STOCHASTIC METHODS IN MATHEMATICAL FINANCE

 

Rome

September 15-17, 2005

 

                             Dedicated to Bruno Bassan

 

 

 

 

The conference will take place at the Department of Mathematics G.Castelnuovo, Universitą di Roma La Sapienza, and is supported by the MIUR2004 funds for the COFIN/PRIN project Metodi stocastici in finanza matematica

 

September 15. The following collaborators of Bruno Bassan will speak about the themes of their own collaboration with him: 
 

·         Claudia CeciUniversitą di Chieti: Optimal stopping and mixed problems with semicontinuous reward: regularity of the value function and viscosity solutions [abstract]

·         Isaco Meilijson, University of  Tel Aviv: Some stochastic orders related to portfolio diversification and to selective risk aversion [abstract]

·         Yoseph Rinott, University of  Jerusalem: Inference on multi-phase survival processes with incomplete data [abstract]

·         Marco ScarsiniUniversitą di Torino: Stochastic orders and lattices of probability measures [abstract and article]

·         Carlo Sempi, Universitą di Lecce: Semicopulę and their transforms [abstract]

Bruno Bassan

 

 

September 16-17.  The conference will include invited talks and short talks on finance, risk modelling, filtering and control theory, simulation.

The following invited speakers  have confirmed their participation:

·         Ruediger Frey, University of Leipzig: Pricing portfolio credit derivatives in a Markovian model of default interaction [abstract]

·         Frederic Patras, CNRS Nice and Zeliade systems: Correlation in the credit risk market: current trends and problems [abstract]

·         Maurizio PratelliUniversitą di Pisa: Merton's Mutual Fund Theorem: the classical version and some generalizations in infinite dimensional financial models [abstract]

 

No registration fee is requested but, please, register your participation by sending an e-mail including name, affiliation and e-mail address to  mestofin@mat.uniroma1.it

 

The following information are available:

                                                                PROGRAMME

                                                                ABSTRACTS

                                                                PARTICIPANTS (registered up to September 12)

                                                                SLIDES AND  PAPERS

 

Some additional information:

list of recommended hotels

how to reach the Campus of the University of Rome “La Sapienza”

the position of  the Department of Mathematics inside the Campus

 

For further information, please contact the organizers at mestofin@mat.uniroma1.it

 

The scientific committee:

Wolfgang Runggaldier (Padova), Paolo Baldi (Roma-Tor Vergata), Lucia Caramellino (Roma-Tor Vergata), Giovanna Nappo (Roma-La Sapienza), Fabio Spizzichino (Roma-La Sapienza)

 

The local organizing committee

Lucia Caramellino (Roma-Tor Vergata), Claudia Ceci (Pescara), Claudio Macci (Roma-Tor Vergata), Giovanna Nappo (Roma-La Sapienza), Fabio Spizzichino (Roma-La Sapienza), Gianluca Torrisi (IAC-CNR, Roma)

 

 

 

Optimal stopping and mixed problems with semicontinuous reward:

 regularity of the value function and viscosity solutions

Claudia Ceci

Universitą di Chieti

 

 

Abstract. We study optimal stopping problems for Markov processes with semicontinuous reward function. We give some results about the regularity of the value function and we show that, under suitable mild conditions on the underlying process, it has the same regularity of the reward function, namely, it is lower (respectively: upper) semicontinuous if the reward function is. Moreover, we show that, in the case of lower semicontinuous reward, under suitable conditions the value function is a (discontinuous) viscosity solution of the associated variational inequalities. We consider some classes of processes for which the sufficient conditions, which ensure the regularity of the value function are satisfied. We deal with diffusion processes, pure jump processes, jump diffusions and Lévy processes. Furthermore, we consider mixed control problems for diffusion processes, i.e. problems which involve both optimal control and stopping. The running reward is assumed to be smooth, but the stopping reward need only be semicontinuous. We give again some results about the regularity of the value function and we prove that, when the final reward is lower semicontinuous, the value function is a viscosity solution of the variational equation associated to   the mixed control problem.

 

References

1. B.Bassan-C.Ceci: An optimal stopping problem arising from a decision model with many agents. Probab. Engrg. Inform. Sci., 12, pp.1-16, 1998.

2. B.Bassan-C.Ceci: Optimal stopping with discontinuous reward: regularity of the value function and viscosity solution. Stochastics Stochastics Rep., 72, 55-77, 2002.

3. B.Bassan-C.Ceci: Regularity of the value function and viscosity solutions in optimal stopping problems for general Markov processes. Stochastics Stochastics Rep., 74, 633-649, 2002.

4. C.Ceci-B.Bassan: Viscosity approach for mixed control problems: semicontinuity of the stopping reward. Stochastics Stochastics Rep., 76, 323-337, 2004.

 

back

 

 

Some stochastic orders related to portfolio diversification and to selective risk aversion

Isaco Meilijson

University of  Tel Aviv

 

Abstract. Rothschild & Stiglitz (1971) showed that if Y is more dispersed than X in the second-degree (or Martingale dilation) sense, then although 

(i) the best portfolio between X and some constant interest rate is preferred by any risk averter to the best portfolio between Y and the same constant,

it may well happen that

(ii) the optimal fraction invested on Y may exceed the optimal fraction invested in X.

That is, the demand for the safer asset may be lower. 

This talk will review some stronger stochastic orders (Gollier, Landsberger, M., others) that better determine demand.  Some of these stochastic orders have applications to "selective risk aversion", as modelled by "star-shaped utilities", and to some interesting martingale material by Azema and by Yor. 

This subject, to be surveyed, was one of the my many joint interests with Bruno Bassan.

 

back

 

 

Inference on multi-phase survival processes with incomplete data

Yoseph Rinott

University of  Jerusalem

 

 

Abstract. Consider a life consisting of several phases (e.g., a disease which progresses in phases) and data obtained by intercepting the life process at a random time and following it for a limited time.  The data is therefore biased and censored. We obtain information on the phase at which a subject is intercepted, and perhaps on the past of the process. Using models (e.g., copulas) we wish to infer on the distribution of total life, and the joint distribution of the phases' durations. 

Based on joint works with Bruno Bassan, Micha Mandel, Yehuda Vardi and Cun-Hui Zhang.

 

back

 

 

Stochastic orders and lattices of probability measures

Marco Scarsini

Universitą di Torino

 

Abstract. We study various partially ordered spaces of probability measures and we determine which of them are lattices. This has important consequences for optimization problems with stochastic dominance constraints. In particular, we show that the space of probability measures on R is lattice under most of the known partial orders, whereas the space of probability measures on Rd typically is not. Nevertheless, some subsets of this space, defined by imposing strong conditions on the dependence structure of the measures, are lattices.

 

 

back

 


 

Semicopulę and their transforms

Carlo Sempi

Universitą di Lecce

 

 

Abstract. The concept of semicopula was introduced in the statistical literature by Bruno Bassan and Fabio Spizzichino. It generalizes the notions of quasi--copula and, hence of that of copula. Moreover, it is also related to the notion of triangular norm. Here we present the main properties of semicopulas, give several examples, show that they form a compact subset of the set of all functions from $[0,1]^2$ into $[0,1]$. and that they are a complete lattice when the natural pointwise order is considered. For the applications it is important to study the transformation

C_h (x,y) := h^{[-1]} C( h(x) , h(y) ),

where $C$ may be a semicopula, a quasi--copula or a copula.

This talk is a joint work with Fabrizio Durante.

 

back

 

 

 

Pricing portfolio credit derivatives in a Markovian model of default interaction

Ruediger Frey

University of Leipzig

 

Abstract. The market for portfolio credit derivatives has seen rapid growth in recent years. and dynamic models for portfolio credit risk have become indispensable tools for the pricing of these products. We discuss models  with default contagion, i.e.  models where the default of a firm has an impact on the default intensity of other firms in a portfolio. Particular emphasis will be given to  the pricing of portfolio credit derivatives such as CDOs in Markovian model for default contagion, which is an alternative to the copula models popular in industry.

Background information can be found in the forthcoming book "Quantitative Risk Management, Concepts, Techniques and Tools" by A. McNeil, R. Frey and P. Embrechts  (Princeton University Press 2005).

 

back

 


                                                                                                                                                                                

Correlation in the credit risk market: current trends and problems

Frederic Patras

CNRS Nice and Zeliade systems

 

Abstract. Due to the fast development of CDOs, n-to-default swaps and other so-called correlation products, the understanding and modelling of correlation, and particularly of defaults correlation, has become one of the leading problems for credit practitioners. The talk will concentrate mainly on CDOs and survey, besides the historical development of the financial products and models, some recent ideas in the field, such as stochastic correlation, the definition of local correlation or the dynamic modelling of defaults.

 

back

 


 

Merton's Mutual Fund Theorem: the classical version and some generalizations in infinite dimensional financial models

Maurizio Pratelli

Universitą di Pisa

 

 

Abstract. The original proof of the celebrated "Merton's mutual fund theorem" is based on stochastic control methods (solution of an Hamiton-Jacobi-Bellman equation): in this talk, I will show how an easy proof of this theorem can be given with "stochastic calculus" methods (representation of martingales in a Brownian filtration). This method can be applied to infinite dimensional situations: the so called "large financial markets" (where a sequence o assets is taken into account) and "bond markets" (where there is a continuum of assets). The talk will insist on related infinite-dimensional stochastic integration problems.

 

back