The paper studies definable valuations in ordered fields. The main result is that any henselian valuation definable in the language of ordered rings is already definable in the language of rings. As shown in Example 3.5 and Example 3.6 this need not be the true if the henselianity assumption is dropped.
A key result in the proof is (Theorem 4.2) that in ordered henseilan fields (in the language of ordered valued fields) the value group and the residue field are orthogonal and both are stably embedded. Combined with the theory of h-minimality this implies (Proposition 4.5) that any two valuations definable (in the languauge of ordered rings) are comparable provided one of them is henselian.
One application of these results is that if \(K\) is almost real closed (i.e., \(K\) admits some henselian valuation with real closed residue field) then any valuation on \(K\) definable in the langugae of rings is henselian.