Fixing a set ϵ of generators of the fundamental group of the surface class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0022404916000402&_mathId=si137.gif&_user=111111111&_pii=S0022404916000402&_rdoc=1&_issn=00224049&md5=478039d847b49812d7838fdf6ea2932e" title="Click to view the MathML source">π1(S)class="mathContainer hidden">class="mathCode">, we associate to any cut d a weight class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0022404916000402&_mathId=si3.gif&_user=111111111&_pii=S0022404916000402&_rdoc=1&_issn=00224049&md5=67d470baec590bdb87d0ae1a2d255c51" title="Click to view the MathML source">wϵ(d)∈Z2g+bclass="mathContainer hidden">class="mathCode">, where g is the genus of S and b the number of boundary components. The main result of the paper asserts that the derived equivalence class of the surface algebra is determined by the corresponding weight class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0022404916000402&_mathId=si4.gif&_user=111111111&_pii=S0022404916000402&_rdoc=1&_issn=00224049&md5=df8da857ce929544d9135b26e20995d0" title="Click to view the MathML source">wϵ(d)class="mathContainer hidden">class="mathCode"> up to homeomorphism of the surface. Surface algebras are gentle and of global dimension ≤2, and any surface algebras coming from the same surface class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0022404916000402&_mathId=si17.gif&_user=111111111&_pii=S0022404916000402&_rdoc=1&_issn=00224049&md5=52407c415661c027bd3107f34aeaa81d" title="Click to view the MathML source">(S,M)class="mathContainer hidden">class="mathCode"> are cluster equivalent, in the sense of [2]. To prove that the weight is a derived invariant we strongly use results about cluster equivalent algebras from [2].
Furthermore we also show that for surface algebras the invariant defined for gentle algebras by Avella-Alaminos and Geiss in [6] is determined by the weight.