Some exact solutions in Bianchi VI0 string cosmology

Pramana ◽  
1994 ◽  
Vol 42 (6) ◽  
pp. 483-489 ◽  
Author(s):  
Ramesh Tikekar ◽  
L K Patel
Keyword(s):  
Exact Solutions ◽  
String Cosmology

Exact Solutions for String Cosmology

2003 ◽  
Vol 20 (5) ◽  
pp. 615-617 ◽  
Author(s):  
Wang Xing-Xiang
Keyword(s):  
Exact Solutions ◽  
String Cosmology

scholarly journals Friedmann universes and exact solutions in string cosmology

1995 ◽  
Vol 12 (10) ◽  
pp. 2519-2524 ◽  
Author(s):  
S N Roshchupkin ◽  
A A Zheltukhin
Keyword(s):  
Exact Solutions ◽  
String Cosmology

SCALE FACTOR DUALITY AND GENERAL TRANSFORMATIONS FOR STRING COSMOLOGY

1993 ◽  
Vol 02 (03) ◽  
pp. 367-371 ◽  
Author(s):  
SALVATORE CAPOZZIELLO ◽  
RUGGIERO DE RITIS
Keyword(s):  
Exact Solutions ◽  
String Cosmology ◽  
Scale Factor ◽  
Point Of View ◽  
Tree Level ◽  
General Point ◽  
Effective Lagrangian ◽  
New System

We adopt a general point of view to obtain the scale factor duality for a class of nonminimally coupled gravitational Lagrangians which comprises the tree-level effective Lagrangian of string-dilaton cosmology. We show that in a new system of coordinates the duality is a reflection and the Lagrangians become cyclic with respect to a coordinate. When this is the situation, the dynamics is simplified and it is easier to obtain exact solutions.

String cosmology from fractional action with solitonic NS–NS matter and possibility of an accelerated expanding universe without dark energy

2021 ◽  
pp. 1-5
Author(s):  
Rami Ahmad El-Nabulsi
Keyword(s):  
Dark Energy ◽  
Exact Solutions ◽  
Vacuum Energy ◽  
String Cosmology ◽  
Accelerated Expansion ◽  
Fractional Action Cosmology ◽  
Dissipative Effects ◽  
Stationary Conditions ◽  
The Universe ◽  
Fractional Parameter

In this study, we discuss string cosmology with solitonic NS–NS matter, which arises when dilaton coupled p-brane gas dominates the universe and is subject to a fractional action motivated from viscosity dissipative effects occurring in the universe. Exact solutions are found from the stationary conditions of the fractional action. It was observed that the universe is non-singular, undergoing accelerated expansion in time and may not be dominated by dark energy because it is strongly affected by dissipations through the fractional parameter α. The numerical ranges of α were obtained using H(z) at the 1σ level for two independent cases: a vacuum energy dominated energy and a non-dominant vacuum energy universe. Our results are in agreement with astronomical observational limits and support both string cosmology and the fractional action cosmology.

Some exact solutions in string cosmology

1990 ◽  
Vol 22 (2) ◽  
pp. 123-130 ◽  
Author(s):  
K. D. Krori ◽  
T. Chaudhury ◽  
Chandra Rekha Mahanta ◽  
Ajanta Mazumdar
Keyword(s):  
Exact Solutions ◽  
String Cosmology
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