scholarly journals Exact Four-Dimensional Exploding Universe Solution in String Theory

1997 ◽  
Vol 12 (19) ◽  
pp. 1355-1360 ◽  
Author(s):  
Shin'ichi Nojiri
Keyword(s):  
String Theory ◽  
Analytic Continuation ◽  
Flat Space ◽  
Fixed Time ◽  
Space Time ◽  
Speed Of Light ◽  
Left Behind ◽  
Flat Background ◽  
The Universe

We obtain a four-dimensional exploding universe solution in string theory. The solution is obtained from the string theory in the flat background by using non-Abelian T-duality and the analytic continuation. In the solution, the radius of the universe is finite for fixed time and the universe is surrounded by the boundary consists of singularity. The boundary runs away with the speed of light and the flat space–time is left behind.

scholarly journals WHY THERE IS SOMETHING SO CLOSE TO NOTHING: TOWARDS A FUNDAMENTAL THEORY OF THE COSMOLOGICAL CONSTANT

2007 ◽  
Vol 22 (10) ◽  
pp. 1797-1818 ◽  
Author(s):  
VISHNU JEJJALA ◽  
DJORDJE MINIC
Keyword(s):  
Quantum Theory ◽  
String Theory ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Uncertainty Relation ◽  
Space Time ◽  
Large Size ◽  
Minkowski Space Time ◽  
The Universe ◽  
Canonical Quantum

The cosmological constant problem is turned around to argue for a new foundational physics postulate underlying a consistent quantum theory of gravity and matter, such as string theory. This postulate is a quantum equivalence principle which demands a consistent gauging of the geometric structure of canonical quantum theory. We argue that string theory can be formulated to accommodate such a principle, and that in such a theory the observed cosmological constant is a fluctuation about a zero value. This fluctuation arises from an uncertainty relation involving the cosmological constant and the effective volume of space–time. The measured, small vacuum energy is dynamically tied to the large "size" of the universe, thus violating naive decoupling between small and large scales. The numerical value is related to the scale of cosmological supersymmetry breaking, supersymmetry being needed for a nonperturbative stability of local Minkowski space–time regions in the classical regime.

Further Results of Flat Space-time Theory of Gravitation

2005 ◽  
Vol 60 (4) ◽  
pp. 255-264
Author(s):  
Walter Petry
Keyword(s):  
Solar System ◽  
Flat Space ◽  
High Energy ◽  
Space Time ◽  
Cosmological Models ◽  
Compact Objects ◽  
Anomalous Acceleration ◽  
Theory Of Gravitation ◽  
The Universe ◽  
Time Theory

Abstract The anomalous acceleration of spacecrafts in the solar system is explained. An explanation of the observed superluminal velocities of jets at extragalactic objects is given. The extension of quasars can be larger as generally assumed, i. e. quasars must not be very compact objects. An explanation of the high energy loss per unit time of quasars is given. The relation between the velocity of an object in the universe and its redshift is stated. All these results are received from cosmological models studied by flat space-time theory of gravitation and the post-Newtonian approximation of perfect fluid in these cosmological models where clocks at earlier times are going faster than at present.

scholarly journals A TOY MODEL OF CLOSED STRING TACHYON EFFECTIVE ACTION

2005 ◽  
Vol 20 (07) ◽  
pp. 1481-1493
Author(s):  
J. KLUSOŇ
Keyword(s):  
Exact Solution ◽  
String Theory ◽  
Effective Action ◽  
Flat Space ◽  
Closed String ◽  
Space Time ◽  
Bosonic String ◽  
Two Dimensional ◽  
Linear Dilaton ◽  
Bosonic String Theory

In this paper we propose the toy model of the closed string tachyon effective action that has marginal tachyon profile as its exact solution in case of constant or linear dilaton background. Then we will apply this model for description of two-dimensional bosonic string theory. We will find that the background configuration with the spatial dependent linear dilaton, flat space–time metric and marginal tachyon profile is the exact solution of our model even if we take into account backreaction of tachyon on dilaton and on metric.

scholarly journals One Observer Universe: A Geometric Interpretation of Speed of Light and Mass

2020 ◽  
Author(s):  
Ahmed Farag Ali
Keyword(s):  
General Relativity ◽  
Special Relativity ◽  
Geometric Interpretation ◽  
Space Time ◽  
Red Shift ◽  
General Covariance ◽  
Speed Of Light ◽  
The Universe

In this paper, we investigate how Rindler observer measures the universe in the ADM formalism. We compute his measurements in each slice of the space-time in terms of gravitational red-shift which is a property of general covariance. In this way, we found special relativity preferred frames to match with the general relativity Rindler frame in ADM formalism. This may resolve the widely known incompatibility between special relativity and general relativity on how each theory sees the red-shift. We found a geometric interpretation of the speed of light and mass.

scholarly journals w = 1/3 to w = −1 evolution in a Robertson–Walker space-time with constant scalar curvature

2019 ◽  
Vol 16 (04) ◽  
pp. 1950061 ◽  
Author(s):  
Luca Guido Molinari ◽  
Carlo Alberto Mantica
Keyword(s):  
Scalar Curvature ◽  
Ricci Tensor ◽  
Constant Scalar Curvature ◽  
Flat Space ◽  
Space Time ◽  
Spatial Curvature ◽  
Limit Values ◽  
Pure Radiation ◽  
Age Of The Universe ◽  
The Universe

The Ricci tensor of a Robertson–Walker (RW) space-time is here specified by requiring constancy of the scalar curvature and a vanishing spatial curvature. By entering this Ricci tensor in Einstein’s equations (without cosmological constant), the cosmological fluid shows a transition from a pure radiation to a Lambda equation of state. In other words, the RW geometry with constant scalar curvature and flat space fixes the limit values [Formula: see text] and [Formula: see text], without any hypothesis on the cosmological fluid. The value of the scalar curvature fixes the time-scale for the transition. For this reason, we investigate the ‘toy-universe’ with Hubble parameter [Formula: see text] and temperature [Formula: see text][Formula: see text]K. The model predicts an age of the universe in the range 7.3–13.7[Formula: see text]Gyr.

scholarly journals On duality of color and kinematics in (A)dS momentum space

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Soner Albayrak ◽  
Savan Kharel ◽  
David Meltzer
Keyword(s):  
Wave Function ◽  
Analytic Continuation ◽  
Momentum Space ◽  
Spectral Representation ◽  
Flat Space ◽  
Tree Level ◽  
De Sitter ◽  
Yang Mills ◽  
The Universe ◽  
Double Copy

Abstract We explore color-kinematic duality for tree-level AdS/CFT correlators in momentum space. We start by studying the bi-adjoint scalar in AdS at tree-level as an illustrative example. We follow this by investigating two forms of color-kinematic duality in Yang-Mills theory, the first for the integrated correlator in AdS4 and the second for the integrand in general AdSd+1. For the integrated correlator, we find color-kinematics does not yield additional relations among n-point, color-ordered correlators. To study color-kinematics for the AdSd+1 Yang-Mills integrand, we use a spectral representation of the bulk-to-bulk propagator so that AdS diagrams are similar in structure to their flat space counterparts. Finally, we study color KLT relations for the integrated correlator and double-copy relations for the AdS integrand. We find that double-copy in AdS naturally relates the bi-adjoint theory in AdSd+3 to Yang-Mills in AdSd+1. We also find a double-copy relation at three-points between Yang-Mills in AdSd+1 and gravity in AdSd−1 and comment on the higher-point generalization. By analytic continuation, these results on AdS/CFT correlators can be translated into statements about the wave function of the universe in de Sitter.

scholarly journals EXACT STRING SOLUTIONS IN (2 + 1)-DIMENSIONAL DE SITTER SPACE-TIME

1994 ◽  
Vol 09 (29) ◽  
pp. 2745-2754 ◽  
Author(s):  
H. J. DE VEGA ◽  
A. V. MIKHAILOV ◽  
N. SÁNCHEZ
Keyword(s):  
Flat Space ◽  
De Sitter Space ◽  
Space Time ◽  
The Other ◽  
De Sitter ◽  
Expansion Factor ◽  
New Feature ◽  
The Universe ◽  
Time Analogy

Exact and explicit string solutions in de Sitter space-time are found. (Here, the string equations reduce to a sinh-Gordon model). A new feature without flat space-time analogy appears: starting with a single worldsheet, several (here two) strings emerge. One string is stable and the other (unstable) grows as the universe grows. Their invariant size and energy either grow as the expansion factor or tend to constant. Moreover, strings can expand (contract) for large (small) universe radius at a different rate than the universe does.

NON-MINIMAL COUPLING, VARIABLE SPEED OF LIGHT AND COSMOLOGY

2002 ◽  
Vol 17 (20) ◽  
pp. 2777-2777
Author(s):  
P. TEYSSANDIER
Keyword(s):  
Dimensional Space ◽  
Flat Space ◽  
Space Time ◽  
Variable Speed ◽  
Speed Of Light ◽  
Field Equations ◽  
Minimal Coupling ◽  
Structural Constant ◽  
Dimensional Space Time ◽  
Photon Gas

Presently, there exists some renewed interest in time varying speed of light theories as possible solutions of the major cosmological problems1. It is often believed that the local Lorentzian invariance is broken if the speed of light in a vacuum is not a constant. We point out that this belief is not necessarily founded and that a variable speed of light is perfectly consistent with general relativity under the assumption of non-minimal coupling between electromagnetism and curvature. Two kinds of arguments may be invoked in favour of such an assumption. First, a theorem due to Horndeski2 shows that in a four-dimensional space-time the Einstein-Maxwell field equations are not the only second-order vector potential field equations which stem from a Lagrangian scalar density, are consistent with the charge conservation and reduce to Maxwell's equations in a flat space-time (see also3). Second, according to QED4,5, vacuum polarization induces tidal gravitational effects which imply that photons propagating in a curved space-time have velocities exceeding the value of the "Lorentzian structural constant" c. The modified electromagnetic field equations given by Horndeski2 are studied here in the geometrical optics limit. Considering the case of Friedmann-Robertson-Walker cosmological models, we find the value of the speed of light as a function of the energetic content of the universe. We deduce from this result a new equation of state for a photon gas and we discuss the consequences of this equation on the evolution of the scale factor during the radiation-dominated era.

scholarly journals THE ISSUE OF CHOOSING NOTHING: WHAT DETERMINES THE LOW ENERGY VACUUM STATE OF NATURE?

2000 ◽  
Vol 15 (29) ◽  
pp. 1813-1821 ◽  
Author(s):  
T. PADMANABHAN ◽  
T. ROY CHOUDHURY
Keyword(s):  
Wave Function ◽  
Vacuum State ◽  
Flat Space ◽  
Space Time ◽  
Low Energy ◽  
Approximate Theory ◽  
Volume Limit ◽  
Low Energies ◽  
Nonrelativistic Quantum Mechanics ◽  
The Universe

Starting from an (unknown) quantum gravitational model, one can invoke a sequence of approximations to progressively arrive at quantum field theory (QFT) in curved space–time, QFT in flat space–time, nonrelativistic quantum mechanics and Newtonian mechanics. The more exact theory can put restrictions on the range of possibilities allowed for the approximate theory which are not derivable from the latter — an example being the symmetry restrictions on the wave function for a pair of electrons. We argue that the choice of vacuum state at low energies could be such a "relic" arising from combining the principles of quantum theory and general relativity, and demonstrate this result in a simple toy model. Our analysis suggests that the wave function of the universe, when describing the large volume limit of the universe, dynamically selects a vacuum state for matter fields — which in turn defines the concept of particle in the low energy limit. The result also has the potential for providing a concrete quantum mechanical version of Mach's principle.

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.

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