure. Published version in Physics Review D
VALUABLE Scientific Publications 1
Creators: name: LORENZEN, JAN
Publisher: name: Zenodo
Year: 2024

description: (Draft deliverable; not yet approved by the European Commission)

In the first project period, from September 2022 until the end of December 2023, one scientific publication has been issued in an open-access, peer reviewed journal, while an additional publication is currently in the finalisation process. The two publications are namely “Bioconversion of a Lignocellulosic Hydrolysate to Single Cell Oil for Biofuel Production in a Cost-Efficient Fermentation Process” (Rerop, Stellner et al. 2023) and “From diverse substrate spectrum to versatile applications – A landscape perspective on the sustainability of Cutaneotrichosporon oleaginosus lipids”.
Cut Moments approach in the analysis of DIS data
Creators: name: Kotlorz, D.
name: Mikhailov, S. V.
name: Teryaev, O. V.
name: Kotlorz, A.
Publisher: name: arXiv
Year: 2017
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We review the main results on the generalization of the DGLAP evolution equations within the cut Mellin moments (CMM) approach, which allows one to overcome the problem of kinematic constraints in Bjorken $x$. CMM obtained by multiple integrations as well as multiple differentiations of the original parton distribution also satisfy the DGLAP equations with the simply transformed evolution kernel. The CMM approach provides novel tools to test QCD; here we present one of them. Using appropriate classes of CMM, we construct the generalized Bjorken sum rule that allows us to determine the Bjorken sum rule value from the experimental data in a restricted kinematic range of $x$. We apply our analysis to COMPASS data on the spin structure function $g_1$.
description: 9 pages, 8 figures; updated to published version
The Origin of Deformation Induced Topological Anisotropy in Silica Glass
Creators: name: Ganisetti, Sudheer
name: Atila, Achraf
name: Guénolé, Julien
name: Prakash, Aruna
name: Horbach, Jürgen
name: Wondraczek, Lothar
name: Bitzek, Erik
Publisher: name: arXiv
Year: 2022
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Oxide glasses with a network structure are omnipresent in daily life. Often, they are regarded as isotropic materials; however, structural anisotropy can be induced through processing in mechanical fields and leads to unique materials properties. Unfortunately, due to the lack of local, atomic-scale analysis methods, the microscopic mechanisms leading to anisotropy remained elusive. Using novel analysis methods on glasses generated by molecular dynamics simulations, this paper provides a microscopic understanding of topological anisotropy in silica (SiO$_2$) glass under mechanical loads. The anisotropy observed in silica glass originates from a preferred orientation of SiO$_4$ tetrahedra at both short- and medium-range levels that can be controlled via the mode of mechanical loading. The findings elucidate the relation between the deformation protocol and the resulting anisotropic structure of the silica network (involving both persistent and transient effects), and thus provide important insight for the design of oxide glasses with tailored materials properties.
Sub-arcsecond imaging of the water emission in Arp 220
Creators: name: König, S.
name: Martín, S.
name: Muller, S.
name: Cernicharo, J.
name: Sakamoto, K.
name: Zschaechner, L. K.
name: Humphreys, E. M. L.
name: Mroczkowski, T.
name: Krips, M.
name: Galametz, M.
name: Aalto, S.
name: Vlemmings, W. H. T.
name: Ott, J.
name: Meier, D. S.
name: Fuente, A.
name: García-Burillo, S.
name: Neri, R.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Extragalactic observations of water emission can provide valuable insights into the excitation of the interstellar medium. In addition, extragalactic megamasers are powerful probes of kinematics close to active nuclei. Therefore, it is paramount to determine the true origin of the water emission, whether it is excited by processes close to an AGN or in star-forming regions. We use ALMA Band 5 science verification observations to analyse the emission of the 183 GHz water line in Arp 220 on sub-arcsecond scales, in conjunction with new ALMA Band 7 data at 325 GHz. Specifically, the nature of the process leading to the excitation of emission at these water lines is studied in this context. Supplementary 22 GHz VLA observations are used to better constrain the parameter space in the excitation modelling of the water lines. We detect 183 GHz H2O and 325 GHz water emission towards the two compact nuclei at the center of Arp 220, being brighter in Arp 220 West. The emission at these two frequencies is compared to previous single-dish data and does not show evidence of variability. The 183 and 325 GHz lines show similar spectra and kinematics, but the 22 GHz profile is significantly different in both nuclei due to a blend with an NH3 absorption line. Our findings suggest that the most likely scenario to cause the observed water emission in Arp 220 is a large number of independent masers originating from numerous star-forming regions.
description: 10 pages, 7 figures, 3 tables, accepted for publication in A&A
Vertical Distribution and Kinematics of Protoplanetary Nebulae in the Galaxy
Creators: name: Bobylev, V. V.
name: Bajkova, A. T.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: The catalogue of protoplanetary nebulae by Vickers et al. has been supplemented with the line-of-sight velocities and proper motions of their central stars from the literature. Based on an exponential density distribution, we have estimated the vertical scale height from objects with an age less than 3 Gyr belonging to the Galactic thin disk (luminosities higher than 5000 Lo) to be h=146+/-15 pc, while from a sample of older objects (luminosities lower than 5000 Lo) it is h=568+/-42 pc. We have produced a list of 147 nebulae in which there are only the line-of-sight velocities for 55 nebulae, only the proper motions for 25 nebulae, and both line-of-sight velocities and proper motions for 67 nebulae. Based on this kinematic sample, we have estimated the Galactic rotation parameters and the residual velocity dispersions of protoplanetary nebulae as a function of their age. We have established that there is a good correlation between the kinematic properties of nebulae and their separation in luminosity proposed by Vickers. Most of the nebulae are shown to be involved in the Galactic rotation, with the circular rotation velocity at the solar distance being V_0=227+/-23 km/s. The following principal semiaxes of the residual velocity dispersion ellipsoid have been found: (sigma1, sigma2, sigma3) = (47, 41, 29) km/s from a sample of young protoplanetary nebulae (with luminosities higher than 5000 Lo), (sigma1, sigma2, sigma3) = (50, 38, 28) km/s from a sample of older protoplanetary nebulae (with luminosities of 4000 Lo or 3500 Lo), and (sigma1, sigma_2, sigma3) = (91, 49, 36) km/s from a sample of halo nebulae (with luminosities of 1700 Lo).
description: 18 pages, 4 figures, 2 tabkes
Time-dependent quantum correlations in phase space
Creators: name: Krumm, Fabian
name: Vogel, Werner
name: Sperling, Jan
Publisher: name: arXiv
Year: 2017
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: General quasi-probabilities are introduced to visualize time-dependent quantum correlations of light in phase space. They are based on the generalization of the Glauber-Sudarshan P function to a time-dependent P functional [W. Vogel, Phys. Rev. Lett. 100, 013605 (2008)], which fully describes temporal correlations of radiation fields on the basis of continuous phase-space distributions. This approach is nontrivial as the P functional itself is highly singular for many quantum states and nonlinear processes. In general, it neither yields a well-behaved nor an experimentally accessible description of quantum stochastic processes. Our regularized version of this multi-time-dependent quasi-probability is a smooth function and applies to stronger divergences compared to the single-time and multi-mode scenario. The technique is used to characterize an optical parametric process with frequency mismatch. A measurement scheme, together with a sampling approach, is provided which yields direct experimental access to the regularized P functional from measured data.
description: 13 pages, 5 figures
Coherence measurements of scattered incoherent light for lensless identification of an object's location and size
Creators: name: Kondakci, H. Esat
name: Beckus, Andre
name: Halawany, Ahmed El
name: Mohammadian, Nafiseh
name: Atia, George K.
name: Abouraddy, Ayman F.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: In absence of a lens to form an image, incoherent or partially coherent light scattering off an obstructive or reflective object forms a broad intensity distribution in the far field with only feeble spatial features. We show here that measuring the complex spatial coherence function can help in the identification of the size and location of a one-dimensional object placed in the path of a partially coherent light source. The complex coherence function is measured in the far field through wavefront sampling, which is performed via dynamically reconfigurable slits implemented on a digital micromirror device (DMD). The impact of an object -- parameterized by size and location -- that either intercepts or reflects incoherent light is studied. The experimental results show that measuring the spatial coherence function as a function of the separation between two slits located symmetrically around the optical axis can identify the object transverse location and angle subtended from the detection plane (the ratio of the object width to the axial distance from the detector). The measurements are in good agreement with numerical simulations of a forward model based on Fresnel propagators. The rapid refresh rate of DMDs may enable real-time operation of such a lensless coherency imaging scheme.
description: 9 pages, 7 figures
Microwave-activated gates between a fluxonium and a transmon qubit
Creators: name: Ciani, Alessandro
name: Varbanov, Boris M.
name: Jolly, Nicolas
name: Andersen, Christian K.
name: Terhal, Barbara M.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We propose and analyze two types of microwave-activated gates between a fluxonium and a transmon qubit, namely a cross-resonance (CR) and a CPHASE gate. The large frequency difference between a transmon and a fluxonium makes the realization of a two-qubit gate challenging. For a medium-frequency fluxonium qubit, the transmon-fluxonium system allows for a cross-resonance effect mediated by the higher levels of the fluxonium over a wide range of transmon frequencies. This allows one to realize the cross-resonance gate by driving the fluxonium at the transmon frequency, mitigating typical problems of the cross-resonance gate in transmon-transmon chips related to frequency targeting and residual ZZ coupling. However, when the fundamental frequency of the fluxonium enters the low-frequency regime below 100 MHz, the cross-resonance effect decreases leading to long gate times. For this range of parameters, a fast microwave CPHASE gate can be implemented using the higher levels of the fluxonium. In both cases, we perform numerical simulations of the gate showing that a gate fidelity above 99% can be obtained with gate times between 100 and 300 ns. Next to a detailed gate analysis, we perform a study of chip yield for a surface code lattice of fluxonia and transmons interacting via the proposed cross-resonance gate. We find a much better yield as compared to a transmon-only architecture with the cross-resonance gate as native two-qubit gate.
High-Fidelity Qutrit Entangling Gates for Superconducting Circuits
Creators: name: Goss, Noah
name: Morvan, Alexis
name: Marinelli, Brian
name: Mitchell, Bradley K.
name: Nguyen, Long B.
name: Naik, Ravi K.
name: Chen, Larry
name: Jünger, Christian
name: Kreikebaum, John Mark
name: Santiago, David I.
name: Wallman, Joel J.
name: Siddiqi, Irfan
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Physics (quant-ph)
subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: Ternary quantum information processing in superconducting devices poses a promising alternative to its more popular binary counterpart through larger, more connected computational spaces and proposed advantages in quantum simulation and error correction. Although generally operated as qubits, transmons have readily addressable higher levels, making them natural candidates for operation as quantum three-level systems (qutrits). Recent works in transmon devices have realized high fidelity single qutrit operation. Nonetheless, effectively engineering a high-fidelity two-qutrit entanglement remains a central challenge for realizing qutrit processing in a transmon device. In this work, we apply the differential AC Stark shift to implement a flexible, microwave-activated, and dynamic cross-Kerr entanglement between two fixed-frequency transmon qutrits, expanding on work performed for the $ZZ$ interaction with transmon qubits. We then use this interaction to engineer efficient, high-fidelity qutrit CZ$^†$ and CZ gates, with estimated process fidelities of 97.3(1)% and 95.2(3)% respectively, a significant step forward for operating qutrits on a multi-transmon device.
description: 8 pages (+19 pages in supplement) 5 Figures (+7 in supplement)
Influence of uncertainty estimation techniques on false-positive reduction in liver lesion detection
Creators: name: Bhat, Ishaan
name: Pluim, Josien P. W.
name: Viergever, Max A.
name: Kuijf, Hugo J.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Image and Video Processing (eess.IV)
subject: Computer Vision and Pattern Recognition (cs.CV)
subject: Machine Learning (cs.LG)
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Computer and information sciences

description: Deep learning techniques show success in detecting objects in medical images, but still suffer from false-positive predictions that may hinder accurate diagnosis. The estimated uncertainty of the neural network output has been used to flag incorrect predictions. We study the role played by features computed from neural network uncertainty estimates and shape-based features computed from binary predictions in reducing false positives in liver lesion detection by developing a classification-based post-processing step for different uncertainty estimation methods. We demonstrate an improvement in the lesion detection performance of the neural network (with respect to F1-score) for all uncertainty estimation methods on two datasets, comprising abdominal MR and CT images, respectively. We show that features computed from neural network uncertainty estimates tend not to contribute much toward reducing false positives. Our results show that factors like class imbalance (true over false positive ratio) and shape-based features extracted from uncertainty maps play an important role in distinguishing false positive from true positive predictions. Our code can be found at https://github.com/ishaanb92/FPCPipeline.
description: Accepted for publication in the Journal of Machine Learning for Biomedical Imaging (MELBA)
Relation connecting thermodynamics and transport of atomic unitary Fermi superfluids
Creators: name: Guo, Hao
name: Cai, Weimin
name: He, Yan
name: Chien, Chih-Chun
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: Superconductivity (cond-mat.supr-con)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: The shear viscosity has been shown to be equal to the product of pressure and relaxation time in normal scale-invariant fluids, but the presence of superfluidity at low temperatures can alter the relation. By using the mean-field BCS-Leggett theory with a gauge-invariant linear response theory for unitary Fermi superfluids, we present an explicit relation between thermodynamic quantities, including the pressure and chemical potential, and transport coefficients, including the shear viscosity, superfluid density, and anomalous shear viscosity from momentum transfer via Cooper pairs. The relation is modified when pairing fluctuations associated with noncondensed Cooper pairs are considered. Within a pairing fluctuation theory consistent with the BCS-Leggett ground state, we found an approximate relation for unitary Fermi superfluids. The exact mean-field relation and the approximate one with pairing flucutaions advance our understanding of relations between equilibrium and transport quantities in superfluids, and they help determine or constrain quantities which can be otherwise difficult to measure.
description: 10 pages, 3 figures
Flow correlations from a hydrodynamics model with dynamical freeze-out and initial conditions based on perturbative QCD and saturation
Creators: name: Hirvonen, H.
name: Eskola, K. J.
name: Niemi, H.
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: We extend the applicability of the hydrodynamics, perturbative QCD and saturation -based EKRT (Eskola-Kajantie-Ruuskanen-Tuominen) framework for ultrarelativistic heavy-ion collisions to peripheral collisions by introducing dynamical freeze-out conditions. As a new ingredient compared to the previous EKRT computations we also introduce a non-zero bulk viscosity. We compute various hadronic observables and flow correlations, including normalized symmetric cumulants, mixed harmonic cumulants and flow-transverse momentum correlations, and compare them against measurements from the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC). We demonstrate that the inclusion of the dynamical freeze-out and bulk viscosity allows a better description of the measured flow coefficients in peripheral collisions and enables the use of an extended centrality range when constraining the properties of QCD matter in the future.
description: 22 pages, 17 figures
Identifying Consistent Statements about Numerical Data with Dispersion-Corrected Subgroup Discovery
Creators: name: Boley, Mario
name: Goldsmith, Bryan R.
name: Ghiringhelli, Luca M.
name: Vreeken, Jilles
Publisher: name: arXiv
Year: 2017
Subjects: subject: Artificial Intelligence (cs.AI)
subject: Databases (cs.DB)
subject: FOS: Computer and information sciences

description: Existing algorithms for subgroup discovery with numerical targets do not optimize the error or target variable dispersion of the groups they find. This often leads to unreliable or inconsistent statements about the data, rendering practical applications, especially in scientific domains, futile. Therefore, we here extend the optimistic estimator framework for optimal subgroup discovery to a new class of objective functions: we show how tight estimators can be computed efficiently for all functions that are determined by subgroup size (non-decreasing dependence), the subgroup median value, and a dispersion measure around the median (non-increasing dependence). In the important special case when dispersion is measured using the average absolute deviation from the median, this novel approach yields a linear time algorithm. Empirical evaluation on a wide range of datasets shows that, when used within branch-and-bound search, this approach is highly efficient and indeed discovers subgroups with much smaller errors.
description: significance of empirical results tested; additional illustrations; table of used notations
Springback effect and structural features during the drying of silica aerogels tracked by in-situ synchrotron X-ray scattering
Creators: name: Zemke, Fabian
name: Scoppola, Ernesto
name: Simon, Ulla
name: Bekheet, Maged F.
name: Wagermaier, Wolfgang
name: Gurlo, Aleksander
Publisher: name: Technische Universität Berlin
Year: 2022
Subjects: subject: 620 Ingenieurwissenschaften und zugeordnete Tätigkeiten
subject: characterization and analytical techniques
subject: design, synthesis and processing
subject: nanoscale materials

description: The springback effect during ambient pressure drying of aerogels is an interesting structural phenomenon, consisting of a severe shrinkage followed by almost complete re-expansion. The drying of gels causes shrinkage, whereas re-expansion is believed to be linked to repelling forces on the nanoscale. A multi-scale structural characterization of this significant volume change is key in controlling aerogel processing and properties. In this work, hydrophobic, monolithic silica aerogels with high specific surface areas were synthesized by modification with trimethylchlorosilane and ambient pressure drying. Here, we report a multi-method approach focusing on in-situ X-ray scattering to observe alterations of the nanostructured material during the drying of surface-modified and unmodified silica gels. Both show a porous fractal nanostructure, which partially collapses during drying and only recovers in surface-modified samples during the springback effect. Distinct changes of the X-ray scattering data were reproducibly associated with the shrinkage, re-expansion and drying of the gel network. Our findings may contribute to tailor aerogels with specific functionality, as the springback effect has a direct influence on properties (e.g., porosity, pore size distribution), which is directly affected by the degree of re-expansion.
A simple algorithm for expanding a power series as a continued fraction
Creators: name: Sokal, Alan D.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Combinatorics (math.CO)
subject: Classical Analysis and ODEs (math.CA)
subject: Complex Variables (math.CV)
subject: FOS: Mathematics
subject: 30B70 (Primary), 05A10, 05A15, 05A19 (Secondary)

description: I present and discuss an extremely simple algorithm for expanding a formal power series as a continued fraction. This algorithm, which goes back to Euler (1746) and Viscovatov (1805), deserves to be better known. I also discuss the connection of this algorithm with the work of Gauss (1812), Stieltjes (1889), Rogers (1907) and Ramanujan, and a combinatorial interpretation based on the work of Flajolet (1980).
description: LaTeX2e, 48 pages. Version 2 contains a few additional historical remarks, and adds a new Remark 4 at the end of Section 10. To be published in Expositiones Mathematicae
1.5 $μ$m lasers with sub 10 mHz linewidth
Creators: name: Matei, D. G.
name: Legero, T.
name: Häfner, S.
name: Grebing, C.
name: Weyrich, R.
name: Zhang, W.
name: Sonderhouse, L.
name: Robinson, J. M.
name: Ye, J.
name: Riehle, F.
name: Sterr, U.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Instrumentation and Detectors (physics.ins-det)
subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: We report on two ultrastable lasers each stabilized to independent silicon Fabry-Pérot cavities operated at 124 K. The fractional frequency instability of each laser is completely determined by the fundamental thermal Brownian noise of the mirror coatings with a flicker noise floor of $4 \times 10^{-17}$ for integration times between 0.8 s and a few tens of seconds. We rigorously treat the notorious divergencies encountered with the associated flicker frequency noise and derive methods to relate this noise to observable and practically relevant linewidths and coherence times. The individual laser linewidth obtained from the phase noise spectrum or the direct beat note between the two lasers can be as small as 5 mHz at 194 THz. From the measured phase evolution between the two laser fields we derive usable phase coherence times for different applications of 11 s and 60 s.
Origin of the Springback Effect in Ambient-Pressure-Dried Silica Aerogels: The Effect of Surface Silylation
Creators: name: Zemke, Fabian
name: Gonthier, Julien
name: Scoppola, Ernesto
name: Simon, Ulla
name: Bekheet, Maged F.
name: Wagermaier, Wolfgang
name: Gurlo, Aleksander
Publisher: name: Technische Universität Berlin
Year: 2023
Subjects: subject: 500 Naturwissenschaften und Mathematik::540 Chemie::540 Chemie und zugeordnete Wissenschaften
subject: aerogel
subject: xerogel
subject: springback effect
subject: silica
subject: silylation
subject: ambient pressure drying
subject: trimethylchlorosilane
subject: triethylchlorosilane
subject: hexamethyldisilazane

description: Ambient pressure drying (APD) can prospectively reduce the costs of aerogel fabrication and processing. APD relies solely on preventing shrinkage or making it reversible. The latter, i.e., the aerogel re-expansion after drying (so-called springback effect—SBE), needs to be controlled for reproducible aerogel fabrication by APD. This can be achieved by an appropriate surface functionalization of aerogel materials (e.g., SiO2). This work addresses the fabrication of monolithic SiO2 aerogels and xerogels by APD. The effect of several silylation agents, i.e., trimethylchlorosilane, triethylchlorosilane, and hexamethyldisilazane on the SBE is studied in detail, applying several complementary experimental techniques, allowing the evaluation of the macroscopic and microscopic morphology as well as the composition of SiO2 aerogels. Here, we show that some physical properties, e.g., the bulk density, the macroscopic structure, and pore sizes/volumes, were significantly affected by the re-expansion. However, silylation did not necessarily lead to full re-expansion. Therefore, similarities in the molecular composition could not be equated to similarities in the SBE. The influences of steric hindrance and reactivity are discussed. The impact of silylation is crucial in tailoring the SBE and, as a result, the APD of monolithic aerogels.
Search for weak M1 transitions in $^{48}$Ca with inelastic proton scattering
Creators: name: Mathy, M.
name: Birkhan, J.
name: Matsubara, H.
name: von Neumann-Cosel, P.
name: Pietralla, N.
name: Ponomarev, V. Yu.
name: Richter, A.
name: Tamii, A.
Publisher: name: arXiv
Year: 2017
Subjects: subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences

description: The spinflip M1 resonance in the doubly magic nucleus $^{48}$Ca, dominated by a single transition, serves as a reference case for the quenching of spin-isospin modes in nuclei. The aim of the present work is a search for weak M1 transitions in $^{48}$Ca with a high-resolution (p,p') experiment at 295 MeV and forward angles including 0 degree and a comparison to results from a similar study using backward-angle electron scattering at low momentum transfers in order to estimate their contribution to the total B(M1) strength. M1 cross sections of individual peaks in the spectra are deduced with a multipole decomposition analysis. The corresponding reduced B(M1) transition strengths are extracted following the approach outlined in J. Birkhan et al., Phys. Rev. C 93, 041302(R) (2016). In total, 29 peaks containing a M1 contribution are found in the excitation energy region 7 - 13 MeV. The resulting B(M1) strength distribution compares well to the electron scattering results considering different factors limiting the sensitivity in both experiments and the enhanced importance of mechanisms breaking the proportionality of nuclear cross sections and electromagnetic matrix elements for weak transitions as studied here. The total strength of 1.19(6) $μ_N^2$ deduced assuming a non-quenched isoscalar part of the (p,p') cross sections agrees with the (e,e') result of 1.21(13) $μ_N^2$. A binwise analysis above 10 MeV provides an upper limit of 1.62(23) $μ_N^2$. The present results confirm that weak transitions contribute about 25% to the total B(M1) strength in $^{48}$Ca and the quenching factors of GT and spin-M1 strength are comparable in fp-shell nuclei. Thus, the role of of meson exchange currents seems to be neglible, in contrast to sd-shell nuclei.
description: 11 pages, 9 figures, revised analysis with oxygen contamination removed