(0) Obligation:

Q restricted rewrite system:
The TRS R consists of the following rules:

f(a, X) → f(X, X)
ca
cb

Q is empty.

(1) DependencyPairsProof (EQUIVALENT transformation)

Using Dependency Pairs [AG00,LPAR04] we result in the following initial DP problem.

(2) Obligation:

Q DP problem:
The TRS P consists of the following rules:

F(a, X) → F(X, X)

The TRS R consists of the following rules:

f(a, X) → f(X, X)
ca
cb

Q is empty.
We have to consider all minimal (P,Q,R)-chains.

(3) NonLoopProof (EQUIVALENT transformation)

By Theorem 8 [NONLOOP] we deduce infiniteness of the QDP.
We apply the theorem with m = 1, b = 0,
σ' = [ ], and μ' = [ ] on the rule
F(a, a)[ ]n[x0 / a] → F(a, a)[ ]n[x0 / a]
This rule is correct for the QDP as the following derivation shows:

intermediate steps: Equivalent (Simplify mu) - Instantiate mu - Instantiation
F(a, X)[ ]n[ ] → F(X, X)[ ]n[ ]
    by OriginalRule from TRS P

(4) NO