scholarly journals Tensor perturbations and thick branes in higher-dimensional f(R) gravity

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Zheng-Quan Cui ◽  
Zi-Chao Lin ◽  
Jun-Jie Wan ◽  
Yu-Xiao Liu ◽  
Li Zhao
Keyword(s):  
Effective Potential ◽  
Higher Dimensions ◽  
Brane Worlds ◽  
Dimensional Spacetime ◽  
Higher Dimensional ◽  
Six Dimensions ◽  
Tensor Perturbations ◽  
Thick Branes ◽  
Kaluza Klein

Abstract We study brane worlds in an anisotropic higher-dimensional spacetime within the context of f(R) gravity. Firstly, we demonstrate that this spacetime with a concrete metric ansatz is stable against linear tensor perturbations under certain conditions. Moreover, the Kaluza-Klein modes of the graviton are analyzed. Secondly, we investigate thick brane solutions in six dimensions and their properties. We further exhibit two sets of solutions for thick branes. At last, the effective potential of the Kaluza-Klein modes of the graviton is discussed for the two solved f(R) models in higher dimensions.

scholarly journals Matter Localization on Brane-Worlds Generated by Deformed Defects

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Alex E. Bernardini ◽  
Roldão da Rocha
Keyword(s):  
Matter Field ◽  
Brane Worlds ◽  
Fermion Fields ◽  
Internal Structures ◽  
Global Action ◽  
Boson Fields ◽  
Mass Terms ◽  
Matter Fields ◽  
Thick Branes ◽  
Kaluza Klein

Localization and mass spectrum of bosonic and fermionic matter fields of some novel families of asymmetric thick brane configurations generated by deformed defects are investigated. The localization profiles of spin 0, spin 1/2, and spin 1 bulk fields are identified for novel matter field potentials supported by thick branes with internal structures. The condition for localization is constrained by the brane thickness of each model such that thickest branes strongly induce matter localization. The bulk mass terms for both fermion and boson fields are included in the global action as to produce some imprints on mass-independent potentials of the Kaluza-Klein modes associated with the corresponding Schrödinger equations. In particular, for spin 1/2 fermions, a complete analytical profile of localization is obtained for the four classes of superpotentials here discussed. Regarding the localization of fermion fields, our overall conclusion indicates that thick branes produce aleft-right asymmetric chirallocalization of spin 1/2 particles.

Conformal evolution of phantom dominated final stages of the universe in higher dimensions

2020 ◽  
pp. 1-9 ◽  
Author(s):  
S. Natarajan ◽  
R. Chandramohan
Keyword(s):  
Loop Quantum Gravity ◽  
Dimensional Space ◽  
Friedmann Equation ◽  
Higher Dimensions ◽  
Higher Dimensional ◽  
Loop Quantization ◽  
The Universe ◽  
Modified Equation ◽  
Work Loop ◽  
Kaluza Klein

Friedmann solutions and higher-dimensional 5D Kaluza–Klein solutions using mathematical packages such as Sagemath and Cadabra are calculated. A modified Friedmann equation powered by loop quantum gravity in higher dimensions is calculated in this work. Loop quantization in extra-dimensional space is predicted. Modified equation of state for non-interacting dark matter and dark energy are calculated. It has been predicted that the higher curvature due to phantom density would be a local kind of quantized curvature. The modified Friedmann solutions with Kaluza–Klein interpretation are found. To achieve a conformal exit, the non-interacting solutions are discussed in this work. The obtained results are compared with the ΛCDM and quintessence models. The results support conformal cyclic cosmology, which predicts the conformal evolution of the universe without facing any singularity as the result of topological effects.

scholarly journals The entropy sum of (A)dS black holes in four and higher dimensions

2014 ◽  
Vol 29 (30) ◽  
pp. 1450172 ◽  
Author(s):  
Wei Xu ◽  
Jia Wang ◽  
Xin-He Meng
Keyword(s):  
Black Holes ◽  
Angular Momentum ◽  
Cosmological Constant ◽  
Higher Dimensions ◽  
Coupling Constant ◽  
Bonnet Gravity ◽  
Charged Black Holes ◽  
Higher Dimensional ◽  
Six Dimensions ◽  
Odd Dimensions

We present the "entropy sum" relation of (A)dS charged black holes in higher-dimensional Einstein–Maxwell gravity, f(R) gravity, Gauss–Bonnet gravity and gauged supergravity. For their "entropy sum" with the necessary effect of the unphysical "virtual" horizon included, we conclude the general results that the cosmological constant dependence and Gauss–Bonnet coupling constant dependence do hold in both the four and six dimensions, while the "entropy sum" is always vanishing in odd dimensions. Furthermore, the "entropy sum" of all horizons is related to the geometry of the horizons in four and six dimensions. In these explicitly four cases, one also finds that the conserved charges M (the mass), Q (the charge from Maxwell field or supergravity) and the parameter a (the angular momentum) play no role in the "entropy sum" relations.

Collapsing solutions in higher-dimensional spacetime

2019 ◽  
Vol 28 (09) ◽  
pp. 1950117
Author(s):  
Hassan Shah ◽  
Zahid Ahmad ◽  
Suhail Khan
Keyword(s):  
Energy Density ◽  
Higher Dimensions ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Dimensional Spacetime ◽  
Higher Dimensional

We investigate higher-dimensional spherically symmetric anisotropic collapsing solutions of the field equations. Our aim is to check the effects of higher dimensions on the density and pressures profile of the collapsing fluid. It has been observed that the energy density, radial and tangential pressures of the collapsing system are strongly affected by higher dimensions. It also comes out that the anisotropy of the collapsing system becomes constant in higher dimensions.

scholarly journals Unitarity in KK-graviton production, a case study in warped extra-dimensions

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
A. de Giorgi ◽  
S. Vogl
Keyword(s):  
Extra Dimensions ◽  
Sum Rules ◽  
Effective Theory ◽  
Higher Dimensional ◽  
Massive Spin ◽  
The Matrix ◽  
Dimensional Gravity ◽  
Warped Extra Dimensions ◽  
Kaluza Klein

Abstract The Kaluza-Klein (KK) decomposition of higher-dimensional gravity gives rise to a tower of KK-gravitons in the effective four-dimensional (4D) theory. Such massive spin-2 fields are known to be connected with unitarity issues and easily lead to a breakdown of the effective theory well below the naive scale of the interaction. However, the breakdown of the effective 4D theory is expected to be controlled by the parameters of the 5D theory. Working in a simplified Randall-Sundrum model we study the matrix elements for matter annihilations into massive gravitons. We find that truncating the KK-tower leads to an early breakdown of perturbative unitarity. However, by considering the full tower we obtain a set of sum rules for the couplings between the different KK-fields that restore unitarity up to the scale of the 5D theory. We prove analytically that these are fulfilled in the model under consideration and present numerical tests of their convergence. This work complements earlier studies that focused on graviton self-interactions and yields additional sum rules that are required if matter fields are incorporated into warped extra-dimensions.

4D Einstein equations in a general gauge Kaluza–Klein space

2015 ◽  
Vol 12 (03) ◽  
pp. 1550036
Author(s):  
Aurel Bejancu ◽  
Constantin Călin
Keyword(s):  
Einstein Equations ◽  
Tensor Fields ◽  
New Approach ◽  
Higher Dimensional ◽  
High Level ◽  
General Gauge ◽  
Kaluza Klein

Using the new approach on higher-dimensional Kaluza–Klein theories developed by the first author, we obtain the 4D Einstein equations on a (4 + n)D relativistic gauge Kaluza–Klein space. Adapted frame and coframe fields, adapted tensor fields, and the Riemannian adapted connection, have a fundamental role in the study. The high level of generality of the study, enables us to recover several results from earlier papers on this matter.

scholarly journals GRAVITY-WAVE DETECTORS AS PROBES OF EXTRA DIMENSIONS

2005 ◽  
Vol 14 (12) ◽  
pp. 2347-2353 ◽  
Author(s):  
CHRIS CLARKSON ◽  
ROY MAARTENS
Keyword(s):  
Black Holes ◽  
String Theory ◽  
Gravity Wave ◽  
Gravity Waves ◽  
Extra Dimensions ◽  
State Of The Art ◽  
Three Dimensional ◽  
Observable Universe ◽  
Dimensional Spacetime ◽  
Higher Dimensional

If string theory is correct, then our observable universe may be a three-dimensional "brane" embedded in a higher-dimensional spacetime. This theoretical scenario should be tested via the state-of-the-art in gravitational experiments — the current and upcoming gravity-wave detectors. Indeed, the existence of extra dimensions leads to oscillations that leave a spectroscopic signature in the gravity-wave signal from black holes. The detectors that have been designed to confirm Einstein's prediction of gravity waves, can in principle also provide tests and constraints on string theory.

FERMION PERTURBATIONS IN HIGHER-DIMENSIONAL STRING-THEORY BLACK HOLES

2013 ◽  
Vol 22 (10) ◽  
pp. 1350073
Author(s):  
OWEN PAVEL FERNÁNDEZ PIEDRA ◽  
JOSE BERNAL CASTILLO ◽  
YULIER JIMENEZ SANTANA ◽  
LEOSDAN FIGUEREDO NORIS
Keyword(s):  
Black Hole ◽  
Damping Factor ◽  
Test Field ◽  
Perfect Agreement ◽  
Massless Fermion ◽  
Time Domain Data ◽  
Fermion Fields ◽  
Dimensional Spacetime ◽  
Higher Dimensional ◽  
The Time Domain

In this paper, we report the results of a detailed investigation of the complete time evolution of massless fermion fields propagating in spacetimes of higher-dimensional stringy black hole solutions, obtained from intersecting branes in string/M theory. We write the Dirac equation in D-dimensional spacetime in a form suitable to perform a numerical integration of it, and using a Prony fitting of the time domain data, we determine the quasinormal frequencies that characterize the test field evolution at intermediary times. We also present the results obtained for the quasinormal frequencies using a sixth-order WKB approximation, that are in perfect agreement with the numerical results. The power-law exponents that describe the field relaxation at very late-times are also determined, and we show that they depends upon the dimensionality of spacetime, and are identical to that associated with the relaxation of boson fields for odd dimensions. The dependence of the frequencies and damping factor of the spinor field with the charges of the stringy black hole are studied.

GRAVITATIONAL BAG EFFECTS ON KALUZA KLEIN AND STRING EXCITATIONS

1989 ◽  
Vol 04 (19) ◽  
pp. 5119-5131 ◽  
Author(s):  
E. I. GUENDELMAN
Keyword(s):  
Extra Dimensions ◽  
Blow Up ◽  
Point Of View ◽  
Spherically Symmetric ◽  
Massive String ◽  
Free Objects ◽  
Higher Dimensional ◽  
Central Regions ◽  
The Masses ◽  
Kaluza Klein

Gravitational Bags are spherically symmetric solutions of higher-dimensional Kaluza Klein (K – K) theories, where the compact dimensions become very large near the center of the geometry, although they are small elsewhere. The K – K excitations therefore become very light when located near the center of this geometry and this appears to affect drastically the naive tower of the masses spectrum of K – K theories. In the context of string theories, string excitations can be enclosed by Gravitational Bags, making them not only lighter, but also localized, as observed by somebody, that does not probe the central regions. Strings, however, can still have divergent sizes, as quantum mechanics seems to demand, since the extra dimensions blow up at the center of the geometry. From a projected 4-D point of view, very massive string bits may lie inside their Schwarzschild radii, as pointed out by Casher, Gravitational Bags however are horizon free objects, so no conflict with macroscopic causality arises if the string excitations are enclosed by Gravitational Bags.

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