Title Author(s) Citation Issue Date ON ENERGY INEQUALITIES OF MIXED PROBLEMS FOR HYPERBOLIC EQUATIONS OF SECOND ORDER Rentaro, AGEMI Journal of the Faculty of Science, Hokkaido University. Ser. 1, Mathematics = 北海道大学理学部紀要, 21(3-4): 221-236 1971 DOI Doc URL http://hdl.handle.net/2115/58108 Right Type bulletin (article) Additional Information File Information JFS_HU_v21n3_4-221.pdf Instructions for use Hokkaido University Collection of Scholarly and Academic Papers : HUSCAP ONENERGYINEQUALITIESOFMIXEDPROBLEMS FORHYPERBOLICEQUATIONS OFSECONDORDER By Rentaro AGEMI ~ 1 . Introduction Let R / ' be t h e open h a l fs p a c e {ヱ =(x' , x,,) ε l{n; x' ε Hη\ xn>O} and Rt "i t sc l o s u r e . W ec o n s i d e ra h y p e r b o l i co p e r a t o ri n [0 , T]X R7~ (T>0 ): ( 1 .1 ) 2 。2 n .;:., a2 :., 0 P(t, x;D)= ~,:;;- -2I ;a j(t , x)-~~~--- I ; ajk(t, x) ー十一一 2 。t ; τ1 '" 蚯蛉j j ・ b1 '" 蛉j蛉k +( f i r s to r d e r ) I• which s a t i s f i e s (件1. 司2) 主主1 {いいい向内川 Jμk(仇 川 μ 川 μ ム 刈)川+ 向帆(仇川川ム x 川 μ 羽) α向 x 叫kμJ ω 川(伊仇 州 μ (ムμ 川 t,, 刈xx)斗)} ~乙伏 ふ J i~kρ>0 j (但1. 司3) 正仏 zムJ川z口?川 f o r any(υt, 二Z 羽 Eめ)ε[刊 0, T]X R7守~, and any non-z詑ero ~=(ぽ ~1 γ, ..一, ι)ε R/'匁£ヘ The c o n d i ュ t i o n (但1. 勾2) me朗ans t h a t P(t, x ;D) i ss t r i c t l yh y p e r b o l i c and ( 1 .3 )a s s u r e st o ne boundary condition on a mixed problem considered below ( c f . impose o ~2 ) . Here weassume t h a ta j k are symmetric. Moreover we consider the t ): f o l l o w i n gboundary o p e r a t o r on t h e boundary [0 , T]x(R n, -R" ( 1 .4 ) ~11_1 _L _j\ a B(t, x';D)= : : . V -I; bj(t, x') ~V_--c(t, 藕n ; : : 1 '" '藕j x') , 蚯 十ん (t, x ' ). Hereweassumet h a ta l lcoe伍cients i n( 1 .1 )and( 1 .4 )a r er e a lvalued , su伍Cl e n t l y smooth andc o n s t a n te x c e p ta compact s e t . In t h ec a s eo fo p e r a t o r s with c o n s t a n t coe伍cients , a n e c e s s a r y and su伍cient c o n d i t i o nf o rL 2 w e l l p o s e d n e s s1) o f a mixedproblem with homo崎 1) T hem i x e dp r o b l e m(P, βis L 2 w e l l p o s e di fa n do n l yi ft h e r ee x i s tp o s i t i v ec o n ュ s t a n t sC, T a n d1" ( 0 <1 " : : : : ;1 ' )s a t i s f y i n gt h ef o l l o w i n gp r o p e r t y :F o re v e r yj ε H1((0 , T) xR';)w i t hf=O(t<0 )t h ep r o b l e m PU=f(t>O , :J:: n>O) , Bu 二 o (t>O司工戸 0), u= 竺 =0 (t=O , :J::n>O) h a sau n i q u es o l u t i o nuEH2((0, οι T')xR~') 1~'o|li 吋 s u c ht h a t )I,!t ιcjOi 九 ):1μ R . Age/l1i 222 geneous i n i t i a l b o u n d a r yc o n d i t i o n si se s t a b l i s h e di n[ 1 ]( s e ea l s o[ 1 0 ] ) . Let P(t, x ;D)and B(t, x ' ;D)be t h ec o n s t a n tcoe伍cient o p e r a t o r sr e s u l t i n g from t(t , x ) . Thent h i sc o n d i t i o ni sw r i t t e nbyt h et e r m s f r e e z i n gt h ecoe伍cients a o f coe伍cients、 that is , ( C1 )a " "(t, x)c(t, x ' )+aη (t, x)~O and h ef o l l o w i n gq u a d r a t i c formH(t, x; σ) i n σ=(σ1 , "', (Jn 択 Rn 1i s ( C2) t p o s i t i v e semi-definite, where H(作t, 川 x; σ 剖) =(仇 仏仇7η叩 μ z口ln川る C什十 αι ,,)2(何 a,ηz口lne 引 αη肌ηn o + b 戸 )2 , αn川n 十 a;l引)(切 一(何 α= I ;aj(t, x) σj , b=I ;anj(t, x)aj ヲ j 1 o= :E bj(t, x') σj e = , I; αjk (t, x) σ3σk ・ j.k~1 When a " " c+a "> 0andH i sp o s i t i v ed e f i n i t eont h eboundary , i ti ss oc a l l e d t h eu n i f o r m l yL o p a t i n s k i ic o n d i t i o n . These f a c t sa r eprovedi n~ 2 . The purpose o ft h i sp a p e ri st o prove t h ef o l l o w i n genergy i n e q u a l i t y which i s shown i n~ 3 . Theorem. SU}ザose t h a tt h ec o n d i t i o n s (C1 )and( C2) a r es a t i s f i e d on t h e boundaゥ [0, T]x(R そ - R'~ . ) Then t h e r ee x i s t sa ρositive c o n s t a n tK s u c hthatfore v e r yr e a luEH2((0 , T)xR" t )withBu=Oon[0 , T]x(R";-R":) o l d s :forany t(0 三二 t 三三 T) t h ef o l l o w i n ge n e r g y inequali砂 h (15)lu(t, )(|l 〉 K(jl(凸)(s , );|;hllu(o ,)|||:), wl;げe Ilu( ・ )II~= Ilu( ・)1 1 ~.' ( l ln) a nd u(t , • )日 =1114(t , )||:+11 仇): I i+到?と (t)l: I tseems t o us t h a t one o f di伍culities o f ourproblemcomes from t h e -=0 and σε Jln-l f o l l o w i n gf a c t :t h e r ei s non z e r ov e c t o r (τ, σ) with Rer such t h a tL o p a t i n s k i id e t e r m i n a n t R( -r, σ) =0 and t h ec h a r a c t e r i s t i ce q u a t i o n P( -r, a, え)=0 h a s apureimaginaryd o u b l er o o twithr e s p e c tt o; f ) . However, we can a v o i dt h i s di伍culity by i n t r o d u c i n gt h e above a l g e b r a i cc o n d i t i o n s ( C1 )and( C2). Combining t h e method o ft h ep r o o fo ft h e theorem with a c e r t a i n remark, i ti s shown t h a t energy i n e q u a l i t i e so fh i g h e ro r d e ra r ev a l i d . By 2) S e e! : 2a n dr e f e ra l s ot o[4] , [ 7 ]a n d[ 8 ] . I np a r t i c u l a rc o n s i d e ro n l yT w i t hRe7" 孟 O. OnEnergyI n e q l l a1 i t i e sof!o,1i:red P r o b l e l l l sfìο rHyρ erbolic E q l l a t i oJ1s0 /SecondOrdl'r 223 t h emethodo fapproximation, we can show t h ee x i s t e n c e and t h er e g u r a l i t y o ft h es o l u t i o no f ourproblem if 戸内止 (t, x)ç正k i sp o s i t i v e de五nite. Here weu s et h ef o l l o w i n gf a c t s : Cauchy-Kowalewskytheorem[ 9 ]withr e s p e c tt o mixed problem and t h a tt h ec o n d i t i o n s (C and (C r ei n v a r i a n tunder t h e 2) a 3. Holmgren t r a n s f o r m a t i o n sl 2 ]and[ 3 ] . Concerning a l r e a d yknown r e s u l t sr e l a t e dt h i s problems s e e[ The author wishes t oe x p r e s sh i ss i n c e r eg r a t i t u d et oP r o f e s s o r T. S h i r o t af o rh i si n v a l u a b l es u g g e s t i o n s and c o n s t a n t encouragement. j) Conditions(Cj) and(C ) 2 ~2 . I nt h i ss e c t i o n we show that, i nt h ec a s eo fc o n s t a n t coe伍cients , c o n ュ )a r ean e c e s s a r y and su伍cient c o n d i t i o nf o r V-wellュ d i t i o n s( Cj) and (C 2 r e p o s e d n e s s . Throughout t h i ss e c t i o n we assume t h a t P(D) and B(D) a o t a t i o n si n[ 1 ] . homogeneous andwith c o n s t a n t coe伍cients. We use n F i r s to fa l ll e tus remarkt h a tt h ec o n d i t i o n( 1 .2 )i se q u i v a l e n tt h a t ( 2 .1 ) ( 2 .2 ) where, α, a肌十 a;, > 0 and t h eq u a d r a t i c form D(σ) = (α山 + a;,)(α2 +e) 一 (a nα +b )2 i sp o s i t i v e de五nite , band ea r e def ned i n~ 1 . L e t P(" σ, ).)=,2-2iα, -2訂za ι",).+α 仏,ι口",À ynomla 心1 f o r P(D) and l e t. )I(ケ"σ剖)(υ). (ケ"σ叫)) be a roo叫t i n. )o f P(ケ" ).λ, σ 引)=0 whichh a sp o s i t i v e( n e g a t i v e )imaginaryp a r tf o r, ε c = {,: Re, >O} r e s p e c t ュ 1 .3 )theya r ew r i t t e nbyt h eformi nC , : i v e l y . Thenby( ).ic(ケ', σ剖 a )=α仏?η」 中; aJ where t h es q u a r e ro∞Ot()3iおs determined such 出 t ha此t Re ( )芦f>O i H fI R r 4 F Moreover we c o n s i d e r ).ic(" σ) t obe c o n t i n u o u s l y extended t o C+x Rη1 w here C 十 is t h ec l o s u r eo f C. By t h ec h o i c eo ft h es q u a r er o o ti t i m p l i e s > , >0. (ロ2.3剖) (置 I川 { }ρ 灼 J打川)川(ド(α仇nn+ 口? where t h eb r a c k e t {}吉 iおs t h e悶 s ame one i n. ) (ケ"σ剖) . Tog e ta n e c e s s a r y and su伍cient c o n d i t i o nf o r Lにwell-posedness , z e r o s o fL o p a t i n s k i id e t e r m i n a n t R(" σ) i nC x[l" 1 and t h eb e h a v i o ro ft h e re同 f l e c t i o n coe伍cient C(" σ) n e a rz e r o sp l a yan i m p o r t a n tr o l e . I nt h i s case, : l ) See t h e remark i nt h e end o ft h e paper R .Agemi 2 2 4 ( 2 .4 ) R(r:, σ) =i ) . i(r:, = σ)-ió-cr: 一正a}~} ι 伝 五ム斗? 一2 丘i(何 a 肌n?勾"Q- C(ケr:,川σド a (ドd(日)-ió 一口} / R( r:, a ) Applying now t h er e s u l t si n[ 1 ]t ot h i sc a s e we o b t a i nt h ef o l l o w i n g w e l l p o s e d n e s s . c r i t e r i af o rL2Theorem. ( A ) l ft h emixedproblem(P, B) i s V-weZZ-posed, t h e n5 (r : )= {σεBn1; i sind,φendent ofr: ε(\. ( B ) Let5(r : )( = 5 )beind,φendent of: rE(! . Then t h emixedproblem (P, B) i s V・ wellアosed i fand only グ the r e f l e c t i o n coφ、cient C(r:, σ) i s r o=O o r(r:o , σ。)ε(!+ X 5 . boundedi na neighbourカood of(r:o , σ。)手 o withRe: R(r:, σ)=O} As a s p e c i a lc a s eo f( B ) we s e et h a t B )s a t i s f i e st h eu n i f o r m l y Lo.ρatinskii c o n d i t i o n( t h a t is, i f loranynonz e r o (r:, σ)εC xRn-l) , t h e nt h emixedproblem(P, B ) (c)ザ (P, R(r:, σ) ,* 0 i sV-wellアosed. Using t h e theoremwe s h a l l show t h a tt h ec o n d i t i o n s( C1 )and ( C2) a r e an e c e s s a r y and su伍cient c o n d i t i o n sf o rV w e l l p o s e d n e s s . To prove t h i s we need t h ef o l l o w i n g lemmas. . Lemma2 .1 ( i ) lf LlnnC+ ι 手一 (a nn +a~J} , t h e n R( r:, 0) 手 o i n C 十一 {O} . ( i i ) l fa n n c+ ι= 一 (dMz+ai)J , then R(T, O)=O i n f ト and C(r:, σ) i sn o t ) (r:oε 0,). boundedi nanyneighbourhoodof(r: o, 0 Proof By the choise o ft h e square r o o tweg e t R( r:, 0 )=-a;;,! {ω +an+(a nn + α討を} : r, C (け )={a仏 九 ι η附zυ叫肌P花ρ& whichpr oves t h e lemma. H e r e a f t e r we mayassume thatσ 手 O. Now i tf o l l o w s from( 2 . 4 )t h a t R(r:, σ)=0 i m p l i e s (但2.5町) F(ケM 刊,川 σ剖) = {(何a仏 ιιιμ 川肌4日?山 ημa +( a n n c +a n ) ( a n n + 同}r:ー (annó+by ー (a n "e-b 2 )=0 , where t h ef フr s te q u a l i t yi s a de五nition. OnEnergyl刀 equaliti,目。>/ MixedProblemsforH y p e r b o l i cE q u a t i o n s01SecondOrder 225 Ther o o t si n' !o f F(!', σ)=0 a問 ( 2 . 6 ) -i{(仏mC + ι)(a側b 十 b) +'(annα -anb)} 土 (H(σ)- a'肌D(a))ま ( a n n C+a n )2 一(仇η +a~) whereH(σ) i st h eq u a d r a t i cf o r m.i n( C 2 . 6 )i ti ss e e nt h a t R(勿, σ) . ) From( 2 手o f o r any r e a l ηif H(σ)-an"D(σ)>0 and R(!', σ) 手 o f o r any ! ' E0十 if H(σ)-an"D(σ)<0. Nowwe 五rst c o n s i d e rt h ec a s et h a t( a " " c+a n )2 学 G肌 + a~ and i n v e s t i g a t e z e r o so fL o p a t i n s k i i determinanta c c o r d i n gt oa s i g no fH (σ)-annD(σ). Lemma2 . 2 . Supposet h a t(a""c+ ι)2手 a n " +a~ andH(ao)-annD{ao)>O forsome σ。手 O. Then ( i ) R(祢 σ) = 1 =0 forany real η , (ii) ザ annc+a,, >O , R(!', σ。)手 o ( i i i ) i fannc+a,, <O , R(!'o , forany!'EO+ , σ。)=0 f orsome! ' o E C + . ReJηark 1 ) Int h i s lemmawemayassume t h a ta n n c+ ι 手 O. In fact , i fa"nc+ ι=0, thenH(σ。)=ー (α肌 +a~)(aη点。+ b ) 2whereモo =ó(σ。) andbo=b(σ。). o Henceby(1. 3), ( 2 . 1 )and( 2 . 2 )wehaveH(σ。)-annD(ao)<O. Thisc o n t r a d i c t s t h ea s s u m p t i o n . 2 ) I f annc+a,, <O andH(σ)-annD(σ) i sp o s i t i v e de五nite, then by t h e p r o o fo ft h i s lemmaS ( ! ' )depends on !'ECc ・ Proof ザ LeJnma 2 .2 . From t h eremarkmentionedb e f o r et h i s lemma oprove ( i i )and( i i i ) . I ti so b v i o u st h a t R(τ, σ。) = 1 =0 e x c e p tr o o t s i t su伍cies t e t ! ' obea r o o to fF(!', σ。) =O . Then i tf o l l o w s from i n' !o fF(!', σ。)=0. L ( 2 . 4 )( 2 . 5 )t h a t ) } R(!'o , σ0) =-a~,~ [{(annC+ 仇ho+i(αnnÓO +b o +{{ド(aω 九,匁削肌 ι 仏 nn 九 日山 ~nC η〆 什 ,cC叶+ αιω 川) 勾J Byt h ec h o i c eo ft h es q u a r er o o twe o b t a i n 1-2a~~~(annc 十 α"ho+i(annóo+bo)f i f annc+an>O , l i f a開c+an<O , R(!'o , σ。)={L J 0 fromwhichoura s s e r t i o nf o l l o w sd i r e c t l y . Remark2 )i sprovedbyt h eabove e q u a l i t yand( 2 . 6 ) . Lemma2 .3 . Supposet h a t(annc+ ι)2 手 ann+a;, andH(ao)-annD(σ。)豆 O forsome σ。 =1= 0. Then (i ) R(!', σ。)学 o forany 日 C" R .Agemi 2 2 6 ( i i ) ザ H(σ。)>0 and annc 十仇 >0 , R(勾, σ。)手 o foranyreal η , (iii) ザ H(σ。)=0 and annc+ αよ 0 , R(旬。, σ。) =0 f or somer e a l1 ) 0' b u t )i sboundedi na ne留hbourhood of(句。, σ仏 C('r, a (iv) ザ H(σ。)<0 o ri fH(σ。)孟 o anda n n c+an< 0, t h e r ee x i s t sareal りo s u c ht h a t R(旬。, σ。)=0 andC(!', σ) i sn o tboundedi nanyneighbourhoodof (勿0 , σ ω心0) 向 I nt h ec a s e伊 (iii) wema 可 y 出 a ss叩 ume 出 t ha 叫t 仇 a 削nz日問n叩 C + α 仇n 守手丘 O . I nfact , i f annC+ ι=0 t h e nby( 2 . 1 )wehaveH(σ。)=一 (ann + 吟) ( a n no +bo)2 豆 O. R仰仰zark 沈 kι. ProofofLemma2 .3 . ( i )i sprovedb e f o r eLe mma2 . 2 . By ( 2 . 6 )and t h ea s s u m p t i o no ft h e lemma t h ee q u a t i o n F(勿, σ。)=0 i n ηhas two r e a l x c e p tr o o t si n ηof r o o t s( c o u n t i n gt h em u l t i p l i c i t y ) . C l e a r l y R(勾, σ。)学 o e F(勾, σ。)=0. Let りo b ear o o to f F(勿, ao). Theni tf o l l o w s from (2.3) , ( 2 . 4 ) and( 2 . 5 )t h a t ( 2 . 7 ) R(句。, σ。) I -----,'" 2ia;~ ~ (~nC 十 a,,) η。 + a n n モ+b o f l ' " " - " ' / " --,.,." " J i f G(σ。)>0 , l i f O ={ 0 G(σ。):::;:0 , and t h enumerator { ,~" o f C(旬。, σ。) ( 2 . 8 ) i f G(σ。)ミ 0 , 0 ={~. ,(, < . . . 1 1-2iaム~ {(annc 十 a,,) 布。 +a""óo+bof i f G(ao)>O , where α。 =α(σ。) andG(σ。)= {(annc+ ι)η。+ a n n モ }{ ( a o n n+a;) η。 -(annoo-anbo)}. O+b Tod e t e r m i n eas i g no fG(σ。) wef i r s tremarkt h ef o l l o w i n gf a c t s . Subュ ) f ( a n n c+an )andi 仲間α -a"d)f(a nn +a ; )a sv a l u e so f!' i n t o s t i t u t i n g -i(αnnÓ +b F(!', σ) weg e td i r e c t l yt h ef o l l o w i n gr e l a t i o n s : ペ( 』企当山 F t川a\ = _ a) ωC九 , ) 向 a 一 (伊a九 ω 一 ,帥d w,HC(帥 ( 2 . 9 ) F (annα-dt.ρ= 一五 nD(a) -_!_回2 ) 2, 1am+aiz-jam+G2(α "n +a; wh町e I(σ)=(annC+ ι)(a"no-anb ) + 仲間 +a;)(a"n ó + b )ー Hencei tf o l l o w sfrom ( 1 .3), ( 2 . 1 )and( 2 . 2 )t h a t ( 2 . 1 0 ) ~oreover F (a"nO 二坐 t, σ) is 時ative ¥ an匁 +a匁/ d e f i n i t e . byt h ede五nition o fI(σ) wehavet h ef o l l o w i n gr e l a t i o n s : ( 2 . 1 1 ) anno-a"b a畑 +a; / ann +b¥_ 1(σ) c+a ,,) ¥ a"nc+an) ( a " n+a ; ) ( a " n 一一一 - , OnEnergyInequaliti,目 ( 2 . 1 2 ) of MixedProblemsforHypelるo/ic E q u a t i o n sofS e c o l l dOrder 2 2 7 一 (ann C+ ι)(α開ó+b) 一 (a肌α -anb) ¥ (α肌ó+b ( a n " c+a n J2 一 (an " +a ; ) ¥ annc 十 anJ -I(σ) (α問 c+ α,,){(α附c+ αJ ー (a"n +a ; ) }, wheret h ef i r s ttermo ft h el e f thando f( 2 .1 2 )i sav a l u ea twhicht h ef u n c ュ t i o nF(勿, σ) in り take anextremum. n " c+ ι>(anJd)E , because f o ra n o t h e r Wec o n s i d e ro n l yt h ec a s et h a ta c a s e (iiト(iv) a回 proved by t h e same method. 1 nt h i s c a s e F(勿, σ) i sa c o n c a v ef u n c t i o ni nη. 、。一 24a 一品 'hu- G 一一+一一+ 向一四%一肌 a一 a一間一 間一 G一 <> z 一α ddpM 一 均一弘弘一 h h 一一 G 一 aa り仇 <> This showst h a t G(σ。)>0. け一'引h け一 ( i i ) Thec a s et h a tH(uo)>O. 1 tf o l l o w sfrom(2.9)一(2.12) t h a tI(σ。)*0, i f I(σ。)>0 , i f I(σ。)<0. Henceby( 2 . 6 )wehaveR(旬。, σ。)手 O. ( i i i ) Thec a s et h a tH(σ。)=0. By ( 2 . 9 ) we s e e thatη。=一 (a開ó o + b o ) f i sar o o tin り of F(勿, σ。) =O . Hencebyt h esamea st h ec a s e( i i ) R(iη, σ。)手 o f o rany ザヲ匂o. From( 2 . 7 )and( 2 . 8 )i ti se a s i l ys e e nt h a tR(句。, σ) =0andt h enumeratoro f C(句。, σ。) i se q u a lt oz e r o . Top r o v et h a t C('Z', σ) i s bounded i n a neighbourhood o f (旬。, σ。) we c o n s i d e rt h ee x p a n s i o no f i 1 : ! :('Z', σ) n e a r(旬。, σ。). ( c f .[ 6 ] ) . L e t P(τ, σ, i1)=('Z'-i-r 1 (σ, i1))('Z'-i-r2 (σ,i1)) where 'Z'j(σ,i1) ( j=1 .2 )a r er e a la n a l y t i candd i s t i n c tandmoreoverl e t1 i 0bear o o t io f P(句。, σ。,え) =O . Thenw i t h o u tr e s t r i c t i o nwemayassemet h a t7 } 0 = i n1 (α同c+ ι) 'Z'1(σ0 , i ( 0 )andん= -(a,,7}o+ b o ) f a " n . S i n c e1 i 0i s double , wehave 空豆 (σ0 , i ( 0 ) =0 1 i and~与(σ0 , 1 i )*O. Hence t h e r ee x i s t sar e a la n a l y t i cf u n c t i o n i10(σ) such o 2 1 i t h a t i1川)=i10 and 竺l_ (u, ん(σ)) =0 i nas m a l lneighbourhoodo fUo ・ Now 。え l e t u ss e t l'Z' 一 η。= 'Z'1(σ, i1)-'Z'I(σ0 ,え。) ( , 1 ,\ ,, 1 哨 ('1'\/' '1'¥ ='Z'I(σ,ん (σ)) -'Z'I(σ0 , i(0) 十一 (σ))( え- 1 i 0 (σ)r +・ ¥ -,. / ., . , 2 -1(σ,ぇ。 . -, . / u Le te(~_) bet h es q u a r er o o tof ði1白\ \ノ 一 (2 i-r +'Z'1(σ,'i10(σ)) ith posi・ , ' //竺互い,ん(σ)) , ' /w 、\ U I 凱2 ¥ ' U t i v e( n e g a t i v e )i m a g i n a r yp a r tr e s p e c t i v e l y . Then f o ranarbitrarily nearσo weo b t a i nt h ee x p a n s i o ni n~:!: o f i1:!:('Z', σ) n e a r旬。: 五xedσ R .Agemi 2 2 8 タ : f :('r, where Cj(σ) a児 real. σ) =À(σ)+e土十 C2 (σ)(e土 )2+ ・ Us i n gん À o(何 ωo)=À 向 σ ん0= 一(悼 α 2り) 一 e++o((ぽぱ Eι;)門 C('r, σ。)ー e -+0@-) 2 ) S i n c e W/~-I =1 and e(~-)→ o when 'r• i1)o, c(ケ'r, σ司) i s bounded i na neighbourhoodo f(収i守仇o , σ向 ω0) (i討V 吋同 ) The悶 c as問 et出 ha 叫tH(伊 ω心 向 σ 0)<0. Fro ひ m(ρ2.ρ9 別)and (ρ2.10 的)we “se 白 et出 ha 叫t t h e r e偲 e Xlおst岱 s a ro∞O叫tη仇o between(α 仇ηnnα 向o 一 G 仇n点 凶 bO0心 0川 )//(αιn加η+α a~) and 一 (annÓ o +b o ) / ( a n n c+a ",.). Hence we havet h a t G(σ。) <O . C o n s e q u e n t l yi tf o l l o w s from ( 2 . 7 )and( 2 . 8 )t h a t t h ec o n c l u s i o no f( i v )i nt h elemmai sv a l i d . a n n c+an ) 2=an "+a~. I nt h ec a s et h a t Next¥ we c o n s i d e rt h ec a s et h a t( annC+a s eo n l yLe mma 2 .1f o ro u ra i m . n=-(a n n+ α~)吉 we u Lemma2 . 4 . SψÞjJose t h a ta " n C+an=(a,日, +a n )き . Then (i)ザ (annC+ ι)(α肌Óo +b n b ) =0forsome σ。 *0, R('r, σ。)*0 ) +(a nnα。 - a o o i nC 汁 ( i i ) i f(annc+ ι) (anno+bo +(annα。 -a"b件 o forsome σ。 *0, R('r, σ) 学 O ) i n0+andt h ec o n c l u s i o n sof(ii) , (必), (倒的 Lemma ( 2 . 3 )a r ev a l i da c c o r d i n g ω H(σ。)>0, H(σ。)=0, H(σ。)<0 re,ゆ ectively. Proof We prove o n l y( i )b e c a u s e( i i )i s proved by same method i n Lemma2 . 3 . I nt h ec a s e(iり) F(什'r, σ的 ω o)=a ι?η帥 z f o l l o w si m m e d i a t e l yfrom( 1 .司3), ( 2 . 1 )and( 2 . 2 ) . Using Theorem (A), (B), ( C ) and lemmas (2.1)一(2.4) we can show t h e f o l l o w i n g Theorem2 .5 . Themixedproblem(P, B )i sV-ωell-posed ザ and o n l y i fannc+ α之 o andthequadraticformH(σ) i sρositive semi-de兵nite. Proof 1 . Su伍ciency o f our c o n d i t i o n . F i r s tc o s i d e rt h ec a s et h a t annC+ ι>0 a nd H(σ)-annD(σ) i sp o s i t i v ed e f i n i t e . By t h e remark 1 o f Le mma2 .2 wemayassumet h a t a,〆 +ι>0. Note t h a t H(σ) i sp o s i t i v e di五nite a nd(α帥c+an?*a間十 a~. I nfact , t h ef i r s ta s s e r t i o nf o l l o w simmediュ a t e l y from ( 1 .3 ) and ( 2 . 2 ) . I f (annC+an)2=ann+a~ , then H(σ)-annD(σ)= ー {(annC+a n )(αnnÓ +b )+(a nnα -anbW 豆 O. Hencei tf o l l o w sfromLemma2.1 , 2 . 2 and Theorem( C )t h a tt h emixedproblem (P, B) s a t i s f i e st h eu n i f o r m l y L o p a t i n s k i ic o n d i t i o n and c o n s e q u e n t l yi ti sV w e l l p o s e d . Next c o n s i d e r t h ec a s et h a ta n n c+ ι 二三 o andH(ao)-annD(σ。)豆 o f o rsomeσ0 ・ I f H(σ。) i s h e nbylemmas 2 . 1 2 . 4t h eproblem (P, B) a l w a y sp o s i t i v ef o rsucha l lσ。, t s a t i s f i e st h eu n i f o r m l yL o p a t i n s k i ic o n d i t i o n . I fH (σ。) i snonn e g a t i v ef o r s u c ha l lσo andi nf a c t H(σ。)=0 f o rsome ao, t h e nby lemmas2 . 1 2 . 4 S(' r ) OnEnergyIn叩talities ofl ¥ 1 i x e dProblemsforH y p e r b o l i cE q u a t i o n sofSecondOrder 2 2 9 = c f o ranyT εC ト and t h er e f l e c t i o ncoe伍cient C(Tσ) i sboundedi nan e i g h ュ bourhood o f az e r oo fL o p a t i n s k i id e t e r m i n a n t . Therefore t h e problem i s V乙-well-posed b yTheorem B . 2 . N e c e s s i t yo f ourc o n d i t i o n . F i r s t百 i fα 仇n口 mC thenby lemmas 2.3 , 2 . 4andTheorem( B )theproblemi sn o t Vュ w e l l p o s e d . Secondly i f annc 十 an<O, αnnC+an 学 (α"n +a;,) and H(σ)-a肌D(σ) i sp o s i t i v e defìnite, then by t h e remark2 o f lemma 2 . 2 and Theorem( A ) t h eproblemi sn o tV w e l l p o s e d . Thirdlyi fa肌c+an<O, a"nC 十仇学仲間 +a~) andH(σ。)-annD(σ。)豆 o f o r someσ。手 0, then by Lemma 2 . 3andTheorem ( B )t h eproblem i sn o tV w e l l p o s e d . F i n a l l yi f annc 十 a n = -( an n+a;,), then .1andTheorem( B )t h eproblemi sn o tD-well幽posed. Inafn a l byLemma2 c a s en o t et h a tS(T)={ O } . Thus theproof i sc o m p l e t e . s叩 omeσ 向0 , Remark. Fromt h ep r o o fo ft h etheoremwes e et h a t(P, B )s a t i s fe st h e sp o s i t i v e u n i f o r m l yL o p a t i n s k i ic o n d i t i o ni fando n l yi fa,山C 十 an>O andH(σ) i de五 nite. ~ 3 . Energy i n e q u a l i t i e s . I nt h i ss e c t i o nweproveTheorem s t a t e di n~ 1 F i r s to fa l lwe may assume t h a t B(t, x ' :D) i s homogeneous. I n fact , wet a k ear e a lv a l u e df u n c t i o n cþ εC;;o ([O , T]xR空) withf o l l o w i n gp r o p e r t i e s : J くゆく 1 c= 1 and i n [0 , T]xR~ , _aι 十ん= 0 on [0, T]x(R~ -Rて) , oX n and s e t u=cv . Then u satis五es ~17 蛆 ov on [0 rA " " . I D , T]x(R" - R ". B(t, x ' :D)u= 一一 -'L. br'::V -c 一一 axπ;-:1 -a X j a t Hence i tf o l l o w s fromt h i s and i n v a r i a n c eo fp r i n c i p a lp a r tt h a tt h e energy i n e q u a l i t yf o ruf o l l o w s fromt h a tf o rv . Denotet h ei n n e rp r o d u c t si nV(R'nandV(R: n-Rて) by(・, . )and く. , r e s p e c t i v e l y . Furthermore s e t IluI1 2 =(u, u ) and ((U))2= くu, u ) . H e r e a f t e r we ' : ) with B(t,: x 'D)u=O on t h eboundary mayassume t h a t u εC;;o ([O, T]xR [0 , T]x(R竺 -R~). Using t h ei n t e g r a t i o nbyp a r t s we o b t a i nt h a tf o rany t(O<t<T) > - ( 3 .1) 引川, .),かう 2 3 0 R .11gemi rau , ,r; 2. ;::, / , au , au" ¥ =(iJr)|!?1 作品川 (s, .),ん (s'.))J 1 。 0) すs, +2):<an(s,., • , 0) +皇内仇, o)?:JM , o) , 7s,, o)>d5+(fown-o物的l) ラ ( 3 .2 ) 2 ) :(仇)同 )ι 仇い ニ 2(学 (s, • )一志向 (s, )fu(s,), fι (s, • ) )I ¥dt dXj j 1 +2):<山, o)7s,, o)+ 主 anj 仇, o)?: 同, 0) , 手-(s,., O)>ゐ +(lωer ordert e r m ) OX k ( 3 . 3 ) ! 1 0 dX k (ん =l , 2,, n-1) , 引仇)(s,), Ci- 同い =2(苧 (s, • ) ¥dt t r"au , +J ¥ <':~ (s, o~l at" かj (s, ・)手竺 (s, ・), ~竺 (s, dXj j--l ~,,, ? ・, 0);}2+ dX n ~, au . 'ax ,," •) ¥ I ! 0 1 <ann(s,., 0 ) ::O<_ (s, ....,. ・, 0) ,一一 (s, ・, 0)> ,. aX n -2< 竺 (s, • , 0) 上IGj(s,, O) 子竺 (s,., O)> dt dXj j~l -JZ1<川, 0) と同, 0) ,ーと仇, 0) >い +(lowerorderterm). n t e g r a lo ff o l l o w i n gt y p e : Here “ lower orderterm" means an i ):θu au whose coe伍cients a ( ab i l i n e a rform i n u , ー, ~~ r ea t a t ' aヱ3 most 五rst d e r i v a t i v e so ft h o s eo fP andB )d s. Consider t h ef o l l o w i n gi n t e g r a l : ( 3 .4 ) 2('((Pu)(5,), A(s, )h)+ む (s, • )手 (s,.•) ' ) d s, J 0 ¥' . a t j 1 ".. aX j. ' ) ~ whereA(t, x ) and Aj(t, x )a r er e a lv a l u e d and d e t e r m i n e dl a t e ro n . By t h e same c a l c u l a t i o na s (3.1) , ( 3 . 2 ) and ( 3 . 3 )t h ep a r t (.,.)日 of t h e i n t e g r a l( 3 . 4 )becomes OnEnergyI n e q u a l i t i e sofl ' v f i x e dProblemsforH y p e r b o l i cE q u a t i o n sofSecondOrder 2 3 1 )1 ~:ペ) + 2 (~:η)' J ( 3 .5 ) [ ( A (s , . .)一 ~:t(S, .,.))' L :A-j 仇)ー何 ( A(s )曻t(s,.), , . ,. 曻 J+2(一肌), ¥曻t, . ,. j = ,. , 曻 Xj, . +土 ( ~凶凶 A(仇ム介川.→)同 α向川 j卯μk ム.k~1川\、 j , d X j dX k /J I Using t h er e l a t i o n (Bu)(t , X' , 0)=0 and d e n o t i n g f lx,, ~o=f(t, x' , 0 )t h e boundaryp a r to ft h ei n t e g r a l( 3 . 4 )becomes <~2(annc 十 an)A 十 (ann C 2 + 1)Anf 一一! i j;i218uL 机 曻tI x _ . o '一一 曻t . . . . , Ix_~o "J >ds A ・ 4 d n G d qd η pι ' o G ,, 十 A n G'S 3 +6 ' oz n u 町一一 an oj > B 以 vA ,、 d <c gOM ++ J汁 伽一白川 ¥ ' •.•. 却と ( 3 . 6 ) 、 rla, l +~日 t;; 宇玄1, <{い仰引均仇(何 aωη 肌ηnbj+切叫 G叫仇向川 刈nn j)A ん加川 k汁川十叫(ι 川ηJ ω 九 あ nιυ 帆 叫 bþ j片bι い£ ム Jo ν J.IL 凡 空竺 u.んj Iη >ds. 曻xk IXnco F i r s t we s e et h a tt h eq u a d r a t i c formc o r r e s p o n d i n gt o( 3 . 5 )i sp o s i t i v e de五nite i f and o n l yi f A>O and n o n z e r o~ε Rn. Put ち = L :(A2ajk-2ajAkA-AjAk)~j~k>0 L :Aj(t, x) σj where ~=(σ, ι). f o rany Then by r e w r i t i n g t h i sc o n d i t i o n weg e t ( 3 . 7 ) A ( 3 . 8 ) >0 , a nn N-2a n AAη -A~>O , ( 3 . 9 ) t h ef o l l o w i n gq u a d r a t i cformL(t, X: σ) inσis p o s i t i v edefinite, where L(μ;σ) =(何G刷 一(何 仇?勾m α るη +a~) 芝ちラ2 十 2(拘 b十α 仇η点α 叫 刈)An芝~ 一 (似 α2 十 E的)A~し, and α, b, bandea r ed e f i n e di n~ 1 . Nextwe s e et h a tt h eq u a d r a t i c formc o r r e s p o n d i n gt o( 3 . 6 )i sp o s i t i v e semi-de負nite i fando n l yi f ont h eboundary ( 3 .1 0 ) ( 3 .1 1 ) 2 2(annc 十 ι )A +( a c +1)A n 孟 n n 0 , t h ef o l l o w i n gq u a d r a t i cform J(ムど ;σ) definite , inσis n e g a t i v es e m i ュ 2 3 2 R . Age/lli where J(伊μ , x'勺; σ判) ニベ{(何a nn b2 一付 十 2A ηm ahybv2 8 Gι附 n) ,))(μ仇肌 ιηnn〆CC+ α 仏仇叫川 刈,)川 n))(α仇n削nn削点 a〆c+a C 川 偽 一(何dannc ω nn n〆 mn cb α叫) ι刈 ω川 判{(何九 利 一 (何 仇ηn九n C2 G M u l t i p l y i n g J(伊t, X i v e s i m p l ec a l c u l a t i o ng ' ;σ引) by (μG匁肌n〆c +an) 2as (β3 悶 αι (何 z口?ηz 問戸 九'"問 〆 )(a肌ぬ一 α叫)ト一(何 αι ,Cc+a 仏仇 αι 十{ (ほ 川,,)刈,)川 ω削肌 九 九 n川nn肌ηz C2 nnn ω + Aπ ヤ ( a n n c +ι )A+(a 九 ι n削nn肌 C2 )22可(何 n)2 c +a G 削肌 C 仰肌 一(何ω G仇九凡 μ?η 匁町削 ρ 〆 , C什 G仇削肌 九〆 ,ι 什 川川ル 仇叫 匁 穴 nnカb022 一 e引)一(何ω nn nn b + 町) ω C o n s i d e rt nt h er i g h t hando f( 3 . 1 2 ) . Comュ h el a s tf a c t o ro f second term i p a r e coe伍 cients o h i sf h o s eo f H(σ). Then f powers i nco ft a c t o r with t we s h a tt h i sf a c t o ri se q u a lt e et oH(σ )/a nn . Consequently (β3 悶 b削) a川)戸悶 J σ引) = [(何G仇九向川削間 叶州 〆 c 仇刈 C什+ ω 仇n)2~ α 刈 ト一 (何αι 叫 a刈)(何 n)川 αn間n点Q+ 九引 (何Gι 訓ん州(ゆ刷 ω帥 九 nn n c+a n )22リ引 nn川 nn c + ι η間n cb μ Jηc+α 間 n) αι +{(何Gι 仇叫州 九 九 刈)(何 b糾) α叫)-(何 Gι匁nn〆C2 叫 叫州 + l抑 nn匁 b+ ω 九 叫}A η, nr 九吋 AπH( σ) ~2(annc+ , l ,/~ (0/~ ~,,, ~22 ! I+ 1¥ In l )A ( a c )! A ι¥ n n + f a ,問、 J e tu e t Now l ss A = (annc+ α n)2 ( 3 . 1 4 ) ι (annc+ ι )+a nn 十 a~ , α n日"þ Aj= 叫 Aη =-a 1バ α 肌 C 十 a ,ι) (j=I ,… , n-1) , , ' )( Herewee x t e n dt h ef u n c t i o n s c(t, x ' )andbj(t, x e .fnedon j= 1,… , n-1) d ' )andbj(t, x)= ん (t, x t h eboundaryt o[0 , T]xRて as f o l l o w s : c(t, x)=c(t, x ' ) . Thenwe s h a l l show t h a tc o n d i t i o n s( 3 . 7 )and( 3 . 8 )h o l di n [0 , T]xRn and h eboundary [0 , T]x(R マ -R,,+). c o n d i t i o n s (3.9) , ( 3 . 1 0 ) and( 3 . 1 1 )h o l d on t F i r s tby (C 1) , ( 3 ) a n d ( 2 . 1 ) t h a t r e l a t i o n s we s e e 1 . A = (a~nc2 +a ",,aη c+a~)+ α nn , a n . l l n A-A;, annA2- 2 ) 4+( a a n n C +a ,,)2 (a nn +a;,) +( =an ( a n n C +an n n+a;,)2} , n{ OnEneγgy Ine明alities o fmi工ed Pγohlems f o rHyperもolic E q u a t i o n so fS e c o n d0γdeγ 2 3 3 ( 3 .1 5 ) 2(a 仇叩 ω d九ηC十 α 仇n)A+(何M α仇削肌 dJ?η 九〆 zJCd2斗 2刊 + 1川 n=(annC+ι ) ( ( ιρ implyt h ea s s e r t i o n s on (3.7) , ( 3 . 8 ) and ( 3 . 1 0 ) . Next , a f t e ral i t t l ec o m p l i c a t e dculculation , we a r r a n g e L(σ) with r e s p e c tt o n n c+an. Thuswe s e et h a t powers i na ( 3 .1 6 ) L(σ) =(annc+ 仇)官(σ)+annD(州annC+a n ? 十 (a nn +a;J} , whereD(σ)( =D(t, x; σ)) i sd e f i n e dby( 2 . 2 ) . By(C 2), ( 1 .3), ( 2 . 1 )and( 2 . 2 )t h e c o n d i t i o n( 3 . 9 )h o l d s on t h eboundary. F i n a l l y by a s h o r tc a l c u l a t i o nt h e p a r t[]o f( 3 . 1 3 )v a n i s h e s . Hencei tf o l l o w sfrom( 3 . 1 3 )and( 3 . 1 5 )t h a t J(σ)=-H(同 {(a",什仇)2 +(αJ ( 3 . 1 7 ) Consequentlyby ( 1 .3 )and(C )t h ec o n d i t i o n( 3 . 1 1 )h o l d s on t h eboundary. 2 Suppose t h a tt h eq u a d r a t i c formL(t, x; σ) i sp o s i t i v e de凸nite i n [0 , T] xR ,,; .4) Then we s h a l l show t h e energy i n e q u a l i t y( 1 .5 ) . The f o r e g o i n g 0<t~ T) c o n s i d e r a t i o ng i v e st h a tf o rany t( /I u(~ , !2η òu (~ , 2\ T7'( ( 3 .1 8 )K d ~~-(ム・) +L ;i: _ : u(t ,'); ¥-K(r U│tl 三三 1 1 j ニ 1|lazj f t (1 T l ¥ I , A I メU ( A ' 2 ; : " メU I A V _ _ (0 , ・ ),+L: ~~-(O,・) u lf\lat ¥ ,.), A(s, ・) J((Pu)(s , " " '" ¥ 0 ¥' メU I V _ _ u (s , ・) t' " j110zj/ i i¥ :, メU +L :Aj(s, ・ )--:'.Ç ""-(s, . )) d s 'メXj'" j ! I j ニi I ¥ I ¥¥ J ' +J(lowerorderterm)I, where A and Aj a r ed e f i n e d by ( 3 . 1 4 ) and c o n s t a n t s KI and K; a r ei n ュ dependent o fu . Note t h a t ( 3 . 1 9 ) (同 (s,' ) n r :~叩パ )|lLjJZ(s, );2) ホ Using Schwarz i n e q u a l i t yi tf o l l o w s from ( 3 . 1 8 ) and ( 3 . 1 9 )t h a tf o rany t ju(t, )i|: 叫 GIllu(s, )|17t+jJ|(h)(s, )|2ゐ+ 1 :u(0 , . ) 1 [ 1 : ) S i n c e S:II(Pu)(s , .)Wds+:ilu(O ,. ・ u ιl 4 lagf'''J 一、、 、、 μ ハυ + dcd c d ,島内 u p VA pt・-E ,,d 'ji--J、I--1 E K 9H'i <= 4'b u ( 3 .2 0 ) i si n c r S e t K=K2e A ,T. Then( 3 . 2 0 )l e a d simmediatelyt ot h eenergyi n e q u a l i t y( 1 .5 ) . 3 . 1 6 ) Now we s h a l l remove t h e above a s s u m p t i o n . Note t h a t by ( L(t, x; σ) i sp o s i t i v ed i f i n i t e on t h eboundary. Then by t h eassumptionand 4) T h i sa s s u m p t i o nmayb er e m o v e da f t e r . R .Agemi 234 c o n t i n u i t yo f coe伍cients t h e r ee x i s t s as m a l lp o s i t i v ec o n s t a n t0s u c ht h a t L(t, x; σ) i sp o s i t i v e de五nite i n [0, T]xRn-lx[0, 0 ] . From t h ef o r e g o i n g 1 .5 )h o l d sf o ru w i t hi t s p a r a g r a p ht h i s shows t h a tt h ee n e r g yi n e q u a l i t y( ] . L e tu st a k ear e a lv a l u e df u n c t i o n cþ(Xn) ε s u p p o r ti n [0, T]xRn-lx[0, 0 C;;, (R~) s u c hthatψ(ι)= 1i n0 壬品三;'0/2 andc( x n ) = Oi nxn"o ands e tu= 。u+(l-cþ)u. C l e a r l yt h es u p p o r to fψu i sc o n t a i n e di n[0, T]xR匁 lX [0, 0 ] andB(ψu)=Bu ont h eb o u n d a r y . Hence cu s a t i s fe st h ee n e r g yi n e q u a l i t y ( 1 .5 ) . Byr e g a r d i n g (1-ψ)u a sas o l u t i o no fCauchyproblemf o rP(D)t h e p r o o fo fTheoremi sc o m p l e t e . F i n a l l y we remarkont h ec a s eo ft h eu n i f o r m l yL o p a t i n s k i ic o n d i t i o n . a t i s f yt h eu n i f o r m l yL o p a t i n s k i ic o n d i t i o ni f and The o p e r a t o r s P andB s o n l yi font h eboundaryannc 十 a,, >O andt h eq u a d r a t i cformH(σ) i sp o s i t i v e de五nite ( S e et h e remark o f Theorem 2 . 5 ) . Then t h ef o l l o w i n gc o r o l l a r y f o l l o w si m m e d i a t e l yfromt h ep r o o fo fTheorem( e s p e c i a l l y( 3 . 1 5 )and( 3 . 1 7 ) ) . h a tP andB Corollary. Suppose t sati.めI t h e uniformly L o p a t i n s k i i c o n d i t i o n . Then t h e r ee x i s t s ap o s i t i v ec o n s t a n tK s u c ht h a tfor eveηy r e a l u ε H2((0 , T)xR~) t h e follo叩ing e n e r g y inequaliりI h o l d s for any t (O<t 三二 T): : 1 ((u(s, "O)))~ゐ (320)iu(t,)日+ 豆 K(f}Pu)(s,. )rゐ +):(((B州,州 where ((u(t, ・, O)))~ Remark. = ((u(t, We 五rst 2 , /åu 匁 ・, 0))/+ (' : " "(ム・,.,.. 0)))2 十 L: 一 (t, ・, 。t ,. l"藕 j ( ( 0 ) ) ) 2. p r o v et h ef o l l o w i n ge n e r g yi n e q u a l i t yo fh i g h e ro r d e r . For e v e r y u ε Hm;3((0, T)xR ' : ) (m 孟 0: i n t e g e r ) with Bu=0 on t h e n e q u a l i t yh o l d s :forany tE(O , T) boundaryt h eene棺y i ( 1 .5 ) ' i!lu(ム )11i:.;2 ~K(llu(O, .) : 1 1 :1 2+1 1(pu)(O , . )1 1 1 : +j;111(Pu)(s, )ii;1 ゐ), where I l l u(s , •) '1 ,ト到す仏 )I[ j I t su伍ces t op r o v et h ec a s em =O . Thedi旺erence betweent h ep r o o fo f OnEne γ部 l n e q u a l i t i e so fJ/li x e dPγoblems f o rHyþelも olic E明 αtions o fS e c o n dOrde γ 蛄 蛄 ~U i n( 3 . 4 )and 藕k ( 1 .5 )andoneof( 1 .5 ) 'i sa sf o l l o w s . Rep1acingu by -~~-, 。t ;T> ¥ 主主も ~ moreoverBu=Oby -,!:- (Bu) ニ 0, -:!-(Bu)=O(んニ 1 ,… , n -1) respective1y, the 蚯 藕k following remaining term a r i s e s from ( 3 .1), ( 3 .2 )and ( 3 .3 ): トtト;〉〉<《(QQ 伽 lバu州 tι 川川, 刈,,叫仇) 0) , 伽 where Qj( j= 1, 2) i s aj t h orderd i f f e r e n t i a 1oparatori n ~ ,一一 (k 。t 藕k <n). Using the t r a c e inequa1ity , the above i n t e g r a li s estimatedby K{εIllu(t, .)1 ,1: +C(ε)Ii:u(t, .):1 ,: +!I;u(O ,. ) 1 1 :+i:lllu(s,. )1::ゐ} , r b i t r a r yp o s i t i v e number. To estimate _~2て where εis a a dX;' we usetheequaュ t i o n( 1 .1 ) . Combining these f a c t s with our method i n ~ 3 we obtain ( 1 .5 ) ' . Second1y t o prove the e x i s t e n c e and the r e g u 1 a r i t yo f the s 0 1 u t i o no f our prob1em we use themethod o f approximation. In fact , by theassumpュ ) a ) e-b2 i sp o s i t i v e de五nite , the condition ( C nd ( C t i o nt h a t ann>O and an 1 2 n are e q u i v a 1 e n tt o annc 十 a n 孟 o and annc+ 正1n ~ the p o s i t i v e root o f H =0 with r e s p e c tt o annc+ ιHence P and B are approximated by P and Bε which s a t i s f y the uniform1y L o p a t i n s k i i condition , where dX n .ι -(C+ ε)p+h. , 藕j Bε=Y-21bj ・ j工l 蚯 References .SHIROTA: On n e c e s s a r ya n dsu 伍 cient c n dT . AGEMIa o n d i t i o n sf o rL2-wellュ [ 1 1 R p o s e d n e s so i x e dp r o b l e m sf o rh y p e r b o l i c equations , ] o u r .F a c .S c i fm 0 ) 3 3 1 5 1( 1 9 7 HokkaidoUniv. , S e r .1, Vo. l21, N o .2, 1 [ 2 ] M.IKAWA r o b l e mf : Am i x e dp o rh y p e r b o l i ce q u a t i o n so fs e c o n do r d e rw i t h a 五 rst o r d e rd e r i v a t i v econdition, P u b .R e s .I n s t .M a t h .Sci., KyotoUniv. , 1 9 1 4 7( 1 9 6 9 ) . l5, N o .2, 1 S er . A, Vo [ : l ] M.IKAWA i x e dp r o b l e mf r d e r : On t h em o rh y p e r b o l i ce q u a t i o n so fs e c o n do w i t ht h eNeumannb o u n d a r ycondition, Osaka] o u r .Math., Vo. l7, N o .1, 2 0 3 2 2 3( 1 9 7 0 l . [ 4 ] M.IKAWA : Mixed p r o b l e mf q u a t i o nw b l i q u ed e r i v a t i v e o rt h ewavee i t ha no b o u n d a r ycondition , t p p e a r . oa [ 5 ] H .O o u n d a r yv r o b l e m sf y p e r b o l i c systems , C o r n r n . .K R E I S S : I n i t i a lb a l u ep o rh 7 7 2 9 8( 1 9 7 0 ) . lMath. , Vo . l 23 , 2 P u r eApp. [ 6 ] T i t h .SADAMATSU: Onr n i x e dp r o b l e m sf y p e r b o l i cs y s e m sof 品 rst o r d e rw o rh 2 3 6 R .Agemi c o n s t a n tcoe伍 cients , J o u r .Math.KyotoUniv. , Vol .9, No.3, 3 3 9 3 6 1( 1 9 6 9 ) . [7] R .SAKAMOTO: Mixedproblemsf o rh y p e r b o l i ce q u a t i o n s 1, J o u r .Math.Kyoto Univ. , Vo. l10, No. 2, 3 4 9 3 7 3( 1 9 7 0 ) . [8] R .SAKAMOTO: Mixedproblemsf o rh y p e r b o l i ce q u a t i o n sII , J o u r .Math.Kyoto .10, No.3, 3 7 5 4 0 1( 1 9 7 0 ) . Univ. , Vol .SHIROTA: On t h e propagation s p e e d so f mixed problems f o rh y p e r b o l i c [9] T eqa tI ons , t oa p p e a r . .SHIROTAandR .AGEMI: Onc e r t a i nmixedproblemf o rh y p e r b o l i ce q u a t i o n s [ 1 0 ] T o fh i g h e rorder, III , P r o c .JapanAcad. , Vol .45 , No. 10, 8 5 4 8 5 8( 1 9 6 9 ) . Departmento fMathematics , HokkaidoU n i v e r s i t y 9 7 0 ) ( R e c e i v e dDecember21 , 1
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