Principle and Equipartition of Energy for the Modified Wave
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Annales Mathematiques Blaise Pascal 1 2 comma 1 47 hyphen 1 60 open parenthesis 2 0 0 5 closing parenthesis nnoindentHuygens quoterightAnnales .. Mathematiques principle .. and .. Blaise equipartition Pascal .. of 1 2 , 1 47 − 1 60 ( 2 0 0 5 ) energy .. for .. the .. modified .. wave .. equation n centerlineassociated ..fHuygens to .. a .. generalized ' nquad ..p radial r i n c i .. p l Laplacian e nquad and nquad equipartition nquad o f g Jamel El Kamel n centerlineChokri Yacoubf energy nquad f o r nquad the nquad modified nquad wave nquad equation g Abstract n centerlineIn this paperf a we sAnnales s considero c i a t e Mathematiques d thenquad modifiedto Blaise wavenquad equation Pascala nquad1 associated 2 , 1generalized 47 - 1 60 ( 2 0 0 5n ) quad r a d i a l nquad Laplacian g with a classHuygens of radial Laplacians ' L principle generalizing the radial and part of equipartition of n centerlinethe Laplaceenergyf endashJamel Beltrami El Kamel for operatorg the on hyperbolic modified spaces or Damek endash wave Ricci equation spaces period We show that the Huygens quoteright principle and the equipartition of n centerlineenergyassociated holdf ifChokri the inverse Yacoub of the tog Harish a endash generalized Chandra c endash function radial is a poly hyphen Laplacian nomial and that these two properties hold asymptoticallyJamel El otherwise Kamel period n centerlineSimilar resultsf Abstract were establishedg previously by BransonChokri comma Yacoub Olafsson and Schlichtkrull in the case of noncompact symmetricAbstract spaces period n centerline1 .. Introductionf In thisIn this paper paper we we consider consider the the modified modified wave wave equation equation associated associated g In Euclidean spacewith X = Ra class to the of power radial of nLaplacians of odd dimensionL generalizing comma any the solution radial u part openof parenthesis x comman centerline t closingf with parenthesisthe Laplacea class to the { of Beltrami radial operator Laplacians on hyperbolic $ L $ spacesgeneralizing or Damek the { Ricci radial part of g wave equation spaces . We show that the Huygens ' principle and the equipartition of n centerlineCapital Deltaf theenergy sub x Laplace u open hold parenthesis if−− theBeltrami inverse x comma of operator the t closing Harish parenthesis on { Chandrahyperbolic = partialdiffc { spaces function to the or power is Damek a poly of partialdiff−− - R i c c i g sub t to the power ofnomial 2 to the and power that of 2these u open two parenthesis properties x comma hold asymptotically t closing parenthesis otherwise . n centerlineis determinedf spaces bySimilar the value . We results of show its in were i-line that established tial the data Huygens in an previously arbitrarily ' principle by thin Branson shell and around , the Olafsson equipartition and of g the sphere S open parenthesisSchlichtkrull x comma in bar the t case bar closing of noncompact parenthesis symmetric period .. This spaces is Huygens . quoteright principlen centerline periodf ..energy Moreover1 hold Introduction the total if the energy inverse of the Harish −− Chandra c −− function is a poly − g Equation: open parenthesis 1 period 1 closing parenthesisn .. E open parenthesis u closing parenthesis = 2 to n centerline f nomialIn and Euclidean that these space twoX = propertiesR of odd dimension hold asymptotically , any solution otherwiseu(x; t) to . g the power of 1 integralthe sub R n vextendsingle-vextendsingle-vextendsingle-vextendsingle partialdiff to the power of partialdiff t to thewave power equation of u open parenthesis x comma t closing parenthesis vextendsingle-vextendsingle- vextendsingle-vextendsinglen centerline f Similar results to the power were of 2 established dx plus 2 to the previously power of 1 integral by Branson sub R n ,bar Olafsson nabla sub andx u g open parenthesis x comma t closing parenthesis bar to the power@ 2 of 2 dx ∆xu(x; t) = @ t2 u(x; t) n centerlinesplits eventuallyf Schlichtkrull equally into its inkinetic the and case potential of noncompact components if symmetric the initial spaces . g data are compactlyis determined supported period by the.. See value Duffin of open its square in i − bracketline tial 7 closing data square in an bracket arbitrarily and Branson opennnoindent square bracket1 nquadthin 3 closingIntroduction shell square around bracket the period sphere S(x; j t j): This is Huygens ' principle . Similar results wereMoreover established the bytotal Branson energy comma Helgason comma Olafsson comma Schlicht hyphen n hspacekrull in∗fn openf i l square l g In bracket Euclidean 4 closing space square $X bracket = comma R^ openf n squareg$ of bracket odd 8dimension closing square , any bracket solution comma$u open ( square x , bracket t 1 2 )$tothe closing squareZ bracket for the modifiedZ wave equation on Riemannian symmetric 1 @ u(x; 2 1 2 147 E(u) = 2 j@ t t)j dx + 2 j rxu(x; t) j dx (1:1) nnoindent wave equation Rn Rn splits eventually equally into its kinetic and potential components if the n [ nDelta f xinitialg u data ( are x compactly , t supported ) = n .partial See Duffin^f n partial [ 7 ] andg Branson^f 2 g f [ t ^f 2 gg u ( x ,3 ] t . ) n ] Similar results were established by Branson , Helgason , Olafsson , Schlicht - krull in [ 4 ] , [ 8 ] , [ 1 2 ] for the modified wave equation on nnoindent is determinedRiemannian by symmetric the value of its in $ i−line $ tial data in an arbitrarily thin shell around thesphere $S ( x , nmid t nmid147 ) . $ nquad This is Huygens ' principle . nquad Moreover the total energy n begin f a l i g n ∗g E ( u ) = 2 ^f 1 g n int f R n g narrowvert n partial ^f n partial g t ^f u ( x , g t ) narrowvert ^f 2 g dx + 2 ^f 1 g n int f R n g nmid nnabla f x g u ( x , t ) nmid ^f 2 g dx n tag ∗f$ ( 1 . 1 ) $g nendf a l i g n ∗g nnoindent splits eventually equally into its kinetic and potential components if the initial data are compactly supported . nquad See Duffin [ 7 ] and Branson [ 3 ] . Similar results were established by Branson , Helgason , Olafsson , Schlicht − krull in [ 4 ] , [ 8 ] , [ 1 2 ] for the modified wave equation on Riemannian symmetric n centerline f147 g J period Elkamel comma .. Ch period .. Yacoub n centerlinespaces of noncompactfJ . Elkamel type X ,=n Gquad slashCh K comma . nquad underYacoub the assumptionsg that dim X is o dd and G has only one conjugacy class of Cartan subgroups period .. Otherwise nnoindentthese phenomenaspaces may of not noncompact hold strictly type speaking $X comma = but G they do/ asymptotically K , $ under comma the assumptions that dim $ Xas $ shown by Branson comma Olafsson and Schlichtkrull in open square bracket 5 closing square bracket period nnoindentThis paperis is devoted o dd and to another $ G setting$ has comma only which one is conjugacy known to share class features of Cartan subgroups . nquad Otherwise thesewith the phenomena previous one may period not .. hold SpecificallyJ . strictly Elkamel we consider speaking , the Ch modified . , but Yacoubwave they equation do asymptotically , asEquation: shown by open Bransonspaces parenthesis of , noncompact 1Olafsson period 2 closing and type Schlichtkrull parenthesisX = G=K; ..under L sub in xthe u [ open assumptions5 ] parenthesis . that x comma dim tX closing parenthesis = partialdiffis o dd to andthe powerG has of only partialdiff one conjugacy sub t to the class power of of Cartan 2 to the powersubgroups of 2 u . open Oth- parenthesis xThis comma paper t closing is parenthesiserwise devoted these to another phenomena setting may not , which hold strictly is known speaking to share , but features they do withwith theinitial previous dataasymptotically one . nquad , as shownSpecifically by Branson we consider , Olafsson the and modified Schlichtkrull wave in [ equation 5 Equation: open]. parenthesis 1 period 3 closing parenthesis .. u open parenthesis x comma 0 closing parenthesis =n begin f 0 openf a l i parenthesis g n ∗g This x closing paper parenthesis is devoted comma to another partialdiff setting to the , power which of is partialdiff known tto vextendsingle- share vextendsingle-vextendsingle-vextendsingleL f x g ufeatures ( x with , the t previous sub) t = = one0 un partial open . Specificallyparenthesis^f n partial x we comma considerg t^f closing2 theg parenthesisf modifiedt ^f 2 =gg f 1 openu parenthesis( x , xwave closing t equation parenthesis ) n tag ∗f$ ( 1 . 2 ) $g nendassociatedf a l i g n ∗g to certain second order differential operators Equation: open parenthesis 1 period 4 closing parenthesis ..@ 2 Lu = dx to the power of d to the power of 2 unnoindent sub 2 plus Awith sub A initial open parenthesis data to the powerLxu of(x; prime t) = @ subt2 u x(x; closing t) parenthesis to the power (1:2) of open parenthesis x closingwith parenthesis initial datadx to the power of du plus rho to the power of 2 u n beginon ..f opena l i g parenthesisn ∗g 0 comma plus infinity closing parenthesis period .. Following Cheacutebli and Trim egraveu(x,0)=f0(x), che comma we a-s sume that the function n partial ^f n partial g t narrowvert f t = 0 g u(x,t)=f1(x) n tag ∗f$ ( A open parenthesis x closing parenthesis behaves as follows@ : u(x; 0) = f0(x);@ tjt=0u(x; t) = f1(x) (1:3) 1bullet . A 3 open ) parenthesis $g x closing parenthesis thicksim x to the power of 2 alpha plus 1 as x searrow 0 commanendf a where l i g n ∗g alphaassociated greater minus to 2certain to the power second of order1 period differential .. More precisely operators Equation: open parenthesis 1 period 5 closing parenthesis .. A open parenthesis x closing parenthesis = x tonnoindent