Finite-buffer workload rate truncation 2026-10-14
For the local convex action defining the linear workload rate for a local convex action, continuity and the contraction principle for large deviations give workload rate functions. The pointwise bound makes on nonnegative workloads. Constant-rate burst paths produce the reverse bound for x at most B. Values outside the buffer interval are impossible. This statement concerns the rate at the workload value, rather than equality of exact finite-buffer and infinite-buffer stationary distributions.
Local convex path action 2026-10-14
A local path action integrates a nonnegative convex cost g of the path's instantaneous input rate, assigning infinity to paths that are not absolutely continuous. When , the typical-rate path has zero cost. On any interval with prescribed total input, Jensen inequality makes a constant derivative minimize its cost. With a queue workload constraint this leads to constant-rate burst paths and the linear workload rate for a local convex action. Such a formula alone does not establish goodness in an unspecified path topology; goodness must be checked or assumed as part of the input large-deviation principle.
Past exam of the mathematics course of the University of Cambridge 2004 iii Paper 31 4 c Solution Created 2026-10-03 Updated 2026-10-14
Put and , allowing gamma to be infinity if no rate above C has finite cost. We prove the linear workload rate for a local convex action, which in particular proves monotonicity on the physical domain .
For an absolutely continuous finite-cost path and any interval of length t with positive net work , its average arrival rate is . Nonnegativity of g and Jensen inequality giveIf , choose intervals with approaching its supremum x, obtaining . If gamma is infinite, the existence of any positive net interval instead forces infinite cost, giving the same extended-value conclusion.
Conversely, choose any of finite cost, use arrival rate v during the last time units and the typical rate mu before that. This constant-rate burst path has queue workload exactly x: the lookback net input increases to x over the burst and then decreases with slope . Its action is . Taking the infimum over v proves the matching upper bound. The typical-rate path has zero queue workload and zero cost. ThereforeStrict convexity and ensure whenever it is finite. Indeed, choose a finite-cost and some ; then , and convexity gives for every finite-cost . Thus J is increasing on nonnegative queue workloads, and the preceding fiber bound yields . Negative values are impossible for both queue workloads and have infinite rate. No monotonicity is asserted across that impossible negative domain.