Source: Adv. in Appl. Probab. Volume 42, Number 3
(2010), 689-705.
We consider a portfolio optimization problem in a defaultable market. The
investor can dynamically choose a consumption rate and allocate his/her wealth
among three financial securities: a defaultable perpetual bond, a default-free
risky asset, and a money market account. Both the default risk premium and the
default intensity of the defaultable bond are assumed to rely on some
stochastic factor which is described by a diffusion process. The goal is to
maximize the infinite-horizon expected discounted log utility of consumption.
We apply the dynamic programming principle to deduce a Hamilton-Jacobi-Bellman
equation. Then an optimal Markov control policy and the optimal value function
is explicitly presented in a verification theorem. Finally, a numerical
analysis is presented for illustration.
References
Biagini, F. and Cretarola, A. (2006). Local risk-minimization for defaultable claims with recovery process. Preprint. LMU University of München and University of Bologna.
Biagini, F. and Cretarola, A. (2007). Quadratic hedging methods for defaultable claims. Appl. Math. Optimization 56, 425--443.
Biagini, F. and Cretarola, A. (2009). Local risk minimization for defaultable markets. Math. Finance 19, 669--689.
Bielecki, T. R. and Jang, I. (2006). Portfolio optimization with a defaultable security. Asia-Pacific Financial Markets 13, 113--127.
Bielecki, T. R. and Rutkowski, M. (2002). Credit Risk: Modelling, Valuation and Hedging. Springer, Berlin.
Cox, J. C. and Huang, C.-F. (1989). Optimal consumption and portfolio policies when asset prices follow a diffusion process. J. Econom. Theory 49, 33--83.
Dellacherie, C. and Meyer, P.-A. (1982). Probabilities and Potential. B. North Holland, Amsterdam.
Mathematical Reviews (MathSciNet):
MR745449
Duffie, D. (2001). Dynamic Asset Pricing Theory, 3rd edn. Princeton University Press.
Duffie, D. and Singleton, K. J. (1999). Modeling term structures of defaultable bonds. Rev. Financial Studies 12, 687--720.
Fleming, W. H. and Hernández-Hernández, D. (2003). An optimal consumption model with stochastic volatility. Finance Stoch. 7, 245--262.
Fleming, W. H. and Pang, T. (2004). An application of stochastic control theory to financial economics. SIAM J. Control Optimization 43, 502--531.
Heston, S. L. (1993). A closed-form solution for options with stochastic volatility with applications to bond and currency options. Rev. Financial Studies 6, 327--343.
Ishikawa, Y. (2004). Optimal control problem associated with jump processes. Appl. Math. Optimization 50, 21--65.
Jang, I. (2005). Portfolio optimization with defaultable securities. Doctoral Thesis, University of Illinois at Chicago.
Jarrow, R. A., Lando, D. and Yu, F. (2005). Default risk and diversification: theory and empirical applications. Math. Finance 51, 1--26.
Jin, X. and Hou, Y. (2002). Optimal investment with default risk. FAME research paper no. 46, Switzerland.
Karatzas, I., Lehoczky, J. P. and Shreve, S. E. (1987). Optimal portfolio and consumption decisions for a `small investor' on a finite horizon. SIAM J. Control Optimization 27, 1557--1586.
Mathematical Reviews (MathSciNet):
MR912456
Korn, R. and Kraft, H. (2003). Optimal portfolios with defaultable securities: a firm value approach. Internat. J. Theory Appl. Finance 6, 793--819.
Merton, R. C. (1969). Lifetime portfolio selection under uncertainty: the continuous case. Rev. Econom. Statist. 51, 247--257.
Merton, R. C. (1971). Optimal consumption and portfolio rules in a continuous-time model. J. Econom. Theory 3, 373--413.
Mathematical Reviews (MathSciNet):
MR456373
Merton, R. C. (1992). Continuous-Time Finance. Blackwell, Oxford.
Pang, T. (2006). Stochastic portfolio optimization with log utility. Internat. J. Theory Appl. Finance 9, 869--887.
Pham, H. (2002). Smooth solutions to optimal investment methods with stochastic volatilities and portfolio constraints. Appl. Math. Optimization 46, 55--78.
Protter, P. (2004). Stochastic Integration and Differential Equations, 2nd edn. Springer, Berlin.