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Search engines in polarized media environment: Auditing political information curation on Google and Bing prior to 2024 US elections

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arXiv 2025年

作者： Makhortykh, Mykola Rorhbach, Tobias Sydorova, Maryna Kuznetsova, Elizaveta Institute of Communication and Media Studies University of Bern Fabrikstrasse 8 Bern3012 Switzerland Research group "Platform Algorithms and Digital Propaganda" Weizenbaum Institute Hardenbergstraße 32 Berlin10623 Germany

Search engines play an important role in the context of modern elections. By curating information in response to user queries, search engines influence how individuals are informed about election-related developments and perceive the media environment in which elections take place. It has particular implications for (perceived) polarization, especially if search engines' curation results in a skewed treatment of information sources based on their political leaning. Until now, however, it is unclear whether such a partisan gap emerges through information curation on search engines and what user- and system-side factors affect it. To address this shortcoming, we audit the two largest Western search engines, Google and Bing, prior to the 2024 US presidential elections and examine how these search engines’ organic search results and additional interface elements represent election-related information depending on the queries’ slant, user location, and time when the search was conducted. Our findings indicate that both search engines tend to prioritize left-leaning media sources, with the exact scope of search results’ ideological slant varying between Democrat- and Republican-focused queries. We also observe limited effects of location- and time-based factors on organic search results, whereas results for additional interface elements were more volatile over time and specific US states. Together, our observations highlight that search engines’ information curation actively mirrors the partisan divides present in the US media environments and has the potential to contribute to (perceived) polarization within these environments. © 2025, CC BY.

关键词： Data curation

Undecidable problems associated with variational quantum algorithms

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arXiv 2025年

作者： Korpas, Georgios Kungurtsev, Vyacheslav Mareček, Jakub Department of Computer Science Czech Technical University Prague Czech Republic Quantum Technologies Group HSBC Singapore Archimedes Research Unit on AI Data Science and Algorithms Athena RC Marousi Greece

Variational Quantum algorithms (VQAs), such as the Variational Quantum Eigensolver (VQE) and the Quantum Approximate Optimization Algorithm (QAOA), are widely studied as candidates for near-term quantum advantage. Recent work has shown that training VQAs is NP-hard in general. In this paper, we present a conditional result suggesting that the training of VQAs is undecidable, even in idealized, noiseless settings. We reduce the decision version of the digitized VQA training problem—where circuit parameters are drawn from a discrete set—to the question of whether a universal Diophantine equation (UDE) has a root. This reduction relies on encoding the UDE into the structure of a variational quantum circuit via the matrix exponentials. The central step involves establishing a correspondence between the objective function of the VQA and a known UDE of 58 variables and degree 4. Our main result is conditional on a natural conjecture: that a certain system of structured complex polynomial equations—arising from the inner product of a VQA circuit output and a fixed observable—has at least one solution. We argue this conjecture is plausible based on dimension-counting arguments (degrees of freedom in the Hamiltonians, state vector, and observable), and the generic solvability of such systems in algebraic geometry over the complex numbers. Under this assumption, we suggest that deciding whether a digitized VQA achieves a given energy threshold is undecidable. This links the limitations of variational quantum algorithms to foundational questions in mathematics and logic, extending the known landscape of quantum computational hardness to include uncomputability. Additionally, we establish an unconditional undecidability result for VQA convergence in open quantum systems. © 2025, CC BY.

关键词： Hamiltonians

ExMAG: Learning of Maximally Ancestral Graphs

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arXiv 2025年

作者： Ryšavý, Petr Rytíř, Pavel He, Xiaoyu Korpas, Georgios Mareček, Jakub Department of Computer Science Czech Technical University Prague Czech Republic HSBC Quantum Technologies Group Innovation & Ventures HSBC Singapore Archimedes Research Unit on AI Data Science and Algorithms Marousi Greece

As one transitions from statistical to causal learning, one is seeking the most appropriate causal model. Dynamic Bayesian networks are a popular model, where a weighted directed acyclic graph represents the causal relationships. Stochastic processes are represented by its vertices, and weighted oriented edges suggest the strength of the causal relationships. When there are confounders, one would like to utilize both oriented edges (when the direction of causality is clear) and edges that are not oriented (when there is a confounder or not a relationship), yielding mixed graphs. A little-studied extension of acyclicity to this mixed-graph setting is known as maximally ancestral graphs with consideration of confounders. We propose a score-based learning algorithm for learning maximally ancestral graphs. A mixed-integer quadratic program is formulated, and an algorithmic approach is proposed, in which the pre-generation of exponentially many constraints is avoided by generating only violated constraints in the so-called branch-and-cut ("lazy constraint") method. Comparing the novel approach to the state-of-the-art, we show that the proposed approach turns out to produce more accurate results when applied to small and medium-sized synthetic instances containing up to 25 variables. Copyright © 2025, The Authors. All rights reserved.

关键词： Bayesian networks

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Federated Sinkhorn

arXiv 2025年

作者： Kulcsar, Jeremy Kungurtsev, Vyacheslav Korpas, Georgios Giaconi, Giulio Shoosmith, William Department of Computer Science Czech Technical University Prague Czech Republic HSBC Quantum Technologies Group HSBC Hong Kong HSBC Quantum Technologies Group HSBC Singapore HSBC Quantum Technologies Group HSBC United Kingdom Archimedes Research Unit on AI Data Science and Algorithms Marousi Greece

In this work we, investigate the potential of solving the discrete Optimal Transport (OT) problem with entropy regularization in a federated learning setting. Recall that the celebrated Sinkhorn algorithm transforms the classical OT linear program into strongly convex constrained optimization, facilitating first order methods for otherwise intractably large problems. A common contemporary setting that remains an open problem as far as the application of Sinkhorn is the presence of data spread across clients with distributed inter-communication, either due to clients whose privacy is a concern, or simply by necessity of processing and memory hardware limitations. In this work we investigate various natural procedures, which we refer to as Federated Sinkhorn, that handle distributed environments where data is partitioned across multiple clients. We formulate the problem as minimizing the transport cost with an entropy regularization term, subject to marginal constraints, where block components of the source and target distribution vectors are locally known to clients corresponding to each block. We consider both synchronous and asynchronous variants as well as all-to-all and server-client communication topology protocols. Each procedure allows clients to compute local operations on their data partition while periodically exchanging information with others. We provide theoretical guarantees on convergence for the different variants under different possible conditions. We empirically demonstrate the algorithms’ performance on synthetic datasets and a real-world financial risk assessment application. The investigation highlights the subtle tradeoffs associated with computation and communication time in different settings and how they depend on problem size and sparsity. © 2025, CC BY.

关键词： Constrained optimization

Identifiability of Autonomous and Controlled Open Quantum Systems

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arXiv 2025年

作者： Parvaiz, Waqas Aspman, Johannes Wodecki, Ales Korpas, Georgios Marecek, Jakub Department of Computer Science Czech Technical University Prague Czech Republic Quantum Technologies Group HSBC Lab Emerging Technologies Innovation & Ventures Singapore Archimedes Research Unit on AI Data Science and Algorithms Athena Research and Innovation Center Marousi Greece

Open quantum systems are a rich area of research in the intersection of quantum mechanics and stochastic analysis. By considering a variety of master equations, we unify multiple views of autonomous and controlled open quantum systems and, through considering their measurement dynamics, connect them to classical linear and bilinear system identification theory. This allows us to formulate corresponding notions of quantum state identifiability for these systems which, in particular, applies to quantum state tomography, providing conditions under which the probed quantum system is reconstructible. Interestingly, the dynamical representation of the system lends itself to considering two types of identifiability: the full master equation recovery and the recovery of the corresponding system matrices of the linear and bilinear systems. Both of these concepts are discussed in detail, and conditions under which reconstruction is possible are given. We set the groundwork for a number of constructive approaches to the identification of open quantum systems. Copyright © 2025, The Authors. All rights reserved.

关键词： Stochastic systems

HelioCubed: A High Order Inner Heliosphere Simulation Code with a Mapped Cubed Sphere Grid and Adaptive Mesh Refinement 16

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HelioCubed: A High Order Inner Heliosphere Simulation Code w...

16th International Conference on Numerical Modeling of Space Plasma Flows, ASTRONUM 2024

作者： Singh, Talwinder Colella, Phillip Van-Straalen, Brian Bozhart, Chris Pogorelov, Nikolai V. Department of Physics & Astronomy Georgia State University AtlantaGA30303 United States Applied Numerical Algorithms Group Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Electrical Engineering and Computer Science Department University of California Berkeley BerkeleyCA94720 United States Department of Space Science The University of Alabama in Huntsville HuntsvilleAL35805 United States Center for Space Plasma and Aeronomic Research The University of Alabama in Huntsville HuntsvilleAL35805 United States

We present the HelioCubed, a high-order magnetohydrodynamic (MHD) code designed for modeling the inner heliosphere. The code is designed to achieve 4th order accuracy both in space and in time. In addition, HelioCubed can perform simulations on mapped grids, such as those based on cubed spheres, which makes it possible to overcome stability limitations caused by the geometrical singularity at the polar axis of a spherical grid, thus enabling substantially larger time steps. HelioCubed has been developed using the high-level Proto library, ensures performance portability across CPU and GPU architectures, and supports back-end implementations, e.g., CUDA, HIP, OpenMP, and MPI. The code is compatible with the HDF5 library, which facilitates seamless data handling for simulations and boundary conditions derived from semi-empirical and MHD models of the solar corona. While presenting the results of preliminary simulations, we demonstrate that our simulations are indeed performed with 4th order of accuracy. Our approach ensures that HelioCubed solves the MHD equations preserving the radial flow to machine round-off error even on cubed-sphere grids. Solar wind simulations are performed using the boundary conditions provided by the Wang-Sheeley-Arge coronal model of the ambient solar wind. It also allows us to to simulate coronal mass ejections using observation-driven flux rope models. These capabilities make HelioCubed a versatile and powerful tool to advance heliophysics research and space weather forecasting. © 2025 Institute of Physics Publishing. All rights reserved.

关键词： Mesh generation

Development of a Hypersonic Entry Test Platform

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Development of a Hypersonic Entry Test Platform

AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2025

作者： Johnson, Breanna J. Johnson, Kate E. Jang, Peter Steffes, Stephen R. Fritz, Matthew P. Hawke, Veronica Garcia, Joseph A. Morr, Donald E. NASA Johnson Space Center Flight Mechanics and Trajectory Design Branch HoustonTX77058 United States NASA Johnson Space Center Applied Aeroscience and CFD Branch HoustonTX77058 United States Aerodyne Industries Applied Aeroscience and CFD Branch HoustonTX77058 United States Charles Stark Draper Laboratory Navigation Algorithms and Software Space GNC Group HoustonTX77058 United States Science Technology Corporation Systems Analysis Office Mountain ViewCA United States NASA Ames Research Center NASA Systems Analysis Office Mountain ViewCA94035 United States Millennium Engineering and Integration Company ArlingtonVA22202 United States

ISBN: (数字)9781624107238

ISBN: (纸本)9781624107238

NASA is designing and building a low-cost, scalable, rapidly developed test platform to lower the barrier to entry for entry, descent, and landing (EDL) technologies. This HyperSonic Testing for Entry Platform, HyperSTEP, will enable the low-cost flight demonstration of hypersonic entry technologies, leveraging a publishable government reference design to further enable future government and industry landers. The HyperSTEP vehicle leverages a lifting body shape that was originally designed for a NASA human-class Mars mission concept vehicle, the CobraMRV. Lifting body vehicles offer increased volume efficiency and greater range control capabilities over capsules, making them an attractive class of vehicles to further develop for small to large payload return missions from the Moon, Mars, and beyond. Progress has been made in the development of the HyperSTEP vehicle in the areas of aerodynamics, aerothermodynamics, structural design and packaging, propulsion, guidance navigation and control (GN&C), decelerators (i.e., parachutes), and the thermal protection system (TPS). This paper details progress made in refining the mission concept of operations (ConOps) for the first notional missions and the development of the aerodynamic and aerothermodynamic databases, GN&C, and parachute system, as the project moves into its build and test phase. © 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： NASA

A fast solver for modeling the evolution of virus populations

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A fast solver for modeling the evolution of virus population...

2011 International Conference for High Performance Computing, Networking, Storage and Analysis, SC11

作者： Niederbrucker, Gerhard Gansterer, Wilfried N. Research Group Theory and Applications of Algorithms University of Vienna Austria

ISBN: (纸本)9781450307710

Solving Eigen's quasispecies model for the evolution of virus populations involves the computation of the dominant eigenvector of a matrix whose size N grows exponentially with the chain length of the virus to be modeled. Most biologically interesting chain lengths are so far well beyond the reach of existing algorithms and hardware. We show how to exploit the special properties of the problem under consideration and design a fast and accurate solver which reduces the complexity to Θ(N log2 N). Our solver is even faster than existing approximative strategies and contrary to those it can also be applied to more general formulations of the quasispecies model. Substantial further improvements and high parallelism can be achieved for special fitness landscapes in the evolution model. Beyond theoretical analysis, we evaluate the performance of our new solver experimentally on a GPU with an OpenCL implementation and illustrate that it achieves speedup factors of more than 107 over standard approaches. Copyright 2011 ACM.

关键词： Graphics processing unit

Extending characterizations of truthful mechanisms from subdomains to domains

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Extending characterizations of truthful mechanisms from subd...

7th International Workshop on Internet and Network Economics, WINE 2011

作者： Vidali, Angelina Theory and Applications of Algorithms Research Group University of Vienna Austria

ISBN: (纸本)9783642255090

The already extended literature in Combinatorial Auctions, Public Projects and Scheduling demands a more systematic classification of the domains and a clear comparison of the results known. Connecting characterization results for different settings and providing a characterization proof using another characterization result as a black box without having to repeat a tediously similar proof is not only elegant and desirable, but also greatly enhances our intuition and provides a classification of different results and a unified and deeper understanding. We consider whether one can extend a characterization of a subdomain to a domain in a black-box manner. We show that this is possible for n-player stable mechanisms if the only truthful mechanisms for the subdomain are the affine maximizers. We further show that if the characterization of the subdomain involves a combination of affine maximizers and threshold mechanisms, the threshold mechanisms for the subdomain cannot be extended to truthful mechanisms for the union of the subdomain with a (very slight) affine transformation of it. We also show that for every truthful mechanism in a domain there exists a corresponding truthful mechanism for any affine transformation of the domain. We finally plug in as a black box to our theorems the characterization of additive 2-player combinatorial auctions that are decisive and allocate all items (which essentially is the domain for scheduling unrelated machines) and show that the 2-player truthful mechanisms of any domain, which is strictly a superdomain of it are only the affine maximizers. This gives a unique characterization proof of the decisive 2-player mechanisms for: Combinatorial Public Projects, Unrestricted domains, as well as for Submodular and Subadditive Combinatorial Auctions that allocate all items. © 2011 Springer-Verlag Berlin Heidelberg.

关键词： Scheduling