Rank of various constructions #
Main statements #
rank_quotient_add_rank_le:rank M/N + rank N ≤ rank M.lift_rank_add_lift_rank_le_rank_prod:rank M × N ≤ rank M + rank N.rank_span_le_of_finite:rank (span s) ≤ #sfor finites.
For free modules, we have
rank_prod:rank M × N = rank M + rank N.rank_finsupp:rank (ι →₀ M) = #ι * rank Mrank_directSum:rank (⨁ Mᵢ) = ∑ rank Mᵢrank_tensorProduct:rank (M ⊗ N) = rank M * rank N.
Lemmas for ranks of submodules and subalgebras are also provided.
We have finrank variants for most lemmas as well.
The dimension of a quotient is bounded by the dimension of the ambient space.
If M and M' are free, then the rank of M × M' is
(Module.rank R M).lift + (Module.rank R M').lift.
If M and M' are free (and lie in the same universe), the rank of M × M' is
(Module.rank R M) + (Module.rank R M').
The finrank of M × M' is (finrank R M) + (finrank R M').
The rank of (ι →₀ R) is (#ι).lift.
If R and ι lie in the same universe, the rank of (ι →₀ R) is # ι.
The rank of the direct sum is the sum of the ranks.
If m and n are finite, the rank of m × n matrices over a module M is
(#m).lift * (#n).lift * rank R M.
If m and n are finite and lie in the same universe, the rank of m × n matrices over a
module M is (#m * #n).lift * rank R M.
If m and n are finite, the rank of m × n matrices is (#m).lift * (#n).lift.
If m and n are finite and lie in the same universe, the rank of m × n matrices is
(#n * #m).lift.
If m and n are finite and lie in the same universe as R, the rank of m × n matrices
is # m * # n.
The finrank of (ι →₀ R) is Fintype.card ι.
If m and n are Fintype, the finrank of m × n matrices over a module M is
(Fintype.card m) * (Fintype.card n) * finrank R M.
The rank of a finite product of free modules is the sum of the ranks.
The finrank of (ι → R) is Fintype.card ι.
The vector space of functions on a Fintype ι has finrank equal to the cardinality of ι.
An n-dimensional R-vector space is equivalent to Fin n → R.
Equations
Instances For
The S-rank of M ⊗[R] M' is (Module.rank S M).lift * (Module.rank R M').lift.
If M and M' lie in the same universe, the S-rank of M ⊗[R] M' is
(Module.rank S M) * (Module.rank R M').
The S-finrank of M ⊗[R] M' is (finrank S M) * (finrank R M').
The dimension of a submodule is bounded by the dimension of the ambient space.
Pushforwards of finite submodules have a smaller finrank.
The rank of a set of vectors as a natural number.
Equations
- Set.finrank R s = Module.finrank R ↥(Submodule.span R s)