R:= RootSystem( "D",5); U:=QuantizedUEA(R); g:= GeneratorsOfAlgebra( U ); PositiveRoots(R); PositiveRootsInConvexOrder(R); ########## generators of U ############### f1:=g[1]; f2:=g[3]; f3:=g[6]; f4:=g[10]; f5:=g[20]; e1:=g[31]; e2:=g[33]; e3:=g[36]; e4:=g[40]; e5:=g[50]; k1:=g[21]; k2:=g[23]; k3:=g[25]; k4:=g[27]; k5:=g[29]; k1m:=g[22]; k2m:=g[24]; k3m:=g[26]; k4m:=g[28]; k5m:=g[30]; ########## generators of B ############### b1:=f1 - k1m * e1; b2:=f2 - k2m * e2; b3:=f3 - k3m * e3; b4:=f4 - k4m * e5; b5:=f5 - k5m * e4; a4:= k4 * k5m; a5:= k5 * k4m; ########## q-numbers #################### 2q:=_q+_q^-1; ########## q-commutator ################# qcom2:=function(a,b) return a*b-_q*b*a; end; ######### relations in B as a function ######### rel1:=function(a,b) return a^2*b - (_q + _q^-1)*a*b*a + b*a^2 ; end; ################# relations #################### (_q-_q^-1)*(b4 * b5 - b5 * b4) - a4 + a5; rel1(b2,b3) + _q^-1*b3; rel1(b3,b2) + _q^-1*b2; rel1(b4,b3); rel1(b3,b4) + _q^-1 * b4; b2*b4-b4*b2; b2*b5-b5*b2; rel1(b5,b3); rel1(b3,b5) + _q^-1 * b5; ################# \tau_2^{-1} Braid group action ##################### t2mb1:=qcom2(b2,b1);; t2mb2:=b2;; t2mb3:=qcom2(b2,b3);; t2mb4:=b4;; t2mb5:=b5;; t2ma4:=a4;; t2ma5:=a5;; ################# t2m is an algebra homomorphism ############ (_q-_q^-1)* (t2mb4 * t2mb5 - t2mb5 * t2mb4) - t2ma4 + t2ma5; rel1(t2mb2,t2mb3) + _q^-1 * t2mb3; rel1(t2mb3,t2mb2) + _q^-1 * t2mb2; rel1(t2mb4,t2mb3); rel1(t2mb3,t2mb4) + _q^-1 * t2mb4; t2mb2*t2mb4 - t2mb4*t2mb2; t2mb2*t2mb5 - t2mb5*t2mb2; rel1(t2mb5,t2mb3); rel1(t2mb3,t2mb5) + _q^-1 * t2mb5; ################# the inverse \tau_2 of \tau_2^{-1} ##################### t2b1:=qcom2(b1,b2);; t2b2:=b2;; t2b3:=qcom2(b3,b2);; t2b4:=b4;; t2b5:=b5;; t2a4:=a4;; t2a5:=a5;; ################# t2 is an algebra homomorphism ############ (_q-_q^-1)* (t2b4 * t2b5 - t2b5 * t2b4) - t2a4 + t2a5; rel1(t2b2,t2b3) + _q^-1 * t2b3; rel1(t2b3,t2b2) + _q^-1 * t2b2; rel1(t2b4,t2b3); rel1(t2b3,t2b4) + _q^-1 * t2b4; t2b2*t2b4 - t2b4*t2b2; t2b2*t2b5 - t2b5*t2b2; rel1(t2b5,t2b3); rel1(t2b3,t2b5) + _q^-1 * t2b5; ################ t2m is the inverse of t2 ###################### qcom2(t2b2,t2b1) - b1; qcom2(t2b2,t2b3) - b3; qcom2(t2mb1,t2mb2) - b1; qcom2(t2mb3,t2mb2) - b3; ################# \tau_3^{-1} Braid group action ##################### t3mb1:=b1;; t3mb2:=qcom2(b3,b2);; t3mb3:=b3;; t3mb4:=qcom2(b3,b4);; t3mb5:=qcom2(b3,b5);; t3ma4:=a4;; t3ma5:=a5;; ################# t3m is an algebra homomorphism ############ (_q-_q^-1)* (t3mb4 * t3mb5 - t3mb5 * t3mb4) - t3ma4 + t3ma5; rel1(t3mb2,t3mb3) + _q^-1 * t3mb3; rel1(t3mb3,t3mb2) + _q^-1 * t3mb2; rel1(t3mb4,t3mb3); rel1(t3mb3,t3mb4) + _q^-1 * t3mb4; t3mb2*t3mb4 - t3mb4*t3mb2; t3mb2*t3mb5 - t3mb5*t3mb2; rel1(t3mb5,t3mb3); rel1(t3mb3,t3mb5) + _q^-1 * t3mb5; ################# the inverse \tau_3 of \tau_3^{-1} ################## t3b1:=b1;; t3b2:=qcom2(b2,b3);; t3b3:=b3;; t3b4:=qcom2(b4,b3);; t3b5:=qcom2(b5,b3);; t3a4:=a4;; t3a5:=a5;; ################# t3 is an algebra homomorphism ############ (_q-_q^-1)* (t3b4 * t3b5 - t3b5 * t3b4) - t3a4 + t3a5; rel1(t3b2,t3b3) + _q^-1 * t3b3; rel1(t3b3,t3b2) + _q^-1 * t3b2; rel1(t3b4,t3b3); rel1(t3b3,t3b4) + _q^-1 * t3b4; t3b2*t3b4 - t3b4*t3b2; t3b2*t3b5 - t3b5*t3b2; rel1(t3b5,t3b3); rel1(t3b3,t3b5) + _q^-1 * t3b5; ############# t3m is the inverse of t3 ######################## qcom2(t3mb2,t3mb3) -b2; qcom2(t3mb4,t3mb3) -b4; qcom2(t3mb5,t3mb3) -b5; qcom2(t3b3,t3b2) - b2; qcom2(t3b3,t3b4) - b4; qcom2(t3b3,t3b5) - b5; ############## \tau_4^{-1} Braid group action ##################### t4mb1:=b1;; t4mb2:=b2;; t4mb3:= _q^-1 * qcom2(b4,qcom2(b5,b3))+b3*a4;; t4mb4:= _q^-1 * a4* b5;; t4mb5:= _q^-1 * a5 * b4;; t4ma4:= a5;; t4ma5:= a4;; ############ t4m is an algebra homomorphism ############# (_q-_q^-1)* (t4mb4 * t4mb5 - t4mb5 * t4mb4) - t4ma4 + t4ma5; rel1(t4mb2,t4mb3) + _q^-1 * t4mb3; rel1(t4mb3,t4mb2) + _q^-1 * t4mb2; rel1(t4mb4,t4mb3); rel1(t4mb3,t4mb4) + _q^-1 * t4mb4; t4mb2*t4mb4 - t4mb4*t4mb2; t4mb2*t4mb5 - t4mb5*t4mb2; rel1(t4mb5,t4mb3); rel1(t4mb3,t4mb5) + _q^-1 * t4mb5; ########### the inverse \tau_4 of \tau_4^{-1} ################# t4b1:= b1;; t4b2:=b2;; t4b3:= _q^-1 * qcom2(qcom2(b3,b4),b5)+ b3*a4;; t4b4:= _q * a5 * b5;; t4b5:= _q * a4 * b4;; t4a4:= a5;; t4a5:= a4;; ############ t4 is an algebra homomorphism ############# (_q-_q^-1)* (t4b4 * t4b5 - t4b5 * t4b4) - t4a4 + t4a5; rel1(t4b2,t4b3) + _q^-1 * t4b3; rel1(t4b3,t4b2) + _q^-1 * t4b2; rel1(t4b4,t4b3); rel1(t4b3,t4b4) + _q^-1 * t4b4; t4b2*t4b4 - t4b4*t4b2; t4b2*t4b5 - t4b5*t4b2; rel1(t4b5,t4b3); rel1(t4b3,t4b5) + _q^-1 * t4b5; ########### t4 is the inverse of t4m ############## _q^-1 * qcom2(qcom2(t4mb3,t4mb4),t4mb5)+ t4mb3*t4ma4 - b3; _q * t4ma5 * t4mb5 - b4; _q * t4ma4 * t4mb4 - b5; _q^-1 * qcom2(t4b4,qcom2(t4b5,t4b3))+t4b3*t4a4 - b3; _q^-1 * t4a4* t4b5 - b4; _q^-1 * t4a5 * t4b4 - b5; ############ braid relations for t4 and t3 ############################### ##### To simplify notation we write t434b5 instead of t4 t3 t4 (b5) ###### ##### And similar notation for other evaluations of products of t4 ###### ##### and t3 or other braid group generators ###### ########################################################################### ########### recall the definition of t3: ################################# t3b2:=qcom2(b2,b3);; t3b3:=b3;; t3b4:=qcom2(b4,b3);; t3b5:=qcom2(b5,b3);; t3a4:=a4;; t3a5:=a5;; ########### and recall the definition of t4 ############################### t4b2:=b2;; t4b3:= _q^-1 * qcom2(qcom2(b3,b4),b5)+ b3*a4;; t4b4:= _q * a5 * b5;; t4b5:= _q * a4 * b4;; t4a4:= a5;; t4a5:= a4;; ############################################################################## #### Observe, that both t3 and t4 act as the identity on b1. #### #### Hence we only need to consider the action on the smaller subalgebra #### #### generated by the other generators. #### ############################################################################## t43b2:=qcom2(t4b2,t4b3);; t43b3:=t4b3;; t43b4:=qcom2(t4b4,t4b3);; t43b5:=qcom2(t4b5,t4b3);; t43a4:=t4a4;; t43a5:=t4a5;; ########### t34b2:=t3b2;; t34b3:= _q^-1 * qcom2(qcom2(t3b3,t3b4),t3b5)+ t3b3*t3a4;; t34b4:= _q * t3a5 * t3b5;; t34b5:= _q * t3a4 * t3b4;; t34a4:= t3a5;; t34a5:= t3a4;; ########## t343b2:=qcom2(t34b2,t34b3);; t343b3:=t34b3;; t343b4:=qcom2(t34b4,t34b3);; t343b5:=qcom2(t34b5,t34b3);; t343a4:=t34a4;; t343a5:=t34a5;; ########### t434b2:=t43b2;; t434b3:= _q^-1 * qcom2(qcom2(t43b3,t43b4),t43b5)+ t43b3*t43a4;; t434b4:= _q * t43a5 * t43b5;; t434b5:= _q * t43a4 * t43b4;; t434a4:= t43a5;; t434a5:= t43a4;; ########## t4343b2:=qcom2(t434b2,t434b3);; t4343b3:=t434b3;; t4343b4:=qcom2(t434b4,t434b3);; t4343b5:=qcom2(t434b5,t434b3);; t4343a4:=t434a4;; t4343a5:=t434a5;; ########### t3434b2:=t343b2;; t3434b3:= _q^-1 * qcom2(qcom2(t343b3,t343b4),t343b5)+ t343b3*t343a4;; t3434b4:= _q * t343a5 * t343b5;; t3434b5:= _q * t343a4 * t343b4;; t3434a4:= t343a5;; t3434a5:= t343a4;; #################################################################### ############ final verification of the type B braid relation: ###### ############ all the followsing computations need to give 0 ###### #################################################################### t3434b2 - t4343b2; t3434b3 - t4343b3; t3434b4 - t4343b4; t3434b5 - t4343b5; t3434a4 - t4343a4; t3434a5 - t4343a5; #################################################################### #### Now we approach the type A braid relation between t2 and ##### #### t3 in the same way, again writing t232b1 etc. ##### #################################################################### t2b1:=qcom2(b1,b2);; t2b2:=b2;; t2b3:=qcom2(b3,b2);; t2b4:=b4;; t2b5:=b5;; t2a4:=a4;; t2a5:=a5;; ######################### t3b1:=b1;; t3b2:=qcom2(b2,b3);; t3b3:=b3;; t3b4:=qcom2(b4,b3);; t3b5:=qcom2(b5,b3);; t3a4:=a4;; t3a5:=a5;; ######################### t32b1:=qcom2(t3b1,t3b2);; t32b2:=t3b2;; t32b3:=qcom2(t3b3,t3b2);; t32b4:=t3b4;; t32b5:=t3b5;; t32a4:=t3a4;; t32a5:=t3a5;; ######################### t23b1:=t2b1;; t23b2:=qcom2(t2b2,t2b3);; t23b3:=t2b3;; t23b4:=qcom2(t2b4,t2b3);; t23b5:=qcom2(t2b5,t2b3);; t23a4:=t2a4;; t23a5:=t2a5;; ######################### t232b1:=qcom2(t23b1,t23b2);; t232b2:=t23b2;; t232b3:=qcom2(t23b3,t23b2);; t232b4:=t23b4;; t232b5:=t23b5;; t232a4:=t23a4;; t232a5:=t23a5;; ######################### t323b1:=t32b1;; t323b2:=qcom2(t32b2,t32b3);; t323b3:=t32b3;; t323b4:=qcom2(t32b4,t32b3);; t323b5:=qcom2(t32b5,t32b3);; t323a4:=t32a4;; t323a5:=t32a5;; ############################################################################### ########## Final step in the verification of the type A braid relation ######## ############################################################################### t323b1 - t232b1; t323b2 - t232b2; t323b3 - t232b3; t323b4 - t232b4; t323b5 - t232b5; t323a4 - t232a4; t323a5 - t232a5; ############################################################################### ####### :-) End :-) #####################################