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Sebastian Baur

Publications and source records attributed to Sebastian Baur.

8 recordsLinked to original sources

Causal Local States: Scalable Simultaneous Causal Network Inference and Forecasting for Dynamical Systems

Machine learning methods predict many real-world systems with remarkable accuracy, but they are typically treated as black boxes that offer no insight into which interactions drive the dynamics. Causal discovery methods reconstruct the interaction network from observational data, but without regard to whether the inferred structure supports prediction. Existing approaches combining both tasks rely on a single global hyperparameter, such as a causal threshold or a fixed neighborhood size, which cannot recover the structure of heterogeneous systems. Here we introduce causal local states (CLS), a framework that simultaneously infers an approximate Granger-causal interaction network and forecasts the system dynamics. For each node independently, we select the smallest set of neighbors that allows a predictive model to forecast the node near-optimally, and the resulting neighborhoods are then combined for a forecast of the full system. On three benchmarks of increasing difficulty, we achieve reconstruction of the underlying networks with high fidelity and forecasts on par with a model that is supplied with the true network, providing a step toward explainable and scalable forecasting of complex systems.

cs.LG

Predicting two-dimensional spatiotemporal chaotic patterns with optimized high-dimensional hybrid reservoir computing

As an alternative approach for predicting complex dynamical systems where physics-based models are no longer reliable, reservoir computing (RC) has gained popularity. The hybrid approach is considered an interesting option for improving the prediction performance of RC. The idea is to combine a knowledge-based model (KBM) to support the fully data-driven RC prediction. There are three types of hybridization for RC, namely full hybrid (FH), input hybrid (IH) and output hybrid (OH), where it was shown that the latter one is superior in terms of the accuracy and the robustness for the prediction of low-dimensional chaotic systems. Here, we extend the formalism to the prediction of spatiotemporal patterns in two dimensions. To overcome the curse of dimensionality for this very high-dimensional case we employ the local states ansatz, where only a few locally adjacent time series are utilized for the RC-based prediction. Using simulation data from the Barkley model describing chaotic electrical wave propagation in cardiac tissue, we outline the formalism of high-dimensional hybrid RC and assess the performance of the different hybridization schemes. We find that all three methods (FH, IH and OH) perform better than reservoir only, where improvements are small when the model is very inaccurate. For small model errors and small reservoirs FH and OH perform nearly equally well and better than IH. Given the smaller CPU needs for OH and especially the better interpretability of it, OH is to be favored. For large reservoirs the performance of OH drops below that of FH and IH. Generally, it maybe advisable to test the three setups for a given application and select the best suited one that optimizes between the counteracting factors of prediction performance and CPU needs.

cs.LG

Predicting high-dimensional heterogeneous time series employing generalized local states

We generalize the concept of local states (LS) for the prediction of high-dimensional, potentially mixed chaotic systems. The construction of generalized local states (GLS) relies on defining distances between time series on the basis of their (non-)linear correlations. We demonstrate the prediction capabilities of our approach based on the reservoir computing (RC) paradigm using the Kuramoto-Sivashinsky (KS), the Lorenz-96 (L96) and a combination of both systems. In the mixed system a separation of the time series belonging to the two different systems is made possible with GLS. More importantly, prediction remains possible with GLS, where the LS approach must naturally fail. Applications for the prediction of very heterogeneous time series with GLSs are briefly outlined.

physics.data-an

Dark matter searches with the IceCube Upgrade

Weakly Interacting Massive Particles (WIMPs) are well-motivated candidates for Dark Matter (DM). WIMP models often include self-annihilation into Standard Model particles such as neutrinos which could potentially be detected by the IceCube Neutrino Observatory. Various searches for a dark matter induced signal have been performed with the existing IceCube detector. However, since there is so far no evidence for WIMPs at TeV scales, more attention is brought to DM candidates at GeV masses, for which the IceCube detector is not sensitive due to its energy threshold. The IceCube collaboration is currently preparing the construction of the IceCube Upgrade which is planned to be deployed in the 2022/2023 South Pole summer season. The IceCube Upgrade will consist of 7 new in-ice strings with about 700 additional optical sensors. This dense sensor array inside the IceCube-DeepCore volume will enhance the reconstruction capability of few-GeV neutrinos. We present first studies on the potential improvements of this upgrade on IceCube's sensitivity to Dark Matter annihilating in the Galactic Center.

astro-ph.HE

Combined Search for Neutrinos from Dark Matter Annihilation in the Galactic Centre using ANTARES and IceCube

The ANTARES and IceCube neutrino telescopes have both searched for neutrinos from dark matter annihilation in the Galactic Centre, putting limits on the thermally-averaged dark matter self-annihilation cross section $\langle \sigma_A \upsilon \rangle$. For WIMP masses above 100 GeV, the most stringent limits were obtained by the ANTARES neutrino telescope, while for lower masses, limits achieved by IceCube are more competitive. The limits obtained by the two detectors are of comparable order of magnitude for WIMP masses going from 50 to 1000 GeV, making this mass range particularly interesting for a combined analysis. In this contribution, we present the limits of the first combined search for dark matter self-annihilation in the centre of the Milky Way using ANTARES and IceCube. The model parameters and the likelihood method were unified, thereby providing a benchmark for future dark matter searches conducted by each collaboration. By combining data of both detectors, we obtained improved limits with respect to the original limits published by the two collaborations.

astro-ph.HE

Measurements of very-forward energy with the CASTOR calorimeter of CMS

The very-forward energy production in hadron collisions is of paramount importance for the understanding of ultra-high energy cosmic ray air showers. The CASTOR calorimeter of CMS is located at $-6.6 < \eta < -5.2$ in the phase-space where the peak of energy is deposited at LHC. The composition and characteristics of the particles in this phase-space have a determining impact on the formation of air shower cascades. An overview of various energy measurements performed with CASTOR is reported and possible implications for cosmic ray physics are outlined.

hep-ex

Core-corona effect in hadron collisions and muon production in air showers

It is very well known that the fraction of energy in a hadron collision going into electromagnetic particles (electrons and photons, including those from decays) has a large impact on the number of muons produced in air shower cascades. Recent measurements at the LHC confirm features that can be linked to a mixture of different underlying particle production mechanisms such as a collective statistical hadronization (core) in addition to the expected string fragmentation (corona). Since the two mechanisms have a different electromagnetic energy fraction, we present a possible connection between statistical hadronization in hadron collisions and muon production in air showers. Using a novel approach, we demonstrate that the core-corona effect as observed at the LHC could be part of the solution for the lack of muon production in simulations of high energy cosmic rays. To probe this hypothesis, we study hadronization in high energy hadron collisions using calorimetric information over a large range of pseudorapidity in combination with the multiplicity of central tracks. As an experimental observable, we propose the production of energy in electromagnetic particles versus hadrons, as a function of pseudorapidity and central charged particle multiplicity.

hep-ph

Arithmetic Distribution Matching

In this work, arithmetic distribution matching (ADM) is presented. ADM invertibly transforms a discrete memoryless source (DMS) into a target DMS. ADM can be used for probabilistic shaping and for rate adaption. Opposed to existing algorithms for distribution matching, ADM works online and can transform arbitrarily long input sequences. It is shown analytically that as the input length tends to infinity, the ADM output perfectly emulates the target DMS with respect to the normalized informational divergence and the entropy rate. Numerical results are presented that confirm the analytical bounds.

cs.IT