Cosmography with the Hubble Rate: The Eis Approach

2017 ◽  
pp. 393-405
Author(s):  
Jaime Klapp ◽  
Alejandro Aviles ◽  
Orlando Luongo
Keyword(s):  
Hubble Rate

Constraining the early Hubble rate using Cosmic Antiprotons

2007 ◽  
Vol 173 ◽  
pp. 56-59
Author(s):  
Mia Schelke ◽  
Riccardo Catena ◽  
Nicolao Fornengo ◽  
Antonio Masiero ◽  
Massimo Pietroni
Keyword(s):  
Hubble Rate

scholarly journals POSSIBLY LARGE CORRECTIONS TO THE INFLATIONARY OBSERVABLES

2008 ◽  
Vol 23 (12) ◽  
pp. 857-862 ◽  
Author(s):  
N. BARTOLO ◽  
A. RIOTTO
Keyword(s):  
Second Order ◽  
Hubble Rate ◽  
Slow Roll ◽  
Theoretical Predictions

We point out that the theoretical predictions for the inflationary observables may be generically altered by the presence of fields which are heavier than the Hubble rate during inflation and whose dynamics is usually neglected. They introduce corrections which may be easily larger than both the second-order contributions in the slow-roll parameters and the accuracy expected in the forthcoming experiments.

scholarly journals The Hubble rate in averaged cosmology

2011 ◽  
Vol 2011 (03) ◽  
pp. 029-029 ◽  
Author(s):  
Obinna Umeh ◽  
Julien Larena ◽  
Chris Clarkson
Keyword(s):  
Hubble Rate

scholarly journals The little sibling of the big rip singularity

2015 ◽  
Vol 24 (10) ◽  
pp. 1550078 ◽  
Author(s):  
Mariam Bouhmadi-López ◽  
Ahmed Errahmani ◽  
Prado Martín-Moruno ◽  
Taoufik Ouali ◽  
Yaser Tavakoli
Keyword(s):  
Blow Up ◽  
Energy Condition ◽  
Cosmic Time ◽  
Energy Conditions ◽  
Accelerating Universe ◽  
Hubble Rate ◽  
Big Rip ◽  
The Status ◽  
The Universe ◽  
Nonlinear Energy

In this paper, we present a new cosmological event, which we named the little sibling of the big rip. This event is much smoother than the big rip singularity. When the little sibling of the big rip is reached, the Hubble rate and the scale factor blow up, but the cosmic derivative of the Hubble rate does not. This abrupt event takes place at an infinite cosmic time where the scalar curvature explodes. We show that a doomsday à la little sibling of the big rip is compatible with an accelerating universe, indeed at present it would mimic perfectly a ΛCDM scenario. It turns out that, even though the event seems to be harmless as it takes place in the infinite future, the bound structures in the universe would be unavoidably destroyed on a finite cosmic time from now. The model can be motivated by considering that the weak energy condition should not be strongly violated in our universe, and it could give us some hints about the status of recently formulated nonlinear energy conditions.

scholarly journals Dark matter freeze-out during matter domination

2018 ◽  
Vol 33 (29) ◽  
pp. 1850181 ◽  
Author(s):  
Saleh Hamdan ◽  
James Unwin
Keyword(s):  
Dark Matter ◽  
Energy Density ◽  
Big Bang ◽  
Big Bang Nucleosynthesis ◽  
Hubble Rate ◽  
Dark Matter Relic Density ◽  
Relic Density ◽  
The Masses ◽  
The Universe ◽  
Freeze Out

We highlight the general scenario of dark matter freeze-out while the energy density of the universe is dominated by a decoupled non-relativistic species. Decoupling during matter domination changes the freeze-out dynamics, since the Hubble rate is parametrically different for matter and radiation domination. Furthermore, for successful Big Bang Nucleosynthesis the state dominating the early universe energy density must decay, this dilutes (or repopulates) the dark matter. As a result, the masses and couplings required to reproduce the observed dark matter relic density can differ significantly from radiation-dominated freeze-out.

Thermal relics

2018 ◽  
Author(s):  
Michael Kachelriess
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Dark Matter Particle ◽  
Big Bang ◽  
Matter Density ◽  
Light Elements ◽  
Big Bang Nucleosynthesis ◽  
Boltzmann Equations ◽  
Hubble Rate ◽  
Dark Matter Density

The Boltzmann equations, which describe processes as diverse as the evolution of the dark matter density, big bang nucleosynthesis or recombination, are derived. The Gamov criterion states that processes freeze-out when their rate becomes smaller than the Hubble rate. It is demonstrated that the mass of any thermal relic is bounded by ≲ 20TeV, while the abundance of a cold dark matter particle with 〈σ‎v〉 ≃ 3 × 10−26 cm3/s corresponds to the observed one, Ω‎CDM = 0.2. Big bang nucleosynthesis, which successfully explains the abundance of light elements like D and 4He, is discussed.

scholarly journals Dynamical dark energy: Scalar fields and running vacuum

2017 ◽  
Vol 32 (09) ◽  
pp. 1750054 ◽  
Author(s):  
Joan Solà ◽  
Adrià Gómez-Valent ◽  
Javier de Cruz Pérez
Keyword(s):  
Dark Energy ◽  
Scalar Fields ◽  
Cosmic Acceleration ◽  
Field Approach ◽  
Hubble Rate ◽  
Representative Model ◽  
Cosmological Data ◽  
Energy Scalar ◽  
Dynamical Dark Energy ◽  
Better Than

Recent analyses in the literature suggest that the concordance [Formula: see text]CDM model with rigid cosmological term, [Formula: see text] may not be the best description of the cosmic acceleration. The class of “running vacuum models”, in which [Formula: see text] evolves with the Hubble rate, has been shown to fit the string of SNIa + BAO + H(z) + LSS + CMB data significantly better than the [Formula: see text]CDM. Here, we provide further evidence on the time-evolving nature of the dark energy (DE) by fitting the same cosmological data in terms of scalar fields. As a representative model, we use the original Peebles and Ratra potential, [Formula: see text]. We find clear signs of dynamical DE at [Formula: see text] c.l., thus reconfirming through a nontrivial scalar field approach the strong hints formerly found with other models and parametrizations.

scholarly journals Dark Matter and Baryon Asymmetry from the very Dawn of Universe

2018 ◽  
Vol 191 ◽  
pp. 08002
Author(s):  
Sabir Ramazanov
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Baryon Asymmetry ◽  
Complex Scalar ◽  
Hubble Rate ◽  
Baryon Charge ◽  
Complex Scalar Field

We discuss a possibility of universally producing dark matter and baryon charge at inflation. For this purpose, we introduce a complex scalar field with the mass exceeding the Hubble rate during the last e-folds of inflation. We assume that the phase of the complex scalar is linearly coupled to the inflaton. This interaction explicitly breaking U(1)-symmetry leads to the production of a non-zero Noether charge. The latter serves as a source of dark matter abundance, or baryon asymmetry, if the complex scalar carries the baryon charge.

scholarly journals GENERALISED COSMOLOGY OF CODIMENSION-TWO BRANEWORLDS

2004 ◽  
Vol 19 (31) ◽  
pp. 5295-5302 ◽  
Author(s):  
JÉRÉMIE VINET
Keyword(s):  
Cosmological Constant ◽  
Static Solution ◽  
Brane Tension ◽  
Cosmological Constant Problem ◽  
Brane Model ◽  
Codimension Two ◽  
Hubble Rate ◽  
Tuning Mechanism ◽  
Self Tuning ◽  
Promising Line

It has recently been argued that codimension-two braneworlds offer a promising line of attack on the cosmological constant problem, since in such models the Hubble rate is not directly related to the brane tension. We point out challenges to building more general models where the brane content is not restricted to pure tension. In order to address these challenges, we construct a thick brane model which we linearize around a well known static solution. We show that the model's cosmology does reduce to standard FRW behaviour, but find no hint of a self-tuning mechanism which might help solve the cosmological constant problem whithin the context of non-supersymmetric Einstein gravity.

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