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* FIXME: summarize [[http://trac.sagemath.org/sage_trac/ticket/6301|#6301]] | * Elementwise (Hadamard) product of matrices (Rob Beezer) (Trac [[http://trac.sagemath.org/sage_trac/ticket/6301|#6301]]) Given matrices A and B of the same size, {{{C = A.elementwise_product(B)}}} creates the new matrix C, of the same size, with entries given by C[i,j]=A[i,j]*B[i,j]. The multiplication occurs in a ring defined by Sage's coercion model, as appropriate for the base rings of A and B (or an error is raised if there is no sensible common ring). In particular, if A and B are defined over a noncommutative ring, then the operation is also noncommutative. The implementation is different for dense matrices versus sparse matrices, but there are probably further optimizations available for specific rings. This operation is often call the Hadamard product. {{{ sage: G = matrix(GF(3),2,[0,1,2,2]) sage: H = matrix(ZZ,2,[1,2,3,4]) sage: J = G.elementwise_product(H) sage: J [0 2] [0 2] sage: J.parent() Full MatrixSpace of 2 by 2 dense matrices over Finite Field of size }}} |
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* Compute the nil radical | |
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sage: H.nil_radical() a_1_0, a_1_1, a_2_4 |
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sage: H = CohomologyRing(128,562) | sage: H = CohomologyRing(128,562) # if there is internet connection, the ring data are downloaded behind the scenes |
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sage: H.nil_radical() a_1_0, a_1_1, a_2_1, a_2_2, a_3_2, a_4_1, a_5_2, a_5_3, b_2_0*b_4_2, a_7_5, b_2_0*b_6_3, b_6_3^2+b_4_2^3 |
Sage 4.1.1 Release Tour
Algebra
FIXME: summarize #6510
Basic Arithmetic
Calculus
FIXME: summarize #5996
Combinatorics
Cryptography
FIXME: summarize #6454
Documentation
FIXME: summarize #4460
Elliptic Curves
#6381 (bug in integral_points when rank is large):
The function integral_x_coords_in_interval() for finding all integral points on an elliptic curve defined over the rationals whose x-coordinate lies in an interval is now more efficient when the interval is large.
FIXME: summarize #6407
Graphics
Graph Theory
FIXME: summarize #6355
FIXME: summarize #6540
FIXME: summarize #6552
FIXME: summarize #6578
FIXME: summarize #5793
Interfaces
Linear Algebra
FIXME: summarize #5081
FIXME: summarize #6553
FIXME: summarize #6554
Elementwise (Hadamard) product of matrices (Rob Beezer) (Trac #6301)
Given matrices A and B of the same size, C = A.elementwise_product(B) creates the new matrix C, of the same size, with entries given by C[i,j]=A[i,j]*B[i,j]. The multiplication occurs in a ring defined by Sage's coercion model, as appropriate for the base rings of A and B (or an error is raised if there is no sensible common ring). In particular, if A and B are defined over a noncommutative ring, then the operation is also noncommutative. The implementation is different for dense matrices versus sparse matrices, but there are probably further optimizations available for specific rings. This operation is often call the Hadamard product.
sage: G = matrix(GF(3),2,[0,1,2,2]) sage: H = matrix(ZZ,2,[1,2,3,4]) sage: J = G.elementwise_product(H) sage: J [0 2] [0 2] sage: J.parent() Full MatrixSpace of 2 by 2 dense matrices over Finite Field of size
Modular Forms
Notebook
FIXME: summarize #5653
Number Theory
#6457 (Intersection of ideals in a number field)
Intersection of ideals in number fields is now implemented.
Numerical
Packages
FIXME: summarize #6558
FIXME: summarize #6380
FIXME: summarize #6443
FIXME: summarize #6445
FIXME: summarize #6451
FIXME: summarize #6453
FIXME: summarize #6528
FIXME: summarize #6143
FIXME: summarize #6438
FIXME: summarize #6493
FIXME: summarize #6563
FIXME: summarize #6602
FIXME: summarize #6302
new optional package p_group_cohomology (Simon A. King, David J. Green)
- Compute the cohomology ring with coefficients in GF(p) for any finite p-group, in terms of a minimal generating set and a minimal set of algebraic relations. We use Benson's criterion to prove the completeness of the ring structure.
- Compute depth, dimension, Poincare series and a-invariants of the cohomology rings.
- Compute the nil radical
- Construct induced homomorphisms.
- The package includes a list of cohomology rings for all groups of order 64.
- With the package, the cohomology for all groups of order 128 and for the Sylow 2-subgroup of the third Conway group (order 1024) was computed for the first time. The result of these and many other computations (e.g., all but 6 groups of order 243) is accessible in a repository on sage.math.
Examples:
- Data that are included with the package:
sage: from pGroupCohomology import CohomologyRing sage: H = CohomologyRing(64,132) # this is included in the package, hence, the ring structure is already there sage: print H Cohomology ring of Small Group number 132 of order 64 with coefficients in GF(2) Computation complete Minimal list of generators: [a_2_4, a 2-Cochain in H^*(SmallGroup(64,132); GF(2)), c_2_5, a 2-Cochain in H^*(SmallGroup(64,132); GF(2)), c_4_12, a 4-Cochain in H^*(SmallGroup(64,132); GF(2)), a_1_0, a 1-Cochain in H^*(SmallGroup(64,132); GF(2)), a_1_1, a 1-Cochain in H^*(SmallGroup(64,132); GF(2)), b_1_2, a 1-Cochain in H^*(SmallGroup(64,132); GF(2))] Minimal list of algebraic relations: [a_1_0*a_1_1, a_1_0*b_1_2, a_1_1^3+a_1_0^3, a_2_4*a_1_0, a_1_1^2*b_1_2^2+a_2_4*a_1_1*b_1_2+a_2_4^2+c_2_5*a_1_1^2] sage: H.depth() 2 sage: H.a_invariants() [-Infinity, -Infinity, -3, -3] sage: H.poincare_series() (-t^2 - t - 1)/(t^6 - 2*t^5 + t^4 - t^2 + 2*t - 1) sage: H.nil_radical() a_1_0, a_1_1, a_2_4
- Data from the repository on sage.math:
sage: H = CohomologyRing(128,562) # if there is internet connection, the ring data are downloaded behind the scenes sage: len(H.gens()) 35 sage: len(H.rels()) 486 sage: H.depth() 1 sage: H.a_invariants() [-Infinity, -4, -3, -3] sage: H.poincare_series() (t^14 - 2*t^13 + 2*t^12 - t^11 - t^10 + t^9 - 2*t^8 + 2*t^7 - 2*t^6 + 2*t^5 - 2*t^4 + t^3 - t^2 - 1)/(t^17 - 3*t^16 + 4*t^15 - 4*t^14 + 4*t^13 - 4*t^12 + 4*t^11 - 4*t^10 + 4*t^9 - 4*t^8 + 4*t^7 - 4*t^6 + 4*t^5 - 4*t^4 + 4*t^3 - 4*t^2 + 3*t - 1)
- Some computation from scratch, involving different ring presentations and induced maps:
sage: tmp_root = tmp_filename() sage: CohomologyRing.set_user_db(tmp_root) sage: H0 = CohomologyRing.user_db(8,3,websource=False) sage: print H0 Cohomology ring of Dihedral group of order 8 with coefficients in GF(2) Computed up to degree 0 Minimal list of generators: [] Minimal list of algebraic relations: [] sage: H0.make() sage: print H0 Cohomology ring of Dihedral group of order 8 with coefficients in GF(2) Computation complete Minimal list of generators: [c_2_2, a 2-Cochain in H^*(D8; GF(2)), b_1_0, a 1-Cochain in H^*(D8; GF(2)), b_1_1, a 1-Cochain in H^*(D8; GF(2))] Minimal list of algebraic relations: [b_1_0*b_1_1] sage: G = gap('DihedralGroup(8)') sage: H1 = CohomologyRing.user_db(G,GroupName='GapD8',websource=False) sage: H1.make() sage: print H1 # the ring presentation is different ... Cohomology ring of GapD8 with coefficients in GF(2) Computation complete Minimal list of generators: [c_2_2, a 2-Cochain in H^*(GapD8; GF(2)), b_1_0, a 1-Cochain in H^*(GapD8; GF(2)), b_1_1, a 1-Cochain in H^*(GapD8; GF(2))] Minimal list of algebraic relations: [b_1_1^2+b_1_0*b_1_1] sage: phi = G.IsomorphismGroups(H0.group()) sage: phi_star = H0.hom(phi,H1) sage: phi_star_inv = phi_star^(-1) # ... but the rings are isomorphic sage: [X==phi_star_inv(phi_star(X)) for X in H0.gens()] [True, True, True, True] sage: [X==phi_star(phi_star_inv(X)) for X in H1.gens()] [True, True, True, True]
- An example with an odd prime:
sage: H = CohomologyRing(81,8) # this needs to be computed from scratch sage: H.make() sage: H.gens() [1, a_2_1, a 2-Cochain in H^*(SmallGroup(81,8); GF(3)), a_2_2, a 2-Cochain in H^*(SmallGroup(81,8); GF(3)), b_2_0, a 2-Cochain in H^*(SmallGroup(81,8); GF(3)), a_4_1, a 4-Cochain in H^*(SmallGroup(81,8); GF(3)), b_4_2, a 4-Cochain in H^*(SmallGroup(81,8); GF(3)), b_6_3, a 6-Cochain in H^*(SmallGroup(81,8); GF(3)), c_6_4, a 6-Cochain in H^*(SmallGroup(81,8); GF(3)), a_1_0, a 1-Cochain in H^*(SmallGroup(81,8); GF(3)), a_1_1, a 1-Cochain in H^*(SmallGroup(81,8); GF(3)), a_3_2, a 3-Cochain in H^*(SmallGroup(81,8); GF(3)), a_5_2, a 5-Cochain in H^*(SmallGroup(81,8); GF(3)), a_5_3, a 5-Cochain in H^*(SmallGroup(81,8); GF(3)), a_7_5, a 7-Cochain in H^*(SmallGroup(81,8); GF(3))] sage: len(H.rels()) 59 sage: H.depth() 1 sage: H.a_invariants() [-Infinity, -3, -2] sage: H.poincare_series() (t^4 - t^3 + t^2 + 1)/(t^6 - 2*t^5 + 2*t^4 - 2*t^3 + 2*t^2 - 2*t + 1) sage: H.nil_radical() a_1_0, a_1_1, a_2_1, a_2_2, a_3_2, a_4_1, a_5_2, a_5_3, b_2_0*b_4_2, a_7_5, b_2_0*b_6_3, b_6_3^2+b_4_2^3