SimpleSummandsOfSecondRadicalLayer

The simple summands of J^2/J^3 for the Jacobson radical J of the path's linear Nakayama algebra, one for each indecomposable projective of dimension at least three.

✓ checked against that system · ! checked, with disagreements (hover a chip)FindStatSt001480via DyckPath✓↗

SimpleSummandsOfSecondRadicalLayer(path)The simple summands of J^2/J^3 for the Jacobson radical J of the path's linear Nakayama algebra, one for each indecomposable projective of dimension at least three.

Typed signatures

Type	Package	Applies
(dyck_path) -> number	combinatorics	always

Domain: Dyck path statistics

Details

• Defined over DyckPath as an expression in _x, evaluated by compute-engine — the definition IS the implementation.
• Takes a DyckPath and nothing else — it reads values against their positions, or walks the orbits, so it needs the bijection. Applying it to a bare list is a type error, not a wrong answer.

Definition

Epsil, as the implementation runs it.

on DyckPath, over _x

0 if Length(_x) < 1 else Apply(
                                (series: list<integer>) => Count(Filter(
                                                                         series,
                                                                         Function(d >= 3, d),
                                                                       )),
                                Apply(
                                       (h: list<integer>) => Apply(
                                                                    (ups: list<integer>) => Join(Map(
                                                                                                      Function(h[ups[Length(_x) / 2 +
                                                                                                                     1 -
                                                                                                                     t]] +
                                                                                                               1, t),
                                                                                                      Range(1, Length(_x) / 2),
                                                                                                    ), [1]),
                                                                    Filter(
                                                                            Range(1, Length(_x)),
                                                                            Function(_x[i] == 1, i),
                                                                          ),
                                                                  ),
                                       Map(
                                            Function(Sum(Map(
                                                              Function(
                                                                        2 *
                                                                        _x[k] - 1,
                                                                        k,
                                                                      ),
                                                              Range(1, i),
                                                            )), i),
                                            Range(1, Length(_x)),
                                          ),
                                     ),
                              )

Examples

Basic #

the step word $UUDDUD$

live ↗

In$\mathrm{SimpleSummandsOfSecondRadicalLayer}({\operatorname{DyckPath}}([1, 1, 0, 0, 1, 0]))$Out$1$

the step word $UDUUDD$

live ↗

In$\mathrm{SimpleSummandsOfSecondRadicalLayer}({\operatorname{DyckPath}}([1, 0, 1, 1, 0, 0]))$Out$1$

Properties #

FindStat's value for [1,0,1,0]

live ↗

In$\mathrm{CombinatorialStat}({\operatorname{DyckPath}}([1, 0, 1, 0]), \text{SimpleSummandsOfSecondRadicalLayer})$Out$0$

Known value · FindStat St001480

FindStat's value for [1,1,0,0]

live ↗

In$\mathrm{CombinatorialStat}({\operatorname{DyckPath}}([1, 1, 0, 0]), \text{SimpleSummandsOfSecondRadicalLayer})$Out$1$

Known value · FindStat St001480

FindStat's value for [1,0,1,0,1,0]

live ↗

In$\mathrm{CombinatorialStat}({\operatorname{DyckPath}}([1, 0, 1, 0, 1, 0]), \text{SimpleSummandsOfSecondRadicalLayer})$Out$0$

Known value · FindStat St001480

About

Examples	5
Crosswalk	FindStat