/////////////////////////////////// // Modifications for Theta Graph // /////////////////////////////////// // The following contains an example for Cell5 combinatorial type of the modified tropical theta graphs in R^3. The curve can be visualized by means of projections. // We use the parameters b5, b4, b34, b2, where b3 = b34+b4, a5 = -b5^2, a4 = b4^2, a3 = b3^2, a2 = b2^2. we use this strategy since the modifications involve square roots. // The parameters w5,w3, w34, w2 satisfy: // PiecesTypeIICone3[1][1].Hrepresentation() // (An equation (1, -2, 1, 0) x + 0 == 0, // An inequality (1, 0, -1, 0) x + 0 >= 0, // An inequality (0, 0, 1, -1) x + 0 >= 0) // We want cancellation, namely in(b4)^2 = in(b5*b34). We aim for a subdivision containing the edge xy---x^3. For this, we multiply our original vector by 3 (so we replace t by t^3) and add a tail to b34 of the form t^(6+e) for e=1, since we need ht(x3)>w3 + (w5+w3+w2)/3, and we want integer heights. //////////////////////////////////////////////////////// // Case 5 (with cancellation): 2w3 = w34+w5, w34 > w2 // //////////////////////////////////////////////////////// LIB "all.lib"; LIB "poly.lib"; LIB "tropical.lib"; LIB "elim.lib"; ring rr = (0,t), (b2,b34,b4,b5, x,y,z),dp; poly f=y^2-x*(x-b2^2)*(x-(b4+b34)^2)*(x-b4^2)*(x+b5^2); // f; // b2^2*b34^2*b4^2*b5^2*x+2*b2^2*b34*b4^3*b5^2*x+b2^2*b4^4*b5^2*x+b2^2*b34^2*b4^2*x^2+2*b2^2*b34*b4^3*x^2+b2^2*b4^4*x^2-b2^2*b34^2*b5^2*x^2-2*b2^2*b34*b4*b5^2*x^2-2*b2^2*b4^2*b5^2*x^2-b34^2*b4^2*b5^2*x^2-2*b34*b4^3*b5^2*x^2-b4^4*b5^2*x^2-b2^2*b34^2*x^3-2*b2^2*b34*b4*x^3-2*b2^2*b4^2*x^3-b34^2*b4^2*x^3-2*b34*b4^3*x^3-b4^4*x^3+b2^2*b5^2*x^3+b34^2*b5^2*x^3+2*b34*b4*b5^2*x^3+2*b4^2*b5^2*x^3+b2^2*x^4+b34^2*x^4+2*b34*b4*x^4+2*b4^2*x^4-b5^2*x^4-x^5+y^2 setring(rr); poly B5 = (1); poly B4 = (2*t^3); poly B34 = (4*t^6-t^7); poly B2 = (17*t^9+13*t^12); map P2 = rr, B2, B34, B4, B5, x, y, z; poly ff = P2(f); ring r = (0,t),(x,y),dp; map newP2 = rr, 0,0,0,0,x,y,0; poly f2 = newP2(ff); // f2; // -x5+(169t24+442t21+289t18+t14-8t13+16t12-4t10+16t9+8t6-1)*x4+(-169t38+1352t37-2704t36-442t35+4212t34-9776t33-289t32+4080t31-13048t30+1156t28-8160t27-2143t24+442t21-4t20+32t19+225t18+16t16-64t15+t14-8t13-4t10+16t9+8t6)*x3+(676t44-5408t43+10816t42+1768t41-16848t40+39104t39+987t38-14968t37+46784t36-442t35-412t34+15792t33-289t32+4080t31-8424t30+1156t28-8160t27-2312t24-4t20+32t19-64t18+16t16-64t15-16t12)*x2+y2+(676t44-5408t43+10816t42+1768t41-16848t40+39104t39+1156t38-16320t37+49488t36-4624t34+25568t33+4624t30)*x drawTropicalCurve(f2,"max"); /////////////////// // XZ-projection // /////////////////// poly B5 = newP2(B5); poly B4 = newP2(B4); poly B34 = newP2(B34); poly B2 = newP2(B2); poly B3 = B34 + B4; poly g2 = substitute(f2, y, y+B3*B4*B5*x-B5*x^2); // g2; // -x5+(169t24+442t21+289t18+t14-8t13+16t12-4t10+16t9+8t6)*x4+(-169t38+1352t37-2704t36-442t35+4212t34-9776t33-289t32+4080t31-13048t30+1156t28-8160t27-2143t24+442t21-4t20+32t19+225t18+16t16-64t15+t14-8t13)*x3-2*x2y+(676t44-5408t43+10816t42+1768t41-16848t40+39104t39+987t38-14968t37+46784t36-442t35-412t34+15792t33-289t32+4080t31-8424t30+1156t28-8160t27-2312t24)*x2+(-4t10+16t9+8t6)*xy+y2+(676t44-5408t43+10816t42+1768t41-16848t40+39104t39+1156t38-16320t37+49488t36-4624t34+25568t33+4624t30)*x drawTropicalCurve(g2,"max"); /////////////////// // ZY-projection // /////////////////// ring s = (0,t),(x,y,z),dp; map P = r, x,y; poly ff= P(f2); poly B5 = P(B5); poly B4 = P(B4); poly B3 = P(B3); poly B34 = P(B34); ideal I = (ff,z-y+B3*B4*B5*x-B5*x^2); poly fnox= eliminate(I,x)[1]; // Replace z by y and y by x so that the pictures are not flipped. ring r2 = (0,t),(x,y),dp; setring(r2); map PP = s,0,x,y; poly newfnox = PP(fnox); // newfnox; // 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drawTropicalCurve(newfnox,"max");