scholarly journals Two-Body Orbit Expansion Due to Time-Dependent Relative Acceleration Rate of the Cosmological Scale Factor

Galaxies ◽  
2014 ◽  
Vol 2 (1) ◽  
pp. 13-21 ◽  
Author(s):  
Lorenzo Iorio
Keyword(s):  
Scale Factor ◽  
Time Dependent ◽  
Cosmological Scale ◽  
Relative Acceleration ◽  
Acceleration Rate

Parametrization of the cosmological scale factor

1994 ◽  
Vol 33 (10) ◽  
pp. 2099-2117 ◽  
Author(s):  
Renee R. Wahba ◽  
Larry L. Smalley ◽  
Alphonsus J. Fennelly
Keyword(s):  
Scale Factor ◽  
Cosmological Scale

scholarly journals VARIABLE CHAPLYGIN GAS: CONSTRAINTS FROM CMBR ANDSNe Ia

2006 ◽  
Vol 15 (07) ◽  
pp. 1089-1098 ◽  
Author(s):  
GEETANJALI SETHI ◽  
SUSHIL K. SINGH ◽  
PRANAV KUMAR ◽  
DEEPAK JAIN ◽  
ABHA DEV
Keyword(s):  
Equation Of State ◽  
Positive Function ◽  
Chaplygin Gas ◽  
Scale Factor ◽  
Type Ia Supernovae ◽  
Data Set ◽  
Cosmological Scale ◽  
Type Ia ◽  
Ia Supernovae

We constrain the parameters of the variable Chaplygin gas model, using the location of peaks of the CMBR spectrum and the SNe Ia "gold" data set. The equation of state of the model is P = -A(a)/ρ, where A(a) = A0a-nis a positive function of the cosmological scale factor a, A0and n> being constants. The variable Chaplygin gas interpolates from the dust-dominated era to the quintessence dominated era. The model is found to be compatible with current type Ia supernovae data and the location of the first peak if the values of Ωmand n lie in the interval [0.017, 0.117] and [-1.3, 2.6], respectively.

scholarly journals RESTORING TIME DEPENDENCE INTO QUANTUM COSMOLOGY

2012 ◽  
Vol 21 (11) ◽  
pp. 1242011 ◽  
Author(s):  
AHARON DAVIDSON ◽  
BEN YELLIN
Keyword(s):  
Quantum Theory ◽  
Time Dependence ◽  
Quantum Cosmology ◽  
Scale Factor ◽  
Time Dependent ◽  
Hamiltonian Constraint ◽  
Canonical Variables ◽  
Explicit Time Dependence ◽  
Dirac Brackets ◽  
Lapse Function

Mini superspace cosmology treats the scale factor a(t), the lapse function n(t) and an optional dilation field ϕ(t) as canonical variables. While pre-fixing n(t) means losing the Hamiltonian constraint, pre-fixing a(t) is serendipitously harmless at this level. This suggests an alternative to the Hartle–Hawking approach, where the pre-fixed a(t) and its derivatives are treated as explicit functions of time, leaving n(t) and a now mandatory ϕ(t) to serve as canonical variables. The naive gauge pre-fix a(t) = const . is clearly forbidden, causing evolution to freeze altogether; so pre-fixing the scale factor, say a(t) = t, necessarily introduces explicit time dependence into the Lagrangian. Invoking Dirac's prescription for dealing with constraints, we construct the corresponding mini superspace time-dependent total Hamiltonian and calculate the Dirac brackets, characterized by {n, ϕ}D ≠ 0, which are promoted to commutation relations in the quantum theory.

scholarly journals Numerical methods for the determination of mixing

2003 ◽  
Vol 21 (3) ◽  
pp. 437-442 ◽  
Author(s):  
E. GEORGE ◽  
J. GLIMM ◽  
X.L. LI ◽  
A. MARCHESE ◽  
Z.-L. XU ◽  
...  
Keyword(s):  
Buoyancy Force ◽  
Rate Coefficient ◽  
Front Tracking ◽  
Mass Diffusion ◽  
Time Dependent ◽  
Mixing Rate ◽  
Quantitative Evidence ◽  
Front Tracking Method ◽  
Acceleration Rate

We present a Rayleigh–Taylor mixing rate simulation with an acceleration rate falling within the range of experiments. The simulation uses front tracking to prevent interfacial mass diffusion. We present evidence to support the assertion that the lower acceleration rate found in untracked simulations is caused, at least to a large extent, by a reduced buoyancy force due to numerical interfacial mass diffusion. Quantitative evidence includes results from a time-dependent Atwood number analysis of the diffusive simulation, which yields a renormalized mixing rate coefficient for the diffusive simulation in agreement with experiment. We also present the study of Richtmyer–Meshkov mixing in cylindrical geometry using the front tracking method and compare it with the experimental results.

TIME-DEPENDENT SOLUTIONS OF 5D VACUUM EINSTEIN EQUATIONS WITH COSMOLOGICAL CONSTANT

2011 ◽  
Vol 26 (22) ◽  
pp. 1673-1679 ◽  
Author(s):  
TAE HOON LEE
Keyword(s):  
Cosmological Constant ◽  
Time Dependence ◽  
Scale Factor ◽  
Einstein Equations ◽  
Time Dependent ◽  
Vacuum Field ◽  
Field Equations ◽  
Vacuum Einstein Equations ◽  
Dimensional Gravity

We solve vacuum field equations in five-dimensional gravity with cosmological constant to determine the time-dependence of the Robertson–Walker scale factor. We discuss its cosmological implications.

scholarly journals INVARIANTS AND SOLUTIONS OF GURZADYAN–XUE DARK ENERGY COSMOLOGICAL MODELS

2007 ◽  
Vol 22 (05) ◽  
pp. 333-338 ◽  
Author(s):  
H. G. KHACHATRYAN
Keyword(s):  
Dark Energy ◽  
Time Evolution ◽  
Gravitational Constant ◽  
Scale Factor ◽  
Cosmological Models ◽  
Time Dependent ◽  
Speed Of Light ◽  
Light Speed ◽  
Hidden Symmetry ◽  
Cosmological Expansion

We have derived the invariants of cosmological models with Gurzadyan–Xue (GX) dark energy, along with the solutions for any time-dependent light speed and gravitational constant. The correspondence of the invariants with the separatrices found earlier for the GX-models is shown, and hence the basis of then detected hidden symmetry is now revealed. Solutions are derived both for radiation and matter models, as well as with both components. It is interesting that, the solutions for the scale factor do not depend on the gravitational constant but only on the "time evolution" of the speed of light. GX-invariants act as efficient tools describing the models and the phases of the cosmological expansion.

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