5ce5316a33 2021-03-01 1: % Calculations concerning the special metric of Dieter Egger
5ce5316a33 2021-03-01 2: % Small and capital letters are treated as being equivalent
5ce5316a33 2021-03-01 3:
5ce5316a33 2021-03-01 4: % Dimension of space-time
5ce5316a33 2021-03-01 5: n:=4;
5ce5316a33 2021-03-01 6:
5ce5316a33 2021-03-01 7: % turn off extra echoes
5ce5316a33 2021-03-01 8: off echo;
5ce5316a33 2021-03-01 9:
5ce5316a33 2021-03-01 10: % smaller exponents first
5ce5316a33 2021-03-01 11: on revpri;
5ce5316a33 2021-03-01 12:
5ce5316a33 2021-03-01 13: % Coordinates
5ce5316a33 2021-03-01 14: OPERATOR X$
5ce5316a33 2021-03-01 15: X(0):=t$
5ce5316a33 2021-03-01 16: X(1):=lambda0$
5ce5316a33 2021-03-01 17: X(2):=lambda1$
5ce5316a33 2021-03-01 18: X(3):=lambda2$
5ce5316a33 2021-03-01 19:
5ce5316a33 2021-03-01 20: % Vectors (1-dim arrays start with index 0)
5ce5316a33 2021-03-01 21: ARRAY U(n), V(n)$
5ce5316a33 2021-03-01 22:
5ce5316a33 2021-03-01 23: % place (fixed to origin)
5ce5316a33 2021-03-01 24: U(0):=a0*asin(t)$
5ce5316a33 2021-03-01 25: U(1):=0$
5ce5316a33 2021-03-01 26: U(2):=0$
5ce5316a33 2021-03-01 27: U(3):=0$
5ce5316a33 2021-03-01 28:
5ce5316a33 2021-03-01 29: % Rule
5ce5316a33 2021-03-01 30: trig1:={sin(~x)^2=>(1-cos(x)^2)}$
5ce5316a33 2021-03-01 31: let trig1$
5ce5316a33 2021-03-01 32:
5ce5316a33 2021-03-01 33: % Procedure
5ce5316a33 2021-03-01 34: procedure showMatrix(mm); begin
5ce5316a33 2021-03-01 35: MATRIX hh(n,n)$
5ce5316a33 2021-03-01 36: FOR I:=0:n-1 DO FOR J:=0:n-1 DO hh(I+1,J+1):=mm(I,J)$
5ce5316a33 2021-03-01 37: write hh; end;
5ce5316a33 2021-03-01 38:
5ce5316a33 2021-03-01 39: % Arrays (2-dim arrays start with indices (0,0))
5ce5316a33 2021-03-01 40: ARRAY G(n,n), GINV(n,n), CHRIST(n,n,n), RIEM(n,n,n,n), RICCI(n,n), EINST(n,n)$
5ce5316a33 2021-03-01 41: ARRAY EIT(n,n), ENI(n,n)$
5ce5316a33 2021-03-01 42:
5ce5316a33 2021-03-01 43: % Metric (cellar indices)
5ce5316a33 2021-03-01 44: G(0,0):=a0^2/(1-t^2)$
5ce5316a33 2021-03-01 45: G(1,1):=a0^2*(1-t^2)$
5ce5316a33 2021-03-01 46: G(2,2):=a0^2*(1-t^2)*cos(lambda0)^2$
5ce5316a33 2021-03-01 47: G(3,3):=a0^2*(1-t^2)*cos(lambda0)^2*cos(lambda1)^2$
5ce5316a33 2021-03-01 48:
5ce5316a33 2021-03-01 49: % Inverse Metric (roof indices)
5ce5316a33 2021-03-01 50: MATRIX MG(n,n), MGINV(n,n)$
5ce5316a33 2021-03-01 51: FOR I:=0:n-1 DO FOR J:=0:n-1 DO MG(I+1,J+1):=G(I,J)$
5ce5316a33 2021-03-01 52: MGINV:=1/MG$
5ce5316a33 2021-03-01 53: FOR I:=0:n-1 DO FOR J:=0:n-1 DO GINV(I,J):=MGINV(I+1,J+1)$
5ce5316a33 2021-03-01 54:
5ce5316a33 2021-03-01 55: write "g = ",mg$
5ce5316a33 2021-03-01 56: write "ginv = ",mginv$
5ce5316a33 2021-03-01 57: write "g*ginv = ",mg*mginv$
5ce5316a33 2021-03-01 58:
5ce5316a33 2021-03-01 59: % velocity
5ce5316a33 2021-03-01 60: for i:=0:n-1 do v(i):=df(u(i),t)$
5ce5316a33 2021-03-01 61:
5ce5316a33 2021-03-01 62: % max. velocity
5ce5316a33 2021-03-01 63: Array vmax(n)$
5ce5316a33 2021-03-01 64: svmax:=a0/sqrt(1-t^2)$
5ce5316a33 2021-03-01 65: for i:=0:n-1 do vmax(i):=svmax$
5ce5316a33 2021-03-01 66: svmaxq:=svmax*svmax$
5ce5316a33 2021-03-01 67: write "max. velocity = ",svmax$
5ce5316a33 2021-03-01 68:
5ce5316a33 2021-03-01 69: % energy impulse tensor (eit, roof indices)
5ce5316a33 2021-03-01 70: for i:=0:n-1 do for j:=0:n-1 do eit(i,j):=v(i)*v(j)*(p/svmaxq + rho) - p * ginv(i,j)$
5ce5316a33 2021-03-01 71: write "eit roof = "$ showMatrix(eit)$
5ce5316a33 2021-03-01 72:
5ce5316a33 2021-03-01 73: % energy impulse tensor (eni, cellar indices, including kappa)
5ce5316a33 2021-03-01 74: for i:=0:n-1 do for j:=0:n-1 do eni(i,j) := - kappa * for k:=0:n-1 sum g(i,k)* for l:=0:n-1 sum g(j,l)*eit(k,l)$
5ce5316a33 2021-03-01 75: write "eni = -kappa*(eit cellar) = "$ showMatrix(eni)$
5ce5316a33 2021-03-01 76:
5ce5316a33 2021-03-01 77: % Christoffel symbols (Fliessbach)
5ce5316a33 2021-03-01 78: for k:=0:n-1 do for l:=0:n-1 do for m:=0:n-1 do CHRIST(k,l,m):= for n:=0:n-1 sum GINV(k,n)/2 * (DF(G(m,n),X(l)) + DF(G(l,n),X(m)) - DF(G(m,l),X(n)))$
5ce5316a33 2021-03-01 79:
5ce5316a33 2021-03-01 80: % curvature tensor (Fliessbach)
5ce5316a33 2021-03-01 81: for m:=0:n-1 do for i:=0:n-1 do for k:=0:n-1 do for p:=0:n-1 do RIEM(m,i,k,p) := DF(CHRIST(m,i,k),X(p)) - DF(CHRIST(m,i,p),X(k)) + FOR r:=0:n-1 SUM CHRIST(r,i,k)*CHRIST(m,r,p) - CHRIST(r,i,p)*CHRIST(m,r,k)$
5ce5316a33 2021-03-01 82:
5ce5316a33 2021-03-01 83: % Ricci tensor (Fliessbach)
5ce5316a33 2021-03-01 84: FOR I:=0:n-1 DO FOR J:=0:n-1 DO RICCI(I,J):= FOR M:=0:n-1 SUM RIEM(M,I,M,J)$
5ce5316a33 2021-03-01 85: write "ricci = "$ showMatrix(ricci)$
5ce5316a33 2021-03-01 86:
5ce5316a33 2021-03-01 87: % curvature scalar
5ce5316a33 2021-03-01 88: R:= FOR I:=0:n-1 SUM FOR J:=0:n-1 SUM GINV(I,J)*RICCI(I,J)$
5ce5316a33 2021-03-01 89: write "curvature scalar r = ",r;
5ce5316a33 2021-03-01 90:
5ce5316a33 2021-03-01 91: % Einstein tensor
5ce5316a33 2021-03-01 92: FOR I:=0:n-1 DO FOR J:=0:n-1 DO EINST(I,J):=RICCI(I,J)-R/2*G(I,J)$
5ce5316a33 2021-03-01 93: write "einstein = "$ showMatrix(einst)$
5ce5316a33 2021-03-01 94:
5ce5316a33 2021-03-01 95: % solving field equations
5ce5316a33 2021-03-01 96: write "solving field equations ...";
5ce5316a33 2021-03-01 97: on factor;
5ce5316a33 2021-03-01 98: erho:=solve(eni(0,0)=einst(0,0),rho)$
5ce5316a33 2021-03-01 99: write "mass density = ", erho$
5ce5316a33 2021-03-01 100:
5ce5316a33 2021-03-01 101: ep:=solve(eni(1,1)=einst(1,1),p)$
5ce5316a33 2021-03-01 102: write "pressure = ", ep$
5ce5316a33 2021-03-01 103: off factor;
5ce5316a33 2021-03-01 104:
5ce5316a33 2021-03-01 105: ferho:=sub(ep,erho)$
5ce5316a33 2021-03-01 106: write "final mass density = ", ferho$
5ce5316a33 2021-03-01 107:
5ce5316a33 2021-03-01 108: %--------------------------------------------------------------
5ce5316a33 2021-03-01 109: % write results to file
5ce5316a33 2021-03-01 110: OUT "metric4d_results.txt";
5ce5316a33 2021-03-01 111: off echo;
5ce5316a33 2021-03-01 112: off nat;
5ce5316a33 2021-03-01 113:
5ce5316a33 2021-03-01 114: % Metric
5ce5316a33 2021-03-01 115: write "metric = ";
5ce5316a33 2021-03-01 116: FOR I:=0:n-1 DO FOR J:=0:n-1 DO WRITE "(",I,",",J,") = ", G(I,J)$
5ce5316a33 2021-03-01 117:
5ce5316a33 2021-03-01 118: % Inverse Metric
5ce5316a33 2021-03-01 119: WRITE "inverse metric = ";
5ce5316a33 2021-03-01 120: FOR I:=0:n-1 DO FOR J:=0:n-1 DO WRITE "(",I,",",J,") = ", GINV(I,J)$
5ce5316a33 2021-03-01 121:
5ce5316a33 2021-03-01 122: % Christoffel symbols
5ce5316a33 2021-03-01 123: write "christoffel symbols = ";
5ce5316a33 2021-03-01 124: FOR K:=0:n-1 DO FOR I:=0:n-1 DO FOR J:=0:n-1 DO WRITE "(",K,",",I,",",J,") = ", CHRIST(K,I,J)$
5ce5316a33 2021-03-01 125:
5ce5316a33 2021-03-01 126: % curvature tensor
5ce5316a33 2021-03-01 127: write "curvature tensor = ";
5ce5316a33 2021-03-01 128: FOR I:=0:n-1 DO FOR J:=0:n-1 DO FOR K:=0:n-1 DO FOR L:=0:n-1 DO WRITE "(",I,",",J,",",K,",",L,") = ", RIEM(I,J,K,L)$
5ce5316a33 2021-03-01 129:
5ce5316a33 2021-03-01 130: % Ricci tensor
5ce5316a33 2021-03-01 131: write "ricci tensor = ";
5ce5316a33 2021-03-01 132: FOR I:=0:n-1 DO FOR J:=0:n-1 DO WRITE "(",I,",",J,") = ", RICCI(I,J)$
5ce5316a33 2021-03-01 133:
5ce5316a33 2021-03-01 134: % curvature scalar
5ce5316a33 2021-03-01 135: write "curvature scalar = ",R$
5ce5316a33 2021-03-01 136:
5ce5316a33 2021-03-01 137: % Einstein tensor
5ce5316a33 2021-03-01 138: write "einstein tensor = ";
5ce5316a33 2021-03-01 139: FOR I:=0:n-1 DO FOR J:=0:n-1 DO WRITE "(",I,",",J,") = ",EINST(I,J)$
5ce5316a33 2021-03-01 140:
5ce5316a33 2021-03-01 141: % energy impulse tensor
5ce5316a33 2021-03-01 142: write "energy impulse tensor eit (roof) = ";
5ce5316a33 2021-03-01 143: FOR I:=0:n-1 DO FOR J:=0:n-1 DO WRITE "(",I,",",J,") = ",eit(I,J);
5ce5316a33 2021-03-01 144:
5ce5316a33 2021-03-01 145: % energy impulse tensor
5ce5316a33 2021-03-01 146: write "energy impulse tensor eni (with kappa, cellar) = ";
5ce5316a33 2021-03-01 147: FOR I:=0:n-1 DO FOR J:=0:n-1 DO WRITE "(",I,",",J,") = ",eni(I,J);
5ce5316a33 2021-03-01 148:
5ce5316a33 2021-03-01 149: % solving field equations
5ce5316a33 2021-03-01 150: write "solving field equations ...";
5ce5316a33 2021-03-01 151: on factor;
5ce5316a33 2021-03-01 152: write "mass density = ", erho;
5ce5316a33 2021-03-01 153: write "pressure = ", ep;
5ce5316a33 2021-03-01 154: off factor;
5ce5316a33 2021-03-01 155: write "final mass density = ", ferho;
5ce5316a33 2021-03-01 156:
5ce5316a33 2021-03-01 157: SHUT "metric4d_results.txt";
5ce5316a33 2021-03-01 158:
5ce5316a33 2021-03-01 159: off revpri;
5ce5316a33 2021-03-01 160: on nat;
5ce5316a33 2021-03-01 161:
5ce5316a33 2021-03-01 162: END;
5ce5316a33 2021-03-01 163: