scholarly journals Fourth order deformed general relativity

2014 ◽  
Vol 90 (10) ◽  
Author(s):  
Rhiannon Cuttell ◽  
Mairi Sakellariadou
Keyword(s):  
General Relativity ◽  
Fourth Order

scholarly journals Wormhole geometries in fourth-order conformal Weyl gravity

2016 ◽  
Vol 25 (06) ◽  
pp. 1650064 ◽  
Author(s):  
Gabriele U. Varieschi ◽  
Kellie L. Ault
Keyword(s):  
General Relativity ◽  
Fourth Order ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Energy Conditions ◽  
Conformal Gravity ◽  
Flat Spacetime ◽  
Traversable Wormholes ◽  
Weyl Gravity ◽  
The Subject

We present an analysis of the classic wormhole geometries based on conformal Weyl gravity, rather than standard general relativity. The main characteristics of the resulting traversable wormholes remains the same as in the seminal study by Morris and Thorne, namely, that effective super-luminal motion is a viable consequence of the metric. Improving on previous work on the subject, we show that for particular choices of the shape and redshift functions the wormhole metric in the context of conformal gravity does not violate the main energy conditions at or near the wormhole throat. Some exotic matter might still be needed at the junction between our solutions and flat spacetime, but we demonstrate that the averaged null energy condition (as evaluated along radial null geodesics) is satisfied for a particular set of wormhole geometries. Therefore, if fourth-order conformal Weyl gravity is a correct extension of general relativity, traversable wormholes might become a realistic solution for interstellar travel.

FOURTH-ORDER TOPOLOGICAL TENSOR CURRENT AND FOCK'S COORDINATE CONDITION

1998 ◽  
Vol 13 (10) ◽  
pp. 745-752 ◽  
Author(s):  
GUOHONG YANG ◽  
YISHI DUAN
Keyword(s):  
General Relativity ◽  
Fourth Order ◽  
Mapping Method ◽  
Coordinate Condition ◽  
Tensor Current ◽  
Special Case ◽  
Topological Tensor ◽  
Singular Manifolds

From ϕ-mapping method we construct a fouth-order topological tensor current in general. It is shown that the inner structure of this topological tensor current is labelled by the δ-function δ(ϕ), which represents some four-dimensional singular manifolds. By investigating the total expansion of δ(ϕ), these singular manifolds carry the topological numbers βiηi naturally, which does not involve any concrete models. As the generalization of Nielsen's Lagrangian and Nambu's action for strings, we present a new coordinate condition in general relativity, which includes the Fock's coordinate condition as a special case.

Children’s Recall of Approximations to English

1973 ◽  
Vol 16 (2) ◽  
pp. 201-212 ◽  
Author(s):  
Elizabeth Carrow ◽  
Michael Mauldin
Keyword(s):  
Language Development ◽  
Fourth Order ◽  
Third Order ◽  
Memory Processes ◽  
The Third ◽  
General Index ◽  
General Linguistic

As a general index of language development, the recall of first through fourth order approximations to English was examined in four, five, six, and seven year olds and adults. Data suggested that recall improved with age, and increases in approximation to English were accompanied by increases in recall for six and seven year olds and adults. Recall improved for four and five year olds through the third order but declined at the fourth. The latter finding was attributed to deficits in semantic structures and memory processes in four and five year olds. The former finding was interpreted as an index of the development of general linguistic processes.

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