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 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 Inflationary Implications of the Covariant Entropy Bound and the Swampland de Sitter Conjectures

Universe ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 423
Author(s):  
Dibya Chakraborty ◽  
Cesar Damian ◽  
Alberto González Bernal ◽  
Oscar Loaiza-Brito
Keyword(s):  
Time Dependence ◽  
Early Phase ◽  
Transition Amplitude ◽  
Time Dependent ◽  
Accelerated Expansion ◽  
Explicit Calculation ◽  
De Sitter ◽  
Flux Compactification ◽  
Slow Roll ◽  
Entropy Bound

We present a proposal to relate the de Sitter conjecture (dSC) with the time dependence of fluxes via the covariant entropy bound (CEB). By assuming an early phase of accelerated expansion where the CEB is satisfied, we take into account a contribution from time-dependent flux compactification to the four-dimensional entropy which establishes a bound on the usual slow-roll parameters ηH and ϵH. We also show an explicit calculation of entropy from a toroidal flux compactification, from a transition amplitude of time-dependent fluxes which allows us to determine the conditions on which the bounds on the slow-roll parameters are in agreement to the dSC.

scholarly journals COSMOLOGY IN SCALAR–TENSOR THEORY AND ASYMPTOTICALLY de SITTER UNIVERSE

2001 ◽  
Vol 16 (20) ◽  
pp. 1303-1313 ◽  
Author(s):  
A. A. SEN ◽  
S. SEN
Keyword(s):  
Accelerated Expansion ◽  
Late Time ◽  
Scalar Tensor Theory ◽  
Dilaton Field ◽  
De Sitter ◽  
Positive Cosmological Constant ◽  
Expansion Phase ◽  
Tensor Theory ◽  
Sitter Universe ◽  
De Sitter Universe

We have investigated the cosmological scenarios with a four-dimensional effective action which is connected with multidimensional, supergravity and string theories. The solution for the scale factor is such that initially universe undergoes a decelerated expansion but in late times it enters into the accelerated expansion phase. In fact, it asymptotically becomes a de Sitter universe. The dilaton field in our model is a decreasing function of time and it becomes a constant in late time resulting the exit from the scalar–tensor theory to the standard Einstein's gravity. Also the dilaton field results in the existence of a positive cosmological constant in late times.

scholarly journals COSMOLOGICAL CONSTANT OF THE INFLATING BRANES IN THE RANDALL–SUNDRUM–ODA MODEL

2001 ◽  
Vol 16 (30) ◽  
pp. 1933-1940 ◽  
Author(s):  
LAURA MERSINI
Keyword(s):  
Cosmological Constant ◽  
Source Term ◽  
Einstein Equations ◽  
Expansion Rate ◽  
Fifth Dimension ◽  
Scale Factors ◽  
Slow Roll ◽  
Effective Expansion ◽  
The Many ◽  
Decreasing Functions

We examine the issue of the cosmological constant in the many inflating branes scenario, extending on two recent models by I. Oda and Randall–Sundrum. The exact solution in a closed form is found in the slow-roll approximation for the branes. We show that each positive tension brane has an induced canonical cosmological constant and expansion rate that are decreasing functions of their position in the fifth dimension. The reason is that the square of the effective expansion rate enters as a source term in the Einstein equations for the branes. Thus the brane has two scale factors depending on time and the fifth dimension respectively. A displacement of the brane along the fifth dimension would adjust its effective expansion rate in such a way that it compensates for its internal energy changes due to inflation and possible phase transitions.

scholarly journals MULTIDIMENSIONAL GRAVITATIONAL MODEL WITH ANISOTROPIC PRESSURE

2013 ◽  
Vol 22 (13) ◽  
pp. 1350075 ◽  
Author(s):  
O. A. GRIGORIEVA ◽  
G. S. SHAROV
Keyword(s):  
Equations Of State ◽  
Einstein Equations ◽  
Accelerated Expansion ◽  
Anisotropic Pressure ◽  
Gravitational Model ◽  
Spatial Dimensions ◽  
Type Ia ◽  
Expansion Of The Universe ◽  
Ia Supernovae ◽  
The Universe

We consider the gravitational model with additional spatial dimensions and anisotropic pressure which is nonzero only in these dimensions. Cosmological solutions of the Einstein equations in this model include accelerated expansion of the universe at late stage of its evolution and dynamical compactification of extra dimensions. This model describes observational data for Type Ia supernovae on the level or better than the ΛCDM model. We analyze two equations of state resulting in different predictions for further evolution, but in both variants the acceleration epoch is finite.

scholarly journals Inflation in terms of a viscous van der Waals coupled fluid

2018 ◽  
Vol 15 (09) ◽  
pp. 1850150 ◽  
Author(s):  
I. Brevik ◽  
V. V. Obukhov ◽  
A. V. Timoshkin
Keyword(s):  
Van Der Waals ◽  
Accelerated Expansion ◽  
Frw Universe ◽  
Slow Roll ◽  
Analytic Expressions ◽  
Acceleration Of The Universe ◽  
The Universe ◽  
Gravitational Equations ◽  
Friedmann Robertson Walker ◽  
Planck Satellite

We propose to describe the acceleration of the universe by introducing a model of two coupled fluids. We focus on the accelerated expansion at the early stages. The inflationary expansion is described in terms of a van der Waals equation of state for the cosmic fluid, when account is taken of bulk viscosity. We assume that there is a weak interaction between the van der Waals fluid and the second component (matter). The gravitational equations for the energy densities of the two components are solved for a homogeneous and isotropic Friedmann–Robertson–Walker (FRW) universe, and analytic expressions for the Hubble parameter are obtained. The slow-roll parameters, the spectral index, and the tensor-to-scalar ratio are calculated and compared with the most recent astronomical data from the Planck satellite. Given reasonable restriction on the parameters, the agreement with observations is favorable.

scholarly journals ON ISSUES IN SWISS CHEESE COMPACTIFICATIONS

2008 ◽  
Vol 23 (36) ◽  
pp. 3031-3047 ◽  
Author(s):  
AALOK MISRA
Keyword(s):  
Inverse Problem ◽  
Black Holes ◽  
Flux Compactifications ◽  
Large Volume ◽  
Type Ii ◽  
Swiss Cheese ◽  
Slow Roll ◽  
Slow Roll Inflation

We give a brief review of our previous works.1,2 We discuss two sets of issues. The first has to do with the possibility of getting a non-supersymmetric dS minimum without the addition of [Formula: see text]-branes as in KKLT, and axionic slow-roll inflation, in type II flux compactifications. The second has to do with the "Inverse Problem"3 and "Fake Superpotentials"4 for extremal (non)supersymmetric black holes in type II compactifications. We use (orientifold of) a "Swiss Cheese" Calabi–Yau5 expressed as a degree-18 hypersurface in WCP4[1, 1, 1, 6, 9] in the "large-volume-scenario" limit6 for the former.

scholarly journals Inflationary universe in terms of a van der Waals viscous fluid

2017 ◽  
Vol 14 (12) ◽  
pp. 1750185 ◽  
Author(s):  
I. Brevik ◽  
E. Elizalde ◽  
S. D. Odintsov ◽  
A. V. Timoshkin
Keyword(s):  
Van Der Waals ◽  
Early Time ◽  
Accelerated Expansion ◽  
Inflationary Universe ◽  
Van Der Waals Equation ◽  
Slow Roll ◽  
Viscosity Term ◽  
Gravitational Equations ◽  
Planck Satellite

The inflationary expansion of our early-time universe is considered in terms of the van der Waals equation, as equation of state for the cosmic fluid, where a bulk viscosity contribution is assumed to be present. The corresponding gravitational equations for the energy density in a homogeneous and isotropic Friedmann–Lemaître–Robertson–Walker universe are solved, and an analytic expression for the scale factor is obtained. Attention is paid, specifically, to the role of the viscosity term in the accelerated expansion; the values of the slow-roll parameters, the spectral index, and the tensor-to-scalar ratio for the van der Waals model are calculated and compared with the most recent astronomical data from the Planck satellite. By imposing reasonable restrictions on the parameters of the van der Waals equation, in the presence of viscosity, it is shown to be possible for this model to comply quite precisely with the observational data. One can therefore conclude that the inclusion of viscosity in the theory of the inflationary epoch may definitely improve the cosmological models.

MATHEMATICAL THEORY OF SELF-DUAL COSMIC STRINGS: EXISTENCE AND OBSTRUCTIONS

1996 ◽  
Vol 11 (02) ◽  
pp. 203-227
Author(s):  
YISONG YANG
Keyword(s):  
Mathematical Theory ◽  
Weak Interactions ◽  
Cosmic Strings ◽  
Einstein Equations ◽  
Positive Cosmological Constant ◽  
Geodesic Completeness ◽  
Survey Article ◽  
Higgs Vacuum ◽  
Vacuum States ◽  
Vortex Solutions

This is a survey article concerning some recent mathematical results for the static selfdual cosmic-string solutions in the Abelian Higgs model and in the Weinberg-Salam standard model unifying electromagnetic and weak interactions, both coupled with gravity through the Einstein equations. For the Abelian Higgs strings there is a nearly complete picture. If the Riemann surface M on which the strings reside is compact, it can be shown that M must be S2 up to topological equivalence and there are only countably many values of the Higgs vacuum states for strings to exist. When M is noncompact and conformally a plane there are exact obstructions to the finiteness of energies and geodesic completeness of solutions. For the Weinberg-Salam strings, much is to be achieved. It can be shown in this case that self-dual strings generated from W and Higgs condensation lead to an explicit formula for a positive cosmological constant and the gravitational metric is always noncomplete. This feature leads to the properties that the metric decays sufficiently rapidly at infinity and there exist non-Abelian electroweak strings of finite energies. It is established that for any integer N there are always suitable ranges of the electroweak parameters to allow the existence of W- and Higgs-condensed N-vortex solutions of finite energies.

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