scholarly journals Two theorems on flat space-time gravitational theories

1980 ◽  
Vol 12 (10) ◽  
pp. 825-835
Author(s):  
Mario Castagnino ◽  
Luis Chimento
Keyword(s):  
Flat Space ◽  
Space Time ◽  
Gravitational Theories

Tensorial rank of gravitational theories in flat space-time

1983 ◽  
Vol 75 (1) ◽  
pp. 50-56 ◽  
Author(s):  
G. Cavalleri ◽  
G. Spinelli
Keyword(s):  
Flat Space ◽  
Space Time ◽  
Gravitational Theories

scholarly journals Energy Conditions of Built-In Inflation Models inf(T)Gravitational Theories

2015 ◽  
Vol 2015 ◽  
pp. 1-10
Author(s):  
Gamal G. L. Nashed
Keyword(s):  
Flat Space ◽  
Space Time ◽  
Energy Conditions ◽  
Frw Universe ◽  
Open Universe ◽  
Gravitational Theories ◽  
Friedmann Robertson Walker

We examine the validity of energy conditions of built-in inflation models inf(T)gravitational theories. For this purpose, we formulate the inequalities of energy conditions by assuming the flat and nonflat Friedmann-Robertson-Walker (FRW) universe. We find the feasible constraints on the constants of integration and evaluate their possible ranges graphically for the consistency of these energy conditions for flat, closed, and open universes. We constrain the constants of integration for flat space-time from the inflation epoch while the closed and open universe constants are constrained from late universe.

scholarly journals Flat Space-Time and Gravitation

1944 ◽  
Vol 30 (10) ◽  
pp. 324-334 ◽  
Author(s):  
G. D. Birkhoff
Keyword(s):  
Flat Space ◽  
Space Time

scholarly journals Evolution of a domain wall in expanding universe: inflation and after it

2018 ◽  
Vol 191 ◽  
pp. 08004
Author(s):  
A.D. Dolgov ◽  
S.I. Godunov ◽  
A.S. Rudenko
Keyword(s):  
Domain Wall ◽  
Hubble Parameter ◽  
Domain Walls ◽  
Flat Space ◽  
Space Time ◽  
Time Dependent ◽  
Expanding Universe ◽  
Large Size ◽  
Dependent Parameter ◽  
Thick Domain Walls

We study the evolution of thick domain walls in the expanding universe. We have found that the domain wall evolution crucially depends on the time-dependent parameter C(t) = 1/(H(t)δ0)2, where H(t) is the Hubble parameter and δ0 is the width of the wall in flat space-time. For C(t) > 2 the physical width of the wall, a(t)δ(t), tends with time to constant value δ0, which is microscopically small. Otherwise, when C(t) ≤ 2, the wall steadily expands and can grow up to a cosmologically large size.

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