scholarly journals Observational constraints on the braneworld model with branebulk energy exchange

2008 ◽  
Vol 388 (1) ◽  
pp. 197-210 ◽  
Author(s):  
M. Sadegh Movahed ◽  
Ahmad Sheykhi
2010 ◽  
Vol 25 (01) ◽  
pp. 171-183 ◽  
Author(s):  
R. ZARROUKI ◽  
Z. SAKHI ◽  
M. BENNAI

We study a new inflation potential in the framework of the Randall–Sundrum type II braneworld model. Using the technic developed in Ref. 1, we consider both a monomial and a new inflation potentials and apply the slow-roll approximation in high energy limit, to derive analytical expression of relevant perturbation spectrum. We show that for some values of the parameter n in the potential [Formula: see text] we obtain a perturbation spectrum which gives a good agreement with the recent WMAP5 observations.


2012 ◽  
Vol 27 (36) ◽  
pp. 1250205 ◽  
Author(s):  
A. SAFSAFI ◽  
A. BOUAOUDA ◽  
H. CHAKIR ◽  
J. INCHAOUH ◽  
M. BENNAI

We consider a supersymmetric hybrid inflation in the framework of the Randall–Sundrum type-2 braneworld model. We derive an analytical expression for the effective scalar potential and find that the D-term dominates hybrid inflation process. We show that we can eliminate partially the fine tuning problem related to coupling constant λ of the potential and calculate the value of FI-term ξ according to recent WMAP7 observation data. We show also that some inflationary spectrum parameters, in particular, the ratio r and the running [Formula: see text] are widely consistent with WMAP7, BAO and H0 data.


2005 ◽  
Vol 22 (4) ◽  
pp. 315-325 ◽  
Author(s):  
Luke Barnes ◽  
Matthew J. Francis ◽  
Geraint F. Lewis ◽  
Eric V. Linder

AbstractObservational evidence indicating that the expansion of the universe is accelerating has surprised cosmologists in recent years. Cosmological models have sought to explain this acceleration by incorporating ‘dark energy’, of which the traditional cosmological constant is just one possible candidate. Several cosmological models involving an evolving equation of state of the dark energy have been proposed, as well as possible energy exchange to other components, such as dark matter. This paper summarizes the forms of the most prominent models and discusses their implications for cosmology and astrophysics. Finally, this paper examines the current and future observational constraints on the nature of dark energy.


2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Hussain Gohar ◽  
Vincenzo Salzano

AbstractWe investigate entropic force cosmological models with the possibility of matter creation and energy exchange between the bulk and the horizon of a homogeneous and isotropic flat Universe. We consider three different kinds of entropy, Bekenstein’s, the non-extensive Tsallis–Cirto’s, and the quartic entropy, plus some phenomenological functional forms for matter creation rate to model different entropic force models and put the observational constraints on them. We show that while most of them are indistinguishable from a standard $$\Lambda $$ Λ CDM scenario, the Bekenstein entropic force model with a matter creation rate proportional to the Hubble parameter is statistically highly favored over $$\Lambda $$ Λ CDM. As a general result, we also find that both the Hawking temperature parameter $$\gamma $$ γ , which relates the energy exchange between the bulk and the boundary of the Universe, and the matter creation rate $$\Gamma (t)$$ Γ ( t ) , must be very small to reproduce observational data.


Impact ◽  
2019 ◽  
Vol 2019 (10) ◽  
pp. 73-75
Author(s):  
Susumu Hara

Professor Susumu Hara is based at the Department of Aerospace Engineering, Nagoya University in Japan explains that when the Mars rover Opportunity was set to land on that planet in the first weeks of 2004, onlookers held their breath as it dropped from orbit and hurtled toward the red surface. 'Any failure in the calculations or landing systems would mean a harder than expected impact,' he highlights. 'The impacts sustained by a rover such as Opportunity can derail a mission before it even starts, damaging cargo or vital systems required to complete the mission.' Impacts occur during landing but also as the craft enters the atmosphere, when it makes sudden moves, while it is on surface or when debris strikes it. 'Therefore, a system and materials to protect a craft are vital,' outlines Hara. 'Surprisingly, the solutions to this problem are not sophisticated. In fact, most craft still employ devices resembling automobile bumpers, which absorb the energy from an impact by crumpling under the force of said impact.' Unfortunately, these cannot be reused, even during testing phases a new prototype is required after every single test run. Recent missions also employed techniques like airbags or sky cranes. While successful they too have drawbacks. 'Airbags create huge rebounds which can jostle the craft and the contents inside while sky cranes are extremely costly to develop,' Hara says. For this reason, he is dedicated to designing a new highly reliable and cost-effective shock control mechanism.


1999 ◽  
Vol 516 (2) ◽  
pp. 939-945 ◽  
Author(s):  
Th. Straus ◽  
G. Severino ◽  
F.‐L. Deubner ◽  
B. Fleck ◽  
S. M. Jefferies ◽  
...  

1998 ◽  
Vol 495 (2) ◽  
pp. 609-616 ◽  
Author(s):  
Kyu‐Hyun Chae ◽  
David A. Turnshek ◽  
Valery K. Khersonsky

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