cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Improved Approximations for Extremal Eigenvalues of Sparse Hamiltonians
Creators: name: Hothem, Daniel
name: Parekh, Ojas
name: Thompson, Kevin
Publisher: name: arXiv
Year: 2023
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We give a classical $1/(qk+1)$-approximation for the maximum eigenvalue of a $k$-sparse fermionic Hamiltonian with strictly $q$-local terms, as well as a $1/(4k+1)$-approximation when the Hamiltonian has both $2$-local and $4$-local terms. More generally we obtain a $1/O(qk^2)$-approximation for $k$-sparse fermionic Hamiltonians with terms of locality at most $q$. Our techniques also yield analogous approximations for $k$-sparse, $q$-local qubit Hamiltonians with small hidden constants and improved dependence on $q$.
description: 6 pages, No Figures, edited typos and added additional details on the qubit results, accepted to TQC2023
Measurements of differential cross sections of Higgs boson production through gluon fusion in the $H\to WW^{\ast}\to eνμν$ final state at $\sqrt{s} = 13$ TeV with the ATLAS detector
Creators: name: ATLAS Collaboration
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences

description: Higgs boson production via gluon-gluon fusion is measured in the $WW^{\ast} \to eνμν$ decay channel. The dataset utilized corresponds to an integrated luminosity of 139 fb$^{-1}$ collected by the ATLAS detector from $\sqrt{s}=13$ TeV proton-proton collisions delivered by the Large Hadron Collider between 2015 and 2018. Differential cross sections are measured in a fiducial phase space restricted to the production of at most one additional jet. The results are consistent with Standard Model expectations, derived using different Monte Carlo generators.
description: 59 pages in total, author list starting page 42, 22 figures, 6 tables, published in EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGG-2018-49/
Quantum Big Bounce of the isotropic Universe via a relational time
Creators: name: Giovannetti, Eleonora
name: Maione, Fabio
name: Montani, Giovanni
Publisher: name: arXiv
Year: 2023
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We analyze the canonical quantum dynamics of the isotropic Universe in a metric approach by adopting a self-interacting scalar field as relational time. When the potential term is absent we are able to associate the the expanding and collapsing dynamics of the Universe with the positive and negative frequency modes that emerge in the Wheeler-DeWitt equation. On the other side, when the potential term is present a non-zero transition amplitude from positive to negative frequency states arises, as in the standard relativistic scattering theory below the particle creation threshold. In particular, we are able to compute the transition probability for an expanding Universe that emerges from a collapsing regime both in the standard quantization procedure and in the polymer formulation. The probability distribution results similar in the two cases and its maximum takes place when the mean values of the momentum essentially coincide in the in-going and out-going wave packets, as it would take place in a semiclassical Big Bounce dynamics.
Principal Shapes and Squeezed Limits in the Effective Field Theory of Large Scale Structure
Creators: name: Bertolini, Daniele
name: Solon, Mikhail P.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We apply an orthogonalization procedure on the effective field theory of large scale structure (EFT of LSS) shapes, relevant for the angle-averaged bispectrum and non-Gaussian covariance of the matter power spectrum at one loop. Assuming natural-sized EFT parameters, this identifies a linear combination of EFT shapes - referred to as the principal shape - that gives the dominant contribution for the whole kinematic plane, with subdominant combinations suppressed by a few orders of magnitude. For the covariance, our orthogonal transformation is in excellent agreement with a principal component analysis applied to available data. Additionally we find that, for both observables, the coefficients of the principal shapes are well approximated by the EFT coefficients appearing in the squeezed limit, and are thus measurable from power spectrum response functions. Employing data from N-body simulations for the growth-only response, we measure the single EFT coefficient describing the angle-averaged bispectrum with $\mathcal{O}(10\%)$ precision. These methods of shape orthogonalization and measurement of coefficients from response functions are valuable tools for developing the EFT of LSS framework, and can be applied to more general observables.
description: 18+10 pages, 5 figures
Search for a new Z' gauge boson in $4μ$ events with the ATLAS experiment
Creators: name: ATLAS Collaboration
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences

description: This paper presents a search for a new Z' vector gauge boson with the ATLAS experiment at the Large Hadron Collider using pp collision data collected at $\sqrt{s} = 13$ TeV, corresponding to an integrated luminosity of 139 fb$^{-1}$. The new gauge boson Z' is predicted by $L_μ-L_τ$ models to address observed phenomena that can not be explained by the Standard Model. The search examines the four-muon (4$μ$) final state, using a deep learning neural network classifier to separate the Z' signal from the Standard Model background events. The di-muon invariant masses in the $4μ$ events are used to extract the Z' resonance signature. No significant excess of events is observed over the predicted background. Upper limits at a 95% confidence level on the Z' production cross-section times the decay branching fraction of $pp \rightarrow Z'μμ\rightarrow 4μ$ are set from 0.31 to 4.3 fb for the Z' mass ranging from 5 to 81 GeV. The corresponding common coupling strengths, $g_{Z'}$, of the Z' boson to the second and third generation leptons above 0.003 - 0.2 have been excluded.
description: 45 pages in total, author list starting at page 26, 7 figures, 3 tables, published by JHEP. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HDBS-2018-57/
A functor for constructing $R$-matrices in the category $\mathcal{O}$ of Borel quantum loop algebras
Creators: name: Pinet, Théo
Publisher: name: arXiv
Year: 2023
Subjects: subject: Representation Theory (math.RT)
subject: Mathematical Physics (math-ph)
subject: Quantum Algebra (math.QA)
subject: FOS: Mathematics
subject: FOS: Physical sciences

description: We tackle the problem of constructing $R$-matrices for the category $\mathcal{O}$ associated to the Borel subalgebra of an arbitrary untwisted quantum loop algebra $U_q(\mathfrak{g})$. For this, we define an exact functor $\mathcal{F}_q$ from the category $\mathcal{O}$ linked to $U_{q^{-1}}(\mathfrak{g})$ to the one linked to $U_q(\mathfrak{g})$. This functor $\mathcal{F}_q$ is compatible with tensor products, preserves irreducibility and interchanges the subcategories $\mathcal{O}^+$ and $\mathcal{O}^-$ of (D. Hernandez, B. Leclerc, Algebra Number Theory, 2016). We construct $R$-matrices for $\mathcal{O}^+$ by applying $\mathcal{F}_q$ on the braidings already found for $\mathcal{O}^-$ in (D. Hernandez, Rep. Theory, 2022). We also use the factorization of the latter intertwiners in terms of stable maps to deduce an analogous factorization for our new braidings. We finally obtain as byproducts new relations for the Grothendieck ring $K_0(\mathcal{O})$ as well as a functorial interpretation of a remarkable ring isomorphism $K_0(\mathcal{O}^+)\simeq K_0(\mathcal{O}^-)$ of Hernandez--Leclerc.
description: 38 pages, comments welcome
Nonconservative extension of Keplerian integrals and a new class of integrable system
Creators: name: Roa, Javier
Publisher: name: arXiv
Year: 2016
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: The invariance of the Lagrangian under time translations and rotations in Kepler's problem yields the conservation laws related to the energy and angular momentum. Noether's theorem reveals that these same symmetries furnish generalized forms of the first integrals in a special nonconservative case, which approximates various physical models. The system is perturbed by a biparametric acceleration with components along the tangential and normal directions. A similarity transformation reduces the biparametric disturbance to a simpler uniparametric forcing along the velocity vector. The solvability conditions of this new problem are discussed, and closed-form solutions for the integrable cases are provided. Thanks to the conservation of a generalized energy, the orbits are classified as elliptic, parabolic, and hyperbolic. Keplerian orbits appear naturally as particular solutions to the problem. After characterizing the orbits independently, a unified form of the solution is built based on the Weierstrass elliptic functions. The new trajectories involve fundamental curves such as cardioids and logarithmic, sinusoidal, and Cotes' spirals. These orbits can represent the motion of particles perturbed by solar radiation pressure, of spacecraft with continuous thrust propulsion, and some instances of Schwarzschild geodesics. Finally, the problem is connected with other known integrable systems in celestial mechanics.
description: 16 pages, 5 figures, published in MNRAS
Neural Network Approximation of Optimal Controls for Stochastic Reaction-Diffusion Equations
Creators: name: Stannat, Wilhelm
name: Vogler, Alexander
name: Wessels, Lukas
Publisher: name: arXiv
Year: 2023
Subjects: subject: Optimization and Control (math.OC)
subject: Probability (math.PR)
subject: FOS: Mathematics

description: We present a numerical algorithm that allows the approximation of optimal controls for stochastic reaction-diffusion equations with additive noise by first reducing the problem to controls of feedback form and then approximating the feedback function using finitely based approximations. Using structural assumptions on the finitely based approximations, rates for the approximation error of the cost can be obtained. Our algorithm significantly reduces the computational complexity of finding controls with asymptotically optimal cost. Numerical experiments using artificial neural networks as well as radial basis function networks illustrate the performance of our algorithm. Our approach can also be applied to stochastic control problems for high dimensional stochastic differential equations and more general stochastic partial differential equations.
description: 12 figures
The Link Between the Local Bubble and Radioisotopic Signatures on Earth
Creators: name: Feige, Jenny
name: Breitschwerdt, Dieter
name: Wallner, Anton
name: Schulreich, Michael M.
name: Kinoshita, Norikazu
name: Paul, Michael
name: Dettbarn, Christian
name: Fifield, L. Keith
name: Golser, Robin
name: Honda, Maki
name: Linnemann, Ulf
name: Matsuzaki, Hiroyuki
name: Merchel, Silke
name: Rugel, Georg
name: Steier, Peter
name: Tims, Stephen G.
name: Winkler, Stephan R.
name: Yamagata, Takeyasu
Publisher: name: arXiv
Year: 2016
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Traces of 2-3 Myr old 60Fe were recently discovered in a manganese crust and in lunar samples. We have found that this signal is extended in time and is present in globally distributed deep-sea archives. A second 6.5-8.7 Myr old signature was revealed in a manganese crust. The existence of the Local Bubble hints to a recent nearby supernova-activity starting 13 Myr ago. With analytical and numerical models generating the Local Bubble, we explain the younger 60Fe-signature and thus link the evolution of the solar neighborhood to terrestrial anomalies.
description: 4 pages, 3 figures, accepted for publication in JPS Conf. Proc
A Pilot Study of Nulling in 22 Pulsars Using Mixture Modeling
Creators: name: Anumarlapudi, Akash
name: Swiggum, Joseph K.
name: Kaplan, David L.
name: Fichtenbauer, Travis D. J.
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: The phenomenon of pulsar nulling, observed as the temporary inactivity of a pulsar, remains poorly understood both observationally and theoretically. Most observational studies that quantify nulling employ a variant of Ritchings (1976)'s algorithm which can suffer significant biases for pulsars where the emission is weak. Using a more robust mixture model method, we study pulsar nulling in a sample of 22 recently discovered pulsars, for which we publish the nulling fractions for the first time. These data clearly demonstrate biases of the former approach and show how an otherwise non-nulling pulsar can be classified as having significant nulls. We show that the population-wide studies that find a positive correlation of nulling with pulsar period/characteristic age can similarly be biased because of the bias in estimating the nulling fraction. We use our probabilistic approach to find the evidence for periodicity in the nulls in a subset of three pulsars in our sample. In addition, we also provide improved timing parameters for 17 of the 22 pulsars that had no prior follow-up.
description: Accepted for publication in the Astrophysical Journal (ApJ)
Angular dependence of the Wigner time delay upon strong field ionization from an aligned p-orbital
Creators: name: Trabert, D.
name: Anders, N.
name: Geyer, A.
name: Hofmann, M.
name: Schöffler, M. S.
name: Schmidt, L. Ph. H.
name: Jahnke, T.
name: Kunitski, M.
name: Dörner, R.
name: Eckart, S.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Atomic Physics (physics.atom-ph)
subject: FOS: Physical sciences

description: We present experimental data on the strong-field ionization of the argon dimer in a co-rotating two-color (CoRTC) laser field. We observe a sub-cycle interference pattern in the photoelectron momentum distribution and infer the Wigner time delay using holographic angular streaking of electrons (HASE). We find that the Wigner time delay varies by more than 400 attoseconds as a function of the electron emission direction with respect to the molecular axis. The measured time delay is found to be independent of the parity of the dimer-cation and is in good agreement with our theoretical model based on the ionization of an aligned atomic p-orbital.
description: 6 pages, 4 figures
Decay of Activity Complexes, Formation of Unipolar Magnetic Regions and Coronal Holes in their Causal Relation
Creators: name: Golubeva, Elena
name: Mordvinov, Alexander
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: North-south asymmetry of sunspot activity resulted in an asynchronous reversal of the Sun's polar fields in the current cycle. The asymmetry is also observed in the formation of polar coronal holes. A stable coronal hole was first formed at the South Pole, despite the later polar-field reversal there. The aim of this study is to understand processes making this situation possible. Synoptic magnetic maps from the Global Oscillation Network Group and corresponding coronal-hole maps from the Extreme ultraviolet Imaging Telescope aboard the Solar and Heliospheric Observatory and the Atmospheric Imaging Assembly aboard the Solar Dynamics Observatory are analyzed here to study a causal relationship between the decay of activity complexes, evolution of large-scale magnetic fields, and formation of coronal holes. Ensembles of coronal holes associated with decaying active regions and activity complexes are presented. These ensembles take part in global rearrangements of the Sun's open magnetic flux. In particular, the south polar coronal hole was formed from an ensemble of coronal holes that originated after the decay of multiple activity complexes observed during 2014.
description: The article is submitted to Solar Physics. John Leibacher, Editor-in-Chief, recommended submitting the manuscript to arXiv.org. Editorial modifications for the manuscript are made
Current and future constraints on Bekenstein-type models for varying couplings
Creators: name: Leite, A. C. O.
name: Martins, C. J. A. P.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Astrophysical tests of the stability of dimensionless fundamental couplings, such as the fine-structure constant $α$ and the proton-to-electron mass ratio $μ$, are an optimal probe of new physics. There is a growing interest in these tests, following indications of possible spacetime variations at the few parts per million level. Here we make use of the latest astrophysical measurements, combined with background cosmological observations, to obtain improved constraints on Bekenstein-type models for the evolution of both couplings. These are arguably the simplest models allowing for $α$ and $μ$ variations, and are characterized by a single free dimensionless parameter, $ζ$, describing the coupling of the underlying dynamical degree of freedom to the electromagnetic sector. In the former case we find that this parameter is constrained to be $|ζ_α|<4.8\times10^{-6}$ (improving previous constraints by a factor of 6), while in the latter (which we quantitatively compare to astrophysical measurements for the first time) we find $ζ_μ=(2.7\pm3.1)\times10^{-7}$; both of these are at the $99.7\%$ confidence level. For $ζ_α$ this constraint is about 20 times stronger than the one obtained from local Weak Equivalence Principle tests, while for $ζ_μ$ it is about 2 orders of magnitude weaker. We also discuss the improvements on these constraints to be expected from the forthcoming ESPRESSO and ELT-HIRES spectrographs, conservatively finding a factor around 5 for the former and around 50 for the latter.
description: 10 pages, 8 figures
The role of spatial curvature in constraining the Universe anisotropies across a Big Bounce
Creators: name: Giovannetti, Eleonora
name: Montani, Giovanni
Publisher: name: arXiv
Year: 2023
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We study the implementation of Polymer Quantum Mechanics (PQM) to a system decomposed into a quasi-classical background and a small quantum subsystem, according to the original Vilenkin proposal. We develop the whole formalism in the momentum representation that is the only viable in the continuum limit of the polymer paradigm and we generalize the fundamental equations of the original Vilenkin analysis in the considered context. Then, we provide a Minisuperspace application of the theory, first considering a Bianchi I cosmology and then extending the analysis to a Bianchi IX model in the limit of small anisotropies. In both these cases, the quasi-classical background is identified with an isotropic bouncing Universe whereas the small quantum subsystem contains the anisotropic degrees of freedom. When the Big Bounce scenario is considered, we obtain that in the Bianchi I model the anisotropies standard deviation is regular at $t=0$ but still increases indefinitely, whereas in the presence of the harmonic Bianchi IX potential such same quantity is bounded and oscillate around a constant value. As a consequence, we demonstrate that the picture of a semiclassical isotropic Bounce can be extended to more general cosmological settings if the spatial curvature becomes relevant when the anisotropic degrees of freedom are still small quantum variables.
Recent advances in the Self-Referencing Embedding Strings (SELFIES) library
Creators: name: Lo, Alston
name: Pollice, Robert
name: Nigam, AkshatKumar
name: White, Andrew D.
name: Krenn, Mario
name: Aspuru-Guzik, Alán
Publisher: name: arXiv
Year: 2023
Subjects: subject: Chemical Physics (physics.chem-ph)
subject: Machine Learning (cs.LG)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: String-based molecular representations play a crucial role in cheminformatics applications, and with the growing success of deep learning in chemistry, have been readily adopted into machine learning pipelines. However, traditional string-based representations such as SMILES are often prone to syntactic and semantic errors when produced by generative models. To address these problems, a novel representation, SELF-referencIng Embedded Strings (SELFIES), was proposed that is inherently 100% robust, alongside an accompanying open-source implementation. Since then, we have generalized SELFIES to support a wider range of molecules and semantic constraints and streamlined its underlying grammar. We have implemented this updated representation in subsequent versions of \selfieslib, where we have also made major advances with respect to design, efficiency, and supported features. Hence, we present the current status of \selfieslib (version 2.1.1) in this manuscript.
description: 11 pages, 2 figures
Chiral electroluminescence from thin-film perovskite metacavities
Creators: name: Kim, Seongheon
name: An, Soo-Chan
name: Kim, Younggon
name: Shin, Yun Seop
name: Antonov, Alexander A.
name: Seo, In Cheol
name: Woo, Byung Hoon
name: Lim, Yeonsoo
name: Gorkunov, Maxim V.
name: Kivshar, Yuri S.
name: Kim, Jin Young
name: Jun, Young Chul
Publisher: name: arXiv
Year: 2023
Subjects: subject: Optics (physics.optics)
subject: Applied Physics (physics.app-ph)
subject: FOS: Physical sciences

description: Chiral light sources realized in ultracompact device platforms are highly desirable for various applications. Among active media employed for thin-film emission devices, lead-halide perovskites have been extensively studied for photoluminescence due to their exceptional properties. However, up to date, there have been no demonstrations of chiral electroluminescence with a substantial degree of circular polarization (DCP), being critical for the development of practical devices. Here, we propose a new concept of chiral light sources based on a thin-film perovskite metacavity and experimentally demonstrate chiral electroluminescence with DCP approaching 0.38. We design a metacavity created by a metal and a dielectric metasurface supporting photonic eigenstates with close-to-maximum chiral response. Chiral cavity modes facilitate asymmetric electroluminescence of pairs of left and right circularly polarized waves propagating in the opposite oblique directions. The proposed ultracompact light sources are especially advantageous for many applications requiring chiral light beams of both helicities.
description: 20 pages, 4 figures
Plaquette Singlet Transition, Magnetic Barocaloric Effect, and Spin Supersolidity in the Shastry-Sutherland Model
Creators: name: Wang, Junsen
name: Li, Han
name: Xi, Ning
name: Gao, Yuan
name: Yan, Qing-Bo
name: Li, Wei
name: Su, Gang
Publisher: name: arXiv
Year: 2023
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: Inspired by recent experimental measurements [Guo \textit{et al.}, Phys. Rev. Lett.~\textbf{124}, 206602 (2020); Jiménez \textit{et al.}, Nature \textbf{592}, 370 (2021)] on frustrated quantum magnet SrCu$_2$(BO$_3$)$_2$ under combined pressure and magnetic fields, we study the related spin-$1/2$ Shastry-Sutherland (SS) model using state-of-the-art tensor network methods. By calculating thermodynamics, correlations and susceptibilities, we find, in zero magnetic field, not only a line of first-order plaquette-singlet (PS) to dimer-singlet phase transition ending with a critical point, but also signatures of the ordered PS transition with its critical endpoint terminating on this first-order line. Moreover, we uncover prominent magnetic barocaloric responses, a novel type of quantum correlation induced cooling effect, in the strongly fluctuating supercritical regime. Under finite fields, we identify a quantum phase transition from the PS phase to the spin supersolid phase that breaks simultaneously lattice translational and spin rotational symmetries. The present findings on the SS model are accessible in current experiments and would shed new light on exotic critical and supercritical phenomena in archetypal frustrated quantum magnets.
description: Close to the published version. 7 pages, 4 figures (SM 9 pages, 12 figures)
Scalable Bayesian optimization with high-dimensional outputs using randomized prior networks
Creators: name: Bhouri, Mohamed Aziz
name: Joly, Michael
name: Yu, Robert
name: Sarkar, Soumalya
name: Perdikaris, Paris
Publisher: name: arXiv
Year: 2023
Subjects: subject: Machine Learning (cs.LG)
subject: Artificial Intelligence (cs.AI)
subject: Optimization and Control (math.OC)
subject: Machine Learning (stat.ML)
subject: FOS: Computer and information sciences
subject: FOS: Mathematics

description: Several fundamental problems in science and engineering consist of global optimization tasks involving unknown high-dimensional (black-box) functions that map a set of controllable variables to the outcomes of an expensive experiment. Bayesian Optimization (BO) techniques are known to be effective in tackling global optimization problems using a relatively small number objective function evaluations, but their performance suffers when dealing with high-dimensional outputs. To overcome the major challenge of dimensionality, here we propose a deep learning framework for BO and sequential decision making based on bootstrapped ensembles of neural architectures with randomized priors. Using appropriate architecture choices, we show that the proposed framework can approximate functional relationships between design variables and quantities of interest, even in cases where the latter take values in high-dimensional vector spaces or even infinite-dimensional function spaces. In the context of BO, we augmented the proposed probabilistic surrogates with re-parameterized Monte Carlo approximations of multiple-point (parallel) acquisition functions, as well as methodological extensions for accommodating black-box constraints and multi-fidelity information sources. We test the proposed framework against state-of-the-art methods for BO and demonstrate superior performance across several challenging tasks with high-dimensional outputs, including a constrained multi-fidelity optimization task involving shape optimization of rotor blades in turbo-machinery.
description: 23 pages, 8 figures
Large-Sample Properties of Blind Estimation of the Linear Discriminant Using Projection Pursuit
Creators: name: Radojicic, Una
name: Nordhausen, Klaus
name: Virta, Joni
Publisher: name: arXiv
Year: 2021
Subjects: subject: Statistics Theory (math.ST)
subject: Methodology (stat.ME)
subject: FOS: Mathematics
subject: FOS: Computer and information sciences

description: We study the estimation of the linear discriminant with projection pursuit, a method that is blind in the sense that it does not use the class labels in the estimation. Our viewpoint is asymptotic and, as our main contribution, we derive central limit theorems for estimators based on three different projection indices, skewness, kurtosis and their convex combination. The results show that in each case the limiting covariance matrix is proportional to that of linear discriminant analysis (LDA), an unblind estimator of the discriminant. An extensive comparative study between the asymptotic variances reveals that projection pursuit is able to achieve efficiency equal to LDA when the groups are arbitrarily well-separated and their sizes are reasonably balanced. We conclude with a real data example and a simulation study investigating the validity of the obtained asymptotic formulas for finite samples.
Unconditional Fock state generation using arbitrarily weak photonic nonlinearities
Creators: name: Lingenfelter, Andrew
name: Roberts, David
name: Clerk, A. A.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Quantum Physics (quant-ph)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We present a new mechanism that harnesses extremely weak Kerr-type nonlinearities in a single driven cavity to deterministically generate single photon Fock states, and more general photon-blockaded states. Our method is effective even for nonlinearities that are orders-of-magnitude smaller than photonic loss. It is also completely distinct from so-called unconventional photon blockade mechanisms, as the generated states are non-Gaussian, exhibit a sharp cut-off in their photon number distribution, and can be arbitrary close to a single-photon Fock state. Our ideas require only standard linear and parametric drives, and is hence compatible with a variety of different photonic platforms.
description: 14 pages, 7 figures, equivalent to the published version
Stationary subspace analysis based on second-order statistics
Creators: name: Flumian, Lea
name: Matilainen, Markus
name: Nordhausen, Klaus
name: Taskinen, Sara
Publisher: name: arXiv
Year: 2021
Subjects: subject: Methodology (stat.ME)
subject: FOS: Computer and information sciences

description: In stationary subspace analysis (SSA) one assumes that the observable p-variate time series is a linear mixture of a k-variate nonstationary time series and a (p-k)-variate stationary time series. The aim is then to estimate the unmixing matrix which transforms the observed multivariate time series onto stationary and nonstationary components. In the classical approach multivariate data are projected onto stationary and nonstationary subspaces by minimizing a Kullback-Leibler divergence between Gaussian distributions, and the method only detects nonstationarities in the first two moments. In this paper we consider SSA in a more general multivariate time series setting and propose SSA methods which are able to detect nonstationarities in mean, variance and autocorrelation, or in all of them. Simulation studies illustrate the performances of proposed methods, and it is shown that especially the method that detects all three types of nonstationarities performs well in various time series settings. The paper is concluded with an illustrative example.
Thermal boundary condition studies in large aspect ratio Rayleigh-Bénard convection
Creators: name: Käufer, Theo
name: Vieweg, Philipp P.
name: Schumacher, Jörg
name: Cierpka, Christian
Publisher: name: arXiv
Year: 2023
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: We study the influence of thermal boundary conditions on large aspect ratio Rayleigh-Bénard convection by a joint analysis of experimental and numerical data sets for a Prandl number $\mathrm{Pr = 7}$ and Rayleigh numbers $\mathrm{Ra = 10^5 - 10^6}$. The spatio-temporal experimental data are obtained by combined Particle Image Velocimetry and Particle Image Thermometry measurements in a cuboid cell filled with water at an aspect ratio $Γ= 25$. In addition, numerical data are generated by Direct Numerical Simulations (DNS) in domains with $Γ= 25$ and $Γ= 60$ subject to different thermal boundary conditions. Our experimental data show an increased characteristic horizontal extension scale of the flow structures, $\tildeλ$, for increasing Ra, which is coupled with a raise of the Biot number Bi in particular at the cooling plate. However, we find the experimental flow structure size to range in any case between the ones observed for the idealized thermal conditions captured by the simulations. On the one hand, they are larger than in the numerical case with applied uniform temperatures at the plates, but, on the other hand, smaller than in the case of an applied constant heat flux, the latter of which leads to a structure that grows gradually up to the horizontal domain size. We link this observation qualitatively to theoretical predictions for the onset of convection. Furthermore, we study the effect of the asymmetric boundary conditions on the heat transfer. Contrasting experimental and numerical data reveals an increased probability of far-tail events of reversed heat transfer. The decomposition of the local Nusselt number $\mathrm{Nu_{loc}}$ traces this effect back to the sign of the temperature deviation $\tildeΘ$, revealing asymmetries of the heating and cooling plate on the thermal variance of the generated thermal plumes.
Self-Healing First-Order Distributed Optimization
Creators: name: Ridgley, Israel L. Donato
name: Freeman, Randy A.
name: Lynch, Kevin M.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Optimization and Control (math.OC)
subject: Multiagent Systems (cs.MA)
subject: Systems and Control (eess.SY)
subject: FOS: Mathematics
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: In this paper we describe a parameterized family of first-order distributed optimization algorithms that enable a network of agents to collaboratively calculate a decision variable that minimizes the sum of cost functions at each agent. These algorithms are self-healing in that their correctness is guaranteed even if they are initialized randomly, agents drop in or out of the network, local cost functions change, or communication packets are dropped. Our algorithms are the first single-Laplacian methods to exhibit all of these characteristics. We achieve self-healing by sacrificing internal stability, a fundamental trade-off for single-Laplacian methods.
description: Corrected equation (40) by changing "min" to "max", results unaffected
Pauli-based model of quantum computation with higher-dimensional systems
Creators: name: Peres, Filipa C. R.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Pauli-based computation (PBC) is a universal model for quantum computation with qubits where the input state is a magic (resource) state and the computation is driven by a sequence of adaptively chosen and compatible multiqubit Pauli measurements. Here we generalize PBC for odd-prime-dimensional systems and demonstrate its universality. Additionally, we discuss how any qudit-based PBC can be implemented on actual, circuit-based quantum hardware. Our results show that we can translate a PBC on $n$ $p$-dimensional qudits to adaptive circuits on $n+1$ qudits with $O\left( pn^2/2 \right)$ $\mathrm{SUM}$ gates and depth. Alternatively, we can carry out the same computation with $O\left( pn/2\right)$ depth at the expense of an increased circuit width. Finally, we show that the sampling complexity associated with simulating a number $k$ of virtual qudits is related to the robustness of magic of the input states. Computation of this magic monotone for qutrit and ququint states leads to sampling complexity upper bounds of, respectively, $O\left( 3^{ 1.0848 k} ε^{-2}\right)$ and $O\left( 5^{ 1.4022 k} ε^{-2}\right)$, for a desired precision $ε$. We further establish lower bounds to this sampling complexity for qubits, qutrits, and ququints: $Ω\left( 2^{0.5431 k} ε^{-2} \right)$, $Ω\left( 3^{0.7236 k} ε^{-2} \right)$, and $Ω\left( 5^{0.8544 k} ε^{-2} \right)$, respectively.
description: 15 pages, 4 figures
title: Μελέτη αντιοξειδωτικής δράσης ενώσεων μετά από γαστρεντερική προσομοίωση.
title: Study of antioxidant activity of compounds after gastrointestinal simulation.
titleType: AlternativeTitle
Creators: name: Γεωργακοπούλου, Παναγιώτα
name: Στέρπη, Ευσταθία
Publisher: name: Πανεπιστήμιο Δυτικής Αττικής
Year: 2023
Subjects: Χαρούπι
Αντιοξειδωτικά
Νόσος του Chron's
Folin-Ciocalteu
Μικροβιολογική ενεργότητα
In vitro
Γαστρεντερικό σύστημα

description: Δεδομένου ότι το χαρούπι αποτελεί την νέα τάση στην αγορά και επανέρχεται εδραιώνοντας την θέση του στο καθημερινό διατροφολόγιο του κόσμου λόγω της ωφέλιμης δράσης του στην υγεία και του πλούσιου περιεχομένου από αντιοξειδωτικά, θρεπτικά συστατικά και ιχνοστοιχεία αποτελεί ένα αξιόλογο και ενδιαφέρον θέμα μελέτης. Μέσω της εκπόνησης της συγκεκριμένης πτυχιακής εργασίας που είχε πειραματικό και ερευνητικό χαρακτήρα επρόκειτο να μελετηθεί ο τρόπος απορρόφησης ευεργετικών συστατικών του χαρουπόμελου και της δράσης και συνεισφοράς του ανθρώπινου μικροβιώματος σε όλη αυτή την διεργασία σε έναν άνθρωπο υγιή και έναν άνθρωπο που πάσχει από νόσο του Crohn’s. Σε πειραματικό επίπεδο ακολουθήθηκε μια διαδικασία μέσω της οποίας δημιουργήθηκε ένα in vitro γαστρεντερικό σύστημα σε εργαστηριακό επίπεδο. Ουσιαστικά ακολουθήθηκε μία όσο το δυνατόν πιο κοντινή αναπαράσταση των διεργασιών που λαμβάνουν χώρο από την στιγμή της πρόσληψης μίας τροφής και της εισόδου της στον οργανισμό έως την στιγμή της τελικής απομάκρυνσης της από αυτόν αφού πρώτα έχουν απορροφηθεί όλα τα απαραίτητα συστατικά που μπορεί να προσδώσει στον οργανισμό. Ακολουθήθηκαν αυστηρά πέντε στάδια που προσομοίαζαν την αρχική και την γαστρική φάση, την εντερική, την πρώιμη εντερική ζύμωση και την όψιμη γαστρική ζύμωση όπου στο τέλος κάθε σταδίου συλλέγονταν δείγματα τα οποία υποβάλλονταν στην διαδικασία της ανάλυσης της Folin και καταγραφόταν το σύνολο των φαινολικών ουσιών. Εντός του πειραματικού αυτού πλάνου απαραίτητες κρίθηκαν και κάποιες μικροβιολογικές αναλύσεις που αφορούσαν τα δείγματα των περιττωμάτων ως προς την μικροβιολογική τους ενεργότητα. Από την διεξαγωγή αυτής της μελέτης προέκυψε για αρχή ξεκάθαρη αλληλεπίδραση μεταξύ του ανθρώπινου μικροβιώματος με τις φαινόλες του χαρουπόμελου οι οποίες και μετρήθηκαν τελικώς.
Iterated Filters for Nonlinear Transition Models
Creators: name: Kullberg, Anton
name: Skog, Isaac
name: Hendeby, Gustaf
Publisher: name: arXiv
Year: 2023
Subjects: subject: Signal Processing (eess.SP)
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: A new class of iterated linearization-based nonlinear filters, dubbed dynamically iterated filters, is presented. Contrary to regular iterated filters such as the iterated extended Kalman filter (IEKF), iterated unscented Kalman filter (IUKF) and iterated posterior linearization filter (IPLF), dynamically iterated filters also take nonlinearities in the transition model into account. The general filtering algorithm is shown to essentially be a (locally over one time step) iterated Rauch-Tung-Striebel smoother. Three distinct versions of the dynamically iterated filters are especially investigated: analogues to the IEKF, IUKF and IPLF. The developed algorithms are evaluated on 25 different noise configurations of a tracking problem with a nonlinear transition model and linear measurement model, a scenario where conventional iterated filters are not useful. Even in this "simple" scenario, the dynamically iterated filters are shown to have superior root mean-squared error performance as compared with their respective baselines, the EKF and UKF. Particularly, even though the EKF diverges in 22 out of 25 configurations, the dynamically iterated EKF remains stable in 20 out of 25 scenarios, only diverging under high noise.
description: 8 pages. Accepted to IEEE International Conference on Information Fusion 2023 (FUSION 2023). Copyright 2023 IEEE
Magnetoelectrics in Disordered Topological Insulator Josephson Junctions
Creators: name: Bobkova, I. V.
name: Bobkov, A. M.
name: Zyuzin, Alexander A.
name: Alidoust, Mohammad
Publisher: name: arXiv
Year: 2016
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Materials Science (cond-mat.mtrl-sci)
subject: Superconductivity (cond-mat.supr-con)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We theoretically study the coupling of electric charge and spin polarization in an equilibrium and nonequilibrium electric transport across a two dimensional Josephson configuration comprised of disordered surface channels of a three dimensional topological insulator. In the equilibriun state of the system we predict the Edelstein effect, which is much more pronounced than its counterpart in conventional spin orbit coupled materials. Employing a quasiclassical Keldysh technique, we demonstrate that the ground state of system can be experimentally shifted into arbitrary macroscopic superconducting phase differences other than the standard `$0$' or `$π$', constituting a $ϕ_0$-junction, solely by modulating a quasiparticle flow injection into the junction. We propose a feasible experiment where the quasiparticles are injected into the topological insulator surface by means of a normal electrode and voltage gradient so that oppositely oriented stationary spin densities can be developed along the interfaces and allow for directly making use of the spin-momentum locking nature of Dirac fermions in the surface channels. The $ϕ_0$-state is proportional to the voltage difference applied between the injector electrode and superconducting terminals that calibrates the injection rate of particles and, therefore, the $ϕ_0$ shift.
Crawling and turning in a minimal reaction-diffusion cell motility model: coupling cell shape and biochemistry
Creators: name: Camley, Brian A.
name: Zhao, Yanxiang
name: Li, Bo
name: Levine, Herbert
name: Rappel, Wouter-Jan
Publisher: name: arXiv
Year: 2016
Subjects: subject: Biological Physics (physics.bio-ph)
subject: Soft Condensed Matter (cond-mat.soft)
subject: Cell Behavior (q-bio.CB)
subject: FOS: Physical sciences
subject: FOS: Biological sciences

description: We study a minimal model of a crawling eukaryotic cell with a chemical polarity controlled by a reaction-diffusion mechanism describing Rho GTPase dynamics. The size, shape, and speed of the cell emerge from the combination of the chemical polarity, which controls the locations where actin polymerization occurs, and the physical properties of the cell, including its membrane tension. We find in our model both highly persistent trajectories, in which the cell crawls in a straight line, and turning trajectories, where the cell transitions from crawling in a line to crawling in a circle. We discuss the controlling variables for this turning instability, and argue that turning arises from a coupling between the reaction-diffusion mechanism and the shape of the cell. This emphasizes the surprising features that can arise from simple links between cell mechanics and biochemistry. Our results suggest that similar instabilities may be present in a broad class of biochemical descriptions of cell polarity.
description: 12 pages, 12 figures
Current-voltage characteristics of the N-I-PT-symmetric non-Hermitian superconductor junction as a probe of non-Hermitian formalisms
Creators: name: Kornich, Viktoriia
Publisher: name: arXiv
Year: 2023
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: We study theoretically a junction consisting of a normal metal, PT-symmetric non-Hermitian superconductor, and an insulating thin layer between them (N-I-PTS junction). We calculate current-voltage characteristics for this junction using left-right and right-right bases and compare the results. We find that in the left-right basis, the Andreev-scattered particles move in the opposite direction compared to the right-right basis and conventional Andreev scattering. This leads to profound differences in current-voltage characteristics. Based on this and other signatures, we argue that left-right basis is not applicable in this case. Remarkably, we find that the growth and decay with time of the states with imaginary energies in right-right basis are equilibrated.
Thermodynamic determination of the equilibrium first-order phase-transition line hidden by hysteresis in a phase diagram
Creators: name: Matsuura, Keisuke
name: Nishizawa, Yo
name: Kriener, Markus
name: Kurumaji, Takashi
name: Oike, Hiroshi
name: Tokura, Yoshinori
name: Kagawa, Fumitaka
Publisher: name: arXiv
Year: 2023
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: Phase diagrams form the basis for the study of material science, and the profiles of phase-transition lines separating different thermodynamic phases include comprehensive information about thermodynamic quantities, such as latent heat. However, in some materials exhibiting field-induced first-order transitions (FOTs), the equilibrium phase-transition line is hidden by the hysteresis region associated with the FOT; thus, it cannot be directly determined from measurements of resistivity, magnetization, etc. Here, we demonstrate a thermodynamics-based method for determining the hidden equilibrium FOT line. This method is verified for the FOT between antiferromagnetic and ferrimagnetic states in magneto-electric compounds (Fe$_{0.95}$Zn$_{0.05}$)$_{2}$Mo$_{3}$O$_{8}$. The equilibrium FOT line determined based on the Clausius-Clapeyron equation exhibits a reasonable profile in terms of the third law of thermodynamics, and it shows marked differences from the midpoints of the hysteresis region. Our findings highlight that care should be taken for referring to the hysteresis midpoint line when discussing field-induced latent heat or magnetocaloric effects.
description: 22 pages, 7 figures
A Deep Reinforcement Learning-Based Resource Scheduler for Massive MIMO Networks
Creators: name: An, Qing
name: Segarra, Santiago
name: Dick, Chris
name: Sabharwal, Ashutosh
name: Doost-Mohammady, Rahman
Publisher: name: arXiv
Year: 2023
Subjects: subject: Information Theory (cs.IT)
subject: FOS: Computer and information sciences

description: The large number of antennas in massive MIMO systems allows the base station to communicate with multiple users at the same time and frequency resource with multi-user beamforming. However, highly correlated user channels could drastically impede the spectral efficiency that multi-user beamforming can achieve. As such, it is critical for the base station to schedule a suitable group of users in each time and frequency resource block to achieve maximum spectral efficiency while adhering to fairness constraints among the users. In this paper, we consider the resource scheduling problem for massive MIMO systems with its optimal solution known to be NP-hard. Inspired by recent achievements in deep reinforcement learning (DRL) to solve problems with large action sets, we propose \name{}, a dynamic scheduler for massive MIMO based on the state-of-the-art Soft Actor-Critic (SAC) DRL model and the K-Nearest Neighbors (KNN) algorithm. Through comprehensive simulations using realistic massive MIMO channel models as well as real-world datasets from channel measurement experiments, we demonstrate the effectiveness of our proposed model in various channel conditions. Our results show that our proposed model performs very close to the optimal proportionally fair (Opt-PF) scheduler in terms of spectral efficiency and fairness with more than one order of magnitude lower computational complexity in medium network sizes where Opt-PF is computationally feasible. Our results also show the feasibility and high performance of our proposed scheduler in networks with a large number of users and resource blocks.
description: IEEE Transactions on Machine Learning in Communications and Networking (TMLCN) 2023