The canonical representation carried by a string word #
The basis vectors of a string representation are the occurrences of vertices along the word. We represent an occurrence by the prefix ending there. This retains repeated visits to the same displayed vertex without choosing numeric coordinates.
A displayed arrow acts between two prefix occurrences when the word traverses that arrow positively between them, or traverses its formal inverse in the opposite direction. Reduction makes the resulting target occurrence unique.
A positive signed arrow can never equal a negative signed arrow with the same signed endpoints.
An occurrence of x along a word, represented by the prefix ending at
that occurrence.
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The length of the prefix representing a position.
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The prefix length of a position is at most the word length.
A position at the final word index lies at the target vertex.
Two prefix positions at the same vertex with the same index coincide.
Prefix length embeds the positions at a fixed displayed vertex into the finite interval of word indices.
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A position anywhere along a word, retaining the displayed vertex over which it lies.
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The prefix index of a total word position.
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The prefix index determines a total position, including its displayed vertex.
Prefix index embeds all positions of a word into its finite index interval.
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The position at the source endpoint of a string word.
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The position at the target endpoint of a string word.
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Every index between zero and the word length is represented by a total word position.
Total word positions are canonically indexed by the finite interval from zero through the word length.
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The vertex space of the canonical string representation.
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A positive occurrence of a moves a basis position one step forward;
an inverse occurrence moves it one step backward.
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An arrow step changes the prefix index by one, forward or backward.
Two total positions at consecutive indices are joined by the displayed ordinary arrow, oriented according to the intervening signed letter.
A position before the final index has an adjacent next position and a displayed arrow in one of the two ordinary orientations.
A position after the initial index has an adjacent previous position and a displayed arrow in one of the two ordinary orientations.
A fixed pair of adjacent word positions determines the displayed arrow between them.
Two displayed-arrow steps cannot traverse the same word edge in opposite displayed directions.
A string word has at most one target position for a displayed arrow from a fixed source position.
The image of one position-basis vector under a displayed arrow.
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At a witnessed arrow step, the corresponding basis vector is sent to the basis vector at that target position.
If an arrow has no target occurrence from a basis position, that basis vector is killed.
The linear map assigned to a displayed arrow by the canonical string representation.
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Reachability of one word-position basis vector under an ordinary quiver path. Each arrow is allowed to use either its positive occurrence or the matching inverse occurrence in the word.
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A nonempty positive traversal cannot be followed by a backward arrow step: their final signed arrows would have opposite signs.
A nonempty backward traversal cannot be followed by a forward arrow step. Reversing the two competing suffixes reduces this to the preceding positive-versus-negative final-arrow contradiction.
A reachable ordinary path moves monotonically along the word: it is realized either by the positive copy of the whole path or by the reversed positive copy in the opposite direction.
A reachable path occurs as one contiguous positive segment of the word or of its reverse.
Every ordinary path which acts nontrivially on a position basis survives the string-algebra relation quotient.
Reduction makes the endpoint of a reachable path unique.
The image of a position-basis vector under a quiver path, expressed as the unique reachable basis vector when it exists.
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The canonical quiver representation of a string word before descending through the relation quotient.
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Evaluation of the canonical representation with the original displayed vertices pinned explicitly.
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Applying one more displayed arrow to the path image of a basis position agrees with extending position reachability by that arrow.
Evaluation of an ordinary quiver path on a position-basis vector is the unique reachable basis vector, or zero when no such position exists.
Every ordinary path killed by the relation quotient acts as zero on the canonical string representation.
The reversed linear realization of the canonical quiver representation as a right module over the free linear path category.
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Reversed path evaluation agrees with the opposite of evaluation in the canonical quiver representation.
On a path-basis morphism, the free right-module realization is the opposite of the corresponding quiver-representation map.
For a monomial presentation, the free realization of a string word kills the complete generated relation ideal.
The string-word realization descended through a monomial relation quotient, still written covariantly with values in the opposite module category.
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The canonical finite-dimensional right module represented by a string word.
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The descended right module evaluates a quotient path by the canonical position-basis path map.