YES Problem: a(a(x1)) -> b(b(b(x1))) b(b(x1)) -> c(c(c(x1))) c(c(x1)) -> d(d(d(x1))) b(x1) -> d(d(x1)) c(d(d(x1))) -> a(x1) Proof: Arctic Interpretation Processor: dimension: 1 interpretation: [d](x0) = 4x0, [c](x0) = 6x0, [b](x0) = 9x0, [a](x0) = 14x0 orientation: a(a(x1)) = 28x1 >= 27x1 = b(b(b(x1))) b(b(x1)) = 18x1 >= 18x1 = c(c(c(x1))) c(c(x1)) = 12x1 >= 12x1 = d(d(d(x1))) b(x1) = 9x1 >= 8x1 = d(d(x1)) c(d(d(x1))) = 14x1 >= 14x1 = a(x1) problem: b(b(x1)) -> c(c(c(x1))) c(c(x1)) -> d(d(d(x1))) c(d(d(x1))) -> a(x1) Arctic Interpretation Processor: dimension: 2 interpretation: [0 0] [d](x0) = [1 0]x0, [2 0] [c](x0) = [2 2]x0, [0 3] [b](x0) = [3 3]x0, [0 -&] [a](x0) = [0 0 ]x0 orientation: [6 6] [6 4] b(b(x1)) = [6 6]x1 >= [6 6]x1 = c(c(c(x1))) [4 2] [1 1] c(c(x1)) = [4 4]x1 >= [2 1]x1 = d(d(d(x1))) [3 2] [0 -&] c(d(d(x1))) = [3 3]x1 >= [0 0 ]x1 = a(x1) problem: b(b(x1)) -> c(c(c(x1))) Arctic Interpretation Processor: dimension: 3 interpretation: [0 -& 0 ] [c](x0) = [-& -& 0 ]x0 [0 0 0 ] , [0 1 0 ] [b](x0) = [1 0 1 ]x0 [1 1 -&] orientation: [2 1 2] [0 0 0] b(b(x1)) = [2 2 1]x1 >= [0 0 0]x1 = c(c(c(x1))) [2 2 2] [0 0 0] problem: Qed