Opened 13 years ago

Closed 13 years ago

# identical rows of syzygies over the Weyl algebra

Reported by: Owned by: barakat@… somebody minor 3-1-3 and higher dontKnow 3-1-2

### Description

the syz command for the Weyl algebra produces a highly redundant matrix with many *identical* columns of syzygies

LIB "nctools.lib"; ring A=0,(z,x,y,dz,dx,dy),dp; def S=Weyl(); setring S; matrix m[1][6] = x2*y8+2*x*y9+y10+2*x5*y4+2*x4*y5+x8,-z*x*y8-z*y9-5*z*x4*y4-4*z*x3*y5-4*z*x7,z2*y8+8*z2*x3*y4+z*y8+16*z2*x6-4*z*x3*y4-12*z*x2*y5+4*z*x6,4*z2*x*y7+5*z2*y8+16*z2*x4*y3+20*z2*x3*y4+z*y8+12*z*x4*y3+20*z*x3*y4,-4*z*x2*y7-9*z*x*y8-5*z*y9-4*z*x5*y3-5*z*x4*y4,16*z2*x2*y6+40*z2*x*y7+25*z2*y8+4*z*x2*y6+8*z*x*y7+5*z*y8-12*z*x5*y2-20*z*x4*y3; matrix s=syz(m); s[3]==s[2]; s[3]==s[4]; s[3]==s[5]; s[3]==s[6]; s[3]==s[7]; s[3]==s[8];

### comment:1 Changed 13 years ago by hannes

Resolution: → fixed new → closed

In principle: this is correct, but not good: it shows that we need more/better criteria for the PLURAL case. fixed with the help of idDelMultiples

### comment:2 Changed 13 years ago by levandov

Can't look at the code at the moment, but one has to make sure that what one deletes is a left multiple of what remains; per default we work with left modules... Regards, Viktor

### comment:3 Changed 13 years ago by hannes

idDelMultiples deletes polys which differ by a factor in the ground field.

Note: See TracTickets for help on using tickets.