Background mode selection during asymptotic-de Sitter inflation

2021 ◽  
Vol 36 (13) ◽  
pp. 2150094
Author(s):  
A. R. Ziyaee ◽  
M. Mohsenzadeh ◽  
E. Yusofi
Keyword(s):  
Mode Selection ◽  
Particle Creation ◽  
Flat Space ◽  
De Sitter ◽  
Flat Background ◽  
Number Problem ◽  
Minimum Number ◽  
Background Mode ◽  
First Time ◽  
Number Of Particles

For the first time, we choose non-flat vacuum mode for background spacetime based on the minimum number of created particles during early non-de Sitter inflation. In conventional methods for calculating the number of created particles, the flat background is selected automatically and causes a negative number problem for created particles during asymptotic-de Sitter inflation. In a covariant approach to curved spacetime, both real and background spacetimes should be selected, curved and consequently the relation for particle creation should be modify. As an interesting finding from this research, flat space does not include minimum number of particles and there are some asymptotic de Sitter spacetimes with fewer number. Therefore, in the generalized formula for particle creation, we choose a non-flat background containing the minimum number of created particles.

Massive fermion particle production in de Sitter universe: Ambient space approach

2014 ◽  
Vol 29 (10) ◽  
pp. 1450051 ◽  
Author(s):  
Sepideh Mirabi
Keyword(s):  
Particle Production ◽  
Particle Creation ◽  
Flat Space ◽  
Ambient Space ◽  
Quantum Field ◽  
De Sitter ◽  
Spin Particle ◽  
Massive Spin ◽  
De Sitter Universe ◽  
Space Approach

In this paper, we study the massive spin-½ particle creation in de Sitter (dS) space where the related fields are written in (4+1)-dimensional bulk or the so-called ambient space approach. This approach mimics the flat space quantum field theory (QFT) and the field operators are defined globally on dS space. The main purpose of this study is defining the |in〉 and |out〉 modes for the proposed quantum field which has been written in terms of the dS plane wave in the 4+1 dimensions. We compute, via the Bogoliubov coefficients, the rate of particle creation in dS universe.

scholarly journals Particle creation in global de Sitter space: Bulk space consideration

2015 ◽  
Vol 24 (07) ◽  
pp. 1550052 ◽  
Author(s):  
M. Reza Tanhayi
Keyword(s):  
Plane Wave ◽  
Massive Particle ◽  
Particle Creation ◽  
Flat Space ◽  
De Sitter Space ◽  
Point Of View ◽  
Theoretical Point ◽  
De Sitter ◽  
Field Equations ◽  
Higher Spin

Recently in [P. R. Anderson and E. Mottola, Phys. Rev. D 89 (2014) 104039, arXiv:1310.1963 [gr-qc] and P. R. Anderson and E. Mottola, Phys. Rev. D 89 (2014) 104038, arXiv:1310.0030 [gr-qc].], it was shown that global de Sitter space is unstable even to the massive particle creation with no self-interactions. In this paper, we study the instability by making use of the coordinate-independent plane wave in de Sitter space. Within this formalism, we show that the previous results of instability of de Sitter space due to the particle creation can be generalized to higher-spin fields in a straightforward way. The so-called plane wave is defined globally in de Sitter space and de Sitter invariance is manifest since such modes are deduced from the group theoretical point of view by means of the Casimir operators. In fact, we employ the symmetry of embedding space namely the 4 + 1-dimensional flat space to write the field equations and the solutions can be obtained in terms of the plane wave in embedding space.

scholarly journals 6d (2, 0) and M-theory at 1-loop

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Luis F. Alday ◽  
Shai M. Chester ◽  
Himanshu Raj
Keyword(s):  
Flat Space ◽  
Lagrangian Description ◽  
Loop Correction ◽  
Higher Derivative ◽  
Weakly Coupled ◽  
S Matrix ◽  
Space Limit ◽  
Tensor Multiplet ◽  
First Time ◽  
M Theory

Abstract We study the stress tensor multiplet four-point function in the 6d maximally supersymmetric (2, 0) AN−1 and DN theories, which have no Lagrangian description, but in the large N limit are holographically dual to weakly coupled M-theory on AdS7× S4 and AdS7× S4/ℤ2, respectively. We use the analytic bootstrap to compute the 1-loop correction to this holographic correlator coming from Witten diagrams with supergravity R and the first higher derivative correction R4 vertices, which is the first 1-loop correction computed for a non-Lagrangian theory. We then take the flat space limit and find precise agreement with the corresponding terms in the 11d M-theory S-matrix, some of which we compute for the first time using two-particle unitarity cuts.

scholarly journals Period-Life of a Branching Process with Migration and Continuous Time

Mathematics ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 868
Author(s):  
Khrystyna Prysyazhnyk ◽  
Iryna Bazylevych ◽  
Ludmila Mitkova ◽  
Iryna Ivanochko
Keyword(s):  
Random Process ◽  
Generating Function ◽  
Continuous Time ◽  
Branching Process ◽  
Probability Generating Function ◽  
Time Interval ◽  
The Moment ◽  
First Time ◽  
Critical Branching Process ◽  
Number Of Particles

The homogeneous branching process with migration and continuous time is considered. We investigated the distribution of the period-life τ, i.e., the length of the time interval between the moment when the process is initiated by a positive number of particles and the moment when there are no individuals in the population for the first time. The probability generating function of the random process, which describes the behavior of the process within the period-life, was obtained. The boundary theorem for the period-life of the subcritical or critical branching process with migration was found.

scholarly journals Bra-ket wormholes in gravitationally prepared states

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Yiming Chen ◽  
Victor Gorbenko ◽  
Juan Maldacena
Keyword(s):  
Hyperbolic Space ◽  
Path Integral ◽  
Flat Space ◽  
Low Energy ◽  
Two Dimensional ◽  
De Sitter ◽  
Euclidean Case ◽  
Fine Grained ◽  
Entropy Formula ◽  
First Case

Abstract We consider two dimensional CFT states that are produced by a gravitational path integral.As a first case, we consider a state produced by Euclidean AdS2 evolution followed by flat space evolution. We use the fine grained entropy formula to explore the nature of the state. We find that the naive hyperbolic space geometry leads to a paradox. This is solved if we include a geometry that connects the bra with the ket, a bra-ket wormhole. The semiclassical Lorentzian interpretation leads to CFT state entangled with an expanding and collapsing Friedmann cosmology.As a second case, we consider a state produced by Lorentzian dS2 evolution, again followed by flat space evolution. The most naive geometry also leads to a similar paradox. We explore several possible bra-ket wormholes. The most obvious one leads to a badly divergent temperature. The most promising one also leads to a divergent temperature but by making a projection onto low energy states we find that it has features that look similar to the previous Euclidean case. In particular, the maximum entropy of an interval in the future is set by the de Sitter entropy.

scholarly journals Mass in de Sitter and Anti-de Sitter Universes with Regard to Dark Matter

Universe ◽  
2020 ◽  
Vol 6 (5) ◽  
pp. 66 ◽  
Author(s):  
Jean-Pierre Gazeau
Keyword(s):  
Dark Matter ◽  
Irreducible Representation ◽  
Flat Space ◽  
Space Time ◽  
Energy Scale ◽  
Unitary Irreducible Representation ◽  
Poincaré Group ◽  
De Sitter ◽  
Rest Energy ◽  
Poincare Group

An explanation of the origin of dark matter is suggested in this work. The argument is based on symmetry considerations about the concept of mass. In Wigner’s view, the rest mass and the spin of a free elementary particle in flat space-time are the two invariants that characterize the associated unitary irreducible representation of the Poincaré group. The Poincaré group has two and only two deformations with maximal symmetry. They describe respectively the de Sitter (dS) and anti-de Sitter (AdS) kinematic symmetries. Analogously to their shared flat space-time limit, two invariants, spin and energy scale for de Sitter and rest energy for anti-de Sitter, characterize the unitary irreducible representation associated with dS and AdS elementary systems, respectively. While the dS energy scale is a simple deformation of the Poincaré rest energy and so has a purely mass nature, AdS rest energy is the sum of a purely mass component and a kind of zero-point energy derived from the curvature. An analysis based on recent estimates on the chemical freeze-out temperature marking in Early Universe the phase transition quark–gluon plasma epoch to the hadron epoch supports the guess that dark matter energy might originate from an effective AdS curvature energy.

scholarly journals COVARIANT REPRESENTATIONS OF THE DE SITTER ISOMETRY GROUP

2013 ◽  
Vol 28 (09) ◽  
pp. 1350033 ◽  
Author(s):  
ION I. COTĂESCU
Keyword(s):  
General Theory ◽  
Isometry Group ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Induced Representations ◽  
Covariant Representations ◽  
Sitter Spacetime ◽  
Technical Details ◽  
First Time

We show that the induced representations of the de Sitter isometry group proposed many years ago by Nachtmann are equivalent to those derived from our general theory of external symmetry. These methods complete each other leading to a coherent theory of covariant fields with spin on the de Sitter spacetime. Some technical details of these representations are presented here for the first time.

A new analytical model for reliability analysis of a launch vehicle system with limited test data

2018 ◽  
Vol 233 (9) ◽  
pp. 3482-3495
Author(s):  
V Murugesan ◽  
Sreejith Plappillimadam ◽  
VJ Saji ◽  
SS Maruthi ◽  
AK Anilkumar
Keyword(s):  
Reliability Analysis ◽  
Analytical Model ◽  
Test Data ◽  
Weighting Factor ◽  
Design Parameters ◽  
Launch Vehicles ◽  
Minimum Number ◽  
First Time ◽  
Propellant Rocket

Reliability is one of the critical design parameters for the launch vehicles and its systems. When the systems are ready to fly the first time, only limited test data are available and accordingly reliability assessed will be very low. However, in most cases, the new systems are derived and developed using the knowledge and experience gained from the heritage systems to meet the fresh challenges. Hence, the reliability assessed with the minimum number of tests done on the new system does not truly reflect the inherent reliability of the system. In this paper, an approach and a new analytical model are developed for the reliability assessment of systems with limited test data, giving an accurate weighting for the tests and flight experiences with similar systems. The method gives a systematic procedure for arriving at the weighting factor for test data of the pedigree system, with due consideration of the similarities between the systems and various factors influencing system reliability. The method is illustrated with a case study of a newly developed liquid propellant rocket system. The model is validated using the available test and flight data of two propulsion systems with adequate flight experience. The analytical model is generic in nature and can be applied to reliability analysis of any system, which has considerable similarities with a pedigree system.

scholarly journals Every timelike geodesic in Anti-de Sitter spacetime is a circle of the same radius

2016 ◽  
Vol 25 (01) ◽  
pp. 1650007 ◽  
Author(s):  
Leszek M. Sokołowski ◽  
Zdzisław A. Golda
Keyword(s):  
Flat Space ◽  
De Sitter Space ◽  
Ambient Space ◽  
Alternative Proof ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Timelike Geodesic ◽  
Sitter Spacetime

In this paper, we refine and analytically prove an old proposition due to Calabi and Markus on the shape of timelike geodesics of anti-de Sitter space in the ambient flat space. We prove that each timelike geodesic forms in the ambient space a circle of the radius determined by [Formula: see text], lying on a Euclidean two-plane. Then, we outline an alternative proof for [Formula: see text]. We also make a comment on the shape of timelike geodesics in de Sitter space.

Particle creation in de Sitter space

1985 ◽  
Vol 31 (4) ◽  
pp. 754-766 ◽  
Author(s):  
E. Mottola
Keyword(s):  
Particle Creation ◽  
De Sitter Space ◽  
De Sitter
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