Under the auspices of the Computational Complexity Foundation (CCF)

REPORTS > KEYWORD > COMBINATORICS:
Reports tagged with Combinatorics:
TR98-012 | 2nd February 1998
Meena Mahajan, V Vinay

#### Determinant: Old Algorithms, New Insights

In this paper we approach the problem of computing the characteristic
polynomial of a matrix from the combinatorial viewpoint. We present
several combinatorial characterizations of the coefficients of the
characteristic polynomial, in terms of walks and closed walks of
different kinds in the underlying graph. We develop algorithms based
more >>>

TR00-010 | 12th January 2000
Amitabha Roy, Christopher Wilson

#### Supermodels and Closed Sets

A {\em supermodel} is a satisfying assignment of a boolean formula
for which any small alteration, such as a single bit flip, can be
repaired by another small alteration, yielding a nearby
satisfying assignment. We study computational problems associated
with super models and some generalizations thereof. For general
formulas, ... more >>>

TR05-143 | 29th November 2005
Parikshit Gopalan

#### Constructing Ramsey Graphs from Boolean Function Representations

Explicit construction of Ramsey graphs or graphs with no large clique or independent set has remained a challenging open problem for a long time. While Erdos's probabilistic argument shows the existence of graphs on 2^n vertices with no clique or independent set of size 2n, the best known explicit constructions ... more >>>

TR09-068 | 1st September 2009
Dave Buchfuhrer, Chris Umans

#### Limits on the Social Welfare of Maximal-In-Range Auction Mechanisms

Many commonly-used auction mechanisms are maximal-in-range''. We show that any maximal-in-range mechanism for $n$ bidders and $m$ items cannot both approximate the social welfare with a ratio better than $\min(n, m^\eta)$ for any constant $\eta < 1/2$ and run in polynomial time, unless $NP \subseteq P/poly$. This significantly improves upon ... more >>>

TR09-085 | 14th September 2009
Christoph Behle, Andreas Krebs, Stephanie Reifferscheid

#### An Approach to characterize the Regular Languages in TC0 with Linear Wires

Revisions: 1

We consider the regular languages recognized by weighted threshold circuits with a linear number of wires.
We present a simple proof to show that parity cannot be computed by such circuits.
Our proofs are based on an explicit construction to restrict the input of the circuit such that the value ... more >>>

TR15-117 | 21st July 2015
Boris Bukh, Venkatesan Guruswami

#### An improved bound on the fraction of correctable deletions

Revisions: 1

We consider codes over fixed alphabets against worst-case symbol deletions. For any fixed $k \ge 2$, we construct a family of codes over alphabet of size $k$ with positive rate, which allow efficient recovery from a worst-case deletion fraction approaching $1-\frac{2}{k+1}$. In particular, for binary codes, we are able to ... more >>>

TR16-029 | 7th March 2016
Joshua Brakensiek, Venkatesan Guruswami

#### New hardness results for graph and hypergraph colorings

Finding a proper coloring of a $t$-colorable graph $G$ with $t$ colors is a classic NP-hard problem when $t\ge 3$. In this work, we investigate the approximate coloring problem in which the objective is to find a proper $c$-coloring of $G$ where $c \ge t$. We show that for all ... more >>>

TR18-096 | 13th May 2018
Venkatesan Guruswami, Andrii Riazanov

#### Beating Fredman-Komlós for perfect $k$-hashing

We say a subset $C \subseteq \{1,2,\dots,k\}^n$ is a $k$-hash code (also called $k$-separated) if for every subset of $k$ codewords from $C$, there exists a coordinate where all these codewords have distinct values. Understanding the largest possible rate (in bits), defined as $(\log_2 |C|)/n$, of a $k$-hash code is ... more >>>

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