اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدA homogeneous and isotropic universe must have a time varying light speed
196
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 Friedman-Lemaitre-Robertson-Walker (FLRW) universe to vary with the cosmic time coordinate t of FLRW. It must be variable when the radial comoving differential coordinates of FLRW is interpreted as physical and therefore 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), integration of the transformed differentials to obtain stationary coordinates for a short radial distance requires the light speed c(t) to be proportional to the square root of da/dt. Since we assume homogeneity of space, this derived c(t) is the physical light speed on all points of the FLRW universe. This impacts the interpretation of all astronomical observations of distant phenomena that are sensitive to light speed. A world transform from FLRW that has a Minkowski metric close to the origin is shown to have a physical radius out to all points of the visible universe. In order to obtain numerical values for c(t), the general relativity (GR) field equation is extended by using a variable gravitational constant and rest mass that keeps constant the gravitational and particle rest energies. This also keeps constant the proportionality constant between the GR tensors of the field equation and conserves the rest stress-energy tensor of the ideal fluid used in the FLRW GR field equation. In the same way all of special and general relativity is extended to include a variable light speed.
قيم البحث
اقرأ أيضاً
In this paper we aim to investigate a deformed relativistic dynamics well-known as Symmetrical Special Relativity (SSR) related to a cosmic background field that plays the role of a variable vacuum energy density associated to the temperature of the
expanding universe with a cosmic inflation in its early time and an accelerated expansion for its very far future time. In this scenario, we show that the speed of light and an invariant minimum speed present an explicit dependence on the background temperature of the expanding universe. Although finding the speed of light in the early universe with very high temperature and also in the very old one with very low temperature, being respectively much larger and much smaller than its current value, our approach does not violate the postulate of Special Relativity (SR), which claims the speed of light is invariant in a kinematics point of view. Moreover, it is shown that the high value of the speed of light in the early universe was drastically decreased and increased respectively before the beginning of the inflationary period. So we are led to conclude that the theory of Varying Speed of Light (VSL) should be questioned as a possible solution of the horizon problem for the hot universe.
Recently a series of studies on high energy gamma-ray burst~(GRB) photons suggest a light speed variation with linear energy dependence at the Lorentz violation scale of $3.6 times 10^{17}~mathrm{GeV}$, with subluminal propagation of high energy phot
ons in cosmological space. We propose stringy space-time foam as a possible interpretation for this light speed variation. In such a string-inspired scenario, bosonic photon open-string travels textit{in vacuo} at an infraluminal speed with an energy dependence suppressed by a single power of the string mass scale, due to the foamy structure of space-time at small scales, as described by D-brane objects in string theory. We present a derivation of this deformed propagation speed of the photon field in the infrared (IR) regime. We show that the light speed variation, revealed in the previous studies on GRBs time-delay data, can be well described within such a string approach towards space-time foam. We also derive the value of the effective quantum-gravity mass in this framework, and give a qualitative study on the theory-dependent coefficients. We comment that stringent constraints on Lorentz violation in the photon sector from complementary astrophysical observations can also be explained and understood in the space-time foam context.
It has been recently claimed that cosmologies with time dependent speed of light might solve some of the problems of the standard cosmological scenario, as well as inflationary scenarios. In this letter we show that most of these models, when analyze
d in a consistent way, lead to large violations of charge conservation. Thus, they are severly constrained by experiment, including those where $c$ is a power of the scale factor and those whose source term is the trace of the energy-momentum tensor. In addition, early Universe scenarios with a sudden change of $c$ related to baryogenesis are discarded.
We study a model of a scalar field minimally coupled to gravity, with a specific potential energy for the scalar field, and include curvature and radiation as two additional parameters. Our goal is to obtain analytically the complete set of configura
tions of a homogeneous and isotropic universe as a function of time. This leads to a geodesically complete description of the universe, including the passage through the cosmological singularities, at the classical level. We give all the solutions analytically without any restrictions on the parameter space of the model or initial values of the fields. We find that for generic solutions the universe goes through a singular (zero-size) bounce by entering a period of antigravity at each big crunch and exiting from it at the following big bang. This happens cyclically again and again without violating the null energy condition. There is a special subset of geodesically complete non-generic solutions which perform zero-size bounces without ever entering the antigravity regime in all cycles. For these, initial values of the fields are synchronized and quantized but the parameters of the model are not restricted. There is also a subset of spatial curvature-induced solutions that have finite-size bounces in the gravity regime and never enter the antigravity phase. These exist only within a small continuous domain of parameter space without fine tuning initial conditions. To obtain these results, we identified 25 regions of a 6-parameter space in which the complete set of analytic solutions are explicitly obtained.
Structure in the Universe is widely believed to have originated from quantum fluctuations during an early epoch of accelerated expansion. Yet, the patterns we observe today do not distinguish between quantum or classical primordial fluctuations; curr
ent cosmological data is consistent with either possibility. We argue here that a detection of primordial non-Gaussianity can resolve the present situation, and provide a litmus-test for the quantum origin of cosmic structure. Unlike in quantum mechanics, vacuum fluctuations cannot arise in classical theories and therefore long-range classical correlations must result from (real) particles in the initial state. Similarly to flat-space scattering processes, we show how basic principles require these particles to manifest themselves as poles in the $n$-point functions, in the so-called folded configurations. Following this observation, and assuming fluctuations are (i) correlated over large scales, and (ii) generated by local evolution during an inflationary phase, we demonstrate that: the absence of a pole in the folded limit of non-Gaussian correlators uniquely identifies the quantum vacuum as the initial state. In the same spirit as Bells inequalities, we discuss how this can be circumvented if locality is abandoned. We also briefly discuss the implications for simulations of a non-Gaussian universe.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
