Description
Let $\{g_1,g_2,\ldots,g_r\}$ be a graded basis of
F with $deg(g_i)=f_i,\ i=1,\ldots,r.$ A monomial submodule $M=\oplus_{i=1}^{r}{I_ig_i}$ of
F is stable if it is almost stable and $(x_1,\ldots,x_n)^{(f_{i+1}-f_i)} I_{i+1}$ belongs to $I_i$ for $i=1,\ldots,r-1.$ A monomial ideal $I$ of $E$ is called stable if for each monomial $e_{\sigma}\in I$ and each $j < \mathrm{m}(e_{\sigma})$ one has $e_j e_{{\sigma} \setminus \{\mathrm{m}(e_{\sigma})\}} \in I.$
Example:
i1 : E = QQ[e_1..e_4, SkewCommutative => true]
o1 = E
o1 : PolynomialRing, 4 skew commutative variable(s)
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i2 : F=E^{0,0}
2
o2 = E
o2 : E-module, free
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i3 : I_1=ideal(e_1*e_2)
o3 = ideal(e e )
1 2
o3 : Ideal of E
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i4 : I_2=ideal(e_1*e_2*e_3,e_1*e_2*e_4,e_1*e_3*e_4)
o4 = ideal (e e e , e e e , e e e )
1 2 3 1 2 4 1 3 4
o4 : Ideal of E
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i5 : M=createModule({I_1,I_2},F)
o5 = image | e_1e_2 0 0 0 |
| 0 e_1e_3e_4 e_1e_2e_4 e_1e_2e_3 |
2
o5 : E-module, submodule of E
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i6 : isAlmostStableModule M
o6 = true
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i7 : isStableModule M
o7 = false
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