Conformal (2 + 4)-braneworld

2017 ◽  
Vol 26 (11) ◽  
pp. 1750125
Author(s):  
Merab Gogberashvili
Keyword(s):  
Geometrical Structure ◽  
Conformal Group ◽  
Effective Dimension ◽  
Brane Model ◽  
Embedding Theory ◽  
Fifth Dimension ◽  
The Stability ◽  
Simply Connected ◽  
Additional Reduction ◽  
Matter Fields

The 6D brane model is considered, where matter is trapped on the surface of a (2+4)-hyperboloid, as is suggested by the geometrical structure behind the 4D conformal group. The effective dimension of the bulk spacetime for matter fields is five, with the extra space-like and time-like domains. Using the embedding theory, the presence of the familiar factorizable 5D brane metrics in both domains is shown. These metrics with exponential warp factors are able to provide with the additional reduction of the effective spacetime dimensions down to four. It is demonstrated that the extra (1+1)-space is not simply connected and there is a gap in the range of the extra coordinates. This can explain the stability of the model in the domain with the time-like effective fifth dimension and the appearance of the cosmological constant due to the tachyon condensation. It is found that the model exhibits orbifold symmetry and thus is free from the fermion chirality problem.

Stability of charged rotating (2 + 1)-dimensional wormholes

2020 ◽  
Vol 29 (01) ◽  
pp. 2050007 ◽  
Author(s):  
M. Sharif ◽  
Faisal Javed
Keyword(s):  
Thin Shell ◽  
Geometrical Structure ◽  
Energy Tensor ◽  
Exterior Region ◽  
Barotropic Fluid ◽  
Linearized Stability ◽  
Stress Energy ◽  
Thin Shell Wormholes ◽  
The Stability ◽  
Fast Rotating

This paper investigates the effects of charge on linearized stability of rotating thin-shell wormholes (WHs) filled with a barotropic fluid. We use Visser cut and paste technique to construct thin-shell from charged rotating Bañados–Teitelboim–Zanelli (BTZ) black holes (BHs). The components of stress-energy tensor are evaluated through Israel thin-shell formalism. The angular momentum for both interior as well as exterior region at the WH throat remains the same but opposite in direction, i.e. thin-shell WH at the throat is counter-rotated. It is found that the geometrical structure of WHs is more stable for highly charged and fast rotating thin-shell. We conclude that the stability regions of charged rotating WHs are larger than the uncharged rotating WHs.

scholarly journals Thick branes in the scalar–tensor representation of f(R, T) gravity

2021 ◽  
Vol 81 (11) ◽  
Author(s):  
João Luís Rosa ◽  
Matheus A. Marques ◽  
Dionisio Bazeia ◽  
Francisco S. N. Lobo
Keyword(s):  
Scalar Field ◽  
Matter Field ◽  
Energy Tensor ◽  
Tensor Representation ◽  
Observable Universe ◽  
Brane Model ◽  
Gravitational Fields ◽  
Stress Energy ◽  
Tensor Representations ◽  
The Stability

AbstractBraneworld scenarios consider our observable universe as a brane embedded in a five-dimensional bulk. In this work, we consider thick braneworld systems in the recently proposed dynamically equivalent scalar–tensor representation of f(R, T) gravity, where R is the Ricci scalar and T the trace of the stress–energy tensor. In the general $$f\left( R,T\right) $$ f R , T case we consider two different models: a brane model without matter fields where the geometry is supported solely by the gravitational fields, and a second model where matter is described by a scalar field with a potential. The particular cases for which the function $$f\left( R,T\right) $$ f R , T is separable in the forms $$F\left( R\right) +T$$ F R + T and $$R+G\left( T\right) $$ R + G T , which give rise to scalar–tensor representations with a single auxiliary scalar field, are studied separately. The stability of the gravitational sector is investigated and the models are shown to be stable against small perturbations of the metric. Furthermore, we show that in the $$f\left( R,T\right) $$ f R , T model in the presence of an extra matter field, the shape of the graviton zero-mode develops internal structure under appropriate choices of the parameters of the model.

scholarly journals THE GAUGE HIERARCHY PROBLEM AND HIGHER-DIMENSIONAL GAUGE THEORIES

1998 ◽  
Vol 13 (32) ◽  
pp. 2601-2611 ◽  
Author(s):  
HISAKI HATANAKA ◽  
TAKEO INAMI ◽  
C. S. LIM
Keyword(s):  
Higgs Mass ◽  
Quantum Correction ◽  
Gauge Theories ◽  
Finite Mass ◽  
Hierarchy Problem ◽  
Mass Correction ◽  
Higher Dimensional ◽  
Gauge Hierarchy ◽  
Simply Connected ◽  
Matter Fields

We report on an attempt to solve the gauge hierarchy problem in the framework of higher-dimensional gauge theories. Both classical Higgs mass and quadratically divergent quantum correction to the mass are argued to be vanished. Hence the hierarchy problem in its original sense is solved. The remaining finite mass correction is shown to depend crucially on the choice of boundary condition for matter fields, and a way to fix it dynamically is presented. We also point out that on the simply-connected space S2 even the finite mass correction vanishes.

scholarly journals DE SITTER COSMOLOGY FROM GAUSS–BONNET DARK ENERGY WITH QUANTUM EFFECTS

2008 ◽  
Vol 17 (11) ◽  
pp. 2159-2170 ◽  
Author(s):  
EMILIO ELIZALDE ◽  
JOHN QUIROGA HURTADO ◽  
HÉCTOR IVÁN ARCOS
Keyword(s):  
Dark Energy ◽  
Correction Term ◽  
Quantum Effects ◽  
Classical Case ◽  
De Sitter ◽  
Quantum Anomaly ◽  
The Stability ◽  
M Theory ◽  
Friedmann Robertson Walker ◽  
Matter Fields

A Gauss–Bonnet dark energy model is considered. It is inspired by string/M-theory and also takes into account quantum contributions, which are introduced from a conformal quantum anomaly. The corresponding solutions for the Hubble rate, H, are studied starting from the Friedmann–Robertson–Walker equation. It is seen that, as a pure effect of the quantum contributions, a new solution for H exists in some region, which does not appear in the classical case. The behavior of all encountered solutions is studied with care, in particular the role played by the quantum correction term — which depends on the number of matter fields — in the stability of the solutions around its asymptotic value. It is argued that, contrary to what happens in the classical case, quantum effects remarkably lead to the realization of a de Sitter stage which corresponds to the inflation/dark energy stages, even for positive values of the f0 constant (coupling of the field with the Gauss–Bonnet invariant).

scholarly journals Methods for Numerical Modeling of Two-Dimensional Capillary Surfaces

2004 ◽  
Vol 4 (1) ◽  
pp. 66-93 ◽  
Author(s):  
Victor K. Polevikov
Keyword(s):  
Magnetic Field ◽  
Physical Phenomenon ◽  
Iterative Algorithms ◽  
Axially Symmetric ◽  
Capillary Surface ◽  
Capillary Surfaces ◽  
Equilibrium Shapes ◽  
Grid Nodes ◽  
The Stability ◽  
Simply Connected

Abstract Certain methods for numerical solving plane and axially symmetric problems on equilibrium shapes of a capillary surface are presented. The methods possess a high order of approximation on a nonuniform grid. They are easy to realize, fairly universal and suitable for constructing not only simply connected but also doubly connected and disconnected surfaces, including strongly curved ones. It is shown that the iterative algorithms constructed are absolutely stable at each iteration. The condition for convergence of iterations is obtained within the framework of a linear theory. To describe peak-shaped configurations of a magnetic uid in a high magnetic field, an algorithm of generation of adaptive grid nodes in accordance with the surface curvature is proposed. The methods have been tested for the well-known problems of capillary hydrostatics on equilibrium shapes of a drop adjacent to the horizontal rotating plate under gravity, and of an isolated magneticuid drop in a high uniform magnetic field. It has been established that they adequately respond to the physical phenomenon of a crisis of equilibrium shapes, i.e., they can be adopted to investigate the stability of equilibrium states of a capillary surface.

scholarly journals On the formality and strong Lefschetz property of symplectic manifolds – Erratum

2009 ◽  
Vol 147 (1) ◽  
pp. 255-255
Author(s):  
Taek Kyu Hwang ◽  
Jin Hong Kim
Keyword(s):  
Fundamental Group ◽  
Symplectic Manifold ◽  
Symplectic Manifolds ◽  
Finite Covering ◽  
Massey Product ◽  
Lefschetz Property ◽  
The Stability ◽  
Simply Connected ◽  
Open Question ◽  
Strong Lefschetz Property

Professor Vicente Muñoz kindly informed us that there is an inaccuracy in Lemma 3.5 of [1]. The correct statement of Lemma 3.5 is now that the fundamental group π1(X′) of the manifold X′ is Z, since the monodromy coming from φ8 does not imply that g4 = g4−1. Therefore, what we have actually constructed in Section 3 of [1] is a closed non-formal 8-dimensional symplectic manifold with π1 = Z whose triple Massey product is non-zero, so that the simply-connectedness in Theorem 1.1 should be dropped. As far as we know, the existence of a simply connected closed non-formal 8-dimensional symplectic manifold whose triple Massey product is non-zero still remains an open question. All other main results, especially Theorem 1.2 and Corollary 1.3, in [1] are not affected by this mistake. Furthermore, the stability of the non-formality under a finite covering as in Subsection 3.3 holds in general. We want to thank Professor Muñoz for his careful reading.

scholarly journals Note on Dolbeault cohomology and Hodge structures up to bimeromorphisms

2020 ◽  
Vol 7 (1) ◽  
pp. 194-214
Author(s):  
Daniele Angella ◽  
Tatsuo Suwa ◽  
Nicoletta Tardini ◽  
Adriano Tomassini
Keyword(s):  
Complex Manifold ◽  
Compact Complex Manifold ◽  
Complex Manifolds ◽  
Dolbeault Cohomology ◽  
Hodge Structures ◽  
Balanced Metric ◽  
The Stability ◽  
Cech Cohomology ◽  
Simply Connected ◽  
Compact Complex Manifolds

AbstractWe construct a simply-connected compact complex non-Kähler manifold satisfying the ∂ ̅∂ -Lemma, and endowed with a balanced metric. To this aim, we were initially aimed at investigating the stability of the property of satisfying the ∂ ̅∂-Lemma under modifications of compact complex manifolds and orbifolds. This question has been recently addressed and answered in [34, 39, 40, 50] with different techniques. Here, we provide a different approach using Čech cohomology theory to study the Dolbeault cohomology of the blowup ̃XZ of a compact complex manifold X along a submanifold Z admitting a holomorphically contractible neighbourhood.

Design Parameters for an Optimized Flame/Furnace Infrared Emission (FIRE) Radiometer

1993 ◽  
Vol 47 (12) ◽  
pp. 2072-2080 ◽  
Author(s):  
Kenneth W. Busch ◽  
Marianna A. Busch ◽  
Renaud Mercier Ythier ◽  
Arvie J. Kuehn
Keyword(s):  
Signal To Noise Ratio ◽  
Modulation Frequency ◽  
Infrared Emission ◽  
Design Parameters ◽  
Experimental Conditions ◽  
Flame Furnace ◽  
Spectral Bandpass ◽  
The Stability ◽  
Additional Reduction ◽  
Maximum Signal

Several design aspects of an optimized flame/furnace infrared emission (FIRE) radiometer are discussed. For a source in thermal equilibrium, the optimum excitation temperature for CO2 is predicted to be 2500 K, based on the stability of the molecule and the population of excited states as functions of temperature. The influence of spectral bandpass on the magnitude of flame background was studied for several wavelengths within the profile of the 4.4-µm emission band of CO2. For the dispersive FIRE radiometer used in this study, the system was found to be detectornoise limited over the range of spectral bandwidths accessible by the instrument (0.01–0.08 µm). When a hydrogen/air flame was used as the excitation source, the maximum signal-to-background ratio was obtained at 4.40 µm with a spectral bandpass of 0.08 µm. For this same experimental arrangement, a mathematical model was used to predict that the maximum signal-to-noise ratio would occur at 4.40 µm with a spectral bandpass of about 0.25 µm. The influence of chopping frequency on detector noise was determined for two different types of wavelength isolation. When a room-temperature bandpass filter was employed, a modulation frequency of 600–1000 Hz was satisfactory for avoiding 1/ f noise from the PbSe detector. However, when a monochromator was employed, chopping frequencies beyond 1000 Hz produced some additional reduction in 1/ f noise. The specific detectivity for the PbSe detector (6.2 × 108 cm Hz0.5 W−1), calculated from the measured noise at a modulation frequency of 600 Hz, is in good agreement with values reported in the literature for 4.40 µm under the same experimental conditions.

scholarly journals FOUR DIMENSIONALITY IN NON-COMPACT KALUZA–KLEIN MODEL

1999 ◽  
Vol 14 (29) ◽  
pp. 2025-2031 ◽  
Author(s):  
MERAB GOGBERASHVILI
Keyword(s):  
Dimensional Model ◽  
Einstein’S Equations ◽  
Einstein's Equations ◽  
Five Dimensional Model ◽  
The Stability ◽  
Klein Model ◽  
Matter Fields ◽  
Kaluza Klein

Five-dimensional model with extended dimensions investigated. It is shown that four dimensionality of our world is the result of the stability requirement. Extra component of five-dimensional Einstein's equations that is responsible for trapping of matter fields coincides with the condition of stability.

Cellular automaton approach to electromagnetic wave propagation in dispersive media

2006 ◽  
Vol 462 (2074) ◽  
pp. 2927-2948 ◽  
Author(s):  
M.W Janowicz ◽  
J.M.A Ashbourn ◽  
Arkadiusz Orłowski ◽  
Jan Mostowski
Keyword(s):  
Cellular Automaton ◽  
Dispersive Media ◽  
One Dimensional ◽  
Linear Partial Differential Equations ◽  
Left Handed ◽  
Split Operator ◽  
Lossy Dielectrics ◽  
The Stability ◽  
The One ◽  
Matter Fields

Extensions of Białynicki-Birula's cellular automaton are proposed for studies of the one-dimensional propagation of electromagnetic fields in Drude metals, as well as in both transparent, dispersive and lossy dielectrics. These extensions are obtained by representing the dielectrics with appropriate matter fields, such as polarization together with associated velocity fields. To obtain the different schemes for the integration of the resulting systems of linear partial differential equations, split-operator ideas are employed. Possible further extensions to two-dimensional propagation and for the study of left-handed materials are discussed. The stability properties of the cellular automaton treated as a difference scheme are analysed.

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