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sparse grid method in the libor market model. option valuation and the

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Chapter 2<br />

Asset Pric<strong>in</strong>g Overview<br />

The most important goal of Derivative F<strong>in</strong>ance is f<strong>in</strong>d<strong>in</strong>g <strong>the</strong> fair price of a cont<strong>in</strong>gent<br />

claim. In this chapter, we will provide a brief <strong>in</strong>troduction to discrete <strong>and</strong> cont<strong>in</strong>uous<br />

<strong>model</strong>s used <strong>in</strong> this area of applied ma<strong>the</strong>matics, def<strong>in</strong>e <strong>the</strong> notion of no-arbitrage <strong>market</strong>s,<br />

risk-neutral world <strong>and</strong> replicat<strong>in</strong>g portfolios. The last section is go<strong>in</strong>g to prepare<br />

<strong>the</strong> ground for fur<strong>the</strong>r discussion of LIBOR <strong>market</strong> <strong>model</strong> by putt<strong>in</strong>g <strong>option</strong> <strong>valuation</strong><br />

<strong>in</strong>to a more general framework of mart<strong>in</strong>gales <strong>and</strong> measures.<br />

2.1 Arbitrage <strong>and</strong> Risk-Neutral World<br />

Simple Market In order to <strong>in</strong>troduce several important concepts, we will start with<br />

a very simple sett<strong>in</strong>g. The <strong>market</strong> should consist of only two assets: zero-coupon 1<br />

cash bond B, <strong>and</strong> a stock S. The evolution of <strong>the</strong>se two assets can be observed at<br />

two discrete time po<strong>in</strong>ts: <strong>the</strong> current moment T 0 <strong>and</strong> <strong>the</strong> time of <strong>option</strong> maturity T 1 .<br />

As cont<strong>in</strong>uously-compounded <strong>in</strong>terest rates are assumed to be constant, <strong>the</strong>re is no<br />

uncerta<strong>in</strong>ty about <strong>the</strong> value of B at T 1 . The price of <strong>the</strong> stock, on <strong>the</strong> o<strong>the</strong>r h<strong>and</strong>, is<br />

subject to uncerta<strong>in</strong>ty <strong>and</strong> evolves to one of <strong>the</strong> two possible states: ”up” - <strong>the</strong> stock<br />

price <strong>in</strong>creases <strong>and</strong> ”down” - <strong>the</strong> stock price goes down. The <strong>market</strong>, described above,<br />

is known as a one-step b<strong>in</strong>ary <strong>model</strong>.<br />

Inspired by [E<strong>the</strong>rage, 2002], this view of <strong>the</strong> economy can be presented <strong>in</strong> <strong>the</strong><br />

matrix-vector form. Prices of N assets at T 0 are denoted by vector I; values of N<br />

assets be<strong>in</strong>g <strong>in</strong> n possible states at T 1 are <strong>in</strong>corporated <strong>in</strong>to matrix D. Specifically for<br />

our case, I <strong>and</strong> D take <strong>the</strong> follow<strong>in</strong>g form:<br />

I =<br />

(<br />

S0<br />

B 0<br />

)<br />

(<br />

up down<br />

)<br />

S0 u S<br />

D =<br />

0 d<br />

B 0 e rT B 0 e rT<br />

where r - is <strong>the</strong> risk-free rate, u <strong>and</strong> d coefficients correspond to <strong>the</strong> upward <strong>and</strong> downward<br />

price movements of S 0 with u > e rT > d.<br />

1 provid<strong>in</strong>g no <strong>in</strong>terim coupon payments.<br />

3

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