Lunches on Algo Events
https://algo.ulb.be/events/lunches/
Recent content in Lunches on Algo EventsHugo -- gohugo.ioen-usWed, 11 Mar 2020 11:30:00 +0000Packing and covering balls in graphs excluding a minor
https://algo.ulb.be/events/lunch/2020/03/11/packing-and-covering-balls-in-graphs-excluding-a-minor/
Wed, 11 Mar 2020 11:30:00 +0000https://algo.ulb.be/events/lunch/2020/03/11/packing-and-covering-balls-in-graphs-excluding-a-minor/Given a graph $G$, the ball centered at vertex $v$ of radius $r$ is the set containing all vertices at distance at most $r$ from $v$. We prove that for every integer $t\ge 1$ there exists a constant $c_t$ such that for every $K_t$-minor-free graph $G$, and every set $S$ of balls in $G$, the minimum size of a set of vertices of $G$ intersecting all the balls of $S$ is at most $c_t$ times the maximum number of vertex-disjoint balls in $S$.Around the Petersen Colouring Conjecture
https://algo.ulb.be/events/lunch/2020/02/19/around-the-petersen-colouring-conjecture/
Wed, 19 Feb 2020 11:30:00 +0000https://algo.ulb.be/events/lunch/2020/02/19/around-the-petersen-colouring-conjecture/A number of old conjectures related to edge-colourings of 3-regular graphs remain vastly open. Among them, the Petersen colouring conjecture is a very strong statement, which implies most of these, such as the Berge—Fulkerson conjecture, and the 5-Cycle-double-cover conjecture. It states that every bridgeless cubic graph admits an edge-colouring with 5 colours such that for every edge e, the set of colours assigned to the edges adjacent to e has cardinality either 2 or 4, but not 3.Bipartite Diameter and Other Measures Under Translation
https://algo.ulb.be/events/lunch/2019/11/21/bipartite-diameter-and-other-measures-under-translation/
Thu, 21 Nov 2019 11:30:00 +0000https://algo.ulb.be/events/lunch/2019/11/21/bipartite-diameter-and-other-measures-under-translation/Let A and B be two sets of points in R^d, where |A|=|B|=n and the distance between them is defined by some bipartite measure dist(A,B). We study several problems in which the goal is to translate the set B, so that dist(A, B) is minimized. The main measures that we consider are
(i) the diameter in two and three dimensions, that is diam(A,B) = max {d(a,b) : a in A, b in B}, where d(a,b) is the Euclidean distance between $a$ and $b$,On Grammars, Polytopes, and Groups
https://algo.ulb.be/events/lunch/2019/11/08/on-grammars-polytopes-and-groups/
Fri, 08 Nov 2019 11:30:00 +0000https://algo.ulb.be/events/lunch/2019/11/08/on-grammars-polytopes-and-groups/A fundamental step towards solving combinatorial problems using techniques from linear programming theory is to encode the space of feasible solutions for such problems as the set of vertices of polytopes of small extension complexity.
In this work, we establish several connections between the extension complexity of polytopes, formal language theory, and group theory. In particular, we introduce the notion of homogeneous context-free grammars and show that polytopes corresponding to languages accepted by polynomial-size non-uniform families of grammars with polynomial homogeneity have polynomial extension complexity.Coloring and Maximum Weight Independent Set of rectangles
https://algo.ulb.be/events/lunch/2019/11/06/coloring-and-maximum-weight-independent-set-of-rectangles/
Wed, 06 Nov 2019 11:30:00 +0000https://algo.ulb.be/events/lunch/2019/11/06/coloring-and-maximum-weight-independent-set-of-rectangles/We prove that every intersection graph of axis-parallel rectangles in the plane with clique number ω has chromatic number O(ω log ω), which is the first improvement of the original O(ω²) bound of Asplund and Grünbaum from 1960. As a consequence, we obtain a polynomial-time O(log log n)-approximation algorithm for Maximum Weight Independent Set in axis-parallel rectangles, improving the previous best approximation ratio of O(log n/log log n).
Joint work with Parinya Chalermsook.Exponential Separation between Quantum Communication and Logarithm of Approximate Rank
https://algo.ulb.be/events/lunch/2019/09/11/exponential-separation-between-quantum-communication-and-logarithm-of-approximate-rank/
Wed, 11 Sep 2019 10:30:00 +0000https://algo.ulb.be/events/lunch/2019/09/11/exponential-separation-between-quantum-communication-and-logarithm-of-approximate-rank/<p>Chattopadhyay, Mande and Sherif (to appear in STOC 2019) recently
exhibited a total Boolean function, the sink function, that has
polynomial approximate rank and polynomial randomized communication
complexity. This gives an exponential separation between randomized
communication complexity and logarithm of the approximate rank, refuting
the log-approximate-rank conjecture. We show that even the quantum
communication complexity of the sink function is polynomial, thus also
refuting the quantum log-approximate-rank conjecture.</p>3D Snap Rounding
https://algo.ulb.be/events/lunch/2019/06/19/3d-snap-rounding/
Wed, 19 Jun 2019 10:30:00 +0000https://algo.ulb.be/events/lunch/2019/06/19/3d-snap-rounding/Many computational geometry algorithms require greater accuracy for output than for input. So, to send or use the output, we often need to round it off. If this is done naively, intersections can occur during rounding. An algorithm from Devillers, Lenhart, Lazard was presented last year to solve this problem. The worst case of this algorithm is \(O(n^15)\). An implementation of this algorithm shows that on average, it is \(O(n \sqrt{n})\).A time- and space-optimal algorithm for the many-visits TSP
https://algo.ulb.be/events/lunch/2019/05/29/a-time-and-space-optimal-algorithm-for-the-many-visits-tsp/
Wed, 29 May 2019 10:30:00 +0000https://algo.ulb.be/events/lunch/2019/05/29/a-time-and-space-optimal-algorithm-for-the-many-visits-tsp/The many-visits traveling salesperson problem (MV-TSP) asks for an optimal tour of n cities that visits each city c a prescribed number kcof times. Travel costs may not be symmetric, and visiting a city twice in a row may incur a non-zero cost. The MV-TSP problem finds applications in scheduling, geometric approximation, and Hamiltonicity of certain graph families.
The fastest known algorithm for MV-TSP is due to Cosmadakis and Papadimitriou (SICOMP, 1984).Maintaining Perfect Matchings at Low Cost
https://algo.ulb.be/events/lunch/2019/05/10/maintaining-perfect-matchings-at-low-cost/
Fri, 10 May 2019 10:30:00 +0000https://algo.ulb.be/events/lunch/2019/05/10/maintaining-perfect-matchings-at-low-cost/The min-cost matching problem suffers from being very sensitive to small changes of the input. Even in a simple setting, e.g., when the costs come from the metric on the line, adding two nodes to the input might change the optimal solution completely. On the other hand, one expects that small changes in the input should incur only small changes on the constructed solutions, measured as the number of modified edges.Extended formulations from communication protocols in output-efficient time
https://algo.ulb.be/events/lunch/2019/05/02/extended-formulations-from-communication-protocols-in-output-efficient-time/
Thu, 02 May 2019 10:30:00 +0000https://algo.ulb.be/events/lunch/2019/05/02/extended-formulations-from-communication-protocols-in-output-efficient-time/Deterministic protocols are well-known tools to obtain extended formulations, with many applications to polytopes arising in combinatorial optimization. Although constructive, those tools are not output-efficient, since the time needed to produce the extended formulation also depends on the size of the slack matrix (hence, of the exact description in the original space). We give general sufficient conditions under which those tools can be implemented as to be output-efficient. In particular we apply this to Yannakakis' extended formulation for the stable set polytope of perfect graphs, for which, to the best of our knowledge, an efficient construction was previously not known.Encoding Two-Dimensional Range Top-k Queries Revisited
https://algo.ulb.be/events/lunch/2019/04/24/encoding-two-dimensional-range-top-k-queries-revisited/
Wed, 24 Apr 2019 10:30:00 +0000https://algo.ulb.be/events/lunch/2019/04/24/encoding-two-dimensional-range-top-k-queries-revisited/We consider the problem of encoding two-dimensional arrays, whose elements come from a total order, for answering Top-k queries. The aim is to obtain encodings that use space close to the information-theoretic lower bound, which can be constructed efficiently. For 2 x n arrays, we first give upper and lower bounds on space for answering sorted and unsorted 3-sided Top-k queries. For m x n arrays, with m <=n and k <=mn, we obtain (m lg{(k+1)n choose n}+4nm(m-1)+o(n))-bit encoding for answering sorted 4-sided Top-k queries.Universal Semiorders
https://algo.ulb.be/events/lunch/2019/03/28/universal-semiorders/
Thu, 28 Mar 2019 11:30:00 +0000https://algo.ulb.be/events/lunch/2019/03/28/universal-semiorders/Semiorders are binary relations that are complete, Ferrers, and semitransitive. In particu- lar, they display a transitive asymmetric part (strict preference), and a usually intransitive symmetric part (indifference). Semiorders are among the most studied categories of binary relations in preference modeling. This is due to the vast range of economic scenarios which can modelled by appealing to the notion of ‘just noticeable difference’. We give a univer- sal characterization of semiorders, which uses the notions of a Z-product and a Z-line.Fractional coloring with local demands
https://algo.ulb.be/events/lunch/2019/03/27/fractional-coloring-with-local-demands/
Wed, 27 Mar 2019 11:30:00 +0000https://algo.ulb.be/events/lunch/2019/03/27/fractional-coloring-with-local-demands/In a fractional coloring, vertices of a graph are assigned subsets of the [0, 1]-interval such that adjacent vertices receive disjoint subsets. The fractional chromatic number of a graph is at most k if it admits a fractional coloring in which the amount of "color" assigned to each vertex is at least 1/k. We investigate fractional colorings where vertices "demand" different amounts of color, determined by local parameters such as the degree of a vertex.From Italian menus to resolutions of convex geometries
https://algo.ulb.be/events/lunch/2019/03/01/from-italian-menus-to-resolutions-of-convex-geometries/
Fri, 01 Mar 2019 11:30:00 +0000https://algo.ulb.be/events/lunch/2019/03/01/from-italian-menus-to-resolutions-of-convex-geometries/A typical two-stage process governs the selection of meal items in an Italian menu. The process admits a direct formalization in terms of choice spaces. Path-independent choice spaces are cryptomorphic to convex geometries (or antimatroids, introduced by Robert E. Jamison). There results a construction of a new convex geometry for a convex geometry (the base) given together with a family of convex geometries (the fibers) indexed by the elements of the base; we call the outcome a resolution.Volume estimation by a new annealing schedule for cooling convex bodies
https://algo.ulb.be/events/lunch/2019/02/01/volume-estimation-by-a-new-annealing-schedule-for-cooling-convex-bodies/
Fri, 01 Feb 2019 11:30:00 +0000https://algo.ulb.be/events/lunch/2019/02/01/volume-estimation-by-a-new-annealing-schedule-for-cooling-convex-bodies/We experimentally study the problem of estimating the volume of convex polytopes, focusing on H- and V-polytopes, as well as zonotopes. Although a lot of effort is devoted to practical algorithms for H-polytopes there is no such method for the latter two representations. We propose a new, practical method for all representations, which is faster on H-polytopes; it relies on Hit-and-Run (HnR) sampling, and combines a new simulated annealing method with the Multiphase Monte Carlo (MMC) approach.Computing a maximum independent set in a graph embedded in a fixed surface when the odd cycle packing number is bounded
https://algo.ulb.be/events/lunch/2019/01/16/computing-a-maximum-independent-set-in-a-graph-embedded-in-a-fixed-surface-when-the-odd-cycle-packing-number-is-bounded/
Wed, 16 Jan 2019 11:30:00 +0000https://algo.ulb.be/events/lunch/2019/01/16/computing-a-maximum-independent-set-in-a-graph-embedded-in-a-fixed-surface-when-the-odd-cycle-packing-number-is-bounded/Tomorrow Sam will tell us how to compute a maximum independent set in a graph embedded in a fixed surface if there are not many disjoint odd cycles in the graph.
Note the unusual room: NO8.202 ("petit séminaire"), because of exams taking place in the other rooms.Finding a Maximum-Weight Convex Set in a Chordal Graph
https://algo.ulb.be/events/lunch/2018/11/21/finding-a-maximum-weight-convex-set-in-a-chordal-graph/
Wed, 21 Nov 2018 11:30:00 +0000https://algo.ulb.be/events/lunch/2018/11/21/finding-a-maximum-weight-convex-set-in-a-chordal-graph/TBA
https://algo.ulb.be/events/lunch/2018/11/14/tba/
Wed, 14 Nov 2018 11:30:00 +0000https://algo.ulb.be/events/lunch/2018/11/14/tba/Hypergraphic polytopes and flip graphs
https://algo.ulb.be/events/lunch/2018/11/07/hypergraphic-polytopes-and-flip-graphs/
Wed, 07 Nov 2018 11:30:00 +0000https://algo.ulb.be/events/lunch/2018/11/07/hypergraphic-polytopes-and-flip-graphs/The cage problem
https://algo.ulb.be/events/lunch/2018/10/24/the-cage-problem/
Wed, 24 Oct 2018 10:30:00 +0000https://algo.ulb.be/events/lunch/2018/10/24/the-cage-problem/Smoothed Analysis of the Art Gallery Problem
https://algo.ulb.be/events/lunch/2018/10/17/smoothed-analysis-of-the-art-gallery-problem/
Wed, 17 Oct 2018 10:30:00 +0000https://algo.ulb.be/events/lunch/2018/10/17/smoothed-analysis-of-the-art-gallery-problem/Almost all string graphs are intersection graphs of plane convex sets
https://algo.ulb.be/events/lunch/2018/10/10/almost-all-string-graphs-are-intersection-graphs-of-plane-convex-sets/
Wed, 10 Oct 2018 10:30:00 +0000https://algo.ulb.be/events/lunch/2018/10/10/almost-all-string-graphs-are-intersection-graphs-of-plane-convex-sets/Designing efficient algorithms for modern GPU architectures
https://algo.ulb.be/events/lunch/2018/10/03/designing-efficient-algorithms-for-modern-gpu-architectures/
Wed, 03 Oct 2018 10:30:00 +0000https://algo.ulb.be/events/lunch/2018/10/03/designing-efficient-algorithms-for-modern-gpu-architectures/Sparse Kneser graphs are hamiltonian
https://algo.ulb.be/events/lunch/2018/08/29/sparse-kneser-graphs-are-hamiltonian/
Wed, 29 Aug 2018 10:30:00 +0000https://algo.ulb.be/events/lunch/2018/08/29/sparse-kneser-graphs-are-hamiltonian/Data Structures Lower Bounds
https://algo.ulb.be/events/lunch/2018/07/24/data-structures-lower-bounds/
Tue, 24 Jul 2018 10:30:00 +0000https://algo.ulb.be/events/lunch/2018/07/24/data-structures-lower-bounds/Dynamic Trees with Almost-Optimal Access Cost
https://algo.ulb.be/events/lunch/2018/07/11/dynamic-trees-with-almost-optimal-access-cost/
Wed, 11 Jul 2018 10:30:00 +0000https://algo.ulb.be/events/lunch/2018/07/11/dynamic-trees-with-almost-optimal-access-cost/Orthogonal Point Location and Rectangle Stabbing Queries in 3-d
https://algo.ulb.be/events/lunch/2018/07/04/orthogonal-point-location-and-rectangle-stabbing-queries-in-3-d/
Wed, 04 Jul 2018 10:30:00 +0000https://algo.ulb.be/events/lunch/2018/07/04/orthogonal-point-location-and-rectangle-stabbing-queries-in-3-d/Sorting in the Asymmetric External Memory Model
https://algo.ulb.be/events/lunch/2018/06/27/sorting-in-the-asymmetric-external-memory-model/
Wed, 27 Jun 2018 10:30:00 +0000https://algo.ulb.be/events/lunch/2018/06/27/sorting-in-the-asymmetric-external-memory-model/Dimension of posets whose cover graphs exclude some minor
https://algo.ulb.be/events/lunch/2018/05/30/dimension-of-posets-whose-cover-graphs-exclude-some-minor/
Wed, 30 May 2018 10:30:00 +0000https://algo.ulb.be/events/lunch/2018/05/30/dimension-of-posets-whose-cover-graphs-exclude-some-minor/Homomorphism bounds for K4-minor-free graphs
https://algo.ulb.be/events/lunch/2018/05/08/homomorphism-bounds-for-k4-minor-free-graphs/
Tue, 08 May 2018 10:30:00 +0000https://algo.ulb.be/events/lunch/2018/05/08/homomorphism-bounds-for-k4-minor-free-graphs/Crossing Numbers
https://algo.ulb.be/events/lunch/2018/04/25/crossing-numbers/
Wed, 25 Apr 2018 10:30:00 +0000https://algo.ulb.be/events/lunch/2018/04/25/crossing-numbers/Quantum SDP-Solvers: Better upper bounds
https://algo.ulb.be/events/lunch/2018/04/11/quantum-sdp-solvers-better-upper-bounds/
Wed, 11 Apr 2018 10:00:00 +0000https://algo.ulb.be/events/lunch/2018/04/11/quantum-sdp-solvers-better-upper-bounds/Sorting and selection in restricted models
https://algo.ulb.be/events/lunch/2018/03/28/sorting-and-selection-in-restricted-models/
Wed, 28 Mar 2018 10:30:00 +0000https://algo.ulb.be/events/lunch/2018/03/28/sorting-and-selection-in-restricted-models/Inverses of Trees
https://algo.ulb.be/events/lunch/2018/03/21/inverses-of-trees/
Wed, 21 Mar 2018 11:30:00 +0000https://algo.ulb.be/events/lunch/2018/03/21/inverses-of-trees/Cuboids, a class of clutters
https://algo.ulb.be/events/lunch/2018/03/13/cuboids-a-class-of-clutters/
Tue, 13 Mar 2018 11:30:00 +0000https://algo.ulb.be/events/lunch/2018/03/13/cuboids-a-class-of-clutters/Short Rainbow Cycles in Sparse Graphs
https://algo.ulb.be/events/lunch/2018/03/07/short-rainbow-cycles-in-sparse-graphs/
Wed, 07 Mar 2018 10:00:00 +0000https://algo.ulb.be/events/lunch/2018/03/07/short-rainbow-cycles-in-sparse-graphs/Let \(G\) be a simple \(n\)-vertex graph and \(c\) be a colouring of \(E(G)\) with \(n\) colours, where each colour class has size at least \(2\). We prove that \(G\) contains a rainbow cycle of length at most \(\lceil \frac{n}{2} \rceil\), which is best possible. Our result settles a special case of a strengthening of the Caccetta-Häggkvist conjecture, due to Aharoni. We also show that the matroid generalization of our main result also holds for cographic matroids, but fails for binary matroids.Fast Fencing
https://algo.ulb.be/events/lunch/2018/02/28/fast-fencing/
Wed, 28 Feb 2018 11:30:00 +0000https://algo.ulb.be/events/lunch/2018/02/28/fast-fencing/Algorithms for k-Server Problems
https://algo.ulb.be/events/lunch/2018/02/21/algorithms-for-k-server-problems/
Wed, 21 Feb 2018 11:30:00 +0000https://algo.ulb.be/events/lunch/2018/02/21/algorithms-for-k-server-problems/Graph Embedding inside a polygon
https://algo.ulb.be/events/lunch/2018/01/31/graph-embedding-inside-a-polygon/
Wed, 31 Jan 2018 11:30:00 +0000https://algo.ulb.be/events/lunch/2018/01/31/graph-embedding-inside-a-polygon/Dynamic Spanning Forest: Techniques and Connections to Other Fields
https://algo.ulb.be/events/lunch/2018/01/17/dynamic-spanning-forest-techniques-and-connections-to-other-fields/
Wed, 17 Jan 2018 12:00:00 +0000https://algo.ulb.be/events/lunch/2018/01/17/dynamic-spanning-forest-techniques-and-connections-to-other-fields/Discrete time quantum walks and quantum search
https://algo.ulb.be/events/lunch/2017/12/06/discrete-time-quantum-walks-and-quantum-search/
Wed, 06 Dec 2017 11:00:00 +0000https://algo.ulb.be/events/lunch/2017/12/06/discrete-time-quantum-walks-and-quantum-search/Convex hulls in the presence of obstacles
https://algo.ulb.be/events/lunch/2017/11/27/convex-hulls-in-the-presence-of-obstacles/
Mon, 27 Nov 2017 11:00:00 +0000https://algo.ulb.be/events/lunch/2017/11/27/convex-hulls-in-the-presence-of-obstacles/Coloring Jordan regions and Jordan curves
https://algo.ulb.be/events/lunch/2017/11/22/coloring-jordan-regions-and-jordan-curves/
Wed, 22 Nov 2017 11:00:00 +0000https://algo.ulb.be/events/lunch/2017/11/22/coloring-jordan-regions-and-jordan-curves/Is Area-Universality UETR-complete?
https://algo.ulb.be/events/lunch/2017/11/15/is-area-universality-uetr-complete/
Wed, 15 Nov 2017 11:00:00 +0000https://algo.ulb.be/events/lunch/2017/11/15/is-area-universality-uetr-complete/Lower bounds for quantum sorting
https://algo.ulb.be/events/lunch/2017/11/08/lower-bounds-for-quantum-sorting/
Wed, 08 Nov 2017 11:00:00 +0000https://algo.ulb.be/events/lunch/2017/11/08/lower-bounds-for-quantum-sorting/Incidence bounds and kernelization
https://algo.ulb.be/events/lunch/2017/10/18/incidence-bounds-and-kernelization/
Wed, 18 Oct 2017 10:30:00 +0000https://algo.ulb.be/events/lunch/2017/10/18/incidence-bounds-and-kernelization/Fine-grained complexity of coloring unit disks and balls
https://algo.ulb.be/events/lunch/2017/10/04/fine-grained-complexity-of-coloring-unit-disks-and-balls/
Wed, 04 Oct 2017 10:30:00 +0000https://algo.ulb.be/events/lunch/2017/10/04/fine-grained-complexity-of-coloring-unit-disks-and-balls/Bounding techniques for extension complexity
https://algo.ulb.be/events/lunch/2017/06/13/bounding-techniques-for-extension-complexity/
Tue, 13 Jun 2017 10:30:00 +0000https://algo.ulb.be/events/lunch/2017/06/13/bounding-techniques-for-extension-complexity/Intersection Graphs of Rays and Grounded Segments
https://algo.ulb.be/events/lunch/2017/06/06/intersection-graphs-of-rays-and-grounded-segments/
Tue, 06 Jun 2017 10:30:00 +0000https://algo.ulb.be/events/lunch/2017/06/06/intersection-graphs-of-rays-and-grounded-segments/Excluded minors for isometric embeddings of graphs in $\ell_\infty^k$-spaces
https://algo.ulb.be/events/lunch/2017/05/31/excluded-minors-for-isometric-embeddings-of-graphs-in-%5Cell_%5Cinftyk-spaces/
Wed, 31 May 2017 10:30:00 +0000https://algo.ulb.be/events/lunch/2017/05/31/excluded-minors-for-isometric-embeddings-of-graphs-in-%5Cell_%5Cinftyk-spaces/Permutations and partitions
https://algo.ulb.be/events/lunch/2017/05/24/permutations-and-partitions/
Wed, 24 May 2017 10:30:00 +0000https://algo.ulb.be/events/lunch/2017/05/24/permutations-and-partitions/The Art Gallery Problem is $\exists \mathbb{R}$-complete
https://algo.ulb.be/events/lunch/2017/05/17/the-art-gallery-problem-is-%5Cexists-%5Cmathbbr-complete/
Wed, 17 May 2017 10:30:00 +0000https://algo.ulb.be/events/lunch/2017/05/17/the-art-gallery-problem-is-%5Cexists-%5Cmathbbr-complete/On the Rectilinear Convex Hull of a planar point set and its generalizations
https://algo.ulb.be/events/lunch/2017/05/03/on-the-rectilinear-convex-hull-of-a-planar-point-set-and-its-generalizations/
Wed, 03 May 2017 10:30:00 +0000https://algo.ulb.be/events/lunch/2017/05/03/on-the-rectilinear-convex-hull-of-a-planar-point-set-and-its-generalizations/Irrational Guards are sometimes needed
https://algo.ulb.be/events/lunch/2017/03/27/irrational-guards-are-sometimes-needed/
Mon, 27 Mar 2017 10:30:00 +0000https://algo.ulb.be/events/lunch/2017/03/27/irrational-guards-are-sometimes-needed/Monotone expanders
https://algo.ulb.be/events/lunch/2017/03/22/monotone-expanders/
Wed, 22 Mar 2017 11:30:00 +0000https://algo.ulb.be/events/lunch/2017/03/22/monotone-expanders/Medianwidths of graphs
https://algo.ulb.be/events/lunch/2017/03/08/medianwidths-of-graphs/
Wed, 08 Mar 2017 11:30:00 +0000https://algo.ulb.be/events/lunch/2017/03/08/medianwidths-of-graphs/Coloring graphs with no short cycles
https://algo.ulb.be/events/lunch/2017/03/01/coloring-graphs-with-no-short-cycles/
Wed, 01 Mar 2017 11:30:00 +0000https://algo.ulb.be/events/lunch/2017/03/01/coloring-graphs-with-no-short-cycles/Generalizations of the geometric de Bruijn-Erdos Theorem
https://algo.ulb.be/events/lunch/2017/02/15/generalizations-of-the-geometric-de-bruijn-erdos-theorem/
Wed, 15 Feb 2017 11:30:00 +0000https://algo.ulb.be/events/lunch/2017/02/15/generalizations-of-the-geometric-de-bruijn-erdos-theorem/A randomized constant factor approximation algorithm for Planar F-Deletion
https://algo.ulb.be/events/lunch/2017/02/01/a-randomized-constant-factor-approximation-algorithm-for-planar-f-deletion/
Wed, 01 Feb 2017 12:00:00 +0000https://algo.ulb.be/events/lunch/2017/02/01/a-randomized-constant-factor-approximation-algorithm-for-planar-f-deletion/Searching edges in the overlap of two plane graphs
https://algo.ulb.be/events/lunch/2017/01/18/searching-edges-in-the-overlap-of-two-plane-graphs/
Wed, 18 Jan 2017 11:00:00 +0000https://algo.ulb.be/events/lunch/2017/01/18/searching-edges-in-the-overlap-of-two-plane-graphs/Time-windowed graph connectivity
https://algo.ulb.be/events/lunch/2017/01/11/time-windowed-graph-connectivity/
Wed, 11 Jan 2017 11:00:00 +0000https://algo.ulb.be/events/lunch/2017/01/11/time-windowed-graph-connectivity/Digital materials and aerospace applications
https://algo.ulb.be/events/lunch/2016/12/14/digital-materials-and-aerospace-applications/
Wed, 14 Dec 2016 13:30:00 +0000https://algo.ulb.be/events/lunch/2016/12/14/digital-materials-and-aerospace-applications/
https://algo.ulb.be/events/lunch/2016/12/07/
Wed, 07 Dec 2016 11:00:00 +0000https://algo.ulb.be/events/lunch/2016/12/07/Characterizing Polytopes Contained in the 0/1-Cube with Bounded Chvatal-Gomory Rank
https://algo.ulb.be/events/lunch/2016/11/30/characterizing-polytopes-contained-in-the-0/1-cube-with-bounded-chvatal-gomory-rank/
Wed, 30 Nov 2016 11:00:00 +0000https://algo.ulb.be/events/lunch/2016/11/30/characterizing-polytopes-contained-in-the-0/1-cube-with-bounded-chvatal-gomory-rank/Transfinite Ford-Fulkerson on a Finite Network
https://algo.ulb.be/events/lunch/2016/11/23/transfinite-ford-fulkerson-on-a-finite-network/
Wed, 23 Nov 2016 11:00:00 +0000https://algo.ulb.be/events/lunch/2016/11/23/transfinite-ford-fulkerson-on-a-finite-network/<p>Today Tony will tell us about Transfinite Ford-Fulkerson on a Finite
Network.</p>Comparison of real roots (without numerical approximations)
https://algo.ulb.be/events/lunch/2016/11/16/comparison-of-real-roots-without-numerical-approximations/
Wed, 16 Nov 2016 11:00:00 +0000https://algo.ulb.be/events/lunch/2016/11/16/comparison-of-real-roots-without-numerical-approximations/Recognizing visibility graphs of polygons with holes is hard for the existential theory of the reals
https://algo.ulb.be/events/lunch/2016/11/09/recognizing-visibility-graphs-of-polygons-with-holes-is-hard-for-the-existential-theory-of-the-reals/
Wed, 09 Nov 2016 11:30:00 +0000https://algo.ulb.be/events/lunch/2016/11/09/recognizing-visibility-graphs-of-polygons-with-holes-is-hard-for-the-existential-theory-of-the-reals/The sandpile model on K_{m,n} and the rank of its configurations
https://algo.ulb.be/events/lunch/2016/10/19/the-sandpile-model-on-k_mn-and-the-rank-of-its-configurations/
Wed, 19 Oct 2016 12:15:00 +0000https://algo.ulb.be/events/lunch/2016/10/19/the-sandpile-model-on-k_mn-and-the-rank-of-its-configurations/
https://algo.ulb.be/events/lunch/1/01/01/
Mon, 01 Jan 0001 00:00:00 +0000https://algo.ulb.be/events/lunch/1/01/01/date: 2019-10-16T10:30:00.000Z title: 'Using hard-core distributions for sparse graph colouring' speakers:
François Pirot duration: PT1H location: Plaine campus, NO building, 8th floor, Rotule (P.2NO8.08) geolocation: latitude: 50.82005 longitude: 4.39767 tags: Graphs Coloring Graph Coloring Sparse Graphs Writing \(\mathcal{I}(G)\) for the collection of independent sets of a given graph \(G\), a random independent set \(\mathcal{B}\) drawn according to the hard-core distribution at fugacity \(\lambda\) on \(\mathcal{I}(G)\) satisfies for every independent set \(I\in \mathcal{I}(G)\) that \(\Pr[\mathcal{B} = I] = \frac{\lambda^{|I|}}{Z_\lambda(G)}\), where \(Z_\lambda(G) = \sum_{I\in \mathcal{I}(G)} \lambda^{|I|}\) is a normalising factor, called the independence polynomial of \(G\).