Space–time geometry and the velocity of light

2018 ◽  
Vol 33 (30) ◽  
pp. 1850183 ◽  
Author(s):  
B. G. Sidharth ◽  
Abhishek Das
Keyword(s):  
Space Time ◽  
Status Quo ◽  
Velocity Of Light ◽  
Underlying Geometry

In this paper, we investigate the possibility of superluminal velocities and the appertaining underlying geometry. We consider three different approaches and arrive at the same status quo.

scholarly journals D-FOAM PHENOMENOLOGY: DARK ENERGY, THE VELOCITY OF LIGHT AND A POSSIBLE D-VOID

2011 ◽  
Vol 26 (13) ◽  
pp. 2243-2262 ◽  
Author(s):  
JOHN ELLIS ◽  
NICK E. MAVROMATOS ◽  
DIMITRI V. NANOPOULOS
Keyword(s):  
Refractive Index ◽  
Dark Energy ◽  
Energy Density ◽  
Particle Density ◽  
Space Time ◽  
Dark Energy Density ◽  
Present Epoch ◽  
Brane Model ◽  
Velocity Of Light ◽  
Reduced Density

In a D-brane model of cosmology and space–time foam, there are contributions to the dark energy that depend on the D-brane 10-velocities and on the density of D-particle defects in the ten-dimensional bulk. The latter may also reduce the speeds of energetic photons, establishing a phenomenological connection with astrophysical probes of the universality of the velocity of light. Specifically, the cosmological dark energy density measured at the present epoch may be linked to the apparent retardation of energetic photons propagating from nearby AGN's. However, this nascent field of "D-foam phenomenology" may be complicated by variations in the D-particle density encountered at different cosmological epochs. A reduced density of D-particles encountered at redshifts z ~ 1 — a "D-void" — would increase the dark energy while suppressing the vacuum refractive index, and thereby might reconcile the AGN measurements with the relatively small retardation seen for the energetic photons propagating from GRB 090510, as measured by the Fermi satellite.

scholarly journals BRANS–DICKE COSMOLOGY IN AN ANISOTROPIC MODEL WHEN VELOCITY OF LIGHT VARIES

2002 ◽  
Vol 11 (06) ◽  
pp. 921-932 ◽  
Author(s):  
SUBENOY CHAKRABORTY ◽  
NARAYAN CHANDRA CHAKRABORTY ◽  
UJJAL DEBNATH
Keyword(s):  
Scalar Field ◽  
Asymptotic Behaviour ◽  
Space Time ◽  
Anisotropic Model ◽  
Time Model ◽  
Velocity Of Light ◽  
Space Time Model ◽  
Flatness Problem

In this paper, we have studied Brans–Dicke (BD) Cosmology in an anisotropic Kantowski–Sachs space–time model; considering variation of the velocity of light. We have addressed the flatness problem considering both cases namely (i) when the Brans–Dicke scalar field φ is constant (ii) when φ varies, specially for radiation dominated era perturbatively and non-perturbatively and asymptotic behaviour have been studied.

scholarly journals Theoretical Value of Hubble’s constant is a Salient Feature of Experimental Results- New Insight in to Origin of Universe

2020 ◽  
Author(s):  
Siva Prasad Kodukula
Keyword(s):  
Neutral Hydrogen ◽  
Salient Feature ◽  
Theoretical Work ◽  
Space Time ◽  
Red Shift ◽  
Experimental Results ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Square Root ◽  
Atacama Cosmology Telescope ◽  
Velocity Of Light

Specifically this work is based on the concept of ‘dark energy’ as a phenomenal effect of expansion through which a theoretical value of Hubble’s constant has been introduced. It is a constant that is based on a postulate that the square root of ratio of the Siva’s constant ‘K’ and Hubble’s constant ‘H’ is exactly equal to the diameter of the neutral hydrogen atom. That is the, exact theoretical value of Hubble’s constant. This is always constant .However, space-time conversions and the changes in the velocity of light will affect the distance and velocity in Hubble’s equation. Deviation factors in velocity, distance and the Hubble’s constant have been calculated separately which are affected by change of velocity of light with expansion of space time. The observations are related to red shift. So the change factor in terms of Hubble’s constant has been calculated with respect to red shift. Thus a factor which affects the theoretical Hubble’s constant has been calculated to find the exact value of Hubble’s constant that satisfies the experimental results. The present theoretical value of Hubble’s constant has been calculated. The experimental results by plank, ACT (Atacama Cosmology Telescope), WMAP (Wilkinson Microwave Anisotropy Probe) etc. experiments are at par with the theoretical result. Thus the ontology of space time introduced in this theoretical work supposed to be correct and leads to a new theory of origin of universe for which a brief description has been provided.

Discrete Time Flowing and A Contradiction to Einstein’s Assumptions

2015 ◽  
Vol 11 (3) ◽  
pp. 3208-3217
Author(s):  
K.H.K. Geerasee Wijesuriya
Keyword(s):  
String Theory ◽  
Discrete Time ◽  
Special Theory ◽  
Space Time ◽  
Theory Of Relativity ◽  
Special Theory Of Relativity ◽  
Specific Result ◽  
Time Duration ◽  
Velocity Of Light ◽  
The Universe

Due to the limited velocity of light, there is a time duration to propagate a light ray between any two distinct spacetime points in the universe. Upon that argument, author‟s attempt is to obtain a very specific result that may useful for the Cosmology subject fields, string theory and the Astronomy subject fields. The final result implies that the time flowing depends on the space time location and time flowing is a relative fact in the universe. “Time flowing is a relative fact” does not mean the notion in the Special theory of Relativity regarding the relativity in the time.

Some exact solutions of gravitational waves coupled with fluid motions

1985 ◽  
Vol 402 (1823) ◽  
pp. 205-224 ◽  
Keyword(s):  
Exact Solutions ◽  
Gravitational Waves ◽  
Perfect Fluid ◽  
Space Time ◽  
Velocity Of Sound ◽  
Time Singularity ◽  
Einstein's Equations ◽  
The Past ◽  
Velocity Of Light ◽  
Cosmological Solutions

Some exact solutions of Einstein’s equations are found which represent the interaction of gravitational waves with a perfect fluid in which the velocity of sound equals the velocity of light. These solutions, unlike the solutions representing the collision of impulsive gravitational waves, are bounded by a space–time singularity and have some resemblance to cosmological solutions: every time-like trajectory, extended into the past, encounters the singularity. Moreover, in the generic case, matter may be considered as being created at the singularity.

Space-time on the rotating disk

1951 ◽  
Vol 47 (1) ◽  
pp. 177-189 ◽  
Author(s):  
Behram Kurşunogğlu
Keyword(s):  
Rotating Disk ◽  
Space Time ◽  
Strained State ◽  
Velocity Of Light ◽  
Unstrained State ◽  
Image Position ◽  
The Waves

1. Introduction. In a recent paper Clark (1) has dealt with the problem of the rotating disk, the material of which is such that the waves of dilatation in this particular material travel with the velocity of light. The material of the disk is supposed to be under an isotropic stress p when in a strained state, and the relation between stress p and the dilatation Δ is found to be connected by an expressionwhere a = density in the unstrained state, and Δ is given byUi (i = 1, 2, 3) are the components of the strain.

Finsler spaces and the underlying geometry of space-time

1985 ◽  
Vol 112 (1-2) ◽  
pp. 23-25 ◽  
Author(s):  
R.K. Tavakol ◽  
N. Van Den Bergh
Keyword(s):  
Space Time ◽  
Finsler Spaces ◽  
Underlying Geometry

Space, Time and Einstein

2002 ◽  
Author(s):  
J. B. Kennedy
Keyword(s):  
Space Time
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