The de Donder coordinate condition and minimal class 1 space–time

1975 ◽  
Vol 16 (6) ◽  
pp. 1234-1236
Author(s):  
Jorge Krause
2021 ◽  
Vol 36 (02) ◽  
pp. 2150015
Author(s):  
Nayan Sarkar ◽  
Susmita Sarkar ◽  
Farook Rahaman ◽  
Safiqul Islam

The present work looks for new spherically symmetric wormhole solutions of the Einstein field equations based on the well-known embedding class 1, i.e. Karmarkar condition. The embedding theorems have an interesting property that connects an [Formula: see text]-dimensional space–time to the higher-dimensional Euclidean flat space–time. The Einstein field equations yield the wormhole solution by violating the null energy condition (NEC). Here, wormholes solutions are obtained corresponding to three different redshift functions: rational, logarithm, and inverse trigonometric functions, in embedding class 1 space–time. The obtained shape function in each case satisfies the flare-out condition after the throat radius, i.e. good enough to represents wormhole structure. In cases of WH1 and WH2, the solutions violate the NEC as well as strong energy condition (SEC), i.e. here the exotic matter content exists within the wormholes and strongly sustains wormhole structures. In the case of WH3, the solution violates NEC but satisfies SEC, so for violating the NEC wormhole preserve due to the presence of exotic matter. Moreover, WH1 and WH2 are asymptotically flat while WH3 is not asymptotically flat. So, indeed, WH3 cutoff after some radial distance [Formula: see text], the Schwarzschild radius, and match to the external vacuum solution.


2019 ◽  
Vol 97 (12) ◽  
pp. 1323-1331 ◽  
Author(s):  
S.K. Maurya ◽  
S. Roy Chowdhury ◽  
Saibal Ray ◽  
B. Dayanandan

In the present paper we study compact stars under the background of Einstein–Maxwell space–time, where the 4-dimensional spherically symmetric space–time of class 1 along with the Karmarkar condition has been adopted. The investigations, via the set of exact solutions, show several important results, such as (i) the value of density on the surface is finite; (ii) due to the presence of the electric field, the outer surface or the crust region can be considered to be made of electron cloud; (iii) the charge increases rapidly after crossing a certain cutoff region (r/R ≈ 0.3); and (iv) the avalanche of charge has a possible interaction with the particles that are away from the center. As the stellar structure supports all the physical tests performed on it, therefore the overall observation is that the model provides a physically viable and stable compact star.


1977 ◽  
Vol 8 (2) ◽  
pp. 147-153 ◽  
Author(s):  
S. N. Pandey ◽  
S. P. Sharma

2010 ◽  
Vol 25 (09) ◽  
pp. 1863-1879 ◽  
Author(s):  
Y. K. GUPTA ◽  
PRATIBHA ◽  
SACHIN KUMAR

In view of renewed interest in the space–time embedded in higher-dimensional flat space which are useful in extrinsic gravity, string and brane theory, a set of six explicit solutions to Einstein's field equations for nonconformally flat accelerating and shearing perfect fluid plates is obtained using similarity transformations method by considering a five-dimensional flat metric. All the solutions thus obtained are analyzed physically. All the solutions are new in their respective category as far as authors are aware.


2002 ◽  
Author(s):  
J. B. Kennedy
Keyword(s):  

2019 ◽  
Vol 24 (5) ◽  
pp. 14-15
Author(s):  
Jay Blaisdell ◽  
James B. Talmage

Abstract Ratings for “non-specific chronic, or chronic reoccurring, back pain” are based on the diagnosis-based impairment method whereby an impairment class, usually representing a range of impairment values within a cell of a grid, is selected by diagnosis and “specific criteria” (key factors). Within the impairment class, the default impairment value then can be modified using non-key factors or “grade modifiers” such as functional history, physical examination, and clinical studies using the net adjustment formula. The diagnosis of “nonspecific chronic, or chronic reoccurring, back pain” can be rated in class 0 and 1; the former has a default value of 0%, and the latter has a default value of 2% before any modifications. The key concept here is that the physician believes that the patient is experiencing pain, yet there are no related objective findings, most notably radiculopathy as distinguished from “nonverifiable radicular complaints.” If the individual is found not to have radiculopathy and the medical record shows that the patient has never had clinically verifiable radiculopathy, then the diagnosis of “intervertebral disk herniation and/or AOMSI [alteration of motion segment integrity] cannot be used.” If the patient is asymptomatic at maximum medical improvement, then impairment Class 0 should be chosen, not Class 1; a final whole person impairment rating of 1% indicates incorrect use of the methodology.


Author(s):  
Roger Penrose ◽  
Wolfgang Rindler
Keyword(s):  

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