9,211 research outputs found
Energy-aware dynamic pricing model for cloud environments
Energy consumption is a critical operational cost for Cloud providers. However, as commercial providers typically use fixed pricing schemes that are oblivious about the energy costs of running virtual machines, clients are not charged according to their actual energy impact. Some works have proposed energy-aware cost models that are able to capture each client’s real energy usage. However, those models cannot be naturally used for pricing Cloud services, as the energy cost is calculated after the termination of the service, and it depends on decisions taken by the provider, such as the actual placement of the client’s virtual machines. For those reasons, a client cannot estimate in advance how much it will pay. This paper presents a pricing model for virtualized Cloud providers that dynamically derives the energy costs per allocation unit and per work unit for each time period. They account for the energy costs of the provider’s static and dynamic energy consumption by sharing out them according to the virtual resource allocation and the real resource usage of running virtual machines for the corresponding time period. Newly arrived clients during that period can use these costs as a baseline to calculate their expenses in advance as a function of the number of requested allocation and work units. Our results show that providers can get comparable revenue to traditional pricing schemes, while offering to the clients more proportional prices than fixed-price models.Peer ReviewedPostprint (author's final draft
Charge breaking bounds in the Zee model
We study the possibility that charge breaking minima occur in the Zee model.
We reach very different conclusions from those attained in simpler, two Higgs
doublet models, and the reason for this is traced back to the existence of
cubic terms in the potential. A scan of the Zee model's parameter space shows
that CB is restricted to a narrow region of values of the parameters
Boundary conditions and renormalized stress-energy tensor on a Poincar\'e patch of
Quantum field theory on anti-de Sitter spacetime requires the introduction of
boundary conditions at its conformal boundary, due essentially to the absence
of global hyperbolicity. Here we calculate the renormalized stress-energy
tensor for a scalar field on the Poincar\'e patch of
and study how it depends on those boundary conditions. We show
that, except for the Dirichlet and Neumann cases, the boundary conditions break
the maximal invariance. As a result,
acquires a space dependence and is no longer
proportional to the metric. When the physical quantities are expanded in a
parameter which characterizes the boundary conditions (with
corresponding to Dirichlet and corresponding to Neumann), the
singularity of the Green's function is entirely subtracted at zeroth order in
. As a result, the contribution of nontrivial boundary conditions to the
stress-energy tensor is free of singular terms.Comment: 7 pages. Minor Correction. Matches published versio
A SAURON study of dwarf elliptical galaxies in the Virgo Cluster
Dwarf elliptical galaxies are the most common galaxy type in nearby galaxy
clusters, yet they remain relatively poorly studied objects and many of their
basic properties have yet to be quantified. In this contribution we present the
preliminary results of a study of 4 Virgo and 1 field galaxy obtained with the
SAURON integral field unit on the William Herschel Telescope (La Palma). While
traditional long-slit observations are likely to miss more complicated
kinematic features, with SAURON we are able to study both kinematics and
stellar populations in two dimensions, obtaining a much more detailed view of
the mass distribution and star formation histories.Comment: 2 pages, 1 figure; to appear in the proceedings of the conference "A
Universe of dwarf galaxies" (Lyon, June 14-18, 2010
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