75 research outputs found
QoE-centric management of advanced multimedia services
Over the last years, multimedia content has become more prominent than ever. Particularly, video streaming is responsible for more than a half of the total global bandwidth consumption on the Internet. As the original Internet was not designed to deliver such real-time, bandwidth-consuming applications, a serious challenge is posed on how to efficiently provide the best service to the users. This requires a shift in the classical approach used to deliver multimedia content, from a pure Quality of Service (QoS) to a full Quality of Experience (QoE) perspective. While QoS parameters are mainly related to low-level network aspects, the QoE reflects how the end-users perceive a particular multimedia service. As the relationship between QoS parameters and QoE is far from linear, a classical QoS-centric delivery is not able to fully optimize the quality as perceived by the users. This paper provides an overview of the main challenges this PhD aims to tackle in the field of end-to-end QoE optimization of video streaming services and, more precisely, of HTTP Adaptive Streaming (HAS) solutions, which are quickly becoming the de facto standard for video delivery over the Internet
Orbits of particles in noncommutative Schwarzschild spacetime
By considering particles as smeared objects, we investigate the effects of
space noncommutativity on the orbits of particles in Schwarzschild spacetime.
The effects of space noncommutativity on the value of the precession of the
perihelion of particle orbit and deflection of light ray in Schwarzschild
geometry are calculated and the stability of circular orbits is discussed.Comment: 14 Pages, 2 eps Figures, accepted for publication in Europhysics
Letter
On the Stability of Planetary Circular Orbits in Noncommutative Spaces
We investigate the effects of space noncommutativity and the generalized
uncertainty principle on the stability of circular orbits of particles in both
a central force potential and Schwarzschild spacetime. We find noncommutative
form of the effective potential which up to first order of noncommutativity
parameter contains an angular momentum dependent extra term. This angular
momentum dependent extra term affects the stability of circular orbits in such
a way that the radius of a stable circular orbit in noncommutative space is
larger than its commutative counterpart. In the case of large angular momentum,
the condition for stability of circular orbits in noncommutative space differs
considerably from commutative case.Comment: 21 pages, 6 figures, revised versio
Evolution of Perturbations in a Noncommutative Braneworld Inflation
Following our previous work in noncommutative braneworld inflation
(arXiv:0911.4418), in this paper we use the smeared, coherent state picture of
noncommutativity to study evolution of perturbations in a noncommutative
braneworld scenario. We show that in this setup, the early stage of the
universe evolution has a phantom evolution with imaginary effective sound
speed. We show also that the amplitude of perturbations in the commutative
regime decays faster than the noncommutative regime with the same parameter
values, and as a result we need smaller number of e-folds in the noncommutative
regime to have a successful braneworld inflation.Comment: 13 pages, 3 figure
Inflation by spin and torsion in Poincare gauge theory of gravity
In Poincare gauge theory of gravity, in addition to mass-energy content, spin
is also a source for gravitational interactions. Although the effects of spin
are negligible at low energies, they can play a crucial role at very early
universe when the spin density was very high. In this paper by choosing a
suitable Lagrangian for Poincare gauge theory of gravity, and suitable
energy-momentum and spin density tensors, we show that the effects of spin and
torsion can lead to a inflationary phase without the need for any additional
fields. No fine tuning of parameters is required in this setup. We also
calculate the scalar spectral index at the end of inflation and show that it
agrees with the most recent observational data.Comment: 7 pages, 8 figures, Accepted for publication in EP
Braneworld setup and embedding in teleparallel gravity
We construct the setup of a five-dimensional braneworld scenario in
teleparallel gravity. Both cases of Minkowski and Friedmann-Robertson-Walker
branes embedded in Anti de Sitter bulk are studied and the effective 4-D action
were studied. 4-dimensional local Lorentz invariance is found to be recovered
in both cases. However, due to different junction conditions, the equations
governing the 4-D cosmological evolution differ from general relativistic case.
Using the results of Ref. [13], we consider a simple inflationary scenario in
this setup. The inflation parameters are found to be modified compared to
general relativistic case.Comment: 21 pages, no figure, Title Changed, Accepted for Publication in Phys.
Lett.
Braneworld Teleparallel Gravity
We study the gravity in the context of a braneworld teleparallel scenario.
The geometrical setup is assumed to be Randall-Sundrum II model where a single
positive tension brane is embedded in an infinite AdS bulk. We derive the
equivalent of Gauss-Codacci equations in teleparallel gravity and junction
conditions in this setup. Using these results we derive the induced
teleparallel field equations on the brane. We show that compared to general
relativity, the induced field equations in teleparallel gravity contain two
extra terms arising from the extra degrees of freedom in the teleparallel
Lagrangian. The term carrying the effects of the bulk to the brane is also
calculated and its implications are discussed.Comment: 7 pages, no figur
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