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NEW ZEALAND JOURNAL OF MATHEMATICS Volume 33 (2004), 165-180 ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND (/-CONFLUENT HYPERGEOMETRIC FUNCTIONS VlVEK SAHAI AND SHALINI SRIVASTAVA (Received October 2001) Abstract. We construct new two variable models of irreducible ^-representations of the Lie algebra sl(2, (D). The q-Mellin transformaton is defined and used to transform the models in the form of ^-difference dilation models, involving ba sic hypergeometric function 2<t>i as basis functions. All the models culminate in many special function identities and recurrence relations. 1 . Introduction Manocha [ 6 ] introduced the idea of irreducible (/-representations of the spe cial complex Lie algebra si (2, C) and developed theory centering around it. A (/-analogue of fractional calculus technique [1, 7] was used to construct models of irreducible (/-representations of si (2, C) followed by the Weisner’s method [18] to obtain identities involving (/-special functions of one and several variables. These models were in terms of (/-differintegral operators acting on (/-hypergeometric func tions 20i- Further, in [15], (/-differintegral operator models of sl(2,C) with basis functions involving k 2 +i(f>k 2 functions were constructed and a good number of iden tities were derived from them. The theory of ^-representation of Lie algebras together with the theory of q- integral transformations has also been a rich source of results in (/-special function theory. In Sahai [12, 13, 14], the (/-Euler integral transformation, which is moti vated by (/-integral representation of beta function, is utilized to obtain models in terms of (/-difference dilation operators of si ( 2, C) along with identities involving (/-special functions. Both these models, viz. (/-differintegral operator models and (/-difference dilation operator models, are of (/-representations Dq (u, a) and (u) of si ( 2, C) in the particular case u = 0. In this paper, we construct new models of (/-representations Dq (u , a) and f q (u) of si (2, C) corresponding to u ^ 0 acting on (/-confluent hypergeometric functions i<£i. We then define g-Mellin transformation, which is motivated by (/-integral representation of gamma function. The (/-Mellin transformation is the ^-analogue of Mellin integral transformation used in [5, 10]. We utilize this transformation to transform these models of si ( 2 , C) to new models involving (/-difference dilation operators with the (/-hypergeometric functions 20i as basis functions. The discus sion culminates in interesting identities and recurrence relations involving i 0 i and 20i functions. Section-wise treatment is as follows. 2000 A M S Mathematics Subject Classification: 33D80, 17B37.

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Page 1: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

NEW ZEALAND JOURNAL OF MATHEMATICS Volume 33 (2004), 165-180

ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND (/-CONFLUENT HYPERGEOMETRIC FUNCTIONS

V lV E K SAHAI AND SHALINI SRIVASTAVA

(Received October 2001)

Abstract. We construct new two variable models of irreducible ^-representations of the Lie algebra sl(2, (D). The q-Mellin transformaton is defined and used to transform the models in the form of ^-difference dilation models, involving ba­sic hypergeometric function 2<t>i as basis functions. All the models culminate in many special function identities and recurrence relations.

1 . Introduction

Manocha [6] introduced the idea of irreducible (/-representations of the spe­cial complex Lie algebra si (2, C) and developed theory centering around it. A (/-analogue of fractional calculus technique [1, 7] was used to construct models of irreducible (/-representations of si (2, C) followed by the Weisner’s method [18] to obtain identities involving (/-special functions of one and several variables. These models were in terms of (/-differintegral operators acting on (/-hypergeometric func­tions 20i- Further, in [15], (/-differintegral operator models of sl(2,C) with basis functions involving k2+i(f>k2 functions were constructed and a good number of iden­tities were derived from them.

The theory of ^-representation of Lie algebras together with the theory of q- integral transformations has also been a rich source of results in (/-special function theory. In Sahai [12, 13, 14], the (/-Euler integral transformation, which is moti­vated by (/-integral representation of beta function, is utilized to obtain models in terms of (/-difference dilation operators of si (2, C) along with identities involving (/-special functions. Both these models, viz. (/-differintegral operator models and (/-difference dilation operator models, are of (/-representations D q (u, a) and (u) of si (2, C) in the particular case u = 0.

In this paper, we construct new models of (/-representations D q (u , a) and f q (u) of si (2, C) corresponding to u ^ 0 acting on (/-confluent hypergeometric functions i<£i. We then define g-Mellin transformation, which is motivated by (/-integral representation of gamma function. The (/-Mellin transformation is the ^-analogue of Mellin integral transformation used in [5, 10]. We utilize this transformation to transform these models of si (2, C) to new models involving (/-difference dilation operators with the (/-hypergeometric functions 20i as basis functions. The discus­sion culminates in interesting identities and recurrence relations involving i 0 i and 20i functions.

Section-wise treatment is as follows.

2000 A M S Mathematics Subject Classification: 33D80, 17B37.

Page 2: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

166 VIVEK SAHAI AND SHALINI SRIVASTAVA

In Section 2, we give definitions involving hypergeometric and basic hyperge­ometric series, needed for our discussion. In Section 3, Lie algebra si (2, C) is presented along with its g-deformed version. In Section 4, we construct model of D q (—7 / 2, a) and f q (—7 / 2) in two variables acting on i<̂ i and obtain identities and recurrence relations based on it. In Section 5, we introduce g-Mellin transformation and then utilize it to transform the models given in Section 4 to ^-difference dila­tion models acting on basis functions 2<f>i- The transformed models are further used in obtaining identities and recurrence relations involving 20i- Finally, in Section 6, we give an application of these techniques to g-Laguerre polynomials.

2. Preliminaries

The generalized basic or (/-hypergeometric series r0s is defined as [3]

P*.( ;,,«) = IV r V w S\ O i . . . , b s J A^ ( b 1:q)ri- - - (bs:q)n (q:q)n .n=0(2.1)

where g-shifted factorial (a; q)n is defined by

(2-2)

In other words,( (1 - a) (1 - aq) ■ ■ • (l - aq™-1) , n = 1 , 2 , . . .

(■a'^)n ~ { 1; n==0 (2-3)[ [(1 - a q -1) (l - aq~2) ■ ■ ■ (1 - aq~n)} ; n = - l , - 2 , . . . .

The series r(f>s terminates if one of the numerator parameter is of the form q~m, m = 0 ,1 ,2 ,.. . , and q ^ 0. When 0 < \q\ < 1, the series r0s converges absolutely for all x if r < s; and for |ar| < 1 if r = s + 1. If \q\ > 1 and |jc| < , then alsor<f)s converges absolutely. It diverges for x / 0 if 0 < \q\ < 1 and r > s + 1, and if \q\ > 1 and |a;| > j ~ ~ ^ , unless it terminates.

The generalized hypergeometric series rFs is defined by [9]

\ _ ~ (a i)n ■ ■ ■ (qr)n

r " { A , . . . , A ’ ) ^ 0 (A )n '" ( /3 . ) „ » ! ’ { ' ’

where {a)n is Pochhammer’s symbol defined by

(a) = I a (a + 1) - - ' ( a + n ~ 1) = ^ 5 n = 1 ,2 ,...V ,n \ 1; n = 0. K J

The g-analogue of the binomial function is

. \ = (ffM joo ; |9| < 1; |x | < 1 (2.6)" ) (X'i V oc

The ^-analogues of the exponential functions are

Page 3: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

^-REPRESENTATIONS OF sl(2,C) 167

and

Eq 0*0 = Y j Q(n. nV = ’ kl < 1- (2-8)n = 0 ' n

We shall also make use of the function

r , ( « ) = SL^ r ( 1 ~ 9 )1~“ (2-9)eq \Q)

defined for a ^ 0 ,-1 , —2 , . . . . This is a g-analogue of the gamma function and satisfies the functional equation

r , ( a + i ) = ^ r , ( a ) . (2.10)

We need the g-analogue of Kampe de Feriet function [16]

C'E’E1 {(-,m m -*■ v) n % (7 j)m+n n f=1 (5j)m n f=1 ( * ' ) „ m\n\

(2 .11)

in the form [6]

±a -.B\B' ( (a ) : (& );(& ') . x , y ^ :E ;E ' { (c) : (c) ; (c') ’ qr r f

Y ' n/=l ( ^ L - h , 1 ':f=l fe ; Q)m nf=l (fy <?)„ ̂n f=1(e:);g)mnf=: i (e$;g)n (g;g)m(g;g)n

For r = s = 0, we denote the l.h.s. of (2.12) simply by

,A:S;jb' / (a) : (b);(b') \9c:E-,E’ ^ (c) • (e) ; (e; ) ’ x,2/y •

The ^-derivative operator is defined by

a , ( / ( * ) ) = (1_ 9)a <2-13>

where the ^-dilation operator Tx is given by

Tx ( /(* )) = /(«*)• (2-14)

The (/-integral [3] is defined by

° ° ooJ f ( t )dqt = ( 1 - 9 ) £ / ( ? n)9n. (2.15)

Page 4: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

168 VIVEK SAHAI AND SHALINI SRIVASTAVA

3. Irreducible q—representations o f sl( 2, C)

The complex Lie algebra sl(2,C) = L { S L ( 2,C )}, the Lie algebra of complex Lie group

SL (2, C) = a b c d

: a, 6, c, d G C, ad — be = 1

consists of all 2 x 2 matrices with trace zero, that is,

2 /sl(2,C) = —e

It has a basis

J + =0 -1 0 0

0 0 -1 0

satisfying the commutation relations

= ± j ± , = 2 J ° .

(3.1)

(3.2)

(3.3)

(3.4)

Let Vq be a complex vector space consisting of g-special functions with a basis {4>x | A G S'} such that the functions {f\ = limq_>i <f>\ \ A € S } form a basis of a vector space, say V. Let A(Vq) be the associative algebra of all linear operators on Vq over the complex field.

A ^-representation of si (2, C) on Vq is a mapping pq : si (2, C) —> A (Vq) satisfying the following conditions:(i) pq (ax + by) = apq (x) + bpq (y )

(ii) There exists a Lie algebra representation p of sl(2) on V such that

lim pq (x) (f)X = p[x)f\ ,q-> 1

for all x, y G sl(2, C) and a, b G C .The representation pq of sl(2, C) is said to be irreducible if there is no proper

subspace W q of Vq which is invariant under pq.Define

J f = P q( J + ), J < = P q(J~), J°q = P q( J 0), (3.5)

where J+, J~, ./“ S A (V q).Manocha [6] has defined the following commutator rules for J^-operators:

J°qJ + - q J + J ° t = J+,

q j p ~ - J~ J°q = - J ~ ,

q J + J - - J ~ J + = 292“ J , ° - ( 1 - 9 ) 92" ^ J “ , u e C . (3.6)

These commutator rules were later generalized by Sahai [11] for the 4-dimensional complex Lie algebra Q (a, b), a, b G C. Further, the commutation relations (3.6) are also equivalent to those introduced by Jimbo [4]. For details, see [6, 14, 15].

If we define an operator Cq on Vq by

c q = q J tJ 7 q ’ q q2UJq (3.7)

Page 5: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

^-REPRESENTATIONS OF sl(2,C) 169

then it is easy to check that

(3.8)

As q —> 1, the operators Jq , J~ , Jq reduce to J + , J~, J° which satisfies the com­mutation relations obeyed by si (2, C) and the operator Cq reduces to the Casimir operator C. Hence, as q —*• 1, pq reduces to a Lie algebra representation p of sl(2,C). For more details, see [6, 8].

4. Models of Irreducible q—representations

We give below new two variable models for each of the ^-representations D q («, a) and (u) corresponding to u = —7 / 2, in which case they will be denoted by D q (—7 / 2, 0;) and ] q (—7 / 2), respectively.

4.1. Representation D q (—7 / 2, a).Consider an irreducible representation D q (—7 / 2, a) of si (2, C), a, 7 G C and 7 ^

0 ,-1 , —2 ,.. . on the representation space Vq with basis {f\ | A = a + n, n G Z}, such that action of si (2, C) on Vq is given by

qx- < h . (4.1)

To find a realization of (4.1) in terms of (/-dilation operators, we choose

j ; = T - 1 ( g - ’ Tt - % - q~< zTzTt) ,

0 _Q 1 „ ’

(4.2)

with basis functions

A = a, a i l , a ± 2, . . . .

Page 6: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

170 VIVEK SAHAI AND SHALINI SRIVASTAVA

Model (4.2) obeys (4.1) and the following

J q J q — Q Jq J q = ^ ,

qJ°qJ - - J - J aq = - J ~ ,

q J + J - - J - J + = 2<TV° - (1 - q)q-'lJ°q Jj, 7 S C

as well asqJ^C, = cqj+,

j - c , — qCqJq

JqC, — C T°— Q g '

4.1.1. Identities based on model (4-2).As

fx cZ,t) = 101 ^

satisfiesr _ (1 - < T ^ ) (1 - .

( 1 - 9 )It immediately follows that

. ( . .< ) . * g :

f * (a; «)„(*»';«)„ (6"; « )„ , / \ . a

where ga = a, also satisfies

( 1 - 9 )Using the fact that

Cq (qsJq ) Cq — Cqeq (s ) , which follows from (4.4), we have

c , [ , . K - ) , ]7-1(1-,).9J q>

v /1:0;2 f a : —;b ,b z,qt \ . X ___ • 07-c' > 1 I (^?)

where

Page 7: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

^-REPRESENTATIONS OF sl(2,<C) 171

Using the expansionOO

[eq ( s J * )u ] (z , t ) = £ i n f a+n(z, t) , (4.10)n —0

where in are obtained by putting 2 = 0, we get the following identity, after suitable rescaling:

( f f ;gL ,i:Q;2 f a - - , b ' , b " z , - t / WM i l l q, 1

^ (o;«)„ / —,A n a ( 1 qn+~'\ A ( aqn \= 1 j ( ^ ( ? *) 301 ( c' J 1̂ ^ (4'U)

where it; = —l - q

4.1.2. Recurrence relations from model (4-2).The recurrence relations originating from the action of J+, J~ on f\ are given

by

(l - q x) (A + l\z) + qX1(j)1 (\\qz) = i(j>i(\;z), (4.12)

' 1^1 (A;<jz) + 1^1 (\\qz) - (A;z) = (1 - qx~~l) i^i (A - l;gz)(4.13)

respectively, where A (A; *) stands for ^

4.2. Representation |q ( —7 / 2 ).We look for an irreducible representation | 9 (—7 / 2) of sl(2,C),

7 G C — {0, —1, —2 ,... }, on the representation space Vq with basis functions {/a I A = 0 ,1 ,2 ,... } such that the action of si (2, C) on Vq is given by

7 _ nXJ + h = ------— fx+ 1 ,1 - 9

_ 1 — 0̂Jq f x = - ~ j -------------- f X - 1 ,

q 1 - q

T°qfx =q 1 - q

J q f x = ----- 71 ----------- /A ,9 l - q

(yJq Jq + 9 j ? - 9“ % ° ) A = 7/2+1 ̂ 9A/a- (4.14)(1 - 9)

Page 8: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

172 VIVEK SAHAI AND SHALINI SRIVASTAVA

To meet this requirement, we choose

J q = y ( < r 7 - J y r , - z 7 y r t )

Jq = — r - ' m - r , ) ,

rO 1 ~ 17/ 2Ttq ~ 1 - 9 ’

C, = q J p ~ +q~'<J0qJ0q - q - ‘J0q,

with basis functions

h = 1̂ 1 ( ;9> -9A+7^ * A> A = 0 ,1 ,2 , . . . .

Model (4.15) satisfies (4.3) as well as (4.4).

4.2.1. Identities based on model (4-15).As

f\ = i0 i ^ qql ; g , - g A+7^ * \

satisfies

C ,A (*, t) = ^ (2i t))( 1 - 9 )

it immediately follows that

» (* -« ) = -I;?;:; )

= E 7 7 ( V' 101 ( <£” ;9 ’ - « " +72) ± ^ ( c ' ; < ? ) n (g;<z)n V 7n=0 v ’ ^/n

satisfies

c qU{z,t) =( 1 - 9 )

Using the fact that

E , ( i SJ “ ) C , = C ,£ , K " ) ,

which follows from (4.4), we have

(1 - <r7/2) (1 - q - r ^ 1)C„ [Eq (sJq ) u] (z, t) =

( 1 - q f

,W l ( (1=5)1 . - q 1+xzt,qt01:1:0 V «2.1

(4.15)

(4.16)

(4.17)

(4.18)

(4.19)

, (4.20)

Page 9: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

^-REPRESENTATIONS OF sl(2,C) 173

where

[Eq (s J - ) u] (z, t) = ( ° : J f y l ; ) . (4.21)

The expansionOO

[Eq (Sj~ ) U] (z, t) = ^ An fn (z, t) , (4.22)71=0

leads to the following identity

/i:0;i ( a : —; —w /t - q * z t , t \{ d : </7 ; — ’ q\ l )

= S d E f c k 1 0 1 ( s ;< H ^ ( r ( 4 2 3 )

4.2.2. Recurrence relations.The recurrence relations arising from model (4.15) are given by

101 (A;*) - gA+7i0 i (\\qz) - ?A+72i0i (\;qz) = (l - qX+1) i0 i (A + 1;z ) ,(4.24)

i(f)i (\;qz) - qxi(j)i (A;z) = ( l - qx) i0 i (A - 1;q z ) , (4.25)

where i<j>i (A;z) stands for i4>i ( ;q, —qx+7z.

5. Transformed Models of si (2, C)

We introduce the (/-Mellin transformation Iq. Define

13(13-1) 00h (/?, x ) = Iq [f (wz)] = ^ - - y J eq ( - u ) u0 V (ux) dqu, (5.1)

q owhich is motivated from the (/-integral representation of gamma function, as in[17],

OO

r q (7 ) = J eq (-it ) u7_1 dqU. (5.2)0

Using the substitution 2 = ux, which gives z A z — u A u = x A x and Tzf (z) = f (qz) = Tuf (ux), we have the following transforms of certain operator expressions which are needed for the discussion.

Iq [uf (ux)] • = Eph ((3, x ) ,

Iq [uAuf(ux)\ = x A xh (P, x ) , (5.3)

where Eph (/?, x) = h ((5 + 1, x).

Page 10: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

174 VIVEK SAHAI AND SHALINI SRIVASTAVA

To obtain transformed models of D q (—7 / 2, 0;) and |q (—7 / 2), we put z = ux in models (4.2) and (4.15). Note that if pq is an irreducible representation of sl(2,C) on the representation space Vq having the basis vectors {f\ | A € S} in terms of { J + , J ~ , J q }, then the transformation Iq induces another irreducible representation crq of sl(2,C) on the representation space W q — IqVq in terms of { i f+ = IqJ + I q l , K q = I g J - I - ' t K ® = Iq j j j l - 1} with basis vectors {hx = I „ h I A € S}.

5.1 . Transformed Model of D q ( —7 / 2, 0:).

K i = r r ^ ( 1 ~ TxTt)'

K~ = ^ T - 1 (q->Tt ~Tx - ^ - ^ E l3q-''xTxTt

K = 1 Zf ^ i . (5-4)1 - q

with basis functions as

h\ [x,t) = 20i ( Q ’ Q~ ;q

Indeed,

and

9 7 ( 1 - 9 ) ? ' 5

K°qK + - q K + K ° q = K + ,

gK°qK q - K q K°q = - K ~ ,

q K + K ~ - K ~ K + = 2q~1K q — (I — q) q~y K qK q (5.5)

K + h x = q->'— ^ h x+l, q 1 ~Q

1 — aA-7/ 2K q h \ = — ^ ---------h > ,

q 1 - Q

Cqh\ = { q K + K q +q -> K °qK 0q -q- '>K°q) h x

- < - - < - 7 ( . . . )(! - q)

Moreover,qK+C'q = C'qK + ,

K~C'q = qC'qK q ,

K qC'q = CqK q. (5.7)

Page 11: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

^-REPRESENTATIONS OF sl(2,C) 175

5.1.1. Identities based on transformed model £>g (—7 /2 , a).As

is a solution of

(*, t) = ( ! ~ g 7/2) ( i ~ £ 7/2+1) qx - , hx (X] t) _ (5.8)( 1 - 9 )

the function

w(x,t) = ( aJ qq̂ c>b ^ l) ta

S (c ' ; g )n (g ;g ) n V ? ( i - 9 ) r /

is also a solution of

C > (x ,t ) = 7/2^ 1 ~2g 7/2+1V - 7 t»(*,t)- (5.10)( 1 - 9 )

Using q K + C q — C'qK + , we have

C' [eq [sKq ) u] (z, i) =( ^ f r ^ ; g ) ^ ,-■> (1 - g - ^ ) (1 - r - ' W )

( 1 “ 9 )2

x o;;!;? ( W , (5 .1 1 )V <r»-1(i-9) • 9 ’ 1 ~ ̂ /

where

r_ ( ~ ts+\ -.1 a : q 0]b',b" q ?x /c 1oN[eqr J llj (x, t) ~ f st ̂ ̂ ast . ^7. ^ 1 ̂ ̂ 51J t . (5.12)5 9 L ‘

From the expansionOO

\eq (sKq ) wj (x, i) = ^ ̂A.nha-\.n (x, £),n=0

where An is found by putting x = 0, we arrive at the following identity after suitable rescaling:

( ^ ;9)oo di W a : < f - , V , W \;1 v # : < f - y ’ 1 )

\ q̂ J OO

(l - q)qf> ,(5.13)

Page 12: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

176 VIVEK SAHAI AND SHALINI SRIVASTAVA

5.1.2. Recurrence relations from model (5.4)-The recurrence relations originating from the action of K + and K ~ on h\ are

given by

20i (A;/?;x) - qx2(f>i {\-,(3;qx) = (l - qx) 2<t>i (A + 1; /?; x ) , (5.14)

xgA-7- / ? l _ J L 20x (A;/3 + 1 ; gx) + 20i (A; /?; gx) - qx~^20i (A; /?; x)

= (1 - 9A_7) 20i (A - 1; /?; q x ) , (5.15)

( qx qP \where 20i (A; /?; x) stands for 20i ( ; q, \T-̂ )q* ) •

5.2. Transformed Model of tq (—7 / 2).

( « -7 - TxT, - Ed xTxTt\ , (5.16)

k - = ^ r - 1 (*A I - t A t) ,

1 - «7/2T(

with basis functions as

o~x aP n^+i-P \ h\ (x, t) = 201 ( ’ ql ; q, y _ ~ ^ ) 1 ■

Model (5.16) satisfies (5.5) and (5.7) and

Kqh\ =q - T - q \

l - q kx+11

K ’ hx = 1-< -e

'to. »

1 1

1—1 rH

1

1 _ qA +7 /2K°qhx = ^ -------- fcA,1 - g

C'qhx = ( q K + K - + q ~ '

(1 - g-7/2) (1

( 1 - 9qxhx. (5.17)

Page 13: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

^-REPRESENTATIONS OF sl(2,C) 177

5 .2 .1 . Identities based on transformed model t q ( —7 / 2).

As/ 0 -A a(3 QX + l - 0 \

h\{x , t ) = 201 f ' ql -,q, x j t , A = 0,1,2,

satisfies

C'qh\ (x,t) = (1 ~ Q 7/2^ 1 ~29 q*hx (x, t) . (5.18)( ! - 9 )

This, in turn, gives

, .x /1:1 ;o ( a : q13; —u ( x , t ) = 0 1:1O , ; 1-9 ’\ c . q ' , - 1

h (c';q)n («;?)„ 2011 ?7 ,9, 1 - 1 ) ’ 1 'n=0 v ’ ’ /n v̂ ’ ^/n

satisfies

C > (x, t) = (1 g 7/2) (1 / " /2+1) 9" « (x, t ) . (5.20)( I - ? )

Using C'q = qCqKq , we have

C'q [E, (s K ~ ) u] (x, t) = (1 g 7/(2l - g / 7/2+1)

(5.2D\ c -0 > 9,1 /

where/ „ • r̂/3- £ j. \

[£ , ( * jr - ) u ] ( x , t ) = J . % q)L ; ’ * ) - (5-22)\ c • y » q->1 /The expansion

OO[E9 w] (x, t) = ^ 2 Cnhn {x, t) , (5.23)

n=0gives rise to the following identity:

. ~/3. it; q~ pxt •a -q t .

r ' • rH • — ’ ic - q \ ~ q, 1

(a;g)„ m ( aQn ^ jl / 9“ n,9/3 9n+7 p V= t a r o s : 1011 o v ^ tn=0

(5.24)

Page 14: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

178 VIVEK SAHAI AND SHALINI SRIVASTAVA

5.2.2. Recurrence relations.The recurrence relations that come from (5.17) are given by

Q

= ( 1 - < 2 A) 2< M A + 1;/?;x), (5.25)

20i (A; 0 ; x ) - gA+720i (A; (3;qx) - xqx+1 13 ^ _ Q 20i (A; (3 + 1; qx)

20i (A;/3;qx) - qx2(j>i (A; /5; a?) = (l - qx) 20i (A - 1; /?; qx) , (5.26)

( q~x q^ a+7—/3 \’ ^7 ;</, q--[_q x J .

6. Conclusion

In this section, we give an application of our models to g-Laguerre polynomials. Let a > — 1 and 0 < q < 1 . Then g-Laguerre polynomials are defined by [3]

ra ( \ _ + )n , f q ” _ n+a+ A . s9/ (qm q) ̂ \ y ' 6.1 )

If we take 2: = (1 — q) x then it can be easily seen that l im ^ i- (z; q) = (x), where (x) are classical Laguerre polynomials. Consider the model (4.15) in the particular case 7 = 1 + a (that is, a model of representation ] q (— (1 + a) / 2)) with basis functions involving g-Laguerre polynomials, given as

4 = (■T(I+“ ) - TzTt - zTzTt) ,

-1

_ 1 - g(l+»)/2Tt

5 1 - 9

/ „ (* ,* ) = L ° ( z ; q ) t n. (6.2)The action of these Jg-operators on f n (z, t) will take the following form:

7n+lj f f n = r ( 1 + a ) \ * q f n + 1 ,

J— f __ ^ ru a Jn — J n —1>1 - q

14-a1 /Tf 2 ”1^= - ..f n - (6.3)

We can obtain identities involving ^-Laguerre polynomials using the method ex­plained above. For example, taking

(*’ () = § J r i A 101 ( ; 9’ ~29"+a+1) <n ( 6 '4 )n=0

Page 15: ON MODELS OF ^-REPRESENTATIONS OF sl(2, C) AND ...€¦ · ^-REPRESENTATIONS OF sl(2,C) 169 then it is easy to check that (3.8) As q —> 1, the operators Jq, J~, Jq reduce to J+,

^-REPRESENTATIONS OF sl(2,C) 179

and proceeding as in Section 4.2.1, we arrive at the following identity:

00 fn

= Ln (^<1) 1^n= 0 ' ,q)n

(6.5)

which is a special case of (4.23).The recurrence relations involving g-Laguerre polynomials can also be obtained

by using first two equations of (6.3). These will shape as

L “ ( z ; q ) - q 1+ °‘+nL Z ( q z ; q ) - z q n+a+1L°(qz ;q) = (l - ,"+>) L«+1 (z; 9) (6.6)

respectively. Eliminating (z; q) from (6.6) and (6.7) gives rise to a three term recurrence relation as follows

(l - qa+n) £ “ _ ! (qz:q) + (zq1+a+2" - ( l - <j1+“ +2" ) ) £ “ (qz;q)

+ qn ( l - q n+1) K + l (z-,q) = 0, (6.8)

Note that (6.8) is a g-analogue of the three term recurrence relation for classical Laguerre polynomials [2],

(.a + n) (x) 4- (x — 1 - a - 2n) L% (x) + (n + 1) L“ +1 (x) = 0. (6.9)

Acknowledgem ents. The authors thank the referee for his valuable suggestions which led to a better presentation of the paper.

1. M.A. Al-Bassam and H.L. Manocha, Lie theory of solutions of certain differ- integral operators, SIAM J. Math. Anal. 18 (1987), 1087-1100.

2. G.E. Andrews, R.Askey and R. Roy, Special Functions, Cambridge Univ. Press,

3. G. Gasper and M. Rahman, Basic Hypergeometric Series, Cambridge Univ. Press, 1990.

4. M. Jimbo , A q-difference analogue of U (g) and the Yang-Baxter equation, Lett. Math. Phys. 10 (1985), 63-69.

5. H.L. Manocha, Lie algebras of difference differential operators and Appell func­tion F i, J. Math. Anal. Appl. 138 (1989), 491-510.

6. H.L. Manocha, On models of irreducible q-representations of sl(2,C), Appl. Anal. 37 (1990), 19-47.

7. H.L. Manocha, and V. Sahai, On models of irreducible unitary presentations of compact Lie qroup SU(2) involvinq special functions, Indian J. Pure Appl. Math. 21 (1990), 1059-1071.

8. W. Miller, Lie Theory and Special Functions, Academic Press, 1968.9. E.D. Rainville, Special Functions, Macmillan, 1960.

and

qnL Z ( z ; q ) - L Z { q z ; q ) = - (l - qa+n) L ^ (qz; q) (6.7)

n = 1,2, . . . .

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180 VIVEK SAHAI AND SHALINI SRIVASTAVA

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Vivek SahaiDepartment of Mathematics and Astronomy Lucknow University Lucknow 226007 INDIA

[email protected]

Shalini SrivastavaDepartment of Mathematics and Astronomy Lucknow University Lucknow 226007 INDIA