geometric asian options pricing under the double heston...

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Research Article Geometric Asian Options Pricing under the Double Heston Stochastic Volatility Model with Stochastic Interest Rate Yanhong Zhong and Guohe Deng College of Mathematics and Statistics, Guangxi Normal University, Guilin , China Correspondence should be addressed to Guohe Deng; [email protected] Received 16 August 2018; Revised 6 December 2018; Accepted 24 December 2018; Published 10 January 2019 Academic Editor: Hassan Zargarzadeh Copyright Β© 2019 Yanhong Zhong and Guohe Deng. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. is paper presents an extension of double Heston stochastic volatility model by incorporating stochastic interest rates and derives explicit solutions for the prices of the continuously monitored fixed and floating strike geometric Asian options. e discounted joint characteristic function of the log-asset price and its log-geometric mean value is computed by using the change of numeraire and the Fourier inversion transform technique. We also provide efficient approximated approach and analyze several effects on option prices under the proposed model. Numerical examples show that both stochastic volatility and stochastic interest rate have a significant impact on option values, particularly on the values of longer term options. e proposed model is suitable for modeling the longer time real-market changes and managing the credit risks. 1. Introduction Asian option is a special type of option contract in which the payoff depends on the average of the underlying asset price over some predetermined time interval. e averaging feature allows Asian options to reduce the volatility inherent in the option. ere are some advantages to trading Asian options in a financial market. One is that these decrease the risk of market manipulation of the financial derivative at expiry. Another is that Asian options have lower relative charge than European or American options. In general, the average considered can be a arithmetic or geometric one and it can be calculated either discretely, for which the average is taken over the underlying asset prices at discrete monitoring time points, or continuously, for which the average is calculated via the integration of the underlying asset price over the monitoring time period. Asian options can be differentiated into two main classes according to their payoff: fixed strike price options (sometimes called β€œaverage price”) and floating strike price options (sometimes called β€œaverage strike”). All these details are specified by the contracts stipulated by two counterparts, as Asian options are traded actively on the OTC market among investors or traders for hedging the average price of a commodity. For a brief introduction to the development of Asian options, see Boyle and Boyle [1]. As the probability distribution of the average prices of the underlying asset generally does not have a simple analytical expression, it is difficult to obtain the analytical pricing formula for Asian option. Since the best-known closed-form pricing formula for the European vanilla option derived by Black and Scholes [2]), many researchers have devoted themselves to developing the Asian options pricing based on the Black-Scholes assumptions; see, e.g., Kemna and Vorst (1990), Turnbull and Wakeman [3], Ritchken et al. [4], Geman and Yor [5], Rogers and Shi [6], Boyle et al. [7], Angus [8], Linetsky [9], Cui et al. [10], and the references therein. For a recent review, one can refer to Fusai and Roncoroni [11] and Sun et al. [12]. In practice, the Black-Scholes assumptions are hardly sat- isfied, especially the constant volatility and constant interest rate hypothesis. As the empirical behaviors of the implied volatility smile and heavy tailed in the distribution of log- returns are commonly observed in financial markets. For Hindawi Complexity Volume 2019, Article ID 4316272, 13 pages https://doi.org/10.1155/2019/4316272

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  • Research ArticleGeometric Asian Options Pricing under the Double HestonStochastic Volatility Model with Stochastic Interest Rate

    Yanhong Zhong and Guohe Deng

    College of Mathematics and Statistics, Guangxi Normal University, Guilin 541004, China

    Correspondence should be addressed to Guohe Deng; [email protected]

    Received 16 August 2018; Revised 6 December 2018; Accepted 24 December 2018; Published 10 January 2019

    Academic Editor: Hassan Zargarzadeh

    Copyright Β© 2019 Yanhong Zhong and Guohe Deng. This is an open access article distributed under the Creative CommonsAttribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work isproperly cited.

    This paper presents an extension of double Heston stochastic volatility model by incorporating stochastic interest rates and derivesexplicit solutions for the prices of the continuously monitored fixed and floating strike geometric Asian options. The discountedjoint characteristic function of the log-asset price and its log-geometric mean value is computed by using the change of numeraireand the Fourier inversion transform technique. We also provide efficient approximated approach and analyze several effects onoption prices under the proposed model. Numerical examples show that both stochastic volatility and stochastic interest rate havea significant impact on option values, particularly on the values of longer term options.The proposedmodel is suitable formodelingthe longer time real-market changes and managing the credit risks.

    1. Introduction

    Asian option is a special type of option contract in which thepayoff depends on the average of the underlying asset priceover somepredetermined time interval.The averaging featureallows Asian options to reduce the volatility inherent in theoption. There are some advantages to trading Asian optionsin a financial market. One is that these decrease the riskof market manipulation of the financial derivative at expiry.Another is that Asian options have lower relative chargethan European or American options. In general, the averageconsidered can be a arithmetic or geometric one and it canbe calculated either discretely, for which the average is takenover the underlying asset prices at discrete monitoring timepoints, or continuously, for which the average is calculatedvia the integration of the underlying asset price over themonitoring time period. Asian options can be differentiatedinto two main classes according to their payoff: fixed strikeprice options (sometimes called β€œaverage price”) and floatingstrike price options (sometimes called β€œaverage strike”). Allthese details are specified by the contracts stipulated bytwo counterparts, as Asian options are traded actively on

    the OTC market among investors or traders for hedgingthe average price of a commodity. For a brief introductionto the development of Asian options, see Boyle and Boyle[1].

    As the probability distribution of the average prices of theunderlying asset generally does not have a simple analyticalexpression, it is difficult to obtain the analytical pricingformula for Asian option. Since the best-known closed-formpricing formula for the European vanilla option derivedby Black and Scholes [2]), many researchers have devotedthemselves to developing the Asian options pricing based onthe Black-Scholes assumptions; see, e.g., Kemna and Vorst(1990), Turnbull andWakeman [3], Ritchken et al. [4], Gemanand Yor [5], Rogers and Shi [6], Boyle et al. [7], Angus [8],Linetsky [9], Cui et al. [10], and the references therein. For arecent review, one can refer to Fusai and Roncoroni [11] andSun et al. [12].

    In practice, the Black-Scholes assumptions are hardly sat-isfied, especially the constant volatility and constant interestrate hypothesis. As the empirical behaviors of the impliedvolatility smile and heavy tailed in the distribution of log-returns are commonly observed in financial markets. For

    HindawiComplexityVolume 2019, Article ID 4316272, 13 pageshttps://doi.org/10.1155/2019/4316272

    http://orcid.org/0000-0002-9344-5193https://creativecommons.org/licenses/by/4.0/https://creativecommons.org/licenses/by/4.0/https://doi.org/10.1155/2019/4316272

  • 2 Complexity

    this reason, stochastic volatility (hereafter SV) models havebeen proposed in finance (see Hull and White [13], Steinand Stein [14], Heston [15], and others). These models havebeen applied to value the Asian options (see, e.g., Wongand Cheung [16], Hubalek and Sgarra [17], Kim and Wee[18], and Shi and Yang [19]). In addition, interest rates arestochastic and stock returns are negatively correlated withinterest rate changes, which have been examined in previousresearch.

    Although these models mentioned above are able toaccount for the empirical behaviors, they are still based on asingle-factor for volatility dynamics that is inconsistent withthe long range memory characteristic of the volatility correc-tions and the stiff volatility skews. See Alizadeh et al. [20],Fiorentini et al. [21], Chernov et al. [22], Gourieroux [23],Christoffersen et al. [24], Romo [25], and Nagashima et al.[26] for the empirical results. To address this issue, mul-tifactor SV models have recently generated attention inthe option pricing literature. For instance, Duffie et al.[27] proposed multifactor affine stochastic volatility models.Based upon the Black-Scholes framework, Fouque et al. [28]introduced a multiscale SV model, in which the volatilityprocesses are driven by two mean-reverting diffusion pro-cesses. Gourieroux [23] proposed a multivariate model inwhich the volatility-covolatility matrix follows a Wishartprocess.

    On the basis of the findings of Christoffersen et al. [24],a double Heston (dbH) model, which consists of two inde-pendent variance processes, has recently been reported betterthan the plain Heston [15] model in the performances ofhedging (see Sun [29]) and has also been applied to arithmeticAsian option under discrete monitoring (Mehrdoust andSaber [30]) and forward starting option (Zhang and Sun [31]).However, its extension to continuously monitored geometricAsian option is yet to be considered. On the other hand,many of Asian options often have long-dated maturities sincethey are used as part of the structured notes which has along maturity. The movement of interest rates becomes anissue in such cases and constant interest rate assumptionshould be replaced by an appropriate dynamic interest ratemodel. Several results are available on the Asian option inthe stochastic interest rate framework; see, e.g., Nielsen andSandmann [32, 33], Zhang et al. [34], Donnelly et al. [35],and He and Zhu [36]. In the above stochastic interest rateframework, the short-term interest rate is assumed to followa specific parametric one-factor model (see, e.g., Cox et al.[37], Hull and White [13], and Vasicek [38]), which tendsto oversimplify the true behavior of interest rate movement.However, empirical tests reported in Lonstaff and Schwartz[39] and Pearson and Sun [40] show that the term struc-ture for the interest rate should involve several sources ofuncertainty, and introducing additional state variables (suchas the rate of inflation, GDP, etc.) significantly improves thefit.

    In this paper, we study the pricing of the continuouslymonitored geometric Asian options under dbH stochasticvolatility model with stochastic interest rate framework(hereafter, dbH-SI model). The contribution of the present

    paper is twofold. Firstly, this paper extends the dbH modelby introducing stochastic interest rate, which is assumed tofollow two-factor model with two state variables. Secondly,this paper provides a semiexplicit valuation formula for thegeometric Asian options with fixed or floating strike price,which is extremely useful also for the arithmetic averageoption valuation via Monte Carlo methods with controlvariables.

    The rest of the paper is organized as follows. Section 2develops the underlying pricing model and describes thegeometric Asian option. Section 3 derives the joint char-acteristic function of a log-return of the underlying assetand its geometric average. Section 4 obtains the analyticexpressions for the prices of the fixed strike geometric Asiancall option and the floating strike Asian call option undercontinuous monitoring. Section 5 provides some numericalexamples for the proposed approach. Section 6 concludes thepaper.

    2. Model Formulation

    We consider an arbitrage-free, frictionless financial marketwhere only riskless asset and risky asset are traded continu-ously up to a fixed horizon date 𝑇. Let (Ξ©,F, {F𝑑}0≀𝑑≀𝑇, 𝑄)be a complete probability space equipped with a filtration{F𝑑} satisfying the usual conditions, where𝑄 is a risk-neutralprobability measure. Suppose π‘Šπ‘—π‘‘ and 𝑍𝑗𝑑 (𝑗 = 1, 2) are allstandard Brownian motions defined on the probability space,and the filtration {F𝑑}𝑑β‰₯0 is generated by these Brownianmotions. Moreover, π‘‘π‘Š1𝑑 𝑑𝑍1𝑑 = 𝜌1𝑑𝑑, π‘‘π‘Š2𝑑 𝑑𝑍2𝑑 = 𝜌2𝑑𝑑,and any other Brownian motions are pairwisely independent.Assume that the asset price process 𝑆𝑑, without payingany dividend, satisfies the following stochastic differentialequation under 𝑄:

    𝑑𝑆𝑑𝑆𝑑 = π‘Ÿπ‘‘π‘‘π‘‘ + √V1π‘‘π‘‘π‘Š1𝑑 + √V2π‘‘π‘‘π‘Š2𝑑 ,𝑑V1𝑑 = πœ…1 (πœƒ1 βˆ’ V1𝑑) 𝑑𝑑 + 𝜎1√V1𝑑𝑑𝑍1𝑑 ,𝑑V2𝑑 = πœ…2 (πœƒ2 βˆ’ V2𝑑) 𝑑𝑑 + 𝜎2√V2𝑑𝑑𝑍2𝑑 ,

    (1)

    where πœ…π‘—, πœƒπ‘—, πœŽπ‘— (𝑗 = 1, 2) are all nonnegative constants,which represent the mean-reverting rates, long-term meanlevels, and volatilities of variance processes V𝑗𝑑, respectively.We suppose that 2πœ…π‘—πœƒπ‘— β‰₯ 𝜎2𝑗 . The instantaneous interestrate, π‘Ÿπ‘‘, is assumed to be a linear combination of V1𝑑 andV2𝑑, i.e., π‘Ÿπ‘‘ = V1𝑑 + V2𝑑, which designates the interest rateas an affine function of two-factor economic variables V1and V2 and offers the analytic tractability (see Duffie et al.[27]).

    In financial market, there are four types of Europeanstyle continuously monitoring geometric Asian options: fixedstrike geometric Asian calls, fixed strike geometric Asianputs, floating strike geometric Asian calls, and floating strikegeometric Asian puts.The payoffs at the expiration date 𝑇 forthese options are as follows:

  • Complexity 3

    β„Ž (𝑆𝑇, 𝐺[0,𝑇]) ={{{{{{{{{{{{{{{{{

    max {𝐺[0,𝑇] βˆ’ 𝐾, 0} , a fixed strike geometric Asian calls,max {𝐾 βˆ’ 𝐺[0,𝑇], 0} , a fixed strike geometric Asian puts,max {𝐺[0,𝑇] βˆ’ 𝑆𝑇, 0} , a floating strike geometric Asian calls,max {𝑆𝑇 βˆ’ 𝐺[0,𝑇], 0} , a floating strike geometric Asian puts,

    (2)

    where 𝐾 is a fixed strike price and 𝐺[0,𝑇] is the geometricaverage of the underlying asset price 𝑆𝑑 until time 𝑇; i.e.,𝐺[0,𝑇] = exp((1/𝑇) βˆ«π‘‡0 ln 𝑆𝑒𝑑𝑒). In the following, we consideronly the pricing problem of the geometric Asian call options(hereafter, GAC), while the put options can be dealt withsimilarly.

    For the instantaneous interest rate π‘Ÿπ‘‘ = V1𝑑 + V2𝑑, onecan express the price at time 𝑑 of a zero-coupon bond withmaturate 𝑇 as follows (see Cox et al. [37]):

    𝑃 (𝑑, 𝑇) = exp {π‘Ž (𝑑, 𝑇) βˆ’ 𝑏 (𝑑, 𝑇) π‘Ÿπ‘‘} , (3)where

    π‘Ž (𝑑, 𝑇) = 2βˆ‘π‘—=1

    [πœ…π‘—πœƒπ‘— (πœ…π‘— βˆ’ 𝛾𝑗) (𝑇 βˆ’ 𝑑)𝜎2𝑗+ 2πœ…π‘—πœƒπ‘—πœŽ2𝑗 ln

    2𝛾𝑗2𝛾𝑗 + (πœ…π‘— βˆ’ 𝛾𝑗) (1 βˆ’ π‘’βˆ’π›Ύπ‘—(π‘‡βˆ’π‘‘))] ,

    𝑏 (𝑑, 𝑇) = 2βˆ‘π‘—=1

    [ 2 (1 βˆ’ π‘’βˆ’π›Ύπ‘—(π‘‡βˆ’π‘‘))2𝛾𝑗 + (πœ…π‘— βˆ’ 𝛾𝑗) (1 βˆ’ π‘’βˆ’π›Ύπ‘—(π‘‡βˆ’π‘‘))] ,𝛾𝑗 = βˆšπœ…2𝑗 + 2𝜎2𝑗 , for 𝑗 = 1, 2.

    (4)

    3. The Joint Characteristic Function

    Given the dynamic of the underlying asset price, it is possibleto obtain the discounted joint characteristic function for thelog-asset value 𝑆𝑇 and the log-geometric mean value of theasset price over a certain time period.

    Let πœ“π‘‘(𝑠, 𝑀) = 𝐸𝑄[π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπœπ‘‘πœ+𝑠 ln𝐺[𝑑,𝑇]+𝑀 ln 𝑆𝑇 | F𝑑] be thediscounted joint characteristic function of two-dimensionalrandom variable, (ln𝐺[𝑑,𝑇], ln 𝑆𝑇), conditioned on F𝑑 under𝑄, where𝐺[𝑑,𝑇] = exp{(1/𝑇) βˆ«π‘‡π‘‘ ln 𝑆𝑒𝑑𝑒} and 𝐸𝑄[β‹… | F𝑑] is theconditional expectation under 𝑄 for 𝑑 ∈ [0, 𝑇]. Denote 𝐷 ={(𝑠, 𝑀) ∈ C2 : R(𝑠) β‰₯ 0,R(𝑀) β‰₯ 0, 0 ≀ R(𝑠) +R(𝑀) ≀ 1}.Proposition 1. Suppose that 𝑆𝑑, V1𝑑, and V2𝑑 follow thedynamics in (1). If (𝑠, 𝑀) ∈ 𝐷 and 𝑑 ∈ [0, 𝑇], then𝐸𝑄[|π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπœπ‘‘πœ+𝑠 ln𝐺[𝑑,𝑇]+𝑀 ln 𝑆𝑇 |] < ∞ and

    πœ“π‘‘ (𝑠, 𝑀) = 𝑒𝑔0𝐸𝑄[[exp{{{2βˆ‘π‘—=1

    [𝑔𝑗1 βˆ«π‘‡π‘‘(𝑇 βˆ’ 𝜏)2 Vπ‘—πœπ‘‘πœ + 𝑔𝑗2 βˆ«π‘‡

    𝑑(𝑇 βˆ’ 𝜏) Vπ‘—πœπ‘‘πœ + 𝑔𝑗3 βˆ«π‘‡

    𝑑Vπ‘—πœπ‘‘πœ + 𝑔𝑗4V𝑗𝑇]}}} | V1𝑑, V2𝑑

    ]] , (5)

    where

    𝑔0 = 𝑔0 (𝑠, 𝑀) = 𝑠[[𝑇 βˆ’ 𝑑𝑇 ln 𝑆𝑑

    βˆ’ 1𝑇2βˆ‘π‘—=1

    (πœŒπ‘—πœ…π‘—πœƒπ‘—2πœŽπ‘— (𝑇 βˆ’ 𝑑)2 +πœŒπ‘— (𝑇 βˆ’ 𝑑)πœŽπ‘— V𝑗𝑑)]]

    + 𝑀[[ln 𝑆𝑑 βˆ’2βˆ‘π‘—=1

    (πœŒπ‘—πœ…π‘—πœƒπ‘—πœŽπ‘— (𝑇 βˆ’ 𝑑) +πœŒπ‘—πœŽπ‘— V𝑗𝑑)]] ,

    𝑔𝑗1 = 𝑔𝑗1 (𝑠, 𝑀) = 𝑠2 (1 βˆ’ 𝜌2𝑗 )2𝑇2 ,

    𝑔𝑗2 = 𝑔𝑗2 (𝑠, 𝑀) = 𝑠 (2πœŒπ‘—πœ…π‘— + πœŽπ‘—)2πœŽπ‘—π‘‡ +𝑠𝑀 (1 βˆ’ 𝜌2𝑗 )𝑇 ,

    𝑔𝑗3 = 𝑔𝑗3 (𝑠, 𝑀) = π‘ πœŒπ‘—π‘‡πœŽπ‘— +𝑀 (2πœŒπ‘—πœ…π‘— + πœŽπ‘—)2πœŽπ‘—

    + 𝑀2 (1 βˆ’ 𝜌2𝑗 )2 βˆ’ 1,𝑔𝑗4 = 𝑔𝑗4 (𝑠, 𝑀) = π‘€πœŒπ‘—πœŽπ‘— .

    (6)

  • 4 Complexity

    Proof. (i) We first prove that the integrability conditionguarantees the existence of the cumulant function πœ“π‘‘(𝑠, 𝑀) in𝐷. If (𝑠, 𝑀) ∈ 𝐷 and 𝑑 ∈ [0, 𝑇), then

    𝐸𝑄 [π‘’βˆ’βˆ«π‘‡

    π‘‘π‘Ÿπœπ‘‘πœ+𝑠ln𝐺[𝑑,𝑇]+𝑀ln𝑆𝑇

    ]= 𝑃 (𝑑, 𝑇) 𝐸𝑄𝑇 [𝑒𝑠ln𝐺[𝑑,𝑇]+𝑀ln𝑆𝑇 ]≀ 𝑃 (𝑑, 𝑇) 𝐸𝑄𝑇 [ 1𝑇 βˆ’ 𝑑 ∫

    𝑇

    𝑑𝑆𝑒𝑑𝑒 + 𝑆𝑇]

    = [ 1𝑇 βˆ’ 𝑑 βˆ«π‘‡

    𝑑

    𝑃 (𝑑, 𝑇)𝑃 (𝑑, 𝑒) 𝑑𝑒 + 1] 𝑆𝑑 < ∞,

    (7)

    where 𝑄𝑇 is the π‘‡βˆ’ forward measure given by the Radon-Nikodym derivative: (𝑑𝑄𝑇/𝑑𝑄)|F𝑇 = exp{βˆ’ βˆ«π‘‡0 π‘Ÿπ‘’π‘‘π‘’}/𝑃(0, 𝑇), and 𝑃(𝑑, 𝑇) is given above in (3). In the case of 𝑑 = 𝑇,it is triviality.

    (ii) In order to determine (5), we start from model(1) and develop ln 𝑆𝑇 with the Brownian motions π‘Š1𝑑 andπ‘Š2𝑑 expressed as π‘Š1𝑑 = 𝜌1𝑍1𝑑 + √1 βˆ’ 𝜌12𝑍1𝑑 and π‘Š2𝑑 =𝜌1𝑍2𝑑 + √1 βˆ’ 𝜌22𝑍2𝑑 , respectively, where (𝑍1𝑑 , 𝑍2𝑑 , 𝑍1𝑑 , 𝑍2𝑑 ) are4-dimensional Brownian motion defined on the probabilityspace. For the process, ln 𝑆𝑇, we have

    ln 𝑆𝑇 = ln 𝑆𝑑 + 2βˆ‘π‘—=1

    [βˆ’πœŒπ‘—πœ…π‘—πœƒπ‘—πœŽπ‘— (𝑇 βˆ’ 𝑑) βˆ’πœŒπ‘—πœŽπ‘— V𝑗𝑑

    + (πœŒπ‘—πœ…π‘—πœŽπ‘— +12)βˆ«π‘‡

    𝑑Vπ‘—πœπ‘‘πœ + πœŒπ‘—πœŽπ‘— V𝑗𝑇

    + √1 βˆ’ 𝜌2𝑗 βˆ«π‘‡π‘‘βˆšVπ‘—πœπ‘‘π‘π‘—πœ] = ln 𝑆𝑑 + 2βˆ‘

    𝑗=1[πœƒπ‘—2 (𝑇 βˆ’ 𝑑)

    + V𝑗𝑑2πœ…π‘— βˆ’V𝑗𝑇2πœ…π‘— + (πœŒπ‘— +

    πœŽπ‘—2πœ…π‘—)βˆ«π‘‡

    π‘‘βˆšVπ‘—πœπ‘‘π‘π‘—πœ

    + √1 βˆ’ 𝜌2𝑗 βˆ«π‘‡π‘‘βˆšVπ‘—πœπ‘‘π‘π‘—πœ] .

    (8)

    On the other hand, we have

    ln𝐺[𝑑,𝑇] = 𝑇 βˆ’ 𝑑𝑇 ln 𝑆𝑑 + 1𝑇2βˆ‘π‘—=1

    [πœƒπ‘—4 (𝑇 βˆ’ 𝑑)2

    + V𝑗𝑑2πœ…π‘— (𝑇 βˆ’ 𝑑) βˆ’12πœ…π‘— βˆ«π‘‡

    𝑑Vπ‘—πœπ‘‘πœ

    + (πœŒπ‘— + πœŽπ‘—2πœ…π‘—)βˆ«π‘‡

    𝑑(𝑇 βˆ’ 𝜏)√Vπ‘—πœπ‘‘π‘π‘—πœ

    + √1 βˆ’ 𝜌2𝑗 βˆ«π‘‡π‘‘(𝑇 βˆ’ 𝜏)√Vπ‘—πœπ‘‘π‘π‘—πœ] .

    (9)

    Using the fact

    βˆ«π‘‡π‘‘(𝑇 βˆ’ 𝜏)√Vπ‘—πœπ‘‘π‘π‘—πœ = 1πœŽπ‘— [πœ…π‘— ∫

    𝑇

    𝑑(𝑇 βˆ’ 𝜏) Vπ‘—πœπ‘‘πœ

    + βˆ«π‘‡π‘‘Vπ‘—πœπ‘‘πœ βˆ’ (𝑇 βˆ’ 𝑑) V𝑗𝑑 βˆ’ πœ…π‘—πœƒπ‘— (𝑇 βˆ’ 𝑑)22 ] ,

    (10)

    for 𝑗 = 1, 2, thenln𝐺[𝑑,𝑇] = 𝑇 βˆ’ 𝑑𝑇 ln 𝑆𝑑 + 1𝑇

    2βˆ‘π‘—=1

    [βˆ’πœŒπ‘—πœ…π‘—πœƒπ‘—2πœŽπ‘— (𝑇 βˆ’ 𝑑)2

    βˆ’ πœŒπ‘—Vπ‘—π‘‘πœŽπ‘— (𝑇 βˆ’ 𝑑) +πœŒπ‘—πœŽπ‘— βˆ«π‘‡

    𝑑Vπ‘—πœπ‘‘πœ

    + (πœŒπ‘—πœ…π‘—πœŽπ‘— +12)βˆ«π‘‡

    𝑑(𝑇 βˆ’ 𝜏) Vπ‘—πœπ‘‘πœ

    + √1 βˆ’ 𝜌2𝑗 βˆ«π‘‡π‘‘(𝑇 βˆ’ 𝜏)√Vπ‘—πœπ‘‘π‘π‘—πœ] .

    (11)

    Let G be the πœŽβˆ’field generated byF𝑑 and {(𝑍1𝑒, 𝑍2𝑒) : 𝑑

  • Complexity 5

    + 2βˆ‘π‘—=1

    [𝑀(πœŒπ‘—Vπ‘—π‘‡πœŽπ‘— +2πœŒπ‘—πœ…π‘— + πœŽπ‘—2πœŽπ‘— ∫

    𝑇

    𝑑Vπ‘—πœπ‘‘πœ)

    βˆ’ βˆ«π‘‡π‘‘Vπ‘—πœπ‘‘πœ]}}} ,

    𝐴3 = exp{{{2βˆ‘π‘—=1

    √1 βˆ’ 𝜌2𝑗 βˆ«π‘‡π‘‘[ 𝑠𝑇 (𝑇 βˆ’ 𝜏) + 𝑀]

    β‹… √Vπ‘—πœπ‘‘π‘π‘—πœ}}} .(13)

    Since

    𝐸𝑄 [𝐴3 | G] = exp{{{122βˆ‘π‘—=1

    (1 βˆ’ 𝜌2𝑗 )

    β‹… βˆ«π‘‡π‘‘[ 𝑠𝑇 (𝑇 βˆ’ 𝜏) + 𝑀]

    2Vπ‘—πœπ‘‘πœ}}}

    = exp{{{2βˆ‘π‘—=1

    (1 βˆ’ 𝜌2𝑗 )2β‹… βˆ«π‘‡π‘‘[ 𝑠2𝑇2 (𝑇 βˆ’ 𝜏)2 + 2𝑠𝑀𝑇 (𝑇 βˆ’ 𝜏) + 𝑀2] Vπ‘—πœπ‘‘πœ}}} ,

    (14)

    substituting (14) into (12) and applying the Markov propertyof {V𝑗𝑒 : 0 ≀ 𝑒 ≀ 𝑇}, 𝑗 = 1, 2, lead to (5), which completes theproof.

    FromProposition 1, it is clear thatweneed to search for anexact formula for the discounted joint characteristic functionof V1𝑑 and V2𝑑 and the three different integrals of V𝑗𝑑 (𝑗 =1, 2) appearing in (5). We use the same approach introducedby Kim and Wee [18] to obtain an explicit formula for thediscounted joint characteristic function πœ“π‘‘(𝑠, 𝑀). Therefore,

    two series of functions are introduced as follows. Define πΉπ‘—πœand πΉπ‘—πœ : C4 β†’ C as

    πΉπ‘—πœ (𝑔𝑗1, 𝑔𝑗2, 𝑔𝑗3, 𝑔𝑗4) = βˆžβˆ‘π‘›=0

    𝑓𝑗𝑛 , (15)πΉπ‘—πœ (𝑔𝑗1, 𝑔𝑗2, 𝑔𝑗3, 𝑔𝑗4) = βˆžβˆ‘

    𝑛=1

    π‘›πœπ‘“π‘—π‘› , (16)where𝑓𝑗𝑛 , 𝑛 = 0, 1, 2, β‹… β‹… β‹… , are functions of 𝑔𝑗1, 𝑔𝑗2, 𝑔𝑗3, and 𝑔𝑗4defined as

    π‘“π‘—βˆ’2 = π‘“π‘—βˆ’1 = 0,𝑓𝑗0 = 1,𝑓𝑗1 = (πœ…π‘— βˆ’ 𝑔𝑗4𝜎

    2𝑗 ) 𝜏2 ,

    𝑓𝑗𝑛 = βˆ’ 𝜎2π‘—πœ22𝑛 (𝑛 βˆ’ 1) (𝑔𝑗1𝜏2π‘“π‘—π‘›βˆ’4 + 𝑔𝑗2πœπ‘“π‘—π‘›βˆ’3

    + (𝑔𝑗3 βˆ’ πœ…2𝑗2𝜎2𝑗 )𝑓

    π‘—π‘›βˆ’2) , 𝑛 β‰₯ 2,

    (17)

    for 𝑗 = 1, 2.For 𝑗 = 1, 2, denoteπ·π‘—πœ = {(𝑔𝑗1, 𝑔𝑗2, 𝑔𝑗3, 𝑔𝑗4) ∈ C4 :

    𝐸𝑄 [exp{R (𝑔𝑗1) ∫𝜏0(𝜏 βˆ’ 𝑑)2 V𝑗𝑑𝑑𝑑

    +R (𝑔𝑗2)∫𝜏0(𝜏 βˆ’ 𝑑) V𝑗𝑑𝑑𝑑 +R (𝑔𝑗3)∫𝜏

    0V𝑗𝑑𝑑𝑑

    +R (𝑔𝑗4) Vπ‘—πœ}] < ∞} .

    (18)

    Proposition 2. (1) οΏ½e argument of πΉπ‘—πœ : argπΉπ‘—πœ(𝑔𝑗1,𝑔𝑗2, 𝑔𝑗3, 𝑔𝑗4) ΜΈ= 0 for every (𝑔𝑗1, 𝑔𝑗2, 𝑔𝑗3, 𝑔𝑗4) ∈ π·π‘—πœ (𝑗 = 1, 2).In particular, argπΉπ‘—πœ is continuous on π·π‘—πœ, andargπΉπ‘—πœ(𝑔𝑗1, 𝑔𝑗2, 𝑔𝑗3, 𝑔𝑗4) = 0 for 𝑔𝑗1, 𝑔𝑗2, 𝑔𝑗3, and 𝑔𝑗4 areall real numbers inπ·π‘—πœ for 𝑗 = 1, 2.

    (2) For (𝑔𝑗1, 𝑔𝑗2, 𝑔𝑗3, 𝑔𝑗4) ∈ π·π‘—πœ, 𝑗 = 1, 2, we have

    𝐸𝑄[[exp{{{2βˆ‘π‘—=1

    [𝑔𝑗1 ∫𝜏0(𝜏 βˆ’ 𝑑)2 V𝑗𝑑𝑑𝑑 + 𝑔𝑗2 ∫𝜏

    0(𝜏 βˆ’ 𝑑) V𝑗𝑑𝑑𝑑 + 𝑔𝑗3 ∫𝜏

    0V𝑗𝑑𝑑𝑑 + 𝑔𝑗4Vπ‘—πœ]}}}

    ]]

    = exp{{{2βˆ‘π‘—=1

    (πœ…π‘—V𝑗0 + πœ…2π‘—πœƒπ‘—πœπœŽπ‘— βˆ’2V𝑗0𝜎2𝑗

    πΉπ‘—πœ (𝑔𝑗1, 𝑔𝑗2, 𝑔𝑗3, 𝑔𝑗4)πΉπ‘—πœ (𝑔𝑗1, 𝑔𝑗2, 𝑔𝑗3, 𝑔𝑗4) βˆ’2πœ…π‘—πœƒπ‘—πœŽ2𝑗 lnπΉπ‘—πœ (𝑔𝑗1, 𝑔𝑗2, 𝑔𝑗3, 𝑔𝑗4))

    }}} .(19)

  • 6 Complexity

    οΏ½e proof of Proposition 2 is similar to that of Kim andWee[18].

    Using Proposition 2 to Proposition 1 leads to the explicitexpression of πœ“π‘‘(𝑠, 𝑀) in Proposition 3. To describe the simplic-ity of the result, we need to introduce new functions. Define𝐻𝑗𝑑,𝑇and �̃�𝑗𝑑,𝑇: C2 β†’ C as𝐻𝑗𝑑,𝑇 (𝑠, 𝑀)= πΉπ‘—π‘‡βˆ’π‘‘ (𝑔𝑗1 (𝑠, 𝑀) , 𝑔𝑗2 (𝑠, 𝑀) , 𝑔𝑗3 (𝑠, 𝑀) , 𝑔𝑗4 (𝑠, 𝑀)) ,

    (20)

    �̃�𝑗𝑑,𝑇 (𝑠, 𝑀)= πΉπ‘—π‘‡βˆ’π‘‘ (𝑔𝑗1 (𝑠, 𝑀) , 𝑔𝑗2 (𝑠, 𝑀) , 𝑔𝑗3 (𝑠, 𝑀) , 𝑔𝑗4 (𝑠, 𝑀)) ,

    (21)

    with 𝑗 = 1, 2.Proposition 3. (1) If (𝑠, 𝑀) ∈ 𝐷, then 𝐻𝑗𝑑,𝑇(𝑠, 𝑀) ΜΈ= 0 andarg𝐻𝑗𝑑,𝑇 is continuous on𝐷. In particular, arg𝐻𝑗𝑑,𝑇(𝑠, 𝑀) = 0 if𝑠 and 𝑀 are real numbers for 𝑗 = 1, 2.

    (2) For πœ“π‘‘(𝑠, 𝑀) ∈ 𝐷 with arg𝐻𝑗𝑑,𝑇 defined as above, then

    πœ“π‘‘ (𝑠, 𝑀) = exp{{{2βˆ‘π‘—=1

    (βˆ’π‘π‘—1 �̃�𝑗𝑑,𝑇 (𝑠, 𝑀)𝐻𝑗𝑑,𝑇 (𝑠, 𝑀)

    βˆ’ 𝑐𝑗2ln𝐻𝑗𝑑,𝑇 (𝑠, 𝑀) + 𝑐𝑗3𝑠 + 𝑐𝑗4𝑀 + 𝑐𝑗5)}}} .(22)

    Here 𝑐𝑗1 = 2V𝑗𝑑/𝜎2𝑗 , 𝑐𝑗2 = 2πœ…π‘—πœƒπ‘—/𝜎2𝑗 ,

    𝑐𝑗3 = 𝑇 βˆ’ 𝑑2𝑇 ln 𝑆𝑑 βˆ’πœŒπ‘—πœ…π‘—πœƒπ‘— (𝑇 βˆ’ 𝑑)22πœŽπ‘—π‘‡ βˆ’

    πœŒπ‘— (𝑇 βˆ’ 𝑑)πœŽπ‘—π‘‡ V𝑗𝑑,𝑐𝑗4 = ln 𝑆𝑑2 βˆ’

    πœŒπ‘—πœŽπ‘— V𝑗𝑑 βˆ’πœŒπ‘—πœ…π‘—πœƒπ‘— (𝑇 βˆ’ 𝑑)πœŽπ‘— ,

    𝑐𝑗5 = πœ…π‘—V𝑗𝑑 + πœ…2π‘—πœƒπ‘— (𝑇 βˆ’ 𝑑)𝜎2𝑗

    (23)

    for 𝑗 = 1, 2.Proof. Assume that (𝑠, 𝑀) ∈ 𝐷, using the definitions of π‘”π‘—π‘˜ =π‘”π‘—π‘˜(𝑠, 𝑀) and π·π‘—πœ for π‘˜ = 1, 2, 3, 4 and 𝑗 = 1, 2. Note that(𝑔𝑗1, 𝑔𝑗2, 𝑔𝑗3, 𝑔𝑗4) ∈ π·π‘—πœ βŠ‚ π·π‘—π‘‡βˆ’π‘‘ for every 0 ≀ 𝑑 ≀ 𝑇 and𝑗 = 1, 2. Therefore, (19) remains valid for any V𝑗0 > 0. Thetime homogeneous Markov property of V𝑗𝑑 implies that (22)holds when Propositions 1 and 2 are satisfied.

    Now Substituting the expressions of 𝑔𝑗1, 𝑔𝑗2, 𝑔𝑗3, 𝑔𝑗4, 𝑗 =1, 2 into (15) and (16),𝐻𝑗𝑑,𝑇 and �̃�𝑗𝑑,𝑇 are expressed as follows,i.e., for (𝑠, 𝑀) ∈ C2,

    𝐻𝑗𝑑,𝑇 (𝑠, 𝑀) = βˆžβˆ‘π‘›=0

    β„Žπ‘—π‘› (𝑠, 𝑀) , (24)�̃�𝑗𝑑,𝑇 (𝑠, 𝑀) = βˆžβˆ‘

    𝑛=1

    𝑛𝑇 βˆ’ π‘‘β„Žπ‘—π‘› (𝑠, 𝑀) , (25)where

    β„Žπ‘—βˆ’2 (𝑠, 𝑀) = β„Žπ‘—βˆ’1 (𝑠, 𝑀) = 0,β„Žπ‘—0 (𝑠, 𝑀) = 1,β„Žπ‘—1 (𝑠, 𝑀) = (𝑇 βˆ’ 𝑑) (πœ…π‘— βˆ’ π‘€πœŒπ‘—πœŽπ‘—)2 ,β„Žπ‘—π‘› (𝑠, 𝑀) = (𝑇 βˆ’ 𝑑)24𝑛 (𝑛 βˆ’ 1) 𝑇2 {βˆ’π‘ 2𝜎2𝑗 (1 βˆ’ 𝜌2𝑗 ) (𝑇 βˆ’ 𝑑)2

    β‹… β„Žπ‘—π‘›βˆ’4 (𝑠, 𝑀) βˆ’ [π‘ πœŽπ‘—π‘‡(πœŽπ‘— + 2πœŒπ‘—πœ…π‘—)+ 2π‘ π‘€πœŽ2𝑗𝑇 (1 βˆ’ 𝜌2𝑗 )] (𝑇 βˆ’ 𝑑) β„Žπ‘—π‘›βˆ’3 (𝑠, 𝑀) + 𝑇 [πœ…2π‘—π‘‡βˆ’ 2π‘ πœŒπ‘—πœŽπ‘— βˆ’ 𝑀 (2πœŒπ‘—πœ…π‘— + πœŽπ‘—) πœŽπ‘—π‘‡ βˆ’ 𝑀2 (1 βˆ’ 𝜌2𝑗 ) 𝜎2𝑗𝑇+ 2𝜎2𝑗𝑇] β„Žπ‘—π‘›βˆ’2 (𝑠, 𝑀)} , 𝑛 β‰₯ 2,

    (26)

    for 𝑗 = 1, 2.4. Pricing Geometric Asian Option

    Once the discounted joint characteristic function is found,the European continuously monitored geometric Asianoption can be valued using numeraire change technique andthe inverse Fourier transform approach which are appliedin many research works (see, e.g., Geman et al. [41] andDeng [42]). This section derives the pricing formulas for thecontinuously monitored fixed and floating strike geometricAsian call options.

    Theorem 4. Suppose that 𝑆𝑑, V1𝑑, and V2𝑑 follow the dynamicsin (1), then the price at time 𝑑 ∈ [0, 𝑇] of the continuously mon-itored fixed strike geometric Asian call option with maturity 𝑇and the strike price 𝐾 is given by

    𝐺𝐴𝐢𝑓𝑖 (𝑑, 𝑆, V1, V2, 𝐾, 𝑇)= 𝑒(1/𝑇) βˆ«π‘‘0 lnπ‘†π‘’π‘‘π‘’πœ“π‘‘ (1, 0) Ξ 1 βˆ’ 𝐾𝑃 (𝑑, 𝑇)Ξ 2, (27)

    where 𝑃(𝑑, 𝑇) is given above in (3) andΠ𝑗 = 12 + 1πœ‹ ∫

    +∞

    0R[π‘’βˆ’π‘–π‘’ln𝐾𝑑,π‘‡πœ™π‘— (𝑒)𝑖𝑒 ]𝑑𝑒,

    𝑗 = 1, 2,

  • Complexity 7

    𝐾𝑑,𝑇 = πΎπ‘’βˆ’(1/𝑇) βˆ«π‘‘0 ln𝑆𝑒𝑑𝑒,πœ™1 (𝑒) = πœ“π‘‘ (𝑖𝑒 + 1, 0)πœ“π‘‘ (1, 0) ,πœ™2 (𝑒) = πœ“π‘‘ (𝑖𝑒, 0)πœ“π‘‘ (0, 0) ,

    (28)

    where 𝑖 is the imaginary unit (𝑖2 = βˆ’1).Proof. Since

    𝐺𝐴𝐢𝑓𝑖 (𝑑, 𝑆, V1, V2, 𝐾, 𝑇)= 𝐸𝑄 [π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’ (𝐺[0,𝑇] βˆ’ 𝐾)+ | F𝑑]= 𝑒(1/𝑇) βˆ«π‘‘0 ln𝑆𝑒𝑑𝑒𝐸𝑄 [π‘’βˆ’ ∫T𝑑 π‘Ÿπ‘’π‘‘π‘’πΊ[𝑑,𝑇]1{ln𝐺[𝑑,𝑇]β‰₯ln𝐾𝑑,𝑇} |F𝑑] βˆ’ 𝐾𝐸𝑄 [π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’1{ln𝐺[𝑑,𝑇]β‰₯ln𝐾𝑑,𝑇} | F𝑑]= 𝑒(1/𝑇) βˆ«π‘‘0 lnπ‘†π‘’π‘‘π‘’πœ“π‘‘ (1, 0)𝑄1 (ln𝐺[𝑑,𝑇] β‰₯ ln𝐾𝑑,𝑇)βˆ’ 𝐾𝑃 (𝑑, 𝑇)𝑄𝑇 (ln𝐺[𝑑,𝑇] β‰₯ ln𝐾𝑑,𝑇) ,

    (29)

    where𝑄1 is defined by the following Radon-Nikodymderiva-tive:

    𝑑𝑄1𝑑𝑄F𝑇 = π‘’βˆ’ ∫

    𝑇

    π‘‘π‘Ÿπ‘’π‘‘π‘’

    𝐺[𝑑,𝑇]𝐸𝑄 [π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’πΊ[𝑑,𝑇] | F𝑑] , (30)

    and 𝑄𝑇 is the π‘‡βˆ’ forward measure given above, it is wellknown that the probability distribution functions can becalculated by using the Fourier inversion transform, and thenthe above two probabilities 𝑄1 and 𝑄𝑇 in (29) are given by

    𝑄1 (ln𝐺[𝑑,𝑇] β‰₯ ln𝐾𝑑,𝑇)= 12 + 1πœ‹ ∫

    +∞

    0R [π‘’βˆ’π‘–π‘’ln𝐾𝑑,π‘‡πœ™1 (𝑒)𝑖𝑒 ] 𝑑𝑒 fl Ξ 1,

    (31)

    𝑄𝑇 (ln𝐺[𝑑,𝑇] β‰₯ ln𝐾𝑑,𝑇)= 12 + 1πœ‹ ∫

    +∞

    0R [π‘’βˆ’π‘–π‘’ln𝐾𝑑,π‘‡πœ™2 (𝑒)𝑖𝑒 ] 𝑑𝑒 fl Ξ 2,

    (32)

    where

    πœ™1 (𝑒) = 𝐸𝑄1 [𝑒𝑖𝑒ln𝐺[𝑑,𝑇] | F𝑑]= 𝐸𝑄 [π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’+𝑖𝑒ln𝐺[𝑑,𝑇]𝐺[𝑑,𝑇] | F𝑑]𝐸𝑄 [π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’πΊ[𝑑,𝑇] | F𝑑]

    = 𝐸𝑄 [π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’+(𝑖𝑒+1)ln𝐺[𝑑,𝑇] | F𝑑]𝐸𝑄 [π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’+ln𝐺[𝑑,𝑇] | F𝑑]

    = πœ“π‘‘ (𝑖𝑒 + 1, 0)πœ“π‘‘ (1, 0) ,(33)

    πœ™2 (𝑒) = 𝐸𝑄𝑇 [𝑒𝑖𝑒ln𝐺[𝑑,𝑇] | F𝑑]= 𝐸𝑄 [π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’+𝑖𝑒ln𝐺[𝑑,𝑇] | F𝑑]𝐸𝑄 [π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’ | F𝑑] =

    πœ“π‘‘ (𝑖𝑒, 0)𝑃 (𝑑, 𝑇) .(34)

    From (29), (31), and (32), we can obtain the requiredTheorem 4.

    Theorem 5. Suppose that 𝑆𝑑, V1𝑑, and V2𝑑 follow the dynamicsin (1), then the price at time 𝑑 ∈ [0, 𝑇] of the continuouslymonitored floating strike geometric Asian call option withmaturity 𝑇 is given by

    𝐺𝐴𝐢𝑓𝑙 (𝑑, 𝑆, V1, V2, 𝑇) = 𝑆𝑑Π̂1βˆ’ 𝑒(1/𝑇) βˆ«π‘‘0 lnπ‘†π‘’π‘‘π‘’πœ“π‘‘ (1, 0) Ξ Μ‚2, (35)

    where

    Ξ Μ‚1= 12

    βˆ’ 1πœ‹ ∫+∞

    0R[[

    πœ“π‘‘ (𝑖𝑒, 1 βˆ’ 𝑖𝑒) 𝑒(𝑖𝑒/𝑇) βˆ«π‘‘0 ln𝑆𝑒𝑑𝑒𝑖𝑒𝑆𝑑 ]]𝑑𝑒,Ξ Μ‚2= 12

    βˆ’ 1πœ‹ ∫+∞

    0R[[

    πœ“π‘‘ (𝑖𝑒 + 1, βˆ’π‘–π‘’) 𝑒(𝑖𝑒/𝑇) βˆ«π‘‘0 lnπ‘†π‘’π‘‘π‘’π‘–π‘’πœ“π‘‘ (1, 0) ]]𝑑𝑒.

    (36)

    Proof. Since

    𝐺𝐴𝐢𝑓𝑙 (𝑑, 𝑆, V1, V2, 𝑇) = 𝐸𝑄 [π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’ (𝑆𝑇 βˆ’ 𝐺[0,𝑇])+ | F𝑑]= 𝑒(1/𝑇) βˆ«π‘‘0 ln𝑆𝑒𝑑𝑒𝐸𝑄 [π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’ (π‘†π‘‡π‘’βˆ’(1/𝑇) βˆ«π‘‘0 ln𝑆𝑒𝑑𝑒 βˆ’ 𝐺[𝑑,𝑇])+ |F𝑑] = 𝐸𝑄 [π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’π‘†π‘‡1{ln(𝐺[𝑑,𝑇]/𝑆𝑇)β‰€βˆ’(1/𝑇) βˆ«π‘‘0 ln𝑆𝑒𝑑𝑒} | F𝑑]βˆ’ 𝑒(1/𝑇) βˆ«π‘‘0 ln𝑆𝑒𝑑𝑒𝐸𝑄 [π‘’βˆ’ βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’πΊ[𝑑,𝑇]1{ln(𝐺𝑑,𝑇/𝑆𝑇)β‰€βˆ’(1/𝑇) βˆ«π‘‘0 ln𝑆𝑒𝑑𝑒} |

  • 8 Complexity

    F𝑑] = 𝑆𝑑𝑄2 (ln(𝐺[𝑑,𝑇]𝑆𝑇 ) ≀ βˆ’1𝑇 βˆ«π‘‘

    0ln 𝑆𝑒𝑑𝑒)

    βˆ’ 𝑒(1/𝑇) βˆ«π‘‘0 lnπ‘†π‘’π‘‘π‘’πœ“π‘‘ (1, 0)𝑄1 (ln(𝐺[𝑑,𝑇]𝑆𝑇 ) ≀ βˆ’1𝑇 βˆ«π‘‘

    0ln 𝑆𝑒𝑑𝑒) ,

    (37)

    where𝑄2 is defined by the following Radon-Nikodymderiva-tive:

    𝑑𝑄2𝑑QF𝑇 = π‘’βˆ’ ∫

    𝑇

    π‘‘π‘Ÿπ‘’π‘‘π‘’ 𝑆𝑇𝑆𝑑 , (38)

    under the two probability measures 𝑄1 and 𝑄2, the condi-tional characteristic functions of ln(𝐺[𝑑,𝑇]/𝑆𝑇) are given by

    𝐸𝑄1 [𝑒𝑖𝑒ln(𝐺[𝑑,𝑇]/𝑆𝑇) | F𝑑]= 𝐸𝑄 [π‘’βˆ’βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’+𝑖𝑒ln(𝐺[𝑑,𝑇]/S𝑇)𝐺[𝑑,𝑇] | F𝑑]

    𝐸𝑄 [π‘’βˆ’βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’πΊ[𝑑,𝑇] | F𝑑]= πœ“π‘‘ (𝑖𝑒 + 1, βˆ’π‘–π‘’)πœ“π‘‘ (1, 0) ,

    (39)

    𝐸𝑄2 [𝑒𝑖𝑒ln(𝐺[𝑑,𝑇]/𝑆𝑇) | F𝑑]= 𝐸𝑄 [π‘’βˆ’βˆ«π‘‡π‘‘ π‘Ÿπ‘’π‘‘π‘’+𝑖𝑒ln(𝐺[𝑑,𝑇]/𝑆𝑇)+ln𝑆𝑇 | F𝑑]

    𝑆𝑑= πœ“π‘‘ (𝑖𝑒, 1 βˆ’ 𝑖𝑒)𝑆𝑑 .

    (40)

    Therefore

    𝑄1 (ln(𝐺𝑑,𝑇𝑆𝑇 ) ≀ βˆ’1𝑇 βˆ«π‘‘

    0ln 𝑆𝑒𝑑𝑒)

    = 12βˆ’ 1πœ‹ ∫

    +∞

    0R[[

    πœ“π‘‘ (𝑖𝑒 + 1, βˆ’π‘–π‘’) 𝑒(𝑖𝑒/𝑇) βˆ«π‘‘0 ln π‘†π‘’π‘‘π‘’π‘–π‘’πœ“π‘‘ (1, 0) ]]𝑑𝑒,(41)

    𝑄2 (ln(𝐺𝑑,𝑇𝑆𝑇 ) ≀ βˆ’1𝑇 βˆ«π‘‘

    0ln 𝑆𝑒𝑑𝑒)

    = 12βˆ’ 1πœ‹ ∫

    +∞

    0R[[

    πœ“π‘‘ (𝑖𝑒, 1 βˆ’ 𝑖𝑒) 𝑒(𝑖𝑒/𝑇) βˆ«π‘‘0 ln𝑆𝑒𝑑𝑒𝑆𝑑 β‹… 𝑖𝑒 ]] 𝑑𝑒.(42)

    Plugging (41) and (42) in (37) yields (35).

    In addition to option prices, one can compute derivativesto hedge against changes in the underlying asset price 𝑆 andvolatilities V1 and V2. We omit it due to its triviality.

    5. Numerical Examples

    In this section, we use the dbH-SI model to analyze the val-uation of the continuously monitored fixed strike geometricAsian call option using some numerical examples. To imple-ment the analytic formula given in (27) numerically, we firstdetermine the number of terms taken for the computationof the infinite series expansions for 𝐻𝑗𝑑,𝑇 and �̃�𝑗𝑑,𝑇 for 𝑗 =1, 2 in (24) and (25). Second, we investigate the accuracyand efficiency of the approximated analytic formula givenin (27). In the end, we compare the option prices varyingby 𝑆0 and 𝑇 under different models including the dbH-SI,H-SI (i.e., Heston stochastic volatility model with stochasticinterest rate), dbH, and Heston models. Furthermore, we usethis proposed model (1), i.e., the dbH-SI model, to examinethe impacts of the model parameters on option prices. Herewe implement the integral formulas given in (27) withouttruncation,modification, and approximation inMathematicaand Matlab software. Numerical integration was performedusing the β€œNIntegrate()” or β€œquadgk()” commands whichcan handle infinite ranges, oscillatory integrands, and sin-gularities in their default version, which employs automaticadaptive integration.

    Model (1) parameters are set as follows: πœ…1 = 1.15, πœ…2 =2.2, πœƒ1 = 0.2, πœƒ2 = 0.15, 𝜎1 = 0.5, 𝜎2 = 0.8, 𝜌1 = βˆ’0.4,𝜌2 = βˆ’0.64, V10 = 0.09, V20 = 0.04, 𝑆0 = 100, and 𝑑 = 0. Theresults are shown in Table 1.

    Table 1 investigates the influence of the number of terms𝑛 taken in (24) and (25). It is shown that the numerical valuestend to be quite stable as the number of terms increases. Inparticular, the option prices stay unchanged after taking 𝑛 =20 and 𝑛 = 30 terms, at most. In addition, Table 1 providesoption prices with various maturities 𝑇, strike prices 𝐾, andthe requiredCPU times (in seconds). FromTable 1, we can seethat some characteristics of the GAC𝑓𝑖 option are similar tothe plain European call option. For example, the values of theGAC𝑓𝑖 option are decreasing functions of the strike price. Inaddition, under the same parameter values setting in dbH-SImodel, longer maturating date 𝑇 will result in higher optionvalues.

    It would be interesting to see the performance of ourapproximated analytic formula approach implemented to thefixed strike GAC option under dbH-SImodel. Our numericalexample uses the number of terms 𝑛 = 20 taken in (24) and(25); other parameter values are similar to those settings ofTable 1. We compute the 0.5-,1.5-, and 3-year maturity GACoptions by our approximated analytic formula approach andcompare the results with Monte Carlo simulation with 10000sample paths and 100 points for time axis. The numericalresults are displayed in Table 2.

    Table 2 shows that the approximated analytic formulaapproach is considerably faster than those of the MonteCarlo simulation (MC). For a given set of parameters,the approximated analytic formula approach calculates theoption prices for 5 different strikes and 3 different maturatesin approximately 5 seconds. The Monte Carlo simulationtakes around 110 seconds for each option price. Table 2 alsocompares their pricing accuracy. It can be seen that therelative error (RE) in prices is less than 0.4% for all cases. If

  • Complexity 9

    Table 1: GAC𝑓𝑖 option prices with different maturities, strike prices, and varying n.

    𝑇 𝐾 𝑛 Option price CPU (sec.) 𝑇 𝐾 𝑛 Option price CPU (sec.)0.5 90 5 17.8597 0.287 1.5 90 5 26.4805 0.291

    10 17.7859 0.291 10 25.2393 0.29415 17.7849 0.294 15 25.2254 0.29920 17.7849 0.296 20 25.2251 0.30225 17.7849 0.301 25 25.2251 0.30730 17.7849 0.312 30 25.2251 0.315

    100 5 9.7733 0.279 100 5 19.8642 0.27610 9.8624 0.288 10 19.1846 0.28515 9.8623 0.290 15 19.1758 0.29020 9.8623 0.295 20 19.1755 0.30225 9.8623 0.298 25 19.1755 0.30930 9.8623 0.302 30 19.1755 0.311

    110 5 4.2061 0.283 110 5 14.1405 0.28310 4.5395 0.291 10 14.0976 0.29115 4.5415 0.304 15 14.1003 0.29720 4.5415 0.306 20 14.1002 0.30425 4.5415 0.312 25 14.1002 0.31030 4.5415 0.315 30 14.1002 0.315

    1 90 5 22.3192 0.268 3 90 5 30.5831 0.28910 22.0988 0.283 10 29.6250 0.29315 22.0938 0.287 15 29.2870 0.29920 22.0938 0.296 20 29.2835 0.30525 22.0938 0.313 25 29.2835 0.31430 22.0938 0.319 30 29.2835 0.317

    100 5 15.0971 0.281 100 5 26.7286 0.26810 15.1874 0.287 10 25.6231 0.28415 15.1850 0.294 15 25.3192 0.29120 15.1849 0.298 20 25.3151 0.29525 15.1849 0.301 25 25.3151 0.29830 15.1849 0.307 30 25.3151 0.307

    110 5 9.2791 0.275 110 5 22.5318 0.28110 9.7604 0.278 10 21.9684 0.28415 9.7650 0.281 15 21.7105 0.29720 9.7651 0.292 20 21.7064 0.30125 9.7651 0.294 25 21.7064 0.30530 9.7651 0.301 30 21.7064 0.310

    we regard the Monte Carlo price as the benchmark, then thisnumerical example confirms that the approximated analyticformula approach is accurate and efficient.

    After examining accuracy and efficiency. We shall turnto investigate the comparison of the option prices underdifferent models. Figure 1 compares the dbH-SI model withHeston, dbH, and H-SI models in pricing the fixed strikeGAC option against the initial asset price 𝑆0 and maturatingdate 𝑇 with the strike price 𝐾 = 100. From Figure 1, it isinteresting to notice that the option prices of the fixed strikeGAC option calculated from the dbH-SI model are muchhigher than those of the dbHmodel, H-SImodel, and Hestonmodel. One possible reason for this phenomena is that thevolatilities are always bigger for the dbH-SI model than those

    for other models. This implies that the proposed model, i.e.,the dbH-SI model, has a more significant influence than thedbHmodel, H-SImodel, and Hestonmodel on option prices.We can also clearly observe that the bigger the value of 𝑆0(or𝑇) is, the higher the GAC𝑓𝑖 option price is.

    In Figure 2, we use the dbH-SI model to examine theeffects of the mean-reverting rates (πœ…1, πœ…2) and volatilities(𝜎1, 𝜎2) of variance processes (V1𝑑, V2𝑑) on the GAC𝑓𝑖 optionprices (see Figures 2(a)–2(d)). We also examine the impactsof the correlation coefficients (𝜌1, 𝜌2) (see Figures 2(e)and 2(f)), which determine both the correlation betweenthe underlying asset and its volatilities, and the correla-tion between the underlying asset and the short interestrates.

  • 10 Complexity

    Table 2: Comparison of the approximated approach and MC for GAC𝑓𝑖 options.

    𝑇 𝐾 Approximated approach CPU(sec.) Monte Carlo CPU(sec.) RE(%)0.5 90 17.7849 0.284 17.7892 110.302 -0.0242

    95 13.5305 0.291 13.5246 110.384 0.0436100 9.8623 0.278 9.8602 110.403 0.0213105 6.8598 0.296 6.8624 110.329 -0.3810110 4.5415 0.287 4.5407 110.376 0.0176

    1.5 90 25.2251 0.265 25.2206 110.376 0.017895 22.0851 0.281 22.0891 110.391 -0.0181100 19.1755 0.294 19.1787 110.417 -0.0167105 16.5109 0.312 16.5045 110.485 0.3888110 14.1002 0.293 14.1039 110.392 -0.0262

    3 90 29.2835 0.271 29.2894 110.428 -0.020195 27.2560 0.289 27.2513 110.397 0.0173100 25.3151 0.307 25.3106 110.405 0.0178105 23.4644 0.295 23.4595 110.471 0.0209110 21.7065 0.292 21.7128 110.396 -0.0290

    80 85 90 95 100 105 110 115 120S0

    0

    5

    10

    15

    20

    25

    30

    35

    40

    45

    optio

    n pr

    ice

    dbH-SI modeldbH modelH-SI modelHeston model

    (a) Option price against 𝑆0

    0.5 1 1.5 2 2.5 3 3.5 4 4.5T

    5

    10

    15

    20

    25

    30

    35

    40

    optio

    n pr

    ice

    dbH-SI modeldbH modelH-SI modelHeston model

    (b) Option price against 𝑇

    Figure 1: Comparison of option prices under Heston, dbH, H-SI, and dbH-SI models.

    From Figures 2(a) and 2(b), we can observe that theoption prices increase as the mean-reverting rate increases.Particularly, it is quite remarkable that the mean-revertingrates have a significant effect on the longer termoption values.The option price decreases as the volatilities of varianceprocesses increase (see Figures 2(c) and 2(d)).The correlationcoefficients (𝜌1, 𝜌2) have several effects depending on therelation between the strike price and the initial asset price.A negative (𝜌1, 𝜌2) tends to produce higher values for ITM(in-the-money) options and lower values for OTM (out-of-the-money) options (see Figure 2(e)). A similar result holdswith respect to the expiration date: a negative (𝜌1, 𝜌2) tends to

    produce higher value for the longer term options and lowervalues for the shorter options (see Figure 2(f)).

    6. Conclusions

    Theproposedmodel (the dbH-SImodel) incorporates severalimportant features of the underlying asset returns variability.We derive the discounted joint characteristic function ofthe log-asset price and its log-geometric mean value overtime period [0, 𝑇] and obtain approximated analytic solutionsto the continuously monitored fixed and floating strikegeometric Asian call options using the change of numeraire

  • Complexity 11

    S0

    5

    10

    15

    20

    25

    30

    35

    optio

    n pr

    ice

    80 85 90 95 100 105 110 115 120

    (οΌ₯1, οΌ₯2)=(1.5,1)

    (οΌ₯1, οΌ₯2)=(1.5,2)

    (οΌ₯1, οΌ₯2)=(2,1.5)

    (οΌ₯1, οΌ₯2)=(1.5,1.5)

    (οΌ₯1, οΌ₯2)=(1,1.5)

    (a)

    T

    5

    10

    15

    20

    25

    30

    35

    optio

    n pr

    ice

    0.5 1 1.5 2 2.5 3 3.5 4

    (οΌ₯1, οΌ₯2)=(1.5,1)

    (οΌ₯1, οΌ₯2)=(1.5,2)

    (οΌ₯1, οΌ₯2)=(2,1.5)

    (οΌ₯1, οΌ₯2)=(1.5,1.5)

    (οΌ₯1, οΌ₯2)=(1,1.5)

    (b)

    S0

    05

    101520253035404550

    optio

    n pr

    ice

    80 85 90 95 100 105 110 115 120

    (1, 2)=(0.2,0.5)

    (1, 2)=(0.2,0.7)

    (1, 2)=(0.2,0.9)

    (1, 2)=(0.6,0.5)

    (1, 2)=(0.9,0.5)

    (c)

    T

    10

    15

    20

    25

    30

    35

    40

    optio

    n pr

    ice

    0.5 1 1.5 2 2.5 3 3.5 45

    (1, 2)=(0.2,0.5)

    (1, 2)=(0.2,0.7)

    (1, 2)=(0.2,0.9)

    (1, 2)=(0.6,0.5)

    (1, 2)=(0.9,0.5)

    (d)

    S0

    0

    10

    20

    30

    40

    50

    60

    70

    80

    optio

    n pr

    ice

    80 85 90 95 100 105 110 115 120

    (1, 2)=(0.6,-0.6)

    (1, 2)=(0.6,0)

    (1, 2)=(0.6,0.6)

    (1, 2)=(-0.6,0.6)

    (1, 2)=(0,0.6)

    (1, 2)=(-0.6,-0.6)

    (e)

    T

    510152025303540455055

    optio

    n pr

    ice

    0.5 1 1.5 2 2.5 3 3.5 4

    (1, 2)=(0.6,-0.6)

    (1, 2)=(0.6,0)

    (1, 2)=(0.6,0.6)

    (1, 2)=(-0.6,0.6)

    (1, 2)=(0,0.6)

    (1, 2)=(-0.6,-0.6)

    (f)

    Figure 2: Option prices with respect to 𝑆0 and 𝑇 in the dbH-SI model.

  • 12 Complexity

    technique and the Fourier inversion transform approach.Some numerical examples are provided to examine theeffects of the proposed model, which reveals some additionalfeatures having a significant impact on option values, espe-cially long-term options. The proposed model can be testedempirically by using the option price data from the optionmarket.

    Data Availability

    All data used to support of the findings for this study areincluded within this article.

    Conflicts of Interest

    The authors declare that there are no conflicts of interestregarding the publication of this paper.

    Acknowledgments

    The authors acknowledge the financial support providedby the Natural Sciences Foundation of China (11461008),the Guangxi Natural Science Foundation (2018JJA110001),and the Guangxi Graduate Education Innovation Programproject (XYCSZ2018059).

    References

    [1] P. Boyle and F. Boyle, Derivatives: οΏ½e Tools that ChangedFinance, Risk Books, London, UK, 2001.

    [2] F. Black and M. Scholes, β€œThe pricing of options corporateliabilities,” Journal of Political Economy, vol. 81, no. 3, pp. 637–659, 1973.

    [3] S. M. Turnbull and M. D. Wakeman, β€œA Quick Algorithm forPricing European Average Options,” Journal of Financial andQuantitative Analysis, vol. 26, no. 3, pp. 377–389, 1991.

    [4] P. Ritchken, L. Sankarasubramanian, and A. M. Vijh, β€œTheValuation of Path Dependent Contracts on the Average,”Man-agement Science, vol. 39, no. 10, pp. 1202–1213, 1993.

    [5] H. Geman and M. Yor, β€œBessel processes, Asian options andperpetuities,” Mathematical Finance, vol. 3, no. 4, pp. 349–375,1993.

    [6] L. C. Rogers and Z. Shi, β€œThe value of an Asian option,” Journalof Applied Probability, vol. 32, no. 4, pp. 1077–1088, 1995.

    [7] P. Boyle,M. Broadie, and P. Glasserman, β€œMonteCarlomethodsfor security pricing,” Journal of Economic Dynamics & Control,vol. 21, no. 8-9, pp. 1267–1321, 1997.

    [8] J. Angus, β€œA note on pricing derivatives with continuousgeometric averaging,” Journal of FutureMarkets, vol. 19, pp. 823–839, 1999.

    [9] V. Linetsky, β€œSpectral expansions for Asian (average price)options,” Operations Research, vol. 52, no. 6, pp. 856–867, 2004.

    [10] Z. Cui, C. Lee, and Y. Liu, β€œSingle-transform formulas for pric-ing Asian options in a general approximation framework underMarkov processes,” European Journal of Operational Research,vol. 266, no. 3, pp. 1134–1139, 2018.

    [11] G. Fusai and A. Roncoroni,Asian Options: An Average Problem,in Problem Solving in Quantitative Finance: A Case-StudyApproach, Springer, 2008.

    [12] J. Sun, L. Chen, and S. Li, β€œA Quasi-analytical pricing model forarithmetic Asian options,” Journal of Futures Markets, vol. 33,no. 12, pp. 1143–1166, 2013.

    [13] J. C. Hull and A. White, β€œThe pricing of options on assets withstochastic volatilities,”�e Journal of Finance, vol. 42, no. 2, pp.281–300, 1987.

    [14] E. M. Stein and J. C. Stein, β€œStock price distribution withstochastic volatility: an analytic approach,” Review of FinancialStudies, vol. 4, pp. 727–752, 1991.

    [15] S. L.Heston, β€œA closed-form solution for options with stochasticvolatility with applications to bond and currency options,” οΏ½eReview of Financial Studies, vol. 6, no. 2, pp. 327–343, 1993.

    [16] H. Y. Wong and Y. L. Cheung, β€œGeometric asian option: val-uation and calibration with stochastic volatility,” QuantitativeFinance, vol. 4, pp. 301–314, 2004.

    [17] F. Hubalek and C. Sgarra, β€œOn the explicit evaluation of thegeometric Asian options in stochastic volatility models withjumps,” Journal of Computational and AppliedMathematics, vol.235, no. 11, pp. 3355–3365, 2011.

    [18] B. Kim and I.-S.Wee, β€œPricing of geometric Asian options underHeston’s stochastic volatility model,” Quantitative Finance, vol.14, no. 10, pp. 1795–1809, 2014.

    [19] Q. Shi and X. Yang, β€œPricing Asian options in a stochasticvolatility model with jumps,” Applied Mathematics and Compu-tation, vol. 228, pp. 411–422, 2014.

    [20] S. Alizadeh, M. Brandt, and F. Diebold, β€œRange-based estima-tion of stochastic volatility models,” Journal of Finance, vol. 57,no. 3, pp. 1047–1091, 2002.

    [21] G. Fiorentini, A. León, andG. Rubio, β€œEstimation and empiricalperformance of Heston’s stochastic volatility model: the case ofthinly traded market,” Journal of Empirical Finance, vol. 9, pp.225–255, 2002.

    [22] M. Chernov, A. R. Gallant, E. Ghysels, and G. Tauchen,β€œAlternativemodels for stock price dynamics,” Journal of Econo-metrics, vol. 116, no. 1-2, pp. 225–257, 2003.

    [23] C. Gourieroux, β€œContinuous time Wishart process for stochas-tic risk,” Econometric Reviews, vol. 25, no. 2-3, pp. 177–217, 2006.

    [24] P. Christoffersen, S. Heston, and K. Jacobs, β€œThe shape and termstructure of the index option smirk: why multifactor stochasticvolatility models work so well,”Management Science, vol. 55, no.12, pp. 1914–1932, 2009.

    [25] J. M. Romo, β€œPricing Forward Skew Dependent Derivatives.Multifactor Versus Single-Factor Stochastic Volatility Models,”Journal of Futures Markets, vol. 34, no. 2, pp. 124–144, 2014.

    [26] K. Nagashima, T.-K. Chung, and K. Tanaka, β€œAsymptoticExpansion Formula of Option Price Under Multifactor HestonModel,” Asia-Pacific Financial Markets, vol. 21, no. 4, pp. 351–396, 2014.

    [27] D.Duffie, J. Pan, andK. Singleton, β€œTransformanalysis and assetpricing for affine jump-diffusions,” Econometrica, vol. 68, pp.1343–1376, 2000.

    [28] J.-P. Fouque, G. Papanicolaou, R. Sircar, and K. SΓΈlna, β€œMulti-scale stochastic volatility asymptotics,”Multiscale Modeling andSimulation: A SIAM Interdisciplinary Journal, vol. 2, no. 1, pp.22–42, 2003.

    [29] Y. Sun, β€œEfficient pricing and hedging under the double Hestonstochastic volatility jump-diffusion model,” International Jour-nal of Computer Mathematics, vol. 92, no. 12, pp. 2551–2574,2015.

    [30] F. Mehrdoust and N. Saber, β€œPricing arithmetic Asian optionunder a two-factor stochastic volatility model with jumps,”

  • Complexity 13

    Journal of Statistical Computation and Simulation, vol. 85, no.18, pp. 3811–3819, 2015.

    [31] S. Zhang and Y. Sun, β€œForward starting options pricing withdounble stochastic volatility, stochastic interest rate and doublejumps,” Journal of Computational and AppliedMathematics, vol.325, pp. 34–41, 2017.

    [32] J. A. Nielsen and K. Sandmann, β€œThe pricing of Asian optionsunder stochastic interest rates,” Applied Mathematical Finance,vol. 3, no. 3, pp. 209–236, 1996.

    [33] J. A. Nielsen and K. Sandmann, β€œPricing of Asian exchangerate options under stochastic interest rates as a sum of options,”Finance and Stochastics, vol. 6, no. 3, pp. 355–370, 2002.

    [34] S. Zhang, S. Yuan, and L. Wang, β€œPrices of Asian options understochastic interest rates,” Applied Mathematics: A Journal ofChinese Universities, vol. 21, no. 2, pp. 135–142, 2006.

    [35] R. Donnelly, S. Jaimungal, and D. H. Rubisov, β€œValuing guar-anteed withdrawal benefits with stochastic interest rates andvolatility,”Quantitative Finance, vol. 14, no. 2, pp. 369–382, 2014.

    [36] X.-J. He and S.-P. Zhu, β€œA closed-form pricing formula for Euro-pean options under the Heston model with stochastic interestrate,” Journal of Computational and Applied Mathematics, vol.335, pp. 323–333, 2018.

    [37] J. C. Cox, J. E. Ingersoll, and S. Ross, β€œA theory of the termstructure of interest rates,” Econometrica, vol. 53, pp. 373–384,1985.

    [38] O. Vasicek, β€œAn equilibrium characterization of the term struc-ture,” Journal of Financial Economics, vol. 5, no. 2, pp. 177–188,1977.

    [39] F. A. Longstaff and E. S. Schwartz, β€œInterest rate volatility andthe term structure: a two-factor general equilibriummodel,”�eJournal of Finance, vol. 47, no. 4, pp. 1259–1282, 1992.

    [40] N. D. Pearson and T. Sun, β€œExploiting the conditional densityin estimating the term structure: an application to the Cox,Ingersoll and Ross model,” οΏ½e Journal of Finance, vol. 49, no.4, pp. 1279–1304, 1994.

    [41] H. Geman, N. Karoui, and J. C. Rochet, β€œChanges of numeraire,changes of probability measure and option pricing,” Journal ofApplied Probability, vol. 32, pp. 443–458, 1995.

    [42] G. Deng, β€œPricing European option in a double exponentialjump-diffusion model with two market structure risks andits comparisons,” Applied Mathematics: A Journal of ChineseUniversities, vol. 22, no. 2, pp. 127–137, 2007.

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