219 research outputs found
Two parallel insurance lines with simultaneous arrivals and risks correlated with inter-arrival times
We investigate an insurance risk model that consists of two reserves which
receive income at fixed rates. Claims are being requested at random epochs from
each reserve and the interclaim times are generally distributed. The two
reserves are coupled in the sense that at a claim arrival epoch, claims are
being requested from both reserves and the amounts requested are correlated. In
addition, the claim amounts are correlated with the time elapsed since the
previous claim arrival. We focus on the probability that this bivariate reserve
process survives indefinitely. The infinite- horizon survival problem is shown
to be related to the problem of determining the equilibrium distribution of a
random walk with vector-valued increments with reflecting boundary. This
reflected random walk is actually the waiting time process in a queueing system
dual to the bivariate ruin process. Under assumptions on the arrival process
and the claim amounts, and using Wiener-Hopf factor- ization with one
parameter, we explicitly determine the Laplace-Stieltjes transform of the
survival function, c.q., the two-dimensional equilibrium waiting time
distribution. Finally, the bivariate transforms are evaluated for some
examples, including for proportional reinsurance, and the bivariate ruin
functions are numerically calculated using an efficient inversion scheme.Comment: 24 pages, 6 figure
Queues and risk processes with dependencies
We study the generalization of the G/G/1 queue obtained by relaxing the
assumption of independence between inter-arrival times and service
requirements. The analysis is carried out for the class of multivariate matrix
exponential distributions introduced in [12]. In this setting, we obtain the
steady state waiting time distribution and we show that the classical relation
between the steady state waiting time and the workload distributions re- mains
valid when the independence assumption is relaxed. We also prove duality
results with the ruin functions in an ordinary and a delayed ruin process.
These extend several known dualities between queueing and risk models in the
independent case. Finally we show that there exist stochastic order relations
between the waiting times under various instances of correlation
Queues and risk models with simultaneous arrivals
We focus on a particular connection between queueing and risk models in a
multi-dimensional setting. We first consider the joint workload process in a
queueing model with parallel queues and simultaneous arrivals at the queues.
For the case that the service times are ordered (from largest in the first
queue to smallest in the last queue) we obtain the Laplace-Stieltjes transform
of the joint stationary workload distribution. Using a multivariate duality
argument between queueing and risk models, this also gives the Laplace
transform of the survival probability of all books in a multivariate risk model
with simultaneous claim arrivals and the same ordering between claim sizes.
Other features of the paper include a stochastic decomposition result for the
workload vector, and an outline how the two-dimensional risk model with a
general two-dimensional claim size distribution (hence without ordering of
claim sizes) is related to a known Riemann boundary value problem
Ruin excursions, the G/G/Infinity queue and tax payments in renewal risk models
In this paper we investigate the number and maximum severity of the ruin excursion of the insurance portfolio reserve process in the Cramer-Lundberg model with and without tax payments. We also provide a relation of the Cramer-Lundberg risk model with the G/G/infinity queue and use it to derive some explicit ruin probability formulae. Finally, the renewal risk model with tax is considered, and an asymptotic identity is derived that in some sense extends the tax identity of the Cramer-Lundberg risk model
Lévy-driven polling systems and continuous-state branching processes
In this paper we consider a ring of N = 1 queues served by a single server in a cyclic order. After having served a queue (according to a service discipline that may vary from queue to queue), there is a switch-over period and then the server serves the next queue and so forth. This model is known in the literature as a polling model.
Each of the queues is fed by a non-decreasing Lévy process, which can be different during each of the consecutive periods within the server's cycle. The N-dimensional Lévy processes obtained in this fashion are described by their (joint) Laplace exponent, thus allowing for non-independent input streams. For such a system we derive the steady-state distribution of the joint workload at embedded epochs, i.e. polling and switching instants. Using the Kella-Whitt martingale, we also derive the steady-state distribution at an arbitrary epoch.
Our analysis heavily relies on establishing a link between fluid (Lévy input) polling systems and multi-type Jirina processes (continuous-state discrete-time branching processes). This is done by properly defining the notion of the branching property for a discipline, which can be traced back to Fuhrmann and Resing. This definition is broad enough to contain the most important service disciplines, like exhaustive and gated
Convergence of the all-time supremum of a L\'evy process in the heavy-traffic regime
In this paper we derive a technique of obtaining limit theorems for suprema
of L\'evy processes from their random walk counterparts. For each , let
be a sequence of independent and identically distributed
random variables and be a L\'evy processes such that
, and as . Let .
Then, under some mild assumptions, , for some random variable and some function
. We utilize this result to present a number of limit theorems
for suprema of L\'evy processes in the heavy-traffic regime
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