Theoretical Economics Letters, 2012, 2, 400-407
http://dx.doi.org/10.4236/tel.2012.24074 Published Online October 2012 (http://www.SciRP.org/journal/tel)
Joint Characteristic Function of Stock Log-Price and
Squared Volatility in the Bates Model and Its Asset Pricing
Applications
Oleksandr Zhylyevskyy
Department of Economics, Iowa State University, Ames, USA
Email: oz9a@iastate.edu
Received July 17, 2012; revised August 17, 2012; accepted September 17, 2012
ABSTRACT
The model of Bates specifies a rich, flexible structure of stock dynamics suitable for applications in finance and eco-
nomics, including valuation of derivative securities. This paper analytically derives a closed-form expression for the
joint conditional characteristic function of a stock’s log-price and squared volatility under the model dynamics. The use
of the function, based on inverting it, is illustrated on examples of pricing European-, Bermudan-, and American-style
options. The discussed approach for European-style derivatives improves on the option formula of Bates. The suggested
approach for American-style derivatives, based on a compound-option technique, offers an alternative solution to exist-
ing finite-difference methods
Keywords: Bates Model; Stochastic Volatility; Jump-Diffusion; Characteristic Function; Option Pricing
1. Introduction
Stochastic volatility and jump-diffusion are standard tools
of modeling asset price dynamics in finance research (see
Aït-Sahalia and Jacod, 2011 [1]). Popularity of stochastic
volatility models, such as the continuous-time model of
Heston (1993) [2], is partly due to their ability to account
for several aspects of stock price data that are not cap-
tured by analytically simpler geometric Brownian motion
dynamics. For example, these models can help to account
for an empirically relevant “leverage effect,” which re-
fers to an increase in the volatility of a stock when its
price declines, and a decrease in the volatility when the
price rises. They also can help to partly correct for defi-
ciencies of the famous Black and Scholes (1973) [3] op-
tion pricing formula (e.g., the implied volatility “smile”).
The model of Bates (1996) [4] extends the Heston model
by incorporating jumps in stock dynamics. Allowing for
jumps enables a more realistic representation of stock
price time-series, which may feature discontinuities (for
a discussion on jumps in asset data, see Aït-Sahalia and
Jacod, 2009 [5]).
In this paper, I analytically derive and provide exam-
ples for the use of a closed-form expression for the joint
conditional characteristic function of a stock’s log-price
and squared volatility under the dynamics of the Bates
model. The model offers a rich distributional structure of
stock returns. For instance, a skewed distribution can
arise due to a correlation between shocks to the stock
price and shocks to the volatility or due to nonzero aver-
age jumps. Excess kurtosis can arise from variable vola-
tility or from a jump component. Also, the model can
help to distinguish between two alternative explanations
for skewness and excess kurtosis: stochastic volatility
implies a positive relationship between the length of the
holding period and the magnitude of skewness and kur-
tosis, whereas jumps imply a negative relationship (Bates,
1996 [4], pp. 72-73). The flexibility of the model makes
it particularly attractive for the task of valuation of de-
rivative securities. As such, it is useful in applied research
and practice.
Under jump-diffusion dynamics with stochastic vola-
tility, the values of derivative securities such as Euro-
pean-style options are typically impossible to express in
simple form. Instead, they may be computed numeri-
cally by applying the transform methods of Duffie et al.
(2000) [6] and Bakshi and Madan (2000) [7], which
require inverting a conditional characteristic function of
an underlying state-price vector. Bates (1996) [4] solved
for the marginal conditional characteristic function of
the logprice and derived a formula for the value of a
European-style call option that involves two separate
inversions. In contrast, the problem of finding the joint
conditional characteristic function of the log-price and
squared volatility was not posed, and to the best of my
knowledge, a solution for this function is not available in
C
opyright © 2012 SciRes. TEL
O. ZHYLYEVSKYY 401
existing finance studies. This paper aims to fill in the gap
by deriving a closed-form expression for the function,
which is an analytically challenging task. In addition, I
provide two practically relevant examples illustrating the
use of the function. The first example revisits the prob-
lem of the valuation of European-style options. I show
that the marginal characteristic function is a special case
of the joint characteristic function and then apply results
from prior research to obtain formulas for European-style
put and call options that require a single inversion; this
approach is more efficient than the solution suggested by
Bates involving two inversions. The second example
addresses the problem of valuation of Bermudan- and
American-style options by proposing an extension of the
Geske-Johnson compound-option technique (Geske and
Johnson, 1984 [8]). In this case, knowledge of the joint
(rather than marginal) characteristic function is indis-
pensable. The proposed approach provides an alternative
to pricing American-style options using finite-difference
methods (e.g., Chiarella et al., 2008 [9]), which can pose
practical challenges when dealing with stochastic volatil-
ity (for a review, see Zhylyevskyy, 2010 [10]). The em-
pirical relevance of the example is due to a large num-
ber of single name equity and commodity futures op-
tions traded on organized exchanges being American-
style.
The remainder of the paper is organized as follows.
Section 2 sets up the Bates model and outlines the as-
sumptions and notation. Section 3 derives a stochastic
differential equation for the stock’s log-price. Section 4
shows that the joint conditional characteristic function is
a martingale and uses this result to derive a partial dif-
ferential-integral equation for the function. Section 5
solves this equation analytically to obtain a closed-form
expression for the function. Section 6 provides examples
for the use of the function when pricing derivative secu-
rities. Section 7 concludes.
2. The Bates Model
I first outline the assumptions and introduce the notation.
The financial market is assumed to admit no arbitrage
opportunities. Thus, there is an equivalent martingale pro-
bability measure (see Harrison and Kreps, 1979 [11]),
denoted here as 1. Random variables and stochastic
processes are defined on a probability space with as
the probability measure. An expected value taken with
respect to is denoted by . To rigorously analyze
stochastic processes, I work with a filtered probability
space 0t, where is the set of
outcomes, indexes time,

is a filtration (i.e., a
non-decreasing sequence of
P

t
P
P
,,
t
[]E
tt
-f
,P
elds
0
i
), and -fiel d
. Stochastic processes are assumed to be
adapted to
tt
0
tt
One of the assets traded in the financial market is a
riskless bond fund with a share worth
.
0
=rt
t
M
Me
0r
on
date , where 0 is an initial value and is
a risk-free interest rate, which is assumed to be constant
over time. In contexts involving asset pricing (e.g.,
valuation of derivative securities), such riskless fund is
often used as a numéraire asset, with prices of other
assets being discounted by t
t>0M
M
. Also, is often
referred to as the “risk-neutral” probability measure.
P
I focus on a stock process 0
tt, where t denotes
the price of the stock on date . The stock is allowed to
pay dividends continuously at a rate

S
tS
0
=0
, which is
assumed to be constant over time (
in the case of
no dividend). Since the stock process in the Bates model
incorporates a jump component, which results in discon-
tinuities in the stock price, it is helpful to introduce the
notion of a “left limit” of a stochastic process. In
particular, the left limit of
0
tt
S on date t is defined
as 1
mn
t
=li
SS
t
n


, where is a positive integer. If
there is a jump on date , then .
nttt
In the Bates model, the dynamics of t under P are
described by a system of two stochastic differential equa-
tions:
SS
S
1
=,
t tt
dSdtv dWUdN

 
tt
S r
(1)
2
=.
ttt
dv t
vdtv dW
 
 (2)
Equation (1) shows that the instantaneous net return on
the stock, tt
dS S
, is a sum of three distinct com-
ponents: 1) a deterministic drift term ; 2)
a stochastic diffusion term

rd

 t
1tt

1
W
vdW , and (3) a stochastic
jump term t
UdN . A process 0
tt underlying the
stochastic diffusion term is a standard Brownian motion.
A process
N0
tt underlying the stochastic jump term
is a Poisson process with intensity 0
, so that
=
t
EN t
. The processes

10
tt and are
independent of each other. A value of in-
dicates that the stock price has undergone t jumps as
of date . The magnitudes of such jumps are governed
by independent and identically distributed (i.i.d.) ran-
dom variables such that
W

0
tt
N
>0
t
N
N
t
12
,,UU
22
ln1ln1/ 2,,UN
 

(3)
where is a generic random variable having the same
distribution as 12 , and
U
,,UU>1
=1
t
and are
the distribution parameters. In Equation (1), is the
random percentage jump of the stock price given a jump
occurring at (i.e., given ). The Bates model
reduces to the Heston stochastic volatility model (Heston,
1993 [2]) if (1)
20
U
tdN
=0
, or (2) =0
and , since
these cases effectively eliminate jumps from the stock
dynamics.
2=0
Equation (2) describes a mean-reverting square root
1P need not be unique, as the financial market may be incomplete.
Copyright © 2012 SciRes. TEL
O. ZHYLYEVSKYY
402
process for the squared volatility2. This equation is bor-
rowed directly from the Heston model. A process
0
tt is a standard Brownian motion possibly cor-
related with 10
{, so that

2
W
}
tt
W12
,=
t
dWW dt
, with
1
. The process
2tt
W
12
,...UU 0, process 0
tt, and the
random variables are mutually independent.
Constants

N
,
0
, 0
, and 0
are parameters. In
order for to be almost surely (a.s.) positive so that
t and t are real-valued a.s.,
t
v
vS
and
are
assumed to satisfy a restriction 22
(see Chernov
and Ghysels, 2000 [12]).
3. Dynamics of Log-Price
Let t
s
denote the stock’s log-price, t
=ln
t
s
S. The dy-
namics of t
s
under are derived using a generalized
Itô formula for semimartingales, which allows me to
properly account for possible discontinuities in the time
path of the stock price. See Theorem 32 of Protter (1990
[13], p. 71) for details on the formula. Before applying
the Itô formula, observe that Equation (1) implies that
t and t are, in general, not equal to each other
because of the presence of the jump term; more speci-
fically, tt Thus,
P
=
t
SU

SS
SS.
t
dN =1
tt t
SS UdN
,
and therefore,
lnln= ln1.
tt t
SS UdN

Also, note that by the properties of the Poisson process,
is effectively either 0 or 1. Therefore,
t
dN


lnln =ln1=ln1.
tt t
SS UdN UdN
 
t
Hence, the generalized Itô formula applied to the
function
ln t
S indicates that the dynamics of t
s
under are described by a stochastic differential
equation
P


2
2
111
=2
lnln,
tt tt
tt
ttttt
dsdSv Sdt
SS
SSSSS

 
which is straightforward to simplify as:


1
=2ln1.
12
,,UU
-fi e l d
ttttt
dsrvdtvdWUdN

 
h
(4)
4. Martingale Property and Dynamics of
Joint Characteristic Function
My main interest lies in deriving a closed-form ex-
pression for the joint characteristic function of some
future, date- log-price and squared volatility given
their present, date-t values, where . Consider an
arbitrary date such that , and note that
since , . Equations (2) and (4), the
properties of the Poisson process and standard Brownian
motion, and the assumption of i.i.d. random variables
imply that the information contained in the
T
h
<tT
Th
<th
<tt
h relevant for conditioning the joint dis-
tribution of T
s
and T on h comprises the values
of
v
h
s
and h, and the time remaining at until ,
vhT
0
Th
. Thus, let
12
,;,,
hh
s
vT h

denote the
joint conditional characteristic function of
T
,
T
s
v
given
,
hh
s
v, evaluated at real arguments 1
and 2
.
By definition of the characteristic function,

12
is v
TT
h e


12
is v
TT
t e


,
hh
sv
12
,;
12
,;
t
,T
,T
=E
=E
|

|
.
h



t





Likewise,
,
hh
sv .
Since , the law of iterated expectations im-
plies that
h



12
12
,;

12
=
=;,,
v
TTt
v
TT
hh
T te
Es









12
,
is
is
e


,,
tt =E
EE
sv
a
t
h


.s.,
ht
vT




which shows that
12
,;

:0
,
tt ttT
svt 
,T
is a martingale. The martingale property of
 implies
that
12
,;s,= s
tt t
v



,T t0 a..Ed
In what follows, it is helpful to denote by
the dura-
tion of the time interval between and T, t=Tt
.
Also, observe that Equation (2) implies that has a
continuous time path; therefore, v. In comparison,
Equation (4) implies that
t
v
=
tt
v
t
s
may have discontinuities in
its path, with
1=ln
tt t
s
sUdN


 .
The goal is to find a solution for as a function
with continuous second order partial derivatives. Apply-
ing the generalized Itô formula,



12

12
12
12
,
, ;
, ;




1tt
dt
tW
,;
ds,
tt
, ;,,
,,
2
,,
t t
stt
t
vtt
v s
sv
rv
sv
 
=

v
dvd
 




2
t
dW
12
12
;,,
;,,
,
tt
sst t
vvt t
t t
t v
sv
2
t
t
vdt
12
,
,
, ;
vd
0.5
0.5
sv
s
vv
,
vdt
d
dt

,Nv
sv




12
12
,
,ln1
,;,,,
tt
t
tt
sv



;



t
sU






 


2In applications, the unobserved value of is often treated as an ad-
t
v
ditional parameter to estimate.
Copyright © 2012 SciRes. TEL
O. ZHYLYEVSKYY 403
and
x
y
x
where symbolic terms of the form de-
note partial derivatives /
x
  and 2/
x
y , re-
spectively.
By the properties of the Poisson process and mutual in-
dependence of and
Ut
dN ,






12
12
12
12
,; ln1,,
,;,,|
=,;ln1,,
,;,,.
ttt
ttt
tt
tt
EsUdNv
sv
EsUv
sv dt
 
 
 
 








t
Then, applying the relationship

=0
t
Ed


ownian motion, it is and the properties of the standard Br
straightforward to show that the function
 must
satisfy the following partial differential-integral etion: qua



2
12
22
,;n

12
2
l1,,
,;,,,
0=
s
tv t
tt
tt
v v
Uv
sv
 
 
 



where the arguments of the partial derivatives and the
term are omitted to shorten the notation. Note that in
the special case of
ss tvv tsvt
t
vvv
Es

 

   

(5)
r

 
dt
=0
,

12
=exp TT
is v

 
.
5. Closed-Form Solution for Joint
Characteristic Function
Solving for the joint characteristic function
he eq
solution com
in
closed form using Equation (5) presents a substantial ana-
lytical challenge. My approach to address this problem is
to first propose a general form of a solution to tua-
tion, and then analytically derive all of the -
ponents. Suppose that is of the form:





1212 12
11
,;,, =exp;,;,
tt t
t
s
vpq
is
 



v
(6)
where

12
;,p

and
12
;,q
 
are complex-
valued functions of
tytically, ano be sd

olved for anal
1
is complex-valued and constant with respect to
t
s
, t
v, and
. The expression for
i
shortly.
expression for
s provided
Differentiating the in Equation


(6):



12
12
1212 1
,;,,
=,;,,
;,,,
tt
tt
t
sv
sv
pqv

 
 
 
 




12 12 1
1212 12
;
,;,, =,;,,,
,;,, =,;,,;,,
st
t tt
vtt tt
sv sv i
svsv q
  
  




2
1212 1
,;,, =,;,,[],
,;,,
tt tt
svsv i
sv sv
 





2
12 12 12
=,;,, [;,],
ss
vvttt tq
  


and
,;,,sv
 


12 1 2
=,
;,, ,
tt
sv iq
 

wher
12
1
;,
svt t

=pdpd
 and
 
=qdqd
.

ln 1U
e
Next, recall from Equation (3) that is a
normal random variable. By assumption,pen-
dent of the information contained inusing
Equation (6),
it is inde
t. Thus,









 

12
12
12 1
12
12 1
12
2
111
,;ln1,,
,;,,
=,;,,expln1
,;,,
=,;,,expln11
=,;,,
expln121,
ttt
tt
tt t
tt
tt
tt
EsUv
sv
EsviU
sv
sv EiU
sv
ii
 

 

 



















w
res
ress
here the last equality follows from the properties of the
characteristic function of a normal random variable (see
Chung, 2001 [14], p. 156). Given this ult, it is con-
venient to exp
as follows:
 
2
11 11
=exp ln121ii
 

.
 

(7)
Then, the integral term in Equation (5) is




12
12
12 1
,;ln1,,
,;,,
=,;,,.
tt
tt
tt
EsUv
sv
sv
 
 
 
t



By plugging in the obtained expressions into Equation
(5) and simplifying it (e.g., note that is differenced
out), I get
 
 
 
12 1
2
2
121 12
; ,2
;,2;,.qiq

 
12 112
2
12 1
0= ;,;,
;,2
t
pir qv
qiq
  
 
 


 



is equation mpar-
ticular value of , the functions
Since thust hold irrespective of a
t
v()
p
and ()q
need
to solve the ng system of two
tions:
followi differential equa-

12 112
;, =;,pir q
,
 
 

 
Copyright © 2012 SciRes. TEL
O. ZHYLYEVSKYY
404



2
12 11112
2
2
;, =22;,
qiiq
12
;,2.q
 
 




Observe that the relationship
 



121 2
12
12 1
,;,,0 exp
= exp0;,
0;,
TTTT
TT
svi sv
p
qvi
 





s
im i
plies that the system has initial conditions

12
0;,=0p

and

122
0; ,=q
 
.
The system is similar, although not identical, to a
system of differential equations analyzed by Zhylyevskyy
(2010) [10] in the case of the Heston model. By appro-
priately modifying the prior analysis, a closed-formolu-
tion for and
s

p
q
0
, in the case of the Bates model
studied here, can be split into three cases. In Case (
beloter
1)
w, parame
, which implies that the square
voIn comparison, Case (2)
and ns for and
d
latility process is stochastic.
Case (3) provide solutio

p
q
when =0
, that is, under the spec stan
non-stochastic stock volatility3.
Case (1). Suppose that
ial circumces of
0
. Let
1
A
and
12
,B

be complex-vnd ctant with respect alued aons
to
, and defined as follows:


222
11
=1 2Ai
2 2
,
1
 
 
 

2
112
12 2
112
,= .
iAi
BiAi

 

Then,

12 1
2
;, =
1
2ln,
1
pr i
B
ABe
 
 
 







(8)
A

12 2
;, = ,qiA
 


1
1
A
A
Be
(9)
1

1Be


where
1
AA
and
12
,BB

at =0
as defined above.
Ca se thse (2). Suppo
but 0
. Then,
 


12 1
2
211
2
11
2
;, =
21
2
1
,
2
pri
eii
ei


 








22
12112 11
1
;, =2.
2
qeii

i
 

 
) (11
Case (3). Suppose that
(10)
=0
and =0
. Then,

12 1
2
11 2
4
;, =
4,
pri
ii
 
  


(12
)

2
;, .qi
12 1 12
=2i
 


 (13)
Together, the expression for in Equation (6),
the expression for


in Equati), and th
for
on (7e solution
and
q
(1
f
p
given byons (8
respectively (alternatively, E10) and (11) or
Eq (12)3), resp depending on the
val
Equati
quations (
ectively,
) and (9),
uations
particular
and
ues o
and
, as shown above),
joint
characteristic function
provide a closed-form, analytical expression for the
of T
s
and T
v, conditional on t
s
and
6. Applications of Joint Characteristic
The derived joint characteristic function may be em-
ployed in asset pricing applications. To illustr
provide two examples related to implementing the trans
form methods of Duffie et al. (2000) [6] and Bakshi and
Madan (2000) [7] to price derivative securities
dynamics of the Bates model. These method
in
ve
expression for
er
t
v.
Function
ate its use, I
-
under the
s require
verting a conditional characteristic function of an un-
derlying state-price ctor. Thus, knowledge of a closed-
form the characteristic function, such as
the one obtained in this paper, is essential for their imple-
mentation.
In the first example, I considthe problem of deter-
mining the values of European-style derivative securities.
Let
,,,
Ett
PXSv
denotee date-value of a Euro- th
with a strike
t
price pean-style put option
X
and time to
expiration
, gi
exerc
ven the (current) ing stock’s
ion is
allised on date d its date-
un
T
derly
, an
price t
S and squared volatility t
v. This put opt
owed to be T
value is
 
,,,0=max0,
TT T
PXSv XS. Likewise,
let
E
,,,
Ett
CXSv
be the date-t value of a correspond-
ing European-style call option; its date-T value is
,,,0=max0,
ETT T
CXSvSX. The dynamics of
t
S and t
v, under the equivalent martingale probability
measure, are described by Equations (1) and (2). Thus,
there are two state variables (comprising the state-price
vector), namely, t
S and t
v, or equivalently, (the log-
price) t
s
and t
v.
The analysis of Zhylyevskyy (2012) [15] adapted to
the case of the Bates model indicates that the valuation of
the options
3Observe from Equation (2) that the value of =0
eliminates the
diffusion component from the dynamics of .
t
v
E
P
and requires knowledge of

E
C
Copyright © 2012 SciRes. TEL
O. ZHYLYEVSKYY 405
the marginal conditional characteristic function of the
date- T log-price T
s
given t
s
and t
v. Let this fun-
ction

;,,
tt
sv
be denoted as

, where
is a real
number. By definition,

;,, =.
is
T
tt t
sv Ee
 


A closed-form expression for

;,,sv
tt

is easily
obtained aof the epression for

12
,;,,
tt
sv
s a special case x

, which was derived earlier. Namely,



0
=
=,0;,,.
is t
is v
TT t
tt
Ee
sv
;,
tt
sv,=T
Ee


Then, applying Equation (10) of Zhylyevskyy (2012)
[15], the value of

E
P is


0
,,,
=1 ;,,d,
2π
Ett
rtt
PXSv
X
eX Rsv
2
i
12
e
i








where
Re
In tur
denotes the real part of a colex-valued
number.n, can be calculated ng a put-
ca
A practical implementation of ese form for
mp
usi
ulas

E
C
ll parity relationship for European-style options (Mer-
ton, 1973 [16]):

= ,,,.
E r
tt t
PXSve Se X
 



,,,
E
tt
C XSv
th
E
P
n to cal- and would require nrical integratio

E
C
culate the term
ume
dRe
od qu
1 [17]). Not
t approach t
n of B
posed here re
ereas the cor
, which is straightforward,
ture me
(Pres 200a these forulas pr
a mfficienprice Eu
riv
r instance,
for proires a singnu
whonding fo
Bates (see Bates, 1996 [4], tion (15) on p. 77)-
quires two separate integrations.
In the second example, I cider the pro of pric-
uda
cal ap
ique (Geske and Johon, 1984
[8]) to a case of non-Black-Scholes stock ics. In
comparison to the first example in this section, which
ut
using the Gauss-Kronr
s et al.,
ore e

C
integration,
adra
bly,
o
. Fo
qu
resp
Equa
ons
thod, for exam
m
ropean-style
the fo
le
rm
blem
ns
dynam
ple
ovide
de-
rmula
merical
ula due to
ative securities under the Bates model dynamics than
the original solutioates
E
re
ing Bermn- and American-style options by building
on the methodologiproach developed by Zhylyevskyy
(2010) [10]. The approach extends the Geske-Johnson
compound-option techn
ilizes only a special case

;,, =,0;,,
tt tt
sv sv

of the joint characteristic function
, this second
example requires knowledge of the value of

12
,;,,
tt
sv

for any combination of real numbers
1
and 2
, including cases of 20
.
Let
,;,,
TTtt
fsvsv
be the joint probability density
func T
tion of
s
and T
v, conditional on t
s
and t
v. The
density function
f
is an inverse Fourier transform of
the characteristic function

 (see Shephard, 1991
[18]; Chung, 2001 [14]):



12
121 2
2
,;,,
1
=,;,,dd.
2π
TTtt
is v
TT tt
fsvsv
esv



 



In practice, numerical values of

f
can be ef-
ficiently computed using values of
 by applying a
fast Fourier transform algorithmel smoothing
(see Press ., 2001 [17]; Zh, 20[10]).
American-style put and call tions are similar to their
t t
time before
ration E
lity of an early
exerciseantially c
v ar se
sol
ption
n their Euro-
pean- and American-style Bermudan-
style option is allowed to be fore expiration,
only on a selected number ofmined dates. To
clarify the iea, let
s
with ke
ylyevskyy
op
ha
e possi
counterparts. A
exercised be
predeter
tion
rn
et al
(the
e
subst
d
10
European-style counterparts, except the American-
style ones are allowed to be exercised at any
uropean-style ones may be exercised
y on thexpiration date). Th bi
expi
onl
but
omplicates the problem of de-
termining the alue ofn American-style deivative -
curity; thus, closed-formutions are generally not
available (Epps, 2000 [19]). Bermudan-style os may
be viewed as an intermediate case betwee


=1
,,
ntt n
DsvTt
be a sequence of Bermudan-style op, where
n
D
is the value of an option that may be exercised on dates

=
j
jT t
tt n
for =1, ,jn. In the sequence,

1
D represents the
value of a European-style option, which may be ex-
ercised only once, on the expiration date, with =1n
and 1=tT.
2
D
is the value of a Bermudan-style
option that may be exercised on two dates,
1=2ttT
(i.e., half-way to expiration) and 2=tT.

34
, ,DD
are defined similarly. The limit of the sequence,
D
,
corresponds to the value of an American-style option,
which features a continuum of possible exercise dates
before expiration.
Let the exercise value of the Bermudan-style option
n
D
on its first potential exte be de-
as
ercise da 1>tt
noted
1
11
,,
tt
s
vTt.
For example,

1
st

=max 0,
X
e
Copyright © 2012 SciRes. TEL
O. ZHYLYEVSKYY
406
in the case of a put option and


1
=max 0, st
eX
in the case of a call option. Bermudan-style derivative se-
curities obey a recursive relationship:





1
11 1
11 11
1
,,
=
max,,,,,
=max
ntt
rtt
ttnttt
rtt
DsvTt
e
EsvTtDsvTt
e











where and

11 1
0
1
,,,,,
,;,,,
n
tt
s
vTtDsvTt
fsvsvt tdvds



00D

1
,; , ,
tt
f
svs v tt

12 1
,;,,
tt
can be com-
putedrting by inve
s
vt t


relationship prov
ny Bermudan-styl
approximate the price of a
tforwar

2,,
tt
DsvT t

3,,
tt
DsvTt, and t
2
, as discussed
es a way to
comice of ae derivative se-
curity, to n American-
style onevalue of . In
pr d to coute
and , and ifm-
hen
010 [10])is
methodological approach is an alternative to pricing
American-style derivative securities under the Bates m
dynamics using a finite-difference-type scheme proposed
by Chiarella et al. (2008) [9]4.
7. Conclusion
This paper contributes to the literature by solving in closed
form for the joint conditional characteristic function of
nd d volatility undep
ates model. The
ving a syste
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
,,
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mp
co
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Ds
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