Opened 7 years ago
Closed 7 years ago
#18469 closed defect (fixed)
Tensor product of crystals does not handle -inf for epsilon/phi correctly
Reported by: | tscrim | Owned by: | sage-combinat |
---|---|---|---|
Priority: | major | Milestone: | sage-6.8 |
Component: | combinatorics | Keywords: | crystals, tensor product |
Cc: | sage-combinat, bsalisbury1, aschilling | Merged in: | |
Authors: | Travis Scrimshaw | Reviewers: | Ben Salisbury |
Report Upstream: | N/A | Work issues: | |
Branch: | 9a24ea0 (Commits, GitHub, GitLab) | Commit: | 9a24ea03c2a5a4268224cc34230681bbb8b92190 |
Dependencies: | Stopgaps: |
Description
This does not work:
sage: E1 = crystals.elementary.B(['A',2], 1) sage: E2 = crystals.elementary.B(['A',2], 2) sage: T = crystals.TensorProduct(E1, E2) sage: x = T(E1.module_generators[0], E2.module_generators[0]); x [0, 0] sage: x.f(1) [-1, 0] sage: x.e(1) [1, 0]
The reason is because we try and be clever with how we compute the _sig
and do an epsilon_(k) - phi_i(k-1)
. If one of these (in particular, the phi) is -inf
, then the computation breaks down. Instead, we have to bite the bullet and do the partial sums of the weight pairings to make sure we cover these cases.
Change History (4)
comment:1 Changed 7 years ago by
- Branch set to public/crystals/fix_tensor_product-18469
- Commit set to 211f6116ff935d05994f64801950715eea591922
- Status changed from new to needs_review
comment:2 Changed 7 years ago by
- Commit changed from 211f6116ff935d05994f64801950715eea591922 to 9a24ea03c2a5a4268224cc34230681bbb8b92190
Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:
9a24ea0 | Fixing _sig for epsilon/phi returning -inf.
|
comment:3 Changed 7 years ago by
- Reviewers set to Ben Salisbury
- Status changed from needs_review to positive_review
Thanks, Travis.
comment:4 Changed 7 years ago by
- Branch changed from public/crystals/fix_tensor_product-18469 to 9a24ea03c2a5a4268224cc34230681bbb8b92190
- Resolution set to fixed
- Status changed from positive_review to closed
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New commits:
Fixing _sig for epsilon/phi returning -inf.