Seminar Algorithms

Organizers

• dr hab. Marcin Pilipczuk, prof. UW

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List of talks

• Dec. 7, 2017, 12:15 p.m.
  Marcin Pilipczuk (Uniwrsytet Warszawski)
  The Erdős-Hajnal conjecture for caterpillars and their complements
  The celebrated Erdos-Hajnal conjecture states that for every proper hereditary graph class GG there exists a constant eps>0 such that every graph G in GG contains a clique or an independent set of size |V(G)|^eps. …

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• Nov. 23, 2017, 12:15 p.m.
  Irene Muz
  Half-integral linkages in highly connected directed graphs
  We study the half-integral k-Directed Disjoint Paths Problem (1/2 kDDPP) in highly strongly connected digraphs. The integral kDDPP is NP-complete even when restricted to instances where k=2, and the input graph is L-strongly connected, for …

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• Nov. 9, 2017, 12:15 p.m.
  Bart M. P. Jansen (Eindhoven University of Technology)
  Polynomial Kernels for Hitting Forbidden Minors under Structural Parameterizations
  We investigate polynomial-time preprocessing for the problem of hitting forbidden minors in a graph, using the framework of kernelization. For a fixed finite set of connected graphs F, the F-Deletion problem is the following: given …

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• July 6, 2017, 12:15 p.m.
  Brynmor Chapman (Massachusetts Institute of Technology)
  A Refutation of the Gotsman-Linial Conjecture
  A degree-$d$ polynomial threshold function is a function that can be written as the sign of a degree-$d$ polynomial on the Boolean hypercube.  Bounds on the sensitivity of polynomial threshold functions to small changes in …

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• June 8, 2017, 12:15 p.m.
  Marek Adamczyk (University of Warsaw)
  When the Optimum is also Blind: a New Perspective on Universal Optimization
  Consider the following variant of the set cover problem. We are given a universe $U={1,2,...,n}$ and a collection of subsets C={S_1,...,S_m} where each S_i is a subset of U. For every element u of U …

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• May 11, 2017, 12:15 p.m.
  Till Miltzow (Universit ́e libre de Bruxelles)
  The Art Gallery Problem is $\exists \mathbb{R}$-complete
  The \emph{art gallery problem} is a classical problem in computational geometry, introduced in 1973 by Viktor Klee. Given a simple polygon \poly and an integer $k$, the goal is to decide if there exists a …

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• April 20, 2017, 12:15 p.m.
  Marcin Wrochna (University of Warsaw)
  A topological approach related to Hedetniemi's conjecture
  Hedetniemi's 50 years old conjecture states that the chromatic number of the tensor product of graphs G,H is the minimum of the chromatic numbers of G and H. The conjecture has many interesting connections with …

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• March 23, 2017, 12:15 p.m.
  Paweł Rzążewski (Politechnika Warszawska)
  Fine-grained complexity of coloring disks, balls, and segments.
  On planar graphs, many classic algorithmic problems enjoy a certain ``square root phenomenon'' and can be solved significantly faster than what is known to be possible on general graphs: for example, Independent Set, 3-Coloring, Hamiltonian …

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• March 16, 2017, 12:15 p.m.
  Andreas Emil Feldmann (Charles University)
  The Complexity Landscape of Fixed-Parameter Directed Steiner Network Problems
  Given a directed graph G and a list (s1 , t1 ), . . . , (sk , tk ) of terminal pairs, the Directed Steiner Network problem asks for a minimum-cost subgraph of G …

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• March 9, 2017, 12:15 p.m.
  Konstanty Junosza-Szaniawski (Politechnika Warszawska)
  2,1)-labeling of unit disk intersection graphs
  We give a family of online algorithms for the classical coloring and the L(2,1)-labeling problems of unit disk intersection graphs. In the L(2,1)-labeling we ask for an assignment of non-negative integers to the vertices of …

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• Feb. 9, 2017, 12:15 p.m.
  Marthe Bonamy (Université de Bordeaux)
  Using region decomposition techniques for coloring problems
  We consider the problem of coloring the square of a planar graph that has no small cycle. We prove a conjecture of Dvorak, Kral, Nejedly, and Skrekovski that planar graphs of girth at least five …

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• Jan. 12, 2017, 12:15 p.m.
  O-joung Kwon (Technische Universitat Berlin)
  Parameterized complexity of Distance-Hereditary Vertex Deletion
  A graph is distance-hereditary if for any pair of vertices, their distance in every connected induced subgraph containing both vertices is the same as their distance in the original graph. Distance-hereditary graphs are exactly the …

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• Dec. 15, 2016, 12:15 p.m.
  Marcin Wrochna (University of Warsaw)
  tw)*n time
  Abstract: Knowing how small treewidth can be exploited algorithmically in NP-hard problems, we ask about speeding up classical polynomial-time algorithms to (quasi-)linear in the graph size, while keeping the dependency on treewidth polynomial. We provide …

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• Dec. 1, 2016, 12:15 p.m.
  Bartosz Walczak (Uniwersytet Jagielloński)
  Coloring graphs with geometric representations and related problems
  Colorings of graphs represented by geometric objects have been studied since the 1960s for both theoretical and practical reasons. In particular, geometric representations lead to natural examples of classes of graphs that are χ-bounded (near-perfect), …

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• Nov. 24, 2016, 12:15 p.m.
  Andrzej Grzesik
  Minimum number of edges that occur in odd cycles
  For any fixed k>1 every graph without a cycle on 2k+1 vertices has at most n^2/4 edges. In 1992, Erdos, Faudree and Rousseau conjectured that if a graph has at least n^2/4 + 1 edges, …

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