scholarly journals Cosmological particle creation beyond de Sitter

2019 ◽  
Vol 28 (09) ◽  
pp. 1930015 ◽  
Author(s):  
Sujoy K. Modak
Keyword(s):  
Dark Energy ◽  
Particle Creation ◽  
Vacuum State ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Central Focus ◽  
Sitter Spacetime ◽  
Multi Stage ◽  
Classical Behavior ◽  
The Universe

Over the years, de Sitter spacetime has been a central focus in studies involving quantum fields, for its importance in the early and late expansion stages of the universe. While de Sitter spacetime closely mimics characteristics of the inflationary and dark energy dominated universe, it does not help to understand the radiation and matter dominated expansions. In this paper, we revisit some recent works involving the author which study gravitational particle creation beyond the de Sitter stage. Specifically, we present novel aspects of particle creation in the radiation dominated universe and then provide an analysis of time evolution of the primordial (Bunch–Davies) vacuum state, its particle excitation and quantum versus classical behavior of field modes in a multi-stage universe, comprising of (i) the inflationary de Sitter (ii) the radiation dominated and (iii) the late dark energy dominated stages.

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.

scholarly journals Primordial Dark Energy from a Condensate of Spinors in a 5D Vacuum

2013 ◽  
Vol 2013 ◽  
pp. 1-7
Author(s):  
Pablo Alejandro Sánchez ◽  
Mauricio Bellini
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Inflationary Universe ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Dark Energy Density ◽  
Sitter Spacetime ◽  
Interesting Candidate ◽  
Expansion Of The Universe ◽  
The Universe

We explore the possibility that the expansion of the universe can be driven by a condensate of spinors which are free of interactions in a 5D relativistic vacuum defined in an extended de Sitter spacetime which is Riemann flat. The extra coordinate is considered as noncompact. After making a static foliation on the extra coordinate, we obtain an effective 4D (inflationary) de Sitter expansion which describes an inflationary universe. We found that the condensate of spinors studied here could be an interesting candidate to explain the presence of dark energy in the early universe. The dark energy density which we are talking about is poured into smaller subhorizon scales with the evolution of the inflationary expansion.

scholarly journals INFLATIONARY DARK ENERGY FROM A CONDENSATE OF SPINORS IN A 5D VACUUM

2013 ◽  
Vol 22 (12) ◽  
pp. 1342028 ◽  
Author(s):  
PABLO ALEJANDRO SÁNCHEZ ◽  
MAURICIO BELLINI
Keyword(s):  
Dark Energy ◽  
Early Universe ◽  
Inflationary Universe ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Physical Origin ◽  
Sitter Spacetime ◽  
Interesting Candidate ◽  
Expansion Of The Universe ◽  
The Universe

What is the physical origin of dark energy? Could this energy be originated by other fields than the inflaton? In this paper, we explore the possibility that the expansion of the universe can be driven by a condensate of spinors. These spinors are free of interactions on five-dimensional (5D) relativistic vacuum in an extended de Sitter spacetime. The extra coordinate is considered as noncompact. After making a static foliation on the extra coordinate, we obtain an effective four-dimensional (4D) (inflationary) de Sitter expansion which describes an inflationary universe. In view of our results, we conclude that the condensate of spinors here studied could be an interesting candidate to explain the presence of dark energy in the early universe.

scholarly journals ON DETERMINATION OF THE GEOMETRIC COSMOLOGICAL CONSTANT FROM THE OPERA EXPERIMENT OF SUPERLUMINAL NEUTRINOS

2012 ◽  
Vol 27 (11) ◽  
pp. 1250041 ◽  
Author(s):  
MU-LIN YAN ◽  
SEN HU ◽  
WEI HUANG ◽  
NENG-CHAO XIAO
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Fundamental Constant ◽  
Zero Point ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Point Energy ◽  
Sitter Spacetime ◽  
Effective Cosmological Constant

The recent OPERA experiment of superluminal neutrinos has deep consequences in cosmology. In cosmology a fundamental constant is the cosmological constant. From observations one can estimate the effective cosmological constant Λ eff which is the sum of the quantum zero point energy Λ dark energy and the geometric cosmological constant Λ. The OPERA experiment can be applied to determine the geometric cosmological constant Λ. It is the first study to distinguish the contributions of Λ and Λ dark energy from each other by experiment. The determination is based on an explanation of the OPERA experiment in the framework of Special Relativity with de Sitter spacetime symmetry.

scholarly journals Graviton two-point function in 3 + 1 static de Sitter spacetime

2016 ◽  
Vol 25 (09) ◽  
pp. 1641016 ◽  
Author(s):  
Rafael P. Bernar ◽  
Luís C. B. Crispino ◽  
Atsushi Higuchi
Keyword(s):  
Vacuum State ◽  
De Sitter Spacetime ◽  
Cosmological Horizon ◽  
De Sitter ◽  
Point Function ◽  
Gauge Invariant ◽  
Gravitational Perturbations ◽  
Time Translation ◽  
Sitter Spacetime ◽  
Arbitrary Dimensions

In [R. P. Bernar, L. C. B. Crispino and A. Higuchi, Phys. Rev. D 90 (2014) 024045.] we investigated gravitational perturbations in the background of de Sitter spacetime in arbitrary dimensions. More specifically, we used a gauge-invariant formalism to describe the perturbations inside the cosmological horizon, i.e. in the static patch of de Sitter spacetime. After a gauge-fixed quantization procedure, the two-point function in the Bunch–Davies-like vacuum state was shown to be infrared finite and invariant under time-translation. In this work, we give details of the calculations to obtain the graviton two-point function in 3 + 1 dimensions.

scholarly journals Production of scalar particles in electric field on de Sitter expanding universe

2014 ◽  
Vol 29 (27) ◽  
pp. 1450138 ◽  
Author(s):  
Mihaela-Andreea Băloi
Keyword(s):  
Electric Field ◽  
Particle Production ◽  
Perturbation Methods ◽  
Transition Amplitude ◽  
Scalar Particle ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Scalar Particles ◽  
Sitter Spacetime ◽  
The Universe

The scalar particle production from vacuum in the presence of an electric field, on the de Sitter spacetime is studied. We use perturbation methods to define the transition amplitude. We obtain that the momentum is not conserved in this process. The probability density of pair production is computed by squaring the transition amplitude. Our graphical representations show that, the probability of scalar particle production was important only in the early stages of the universe, when Hubble's constant was very large in comparison with the mass of the particle. Also, we propose here a criterion for particle–antiparticle separation.

scholarly journals Dark energy and quantum gravity

2019 ◽  
Vol 28 (14) ◽  
pp. 1944018 ◽  
Author(s):  
Per Berglund ◽  
Tristan Hübsch ◽  
Djordje Minić
Keyword(s):  
Dark Energy ◽  
String Theory ◽  
Quantum Gravity ◽  
Cosmological Constant ◽  
Particle Physics ◽  
Dual Space ◽  
Planck Scale ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Sitter Spacetime

Realizing dark energy and the observed de Sitter spacetime in quantum gravity has proven to be obstructed in almost every usual approach. We argue that additional degrees of freedom of the left- and right-movers in string theory and a resulting doubled, noncommutatively generalized geometric formulation thereof can lead to an effective model of dark energy consistent with de Sitter spacetime. In this approach, the curvature of the canonically conjugate dual space provides for the dark energy inducing a positive cosmological constant in the observed spacetime, whereas the size of the above dual space is the gravitational constant in the same observed de Sitter spacetime. As a hallmark relation owing to a unique feature of string theory which relates short distances to long distances, the cosmological constant scale, the Planck scale and the effective TeV-sized particle physics scale must satisfy a see-saw-like formula — precisely the generic prediction of certain stringy cosmic brane type models.

scholarly journals Stringy Bubbles Solve de Sitter Troubles

Universe ◽  
2021 ◽  
Vol 7 (10) ◽  
pp. 363
Author(s):  
Per Berglund ◽  
Tristan Hübsch ◽  
Djordje Minic
Keyword(s):  
Bubble Nucleation ◽  
Recent Analysis ◽  
Mass Hierarchy ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Positive Cosmological Constant ◽  
Accelerating Expansion ◽  
Sitter Spacetime ◽  
Expansion Of The Universe ◽  
The Universe

Finding four-dimensional de Sitter spacetime solutions in string theory has been a vexing quest ever since the discovery of the accelerating expansion of the universe. Building on a recent analysis of bubble-nucleation in the decay of (false-vacuum) AdS backgrounds where the interfacing bubbles themselves exhibit a de Sitter geometry we show that this resonates strongly with a stringy cosmic brane construction that naturally provides for an exponential mass-hierarchy and the localization of both gravity and matter, in addition to an exponentially suppressed positive cosmological constant. Finally, we argue that these scenarios can be realized in terms of a generalization of a small resolution of a conifold singularity in the context of a (Lorentzian) Calabi–Yau 5-fold, where the isolated (Lorentzian) two complex dimensional Fano variety is a four-dimensional de Sitter spacetime.

Sign in / Sign up

Export Citation Format

Share Document