Lower bounds for local approximation

Lower Bounds for Approximation by Nonlinear Manifolds

which is the precision to which F approximates K. An instance of classical interest is that in which L is C([0, 1]), K is A"—i.e. those functions bounded by one, and whose modulus of continuity is dominated by the modulus of continuity function o>—and F is the family Pn of polynomials of degree n 1. For this case it is known that there are positive constants A and B, independent of to and n, su...

Lower Bounds and Approximation Guarantees

Some Lower Bounds for Estrada Index

Lower Bounds for Approximation Schemes for Closest String

In the Closest String problem one is given a family S of equal-length strings over some fixed alphabet, and the task is to find a string y that minimizes the maximum Hamming distance between y and a string from S. While polynomial-time approximation schemes (PTASes) for this problem are known for a long time [Li et al.; J. ACM’02], no efficient polynomial-time approximation scheme (EPTAS) has b...

Lower Bounds for Approximation Algorithms for the Steiner Tree Problem

The Steiner tree problem asks for a shortest subgraph connecting a given set of terminals in a graph. It is known to be APX-complete, which means that no polynomial time approximation scheme can exist for this problem, unless P=NP. Currently, the best approximation algorithm for the Steiner tree problem has a performance ratio of + , , whereas the corresponding lower bound is smaller than + , ....