Spacetime Curvature And Speed Of Light

What if Gravity is the 5th emergent dimension? (So mass/energy of a particle is its gravity dimension location (+ or -).
(2D surface of a sphere is bent in 3rd dimension. 4D spacetime is bent in the 5th (Gravity) dimension whenever (+ or -) energy/mass is present.)

When a positive spacetime curvature is present, speed of light must slowdown passing from that location. (Just like light slows down when it enters water from air and refracts.)
And if so, then how index of refraction and current speed of light can be calculated for any spacetime location?

Spacetime curvature (which we can calculate) determines deflection angle (which we can also calculate).
Using Snell's Law:
sin(t0)/sin(t1)=v0/v1=n1/n0
Also if c is the speed when there is no curvature.
And if we plug in the values we know/assume then this is what we have:
sin(t0)/sin(t1)=c/v1=n1/n0

We can calculate total bending (deflection) angle of light (in radians) in General Relativity:
deltaPhi=4*G*M/C^2/R (M:Mass in kg; R:Distance from center in meters; C:Speed of light in m/s; G:6.7E-11)

Assume incoming angle of light is 90 degrees (pi/2 radians) (for refraction index=1 because n=c/v and no spacetime curvature in the first medium):
=> 1/sin(t1)=c/v1=n1/1 =>
1/sin(deltaPhi)=c/v1=n1/1 =>
1/sin(4*G*M/c^2/r)=c/v1=n1/1 =>
n1=c/v1=1/sin(4*G*M/c^2/r) (Index of refraction for any spacetime location bending light)
(=> Possible extreme values:1/0=inf or -inf depending on direction of approach;1/1=1;1/-1=-1 => Range: -inf to +inf)
v1=c/n1=c*sin(4*G*M/c^2/r) (current speed of light for any spacetime location bending light)
(=> Possible extreme values:c*0=0;c*1=c;c*(-1)=-c => Range: -inf to +inf)
(Negative c would mean time is flowing backwards there!? c is the flow rate of time (event information flow (perception) rate) anywhere.)
(So it is not possible to make time move faster than c but it can be slowed and its direction maybe changed using negative energy/mass.)
(Light slows down in (positive) gravitational field because it is denser from light point of view. Imagine more positive energy/mass virtual particles on the way.

Gravitational field is actually local polarization of the virtual particle (each with + or - energy/mass) balance at any spacetime location.) If the total net energy is negative then curvature would be negative. Then index of refraction would also be negative.

(The speed of light anywhere is speed of information flow between the CA cells which determine perception of events in Relativity by any observer.)

https://en.wikipedia.org/wiki/Refractive_index
https://en.wikipedia.org/wiki/Snell%27s_law