Recent content by Giammy85

  1. G

    Fortran How can I change the starting index of an array in Fortran?

    I'm try to read some files in subdirectories and create some other files in my present location: program multiread ! implicit none !variables integer :: n, k, i integer :: j, m2 real(8) :: pratio, crap, rmsttv character(len=42) :: filein(98) character(len=10) :: fileout(14)...
  2. G

    What Causes Type/Rank Mismatch in Argument 'a'?

    Unfortunately by doing so I have ever more error messages: In file tidalevolution.f90:84 real, dimension(:), allocatable :: a, e, time 1 Error: ALLOCATABLE attribute conflicts with DUMMY attribute at (1) In file tidalevolution.f90:86...
  3. G

    What Causes Type/Rank Mismatch in Argument 'a'?

    Hi, I'm allocating the dimension of some arrays once I have calculated steps, then I send the allocated arrays to a function but I have the error Type/rank mismatch in argument 'a'. What am I doing wrong? Cheers integer i, steps, noutput, savestep double integrationtime...
  4. G

    Polytropic Models: Solving Problem at Slide 5

    are you talking about this? http://astronomy.sussex.ac.uk/~pd48/Polytropes.ppt I can clearly see them in every pc I used The problem is that according to the author of this ppt for a homogenous gas sphere the polytropic index n has to be equal to 0 and so γ=1+1/n=infinite. Instead I...
  5. G

    Polytropic Models: Solving Problem at Slide 5

    Hello, I am studing polytropes and I found something intersting here: http://astronomy.sussex.ac.uk/~pd48/Polytropes.ppt I got a problem at slide 5 where she says that the polytropic index n is equal to 0 for a homogenous gas sphere. I am not able to figure out why. From the polytropic...
  6. G

    Surface with Ricci scalar equal to two

    mhm... I think it is a sphere of radius r=1
  7. G

    Surface with Ricci scalar equal to two

    A two-dimensional Rienmannian manifold has a metric given by ds^2=e^f dr^2 + r^2 dTHETA^2 where f=f(r) is a function of the coordinate r Eventually I calculated that Ricci scalar is R=-1/r* d(e^-f)/dr if e^-f=1-r^2 what is this surface? In this case R comes to be equal to 2 I've...
  8. G

    Why the metric is covariantly constant?

    Here the solution of my teacher: Since g_ac is a (0,2) tensor than g_ac;b= g_ac,b-GAMMA^d_ab*g_dc-GAMMA^d_cb*g_ad In a Local Inertial Frame g_ac,b=0 in a point P, than since the connection depends on the first partial derivatives of the metric GAMMA^d_ab=GAMMA^d_cb=0 in P. So we have in...
  9. G

    Surface with Ricci scalar equal to two

    A two-dimensional Rienmannian manifold has a metric given by ds^2=e^f dr^2 + r^2 dTHETA^2 where f=f(r) is a function of the coordinate r Eventually I calculated that Ricci scalar is R=-1/r* d(e^-f)/dr if e^-f=1-r^2 what this surface is? In this case R comes to be equal to 2 I've...
  10. G

    Why the metric is covariantly constant?

    1 in general for a tensor T of upper indices a... and lower indices b... T^a..._b...;c=T^a..._b...,c+GAMMA^a_dc*T^d..._b...+...-GAMMA^d_bc*T^a..._d...-... So for (0,1) tensor: V_a;b=V_a,b-GAMMA^c_ab*V_c... where GAMMA is the connection and ,b indicates the derivative with respect to b...
  11. G

    Why the metric is covariantly constant?

    ;b is the covariant derivative with respect to b
  12. G

    Why the metric is covariantly constant?

    you can show that the metric is covariantly constant by writing: V_a;b=g_acV^c;b for linearity V_a;b=(g_acV^c);b=g_ac;bV^c+g_acV^c;b than must be g_ac;b=0 is there an alternative argument (even shorter than this) that show that the metric is covariantly constant? if I calculate...
  13. G

    Why the metric is covariantly constant?

    yes, I have but I haven't studied yet what a torsion field is
Back
Top