TY - GEN AB - The second mission of NASA’s Kepler satellite, K2, has collected hundreds of thousands of lightcurves for stars close to the ecliptic plane. This new sample could increase the number of known pulsating stars and then improve our understanding of those stars. For the moment only a few stars have been properly classified and published. In this work, we present a method to automaticly classify K2 pulsating stars using a Machine Learning technique called Random Forest. The objective is to sort out the stars in four classes: red giant (RG), main-sequence Solar-like stars (SL), classical pulsators (PULS) and Other. To do this we use the effective temperatures and the luminosities of the stars as well as the FliPer features, that measures the amount of power contained in the power spectral density. The classifier now retrieves the right classification for more than 80% of the stars. AU - Saux, A. Le AU - Bugnet, Lisa Annabelle AU - Mathur, S. AU - Breton, S. N. AU - Garcia, R. A. ID - 11630 KW - asteroseismology - methods KW - data analysis - thecniques KW - machine learning - stars KW - oscillations T2 - arXiv TI - Automatic classification of K2 pulsating stars using machine learning techniques ER - TY - CONF AB - The diameter, radius and eccentricities are natural graph parameters. While these problems have been studied extensively, there are no known dynamic algorithms for them beyond the ones that follow from trivial recomputation after each update or from solving dynamic All-Pairs Shortest Paths (APSP), which is very computationally intensive. This is the situation for dynamic approximation algorithms as well, and even if only edge insertions or edge deletions need to be supported. This paper provides a comprehensive study of the dynamic approximation of Diameter, Radius and Eccentricities, providing both conditional lower bounds, and new algorithms whose bounds are optimal under popular hypotheses in fine-grained complexity. Some of the highlights include: - Under popular hardness hypotheses, there can be no significantly better fully dynamic approximation algorithms than recomputing the answer after each update, or maintaining full APSP. - Nearly optimal partially dynamic (incremental/decremental) algorithms can be achieved via efficient reductions to (incremental/decremental) maintenance of Single-Source Shortest Paths. For instance, a nearly (3/2+epsilon)-approximation to Diameter in directed or undirected n-vertex, m-edge graphs can be maintained decrementally in total time m^{1+o(1)}sqrt{n}/epsilon^2. This nearly matches the static 3/2-approximation algorithm for the problem that is known to be conditionally optimal. AU - Ancona, Bertie AU - Henzinger, Monika H AU - Roditty, Liam AU - Williams, Virginia Vassilevska AU - Wein, Nicole ID - 11826 SN - 1868-8969 T2 - 46th International Colloquium on Automata, Languages, and Programming TI - Algorithms and hardness for diameter in dynamic graphs VL - 132 ER - TY - CONF AB - Modern networked systems are increasingly reconfigurable, enabling demand-aware infrastructures whose resources can be adjusted according to the workload they currently serve. Such dynamic adjustments can be exploited to improve network utilization and hence performance, by moving frequently interacting communication partners closer, e.g., collocating them in the same server or datacenter. However, dynamically changing the embedding of workloads is algorithmically challenging: communication patterns are often not known ahead of time, but must be learned. During the learning process, overheads related to unnecessary moves (i.e., re-embeddings) should be minimized. This paper studies a fundamental model which captures the tradeoff between the benefits and costs of dynamically collocating communication partners on l servers, in an online manner. Our main contribution is a distributed online algorithm which is asymptotically almost optimal, i.e., almost matches the lower bound (also derived in this paper) on the competitive ratio of any (distributed or centralized) online algorithm. AU - Henzinger, Monika H AU - Neumann, Stefan AU - Schmid, Stefan ID - 11850 SN - 978-1-4503-6678-6 T2 - SIGMETRICS'19: International Conference on Measurement and Modeling of Computer Systems TI - Efficient distributed workload (re-)embedding ER - TY - CHAP AB - This paper serves as a user guide to the Vienna graph clustering framework. We review our general memetic algorithm, VieClus, to tackle the graph clustering problem. A key component of our contribution are natural recombine operators that employ ensemble clusterings as well as multi-level techniques. Lastly, we combine these techniques with a scalable communication protocol, producing a system that is able to compute high-quality solutions in a short amount of time. After giving a description of the algorithms employed, we establish the connection of the graph clustering problem to protein–protein interaction networks and moreover give a description on how the software can be used, what file formats are expected, and how this can be used to find functional groups in protein–protein interaction networks. AU - Biedermann, Sonja AU - Henzinger, Monika H AU - Schulz, Christian AU - Schuster, Bernhard ED - Canzar, Stefan ED - Rojas Ringeling, Francisca ID - 11847 SN - 1064-3745 T2 - Protein-Protein Interaction Networks TI - Vienna Graph Clustering VL - 2074 ER - TY - CONF AB - We present a deterministic dynamic algorithm for maintaining a (1+ε)f-approximate minimum cost set cover with O(f log(Cn)/ε^2) amortized update time, when the input set system is undergoing element insertions and deletions. Here, n denotes the number of elements, each element appears in at most f sets, and the cost of each set lies in the range [1/C, 1]. Our result, together with that of Gupta~et~al.~[STOC'17], implies that there is a deterministic algorithm for this problem with O(f log(Cn)) amortized update time and O(min(log n, f)) -approximation ratio, which nearly matches the polynomial-time hardness of approximation for minimum set cover in the static setting. Our update time is only O(log (Cn)) away from a trivial lower bound. Prior to our work, the previous best approximation ratio guaranteed by deterministic algorithms was O(f^2), which was due to Bhattacharya~et~al.~[ICALP`15]. In contrast, the only result that guaranteed O(f) -approximation was obtained very recently by Abboud~et~al.~[STOC`19], who designed a dynamic algorithm with (1+ε)f-approximation ratio and O(f^2 log n/ε) amortized update time. Besides the extra O(f) factor in the update time compared to our and Gupta~et~al.'s results, the Abboud~et~al.~algorithm is randomized, and works only when the adversary is oblivious and the sets are unweighted (each set has the same cost). We achieve our result via the primal-dual approach, by maintaining a fractional packing solution as a dual certificate. This approach was pursued previously by Bhattacharya~et~al.~and Gupta~et~al., but not in the recent paper by Abboud~et~al. Unlike previous primal-dual algorithms that try to satisfy some local constraints for individual sets at all time, our algorithm basically waits until the dual solution changes significantly globally, and fixes the solution only where the fix is needed. AU - Bhattacharya, Sayan AU - Henzinger, Monika H AU - Nanongkai, Danupon ID - 11853 SN - 2575-8454 T2 - 60th Annual Symposium on Foundations of Computer Science TI - A new deterministic algorithm for dynamic set cover ER - TY - CONF AB - The minimum cut problem for an undirected edge-weighted graph asks us to divide its set of nodes into two blocks while minimizing the weighted sum of the cut edges. In this paper, we engineer the fastest known exact algorithm for the problem. State-of-the-art algorithms like the algorithm of Padberg and Rinaldi or the algorithm of Nagamochi, Ono and Ibaraki identify edges that can be contracted to reduce the graph size such that at least one minimum cut is maintained in the contracted graph. Our algorithm achieves improvements in running time over these algorithms by a multitude of techniques. First, we use a recently developed fast and parallel inexact minimum cut algorithm to obtain a better bound for the problem. Afterwards, we use reductions that depend on this bound to reduce the size of the graph much faster than previously possible. We use improved data structures to further lower the running time of our algorithm. Additionally, we parallelize the contraction routines of Nagamochi et al. . Overall, we arrive at a system that significantly outperforms the fastest state-of-the-art solvers for the exact minimum cut problem. AU - Henzinger, Monika H AU - Noe, Alexander AU - Schulz, Christian ID - 11851 SN - 978-1-7281-1247-3 T2 - 33rd International Parallel and Distributed Processing Symposium TI - Shared-memory exact minimum cuts ER - TY - CONF AB - We present the first sublinear-time algorithm that can compute the edge connectivity λ of a network exactly on distributed message-passing networks (the CONGEST model), as long as the network contains no multi-edge. We present the first sublinear-time algorithm for a distributed message-passing network sto compute its edge connectivity λ exactly in the CONGEST model, as long as there are no parallel edges. Our algorithm takes Õ(n1−1/353D1/353+n1−1/706) time to compute λ and a cut of cardinality λ with high probability, where n and D are the number of nodes and the diameter of the network, respectively, and Õ hides polylogarithmic factors. This running time is sublinear in n (i.e. Õ(n1−є)) whenever D is. Previous sublinear-time distributed algorithms can solve this problem either (i) exactly only when λ=O(n1/8−є) [Thurimella PODC’95; Pritchard, Thurimella, ACM Trans. Algorithms’11; Nanongkai, Su, DISC’14] or (ii) approximately [Ghaffari, Kuhn, DISC’13; Nanongkai, Su, DISC’14]. To achieve this we develop and combine several new techniques. First, we design the first distributed algorithm that can compute a k-edge connectivity certificate for any k=O(n1−є) in time Õ(√nk+D). The previous sublinear-time algorithm can do so only when k=o(√n) [Thurimella PODC’95]. In fact, our algorithm can be turned into the first parallel algorithm with polylogarithmic depth and near-linear work. Previous near-linear work algorithms are essentially sequential and previous polylogarithmic-depth algorithms require Ω(mk) work in the worst case (e.g. [Karger, Motwani, STOC’93]). Second, we show that by combining the recent distributed expander decomposition technique of [Chang, Pettie, Zhang, SODA’19] with techniques from the sequential deterministic edge connectivity algorithm of [Kawarabayashi, Thorup, STOC’15], we can decompose the network into a sublinear number of clusters with small average diameter and without any mincut separating a cluster (except the “trivial” ones). This leads to a simplification of the Kawarabayashi-Thorup framework (except that we are randomized while they are deterministic). This might make this framework more useful in other models of computation. Finally, by extending the tree packing technique from [Karger STOC’96], we can find the minimum cut in time proportional to the number of components. As a byproduct of this technique, we obtain an Õ(n)-time algorithm for computing exact minimum cut for weighted graphs. AU - Daga, Mohit AU - Henzinger, Monika H AU - Nanongkai, Danupon AU - Saranurak, Thatchaphol ID - 11865 SN - 0737-8017 T2 - Proceedings of the 51st Annual ACM SIGACT Symposium on Theory of Computing TI - Distributed edge connectivity in sublinear time ER - TY - CONF AB - Many dynamic graph algorithms have an amortized update time, rather than a stronger worst-case guarantee. But amortized data structures are not suitable for real-time systems, where each individual operation has to be executed quickly. For this reason, there exist many recent randomized results that aim to provide a guarantee stronger than amortized expected. The strongest possible guarantee for a randomized algorithm is that it is always correct (Las Vegas), and has high-probability worst-case update time, which gives a bound on the time for each individual operation that holds with high probability. In this paper we present the first polylogarithmic high-probability worst-case time bounds for the dynamic spanner and the dynamic maximal matching problem. 1. For dynamic spanner, the only known o(n) worst-case bounds were O(n3/4) high-probability worst-case update time for maintaining a 3-spanner, and O(n5/9) for maintaining a 5-spanner. We give a O(1)k log3(n) high-probability worst-case time bound for maintaining a (2k – 1)-spanner, which yields the first worst-case polylog update time for all constant k. (All the results above maintain the optimal tradeoff of stretch 2k – 1 and Õ(n1+1/k) edges.) 2. For dynamic maximal matching, or dynamic 2-approximate maximum matching, no algorithm with o(n) worst-case time bound was known and we present an algorithm with O(log5 (n)) high-probability worst-case time; similar worst-case bounds existed only for maintaining a matching that was (2 + ∊)-approximate, and hence not maximal. Our results are achieved using a new approach for converting amortized guarantees to worst-case ones for randomized data structures by going through a third type of guarantee, which is a middle ground between the two above: an algorithm is said to have worst-case expected update time α if for every update σ, the expected time to process σ is at most α. Although stronger than amortized expected, the worst-case expected guarantee does not resolve the fundamental problem of amortization: a worst-case expected update time of O(1) still allows for the possibility that every 1/f(n) updates requires Θ(f(n)) time to process, for arbitrarily high f(n). In this paper we present a black-box reduction that converts any data structure with worst-case expected update time into one with a high-probability worst-case update time: the query time remains the same, while the update time increases by a factor of O(log2(n)). Thus we achieve our results in two steps: (1) First we show how to convert existing dynamic graph algorithms with amortized expected polylogarithmic running times into algorithms with worst-case expected polylogarithmic running times. (2) Then we use our black-box reduction to achieve the polylogarithmic high-probability worst-case time bound. All our algorithms are Las-Vegas-type algorithms. AU - Bernstein, Aaron AU - Forster, Sebastian AU - Henzinger, Monika H ID - 11871 T2 - 30th Annual ACM-SIAM Symposium on Discrete Algorithms TI - A deamortization approach for dynamic spanner and dynamic maximal matching ER - TY - JOUR AB - We build upon the recent papers by Weinstein and Yu (FOCS'16), Larsen (FOCS'12), and Clifford et al. (FOCS'15) to present a general framework that gives amortized lower bounds on the update and query times of dynamic data structures. Using our framework, we present two concrete results. (1) For the dynamic polynomial evaluation problem, where the polynomial is defined over a finite field of size n1+Ω(1) and has degree n, any dynamic data structure must either have an amortized update time of Ω((lgn/lglgn)2) or an amortized query time of Ω((lgn/lglgn)2). (2) For the dynamic online matrix vector multiplication problem, where we get an n×n matrix whose entires are drawn from a finite field of size nΘ(1), any dynamic data structure must either have an amortized update time of Ω((lgn/lglgn)2) or an amortized query time of Ω(n⋅(lgn/lglgn)2). For these two problems, the previous works by Larsen (FOCS'12) and Clifford et al. (FOCS'15) gave the same lower bounds, but only for worst case update and query times. Our bounds match the highest unconditional lower bounds known till date for any dynamic problem in the cell-probe model. AU - Bhattacharya, Sayan AU - Henzinger, Monika H AU - Neumann, Stefan ID - 11898 JF - Theoretical Computer Science SN - 0304-3975 TI - New amortized cell-probe lower bounds for dynamic problems VL - 779 ER - TY - JOUR AB - Cross-coupling reactions mediated by dual nickel/photocatalysis are synthetically attractive but rely mainly on expensive, non-recyclable noble-metal complexes as photocatalysts. Heterogeneous semiconductors, which are commonly used for artificial photosynthesis and wastewater treatment, are a sustainable alternative. Graphitic carbon nitrides, a class of metal-free polymers that can be easily prepared from bulk chemicals, are heterogeneous semiconductors with high potential for photocatalytic organic transformations. Here, we demonstrate that graphitic carbon nitrides in combination with nickel catalysis can induce selective C−O cross-couplings of carboxylic acids with aryl halides, yielding the respective aryl esters in excellent yield and selectivity. The heterogeneous organic photocatalyst exhibits a broad substrate scope, is able to harvest green light, and can be recycled multiple times. In situ FTIR was used to track the reaction progress to study this transformation at different irradiation wavelengths and reaction scales. AU - Pieber, Bartholomäus AU - Malik, Jamal A. AU - Cavedon, Cristian AU - Gisbertz, Sebastian AU - Savateev, Aleksandr AU - Cruz, Daniel AU - Heil, Tobias AU - Zhang, Guigang AU - Seeberger, Peter H. ID - 11957 IS - 28 JF - Angewandte Chemie International Edition SN - 1433-7851 TI - Semi‐heterogeneous dual nickel/photocatalysis using carbon nitrides: Esterification of carboxylic acids with aryl halides VL - 58 ER - TY - JOUR AB - Differentially protected galactosamine building blocks are key components for the synthesis of human and bacterial oligosaccharides. The azidophenylselenylation of 3,4,6-tri-O-acetyl-d-galactal provides straightforward access to the corresponding 2-nitrogenated glycoside. Poor reproducibility and the use of azides that lead to the formation of potentially explosive and toxic species limit the scalability of this reaction and render it a bottleneck for carbohydrate synthesis. Here, we present a method for the safe, efficient, and reliable azidophenylselenylation of 3,4,6-tri-O-acetyl-d-galactal at room temperature, using continuous flow chemistry. Careful analysis of the transformation resulted in reaction conditions that produce minimal side products while the reaction time was reduced drastically when compared to batch reactions. The flow setup is readily scalable to process 5 mmol of galactal in 3 h, producing 1.2 mmol/h of product. AU - Guberman, Mónica AU - Pieber, Bartholomäus AU - Seeberger, Peter H. ID - 11984 IS - 12 JF - Organic Process Research and Development SN - 1083-6160 TI - Safe and scalable continuous flow azidophenylselenylation of galactal to prepare galactosamine building blocks VL - 23 ER - TY - JOUR AB - A carbon nitride material can be combined with homogeneous nickel catalysts for light-mediated cross-couplings of aryl bromides with alcohols under mild conditions. The metal-free heterogeneous semiconductor is fully recyclable and couples a broad range of electron-poor aryl bromides with primary and secondary alcohols as well as water. The application for intramolecular reactions and the synthesis of active pharmaceutical ingredients was demonstrated. The catalytic protocol is applicable for the coupling of aryl iodides with thiols as well. AU - Cavedon, Cristian AU - Madani, Amiera AU - Seeberger, Peter H. AU - Pieber, Bartholomäus ID - 11982 IS - 13 JF - Organic Letters SN - 1523-7060 TI - Semiheterogeneous dual nickel/photocatalytic (thio)etherification using carbon nitrides VL - 21 ER - TY - JOUR AB - Upper and lower bounds, of the expected order of magnitude, are obtained for the number of rational points of bounded height on any quartic del Pezzo surface over ℚ that contains a conic defined over ℚ . AU - Browning, Timothy D AU - Sofos, Efthymios ID - 170 IS - 3-4 JF - Mathematische Annalen TI - Counting rational points on quartic del Pezzo surfaces with a rational conic VL - 373 ER - TY - JOUR AU - Kalinin, Nikita AU - Shkolnikov, Mikhail ID - 441 IS - 3 JF - European Journal of Mathematics SN - 2199-675X TI - Tropical formulae for summation over a part of SL(2,Z) VL - 5 ER - TY - CHAP AB - The transcription coactivator, Yes-associated protein (YAP), which is a nuclear effector of the Hippo signaling pathway, has been shown to be a mechano-transducer. By using mutant fish and human 3D spheroids, we have recently demonstrated that YAP is also a mechano-effector. YAP functions in three-dimensional (3D) morphogenesis of organ and global body shape by controlling actomyosin-mediated tissue tension. In this chapter, we present a platform that links the findings in fish embryos with human cells. The protocols for analyzing tissue tension-mediated global body shape/organ morphogenesis in vivo and ex vivo using medaka fish embryos and in vitro using human cell spheroids represent useful tools for unraveling the molecular mechanisms by which YAP functions in regulating global body/organ morphogenesis. AU - Asaoka, Yoichi AU - Morita, Hitoshi AU - Furumoto, Hiroko AU - Heisenberg, Carl-Philipp J AU - Furutani-Seiki, Makoto ED - Hergovich, Alexander ID - 5793 SN - 978-1-4939-8909-6 T2 - The hippo pathway TI - Studying YAP-mediated 3D morphogenesis using fish embryos and human spheroids VL - 1893 ER - TY - JOUR AB - Cryptographic security is usually defined as a guarantee that holds except when a bad event with negligible probability occurs, and nothing is guaranteed in that bad case. However, in settings where such failure can happen with substantial probability, one needs to provide guarantees even for the bad case. A typical example is where a (possibly weak) password is used instead of a secure cryptographic key to protect a session, the bad event being that the adversary correctly guesses the password. In a situation with multiple such sessions, a per-session guarantee is desired: any session for which the password has not been guessed remains secure, independently of whether other sessions have been compromised. A new formalism for stating such gracefully degrading security guarantees is introduced and applied to analyze the examples of password-based message authentication and password-based encryption. While a natural per-message guarantee is achieved for authentication, the situation of password-based encryption is more delicate: a per-session confidentiality guarantee only holds against attackers for which the distribution of password-guessing effort over the sessions is known in advance. In contrast, for more general attackers without such a restriction, a strong, composable notion of security cannot be achieved. AU - Demay, Gregory AU - Gazi, Peter AU - Maurer, Ueli AU - Tackmann, Bjorn ID - 5887 IS - 1 JF - Journal of Computer Security SN - 0926227X TI - Per-session security: Password-based cryptography revisited VL - 27 ER - TY - CONF AB - We propose a new non-orthogonal basis to express the 3D Euclidean space in terms of a regular grid. Every grid point, each represented by integer 3-coordinates, corresponds to rhombic dodecahedron centroid. Rhombic dodecahedron is a space filling polyhedron which represents the close packing of spheres in 3D space and the Voronoi structures of the face centered cubic (FCC) lattice. In order to illustrate the interest of the new coordinate system, we propose the characterization of 3D digital plane with its topological features, such as the interrelation between the thickness of the digital plane and the separability constraint we aim to obtain. A characterization of a 3D digital sphere with relevant topological features is proposed as well with the help of a 48 symmetry that comes with the new coordinate system. AU - Biswas, Ranita AU - Largeteau-Skapin, Gaëlle AU - Zrour, Rita AU - Andres, Eric ID - 6163 SN - 0302-9743 T2 - 21st IAPR International Conference on Discrete Geometry for Computer Imagery TI - Rhombic dodecahedron grid—coordinate system and 3D digital object definitions VL - 11414 ER - TY - JOUR AB - We give non-degeneracy criteria for Riemannian simplices based on simplices in spaces of constant sectional curvature. It extends previous work on Riemannian simplices, where we developed Riemannian simplices with respect to Euclidean reference simplices. The criteria we give in this article are in terms of quality measures for spaces of constant curvature that we develop here. We see that simplices in spaces that have nearly constant curvature, are already non-degenerate under very weak quality demands. This is of importance because it allows for sampling of Riemannian manifolds based on anisotropy of the manifold and not (absolute) curvature. AU - Dyer, Ramsay AU - Vegter, Gert AU - Wintraecken, Mathijs ID - 6515 IS - 1 JF - Journal of Computational Geometry SN - 1920-180X TI - Simplices modelled on spaces of constant curvature VL - 10 ER - TY - CONF AB - We construct a verifiable delay function (VDF) by showing how the Rivest-Shamir-Wagner time-lock puzzle can be made publicly verifiable. Concretely, we give a statistically sound public-coin protocol to prove that a tuple (N,x,T,y) satisfies y=x2T (mod N) where the prover doesn’t know the factorization of N and its running time is dominated by solving the puzzle, that is, compute x2T, which is conjectured to require T sequential squarings. To get a VDF we make this protocol non-interactive using the Fiat-Shamir heuristic.The motivation for this work comes from the Chia blockchain design, which uses a VDF as akey ingredient. For typical parameters (T≤2 40, N= 2048), our proofs are of size around 10K B, verification cost around three RSA exponentiations and computing the proof is 8000 times faster than solving the puzzle even without any parallelism. AU - Pietrzak, Krzysztof Z ID - 6528 SN - 1868-8969 T2 - 10th Innovations in Theoretical Computer Science Conference TI - Simple verifiable delay functions VL - 124 ER - TY - CONF AB - In this paper, we address the problem of synthesizing periodic switching controllers for stabilizing a family of linear systems. Our broad approach consists of constructing a finite game graph based on the family of linear systems such that every winning strategy on the game graph corresponds to a stabilizing switching controller for the family of linear systems. The construction of a (finite) game graph, the synthesis of a winning strategy and the extraction of a stabilizing controller are all computationally feasible. We illustrate our method on an example. AU - Kundu, Atreyee AU - Garcia Soto, Miriam AU - Prabhakar, Pavithra ID - 6565 SN - 978-153866246-5 T2 - 5th Indian Control Conference Proceedings TI - Formal synthesis of stabilizing controllers for periodically controlled linear switched systems ER -