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Two CORRECTIONS: 1. Meaning of R0 has also changed. It must be pure number due correct dimensions
of metric parts. It is best to use ref. Chatterjee S. and Bhui B. 1990 definition properly and
use R(t)=a(t), so we would have in my Einstein tensor components in form where R0 = 1.
2. And meaning of k has also changed this is also due reference Chatterjee S. and Bhui B. 1990.
Analytically solved (3+1)D case differential equation of mine does not change,
it used Planck Satellite 2013 results (measurements given in SI-units) and my Guess2 of additional test term for (4+1)D and it is FLAT case (1-Q0 = 0, and this differential equation
does not depend on k or R0) and it is OK solution.
Sorry about these confusions of mine. I put below explanations of different (3+1)D metrics forms
due to clarify these confusions of mine.
Different (3+1)D metric forms from refs. Tolman R.C. 1934 , Chatterjee S. and Bhui B. 1990.
(c = 1 units in my metrics forms).
ds^2=dt^2-dr^2+dth^2*(-r^2*sin(kh)^2)+dph^2*(-r^2*sin(kh)^2*sin(th)^2)+dkh^2*(-r^2)
(t=>0, unique definition area of 4D sphere, r=>0, -Pi<ph<= Pi, 0<=th<=Pi, 0<=kh<=Pi)
(4+1)D = 5D metrics (with a(t) which satisfies Einstein equations,
Einstein tensor tt-component is only used in my calculations).
ds^2=dt^2-a(t)^2*dr^2/(1-k*r^2)+dth^2*(-r^2*a(t)^2*sin(kh)^2)+dph^2*(-r^2*a(t)^2*sin(kh)^2*sin(th)^2)+dkh^2*(-r^2*a(t)^2),
k= constant of integration ,
(Ref. Chatterjee S. and Bhui B. 1990.
Homogeneous cosmological model in higher dimension.
Mon. Not. astr. Soc. (1990) 247, 57-51. (c=1, G=1 units).
Def. of constant of integration k on page 58, formulae (21) and (22) and metrics (23) and (2)
k = 2*k_bar/(n*(n-1)), k_bar is an arbitrary constant of integration
and n=3 in case of 5 dimensional space-time,
ds^2=dt^2-R(t)^2*(dr^2/(1-k*r^2)+r^2*dx_n^2), dx_n^2=dth_1^2+sin(th_1)^2*dth_2^2+…sin(th_1)^2*sin(th_2)^2…sin(th_(n-1))^2*dth_n^2,
My used letters: th_1 = kh, th_2 = th, th_3 = ph in case of 5 dimensions D = n+2, where n = 3).
(unique (?) definition area for this metrics:
t=>0 (?),1-k*r^2<>0 (?), r=>0 (?), -Pi<ph<= Pi, 0<=th<=Pi, 0<=kh<=Pi, ?)
(+,-,-,-,-) signature used here and also in my calculations.
Model from Tolman R. C. 1934: Einstein field equations form (page 376)
R_uv-(1/2)*R*g_uv+L*g_uv = -8*Pi*T_uv
Different forms of (3+1)D metrics used by Tolman R. C. 1932 (c=1, G=1 units, exp(g(t))=a(t)^2,
(-,-,-,+) signature used by Tolman , I used (+,-,-,-) signature for (3+1)D and (+,-,-,-,-) for 5D):
(Ref. Tolman, R.C. 1934. (reprint 1987). Relativity Thermodynamics and Cosmology. Dover Publications, Inc. New York. Manufactured in the United States of America.
502 pages, THIS COPY below pp. 370-372 . ThisCOPY is due that perhaps (4+1)D case
could be possible more properly to be generalized with help of this (3+1)D text of Tolman ?)
ds^2=dt^2-(a(t)^2/(1+r^2/(4*R0^2))^2)*(dr^2+r^2*dth^2+r^2*sin(th)^2*dph^2),
ds^2=dt^2-(a(t)^2/(1+r^2/(4*R0^2))^2)*(dx^2+dy^2+dz^2),
x=r*sin(th)*cos(ph),y=r*sin(th)*sin(ph),z=r*cos(ph),
r=sqrt(x^2+y^2+z^2),
ds^2=dt^2-a(t)^2*(dr^2/(1-r^2/R0^2)+ r^2*dth^2+r^2*sin(th)^2*dph^2),
r = r_ba r, r_bar = r/(1+r^2/(4*R0^2)),
ds^2=dt^2-R0^2*a(t)^2*(dkh^2+sin(kh)^2*dth^2+sin(kh)^*sin(th)^2*dph^2),
r_bar = R0*sin(kh).
ds^2=dt^2-a(t)^2*(dz1^2+dz2^2+dz3^2+dz4^2),
z1 = R0*sqrt(1-r^2/R0^2), z2 = r*sin(th)*cos(ph), z3 = r*sin(th)*sin(ph), z4 = r*cos(th),
r = r_bar.
This last metrics form at any given time t permits us to regard our original space as
embedded in a Euclidean space of a larger number of dimensions.
It will be simplest, however, as suggested by the last form of the line element, to
regard the spatial extent of this non-static universe at any given time t as the whole
three-dimensional spherical surface defined by
z1^2+z2^2+z3^2+z4^2 = R0^2,
embedded in the four-dimensional Euclidean space (z1.z2.z3,z4).
Since the proper distance at time t corresponding to the coordinate interval
dz1, would from the form of the line element
ds^2=dt^2-a(t)^2*(dz1^2+dz2^2+dz3^2+dz4^2),
would evidently be
dl0=a(t)*dz1,
with similar expressions fort he other spatial coordinates, it is evident that
the radius of this spherical surface would be
R = R0*a(t),
Hence this quantity is often spoken of as the radius of the non-static universe,
and the geometry is spoken of as being that for the surface of a sphere in
four dimensions whose radius is a function of the time.
It should be noted, however, in accordance with the equation
-c1/c2 = 1/R0^2, (c1 and c2 are constants of intgration),
by which R0 was introduced, that this radius could be real, imaginary, or
infinite.
If we assume the radius real, the total integrated proper spatial volume
of the model at any selected time t would be give in accordance with
ds^2=dt^2-R0^2*a(t)^2*(dkh^2+sin(kh)^2*dth^2+sin(kh)^*sin(th)^2*dph^2),
r_bar = R0*sin(kh).
by
v0 = int_0^2*Pi int_0^Pi int_0^Pi (R0^3*a(t)^3*sin(kh)^2*sin(th)*dkh*dth*dph) =
= 2^Pi^2*R0^3*a(t)^3
and the total integrated proper distance around the universe would be
l0 = 2*Pi*R0*a(t).
Taking the spatial geometry as elliptical rather than spherical, the corresponding
quantities would be half as great.
If we assume the radius infinite or imaginary, the model would be spatially
open rather than closed and the total proper volume could be most conveniently
calculated, in accordance with the form
ds^2=dt^2-R0^2*a(t)^2*(dkh^2+sin(kh)^2*dth^2+sin(kh)^*sin(th)^2*dph^2),
r_bar = R0*sin(kh),
for the line element, from the expression
v0 = int_0^2*Pi int_0^Pi int_0^infinity (a(t)^3/sqrt(1+r^2/A^2)*r^2*sin(th)*dr*dth*dph) =
= infinity,
r =r_bar, r_bar = r/(1+r^2/(4*R0^2)),
where A^2 is a positive quantity which can assume the value infinity, and upper limit
for r_bar can be taken as infinity without disturbing the possibility for a physical interpretation
of the line element by changing its signature. Evaluating the integral we then obtain an
infinite total proper volume for open models.
The symmetrical form
ds^2=dt^2-a(t)^2*(dz1^2+dz2^2+dz3^2+dz4^2),
which we have been able to give to the line element by the device of considering
a larger number of dimensions, is valuable in clearly showing the spatial homogeneity
of the model already mentioned in the connexion with
ds^2=dt^2-a(t)^2*b(r)^2*(dr^2+r^2*dth^2+r^2*sin(th)^2*dph^2),
(exp(f(r))=b(r)^2, exp(g(t))=a(t)^2).
It is an interesting extension of Schur’s theorem of Riemannian geometry, that
the spatial isotropy which we have assumed for observers at all points in space-time
should lead to an orthogonal separation into space and time and to homogeneity for
the sub-manifold of space. It is in accordance with this result that our present models
of the universe have been designated as non-static homogeneous cosmological models.
Hannu
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