2.3. Description of tables

The tables are arranged as follows.

Each table contains the list of all arrays that satisfy the necessary condition for intersection arrays of completely regular codes in hypercubes with fixed ρ from 1 to 8 and with the intersection number b0 bounded by 32 or 36 (in the case ρ=1, the sum b0+c1 is bounded by 64). The arrays are ordered lexicographically (except the case ρ=1, where the arrays are ordered in accordance with b0+c1). Among two equivalent arrays (e.g., [2,1;3,6] and [6,3;1,2]), we include only the second one (so, the first cell of an equitable partition would have the minimal cardinality).

Columns:

Array.

The (hypothetical) intersection array.

Cardinality (|C|/|H|).

The cardinality of the (hypothetical) c.r. code divided by the number 2n of vertices in the n-cube (for given array, this ratio does not depend on n). Note that the cardinality of a c.r. code that corresponds to the reflected array is not shown in the table.

Spectrum.

The list [(n-θ1)/2, (n-θ2)/2, ..., (n-θρ)/2], where n=θ0, θ1, θ2, ..., θρ are the eigenvalues of the quotient matrix (for given intersection array, this list does not depend on n). So, the number λ in this list denotes the (1+λ)th largest eigenvalue of the hypercube.

Lower bound (LB).

The lower bound on the minimal dimension of a hypercube that contains a c.r. code with given intersection array. "!" means that the bound is non trivial (the trivial bound is maxi(bi+ci)). In the current version of the tables, almost all nontrivial bounds are given by the interweight-distribution condition. "99+" means that the array does not pass the interweight-distribution test test for n=100; it is naturally to conjecture that it does not pass this test for any n (a proof is wanted). In the case ρ=1, the correlation-immunity bound gives the same values (an empiric fact).

Upper bound (UB).

The upper bound on the minimal dimension of a hypercube that contains a c.r. code. I.e., the minimal dimension of an n-cube in which c.r. codes with given intersection array exist.

Reference.

An information about the construction that gives the upper bound, see the page Constructions. For some linear codes, the corresponding Cayley graph is mentioned /between slashes/. Sometimes, if no construction is known, we comment the structure of a hypothetical CR code, e.g., it must be nonlinear (when the code distance is less than 3; all linear c.r. codes are described in [Vas08]), or it must split another c.r. code with smaller covering radius.