scholarly journals Spacetime Singularity Resolution by M-Theory Fivebranes: Calibrated Geometry, Anti-de Sitter Solutions and Special Holonomy Metrics

2008 ◽  
Vol 284 (2) ◽  
pp. 345-389
Author(s):  
Oisín A. P. Mac Conamhna
Keyword(s):  
De Sitter ◽  
Special Holonomy ◽  
Spacetime Singularity ◽  
Singularity Resolution ◽  
Calibrated Geometry ◽  
M Theory

scholarly journals On the Superstrings-Induced Four-Dimensional Gravity and Its Applications to Cosmology

2008 ◽  
Vol 2008 ◽  
pp. 1-27 ◽  
Author(s):  
Masao Iihoshi ◽  
Sergei V. Ketov
Keyword(s):  
Effective Action ◽  
Leading Order ◽  
De Sitter ◽  
Frw Cosmology ◽  
Spacetime Singularity ◽  
Spacetime Curvature ◽  
The Status ◽  
Dimensional Gravity ◽  
Definition Of ◽  
M Theory

We review the status of the fourth-order (quartic in the spacetime curvature) terms induced by superstrings/M-theory (compactified on a warped torus) in the leading order with respect to the Regge slope parameter, and study their (nonperturbative) impact on the evolution of the Hubble scale in the context of the four-dimensional FRW cosmology. After taking into account the quantum ambiguities in the definition of the off-shell superstring effective action, we propose the generalized Friedmann equations, find the existence of their (de Sitter) exact inflationary solutions without a spacetime singularity, and constrain the ambiguities by demanding stability and the scale factor duality invariance of our solutions. The most naive (Bel-Robinson tensor squared) quartic terms are ruled out, thus giving the evidence for the necessity of extra quartic (Ricci tensor-dependent) terms in the off-shell gravitational effective action for superstrings. Our methods are generalizable to the higher orders in the spacetime curvature.

scholarly journals Towards the Structure of Black Holes in Asymptotically Safe Gravity

2018 ◽  
Author(s):  
Adémólá Adéìféoba
Keyword(s):  
Black Holes ◽  
Fixed Point ◽  
Renormalization Group ◽  
Cosmological Constant ◽  
Critical Exponents ◽  
De Sitter ◽  
Renormalization Group Flow ◽  
Spacetime Singularity ◽  
Singularity Resolution ◽  
Group Flow

Asymptotically safe quantum gravity suggests a resolution to the classical spacetime singularity of Schwarzschild-(A)dS black holes. In particular, this is realizable only for a vanishing microscopic value of the dimensionless cosmological constant at the asymptotically safe fixed point. To accommodate a nonzero infrared value of the cosmological constant, we consider the linearized Renormalization Group flow away from the fixed point, which is characterized by two critical exponents in the Einstein-Hilbert truncation. In this study, we show that the realization of a regular de-Sitter core places a bound on the universal gravitational critical exponents. Accordingly, our study hints at the possibility of singularity resolution in black holes, as explicit estimates of the critical exponents in the literature point towards a realization of our bound.

scholarly journals SUPERGRAVITY DESCRIPTION OF FIELD THEORIES ON CURVED MANIFOLDS AND A NO GO THEOREM

2001 ◽  
Vol 16 (05) ◽  
pp. 822-855 ◽  
Author(s):  
JUAN MALDACENA ◽  
CARLOS NUÑEZ
Keyword(s):  
Field Theory ◽  
Conformal Field Theory ◽  
Riemann Surface ◽  
Riemann Surfaces ◽  
Field Theories ◽  
De Sitter ◽  
Curved Manifolds ◽  
Conformal Field ◽  
Low Energies ◽  
M Theory

In the first part of this paper we find supergravity solutions corresponding to branes on worldvolumes of the form Rd×Σ where Σ is a Riemann surface. These theories arise when we wrap branes on holomorphic Riemann surfaces inside K3 or CY manifolds. In some cases the theory at low energies is a conformal field theory with two less dimensions. We find some non-singular supersymmetric compactifications of M-theory down to AdS5. We also propose a criterion for permissible singularities in supergravity solutions. In the second part of this paper, which can be read independently of the first, we show that there are no non-singular Randall-Sundrum or de-Sitter compactifications for large class of gravity theories.

scholarly journals A CHERN–SIMONS E8 GAUGE THEORY OF GRAVITY IN D = 15, GRAND UNIFICATION AND GENERALIZED GRAVITY IN CLIFFORD SPACES

2007 ◽  
Vol 04 (08) ◽  
pp. 1239-1257 ◽  
Author(s):  
CARLOS CASTRO
Keyword(s):  
Gauge Theory ◽  
Grand Unification ◽  
De Sitter ◽  
Sitter Group ◽  
Yang Mills ◽  
Theory Of Gravity ◽  
M Theory ◽  
Chern Simons ◽  
Topological Part ◽  
Gauge Theory Of Gravity

A novel Chern–Simons E8 gauge theory of gravity in D = 15 based on an octicE8 invariant expression in D = 16 (recently constructed by Cederwall and Palmkvist) is developed. A grand unification model of gravity with the other forces is very plausible within the framework of a supersymmetric extension (to incorporate spacetime fermions) of this Chern–Simons E8 gauge theory. We review the construction showing why the ordinary 11D Chern–Simons gravity theory (based on the Anti de Sitter group) can be embedded into a Clifford-algebra valued gauge theory and that an E8 Yang–Mills field theory is a small sector of a Clifford (16) algebra gauge theory. An E8 gauge bundle formulation was instrumental in understanding the topological part of the 11-dim M-theory partition function. The nature of this 11-dim E8 gauge theory remains unknown. We hope that the Chern–Simons E8 gauge theory of gravity in D = 15 advanced in this work may shed some light into solving this problem after a dimensional reduction.

scholarly journals M-theory on special holonomy spaces

2002 ◽  
Author(s):  
Mirjam Cvetič
Keyword(s):  
Special Holonomy ◽  
M Theory

scholarly journals String and M-theory deformations of manifolds with special holonomy

2005 ◽  
Vol 2005 (07) ◽  
pp. 075-075 ◽  
Author(s):  
Hong Lü ◽  
Christofer N Pope ◽  
Kellog S Stelle ◽  
Paul K Townsend
Keyword(s):  
Special Holonomy ◽  
M Theory

scholarly journals Can a false vacuum bubble remove the singularity inside a black hole?

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
Suddhasattwa Brahma ◽  
Dong-han Yeom
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Thin Shell ◽  
Apparent Horizon ◽  
False Vacuum ◽  
De Sitter ◽  
Singularity Formation ◽  
Null Direction ◽  
Singularity Resolution ◽  
Hole Model

Abstract We investigate a regular black hole model with a de Sitter-like core at its center. This type of a black hole model with a false vacuum core was introduced with the hope of singularity-resolution and is a common feature shared by many regular black holes. In this paper, we examine this claim of a singularity-free black hole by employing the thin-shell formalism, and exploring its dynamics, within the Vaidya approximation. We find that during gravitational collapse, the shell necessarily moves along a space-like direction. More interestingly, during the evaporation phase, the shell and the outer apparent horizon approach each other but, unless the evaporation takes place very rapidly, the approaching tendency is too slow to avoid singularity-formation. This shows that albeit a false vacuum core may remove the singularity along the ingoing null direction, there still exists a singularity along the outgoing null direction, unless the evaporation is very strong.

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 Deriving the inflaton in compactified M-theory with a de Sitter vacuum

2019 ◽  
Vol 100 (6) ◽  
Author(s):  
Gordon Kane ◽  
Martin Wolfgang Winkler
Keyword(s):  
De Sitter ◽  
De Sitter Vacuum ◽  
M Theory
Sign in / Sign up

Export Citation Format

Share Document