42,790 research outputs found
Diffusion approximation for a processor sharing queue in heavy traffic
Consider a single server queue with renewal arrivals and i.i.d. service times
in which the server operates under a processor sharing service discipline. To
describe the evolution of this system, we use a measure valued process that
keeps track of the residual service times of all jobs in the system at any
given time. From this measure valued process, one can recover the traditional
performance processes, including queue length and workload. We show that under
mild assumptions, including standard heavy traffic assumptions, the (suitably
rescaled) measure valued processes corresponding to a sequence of processor
sharing queues converge in distribution to a measure valued diffusion process.
The limiting process is characterized as the image under an appropriate lifting
map, of a one-dimensional reflected Brownian motion. As an immediate
consequence, one obtains a diffusion approximation for the queue length process
of a processor sharing queue
Monetary Policy and Public Finances: Inflation Targets in a New Perspective
This paper examines how the private sector, the monetary authority, and the fiscal authority interact and concludes that unrestricted central bank independence may not be an optimal way to collect seigniorage revenues or stabilize supply shocks. Moreover, the paper shows that the implementation of an optimal inflation target results in optimal shares of government finances--seigniorage, taxes, and the spending shortfall--from society's point of view but still involves suboptimal stabilization. Even if price stability is the sole central bank objective, a positive inflation target has important implications for the government's finances, as well as for stabilization. Copyright 1999, International Monetary Fund
Invariance of fluid limits for the Shortest Remaining Processing Time and Shortest Job First policies
We consider a single-server queue with renewal arrivals and i.i.d. service
times, in which the server employs either the preemptive Shortest Remaining
Processing Time (SRPT) policy, or its non-preemptive variant, Shortest Job
First (SJF). We show that for given stochastic primitives (initial condition,
arrival and service processes), the model has the same fluid limit under either
policy. In particular, we conclude that the well-known queue length optimality
of preemptive SRPT is also achieved, asymptotically on fluid scale, by the
simpler-to-implement SJF policy. We also conclude that on fluid scale, SJF and
SRPT achieve the same performance with respect to response times of the
longest-waiting jobs in the system.Comment: 24 page
Heavy traffic limit for a processor sharing queue with soft deadlines
This paper considers a GI/GI/1 processor sharing queue in which jobs have
soft deadlines. At each point in time, the collection of residual service times
and deadlines is modeled using a random counting measure on the right
half-plane. The limit of this measure valued process is obtained under
diffusion scaling and heavy traffic conditions and is characterized as a
deterministic function of the limiting queue length process. As special cases,
one obtains diffusion approximations for the lead time profile and the profile
of times in queue. One also obtains a snapshot principle for sojourn times.Comment: Published at http://dx.doi.org/10.1214/105051607000000014 in the
Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute
of Mathematical Statistics (http://www.imstat.org
Isoproterenol modulates insulin activation of insulin receptor kinase in intact rat adipocytes
Isoproterenol decreases activation by insulin of insulin receptor kinase in intact rat adipocytes
Casimir Scaling and String Breaking in G(2) Gluodynamics
We study the potential energy between static charges in G(2) gluodynamics in
three and four dimensions. Our work is based on an efficient local hybrid
Monte-Carlo algorithm and a multi-level L\"uscher-Weisz algorithm with
exponential error reduction to accurately measure expectation values of Wilson-
and Polyakov loops. Both in three and four dimensions we show that at
intermediate scales the string tensions for charges in various
G(2)-representations scale with the second order Casimir. In three dimensions
Casimir scaling is confirmed within one percent for charges in representations
of dimensions 7, 14, 27, 64, 77, 77', 182 and 189 and in 4 dimensions within 5
percent for charges in representions of dimensions 7, 14, 27 and 64. In three
dimensions we detect string breaking for charges in the two fundamental
representations. The scale for string breaking agrees very well with the mass
of the created pair of glue-lumps.Comment: 20 pages, 17 figure
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