@article{11612,
  abstract     = {Since the onset of the "space revolution" of high-precision high-cadence photometry, asteroseismology has been demonstrated as a powerful tool for informing Galactic archeology investigations. The launch of the NASA Transiting Exoplanet Survey Satellite (TESS) mission has enabled seismic-based inferences to go full sky—providing a clear advantage for large ensemble studies of the different Milky Way components. Here we demonstrate its potential for investigating the Galaxy by carrying out the first asteroseismic ensemble study of red giant stars observed by TESS. We use a sample of 25 stars for which we measure their global asteroseimic observables and estimate their fundamental stellar properties, such as radius, mass, and age. Significant improvements are seen in the uncertainties of our estimates when combining seismic observables from TESS with astrometric measurements from the Gaia mission compared to when the seismology and astrometry are applied separately. Specifically, when combined we show that stellar radii can be determined to a precision of a few percent, masses to 5%–10%, and ages to the 20% level. This is comparable to the precision typically obtained using end-of-mission Kepler data.},
  author       = {Aguirre, Víctor Silva and Stello, Dennis and Stokholm, Amalie and Mosumgaard, Jakob R. and Ball, Warrick H. and Basu, Sarbani and Bossini, Diego and Bugnet, Lisa Annabelle and Buzasi, Derek and Campante, Tiago L. and Carboneau, Lindsey and Chaplin, William J. and Corsaro, Enrico and Davies, Guy R. and Elsworth, Yvonne and García, Rafael A. and Gaulme, Patrick and Hall, Oliver J. and Handberg, Rasmus and Hon, Marc and Kallinger, Thomas and Kang, Liu and Lund, Mikkel N. and Mathur, Savita and Mints, Alexey and Mosser, Benoit and Çelik Orhan, Zeynep and Rodrigues, Thaíse S. and Vrard, Mathieu and Yıldız, Mutlu and Zinn, Joel C. and Örtel, Sibel and Beck, Paul G. and Bell, Keaton J. and Guo, Zhao and Jiang, Chen and Kuszlewicz, James S. and Kuehn, Charles A. and Li, Tanda and Lundkvist, Mia S. and Pinsonneault, Marc and Tayar, Jamie and Cunha, Margarida S. and Hekker, Saskia and Huber, Daniel and Miglio, Andrea and F. G. Monteiro, Mario J. P. and Slumstrup, Ditte and Winther, Mark L. and Angelou, George and Benomar, Othman and Bódi, Attila and De Moura, Bruno L. and Deheuvels, Sébastien and Derekas, Aliz and Di Mauro, Maria Pia and Dupret, Marc-Antoine and Jiménez, Antonio and Lebreton, Yveline and Matthews, Jaymie and Nardetto, Nicolas and do Nascimento, Jose D. and Pereira, Filipe and Rodríguez Díaz, Luisa F. and Serenelli, Aldo M. and Spitoni, Emanuele and Stonkutė, Edita and Suárez, Juan Carlos and Szabó, Robert and Van Eylen, Vincent and Ventura, Rita and Verma, Kuldeep and Weiss, Achim and Wu, Tao and Barclay, Thomas and Christensen-Dalsgaard, Jørgen and Jenkins, Jon M. and Kjeldsen, Hans and Ricker, George R. and Seager, Sara and Vanderspek, Roland},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal Letters},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{Detection and characterization of oscillating red giants: First results from the TESS satellite}},
  doi          = {10.3847/2041-8213/ab6443},
  volume       = {889},
  year         = {2020},
}

@inbook{11622,
  abstract     = {The recent discovery of low-amplitude dipolar oscillation mixed modes in massive red giants indicates the presence of a missing physical process inside their cores. Stars more massive than ∼ 1.3 M⊙ are known to develop a convective core during the main-sequence: the dynamo process triggered by this convection could be the origin of a strong magnetic field inside the core of the star, trapped when it becomes stably stratified and for the rest of its evolution. The presence of highly magnetized white dwarfs strengthens the hypothesis of buried fossil magnetic fields inside the core of evolved low-mass stars. If such a fossil field exists, it should affect the mixed modes of red giants as they are sensitive to processes affecting the deepest layers of these stars. The impact of a magnetic field on dipolar oscillations modes was one of Pr. Michael J. Thompson’s research topics during the 90s when preparing the helioseismic SoHO space mission. As the detection of gravity modes in the Sun is still controversial, the investigation of the solar oscillation modes did not provide any hint of the existence of a magnetic field in the solar radiative core. Today we have access to the core of evolved stars thanks to the asteroseismic observation of mixed modes from CoRoT, Kepler, K2 and TESS missions. The idea of applying and generalizing the work done for the Sun came from discussions with Pr. Michael Thompson in early 2018 before we lost him. Following the path we drew together, we theoretically investigate the effect of a stable axisymmetric mixed poloidal and toroidal magnetic field, aligned with the rotation axis of the star, on the mixed modes frequencies of a typical evolved low-mass star. This enables us to estimate the magnetic perturbations to the eigenfrequencies of mixed dipolar modes, depending on the magnetic field strength and the evolutionary state of the star. We conclude that strong magnetic fields of ∼ 1MG should perturb the mixed-mode frequency pattern enough for its effects to be detectable inside current asteroseismic data.},
  author       = {Bugnet, Lisa Annabelle and Prat, V. and Mathis, S. and García, R. A. and Mathur, S. and Augustson, K. and Neiner, C. and Thompson, M. J.},
  booktitle    = {Dynamics of the Sun and Stars},
  editor       = {Monteiro, Mario and Garcia, Rafael A and Christensen-Dalsgaard, Jorgen and McIntosh, Scott W},
  isbn         = {978-3-030-55335-7},
  issn         = {1570-6605},
  pages        = {251--257},
  publisher    = {Springer Nature},
  title        = {{The impact of a fossil magnetic field on dipolar mixed-mode frequencies in sub- and red-giant stars}},
  doi          = {10.1007/978-3-030-55336-4_33},
  volume       = {57},
  year         = {2020},
}

@article{11674,
  abstract     = {In this paper, we study the problem of opening centers to cluster a set of clients in a metric space so as to minimize the sum of the costs of the centers and of the cluster radii, in a dynamic environment where clients arrive and depart, and the solution must be updated efficiently while remaining competitive with respect to the current optimal solution. We call this dynamic sum-of-radii clustering problem. We present a data structure that maintains a solution whose cost is within a constant factor of the cost of an optimal solution in metric spaces with bounded doubling dimension and whose worst-case update time is logarithmic in the parameters of the problem.},
  author       = {Henzinger, Monika H and Leniowski, Dariusz and Mathieu, Claire},
  issn         = {1432-0541},
  journal      = {Algorithmica},
  number       = {11},
  pages        = {3183--3194},
  publisher    = {Springer Nature},
  title        = {{Dynamic clustering to minimize the sum of radii}},
  doi          = {10.1007/s00453-020-00721-7},
  volume       = {82},
  year         = {2020},
}

@article{11675,
  abstract     = {We consider the problems of maintaining an approximate maximum matching and an approximate minimum vertex cover in a dynamic graph undergoing a sequence of edge insertions/deletions. Starting with the seminal work of Onak and Rubinfeld (in: Proceedings of the ACM symposium on theory of computing (STOC), 2010), this problem has received significant attention in recent years. Very recently, extending the framework of Baswana et al. (in: Proceedings of the IEEE symposium on foundations of computer science (FOCS), 2011) , Solomon (in: Proceedings of the IEEE symposium on foundations of computer science (FOCS), 2016) gave a randomized dynamic algorithm for this problem that has an approximation ratio of 2 and an amortized update time of O(1) with high probability. This algorithm requires the assumption of an oblivious adversary, meaning that the future sequence of edge insertions/deletions in the graph cannot depend in any way on the algorithm’s past output. A natural way to remove the assumption on oblivious adversary is to give a deterministic dynamic algorithm for the same problem in O(1) update time. In this paper, we resolve this question. We present a new deterministic fully dynamic algorithm that maintains a O(1)-approximate minimum vertex cover and maximum fractional matching, with an amortized update time of O(1). Previously, the best deterministic algorithm for this problem was due to Bhattacharya et al. (in: Proceedings of the ACM-SIAM symposium on discrete algorithms (SODA), 2015); it had an approximation ratio of (2+ε) and an amortized update time of O(logn/ε2). Our result can be generalized to give a fully dynamic O(f3)-approximate algorithm with O(f2) amortized update time for the hypergraph vertex cover and fractional hypergraph matching problem, where every hyperedge has at most f vertices.},
  author       = {Bhattacharya, Sayan and Chakrabarty, Deeparnab and Henzinger, Monika H},
  issn         = {1432-0541},
  journal      = {Algorithmica},
  keywords     = {Dynamic algorithms, Data structures, Graph algorithms, Matching, Vertex cover},
  number       = {4},
  pages        = {1057--1080},
  publisher    = {Springer Nature},
  title        = {{Deterministic dynamic matching in O(1) update time}},
  doi          = {10.1007/s00453-019-00630-4},
  volume       = {82},
  year         = {2020},
}

@inproceedings{11816,
  abstract     = {In recent years, significant advances have been made in the design and analysis of fully dynamic maximal matching algorithms. However, these theoretical results have received very little attention from the practical perspective. Few of the algorithms are implemented and tested on real datasets, and their practical potential is far from understood. In this paper, we attempt to bridge the gap between theory and practice that is currently observed for the fully dynamic maximal matching problem. We engineer several algorithms and empirically study those algorithms on an extensive set of dynamic instances.},
  author       = {Henzinger, Monika H and Shahbaz, Khan and Paul, Richard and Schulz, Christian},
  booktitle    = {8th Annual European Symposium on Algorithms},
  isbn         = {9783959771627},
  issn         = {1868-8969},
  location     = {Pisa, Italy},
  publisher    = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
  title        = {{Dynamic matching algorithms in practice}},
  doi          = {10.4230/LIPIcs.ESA.2020.58},
  volume       = {173},
  year         = {2020},
}

@inproceedings{11818,
  abstract     = {With input sizes becoming massive, coresets - small yet representative summary of the input - are relevant more than ever. A weighted set C_w that is a subset of the input is an ε-coreset if the cost of any feasible solution S with respect to C_w is within [1±ε] of the cost of S with respect to the original input. We give a very general technique to compute coresets in the fully-dynamic setting where input points can be added or deleted. Given a static (i.e., not dynamic) ε-coreset-construction algorithm that runs in time t(n, ε, λ) and computes a coreset of size s(n, ε, λ), where n is the number of input points and 1-λ is the success probability, we give a fully-dynamic algorithm that computes an ε-coreset with worst-case update time O((log n) ⋅ t(s(n, ε/log n, λ/n), ε/log n, λ/n)) (this bound is stated informally), where the success probability is 1-λ. Our technique is a fully-dynamic analog of the merge-and-reduce technique, which is due to Har-Peled and Mazumdar [Har-Peled and Mazumdar, 2004] and is based on a technique of Bentley and Saxe [Jon Louis Bentley and James B. Saxe, 1980], that applies to the insertion-only setting where points can only be added. Although, our space usage is O(n), our technique works in the presence of an adaptive adversary, and we show that Ω(n) space is required when adversary is adaptive.
As a concrete implication of our technique, using the result of Braverman et al. [{Braverman} et al., 2016], we get fully-dynamic ε-coreset-construction algorithms for k-median and k-means with worst-case update time O(ε^{-2} k² log⁵ n log³ k) and coreset size O(ε^{-2} k log n log² k) ignoring log log n and log(1/ε) factors and assuming that ε = Ω(1/poly(n)) and λ = Ω(1/poly(n)) (which are very weak assumptions made only to make these bounds easy to parse). This results in the first fully-dynamic constant-approximation algorithms for k-median and k-means with update times O(poly(k, log n, ε^{-1})). Specifically, the dependence on k is only quadratic, and the bounds are worst-case. The best previous bound for both problems was amortized O(nlog n) by Cohen-Addad et al. [Cohen-Addad et al., 2019] via randomized O(1)-coresets in O(n) space.
We also show that under the OMv conjecture [Monika Henzinger et al., 2015], a fully-dynamic (4 - δ)-approximation algorithm for k-means must either have an amortized update time of Ω(k^{1-γ}) or amortized query time of Ω(k^{2 - γ}), where γ > 0 is a constant.},
  author       = {Henzinger, Monika H and Kale, Sagar},
  booktitle    = {28th Annual European Symposium on Algorithms},
  isbn         = {9783959771627},
  issn         = {1868-8969},
  location     = {Pisa, Italy},
  publisher    = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
  title        = {{Fully-dynamic coresets}},
  doi          = {10.4230/LIPIcs.ESA.2020.57},
  volume       = {173},
  year         = {2020},
}

@inproceedings{11819,
  abstract     = {We present a practically efficient algorithm that finds all global minimum cuts in huge undirected graphs. Our algorithm uses a multitude of kernelization rules to reduce the graph to a small equivalent instance and then finds all minimum cuts using an optimized version of the algorithm of Nagamochi, Nakao and Ibaraki. In shared memory we are able to find all minimum cuts of graphs with up to billions of edges and millions of minimum cuts in a few minutes. We also give a new linear time algorithm to find the most balanced minimum cuts given as input the representation of all minimum cuts.},
  author       = {Henzinger, Monika H and Noe, Alexander and Schulz, Christian and Strash, Darren},
  booktitle    = {28th Annual European Symposium on Algorithms},
  isbn         = {9783959771627},
  issn         = {1868-8969},
  location     = {Pisa, Italy},
  publisher    = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
  title        = {{Finding all global minimum cuts in practice}},
  doi          = {10.4230/LIPIcs.ESA.2020.59},
  volume       = {173},
  year         = {2020},
}

@inproceedings{11822,
  abstract     = {The fully dynamic transitive closure problem asks to maintain reachability information in a directed graph between arbitrary pairs of vertices, while the graph undergoes a sequence of edge insertions and deletions. The problem has been thoroughly investigated in theory and many specialized algorithms for solving it have been proposed in the last decades. In two large studies [Frigioni ea, 2001; Krommidas and Zaroliagis, 2008], a number of these algorithms have been evaluated experimentally against simple, static algorithms for graph traversal, showing the competitiveness and even superiority of the simple algorithms in practice, except for very dense random graphs or very high ratios of queries. A major drawback of those studies is that only small and mostly randomly generated graphs are considered.
In this paper, we engineer new algorithms to maintain all-pairs reachability information which are simple and space-efficient. Moreover, we perform an extensive experimental evaluation on both generated and real-world instances that are several orders of magnitude larger than those in the previous studies. Our results indicate that our new algorithms outperform all state-of-the-art algorithms on all types of input considerably in practice.},
  author       = {Hanauer, Kathrin and Henzinger, Monika H and Schulz, Christian},
  booktitle    = {18th International Symposium on Experimental Algorithms},
  isbn         = {9783959771481},
  issn         = {1868-8969},
  location     = {Pisa, Italy},
  publisher    = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
  title        = {{Faster fully dynamic transitive closure in practice}},
  doi          = {10.4230/LIPIcs.SEA.2020.14},
  volume       = {160},
  year         = {2020},
}

@inproceedings{11824,
  abstract     = {Independent set is a fundamental problem in combinatorial optimization. While in general graphs the problem is essentially inapproximable, for many important graph classes there are approximation algorithms known in the offline setting. These graph classes include interval graphs and geometric intersection graphs, where vertices correspond to intervals/geometric objects and an edge indicates that the two corresponding objects intersect.
We present dynamic approximation algorithms for independent set of intervals, hypercubes and hyperrectangles in d dimensions. They work in the fully dynamic model where each update inserts or deletes a geometric object. All our algorithms are deterministic and have worst-case update times that are polylogarithmic for constant d and ε>0, assuming that the coordinates of all input objects are in [0, N]^d and each of their edges has length at least 1. We obtain the following results:
- For weighted intervals, we maintain a (1+ε)-approximate solution.
- For d-dimensional hypercubes we maintain a (1+ε)2^d-approximate solution in the unweighted case and a O(2^d)-approximate solution in the weighted case. Also, we show that for maintaining an unweighted (1+ε)-approximate solution one needs polynomial update time for d ≥ 2 if the ETH holds.
- For weighted d-dimensional hyperrectangles we present a dynamic algorithm with approximation ratio (1+ε)log^{d-1}N.},
  author       = {Henzinger, Monika H and Neumann, Stefan and Wiese, Andreas},
  booktitle    = {36th International Symposium on Computational Geometry},
  isbn         = {9783959771436},
  issn         = {1868-8969},
  location     = {Zurich, Switzerland},
  publisher    = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
  title        = {{Dynamic approximate maximum independent set of intervals, hypercubes and hyperrectangles}},
  doi          = {10.4230/LIPIcs.SoCG.2020.51},
  volume       = {164},
  year         = {2020},
}

@inproceedings{11825,
  abstract     = {We give a fully dynamic (Las-Vegas style) algorithm with constant expected amortized time per update that maintains a proper (Δ+1)-vertex coloring of a graph with maximum degree at most Δ. This improves upon the previous O(log Δ)-time algorithm by Bhattacharya et al. (SODA 2018). Our algorithm uses an approach based on assigning random ranks to vertices and does not need to maintain a hierarchical graph decomposition. We show that our result does not only have optimal running time, but is also optimal in the sense that already deciding whether a Δ-coloring exists in a dynamically changing graph with maximum degree at most Δ takes Ω(log n) time per operation.},
  author       = {Henzinger, Monika H and Peng, Pan},
  booktitle    = {37th International Symposium on Theoretical Aspects of Computer Science},
  isbn         = {9783959771405},
  issn         = {1868-8969},
  location     = {Montpellier, France},
  publisher    = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
  title        = {{Constant-time dynamic (Δ+1)-coloring}},
  doi          = {10.4230/LIPIcs.STACS.2020.53},
  volume       = {154},
  year         = {2020},
}

@inproceedings{11852,
  abstract     = {We present a general framework of designing efficient dynamic approximate algorithms for optimization problems on undirected graphs. In particular, we develop a technique that, given any problem that admits a certain notion of vertex sparsifiers, gives data structures that maintain approximate solutions in sub-linear update and query time. We illustrate the applicability of our paradigm to the following problems. (1)A fully-dynamic algorithm that approximates all-pair maximum-flows/minimum-cuts up to a nearly logarithmic factor in O~(n2/3) 11The O~(⋅) notation is used in this paper to hide poly-logarithmic factors. amortized time against an oblivious adversary, and O~(m3/4) time against an adaptive adversary. (2)An incremental data structure that maintains O(1) - approximate shortest path in no(1) time per operation, as well as fully dynamic approximate all-pair shortest path and transshipment in O~(n2/3+o(1)) amortized time per operation. (3)A fully-dynamic algorithm that approximates all-pair effective resistance up to an (1+ϵ) factor in O~(n2/3+o(1)ϵ−O(1)) amortized update time per operation. The key tool behind result (1) is the dynamic maintenance of an algorithmic construction due to Madry [FOCS' 10], which partitions a graph into a collection of simpler graph structures (known as j-trees) and approximately captures the cut-flow and metric structure of the graph. The O(1)-approximation guarantee of (2) is by adapting the distance oracles by [Thorup-Zwick JACM '05]. Result (3) is obtained by invoking the random-walk based spectral vertex sparsifier by [Durfee et al. STOC '19] in a hierarchical manner, while carefully keeping track of the recourse among levels in the hierarchy. See https://arxiv.org/pdf/2005.02368.pdf for the full version of this paper.},
  author       = {Chen, Li and Goranci, Gramoz and Henzinger, Monika H and Peng, Richard and Saranurak, Thatchaphol},
  booktitle    = {61st Annual Symposium on Foundations of Computer Science},
  isbn         = {978-1-7281-9622-0},
  issn         = {2575-8454},
  location     = {Durham, NC, United States},
  pages        = {1135--1146},
  publisher    = {Institute of Electrical and Electronics Engineers},
  title        = {{Fast dynamic cuts, distances and effective resistances via vertex sparsifiers}},
  doi          = {10.1109/focs46700.2020.00109},
  year         = {2020},
}

@inproceedings{11880,
  abstract     = {Given a directed graph and a source vertex, the fully dynamic single-source reachability problem is to maintain the set of vertices that are reachable from the given vertex, subject to edge deletions and insertions. It is one of the most fundamental problems on graphs and appears directly or indirectly in many and varied applications. While there has been theoretical work on this problem, showing both linear conditional lower bounds for the fully dynamic problem and insertions-only and deletions-only upper bounds beating these conditional lower bounds, there has been no experimental study that compares the performance of fully dynamic reachability algorithms in practice. Previous experimental studies in this area concentrated only on the more general all-pairs reachability or transitive closure problem and did not use real-world dynamic graphs.

In this paper, we bridge this gap by empirically studying an extensive set of algorithms for the single-source reachability problem in the fully dynamic setting. In particular, we design several fully dynamic variants of well-known approaches to obtain and maintain reachability information with respect to a distinguished source. Moreover, we extend the existing insertions-only or deletions-only upper bounds into fully dynamic algorithms. Even though the worst-case time per operation of all the fully dynamic algorithms we evaluate is at least linear in the number of edges in the graph (as is to be expected given the conditional lower bounds) we show in our extensive experimental evaluation that their performance differs greatly, both on generated as well as on real-world instances.},
  author       = {Hanauer, Kathrin and Henzinger, Monika H and Schulz, Christian},
  booktitle    = {2020 Symposium on Algorithm Engineering and Experiments},
  location     = {Salt Lake City, UT, United States},
  pages        = {106--119},
  publisher    = {Society for Industrial and Applied Mathematics},
  title        = {{Fully dynamic single-source reachability in practice: An experimental study}},
  doi          = {10.1137/1.9781611976007.9},
  year         = {2020},
}

@inproceedings{11881,
  abstract     = {We introduce the fastest known exact algorithm for the multiterminal cut problem with k terminals. In particular, we engineer existing as well as new data reduction rules. We use the rules within a branch-and-reduce framework and to boost the performance of an ILP formulation. Our algorithms achieve improvements in running time of up to multiple orders of magnitudes over the ILP formulation without data reductions, which has been the de facto standard used by practitioners. This allows us to solve instances to optimality that are significantly larger than was previously possible.},
  author       = {Henzinger, Monika H and Noe, Alexander and Schulz, Christian},
  booktitle    = {2020 Symposium on Algorithm Engineering and Experiments},
  location     = {Salt Lake City, UT, United States},
  pages        = {42--55},
  publisher    = {Society for Industrial and Applied Mathematics},
  title        = {{Shared-memory branch-and-reduce for multiterminal cuts}},
  doi          = {10.1137/1.9781611976007.4},
  year         = {2020},
}

@article{11889,
  abstract     = {We study the problem of computing a minimum cut in a simple, undirected graph and give a deterministic 𝑂(𝑚log2𝑛loglog2𝑛) time algorithm. This improves on both the best previously known deterministic running time of 𝑂(𝑚log12𝑛) (Kawarabayashi and Thorup [J. ACM, 66 (2018), 4]) and the best previously known randomized running time of 𝑂(𝑚log3𝑛) (Karger [J. ACM, 47 (2000), pp. 46--76]) for this problem, though Karger's algorithm can be further applied to weighted graphs. Moreover, our result extends to balanced directed graphs, where the balance of a directed graph captures how close the graph is to being Eulerian. Our approach is using the Kawarabayashi and Thorup graph compression technique, which repeatedly finds low conductance cuts. To find these cuts they use a diffusion-based local algorithm. We use instead a flow-based local algorithm and suitably adjust their framework to work with our flow-based subroutine. Both flow- and diffusion-based methods have a long history of being applied to finding low conductance cuts. Diffusion algorithms have several variants that are naturally local, while it is more complicated to make flow methods local. Some prior work has proven nice properties for local flow-based algorithms with respect to improving or cleaning up low conductance cuts. Our flow subroutine, however, is the first that both is local and produces low conductance cuts. Thus, it may be of independent interest.},
  author       = {Henzinger, Monika H and Rao, Satish and Wang, Di},
  issn         = {1095-7111},
  journal      = {SIAM Journal on Computing},
  number       = {1},
  pages        = {1--36},
  publisher    = {Society for Industrial & Applied Mathematics},
  title        = {{Local flow partitioning for faster edge connectivity}},
  doi          = {10.1137/18m1180335},
  volume       = {49},
  year         = {2020},
}

@article{11894,
  abstract     = {Graph sparsification aims at compressing large graphs into smaller ones while preserving important characteristics of the input graph. In this work we study vertex sparsifiers, i.e., sparsifiers whose goal is to reduce the number of vertices. We focus on the following notions: (1) Given a digraph 𝐺=(𝑉,𝐸) and terminal vertices 𝐾⊂𝑉 with |𝐾|=𝑘, a (vertex) reachability sparsifier of 𝐺 is a digraph 𝐻=(𝑉𝐻,𝐸𝐻), 𝐾⊂𝑉𝐻 that preserves all reachability information among terminal pairs. Let |𝑉𝐻| denote the size of 𝐻. In this work we introduce the notion of reachability-preserving minors (RPMs), i.e., we require 𝐻 to be a minor of 𝐺. We show any directed graph 𝐺 admits an RPM 𝐻 of size 𝑂(𝑘3), and if 𝐺 is planar, then the size of 𝐻 improves to 𝑂(𝑘2log𝑘). We complement our upper bound by showing that there exists an infinite family of grids such that any RPM must have Ω(𝑘2) vertices. (2) Given a weighted undirected graph 𝐺=(𝑉,𝐸) and terminal vertices 𝐾 with |𝐾|=𝑘, an exact (vertex) cut sparsifier of 𝐺 is a graph 𝐻 with 𝐾⊂𝑉𝐻 that preserves the value of minimum cuts separating any bipartition of 𝐾. We show that planar graphs with all the 𝑘 terminals lying on the same face admit exact cut sparsifiers of size 𝑂(𝑘2) that are also planar. Our result extends to flow and distance sparsifiers. It improves the previous best-known bound of 𝑂(𝑘222𝑘) for cut and flow sparsifiers by an exponential factor and matches an Ω(𝑘2) lower-bound for this class of graphs.},
  author       = {Goranci, Gramoz and Henzinger, Monika H and Peng, Pan},
  issn         = {1095-7146},
  journal      = {SIAM Journal on Discrete Mathematics},
  number       = {1},
  pages        = {130--162},
  publisher    = {Society for Industrial & Applied Mathematics},
  title        = {{Improved guarantees for vertex sparsification in planar graphs}},
  doi          = {10.1137/17m1163153},
  volume       = {34},
  year         = {2020},
}

@article{11954,
  abstract     = {The combination of nickel and photocatalysis has unlocked a variety of cross-couplings. These protocols rely on a few photocatalysts that can only convert a small portion of visible light (<500 nm) into chemical energy. The high-energy photons that excite the photocatalyst can result in unwanted side reactions. Dyes that absorb a much broader spectrum of light are not applicable because of their short-lived singlet excited states. Here, we describe a self-assembling catalyst system that overcomes this limitation. Immobilization of a nickel catalyst on dye-sensitized titanium dioxide results in a material that catalyzes carbon–heteroatom and carbon–carbon bond formations. The modular approach of dye-sensitized metallaphotocatalysts accesses the entire visible light spectrum and allows tackling selectivity issues resulting from low wavelengths strategically. The concept overcomes current limitations of metallaphotocatalysis by unlocking the potential of dyes that were previously unsuitable.},
  author       = {Reischauer, Susanne and Strauss, Volker and Pieber, Bartholomäus},
  issn         = {2155-5435},
  journal      = {ACS Catalysis},
  number       = {22},
  pages        = {13269–13274},
  publisher    = {American Chemical Society},
  title        = {{Modular, self-assembling metallaphotocatalyst for cross-couplings using the full visible-light spectrum}},
  doi          = {10.1021/acscatal.0c03950},
  volume       = {10},
  year         = {2020},
}

@article{11966,
  abstract     = {The front cover artwork is provided by the group of Dr. Bartholomäus Pieber at the Max Planck Institute of Colloids and Interfaces (Germany). The image symbolizes the activation of a heterogeneous photocatalyst by visible light and its application for organic synthesis. Read the full text of the Review at 10.1002/cptc.202000014.},
  author       = {Gisbertz, Sebastian and Pieber, Bartholomäus},
  issn         = {2367-0932},
  journal      = {ChemPhotoChem},
  number       = {7},
  pages        = {454--454},
  publisher    = {Wiley},
  title        = {{Heterogeneous photocatalysis in organic synthesis}},
  doi          = {10.1002/cptc.202000137},
  volume       = {4},
  year         = {2020},
}

@article{11969,
  abstract     = {Photochemistry enables new synthetic means to form carbon–heteroatom bonds. Photocatalysts can catalyze carbon–heteroatom cross-couplings by electron or energy transfer either alone or in combination with a second catalyst. Photocatalyst-free methods are possible using photolabile substrates or by generating photoactive electron donor-acceptor complexes. This review summarizes and discusses the strategies used in light-mediated carbon–heteroatom bond formations based on the proposed mechanisms.},
  author       = {Cavedon, Cristian and Seeberger, Peter H. and Pieber, Bartholomäus},
  issn         = {1099-0690},
  journal      = {European Journal of Organic Chemistry},
  number       = {10},
  pages        = {1379--1392},
  publisher    = {Wiley},
  title        = {{Photochemical strategies for carbon–heteroatom bond formation}},
  doi          = {10.1002/ejoc.201901173},
  volume       = {2020},
  year         = {2020},
}

@article{11978,
  abstract     = {Dual photocatalysis and nickel catalysis can effect cross-coupling under mild conditions, but little is known about the in situ kinetics of this class of reactions. We report a comprehensive kinetic examination of a model carboxylate O-arylation, comparing a state-of-the-art homogeneous photocatalyst (Ir(ppy)3) with a competitive heterogeneous photocatalyst (graphitic carbon nitride). Experimental conditions were adjusted such that the nickel catalytic cycle is saturated with excited photocatalyst. This approach was designed to remove the role of the photocatalyst, by which only the intrinsic behaviors of the nickel catalytic cycles are observed. The two reactions did not display identical kinetics. Ir(ppy)3 deactivates the nickel catalytic cycle and creates more dehalogenated side product. Kinetic data for the reaction using Ir(ppy)3 supports a turnover-limiting reductive elimination. Graphitic carbon nitride gave higher selectivity, even at high photocatalyst-to-nickel ratios. The heterogeneous reaction also showed a rate dependence on aryl halide, indicating that oxidative addition plays a role in rate determination. The results argue against the current mechanistic hypothesis, which states that the photocatalyst is only involved to trigger reductive elimination.},
  author       = {Malik, Jamal A. and Madani, Amiera and Pieber, Bartholomäus and Seeberger, Peter H.},
  issn         = {1520-5126},
  journal      = {Journal of the American Chemical Society},
  number       = {25},
  pages        = {11042--11049},
  publisher    = {American Chemical Society},
  title        = {{Evidence for photocatalyst involvement in oxidative additions of nickel-catalyzed carboxylate O-arylations}},
  doi          = {10.1021/jacs.0c02848},
  volume       = {142},
  year         = {2020},
}

@article{11979,
  abstract     = {Dual photoredox/nickel-catalysed C–N cross-couplings suffer from low yields for electron-rich aryl halides. The formation of catalytically inactive nickel-black is responsible for this limitation and causes severe reproducibility issues. Here, we demonstrate that catalyst deactivation can be avoided by using a carbon nitride photocatalyst. The broad absorption of the heterogeneous photocatalyst enables wavelength-dependent control of the rate of reductive elimination to prevent nickel-black formation during the coupling of cyclic, secondary amines and aryl halides. A second approach, which is applicable to a broader set of electron-rich aryl halides, is to run the reactions at high concentrations to increase the rate of oxidative addition. Less nucleophilic, primary amines can be coupled with electron-rich aryl halides by stabilizing low-valent nickel intermediates with a suitable additive. The developed protocols enable reproducible, selective C–N cross-couplings of electron-rich aryl bromides and can also be applied for electron-poor aryl chlorides.},
  author       = {Gisbertz, Sebastian and Reischauer, Susanne and Pieber, Bartholomäus},
  issn         = {2520-1158},
  journal      = {Nature Catalysis},
  number       = {8},
  pages        = {611--620},
  publisher    = {Springer Nature},
  title        = {{Overcoming limitations in dual photoredox/nickel-catalysed C–N cross-couplings due to catalyst deactivation}},
  doi          = {10.1038/s41929-020-0473-6},
  volume       = {3},
  year         = {2020},
}