Proposition 2.6(3): k(Γ_A) is the radical grading of ind(mod A) #
graded-category.tex. Sending each arrow to its chosen class in
C_1 = Irr defines a functor from the path category; it kills each mesh
relation, because the degree-two part of p ∘ i = 0 is the image of r_Y;
the resulting graded functor k(Γ_A) → gr_J ind(mod A) is surjective because
the radical layers are generated in degree one, and injective by induction on
the degree, using the exactness of Proposition 2.6(1).
Formally, choose for each arrow a : x → y a representative rep a ∈ J(x, y)
of the chosen basis vector of Irr(x, y). A path is realized by the composite
of the representatives (pathMap), and a morphism of kQ by linear extension
(realize). A path of length d lands in J^d, so a homogeneous morphism of
degree d has a class in the radical layer J^d/J^{d+1}.
A representative in J(x, y) of the basis vector of Irr(x, y) indexed by
the arrow a.
Instances For
The realization of a path: the composite of the representatives of its arrows.
Instances For
The realization of a morphism of kQ, by linear extension.
Instances For
In Irr(x, y), every vector is a multiple of the basis vector of the
(unique) arrow.
A radical map agrees modulo J² with the corresponding multiple of the
representative of the arrow.
The components of the canonical mesh at a nonprojective vertex compose to
zero: ∑_i α_i β_i = 0.
Agreement modulo J² of two radical factors gives agreement modulo J³
of their composites.
The component τx → y at an occurrence, in ind(mod A).
Instances For
The component y → x at an occurrence, in ind(mod A).
Instances For
One occurrence contributes u_i v_i (σ a) a modulo J³.
The sum of the occurrence composites at a vertex vanishes.
The number of arrows y → x equals the number of occurrences of y in
the mesh ending at x.
The mesh relations are realized in J³: the degree-two part of
p ∘ i = 0 is the image of r_x.
The degree-d component of an element of the mesh ideal is realized in
J^{d+1}.
Maps between distinct (hence nonisomorphic) indecomposables are radical.
An endomorphism of an indecomposable is a scalar plus a radical map.
Surjectivity in Proposition 2.6(3): the radical layers are generated in
degree one. Every f ∈ J^d agrees modulo J^{d+1} with the realization of a
homogeneous morphism of degree d of the path category.
dim Irr(x, y) is the number of occurrences of x in the middle term of the
mesh ending at y.
The arrow E_i → Y given by a summand i of the middle term of the mesh
ending at Y.
Instances For
The summands of the middle term at Y correspond bijectively to the arrows
ending at Y.
Instances For
The component β_i of the right almost split map, in ind(mod A).
Instances For
The coordinate v_i of β_i in the arrow basis; it is nonzero.
Instances For
The component α_i : τY → E_i of the first map, in ind(mod A).
Instances For
The coordinate u_i of α_i in the arrow basis.
Instances For
The mesh coefficient of the arrow of the summand i is u_i v_i.
At a projective vertex the first term of the mesh is zero.
The mesh ideal of k(Γ_A) in the linear path category.
Instances For
The identity of an indecomposable is not radical.
Reindexing the last-arrow decomposition by the summands of the mesh.
The estimate ∑_i v_i⁻¹ G_i β_i ∈ J^{N+2} used in the injectivity step.
The corrected component G_i - c_i H (σ a_i) is realized in J^{m+2}.
Injectivity in Proposition 2.6(3): a homogeneous morphism of degree N
of the path category whose realization lies in J^{N+1} belongs to the mesh
ideal.