scholarly journals Modified Gravity in Higher Dimensions, Flux Compactification, and Cosmological Inflation

Symmetry ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1528 ◽  
Author(s):  
Sergei V. Ketov
Keyword(s):  
Cosmological Constant ◽  
Modified Gravity ◽  
Higher Dimensions ◽  
Gravity Theory ◽  
Inflationary Model ◽  
Positive Cosmological Constant ◽  
Flux Compactification ◽  
Modified Gravity Theory ◽  
Cosmological Inflation ◽  
Form Field

We review a possible origin of cosmological inflation from higher ( D ) spacetime dimensions in the context of modified gravity theory. It is demonstrated that it requires a spontaneous warped compactification of higher ( D ) spacetime dimensions together with the stabilization of extra ( D − 4 ) dimensions by Freund–Rubin mechanism. The relevant tools include an extra gauge ( D / 2 − 1 ) -form field with a non-vanishing flux in compact dimensions and a positive cosmological constant in D dimensions. Those features are illustrated on the specific example in eight spacetime dimensions compactified on a four-sphere with a warped factor and a flux, which leads to a viable Starobinsky-like inflationary model in four (non-compact) spacetime dimensions.

scholarly journals Nonlinear dynamics of flux compactification

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Maxence Corman ◽  
William E. East ◽  
Matthew C. Johnson
Keyword(s):  
Flux Compactifications ◽  
Nonlinear Evolution ◽  
Einstein Equations ◽  
Accelerated Expansion ◽  
Positive Cosmological Constant ◽  
Flux Compactification ◽  
Trapped Surfaces ◽  
Slow Roll ◽  
Form Field ◽  
Lower Dimensional

Abstract We study the nonlinear evolution of unstable flux compactifications, applying numerical relativity techniques to solve the Einstein equations in D dimensions coupled to a q-form field and positive cosmological constant. We show that initially homogeneous flux compactifications are unstable to dynamically forming warped compactifications. In some cases, we find that the warping process can serve as a toy-model of slow-roll inflation, while in other instances, we find solutions that eventually evolve to a singular state. Analogous to dynamical black hole horizons, we use the geometric properties of marginally trapped surfaces to characterize the lower dimensional vacua in the inhomogeneous and dynamical settings we consider. We find that lower-dimensional vacua with a lower expansion rate are dynamically favoured, and in some cases find spacetimes that undergo a period of accelerated expansion followed by contraction.

scholarly journals A Modified Gravity Theory: Null Aether

2019 ◽  
Vol 71 (3) ◽  
pp. 312 ◽  
Author(s):  
Metin Gürses ◽  
Çetin Şentürk
Keyword(s):  
Modified Gravity ◽  
Gravity Theory ◽  
Modified Gravity Theory

MODIFIED GRAVITY THEORY DUE TO POSITIVE AS WELL AS NEGATIVE CURVATURE INDUCED ACCELERATION

2012 ◽  
Vol 21 (02) ◽  
pp. 1250012
Author(s):  
PRIYADARSHI MAJUMDAR
Keyword(s):  
Dark Energy ◽  
Modified Gravity ◽  
Negative Curvature ◽  
Gravity Theory ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Negative Power ◽  
Modified Gravity Theory ◽  
Phase Q ◽  
The Universe

We formulate a modified gravity theory that eliminates the need for dark energy and is stable for a Lagrangian containing R, R2 as well as 1/R terms (i.e. nonlinear contributions of the Ricci curvature with a non-analytic model of f(R) at R = 0) without considering any matter-dominated era. The terms with positive powers (1, 2) of the curvature support the inflationary epoch while the terms with negative power (-1) serves as effective dark energy, supporting current cosmic acceleration. We present a few analytical solutions of evolution equation for the deceleration parameter q as a function of Hubble parameter H and time t; specially in one solution, the universe evolves continuously from q = 1 (a radiation-dominated epoch) to q = -1/2 (dark-energy-dominated late-time accelerating phase) when the universe is sufficiently old. The solution is supported by numerical results. The transition from the decelerated (q > 0) to the accelerated phase (q < 0) of expansion takes place smoothly without having to resort to a study of asymptotic behavior.

scholarly journals EFFECTS OF CHERN–SIMONS CORRECTIONS ON CONSERVED QUANTITIES OF RELATIVISTIC FLUID

2010 ◽  
Vol 25 (31) ◽  
pp. 2655-2666
Author(s):  
KOHKICHI KONNO ◽  
TOYOKI MATSUYAMA ◽  
SATOSHI TANDA
Keyword(s):  
Fluid Flow ◽  
Modified Gravity ◽  
Gravity Theory ◽  
Conserved Quantities ◽  
Maxwell Theory ◽  
Relativistic Fluid ◽  
Modified Gravity Theory ◽  
Chern Simons

We consider relativistic fluid flow under Chern–Simons modified Maxwell theory and under Chern–Simons modified gravity theory. We take account of the effects of Chern–Simons corrections on the quantities of fluid flow that is conserved without the Chern–Simons corrections. We find that the conservations of several quantities are generally broken by the Chern–Simons corrections.

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