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Tools to Estimate the First Passage Time to a Convex Barrier

Published online by Cambridge University Press:  14 July 2016

Ola Hammarlid*
Affiliation:
Stockholm University
*
Postal address: Department of Mathematics, Stockholm University, 106 91 Stockholm, Sweden. Email address: olah@math.su.se
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Abstract

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The first passage time of a random walk to a barrier (constant or concave) is of great importance in many areas, such as insurance, finance, and sequential analysis. Here, we consider a sum of independent, identically distributed random variables and the convex barrier cb(n/c), where c is a scale parameter and n is time. It is shown, using large-deviation techniques, that the limit distribution of the first passage time decays exponentially in c. Under a tilt of measure, which changes the drift, four properties are proved: the limit distribution of the overshoot is distributed as an overshoot over a linear barrier; the stopping time is asymptotically normally distributed when it is properly normalized; the overshoot and the asymptotic normal part are asymptotically independent; and the overshoot over a linear barrier is bounded by an exponentially distributed random variable. The determination of the function that multiplies the exponential part is guided by consideration of these properties.

Type
Research Papers
Copyright
© Applied Probability Trust 2005 

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