=Paper=
{{Paper
|id=Vol-1763/paper02
|storemode=property
|title=
Using singular perturbated systems of differencial equations of infinite order for countable Markov chains analysis
|pdfUrl=https://ceur-ws.org/Vol-1763/paper02.pdf
|volume=Vol-1763
|authors=Sergey Vasilyev,Galina Tzareva
}}
==
Using singular perturbated systems of differencial equations of infinite order for countable Markov chains analysis
==
https://ceur-ws.org/Vol-1763/paper02.pdf
УДК 517.937+ 517.928.2+ 519.217.2
Sergey Vasilyev, Galina Tzareva G.O.
Peoples' Friendship University of Russia, Moscow, Russia
USING SINGULAR PERTURBATED SYSTEMS OF DIFFERENCIAL EQUATIONS OF
INFINITE ORDER FOR COUNTABLE MARKOV CHAINS ANALYSIS*
ABSTRACT
Tikhonov-type Cauchy problems are investigated for systems of ordinary differential equations
of infinite order with a small parameter and initial conditions. It is studying the singular
perturbated systems of ordinary differential equations of infinite order of Tikhonov-type
x = f ( x(t , g x ), y (t , g y ), t ), y == F ( x(t , g x ), y (t , g y ), t ) with the initial conditions
x(t0 , g x ) = g x , y (t0 , g y ) = g y , where x, f X , X R n are n-dimensional functions;
y , F Y , Y l1 are infinite-dimensional functions and t t0 , t1 ( t0 < t1 ), t T ,
T R ; g x X and g y Y are given vectors, > 0 is a small real parameter. The results
may be applied to the queueing networks, which arise from the modern telecommunications.
KEYWORDS
Systems of differential equations of infinite order; singular perturbated systems of differential
equations; small parameter; v countable Markov chains.
Васильев С.А., Царева Г.О.
Россиискии университет дружбы народов, г. Москва, Россия
ИСПОЛЬЗОВАНИЕ СИНГУЛЯРНО ВОЗМУЩЕННЫХ СИСТЕМ
ДИФФЕРЕНЦИАЛЬНЫХ УРАВНЕНИЙ ДЛЯ АНАЛИЗА СЧЕТНЫХ МАРКОВСКИХ
ЦЕПЕЙ
АННОТАЦИЯ
В статье исследованы задачи Коши для систем обыкновенных дифференциальных
уравнений бесконечного порядка с малым параметром тихоновского-типа
x = f ( x(t , g x ), y (t , g y ), t ), y == F ( x(t , g x ), y (t , g y ), t ) с начальными условиями
x(t0 , g x ) = g x , y (t0 , g y ) = g y , где x, f X , X R n - функции конечного числа
измерений; y , F Y , Y l1 - функции бесконечного числа измерений и t t0 , t1 (
t0 < t1 ), t T , T R ; g x X , а также g y Y заданные векторы, > 0 - малый
параметр. Результаты данной работы могут быть применены для анализа
прикладных задачах в теории массового обслуживания.
КЛЮЧЕВЫЕ СЛОВА
Системы дифференциальных уравнений бесконечного порядка; сингулярно возмущенных
системы дифференциальных уравнений; малый параметр; счетные цепи Маркова.
Introduction
The recent research of service networks with complex routing discipline in [16], [17], [18]
transport networks [1], [4], [5] faced with the problem of proving the global convergence of the solutions of
* Proceedings of the I International scientific conference "Convergent cognitive information
technologies" (Convergent’2016), Moscow, Russia, November 25-26, 2016
15
certain infinite systems of ordinary differential equations to a time-independent solution. Scattered results
of these studies, however, allow a common approach to their justification. This approach will be expounded
here. In work [11] the countable systems of differential equations with bounded Jacobi operators are
studied and the sufficient conditions of global stability and global asymptotic stability are obtained. In [10]
it was considered finite closed Jackson networks with N first come, first serve nodes and M customers.
In the limit M , N , M / N > 0 , it was got conditions when mean queue lengths are
uniformly bounded and when there exists a node where the mean queue length tends to infty under the
above limit (condensation phenomena, traffic jams), in terms of the limit distribution of the relative
utilizations of the nodes. It was deriven asymptotics of the partition function and of correlation functions.
Cauchy problems for the systems of ordinary differential equations of infinite order was
investigated A.N. Tihonov [13], K.P. Persidsky [12], O.A. Zhautykov [19], [20], Ju. Korobeinik [7] other
researchers.
It was studied the singular perturbated systems of ordinary differential equations by A.N. Tihonov
[14], A.B. Vasil’eva [15], S.A. Lomov [9] other researchers.
A particular our interest is the synthesis all these methods and its applications in
telecommunications. In this paper we apply methods from [11] for the singular perturbated systems of
ordinary differential equations of infinite order of Tikhonov-type.
TIKHONOV-TYPE CAUCHY PROBLEMS FOR SYSTEMS OF ORDINARY DIFFERENTIAL EQUATIONS OF
INFINITE ORDER WITH A SMALL PARAMETER
Let us consider Tikhonov-type Cauchy problems for systems of ordinary differential equations of
infinite order with a small parameter and initial conditions:
x = f ( x(t , g x ), y (t , g y ), t ),
y = F ( x(t , g x ), y (t , g y ), t ); (1)
x(t0 , g x ) = g x ,
(2)
y (t0 , g y ) = g y ,
n
where x , f X , X R are n-dimensional functions; y , F Y , Y l1 are infinite-dimensional
functions and t t0 , t1 ( t0 < t1 ), t T , T R ; g x X and g y Y are given vectors, > 0 is a
small real parameter; x(t , g x ) and y (t , g y ) are solutions of (1)-(2). Given functions
f ( x(t , g x ), y (t , g y ), t ) and F ( x (t , g x ), y (t , g y ), t ) are continuous functions for all variables. Let S is
an integral manifold of the system (1)-(2) in X Y T . If any point t t0 , t1
*
( x(t* ), y(t* ), t * ) S of
trajectory of this system has at least one common point on S this trajectory ( x (t , G ), y (t , g ), t ) S
belongs the integral manifold S totally. If we assume in (1)-(2) that = 0 than we have a degenerate
system of the ordinary differential equations and a problem of singular perturbations
x = f ( x (t , g x ), y (t ), t ),
0 = F ( x (t , g x ), y (t ), t ); (3)
x ( t0 , g x ) = g x ,
where the dimension of this system is less than the dimension of the system (1)-(2), since the relations
F ( x (t ), y (t ), t ) = 0 in the system (3) are the algebraic equations (not differential equations). Thus for the
system (3) we can use limited number of the initial conditions then for system (1)-(2). Most natural for this
case we can use the initial conditions x(t0 , g x ) = g x for the system (3) and the initial conditions
y (t0 , g y ) = g y disregard otherwise we get the overdefined system. We can solve the system (3) if the
equation F ( x (t ), y (t ), t ) = 0 could be solved. If it is possible to solve we can find a finite set or countable
set of the roots yq (t , g x ) = uq ( x (t , g x ), t ) where q N .
If the implicit function F ( x (t ), y (t ), t ) = 0 has not simple structure we must investigate the
question about the choice of roots. Hence we can use the roots yq (t , g x ) = uq ( x (t , g x ), t ) ( q N ) in (3)
16
and solve the degenerate system
xd = f ( xd (t , g x ), uq ( xd (t , g x ), t ), t );
(4)
yd (t0 , g x ) = g x .
Since it is not assumed that the roots yq (t , g x ) = uq ( x (t , g x ), t ) satisfy the initial conditions of the Cauchy
problem (1)-(2) ( yq (t0 ) g x , q N ), the solutions y (t , g y ) (1)-(2) and yq (t , g x ) do not close to each
other at the initial moments of time t > 0 . Also there is a very interesting question about behaviors of the
solutions x(t , g x ) of the singular perturbated problem (1)-(2) and the solutions xd (t , g x ) of the
degenerate problem (4). When t = 0 we have x(t0 , g x ) = xd (t0 , g x ) . Do these solutions close to each
other when t t0 , t1 ? The answer to this question depends on using roots yq (t , g x ) = uq ( x (t , g x ), t )
and the initial conditions which we apply for the systems (1)-(2) and (3).
LOCAL EXISTENCE THEOREM FOR CAUCHY PROBLEMS FOR SYSTEMS OF ORDINARY DIFFERENTIAL
EQUATIONS OF INFINITE ORDER
Let Tikhonov-type Cauchy problems for systems of ordinary differential equations of infinite order
with a small parameter > 0 and initial conditions (1)-(2) has a form:
z = P( z (t , G, ), t , ); z (t0 , G, ) = G,
z = ( x1 , x2 ,..., xn , y1 , y2 ,...)T ,
(5)
P( z (t , G , ), t , ) = ( f1 , f 2 ,..., f n , 1F1 , 1 F2 ,...)T ,
G = ( g x1 , g x 2 ,..., g xn , g y1 , g y 2 ,...)T
where P ( z (t , G , ), t , ) is the infinite-dimensional function; G is the given vector; t t0 , t1 (
t0 < t1 ).
Let z (t , G , ) be a continuously differentiable solution of the Cauchy problems (5) then there are
(t , G , ) = z (t , G , ) / G , (t , G , ) = z (t , G , ) / where (t , G, ) and (t , G , ) satisfy
of the system of ordinary differential equations in variations:
z = P ( z (t , G , ), t , ),
(t , G , ) = J (t , G , ) (t , G , ),
z
(t , G , ) = J (t , G , ) (t , G , ) (t , G , ); (6)
z
z (t0 , G , ) = G , (t0 , G , ) = I , (t 0 , G , ) = 0,t0 T ,
where J z (t , G , ) = ( Pi / z j ) i, j =1 is Jacobi matrix, I is an identity operator and
(t , G, ) = (Pi / )i=1 is a vector.
Theorem 1 (local existence theorem). Let P ( z (t , G , ), t , ) , J z (t , G, ) , (t , G , ) be
continuous and meet Gelder’s local condition with z U (G ) then the system (6) has only one solution, which
meet the conditions z (t0 , G , ) = G , z (t , G, ) U (G) . Thus z (t , G , ) continuously differentiable
with respect to the initial condition, and its derivative meet the equation (6).
Proof. This statement is following from [3] (theorem 3.4.4) when the unlimited operator be A = 0 . End
proof.
The behavior of the solution z (t , G , ) (5) and the nonnegative condition for the off-diagonal
elements of the matrix J z (t , G, ) is demonstrated by the following theorem.
Theorem 2. Let the solution z of (5) be z (t , G, ) l1 for any t 0 , G l1 and . The following
claims are equal: (i) the off-diagonal elements J z (t , G, ) are non-negative for any G ; (ii) for any G and
any vector h l1 , h 0, z (t , G h, ) z (t , G , ) .
Proof. Let us examine a convex set Z , and z (t , G , ) Z for any G Z , derivative (t , G, )
17
of function z (t , G , ) can be specify by simultaneous equations (6). In that case the following formula is
0 1
fair for any G , G Z :
z (t , G1 , ) z (t , G 0 , ) =
1 , (7)
= (t , ( s ), )(G1 G 0 ) ds
0
0 1
where ( s ) = (1 s)G sG , 0 s 1 .
In fact the function z (t , G , ) transfer the segment ( s ) into the curve z (t , ( s ), ) in (7). The
following formula is fair because of the continuous differentiability of function z (t , G , )
z (t , ( s ), )
z (t , ( ), ) = z (t , G 0 , ) ds.
0 s
By the formula of complex derivative
z (t , ( s ), ) z
= ( ( s )) ( s ) .
s G
1 0
Recalling that z / G = and ( s ) = G G , with = 1 we get (7). Let us suppose that
statement (i) is fair. So because of (7)
1
z (t , G h, ) z (t , G, ) = (t , ( s), )hds ,
0
where ( s ) = G sh, 0 s 1 . Because of non-negativeness of function J z (t , G, ) outside of diagonal
from (7) we get (t , ( s ), ) 0 , so (t , ( s ), ) h 0 whence we get statement (ii).
Let us suppose that (ii) is fair. Under the conditions of Theorem 1 P, J z with z U (G ) be
continuous and meet Gelder’s local condition. Let Gelder’s local condition be P P P< M 0 ,P J P< M 1 , and
*
there are numbers > 0, = min( / M 0 ,1/ M 1 ) . Let z (t , G, ) = G z (t , G, ) be a solution of (7),
t
*
where z (t , G , ) is a fixed point of Picard’s mapping ( )(t ) = P(G ( ))d under conditions
t0
t [t0 1 , t0 1 ], 1 < . Mapping is contraction with coefficient = 1M 1 < 1 . Consider the
*
approximation to solution z (t , G , ) = G z (t , G , ) = G (t t0 ) P ( z (t , G , ), t , ) . We can see that
P z (t , G , ) z (t , G , ) P=
=P z * (t , G, ) z* (t , G, ) P
1
P z (t , G , ) z(t , G , ) P,
1
z (t , G, ) z (t , G, ) =
t t
= P(G ( t0 ) P)d Pd =
t0 t0
t
= ( P(G ( t0 ) P) P)d = D.
t0
Because of the derivative of the function P is limited and P meet Gelder’s local condition with the
constant M 1 , where P P(G ( t0 ) P(G )) P(G ) P M 1 P ( t0 ) P(G ) P M 0 M 1 | t0 | , so
P D P M 0 M 1 (t t0 ) 2 / 2(1 ) , or P z (t , G, ) z (t , G , ) P M 0 M 1 (t t 0 ) 2 / 2(1 ) . Using this
estimation and for all small > 0 we have that
0 z (t , G e j , ) z (t , G , ) = e j (t t 0 )[ P (G e j ) P (G )] (G , t ),
2
where P (G , t ) P M 0 M 1 (t t 0 ) / 2(1 ) and e j is a vector, which has all coordinates equal to 0 but
j -th coordinate equal to 1 . Component i j of this inequality is given by
0 (t t0 )[ Pi (G e j ) Pi (G )] i (G, t ) . Dividing by t t0 > 0 and directing t t0 on the right,
18
considering i (G , t ) / (t t0 ) 0 we get 0 P (G e j ) P (G ) . Let us divide last expression by
and direct 0
P(G e j ) P (G) Pi
0 lim = = J ij ,
0 Gi
what is mean the fairing of statement (i). End proof.
Theorem 3. Let be Markovian mapping and G 0 , G1 X , t 0, >0 than
P z (t , G1 , ) z (t , G 0 , ) PP G1 G 0 P.
Proof. Using (6) from the proofing of theorem 4 we have
1
P z(t , G1 , ) z (t , G 0 , ) P P (t , ( s))(G1 G 0 ) P ds . (8)
0
Let function (t , ( s )) is Markovian mapping for any
P t 0, s [0,1],P (t , ( s))(G1 G 0 ) PP G1 G 0 P.
Estimating the integral, considering this inequality, we get required. End proof.
This theorem shows us the following sufficient condition for the boundedness of the norm-solution
z (t , G , ) .
* * * *
Corollary fact from theorem 3. Let G X : z (t , G , ) = G . Then P z (t , G , ) G P G G* P
with t 0, G X .
This fact we can use for solutions analysis of the systems (5).
Conclusions
The boundaries of applications and possible generalizations. Some works in the routing disciplines.
All systems can be analyzed for the global stability but with some condition that the convergence to the
steady-state solution will not coordinate-wise, but the norm. We have seen that the most serious constraints
of our methods are non-negativity of the Jacobi matrix off-diagonal elements and the availability of the first
integral, which equal to the sum of the components. It would be interesting to understand the physical
meaning of these conditions. It is necessary to remember that such systems describes the behavior of the
queue lengths on the devices. Roughly speaking, zk is the proportion of units in the queue for a service, to
which there is at least k requests (including requests, which are serviced at the moment). Non-negative
elements of the Jacobi matrix indicate that the rate of change of zk (i.e., the time derivative of zk ) can only
grow at the expense of z j with j k . It can be reduced (or decrease) only due to uk . Thus, with the increase
of the portion of queues with a minimum number of requests j in the system, the percentage change in
intensity with the minimum number of queues requests k j can only increase.
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Поступила 21.10.2016
Об авторах:
Васильев Сергей Анатольевич, доцент кафедры прикладной информатики и теории вероятностей Российского
университета дружбы народов, кандидат физико-математических наук, svasilyev@sci.pfu.edu.ru;
Царева Галина Олеговна, аспирант кафедры прикладной информатики и теории вероятностей Российского университета
дружбы народов, кандидат физико-математических наук, galinabolotova@gmail.com.
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