QUANTUM CORRECTIONS HELP EINSTEIN GRAVITY EXIT GRACIOUSLY

1991 ◽  
Vol 06 (10) ◽  
pp. 861-867 ◽  
Author(s):  
J. PÉREZ-MERCADER
Keyword(s):  
Initial Period ◽  
Einstein Gravity ◽  
Bubble Nucleation ◽  
Time Dependent ◽  
Quantum Corrections ◽  
Exponential Potential ◽  
Exit Problem ◽  
Conformal Equivalence ◽  
The Universe ◽  
Natural Way

We exploit the conformal equivalence between the 1-loop corrected Einstein gravity coupled to a scalar field, and linear Einstein gravity with an exponential potential, to show how the Graceful Exit Problem is solved in the context of this theory in a natural and simple way. What emerges is a scenario with a chaotic initial period followed by an era of old inflation. The resulting bubble nucleation rate is time-dependent in such a way that the second inflationary period, helped by the chaotic period, brings the Universe out of its inflationary era in a self-regulated and natural way.

scholarly journals INFLATION INDUCED BY VACUUM ENERGY AND GRACEFUL EXIT FROM IT

2001 ◽  
Vol 16 (40) ◽  
pp. 2545-2555 ◽  
Author(s):  
E. PAPANTONOPOULOS ◽  
I. PAPPA
Keyword(s):  
Cosmological Constant ◽  
Vacuum Energy ◽  
Einstein Equations ◽  
Time Dependent ◽  
Brane Cosmology ◽  
Fast Growing ◽  
Early Epoch ◽  
The Universe ◽  
Natural Way

Motivated by brane cosmology, we solve the Einstein equations with a time-dependent cosmological constant. Assuming that at an early epoch the vacuum energy scales as 1/log t, we show that the universe passes from a fast growing phase (inflation) to an expanding phase in a natural way.

The interaction between dark energy and dark matter and its connection to the modified gravity

2015 ◽  
Vol 30 (28n29) ◽  
pp. 1545012
Author(s):  
Jian-Hua He ◽  
Bin Wang
Keyword(s):  
Analytic Form ◽  
Rate Function ◽  
Einstein Frame ◽  
Linear Perturbation ◽  
Jordan Frame ◽  
Expansion Of The Universe ◽  
Text Model ◽  
Conformal Equivalence ◽  
The Universe ◽  
Dilation Rate

We review the conformal equivalence in describing the background expansion of the universe by [Formula: see text] gravity both in the Jordan frame and the Einstein frame. In the Jordan frame, we present the general analytic expression for [Formula: see text] models that have the same expansion history as the [Formula: see text]CDM model. This analytic form can provide further insights on how cosmology can be used to test the [Formula: see text] gravity at the largest scales. Moreover we present a systematic and self-consistent way to construct the viable [Formula: see text] model in Jordan frame using the mass dilation rate function from the Einstein frame through the conformal transformation. In addition, we extend our study to the linear perturbation theories and we further exhibit the equivalence of the [Formula: see text] gravity presented in the Jordan frame and Einstein frame in the perturbed space–time. We argue that this equivalence has solid physics root.

scholarly journals From Quantum Unstable Systems to the Decaying Dark Energy: Cosmological Implications

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Aleksander Stachowski ◽  
Marek Szydłowski ◽  
Krzysztof Urbanowski
Keyword(s):  
Dark Energy ◽  
Time Reversal ◽  
Hubble Parameter ◽  
Decay Process ◽  
Time Dependent ◽  
Time Reversal Symmetry ◽  
Exponential Form ◽  
Cosmological Time ◽  
Evolution Of The Universe ◽  
The Universe

We consider a cosmology with decaying metastable dark energy and assume that a decay process of this metastable dark energy is a quantum decay process. Such an assumption implies among others that the evolution of the Universe is irreversible and violates the time reversal symmetry. We show that if we replace the cosmological time t appearing in the equation describing the evolution of the Universe by the Hubble cosmological scale time, then we obtain time dependent Λ(t) in the form of the series of even powers of the Hubble parameter H: Λ(t)=Λ(H). Our special attention is focused on radioactive-like exponential form of the decay process of the dark energy and on the consequences of this type decay.

scholarly journals Power Matrices and Dunn--Belnap Semantics: Reflections on a Remark of Graham Priest

2014 ◽  
Vol 11 (1) ◽  
Author(s):  
Lloyd Humberstone
Keyword(s):  
Equational Logic ◽  
Consequence Relations ◽  
Consequence Relation ◽  
Power Matrix ◽  
Matrix Construction ◽  
The Given ◽  
The Universe ◽  
Power Algebras ◽  
Graham Priest ◽  
Natural Way

The plurivalent logics considered in Graham Priest's recent paper of that name can be thought of as logics determined by matrices (in the `logical matrix' sense) whose underlying algebras are power algebras (a.k.a. complex algebras, or `globals'), where the power algebra of a given algebra has as elements \textit{subsets} of the universe of the given algebra, and the power matrix of a given matrix has has the power algebra of the latter's algebra as its underlying algebra, with its designated elements being selected in a natural way on the basis of those of the given matrix. The present discussion stresses the continuity of Priest's work on the question of which matrices determine consequence relations (for propositional logics) which remain unaffected on passage to the consequence relation determined by the power matrix of the given matrix with the corresponding (long-settled) question in equational logic as to which identities holding in an algebra continue to hold in its power algebra. Both questions are sensitive to a decision as to whether or not to include the empty set as an element of the power algebra, and our main focus will be on the contrast, when it is included, between the power matrix semantics (derived from the two-element Boolean matrix) and the four-valued Dunn--Belnap semantics for first-degree entailment a la Anderson and Belnap) in terms of sets of classical values (subsets of {T, F}, that is), in which the empty set figures in a somewhat different way, as Priest had remarked his 1984 study, `Hyper-contradictions', in which what we are calling the power matrix construction first appeared.

Das Präphysiche Stadium und der Anfang der Welt

1998 ◽  
pp. 74-80
Author(s):  
Malgorzata Szczesniak
Keyword(s):  
Physical State ◽  
Big Bang ◽  
Evolution Of The Universe ◽  
Time Period ◽  
The Creation ◽  
The Absolute ◽  
The Big Bang ◽  
The Universe ◽  
Natural Way

This paper concerns the main physical, philosophical and existential aspects of the ‘pre-physical’ stage in the evolution of the universe. I will discuss the ways that contemporary cosmology tries to: (1) solve the problem about the time period of the ‘pre-physical’ state; (2) answer the question whether the beginning of time was at the same time as the beginning of the existence of the Universe; (3) answer another whether the Big Bang was an absolute beginning of the existence of the Universe or only a beginning of some stage of its evolution; (4) respond to another question whether the absolute beginning of the Universe inevitably implies its creation by God or whether it allows for the possibility of the creation of the Universe in a natural way; and (5) discuss the issue of the ‘singular’ moment. All of these questions, in particular the last one, will be discussed with reference to the latest achievements in the fields of physics and cosmology.

scholarly journals The Large Number Hypothesis and Einstein's Theory of Gravitation

1985 ◽  
Vol 38 (4) ◽  
pp. 547 ◽  
Author(s):  
Yun-Kau Lau
Keyword(s):  
Cosmological Model ◽  
Cosmological Constant ◽  
Matter Density ◽  
Time Dependent ◽  
Field Equations ◽  
Large Number Hypothesis ◽  
Theory Of Gravitation ◽  
The Mean ◽  
Limiting Case ◽  
The Universe

In an attempt to reconcile the large number hypothesis (LNH) with Einstein's theory of gravitation, a tentative generalization of Einstein's field equations with time-dependent cosmological and gravitational constants is proposed. A cosmological model consistent with the LNH is deduced. The coupling formula of the cosmological constant with matter is found, and as a consequence, the time-dependent formulae of the cosmological constant and the mean matter density of the Universe at the present epoch are then found. Einstein's theory of gravitation, whether with a zero or nonzero cosmological constant, becomes a limiting case of the new generalized field equations after the early epoch.

Geometric phase of cosmological scalar and tensor perturbations in f(R) gravity

2018 ◽  
Vol 33 (14) ◽  
pp. 1850077
Author(s):  
Hamideh Balajany ◽  
Mohammad Mehrafarin
Keyword(s):  
Scalar Field ◽  
Harmonic Oscillator ◽  
Geometric Phase ◽  
Berry Phase ◽  
Time Dependent ◽  
Einstein Theory ◽  
Tensor Perturbations ◽  
Cosmological Scalar ◽  
Conformal Equivalence

By using the conformal equivalence of f(R) gravity in vacuum and the usual Einstein theory with scalar-field matter, we derive the Hamiltonian of the linear cosmological scalar and tensor perturbations in f(R) gravity in the form of time-dependent harmonic oscillator Hamiltonians. We find the invariant operators of the resulting Hamiltonians and use their eigenstates to calculate the adiabatic Berry phase for sub-horizon modes as a Lewis–Riesenfeld phase.

scholarly journals Extending trinity to the scalar sector through discrete flavoured symmetries

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
João M. Alves ◽  
Francisco J. Botella ◽  
Gustavo C. Branco ◽  
Miguel Nebot
Keyword(s):  
Mass Matrix ◽  
Baryon Asymmetry ◽  
Tree Level ◽  
Strong Reduction ◽  
Ckm Matrix ◽  
The Standard Model ◽  
The Universe ◽  
The Trinity ◽  
Scalar Sector ◽  
Natural Way

Abstract We conjecture the existence of a relation between elementary scalars and fermions, making it plausible the existence of three Higgs doublets. We introduce a Trinity Principle (TP) which, given the fact that there are no massless quarks, requires the existence of a minimum of three Higgs doublets. The TP states that each row of the mass matrix of a quark of a given charge should receive the contribution from one and only one scalar doublet and furthermore a given scalar doublet should contribute to one and only one row of the mass matrix of a quark of a given charge. This principle is analogous to the Natural Flavour Conservation (NFC) of Glashow and Weinberg with the key distinction that NFC required the introduction of a flavour blind symmetry, while the TP requires a flavoured symmetry, to be implemented in a natural way. We provide two examples which satisfy the Trinity Principle based on $${\mathbb {Z}}_3$$Z3 and $${\mathbb {Z}}_2\times {\mathbb {Z}}_2'$$Z2×Z2′ flavoured symmetries, and show that they are the minimal multi-Higgs extensions of the Standard Model where CP can be imposed as a symmetry of the full Lagrangian and broken by the vacuum, without requiring soft-breaking terms. We show that the vacuum phases are sufficient to generate a complex CKM matrix, in agreement with experiment. The above mentioned flavoured symmetries lead to a strong reduction in the number of parameters in the Yukawa interactions, enabling a control of the Scalar Flavour Changing Neutral Couplings (SFCNC). We analyse some of the other physical implications of the two models, including an estimate of the enhancement of the Baryon Asymmetry of the Universe provided by the new sources of CP violation, and a discussion of the strength of their tree-level SFCNC.

scholarly journals LITTLE RIP COSMOLOGICAL MODELS WITH TIME-DEPENDENT EQUATION OF STATE

2012 ◽  
Vol 27 (36) ◽  
pp. 1250210 ◽  
Author(s):  
I. BREVIK ◽  
V. V. OBUKHOV ◽  
K. E. OSETRIN ◽  
A. V. TIMOSHKIN
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Cosmological Models ◽  
Time Dependent ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Energy Models ◽  
Sitter Spacetime ◽  
The Universe ◽  
Far Future

Specific dark energy models, leading to the Little Rip (LR) cosmology in the far future, are investigated. Conditions for the occurrence of LR in terms of the parameters present in the proposed equation of state for the dark energy cosmic fluid are studied. Estimates about the time needed before the occurrence of the small singularity in the standard LR model in which the universe approaches the de Sitter spacetime asymptotically, are given.

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