480 research outputs found
Exploiting the Synergy Between Gossiping and Structured Overlays
In this position paper we argue for exploiting the synergy between gossip-based algorithms and structured overlay networks (SON). These two strands of research have both aimed at building fault-tolerant, dynamic, self-managing, and large-scale distributed systems. Despite the common goals, the two areas have, however, been relatively isolated. We focus on three problem domains where there is an untapped potential of using gossiping combined with SONs. We argue for applying gossip-based membership for ring-based SONs---such as Chord and Bamboo---to make them handle partition mergers and loopy networks. We argue that small world SONs---such as Accordion and Mercury---are specifically well-suited for gossip-based membership management. The benefits would be better graph-theoretic properties. Finally, we argue that gossip-based algorithms could use the overlay constructed by SONs. For example, many unreliable broadcast algorithms for SONs could be augmented with anti-entropy protocols. Similarly, gossip-based aggregation could be used in SONs for network size estimation and load-balancing purposes
Phase transition in multi-scalar-singlet extensions of the Standard Model
We propose a generalization of the Standard Model (SM) by adding two real
gaugesinglets S1, S2. The field S1 will improve the strength of the electroweak
phase transition (EWPT). Imposing a Z2 symmetry on the field S2 makes this
field a possible candidate for dark matter. Both singlets interact with other
observable fields through Higgs boson. They are allowed to interact with each
other as well. We find that by introducing two different scalar fields, the
model is less vulnerable to experimental constraints. In this paper, we
consider the effects of a heavy scalar(M1 > MH) on the electroweak phase
transition. And we present configurations that produce a strong first order
EWPT
R^4 Corrections to D1D5p Black Hole Entropy from Entropy Function Formalism
We show that in IIB string theory and for D1D5p black holes in ten dimensions
the method of entropy function works. Despite the more complicated Wald formula
for the entropy of D1D5p black holes in ten dimensions, their entropy is given
by entropy function at its extremum point. We use this method for computing the
entropy of the system both at the level of supergravity and for its higher
order alpha'^3R^4 corrections.Comment: 15 pages, minor corrections, typos correcte
Gravity on Noncommutative D-Branes
The effective action for the low energy scattering of two gravitons with a
D-brane in the presence of a constant antisytmetric field in bosonic string
theory is calculated and the modification to the standard D-brane action to
first order in is obtained.Comment: 18 pages, Latex file, accepted in Int. J. Mod. Phys.
Inflation from D3-brane motion in the background of D5-branes
We study inflation arising from the motion of a BPS D3-brane in the
background of a stack of k parallel D5-branes. There are two scalar fields in
this set up-- (i) the radion field R, a real scalar field, and (ii) a complex
tachyonic scalar field chi living on the world volume of the open string
stretched between the D3 and D5 branes. We find that inflation is realized by
the potential of the radion field, which satisfies observational constraints
coming from the Cosmic Microwave Background. After the radion becomes of order
the string length scale l_s, the dynamics is governed by the potential of the
complex scalar field. Since this field has a standard kinematic term, reheating
can be successfully realized by the mechanism of tachyonic preheating with
spontaneous symmetry breaking.Comment: 10 pages, 4 figures. Minor clarifications and references added.
Version to appear in Phys. Rev.
OStrich: Fair Scheduling for Multiple Submissions
International audienceCampaign Scheduling is characterized by multiple job submissions issued from multiple users over time. This model perfectly suits today's systems since most available parallel environments have multiple users sharing a common infrastructure. When scheduling individually the jobs submitted by various users, one crucial issue is to ensure fairness. This work presents a new fair scheduling algorithm called OStrich whose principle is to maintain a virtual time-sharing schedule in which the same amount of processors is assigned to each user. The completion times in the virtual schedule determine the execution order on the physical processors. Then, the campaigns are interleaved in a fair way by OStrich. For independent sequential jobs, we show that OStrich guarantees the stretch of a campaign to be proportional to campaign's size and the total number of users. The stretch is used for measuring by what factor a workload is slowed down relative to the time it takes on an unloaded system. The theoretical performance of our solution is assessed by simulating OStrich compared to the classical FCFS algorithm, issued from synthetic workload traces generated by two different user profiles. This is done to demonstrate how OStrich benefits both types of users, in contrast to FCFS
Cosmological tests of sudden future singularities
We discuss combined constraints, coming from the cosmic microwave background
shift parameter , baryon acoustic oscillations (BAO) distance
parameter , and from the latest type Ia supernovae data, imposed
on cosmological models which allow sudden future singularities of pressure. We
show that due to their weakness such sudden singularities may happen in the
very near future and that at present they can mimic standard dark energy
models.Comment: 8 pages, 2 references adde
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