Approximating the independence number via the θ-function

نویسندگان

  • Noga Alon
  • Nabil Kahale
چکیده

We describe an approximation algorithm for the independence number of a graph. If a graph on n vertices has an independence number n/k + m for some fixed integer k ≥ 3 and some m > 0, the algorithm finds, in random polynomial time, an independent set of size Ω̃(m), improving the best known previous algorithm of Boppana and Halldorsson that finds an independent set of size Ω(m1/(k−1)) in such a graph. The algorithm is based on semidefinite programming, some properties of the Lovász θ-function of a graph and the recent algorithm of Karger, Motwani and Sudan for approximating the chromatic number of a graph. If the θ-function of an n vertex graph is at least Mn1−2/k for some absolute constant M , we describe another, related, efficient algorithm that finds an independent set of size k. Several examples show the limitations of the approach and the analysis together with some related arguments supply new results on the problem of estimating the largest possible ratio between the θ-function and the independence number of a graph on n vertices. ∗Department of Mathematics, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel and AT & T Bell Laboratories, Murray Hill, NJ 07974, USA. Email: [email protected]. Research supported in part by a USA-Israel BSF grant and by the Fund for Basic Research administered by the Israel Academy of Sciences. †AT & T Labs-Research, Murray Hill, NJ 07974. Email: [email protected]. This work was partly done while the author was at XEROX PARC, and partly at DIMACS.

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Mixed Roman domination and 2-independence in trees

‎‎Let $G=(V‎, ‎E)$ be a simple graph with vertex set $V$ and edge set $E$‎. ‎A {em mixed Roman dominating function} (MRDF) of $G$ is a function $f:Vcup Erightarrow {0,1,2}$ satisfying the condition that every element $xin Vcup E$ for which $f(x)=0$ is adjacent‎‎or incident to at least one element $yin Vcup E$ for which $f(y)=2$‎. ‎The weight of an‎‎MRDF $f$ is $sum _{xin Vcup E} f(x)$‎. ‎The mi...

متن کامل

Error bounds in approximating n-time differentiable functions of self-adjoint operators in Hilbert spaces via a Taylor's type expansion

On utilizing the spectral representation of selfadjoint operators in Hilbert spaces, some error bounds in approximating $n$-time differentiable functions of selfadjoint operators in Hilbert Spaces via a Taylor's type expansion are given.

متن کامل

On Minrank and the Lovász Theta Function

Two classical upper bounds on the Shannon capacity of graphs are the θ-function due to Lovász and the minrank parameter due to Haemers. We provide several explicit constructions of n-vertex graphs with a constant θ-function and minrank at least n for a constant δ > 0 (over various prime order fields). This implies a limitation on the θ-function-based algorithmic approach to approximating the mi...

متن کامل

Estimating a Bounded Normal Mean Under the LINEX Loss Function

Let X be a random variable from a normal distribution with unknown mean θ and known variance σ2. In many practical situations, θ is known in advance to lie in an interval, say [−m,m], for some m > 0. As the usual estimator of θ, i.e., X under the LINEX loss function is inadmissible, finding some competitors for X becomes worthwhile. The only study in the literature considered the problem of min...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 1994