اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدOn a c(t)-Modified Friedman-Lemaitre-Robertson-Walker Universe
55
0
0.0
(
0
)
تأليف
Robert C. Fletcher
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
This paper presents a compelling argument for the physical light speed in the homogeneous and isotropic Friedman-Lemaitre-Robertson-Walker (FLRW) universe to vary with the cosmic time coordinate t of FLRW. It will be variable when the radial co-moving differential coordinate of FLRW is interpreted as physical and therefor transformable by a Lorentz transform locally to differentials of stationary physical coordinates. Because the FLRW differential radial distance has a time varying coefficient a(t), in the limit of a zero radial distance the light speed c(t) becomes time varying, proportional to the square root of the derivative of a(t) Since we assume homogeneity of space, this derived c(t) is the physical light speed for all events in the FLRW universe. This impacts the interpretation of astronomical observations of distant phenomena that are sensitive to light speed. A transform from FLRW is shown to have a physical radius out to all radial events in the visible universe. This shows a finite horizon beyond which there are no galaxies and no space. The general relativity (GR) field equation to determine a(t) and c(t) is maintained by using a variable gravitational constant and rest mass that keeps constant the gravitational and particle rest energies. This keeps constant the proportionality constant between the GR tensors of the field equation and conserves the stress-energy tensor of the ideal fluid used in the FLRW GR field equation. In the same way all of special and general relativity can be extended to include a variable light speed.
قيم البحث
اقرأ أيضاً
A regularization procedure has been recently suggested for regularizing Big Bang singularities in Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetimes. We argue that this procedure is only appliable to one case of Big Bang singularities and does not affect other types of singularities.
The semi classical cosmology approximation for a Friedman Robertson Walker geometry coupled to a field is considered. A power series of the field with coefficients that depend on the radius of the geometry is proposed, and the equations for the coefficients are solved.
We completely classify Friedmann-Lema^{i}tre-Robertson-Walker solutions with spatial curvature $K=0,pm 1$ and equation of state $p=wrho$, according to their conformal structure, singularities and trapping horizons. We do not assume any energy conditi
ons and allow $rho < 0$, thereby going beyond the usual well-known solutions. For each spatial curvature, there is an initial spacelike big-bang singularity for $w>-1/3$ and $rho>0$, while no big-bang singularity for $w<-1$ and $rho>0$. For $K=0$ or $-1$, $-1<w<-1/3$ and $rho>0$, there is an initial null big-bang singularity. For each spatial curvature, there is a final spacelike future big-rip singularity for $w<-1$ and $rho>0$, with null geodesics being future complete for $-5/3le w<-1$ but incomplete for $w<-5/3$. For $w=-1/3$, the expansion speed is constant. For $-1<w<-1/3$ and $K=1$, the universe contracts from infinity, then bounces and expands back to infinity. For $K=0$, the past boundary consists of timelike infinity and a regular null hypersurface for $-5/3<w<-1$, while it consists of past timelike and past null infinities for $wle -5/3$. For $w<-1$ and $K=1$, the spacetime contracts from an initial spacelike past big-rip singularity, then bounces and blows up at a final spacelike future big-rip singularity. For $w<-1$ and $K=-1$, the past boundary consists of a regular null hypersurface. The trapping horizons are timelike, null and spacelike for $win (-1,1/3)$, $win {1/3, -1}$ and $win (-infty,-1)cup (1/3,infty)$, respectively. A negative energy density ($rho <0$) is possible only for $K=-1$. In this case, for $w>-1/3$, the universe contracts from infinity, then bounces and expands to infinity; for $-1<w<-1/3$, it starts from a big-bang singularity and contracts to a big-crunch singularity; for $w<-1$, it expands from a regular null hypersurface and contracts to another regular null hypersurface.
The integral of the energy density function $mathfrak m$ of a closed Robertson-Walker (RW) spacetime with source a perfect fluid and cosmological constant $Lambda$ gives rise to an action functional on the space of scale functions of RW spacetime met
rics. This paper studies closed RW spacetimes which are critical for this functional, subject to volume-preserving variations (critical RW spacetimes). A complete classification of critical RW spacetimes is given and explicit solutions in terms of Weierstrass elliptic functions and their degenerate forms are computed. The standard energy conditions (weak, dominant, and strong) as well as the cyclic property of critical RW spacetimes are discussed.
In a recent paper [arXiv:1206.4916] by T. Padmanabhan, it was argued that our universe provides an ideal setup to stress the issue that cosmic space is emergent as cosmic time progresses and that the expansion of the universe is due to the difference
between the number of degrees of freedom on a holographic surface and the one in the emerged bulk. In this note following this proposal we obtain the Friedmann equation of a higher dimensional Friedmann-Robertson-Walker universe. By properly modifying the volume increase and the number of degrees of freedom on the holographic surface from the entropy formulas of black hole in the Gauss-Bonnet gravity and more general Lovelock gravity, we also get corresponding dynamical equations of the universe in those gravity theories.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
