scholarly journals THE INTERFACE OF COSMOLOGY WITH STRING AND M(ILLENNIUM) THEORY

2001 ◽  
Vol 16 (30) ◽  
pp. 4803-4843 ◽  
Author(s):  
DAMIEN A. EASSON
Keyword(s):  
Early Universe ◽  
Extra Dimensions ◽  
Large Extra Dimensions ◽  
Short Review ◽  
Big Bang ◽  
Space Time ◽  
String Cosmology ◽  
Brane World ◽  
Recent Developments ◽  
M Theory

The purpose of this review is to discuss recent developments occurring at the interface of cosmology with string and M theory. We begin with a short review of 1980s string cosmology and the Brandenberger–Vafa mechanism for explaining space–time dimensionality. It is shown how this scenario has been modified to include the effects of p-brane gases in the early universe. We then introduce the Pre-Big-Bang scenario (PBB), Hořava–Witten heterotic M theory and the work of Lukas, Ovrut and Waldram, and end with a discussion of large extra dimensions, the Randall–Sundrum model and Brane World cosmologies.

scholarly journals Quasi-Steady State Cosmology

1994 ◽  
Vol 159 ◽  
pp. 293-299
Author(s):  
G. Burbidge ◽  
F. Hoyle ◽  
J.V. Narlikar
Keyword(s):  
Steady State ◽  
Early Universe ◽  
Particle Physics ◽  
Physical Theory ◽  
Big Bang ◽  
Quasi Steady State ◽  
Recent Developments ◽  
History Of ◽  
The Big Bang ◽  
The Universe

The standard big bang cosmology has the universe created out of a primeval explosion that not only created matter and radiation but also spacetime itself. The big bang event itself cannot be discussed within the framework of a physical theory but the events following it are in principle considered within the scope of science. The recent developments on the frontier between particle physics and cosmology highlight the attempts to chart the history of the very early universe.

scholarly journals Space–time singularities and cosmic censorship conjecture: A Review with some thoughts

2020 ◽  
Vol 35 (14) ◽  
pp. 2030007 ◽  
Author(s):  
Yen Chin Ong
Keyword(s):  
General Relativity ◽  
Short Review ◽  
Big Bang ◽  
Cosmic Censorship ◽  
Space Time ◽  
Singularity Theorems ◽  
Time Singularities ◽  
The One ◽  
The Big Bang ◽  
Cosmic Censorship Conjecture

The singularity theorems of Hawking and Penrose tell us that singularities are common place in general relativity. Singularities not only occur at the beginning of the Universe at the Big Bang, but also in complete gravitational collapses that result in the formation of black holes. If singularities — except the one at the Big Bang — ever become “naked,” i.e. not shrouded by black hole horizons, then it is expected that problems would arise and render general relativity indeterministic. For this reason, Penrose proposed the cosmic censorship conjecture, which states that singularities should never be naked. Various counterexamples to the conjecture have since been discovered, but it is still not clear under which kind of physical processes one can expect violation of the conjecture. In this short review, I briefly examine some progresses in space–time singularities and cosmic censorship conjecture. In particular, I shall discuss why we should still care about the conjecture, and whether we should be worried about some of the counterexamples. This is not meant to be a comprehensive review, but rather to give an introduction to the subject, which has recently seen an increase of interest.

NONCOMMUTATIVE D-BRANE WORLD, BLACK HOLES AND EXTRA DIMENSIONS

2009 ◽  
Vol 24 (18n19) ◽  
pp. 3571-3576 ◽  
Author(s):  
SUPRIYA KAR
Keyword(s):  
Black Holes ◽  
String Theory ◽  
Extra Dimensions ◽  
Space Time ◽  
Brane World ◽  
Spherically Symmetric ◽  
Axially Symmetric ◽  
Ordinary Space ◽  
Classical Black Holes ◽  
Type Iib String Theory

Inspired by the space-time noncommutativity on a D5-brane world, in a type IIB string theory, we explore the possibility of an emergent 4D ordinary space-time in the formalism. In particular, a curved D3-brane dynamics is worked out to obtain an axially symmetric and a spherically symmetric AdS and dS black holes. Extremal geometries are analyzed, using the noncommutative scaling. The emerging two dimensional semi-classical black holes are investigated to yield evidence for extra dimensions in the curved brane-world. Interestingly, a tunneling between dS to AdS vacua in the formalism is briefly discussed by incorporating the Hagedorn transitions in string theory.

scholarly journals A Scale at 10 MeV, Gravitational Topological Vacuum, and Large Extra Dimensions

Universe ◽  
2018 ◽  
Vol 4 (7) ◽  
pp. 80
Author(s):  
Ufuk Aydemir
Keyword(s):  
Thermal History ◽  
Extra Dimensions ◽  
Weak Interactions ◽  
Large Extra Dimensions ◽  
Big Bang ◽  
Length Scale ◽  
Big Bang Nucleosynthesis ◽  
History Of ◽  
The Universe ◽  
Bonnet Term

We discuss a possible scale of gravitational origin at around 10 MeV, or 10−12 cm, which arises in the MacDowell–Mansouri formalism of gravity due to the topological Gauss–Bonnet term in the action, as pointed out by Bjorken several years ago. A length scale of the same size emerges also in the Kodama solution in gravity, which is known to be closely related to the MacDowell–Mansouri formulation. We particularly draw attention to the intriguing incident that the existence of six compact extra dimensions originated from TeV-scale quantum gravity as well points to a length scale of 10−12 cm, as the compactification scale. The presence of six such extra dimensions is also in remarkable consistency with the MacDowell–Mansouri formalism; it provides a possible explanation for the factor of ∼10120 multiplying the Gauss–Bonnet term in the action. We also comment on the relevant implications of such a scale regarding the thermal history of the universe motivated by the fact that it is considerably close to 1–2 MeV below which the weak interactions freeze out, leading to Big Bang Nucleosynthesis.

scholarly journals Infinity in string cosmology: A review through open problems

2017 ◽  
Vol 26 (04) ◽  
pp. 1730009 ◽  
Author(s):  
Ignatios Antoniadis ◽  
Spiros Cotsakis
Keyword(s):  
Higher Order ◽  
String Cosmology ◽  
Tree Level ◽  
Open Problems ◽  
String Correction ◽  
Recent Developments ◽  
M Theory

We review recent developments in the field of string cosmology with particular emphasis on open problems having to do mainly with geometric asymptotics and singularities. We discuss outstanding issues in a variety of currently popular themes, such as tree-level string cosmology asymptotics, higher-order string correction effects, M-theory cosmology, braneworlds and finally ambient cosmology.

Stranger things: multiverse, string cosmology, physical eschatology

2019 ◽  
pp. 464-496
Author(s):  
Milan M. Ćirković
Keyword(s):  
Big Bang ◽  
String Cosmology ◽  
The Other ◽  
Research Activity ◽  
Eternal Inflation ◽  
The Future ◽  
Anthropic Reasoning ◽  
M Theory ◽  
Infinite Set

The period (roughly) 1990-today is characterized by a big watershed and branching of cosmology into multiple and hitherto unexpected directions. On one side, the generic chaotic/eternal inflation has provided physical grounds for rather wild speculative ideas about the multiverse: the possibly infinite set of cosmological domains (‘universes’). In order to determine how observed features of our universe are (im)probable in the multiverse context requires application of anthropic reasoning which is still controversial in many circles. On the other side, we encounter applications of other speculative physical theories, like the string/M-theory to cosmology, resulting in unusual hypotheses like those of the pre-Big Bang cosmologies. In this period we have also witnessed the birth of physical eschatology as the true ‘cosmology of the future’. This chapter will attempt a survey of these and related developments, with necessary qualifications which accompany any ongoing, evolving research activity.

scholarly journals Neutrino oscillations and the early universe

Open Physics ◽  
2004 ◽  
Vol 2 (3) ◽  
Author(s):  
Daniela Kirilova
Keyword(s):  
Early Universe ◽  
Neutrino Oscillation ◽  
Neutrino Oscillations ◽  
Atmospheric Neutrino ◽  
Short Review ◽  
Big Bang ◽  
Big Bang Nucleosynthesis ◽  
Cosmological Constraints ◽  
Theoretical Status

AbstractThe observational and theoretical status of neutrino oscillations in connection with solar and atmospheric neutrino anomalies is presented briefly. The effect of neutrino oscillations on the evolution of the early Universe is discussed in detail. A short review is given of the standard Big Bang Nucleosynthesis (BBN) and the influence of resonant and non-resonant neutrino oscillations on active neutrinos and on primordial synthesis of He-4. BBN cosmological constraints on neutrino oscillation parameters are discussed.

scholarly journals Quantum String Cosmology

Universe ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 14
Author(s):  
Maurizio Gasperini
Keyword(s):  
Effective Action ◽  
Weak Coupling ◽  
Short Review ◽  
Big Bang ◽  
String Cosmology ◽  
Low Energy ◽  
Initial State ◽  
Quantum Process ◽  
Asymptotically Flat ◽  
Quantum Transitions

We present a short review of possible applications of the Wheeler-De Witt equation to cosmological models based on the low-energy string effective action, and characterised by an initial regime of asymptotically flat, low energy, weak coupling evolution. Considering in particular a class of duality-related (but classically disconnected) background solutions, we shall discuss the possibility of quantum transitions between the phases of pre-big bang and post-big bang evolution. We will show that it is possible, in such a context, to represent the birth of our Universe as a quantum process of tunneling or “anti-tunneling” from an initial state asymptotically approaching the string perturbative vacuum.

scholarly journals THE EFFECTIVE ENERGY-MOMENTUM TENSOR IN KALUZA–KLEIN GRAVITY WITH LARGE EXTRA DIMENSIONS AND OFF-DIAGONAL METRICS

2002 ◽  
Vol 11 (09) ◽  
pp. 1355-1380 ◽  
Author(s):  
J. PONCE DE LEON
Keyword(s):  
Energy Momentum Tensor ◽  
Dimensional Space ◽  
Large Extra Dimensions ◽  
Momentum Tensor ◽  
Space Time ◽  
Brane World ◽  
Splitting Technique ◽  
Klein Theory ◽  
Electromagnetic Tensor ◽  
Kaluza Klein

We consider a version of Kaluza–Klein theory where the cylinder condition is not imposed. The metric is allowed to have explicit dependence on the "extra" coordinate(s). This is the usual scenario in brane-world and space-time-matter theories. We extend the usual discussion by considering five-dimensional metrics with off-diagonal terms. We replace the condition of cylindricity by the requirement that physics in four-dimensional space-time should remain invariant under changes of coordinates in the five-dimensional bulk. This invariance does not eliminate physical effects from the extra dimension but separates them from spurious geometrical ones. We use the appropriate splitting technique to construct the most general induced energy-momentum tensor, compatible with the required invariance. It generalizes all previous results in the literature. In addition, we find two four-vectors, [Formula: see text] and [Formula: see text], induced by off-diagonal metrics, that separately satisfy the usual equation of continuity in 4D. These vectors appear as source-terms in equations that closely resemble the ones of electromagnetism. These are Maxwell-like equations for an antisymmetric tensor [Formula: see text] that generalizes the usual electromagnetic one. This generalization is not an assumption, but follows naturally from the dimensional reduction. Thus, if[Formula: see text] could be identified with the electromagnetic tensor, then the theory would predict the existence of classical magnetic charge and current. The splitting formalism used allows us to construct 4D physical quantities from five-dimensional ones, in a way that is independent from how we choose our space-time coordinates from those of the bulk.

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