STACS 2001

The Symposium on Theoretical Aspects of Computer Science (STACS) is held annually, alternating between France and Germany. The STACS meetings are organized jointly by the Special Interest Group for Theoretical Computer S- ence of the Gesellschaft fu r Informatik (GI) in Germany and the Maison de l Informatique et des Math ematiques Discr etes (MIMD) in France. STACS2001 was the 18th in this series, held in Dresden, February 15-17, 2001. PreviousSTACS symposia took placein Paris(1984),Saarbr ucken(1985), Orsay(1986),Passau(1987),Bordeaux(1988),Paderborn(1989),Rouen(1990), Hamburg(1991),Cachan(1992),Wu rzburg(1993),Caen(1994),Mu nchen(1995), Grenoble (1996), Lub eck (1997), Paris (1998), Trier (1999), and Lille (2000). It may be worth noting that in 2001 the symposium was held in one of the new states of reunited Germany for the r st time. The proceedings of all of these symposia have been published in the Lecture Notes in Computer Science series of Springer{Verlag. STACS has become one of the most important annual meetings in Europe for the theoretical computer science community. It covers a wide range of topics in the area of foundations of computer science: algorithms and data structures, automata and formallanguages,computationaland structuralcomplexity, logic, veri cation, and current challenges. This year, 153 submissions were received, mostly in electronic form, from more than 30 countries, with a fair portion from non{European countries. We would like to thank Jochen Bern who designed the electronic submission procedure which performed marvelously and was of great help to the program committee.

Includes supplementary material: sn.pub/extras

Inhalt
Invited Presentations.- Recurrence in Infinite Words.- Generalized Model-Checking Problems for First-Order Logic.- Myhill-Nerode Relations on Automatic Systems and the Completeness of Kleene Algebra.- Contributions.- 2-Nested Simulation Is Not Finitely Equationally Axiomatizable.- On the Difference between Polynomial-Time Many-One and Truth-Table Reducibilities on Distributional Problems.- Matching Polygonal Curves with Respect to the Fréchet Distance.- On the Class of Languages Recognizable by 1-Way Quantum Finite Automata.- Star-Free Open Languages and Aperiodic Loops.- A 5/2n 2-Lower Bound for the Multiplicative Complexity of n × n-Matrix Multiplication.- Evasiveness of Subgraph Containment and Related Properties.- On the Complexity of Computing Minimum Energy Consumption Broadcast Subgraphs.- On Presburger Liveness of Discrete Timed Automata.- Residual Finite State Automata.- Deterministic Radio Broadcasting at Low Cost.- The Existential Theory of Equations with Rational Constraints in Free Groups is PSPACEComplete.- Recursive Randomized Coloring Beats Fair Dice Random Colorings.- Randomness, Computability, and Density.- On Multipartition Communication Complexity.- Scalable Sparse Topologies with Small Spectrum.- Optimal Preemptive Scheduling on Uniform Processors with Non-decreasing Speed Ratios.- The UPS Problem.- Gathering of Asynchronous Oblivious Robots with Limited Visibility.- Generalized Langton's Ant: Dynamical Behavior and Complexity.- Optimal and Approximate Station Placement in Networks.- Learning Expressions over Monoids.- Efficient Recognition of Random Unsatisfiable k-SAT Instances by Spectral Methods.- On the Circuit Complexity of Random Generation Problems for Regular and Context-Free Languages.- Efficient Minimal Perfect Hashing in NearlyMinimal Space.- Small PCPs with Low Query Complexity.- Space Efficient Algorithms for Series-Parallel Graphs.- A Toolkit for First Order Extensions of Monadic Games.- Polynomial Time Approximation Schemes for MAX-BISECTION on Planar and Geometric Graphs.- Refining the Hierarchy of Blind Multicounter Languages.- A Simple Undecidable Problem: The Inclusion Problem for Finite Substitutions on ab*c.- New Results on Alternating and Non-deterministic Two-Dimensional Finite-State Automata.- The Complexity of Minimal Satisfiability Problems.- On the Minimal Hardware Complexity of Pseudorandom Function Generators.- Approximation Algorithms for Minimum Size 2-Connectivity Problems.- A Model Theoretic Proof of Büchi-Type Theorems and First-Order Logic for N-Free Pomsets.- An Ehrenfeucht-Fraïssé Approach to Collapse Results for First-Order Queries over Embedded Databases.- A New Logical Characterization of Büchi Automata.- A Primal-Dual Approximation Algorithm for the Survivable Network Design Problem in Hypergraph.- The Complexity of Copy Constant Detection in Parallel Programs.- Approximation Algorithms for the Bottleneck Stretch Factor Problem.- Semantical Principles in the Modal Logic of Coalgebras.- The #a = #b Pictures Are Recognizable.- A Logical Approach to Decidability of Hierarchies of Regular StarFree Languages.- Regular Languages Defined by Generalized First-Order Formulas with a Bounded Number of Bound Variables.- New Bounds on the OBDD-Size of Integer Multiplication via Universal Hashing.