Anomalous diffusion. A competition between the very large jumps in physical and operational times

In this paper we analyze a coupling between the very large jumps in physical and operational times as applied to anomalous diffusion. The approach is based on subordination of a skewed Levy-stable process by its inverse to get two types of operational time - the spent and the residual waiting time, respectively. The studied processes have different properties which display both subdiffusive and superdiffusive features of anomalous diffusion underlying the two-power-law relaxation patterns.Comment: 6 pages, 3 figures; corrected versio

Approximation of stochastic differential equations driven by alpha-stable Levy motion

In this paper we present a result on convergence of approximate solutions of stochastic differential equations involving integrals with respect to alpha-stable Levy motion. We prove an appropriate weak limit theorem, which does not follow from known results on stability properties of stochastic differential equations driven by semimartingales. It assures convergence in law in the Skorokhod topology of sequences of approximate solutions and justifies discrete time schemes applied in computer simulations. An example is included in order to demonstrate that stochastic differential equations with jumps are of interest in constructions of models for various problems arising in science and engineering, often providing better description of real life phenomena than their Gaussian counterparts. In order to demonstrate the usefulness of our approach, we present computer simulations of a continuous time alpha-stable model of cumulative gain in the Duffie–Harrison option pricing framework.Stable distribution, Simulation, Stochastic differential equation (SDE), Option pricing

The Lamperti transformation for self-similar processes

In this paper we establish the uniqueness of the Lamperti transformation leading from self-similar to stationary processes, and conversely. We discuss alpha-stable processes, which allow to understand better the difference between the Gaussian and non-Gaussian cases. As a by-product we get a natural construction of two distinct alpha-stable Ornstein–Uhlenbeck processes via the Lamperti transformation for 0Lamperti transformation; Self-similar process; Stationary process; Stable distribution;

Experimental Evidence of the Role of Compound Counting Processes in Random Walk Approaches to Fractional Dynamics

We present dielectric spectroscopy data obtained for gallium-doped Cd$_{0.99}$Mn$_{0.01}$Te:Ga mixed crystals which exhibit a very special case of the two-power-law relaxation pattern with the high-frequency power-law exponent equal to 1. We explain this behavior, which cannot be fitted by none of the well-known empirical relaxation functions, in a subordinated diffusive framework. We propose diffusion scenario based on a renormalized clustering of random number of spatio-temporal steps in the continuous time random walk. Such a construction substitutes the renewal counting process, used in the classical continuous time random walk methodology, by a compound counting one. As a result, we obtain a novel relaxation function governing the observed non-standard pattern, and we show the importance of the compound counting processes in studying fractional dynamics of complex systems.Comment: 6 pages, 5 figures; corrected versio

A new De Vylder type approximation of the ruin probability in infinite time

In this paper we introduce a generalization of the De Vylder approximation. Our idea is to approximate the ruin probability with the one for a different process with gamma claims, matching first four moments. We compare the two approximations studying mixture of exponentials and lognormal claims. In order to obtain exact values of the ruin probability for the lognormal case we use Pollaczeck-Khinchine formula. We show that the proposed 4-moment gamma De Vylder approximation works even better than the original one.Risk process; Ruin probability; De Vylder approximation; Pollaczeck-Khinchine formula;

Pure risk premiums under deductibles. A quantitative management in actuarial practice

It is common practice in most insurance lines for the coverage to be restricted by a deductible. In the paper we investigate the influence of deductibles on pure risk premiums. We derive simple but practical formulae for premiums under franchise, fix amount, proportional, limited proportional and disappearing deductibles in terms of the limited expected value function. Next, we apply the results to typical loss distributions, i.e. lognormal, Pareto, Burr, Weibull and gamma. Finally, we analyse a loss data of one of the power companies. We fit distributions to the data and show how the choice of the distribution and a deductible influences the premium.Insurance risk premium; Deductible; Limited expected value function;

On annuities under random rates of interest

In the article we consider accumulated values of annuities-certain with yearly payments with independent random interest rates. We focus on general annuities with payments varying in arithmetic and geometric progression which are important basic varying annuities (see Kellison, 1991). They are equivalent to the types studied recently by Zaks (2001). We derive, via recursive relationships, mean and variance formulae of the final values of the annuities. As a consequence, we obtain the moments related to the already discussed cases, which leads to a correction of main results from Zaks (2001).Finance mathematics; Annuity; Accumulated value; Random interest rate;