scholarly journals Schwarzschild-like Wormholes in Asymptotically Safe Gravity

Universe ◽  
2021 ◽  
Vol 7 (9) ◽  
pp. 332
Author(s):  
Geová Alencar ◽  
Matheus Nilton

In this paper, we analyze the Schwarzschild-like wormhole in the Asymptotically Safe Gravity(ASG) scenario. The ASG corrections are implemented via renormalization group methods, which, as consequence, provides a new tensor Xμν as a source to improved field equations, and promotes the Newton’s constant into a running coupling constant. In particular, we check whether the radial energy conditions are satisfied and compare with the results obtained from the usual theory. We show that only in the particular case of the wormhole being asymptotically flat(Schwarzschild Wormholes) that the radial energy conditions are satisfied at the throat, depending on the chosen values for its radius r0. In contrast, in the general Schwarzschild-like case, there is no possibility of the energy conditions being satisfied nearby the throat, as in the usual case. After that, we calculate the radial state parameter, ω(r), in r0, in order to verify what type of cosmologic matter is allowed at the wormhole throat, and we show that in both cases there is the possibility of the presence of exotic matter, phantom or quintessence-like matter. Finally, we give the ω(r) solutions for all regions of space. Interestingly, we find that Schwarzschild-like Wormholes with excess of solid angle of the sphere in the asymptotic limit have the possibility of having non-exotic matter as source for certain values of the radial coordinate r. Furthermore, it was observed that quantum gravity corrections due the ASG necessarily imply regions with phantom-like matter, both for Schwarzschild and for Schwarzschild-like wormholes. This reinforces the supposition that a phantom fluid is always present for wormholes in this context.

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 238
Author(s):  
G. Alencar ◽  
V. B. Bezerra ◽  
C. R. Muniz ◽  
H. S. Vieira

In this paper, we investigate the simplest wormhole solution—the Ellis–Bronnikov one—in the context of the asymptotically safe gravity (ASG) at the Planck scale. We work with three models, which employ the Ricci scalar, Kretschmann scalar, and squared Ricci tensor to improve the field equations by turning the Newton constant into a running coupling constant. For all the cases, we check the radial energy conditions of the wormhole solution and compare them with those that are valid in general relativity (GR). We verified that asymptotic safety guarantees that the Ellis–Bronnikov wormhole can satisfy the radial energy conditions at the throat radius, r0, within an interval of values of the latter, which is quite different from the result found in GR. Following this, we evaluate the effective radial state parameter, ω(r), at r0, showing that the quantum gravitational effects modify Einstein’s field equations in such a way that it is necessary to have a very exotic source of matter to generate the wormhole spacetime–phantom or quintessence-like matter. This occurs within some ranges of the throat radii, even though the energy conditions are or are not violated there. Finally, we find that, although at r0 we have a quintessence-like matter, upon growing r, we inevitably came across phantom-like regions. We speculate whether such a phantom fluid must always be present in wormholes in the ASG context or even in more general quantum gravity scenarios.


2019 ◽  
Vol 16 (03) ◽  
pp. 1950046 ◽  
Author(s):  
M. Zubair ◽  
Rabia Saleem ◽  
Yasir Ahmad ◽  
G. Abbas

This paper is aimed to evaluate the existence of wormholes in viable [Formula: see text] gravity models (where [Formula: see text] is the scalar curvature and [Formula: see text] is the trace of stress–energy tensor of matter). The exact solutions for energy–momentum tensor components depending on different shapes and redshift functions are calculated without some additional constraints. To investigate this, we consider static spherically symmetric geometry with matter contents as anisotropic fluid and formulate the Einstein field equations for three different [Formula: see text] models. For each model, we derive expression for weak and null energy conditions and graphically analyzed its violation near the throat. It is really interesting that wormhole solutions do not require the presence of exotic matter — like that in general relativity. Finally, the stability of the solutions for each model is presented using equilibrium condition.


1995 ◽  
Vol 10 (06) ◽  
pp. 525-537 ◽  
Author(s):  
IGOR PESANDO

We consider the (massive) Gross–Neveu model using the light-cone quantization where we solve the constraints explicitly. We show that the vacuum is trivial and that the quantization fails when m = 0. We show that the running coupling constant emerges as a pure normal ordering effect and we discuss the bound state equation.


1989 ◽  
Vol 04 (20) ◽  
pp. 5575-5585 ◽  
Author(s):  
S. N. BANERJEE ◽  
BALLARI CHAKRABARTI ◽  
A. K. SARKER

The spectroscopic properties of the charmonium (Ψ) and bottomium (ϒ) families have been studied in the framework of the statistical model. The energy splittings of the S, P, D levels of Ψ and ϒ-families have been investigated using one-gluon exchange potential containing the running coupling constant, as a perturbation over the already existing confinement type of potentials. Our computed results are found to be in reasonably good agreement with the corresponding experimental findings and/or other theoretical estimates.


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