Loop Crystals

sage.categories.loop_crystals.KirillovReshetikhinCrystals

Category of Kirillov-Reshetikhin crystals.

class sage.categories.loop_crystals.LocalEnergyFunction(B, Bp, normalization=0)

Bases: sage.categories.map.Map

The local energy function.

Let \(B\) and \(B'\) be Kirillov-Reshetikhin crystals with maximal vectors \(u_B\) and \(u_{B'}\) respectively. The local energy function \(H : B \otimes B' \to \ZZ\) is the function which satisfies

\[\begin{split}H(e_0(b \otimes b')) = H(b \otimes b') + \begin{cases} 1 & \text{if } i = 0 \text{ and LL}, \\ -1 & \text{if } i = 0 \text{ and RR}, \\ 0 & \text{otherwise,} \end{cases}\end{split}\]

where LL (resp. RR) denote \(e_0\) acts on the left (resp. right) on both \(b \otimes b'\) and \(R(b \otimes b')\), and normalized by \(H(u_B \otimes u_{B'}) = 0\).

INPUT:

  • B – a Kirillov-Reshetikhin crystal
  • Bp – a Kirillov-Reshetikhin crystal
  • normalization – (default: 0) the normalization value

EXAMPLES:

sage: K = crystals.KirillovReshetikhin(['C',2,1], 1,2)
sage: K2 = crystals.KirillovReshetikhin(['C',2,1], 2,1)
sage: H = K.local_energy_function(K2)
sage: T = tensor([K, K2])
sage: hw = T.classically_highest_weight_vectors()
sage: for b in hw:
....:     b, H(b)
([[], [[1], [2]]], 1)
([[[1, 1]], [[1], [2]]], 0)
([[[2, -2]], [[1], [2]]], 1)
([[[1, -2]], [[1], [2]]], 1)

REFERENCES:

[KKMMNN1992]

sage.categories.loop_crystals.LoopCrystals

The category of \(U_q'(\mathfrak{g})\)-crystals, where \(\mathfrak{g}\) is of affine type.

The category is called loop crystals as we can also consider them as crystals corresponding to the loop algebra \(\mathfrak{g}_0[t]\), where \(\mathfrak{g}_0\) is the corresponding classical type.

EXAMPLES:

sage: from sage.categories.loop_crystals import LoopCrystals
sage: C = LoopCrystals()
sage: C
Category of loop crystals
sage: C.super_categories()
[Category of crystals]
sage: C.example()
Kirillov-Reshetikhin crystal of type ['A', 3, 1] with (r,s)=(1,1)
sage.categories.loop_crystals.RegularLoopCrystals

The category of regular \(U_q'(\mathfrak{g})\)-crystals, where \(\mathfrak{g}\) is of affine type.