Journal articles: 'Multi-Physics correlations'

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Spikes, Kyle T., and Mrinal K. Sen. "Correlations of inclusion-based rock-physics model inputs from Bayesian analysis." Journal of Geophysics and Engineering 19, no. 5 (September 10, 2022): 965–81. http://dx.doi.org/10.1093/jge/gxac063.

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Abstract For any given rock-physics model, knowledge of correlations among its inputs helps to define geologically and physically meaningful and informed models for a given problem. These informed models can, in turn, reduce the uncertainty in forward and inverse problems. We use a Bayesian framework to identify such correlations among inputs of two rock-physics models. That framework makes use of velocity and porosity measurements on both dry and brine-saturated carbonate samples. Two inclusion-based rock-physics models, the self-consistent approximation and the differential effective medium model, are analyzed along with these data to identify the underlying correlations. To do so, the posterior distribution must be evaluated, which is based on a prior model and the calculated likelihood function. Exhaustive sampling of the posterior is convenient in this case because relatively few input parameters to consider. Results are multi-variate histograms that indicate maximum a posteriori values of the inputs. Correlations among the inputs become evident when the Bayesian analysis is repeated many times with different prior models. These correlated values provide the inputs to optimized maximum a posteriori models. The correlations identified for the two rock-physics models under study should be used in relevant applications. Finally, all rock-physics models, along with an appropriate data set, should be examined in a similar Bayesian framework.

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Babaee, H., P. Perdikaris, C. Chryssostomidis, and G. E. Karniadakis. "Multi-fidelity modelling of mixed convection based on experimental correlations and numerical simulations." Journal of Fluid Mechanics 809 (November 21, 2016): 895–917. http://dx.doi.org/10.1017/jfm.2016.718.

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For thermal mixed-convection flows, the Nusselt number is a function of Reynolds number, Grashof number and the angle between the forced- and natural-convection directions. We consider flow over a heated cylinder for which there is no universal correlation that accurately predicts Nusselt number as a function of these parameters, especially in opposing-convection flows, where the natural convection is against the forced convection. Here, we revisit this classical problem by employing modern tools from machine learning to develop a general multi-fidelity framework for constructing a stochastic response surface for the Nusselt number. In particular, we combine previously developed experimental correlations (low-fidelity model) with direct numerical simulations (high-fidelity model) using Gaussian process regression and autoregressive stochastic schemes. In this framework the high-fidelity model is sampled only a few times, while the inexpensive empirical correlation is sampled at a very high rate. We obtain the mean Nusselt number directly from the stochastic multi-fidelity response surface, and we also propose an improved correlation. This new correlation seems to be consistent with the physics of this problem as we correct the vectorial addition of forced and natural convection with a pre-factor that weighs differently the forced convection. This, in turn, results in a new definition of the effective Reynolds number, hence accounting for the ‘incomplete similarity’ between mixed convection and forced convection. In addition, due to the probabilistic construction, we can quantify the uncertainty associated with the predictions. This information-fusion framework is useful for elucidating the physics of the flow, especially in cases where anomalous transport or interesting dynamics may be revealed by contrasting the variable fidelity across the models. While in this paper we focus on the thermal mixed convection, the multi-fidelity framework provides a new paradigm that could be used in many different contexts in fluid mechanics including heat and mass transport, but also in combining various levels of fidelity of models of turbulent flows.

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Papadionysiou, Marianna, Kim Seongchan, Mathieu Hursin, Alexander Vasiliev, Hakim Ferroukhi, Andreas Pautz, and Joo Han Gyu. "COUPLING OF nTRACER TO COBRA-TF FOR HIGH-FIDELITY ANALYSIS OF VVERs." EPJ Web of Conferences 247 (2021): 02008. http://dx.doi.org/10.1051/epjconf/202124702008.

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Paul Scherrer Institut is developing a high-resolution multi-physics core solver for VVER analysis. This work presents the preliminary stages of the development, specifically the coupling of the 3D pin-by-pin neutronic solver nTRACER to the sub-channel thermal-hydraulic code COBRA-TF for single assembly multi-physics steady state calculations. The coupling scheme and the modifications performed in the codes are described in details. The results of the coupled nTRACER/COBRA-TF calculations are compared to the ones of a standalone nTRACER calculation where the feedbacks are provided by a simplified 1D thermal-hydraulic solver. The agreement is very good with fuel temperature differences around 10 K which can be attributed to the different correlations used in the various solvers. The cross-comparison of the two multi-physics computational routes serves as a preliminary verification of the coupling scheme developed between nTRACER and COBRA-TF.

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Abdel-Khalek, S., K. Berrada, and H. Eleuch. "Quantum correlation and non-classical properties in semiconductor microcavities for multi-photon excitation." International Journal of Quantum Information 17, no. 05 (August 2019): 1950047. http://dx.doi.org/10.1142/s0219749919500473.

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We study how the interplay of weak excitation regime of quantum well confined in a semiconductor microcavity affects the dynamics of correlations and the statistical properties of photons. We discuss how the system parameters can impact the quantum entropy and Mandel’s parameter, and illustrate our concerns with numerical simulations. We have found that the enhancement of the correlations and the control of the statistical properties of photons in semiconductor microcavities for multi-photon excitation highly benefits from the combination of the strength of the field, excitonic spontaneous emission rate, cavity dissipative rate, and the coupling between the exciton and photons. Our results may have important implications not only for those specially interested in quantum optics and information, but also for the general physics community.

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Bogolubov, Nikolai N., and Andrey V. Soldatov. "Algebraic aspects of the driven dynamics in the density operator and correlation functions calculation for multi-level open quantum systems." International Journal of Modern Physics B 31, no. 32 (December 18, 2017): 1850044. http://dx.doi.org/10.1142/s0217979218500443.

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Exact and approximate master equations were derived by the projection operator method for the reduced statistical operator of a multi-level quantum system with finite number N of quantum eigenstates interacting with arbitrary external classical fields and dissipative environment simultaneously. It was shown that the structure of these equations can be simplified significantly if the free Hamiltonian driven dynamics of an arbitrary quantum multi-level system under the influence of the external driving fields as well as its Markovian and non-Markovian evolution, stipulated by the interaction with the environment, are described in terms of the SU(N) algebra representation. As a consequence, efficient numerical methods can be developed and employed to analyze these master equations for real problems in various fields of theoretical and applied physics. It was also shown that literally the same master equations hold not only for the reduced density operator but also for arbitrary nonequilibrium multi-time correlation functions as well under the only assumption that the system and the environment are uncorrelated at some initial moment of time. A calculational scheme was proposed to account for these lost correlations in a regular perturbative way, thus providing additional computable terms to the correspondent master equations for the correlation functions.

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Decker, Lukas, Daniel Förster, Frank Gauterin, and Martin Doppelbauer. "Physics-Based and Data-Enhanced Model for Electric Drive Sizing during System Design of Electrified Powertrains." Vehicles 3, no. 3 (August 8, 2021): 512–32. http://dx.doi.org/10.3390/vehicles3030031.

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In multi-drive electrified powertrains, the control strategy strongly influences the component load collectives. Due to this interdependency, the component sizing becomes a difficult task. This paper comprehensively analyses different electric drive system sizing methods for multi-drive systems in the literature. Based on this analysis, a new data-enhanced sizing approach is proposed. While the characteristic is depicted with a physics-based polynomial model, a data-enhanced limiting function ensures the parameter variation stays within a physically feasible range. Its beneficial value is demonstrated by applying the new model to a powertrain system optimization. The new approach enables a detailed investigation of the correlations between the characteristic of electric drive systems and the overall vehicle energy consumption for varying topologies. The application results demonstrate the accuracy and benefit of the proposed model.

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Sahu, Nandini, Alister Graham, and Benjamin Davis. "The Morphology-dependent Black Hole–Host Galaxy Correlations: A Consequence of Physical Formation Processes." Acta Astrophysica Taurica 3, no. 1 (December 2, 2021): 39–43. http://dx.doi.org/10.31059/aat.vol3.iss1.pp39-43.

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For decades, astronomers have been investigating how the central supermassive black hole (BH) may govern the host galaxy’s properties and vice versa. Our work adds another step to this study. We have performed state-of-theart 2D modeling and multi-component photometric decompositions of the largest-to-date sample of galaxies with dynamically-measured black hole masses (MBH). The multi-component decomposition allows us to accurately extract the bulge (spheroid) stellar luminosity/mass and structural parameters (also for other galaxy components) and provides detailed galaxy morphologies. We investigated the correlations between MBH and various host galaxy properties, including the bulge (M*,sph) and total galaxy (M*,gal) stellar masses discussed here. Importantly, we analyzed the role of galaxy morphology in these correlations. Our work reveals that the BH scaling relations depend on galaxy morphology and thus depend on the galaxy’s formation and evolution physics. Here we discuss that in the MBH–M*,sph diagram, early-type galaxies (ETGs) with a disk, ETGs without a disk, and late-type galaxies (LTG-spirals) define distinct relations, with quadratic slopes but different zero-points. We also review the MBH–M*,gal relation, where ETGs and LTGs define different relations. Notably, the existence of the MBH–M*,gal relations enables one to quickly estimate MBH in other galaxies without going through the multi-component decomposition process to obtain M*,sph. The final morphology-dependent black hole scaling relations provide tests for morphology-aware simulations of galaxies with a central BH and hold insights for BH-galaxy co-evolution theories based on BH accretion and feedback.

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Meier, S., J. Heimerl, and P. Hommelhoff. "Correlations in strong-field-emitted ultrashort electron pulses from metal needle tips." Laser Physics Letters 21, no. 4 (February 29, 2024): 045301. http://dx.doi.org/10.1088/1612-202x/ad2b5a.

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Abstract When two electrons are emitted from a metal needle tip with the help of femtosecond laser pulses, they show a strong anticorrelation signal in the energy domain. Depending on the wavelength and intensity of the driving laser pulses, the electron emission process can be either in a perturbative regime, like single- or multi-photon photoemission, or in the strong-field regime, where emission is dominated by the instantaneous electric field of the laser pulse, or in the intermediate regime. Here, we report on the two-electron anticorrelation signal and how it evolves from the multiphoton toward the strong-field emission regime. We show that in both cases, the resulting anticorrelation signal can be well explained by semi-classical simulations using a point-particle model, thus the dynamics is dominated by the center-of-mass dynamics of the individual electrons. However, the actual emission process of multiple interacting electrons requires improved quantum mechanical models and therefore remains the subject of future work. This paper is part of the Special Topic Collection: papers from the 31th Annual International Laser Physics Workshop 2023 (LPHYS 2023).

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Lukins, James, Roger Tribe, and Oleg Zaboronski. "Multi-point correlations for two-dimensional coalescing or annihilating random walks." Journal of Applied Probability 55, no. 4 (December 2018): 1158–85. http://dx.doi.org/10.1017/jpr.2018.77.

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Abstract In this paper we consider an infinite system of instantaneously coalescing rate 1 simple symmetric random walks on ℤ2, started from the initial condition with all sites in ℤ2 occupied. Two-dimensional coalescing random walks are a `critical' model of interacting particle systems: unlike coalescence models in dimension three or higher, the fluctuation effects are important for the description of large-time statistics in two dimensions, manifesting themselves through the logarithmic corrections to the `mean field' answers. Yet the fluctuation effects are not as strong as for the one-dimensional coalescence, in which case the fluctuation effects modify the large time statistics at the leading order. Unfortunately, unlike its one-dimensional counterpart, the two-dimensional model is not exactly solvable, which explains a relative scarcity of rigorous analytic answers for the statistics of fluctuations at large times. Our contribution is to find, for any N≥2, the leading asymptotics for the correlation functions ρN(x1,…,xN) as t→∞. This generalises the results for N=1 due to Bramson and Griffeath (1980) and confirms a prediction in the physics literature for N>1. An analogous statement holds for instantaneously annihilating random walks. The key tools are the known asymptotic ρ1(t)∼logt∕πt due to Bramson and Griffeath (1980), and the noncollision probability 𝒑NC(t), that no pair of a finite collection of N two-dimensional simple random walks meets by time t, whose asymptotic 𝒑NC(t)∼c0(logt)-(N2) was found by Cox et al. (2010). We re-derive the asymptotics, and establish new error bounds, both for ρ1(t) and 𝒑NC(t) by proving that these quantities satisfy effective rate equations; that is, approximate differential equations at large times. This approach can be regarded as a generalisation of the Smoluchowski theory of renormalised rate equations to multi-point statistics.

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SANCHIS-LOZANO, MIGUEL-ANGEL. "PROSPECTS OF SEARCHING FOR (UN)PARTICLES FROM HIDDEN SECTORS USING RAPIDITY CORRELATIONS IN MULTIPARTICLE PRODUCTION AT THE LHC." International Journal of Modern Physics A 24, no. 24 (September 30, 2009): 4529–72. http://dx.doi.org/10.1142/s0217751x09045820.

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Most signatures of new physics have been studied on the transverse plane with respect to the beam direction at the LHC where background is much reduced. In this paper we propose the analysis of inclusive longitudinal (pseudo)rapidity correlations among final-state (charged) particles in order to search for (un)particles belonging to a hidden sector beyond the Standard Model, using a selected sample of p–p minimum bias events (applying appropriate off-line cuts on events based on, e.g. minijets, high-multiplicity, event shape variables, high-p⊥ leptons and photons, etc.) collected at the early running of the LHC. To this aim, we examine inclusive and semi-inclusive two-particle correlation functions, forward–backward correlations, and factorial moments of the multiplicity distribution, without resorting to any particular model but under very general (though simplifying) assumptions. Finally, motivated by some analysis techniques employed in the search for quark–gluon plasma in heavy-ion collisions, we investigate the impact of such intermediate (un)particle stuff on the (multi)fractality of parton cascades in p–p collisions, by means of a Lévy stable law description and a Ginzburg–Landau model of phase transitions. Results from our preliminary study seem encouraging for possible dedicated analyses at LHC and Tevatron experiments.

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Barrett, Alexander, and Preston Jones. "Second Order Glauber Correlation of Gravitational Waves Using the LIGO Observatories as Hanbury Brown and Twiss Detectors." Physical Sciences Forum 2, no. 1 (March 19, 2021): 25. http://dx.doi.org/10.3390/ecu2021-09519.

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The second order Glauber correlation of a simplified gravitational wave is investigated, using parameters from the first signal detected by LIGO. This simplified model spans the inspiral, merger, and ringdown phases of a black hole merger and was created to have a continuous amplitude, so there is no discontinuity between the phases. This allows for a trivial extraction of the intensity, which is necessary for determining the correlation between detectors. The two LIGO observatories can be used as detectors in a Hanbury Brown and Twiss interferometer for gravitational waves; these observatories measure the amplitude of the wave, so these measurements were used as the basis of the simplified model. The signal detected by the observatories is transient and is not consistent with chaotic or steady electromagnetic waves and thus the second order Glauber correlation function was calculated to produce physically meaningful results. To find correlations that are consistent with applications to electromagnetic waves, weighting functions for both models were studied in the integral equations for the Glauber correlation functions. The relationship between the transient and chaotic signals of both waveforms and their respective correlation functions was also examined. The second order Glauber correlation functions are a measure of intensity interference between independent detectors and has proven to be useful in both optics and particle physics. It has also been used in theoretical studies of primordial gravitational waves. The correlations can be used to define the degrees of coherence of a field, characterize multi-particle processes and assist in image enhancement.

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KROTSCHECK, E., H. M. BÖHM, and K. SCHÖRKHUBER. "TWO–PARTICLE–TWO–HOLE EXCITATIONS IN 3He." International Journal of Modern Physics B 20, no. 19 (July 30, 2006): 2657–66. http://dx.doi.org/10.1142/s021797920603514x.

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We describe the development of a systematic theory of excitations in strongly interacting Fermi systems. Technically, we derive the equations of motion for multi–pair excitations from a stationarity principle. This method has, in Fermi systems, so far been developed only to the level of one–particle–one–hole excitations, where it leads to the (correlated) random phase approximation (RPA). We extend the analysis here to pair excitations. Our work is motivated by the fact that time–dependent pair correlations are necessary for explaining the physics of the phonon–roton spectrum in 4 He . It is therefore plausible that the same processes also have visible effects in the excitation spectrum of 3 He . Further motivation is derived from recent measurements of the dynamic structure function in two–dimensional 3 He . We first formulate the theory for a second quantized, weakly interacting Hamiltonian and then generalize the theory to a correlated ground state. We show that the inclusion of Jastrow–Feenberg type correlations leads to prescriptions for calculating weak effective interactions from a microscopic, strongly interacting Hamiltonian.

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Yu, Xie-Hang, Zhiyuan Wang, and Pavel Kos. "Hierarchical generalization of dual unitarity." Quantum 8 (February 20, 2024): 1260. http://dx.doi.org/10.22331/q-2024-02-20-1260.

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Quantum dynamics with local interactions in lattice models display rich physics, but is notoriously hard to study. Dual-unitary circuits allow for exact answers to interesting physical questions in clean or disordered one- and higher-dimensional quantum systems. However, this family of models shows some non-universal features, like vanishing correlations inside the light-cone and instantaneous thermalization of local observables. In this work we propose a generalization of dual-unitary circuits where the exactly calculable spatial-temporal correlation functions display richer behavior, and have non-trivial thermalization of local observables. This is achieved by generalizing the single-gate condition to a hierarchy of multi-gate conditions, where the first level recovers dual-unitary models, and the second level exhibits these new interesting features. We also extend the discussion and provide exact solutions to correlators with few-site observables and discuss higher-orders, including the ones after a quantum quench. In addition, we provide exhaustive parametrizations for qubit cases, and propose a new family of models for local dimensions larger than two, which also provides a new family of dual-unitary models.

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Senger, Peter. "Status of the Compressed Baryonic Matter experiment at FAIR." International Journal of Modern Physics E 29, no. 02 (February 2020): 2030001. http://dx.doi.org/10.1142/s0218301320300015.

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The Compressed Baryonic Matter (CBM) experiment will investigate high-energy heavy-ion collisions at the international Facility for Antiproton and Ion Research (FAIR), which is under construction in Darmstadt, Germany. The CBM research program is focused on the exploration of QCD matter at neutron star core densities, such as study of the equation-of-state and the search for phase transitions. Key experimental observables include (multi-) strange (anti-) particles, electron-positron pairs and dimuons, particle correlations and fluctuations, and hyper-nuclei. In order to measure these diagnostic probes multi-differentially with unprecedented precision, the CBM detector and data acquisition systems are designed to run at reaction rates up to 10 MHz. This requires the development of fast and radiation hard detectors and readout electronics for track reconstruction, electron and muon identification, time-of-flight (TOF) determination and event characterization. The data are read-out by ultra-fast, radiation-tolerant, and free-streaming front-end electronics, and then transferred via radiation-hard data aggregation units and high-speed optical connections to a high-performance computing center. A fast and highly parallelized software will perform online track reconstruction, particle identification and event analysis. The components of the CBM experimental setup will be discussed and results of physics performance studies will be presented.

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Alfonso, Lester, Graciela B. Raga, and Darrel Baumgardner. "The impact of fluctuations and correlations in droplet growth by collision–coalescence revisited – Part 2: Observational evidence of gel formation in warm clouds." Atmospheric Chemistry and Physics 19, no. 23 (December 10, 2019): 14917–32. http://dx.doi.org/10.5194/acp-19-14917-2019.

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Abstract. In recent papers (Alfonso et al., 2013; Alfonso and Raga, 2017) the sol–gel transition was proposed as a mechanism for the formation of large droplets required to trigger warm rain development in cumulus clouds. In the context of cloud physics, gelation can be interpreted as the formation of the “lucky droplet” that grows by accretion of smaller droplets at a much faster rate than the rest of the population and becomes the embryo for raindrops. However, all the results in this area have been theoretical or simulation studies. The aim of this paper is to find some observational evidence of gel formation in clouds by analyzing the distribution of the largest droplet at an early stage of cloud formation and to show that the mass of the gel (largest drop) is a mixture of a Gaussian distribution and a Gumbel distribution, in accordance with the pseudo-critical clustering scenario described in Gruyer et al. (2013) for nuclear multi-fragmentation.

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Kumar, Pinaki, Roberto Benzi, Jeannot Trampert, and Federico Toschi. "A multi-component lattice Boltzmann approach to study the causality of plastic events." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, no. 2175 (June 22, 2020): 20190403. http://dx.doi.org/10.1098/rsta.2019.0403.

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Using a multi-component lattice Boltzmann (LB) model, we perform fluid kinetic simulations of confined and concentrated emulsions. The system presents the phenomenology of soft-glassy materials, including a Herschel–Bulkley rheology, yield stress, ageing and long relaxation time scales. Shearing the emulsion in a Couette cell below the yield stress results in plastic topological re-arrangement events which follow established empirical seismic statistical scaling laws, making this system a good candidate to study the physics of earthquakes. One characteristic of this model is the tendency for events to occur in avalanche clusters, with larger events, triggering subsequent re-arrangements. While seismologists have developed statistical tools to study correlations between events, a process to confirm causality remains elusive. We present here, a modification to our LB model, involving small, fast vibrations applied to individual droplets, effectively a macroscopic forcing, which results in the arrest of the topological plastic re-arrangements. This technique provides an excellent tool for identifying causality in plastic event clusters by examining the evolution of the dynamics after ‘stopping’ an event, and then checking which subsequent events disappear. This article is part of the theme issue ‘Fluid dynamics, soft matter and complex systems: recent results and new methods’.

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Kondrashov, D., and M. Ghil. "Spatio-temporal filling of missing points in geophysical data sets." Nonlinear Processes in Geophysics 13, no. 2 (May 24, 2006): 151–59. http://dx.doi.org/10.5194/npg-13-151-2006.

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Abstract. The majority of data sets in the geosciences are obtained from observations and measurements of natural systems, rather than in the laboratory. These data sets are often full of gaps, due to to the conditions under which the measurements are made. Missing data give rise to various problems, for example in spectral estimation or in specifying boundary conditions for numerical models. Here we use Singular Spectrum Analysis (SSA) to fill the gaps in several types of data sets. For a univariate record, our procedure uses only temporal correlations in the data to fill in the missing points. For a multivariate record, multi-channel SSA (M-SSA) takes advantage of both spatial and temporal correlations. We iteratively produce estimates of missing data points, which are then used to compute a self-consistent lag-covariance matrix; cross-validation allows us to optimize the window width and number of dominant SSA or M-SSA modes to fill the gaps. The optimal parameters of our procedure depend on the distribution in time (and space) of the missing data, as well as on the variance distribution between oscillatory modes and noise. The algorithm is demonstrated on synthetic examples, as well as on data sets from oceanography, hydrology, atmospheric sciences, and space physics: global sea-surface temperature, flood-water records of the Nile River, the Southern Oscillation Index (SOI), and satellite observations of relativistic electrons.

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Sinclair, Kenneth, Bastiaan van Diedenhoven, Brian Cairns, John Yorks, Andrzej Wasilewski, and Matthew McGill. "Remote sensing of multiple cloud layer heights using multi-angular measurements." Atmospheric Measurement Techniques 10, no. 6 (June 29, 2017): 2361–75. http://dx.doi.org/10.5194/amt-10-2361-2017.

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Abstract. Cloud top height (CTH) affects the radiative properties of clouds. Improved CTH observations will allow for improved parameterizations in large-scale models and accurate information on CTH is also important when studying variations in freezing point and cloud microphysics. NASA's airborne Research Scanning Polarimeter (RSP) is able to measure cloud top height using a novel multi-angular contrast approach. For the determination of CTH, a set of consecutive nadir reflectances is selected and the cross correlations between this set and collocated sets at other viewing angles are calculated for a range of assumed cloud top heights, yielding a correlation profile. Under the assumption that cloud reflectances are isotropic, local peaks in the correlation profile indicate cloud layers. This technique can be applied to every RSP footprint and we demonstrate that detection of multiple peaks in the correlation profile allows retrieval of heights of multiple cloud layers within single RSP footprints. This paper provides an in-depth description of the architecture and performance of the RSP's CTH retrieval technique using data obtained during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) campaign. RSP-retrieved cloud heights are evaluated using collocated data from the Cloud Physics Lidar (CPL). The method's accuracy associated with the magnitude of correlation, optical thickness, cloud thickness and cloud height are explored. The technique is applied to measurements at a wavelength of 670 and 1880 nm and their combination. The 1880 nm band is virtually insensitive to the lower troposphere due to strong water vapor absorption. It is found that each band is well suitable for retrieving heights of cloud layers with optical thicknesses above about 0.1 and that RSP cloud layer height retrievals more accurately correspond to CPL cloud middle than cloud top. It is also found that the 1880 nm band yields the most accurate results for clouds at middle and high altitudes (4.0 to 17 km), while the 670 nm band is most accurate at low and middle altitudes (1.0–13.0 km). The dual band performs best over the broadest range and is suitable for accurately retrieving cloud layer heights between 1.0 and 16.0 km. Generally, the accuracy of the retrieved cloud top heights increases with increasing correlation value. Improved accuracy is achieved by using customized filtering techniques for each band with the most significant improvements occurring in the primary layer retrievals. RSP is able to measure a primary layer CTH with a median error of about 0.5 km when compared to CPL. For multilayered scenes, the second and third layer heights are determined median errors of about 1.5 and 2.0–2.5 km, respectively.

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Aurell, Erik, Michał Eckstein, and Paweł Horodecki. "Hawking radiation and the quantum marginal problem." Journal of Cosmology and Astroparticle Physics 2022, no. 01 (January 1, 2022): 014. http://dx.doi.org/10.1088/1475-7516/2022/01/014.

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Abstract In 1974 Steven Hawking showed that black holes emit thermal radiation, which eventually causes them to evaporate. The problem of the fate of information in this process is known as the “black hole information paradox”. Two main types of resolution postulate either a fundamental loss of information in Nature — hence the breakdown of quantum mechanics — or some sort of new physics, e.g. quantum gravity, which guarantee the global preservation of unitarity. Here we explore the second possibility with the help of recent developments in continuous-variable quantum information. Concretely, we employ the solution to the Gaussian quantum marginal problem to show that the thermality of all individual Hawking modes is consistent with a global pure state of the radiation. Surprisingly, we find out that the mods of radiation of an astrophysical black hole are thermal until the very last burst. In contrast, the single-mode thermality of Hawking radiation originating from microscopic black holes, expected to evaporate through several quanta, is not excluded, though there are constraints on modes' frequencies. Our result paves the way towards a systematic study of multi-mode correlations in Hawking radiation.

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Bhagat, Kunal, and Shiva Rudraraju. "A Numerical Investigation of Dimensionless Numbers Characterizing Meltpool Morphology of the Laser Powder Bed Fusion Process." Materials 16, no. 1 (December 22, 2022): 94. http://dx.doi.org/10.3390/ma16010094.

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Microstructure evolution in metal additive manufacturing (AM) is a complex multi-physics and multi-scale problem. Understanding the impact of AM process conditions on the microstructure evolution and the resulting mechanical properties of the printed component remains an active area of research. At the meltpool scale, the thermo-fluidic governing equations have been extensively modeled in the literature to understand the meltpool conditions and the thermal gradients in its vicinity. In many phenomena governed by partial differential equations, dimensional analysis and identification of important dimensionless numbers can provide significant insights into the process dynamics. In this context, we present a novel strategy using dimensional analysis and the linear least-squares regression method to numerically investigate the thermo-fluidic governing equations of the Laser Powder Bed Fusion AM process. First, the governing equations are solved using the Finite Element Method, and the model predictions are validated by comparing with experimentally estimated cooling rates, and with numerical results from the literature. Then, through dimensional analysis, an important dimensionless quantity interpreted as a measure of heat absorbed by the powdered material and the meltpool, is identified. This dimensionless measure of absorbed heat, along with classical dimensionless quantities such as Péclet, Marangoni, and Stefan numbers, are employed to investigate advective transport in the meltpool for different alloys. Further, the framework is used to study variations in the thermal gradients and the solidification cooling rate. Important correlations linking meltpool morphology and microstructure-evolution-related variables with classical dimensionless numbers are the key contribution of this work.

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Liu, Yuan, Ravi Ravichandran, Kuiying Chen, and Prakash Patnaik. "Application of Machine Learning to Solid Particle Erosion of APS-TBC and EB-PVD TBC at Elevated Temperatures." Coatings 11, no. 7 (July 13, 2021): 845. http://dx.doi.org/10.3390/coatings11070845.

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Machine learning (ML) and deep learning (DL) for big data (BD) management are currently viable approaches that can significantly help in high-temperature materials design and development. ML-DL can accumulate knowledge by learning from existing data generated through multi-physics modelling (MPM) and experimental tests (ETs). DL mainly involves analyzing nonlinear correlations and high-dimensional datasets implemented through specifically designed numerical algorithms. DL also makes it possible to learn from new data and modify predictive models over time, identifying anomalies, signatures, and trends in machine performance, develop an understanding of patterns of behaviour, and estimate efficiencies in a machine. Machine learning was implemented to investigate the solid particle erosion of both APS (air plasma spray) and EB-PVD (electron beam physical vapour deposition) TBCs of hot section components. Several ML models and algorithms were used such as neural networks (NNs), gradient boosting regression (GBR), decision tree regression (DTR), and random forest regression (RFR). It was found that the test data are strongly associated with five key factors as identifiers. Following test data collection, the dataset is subjected to sorting, filtering, extracting, and exploratory analysis. The training and testing, and prediction results are analysed. The results suggest that neural networks using the BR model and GBR have better prediction capability.

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Sairajan, K. K., G. S. Aglietti, and Scott J. I. Walker. "Correlation of finite element models of multi-physics systems." Journal of Sound and Vibration 333, no. 17 (August 2014): 4051–70. http://dx.doi.org/10.1016/j.jsv.2014.04.010.

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Santos, Andrés, and Jarosław Piasecki. "Multi-particle critical correlations." Molecular Physics 113, no. 17-18 (March 19, 2015): 2855–62. http://dx.doi.org/10.1080/00268976.2015.1021397.

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Kabra, Venkatesh, Ishita Kamboj, Veronica Augustyn, and Partha P. Mukherjee. "Data Driven Model for Lithium-Ion Battery Electrode Microstructure Property Estimation." ECS Meeting Abstracts MA2022-02, no. 3 (October 9, 2022): 176. http://dx.doi.org/10.1149/ma2022-023176mtgabs.

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Li-ion batteries (LIB) are ubiquitous in today’s world with applications ranging from portable electronic devices to electric vehicles. These set of applications require the batteries to have diverse energy and power dense configurations. For these reasons the LIB exists in multiple form factors such as cylindrical, pouch cell configurations and different chemistries. The most commercialized and successful LIB are based on intercalation mechanism, which requires shuttling of Li-ion between anode and cathode with redox reaction occurring on the surface of the electrodes and ultimately leading to the Li-ions to diffuse into the host structure of the electrode. Such electrodes are naturally made to be porous, to maximize the surface area for redox and electrochemical reaction, also giving rise to multiple pathways for Li-ion diffusion and migration. These electrode structures are also integrated with additives to increase the electronic conductivity and mechanical strength. This gives rise to the microstructure as a matrix of different phases with multi-length scale structure and characteristics at different scales. The performance and operation of battery is closely intertwined with these electrode microstructure, and thus microstructural characteristics significantly influence the transport process or kinetics of the reaction. This relation between performance and electrode microstructure is not limited to the composition of electrode rather even with fixed chemical composition the widely different structural arrangement of the phases alters the short- and long-range interactions within the electrode. Specifically based on electrochemical performance model, the electrochemical-thermal interactions can be captured with few important effective electrode properties such as interfacial area, tortuosity and conductivity. Here we develop a framework for the accurate prediction of these effective electrode properties as a function of the microstructural properties. For this purpose of effective electrode property prediction, we develop an integrated framework, including information from the physics informed mesoscale model along with the data driven models. The accurate effective electrode properties are evaluated from pore-scale characterization of microstructure, to serve as output for data set. Our main objective with developing such a framework is to describe the effective electrode properties with simple yet meaningful correlations, which can accurately capture physics while maintaining high predictive accuracy, thus also providing directions for better electrode manufacturing.

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Snoll, Brooke, Ruza Ivanovic, Lauren Gregoire, Sam Sherriff-Tadano, Laurie Menviel, Takashi Obase, Ayako Abe-Ouchi, et al. "A multi-model assessment of the early last deglaciation (PMIP4 LDv1): a meltwater perspective." Climate of the Past 20, no. 4 (April 5, 2024): 789–815. http://dx.doi.org/10.5194/cp-20-789-2024.

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Abstract. The last deglaciation (∼20–11 ka BP) is a period of a major, long-term climate transition from a glacial to interglacial state that features multiple centennial- to decadal-scale abrupt climate variations whose root cause is still not fully understood. To better understand this time period, the Paleoclimate Modelling Intercomparison Project (PMIP) has provided a framework for an internationally coordinated endeavour in simulating the last deglaciation whilst encompassing a broad range of models. Here, we present a multi-model intercomparison of 17 transient simulations of the early part of the last deglaciation (∼20–15 ka BP) from nine different climate models spanning a range of model complexities and uncertain boundary conditions and forcings. The numerous simulations available provide the opportunity to better understand the chain of events and mechanisms of climate changes between 20 and 15 ka BP and our collective ability to simulate them. We conclude that the amount of freshwater forcing and whether it follows the ice sheet reconstruction or induces an inferred Atlantic meridional overturning circulation (AMOC) history, heavily impacts the deglacial climate evolution for each simulation rather than differences in the model physics. The course of the deglaciation is consistent between simulations except when the freshwater forcing is above 0.1 Sv – at least 70 % of the simulations agree that there is warming by 15 ka BP in most places excluding the location of meltwater input. For simulations with freshwater forcings that exceed 0.1 Sv from 18 ka BP, warming is delayed in the North Atlantic and surface air temperature correlations with AMOC strength are much higher. However, we find that the state of the AMOC coming out of the Last Glacial Maximum (LGM) also plays a key role in the AMOC sensitivity to model forcings. In addition, we show that the response of each model to the chosen meltwater scenario depends largely on the sensitivity of the model to the freshwater forcing and other aspects of the experimental design (e.g. CO2 forcing or ice sheet reconstruction). The results provide insight into the ability of our models to simulate the first part of the deglaciation and how choices between uncertain boundary conditions and forcings, with a focus on freshwater fluxes, can impact model outputs. We can use these findings as helpful insight in the design of future simulations of this time period.

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Adamska, L. V., and A. M. Gavrilik. "Multi-particle correlations inqp-Bose gas model." Journal of Physics A: Mathematical and General 37, no. 17 (April 15, 2004): 4787–95. http://dx.doi.org/10.1088/0305-4470/37/17/009.

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Bianchet, Lorena C., Natalia Alves, Laura Zarraoa, Natalia Bruno, and Morgan W. Mitchell. "Manipulating and measuring single atoms in the Maltese cross geometry." Open Research Europe 1 (September 6, 2021): 102. http://dx.doi.org/10.12688/openreseurope.13972.1.

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Background: Optical microtraps at the focus of high numerical aperture (high-NA) imaging systems enable efficient collection, trapping, detection and manipulation of individual neutral atoms for quantum technology and studies of optical physics associated with super- and sub-radiant states. The recently developed “Maltese cross” geometry (MCG) atom trap uses four in-vacuum lenses to achieve four-directional high-NA optical coupling to single trapped atoms and small atomic arrays. This article presents the first extensive characterisation of atomic behaviour in a MCG atom trap. Methods: We employ a MCG system optimised for high coupling efficiency and characterise the resulting properties of the trap and trapped atoms. Using current best practices, we measure occupancy, loading rate, lifetime, temperature, fluorescence anti-bunching and trap frequencies. We also use the four-directional access to implement a new method to map the spatial distribution of collection efficiency from high-NA optics: we use the two on-trap-axis lenses to produce a 1D optical lattice, the sites of which are stochastically filled and emptied by the trap loading process. The two off-trap-axis lenses are used for imaging and single-mode collection. Correlations of single-mode and imaging fluorescence signals are then used to map the single-mode collection efficiency. Results: We observe trap characteristics comparable to what has been reported for single-atom traps with one- or two-lens optical systems. The collection efficiency distribution in the axial and transverse directions is directly observed to be in agreement with expected collection efficiency distribution from Gaussian beam optics. Conclusions: The multi-directional high-NA access provided by the Maltese cross geometry enables complex manipulations and measurements not possible in geometries with fewer directions of access, and can be achieved while preserving other trap characteristics such as lifetime, temperature, and trap size.

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Bianchet, Lorena C., Natalia Alves, Laura Zarraoa, Natalia Bruno, and Morgan W. Mitchell. "Manipulating and measuring single atoms in the Maltese cross geometry." Open Research Europe 1 (March 3, 2022): 102. http://dx.doi.org/10.12688/openreseurope.13972.2.

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Background: Optical microtraps at the focus of high numerical aperture (high-NA) imaging systems enable efficient collection, trapping, detection and manipulation of individual neutral atoms for quantum technology and studies of optical physics associated with super- and sub-radiant states. The recently developed “Maltese cross” geometry (MCG) atom trap uses four in-vacuum lenses to achieve four-directional high-NA optical coupling to single trapped atoms and small atomic arrays. This article presents the first extensive characterisation of atomic behaviour in a MCG atom trap. Methods: We employ a MCG system optimised for high coupling efficiency and characterise the resulting properties of the trap and trapped atoms. Using current best practices, we measure occupancy, loading rate, lifetime, temperature, fluorescence anti-bunching and trap frequencies. We also use the four-directional access to implement a new method to map the spatial distribution of collection efficiency from high-NA optics: we use the two on-trap-axis lenses to produce a 1D optical lattice, the sites of which are stochastically filled and emptied by the trap loading process. The two off-trap-axis lenses are used for imaging and single-mode collection. Correlations of single-mode and imaging fluorescence signals are then used to map the single-mode collection efficiency. Results: We observe trap characteristics comparable to what has been reported for single-atom traps with one- or two-lens optical systems. The collection efficiency distribution in the axial and transverse directions is directly observed to be in agreement with expected collection efficiency distribution from Gaussian beam optics. Conclusions: The multi-directional high-NA access provided by the Maltese cross geometry enables complex manipulations and measurements not possible in geometries with fewer directions of access, and can be achieved while preserving other trap characteristics such as lifetime, temperature, and trap size.

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Chiorean, Radu, Mircea Cristian Dudescu, Marius Pustan, and Mihail Hărdău. "V-Beam Thermal Actuator’s Performance Analysis Using Digital Image Correlation." Applied Mechanics and Materials 658 (October 2014): 173–76. http://dx.doi.org/10.4028/www.scientific.net/amm.658.173.

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This paper analyses the influence of the V-beam thermal actuator’s geometrical parameters on its mechanical behavior. Experimental measurements were performed using Digital Image Correlation (DIC), which is a gray scale value tracking algorithm that evaluates the position shift of a pixel between at least two images taken at different deformation stages. These results are compared to multi-physics simulation data obtained using Finite Element Analysis (FEA) as well as to analytical values based on the electro-thermal and thermo-mechanical presented models.

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Ludwig, Patrick, Hauke Thomsen, Karsten Balzer, Alexei Filinov, and Michael Bonitz. "Tuning correlations in multi-component plasmas." Plasma Physics and Controlled Fusion 52, no. 12 (November 15, 2010): 124013. http://dx.doi.org/10.1088/0741-3335/52/12/124013.

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Mishra, Aashwin A., and Sharath S. Girimaji. "Intercomponent energy transfer in incompressible homogeneous turbulence: multi-point physics and amenability to one-point closures." Journal of Fluid Mechanics 731 (August 28, 2013): 639–81. http://dx.doi.org/10.1017/jfm.2013.343.

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AbstractIntercomponent energy transfer (IET) is a direct consequence of the incompressibility-preserving action of pressure. This action of pressure is inherently non-local, and consequently its modelling must address multi-point physics. However, in second moment closures, pragmatism mandates a single-point closure model for the pressure–strain correlation, that is, the source of IET. In this study, we perform a rapid distortion analysis to demonstrate that for a given mean-flow gradient, IET is strongly dependent on fluctuation modes and critically influences the flow stability, asymptotic states and their bifurcations. The inference is that multi-point physics must be characterized and appropriately incorporated into pressure–strain correlation closures. To this end, we analyse and categorize various multi-point characteristics such as: (i) the fluctuation mode wavevector dynamics; (ii) the spectral space topology of dominant modes; and (iii) the range of IET behaviour and statistically most likely (SML) outcomes. Thence, this characterization is used to examine the validity and limitations of current one-point closures and to propose directions for improving the fidelity of future models.

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Amelin, Nikolai, and Richard Lednicky. "Multi-Boson correlations and classical transport models." Acta Physica Hungarica A) Heavy Ion Physics 4, no. 1-4 (December 1996): 241–47. http://dx.doi.org/10.1007/bf03155619.

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Rajesh, R. "Multi-avalanche correlations in directed sandpile models." EPL (Europhysics Letters) 85, no. 1 (January 2009): 10001. http://dx.doi.org/10.1209/0295-5075/85/10001.

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Klobas, Katja, Matthieu Vanicat, Juan P. Garrahan, and Tomaž Prosen. "Matrix product state of multi-time correlations." Journal of Physics A: Mathematical and Theoretical 53, no. 33 (July 31, 2020): 335001. http://dx.doi.org/10.1088/1751-8121/ab8c62.

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Paz-Silva, Gerardo A., and John H. Reina. "Total correlations as multi-additive entanglement monotones." Journal of Physics A: Mathematical and Theoretical 42, no. 5 (January 6, 2009): 055306. http://dx.doi.org/10.1088/1751-8113/42/5/055306.

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VanderKam, Jeffrey M. "Correlations of Eigenvalues on¶Multi-Dimensional Flat Tori." Communications in Mathematical Physics 210, no. 1 (March 1, 2000): 203–23. http://dx.doi.org/10.1007/s002200050777.

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ANDRIES, JOHAN, FABIO BENATTI, MIEKE De COCK, and MARK FANNES. "MULTI-TIME CORRELATIONS IN RELAXING QUANTUM DYNAMICAL SYSTEMS." Reviews in Mathematical Physics 12, no. 07 (July 2000): 921–44. http://dx.doi.org/10.1142/s0129055x00000356.

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In this paper, we consider the long time asymptotics of multi-time correlation functions for quantum dynamical systems that are sufficiently random to relax to a reference state. In particular, the evolution of such systems must have a continuous spectrum. Special attention is paid to general dynamical clustering conditions and their consequences for the structure of fluctuations of temporal averages. This approach is applied to the so-called Powers–Price shifts.

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Delipei, Gregory K., Pascal Rouxelin, Agustin Abarca, Jason Hou, Maria Avramova, and Kostadin Ivanov. "CTF-PARCS Core Multi-Physics Computational Framework for Efficient LWR Steady-State, Depletion and Transient Uncertainty Quantification." Energies 15, no. 14 (July 19, 2022): 5226. http://dx.doi.org/10.3390/en15145226.

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Best Estimate Plus Uncertainty (BEPU) approaches for nuclear reactor applications have been extensively developed in recent years. The challenge for BEPU approaches is to achieve multi-physics modeling with an acceptable computational cost while preserving a reasonable fidelity of the physics modeled. In this work, we present the core multi-physics computational framework developed for the efficient computation of uncertainties in Light Water Reactor (LWR) simulations. The subchannel thermal-hydraulic code CTF and the nodal expansion neutronic code PARCS are coupled for the multi-physics modeling (CTF-PARCS). The computational framework is discussed in detail from the Polaris lattice calculations up to the CTF-PARCS coupling approaches. Sampler is used to perturb the multi-group microscopic cross-sections, fission yields and manufacturing parameters, while Dakota is used to sample the CTF input parameters and the boundary conditions. Python scripts were developed to automatize and modularize both pre- and post-processing. The current state of the framework allows the consistent perturbation of inputs across neutronics and thermal-hydraulics modeling. Improvements to the standard thermal-hydraulics modeling for such coupling approaches have been implemented in CTF to allow the usage of 3D burnup distribution, calculation of the radial power and the burnup profile, and the usage of Santamarina effective Doppler temperature. The uncertainty quantification approach allows the treatment of both scalar and functional quantities and can estimate correlation between the multi-physics outputs of interest and up to the originally perturbed microscopic cross-sections and yields. The computational framework is applied to three exercises of the LWR Uncertainty Analysis in Modeling Phase III benchmark. The exercises cover steady-state, depletion and transient calculations. The results show that the maximum fuel centerline temperature across all exercises is 2474K with 1.7% uncertainty and that the most correlated inputs are the 238U inelastic and elastic cross-sections above 1 MeV.

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Kim, Kisik. "Generation of multi-mode nonclassical correlations of light." Physica Scripta T151 (November 1, 2012): 014063. http://dx.doi.org/10.1088/0031-8949/2012/t151/014063.

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Yuri, Michiko. "Decay of correlations for certain multi-dimensional maps." Nonlinearity 9, no. 6 (November 1, 1996): 1439–61. http://dx.doi.org/10.1088/0951-7715/9/6/003.

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Flaccomio, E., G. Micela, S. Sciortino, A. M. Cody, M. G. Guarcello, M. Morales-Calderòn, L. Rebull, and J. R. Stauffer. "A multi-wavelength view of magnetic flaring from PMS stars." Astronomy & Astrophysics 620 (November 29, 2018): A55. http://dx.doi.org/10.1051/0004-6361/201833308.

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Context. Flaring is an ubiquitous manifestation of magnetic activity in low mass stars including, of course, the Sun. Although flares, both from the Sun and from other stars, are most prominently observed in the soft X-ray band, most of the radiated energy is released at optical/UV wavelengths. In spite of decades of investigation, the physics of flares, even solar ones, is not fully understood. Even less is known about magnetic flaring in pre-main sequence (PMS) stars, at least in part because of the lack of suitable multi-wavelength data. This is unfortunate since the energetic radiation from stellar flares, which is routinely observed to be orders of magnitude greater than in solar flares, might have a significant impact on the evolution of circumstellar, planet-forming disks. Aims. We aim at improving our understanding of flares from PMS stars. Our immediate objectives are constraining the relation between flare emission at X-ray, optical, and mid-infrared (mIR) bands, inferring properties of the optically emitting region, and looking for signatures of the interaction between flares and the circumstellar environment, i.e. disks and envelopes. This information might then serve as input for detailed models of the interaction between stellar atmospheres, circumstellar disks and proto-planets. Methods. Observations of a large sample of PMS stars in the NGC 2264 star forming region were obtained in December 2011, simultaneously with three space-borne telescopes, Chandra (X-rays), CoRoT (optical), and Spitzer (mIR), as part of the “Coordinated Synoptic Investigation of NGC 2264” (CSI-NGC 2264). Shorter Chandra and CoRoT observations were also obtained in March 2008. We analyzed the lightcurves obtained during the Chandra observations (∼300 ks and ∼60 ks in 2011 and 2008, respectively), to detect X-ray flares with an optical and/or mIR counterpart. From the three datasets we then estimated basic flare properties, such as emitted energies and peak luminosities. These were then compared to constrain the spectral energy distribution of the flaring emission and the physical conditions of the emitting regions. The properties of flares from stars with and without circumstellar disks were also compared to establish any difference that might be attributed to the presence of disks. Results. Seventy-eight X-ray flares (from 65 stars) with an optical and/or mIR counterpart were detected. The optical emission of flares (both emitted energy and peak flux) is found to correlate well with, and to be significantly larger than, the X-ray emission. The slopes of the correlations suggest that the difference becomes smaller for the most powerful flares. The mIR flare emission seems to be strongly affected by the presence of a circumstellar disk: flares from stars with disks have a stronger mIR emission with respect to stars without disks. This might be attributed to either a cooler temperature of the region emitting both the optical and mIR flux or, perhaps more likely, to the reprocessing of the optical (and X-ray) flare emission by the inner circumstellar disk, providing evidence for flare-induced disk heating.

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Bartolozzi, M., C. Mellen, T. Di Matteo, and T. Aste. "Multi-scale correlations in different futures markets." European Physical Journal B 58, no. 2 (July 2007): 207–20. http://dx.doi.org/10.1140/epjb/e2007-00216-2.

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Bálint, Péter, and Imre Péter Tóth. "Exponential Decay of Correlations in Multi-Dimensional Dispersing Billiards." Annales Henri Poincaré 9, no. 7 (October 17, 2008): 1309–69. http://dx.doi.org/10.1007/s00023-008-0389-1.

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Triantafyllopoulos, D. N. "Multi-gluon correlations in the Color Glass Condensate." Nuclear Physics A 910-911 (August 2013): 506–9. http://dx.doi.org/10.1016/j.nuclphysa.2012.12.100.

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Tajima, H., and P. Naidon. "Multi-body Correlations in SU(3) Fermi Gases." Journal of Low Temperature Physics 196, no. 1-2 (December 6, 2018): 163–69. http://dx.doi.org/10.1007/s10909-018-2104-z.

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Sui, Guo, Huajiao Li, Sida Feng, Xueyong Liu, and Meihui Jiang. "Correlations of stock price fluctuations under multi-scale and multi-threshold scenarios." Physica A: Statistical Mechanics and its Applications 490 (January 2018): 1501–12. http://dx.doi.org/10.1016/j.physa.2017.08.141.

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Nagy, M. I., and T. Csörgő. "Multi-boson correlations using wave-packets II." European Physical Journal Special Topics 155, no. 1 (March 2008): 115–22. http://dx.doi.org/10.1140/epjst/e2008-00595-0.

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Regenauer-Lieb, Klaus, Manman Hu, Christoph Schrank, Xiao Chen, Santiago Peña Clavijo, Ulrich Kelka, Ali Karrech, et al. "Cross-diffusion waves resulting from multiscale, multi-physics instabilities: theory." Solid Earth 12, no. 4 (April 16, 2021): 869–83. http://dx.doi.org/10.5194/se-12-869-2021.

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Abstract. We propose a multiscale approach for coupling multi-physics processes across the scales. The physics is based on discrete phenomena, triggered by local thermo-hydro-mechano-chemical (THMC) instabilities, that cause cross-diffusion (quasi-soliton) acceleration waves. These waves nucleate when the overall stress field is incompatible with accelerations from local feedbacks of generalized THMC thermodynamic forces that trigger generalized thermodynamic fluxes of another kind. Cross-diffusion terms in the 4×4 THMC diffusion matrix are shown to lead to multiple diffusional P and S wave equations as coupled THMC solutions. Uncertainties in the location of meso-scale material instabilities are captured by a wave-scale correlation of probability amplitudes. Cross-diffusional waves have unusual dispersion patterns and, although they assume a solitary state, do not behave like solitons but show complex interactions when they collide. Their characteristic wavenumber and constant speed define mesoscopic internal material time–space relations entirely defined by the coefficients of the coupled THMC reaction–cross-diffusion equations. A companion paper proposes an application of the theory to earthquakes showing that excitation waves triggered by local reactions can, through an extreme effect of a cross-diffusional wave operator, lead to an energy cascade connecting large and small scales and cause solid-state turbulence.

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Ali, S. "Test charge response and correlations in multi-ion plasmas." Physics of Plasmas 26, no. 5 (May 2019): 052102. http://dx.doi.org/10.1063/1.5098532.

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Zhang, Ping, Wanfu Gao, Juncheng Hu, and Yonghao Li. "Multi-Label Feature Selection Based on High-Order Label Correlation Assumption." Entropy 22, no. 7 (July 21, 2020): 797. http://dx.doi.org/10.3390/e22070797.

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Multi-label data often involve features with high dimensionality and complicated label correlations, resulting in a great challenge for multi-label learning. Feature selection plays an important role in multi-label learning to address multi-label data. Exploring label correlations is crucial for multi-label feature selection. Previous information-theoretical-based methods employ the strategy of cumulative summation approximation to evaluate candidate features, which merely considers low-order label correlations. In fact, there exist high-order label correlations in label set, labels naturally cluster into several groups, similar labels intend to cluster into the same group, different labels belong to different groups. However, the strategy of cumulative summation approximation tends to select the features related to the groups containing more labels while ignoring the classification information of groups containing less labels. Therefore, many features related to similar labels are selected, which leads to poor classification performance. To this end, Max-Correlation term considering high-order label correlations is proposed. Additionally, we combine the Max-Correlation term with feature redundancy term to ensure that selected features are relevant to different label groups. Finally, a new method named Multi-label Feature Selection considering Max-Correlation (MCMFS) is proposed. Experimental results demonstrate the classification superiority of MCMFS in comparison to eight state-of-the-art multi-label feature selection methods.

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Journal articles on the topic 'Multi-Physics correlations'

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