TOPICS
Search

Translative Covering Density


The translative covering density theta_T(K) of a convex body K subset R^n is the infimum of the asymptotic upper densities of coverings of Euclidean space by translates of K. Let X subset R^n have only finitely many points in each bounded set, let Q_R=[-R,R]^n, and require K+X=R^n, where the sum is a Minkowski sum. Then

 theta_T(K)=inf_(X:K+X=R^n)vol_n(K)limsup_(R->infty)(|X intersection Q_R|)/((2R)^n),

where vol_n denotes n-dimensional volume, |X intersection Q_R| is the number of centers in the hypercube Q_R, and limsup is the supremum limit. The density counts overlaps with multiplicity.

The same infimum can be taken over periodic coverings with centers X=Lambda+T, where Lambda is a full-rank point lattice and T is a finite set of distinct coset representatives. Such a covering has density |T|vol_n(K)/covol(Lambda), where covol(Lambda) is the covolume. The number of cosets is unrestricted. Requiring just one coset gives the lattice covering density theta_L(K), so 1<=theta_T(K)<=theta_L(K).

Rogers (1957) proved the upper bound

 theta_T(K)<=nlnn+nlnlnn+5n

for every convex body K subset R^n with n>=3, where ln denotes the natural logarithm. For instance, the hypercube [0,1]^n has translative covering density 1.


See also

Circle Covering, Convex Body, Lattice Covering Density, Octahedron Covering, Packing Density, Point Lattice

Explore with Wolfram|Alpha

WolframAlpha

More things to try:

References

Rogers, C. A. "A Note on Coverings." Mathematika 4, 1-6, 1957. https://doi.org/10.1112/S0025579300001030.

Cite this as:

Weisstein, Eric W. "Translative Covering Density." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/TranslativeCoveringDensity.html

Subject classifications