Abstract
We investigate harmonic functions and the convergence of the sequence of ratios \(({\mathbb {P}}_x(\tau _\vartheta> n)/{\mathbb {P}}_e(\tau _\vartheta > n))\) for a random walk on a countable group killed upon the time \(\tau _\vartheta \) of the first exit from some semigroup with an identity element e. Several results of classical renewal theory for one-dimensional random walk killed at the first exit from the positive half-line are extended to a multi-dimensional setting. For this purpose, an analogue of the ladder height process and the corresponding renewal function V are introduced. The results are applied to multi-dimensional random walks (X(t)) killed upon the times of first exit from a convex cone. Our approach combines large deviation estimates and an extension of Choquet–Deny theory.
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References
Sawyer, S.A.: Martin boundaries and random walks. Contemp. Math. 206(1), 17–44 (1997)
Doob, J.L.: Discrete potential theory and boundaries. J. Math. Mech. 8, 433–458 (1959)
Hunt, G.A.: Markoff chains and Martin boundaries. Ill. J. Math. 4, 313–340 (1960)
Dynkin, E.B.: Boundary theory of Markov processes. Russ. Math. Surv. 24(7), 1–42 (1969)
Bertoin, J., Doney, R.A.: On conditioning a random walk to stay nonnegative. Ann. Probab. 4, 2152–2167 (1994)
Denisov, D., Wachtel, V.: Random walks in cones. Ann. Probab. 43(3), 992–1044 (2015)
Raschel, K., Tarrago, P.: Martin boundary of random walks in convex cones. arXiv:1803.09253v2 [math.PR]
Spitzer, F.: Principles of Random Walk. Van Nostrand, Princeton (1964)
Feller, W.: An Introduction to Probability Theory and Its Applications, 2. Wiley Series in Probability, 2nd edn. Wiley, New York (1971)
Mogulskii, A.A., Pecherskii, E.A.: On the first exit time from a semigroup for a random walk. Theory Probab. Appl. 22, 818–825 (1977)
Greenwood, P., Shaked, M.: Fluctuation of random walks in Rd and storage systems. Adv. Appl. Prob. 9, 566–587 (1977)
Greenwood, P., Shaked, M.: Dual pairs of stopping times for random walk. Ann. Probab. 6(4), 644–650 (1978)
Kurkova, I.A., Malyshev, V.A.: Martin boundary and elliptic curves. Markov Process. Relat. Fields 4, 203–272 (1998)
Kurkova, I., Raschel, K.: Random walks in \({\mathbb{Z}}_+^2\) with non-zero drift absorbed at the axes. Bull. Soc. Math. Fr. 139, 341–387 (2011)
Raschel, K.: Random walks in the quarter plane, discrete harmonic functions and conformal mappings, with an appendix by Sandro Franceschi. Stoch. Process. Appl. 124, 3147–3178 (2014). MR-3231615
Ignatiouk-Robert, I., Loree, C.: Martin boundary of a killed random walk on a quadrant. Ann. Probab. 38(3), 1106–1142 (2010)
Ignatiouk-Robert, I.: Martin boundary of a killed random walk on \({\mathbb{Z}}_+^d\), pp. 1–49 (2009). arXiv:0909.3921
Aymen, B., Sami, M., Sifi, M.: Discrete harmonic functions on an orthant in \({\mathbb{Z}}^d\). Electron. Commun. Probab. 20(52), 1–13 (2015)
Gessel, I.M., Zeilberger, D.: Random walk in a Weyl chamber. Proc. Am. Math. Soc. 115, 27–31 (1992)
Grabiner, D.J., Magyar, P.: Random walks in Weyl chambers and the decomposition of tensor powers. J. Algebr. Combin. 2, 239–260 (1993)
Konig, W., Schmid, P.: Random walks conditioned to stay in Weyl chambers of type C and D. Electron. Commun. Probab. 15, 286–296 (2010)
Raschel, K.: Green functions and Martin compactification for killed random walks related to SU(3). Electron. Commun. Probab. 15, 176–190 (2010)
Raschel, K.: Green functions for killed random walks in the Weyl chamber of Sp(4). Ann. Inst. H. Poincaré Probab. Stat. 47, 1001–1019 (2011)
Duraj, J.: Random walks in cones: the case of nonzero drift. Stoch. Process. Appl. 124(4), 1503–1518 (2014)
Woess, W.: Random Walks on Infinite Graphs and Groups. Cambridge University Press, Cambridge (2000)
Dembo, A., Zeitouni, O.: Large Deviations Techniques and Applications. Springer, New York (1998)
Hennequin, P.L.: Processus de Markoff en cascade. Ann. Inst. H. Poincaré 18(2), 109–196 (1963)
Tyrrell Rockafellar, R.: Convex Analysis. Princeton University Press, Princeton, NJ (1997). (Reprint of the 1970 original, Princeton Paperbacks)
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Ignatiouk-Robert, I. Harmonic Functions of Random Walks in a Semigroup via Ladder Heights. J Theor Probab 34, 34–80 (2021). https://doi.org/10.1007/s10959-019-00974-1
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DOI: https://doi.org/10.1007/s10959-019-00974-1