Chapter1 Introduction
Abstract
Thedescriptionofvariouskindsofintegro-differentialequationsandabriefhistoryoftheiroriginandapplicationsare given.Theimportanceofinvestigationsofintegro-differential modelsispointedoutaswell.Classificationofintegro-differentialequationisgiven.Themainattentionispaidonparabolic typeintegro-differentialmodels.Inparticular,threetypesof integro-differentialequationsareconsidered.Twoofthemare basedonMaxwell’sequationsdescribingelectromagneticfield penetrationintoasubstance.Thethirdoneisobtainedby simulationofheatflow.Attheendofthechapter,asatthe endofeachchapter,thecommentsandbibliographicalnotesis given,whichconsistsofdescriptionofreferencesconcerningto thetopicconsidered.
Numerical Solutions of Three Classes of Nonlinear Parabolic Integro-Differential Equation. http://dx.doi.org/10.1016/B978-0-12-804628-9.50001-6
© 2016 Elsevier Inc. All rights reserved.
Keywords: Electromagneticfieldpenetration,Maxwell’s system,heatflowequation,integro-differentialmodels. 3
Inmathematicalmodelingofappliedtasksdifferential,integral,andintegro-differential(I-D,forshort)equationsappear veryoften.Therearenumerousscientificworksdevotedtothe investigationofdifferentialequations.Thereisavastliterature inthefieldofintegralandintegro-differentialmodelsaswell.
Thedifferentialequationsareconnectingunknownfunctions, theirderivatives,andindependentvariables.Ontheotherhand, integralequationscontaintheunknownfunctionsunderanintegralaswell.
Thetermintegro-differentialequationintheliteratureis usedinthecasewhentheequationcontainsunknownfunction togetherwithitsderivativesandwheneitherunknownfunction, oritsderivatives,orbothappearunderanintegral.
Letusrecallthegeneralclassificationofintegro-differential equations.Iftheequationcontainsderivativesofunknownfunctionofonevariablethentheintegro-differentialequationiscalled ordinaryintegro-differentialequation.Theorderofanequation isthesameasthehighest-orderderivativeoftheunknownfunctionintheequation.
Theintegro-differentialequationsoftenencounteredinmathematicsandphysicscontainderivativesofvariousvariables; therefore,theseequationsarecalledintegro-differentialequationswithpartialderivativesorpartialintegro-differentialequations.
Intheapplicationsveryoftenthereareintegro-differential equationswithpartialderivativesandmultipleintegralsaswell, forexample,Boltzmannequation[66]andKolmogorov-Feller equation[288].
Volterraisoneofthefoundersofthetheoryofintegraland integro-differentialequations.Hisworks,especiallyintheintegralandintegro-differentialequations,areoftencitedtilltoday. TheclassicalbookbyVolterra[469]iswidelyquotedintheliterature.In1884Volterra[465]beganhisresearchinthetheoryof
CHAPTER1.INTRODUCTION
integralequationsdevotedtodistributionofanelectricalcharge onasphericalpatch.Thisworkledtotheequation,whichin themodernliteratureiscalledtheintegralequationofthefirst kindwithsymmetrickernel.
Theworkonthetheoryofelasticitybecamethebeginning researchofVolterraleadingtothetheoryofpartialintegrodifferentialequations.In1909Volterra[466]hasstudiedaparticulartypeofsuchequationsandhasshownthatthisintegrodifferentialequationisequivalenttoasystemconsistingofthree linearintegralequationsandasecondorderpartialdifferential equations.
Thefirstexamplesofintegro-differentialequationswithpartialderivativesinvestigatedinthebeginningofthetwentieth centurywereinSchlesinger’sworks[417],[418],wherethefollowingequationisinvestigated:
Numerousworksinthebeginningofthetwentiethcentury weredevotedtoresearchofintegro-differentialequationsofvariouskinds.Theexcellentbibliographyinthiscaseisgiveninthe classicalbookbyVolterra[469].Inaddition,Kerimov[271],the editoroftheRussiantranslationofthisbook,hasupdated(up to1970s)thelistofreferencesonintegralandintegro-differential equations.
Letusdescribesomeclassesofmathematicalmodelsofsecondorderpromotingintensiveresearchonpartialintegro-differentialequations.
Whenwetakeintoaccounthereditaryphenomena,thequestionsofphysicsandmechanicsleadtointegro-differentialequations.Ahereditaryphenomenonoccursinasystemwhenthe phenomenondoesnotdependonlyontheactualstateofthe systembutonalltheprecedingstatesthroughwhichthesys-
Integro-differentialequationsofparabolictypeariseinthe studyofvariousproblemsinphysics,chemistry,technology, economics,etc.Oneveryimportantproblemofappliedtype isgeneratedbymathematicalmodelingofprocessesofelectromagneticfieldpenetrationintoasubstanceandisdescribedby thewell-knownMaxwell’sequations[300].Intheworks[187] and[188],complexsystemcorrespondingtononlinearpartialdifferentialequationswasreducedtointegro-differentialform.If thecoefficientofthermalheatcapacityandelectroconductivity ofthesubstancearehighlydependentontemperature,thenthe Maxwell’ssystemcanberewritteninthefollowingform(see [187]and[188]):
Insystem(1.6), ∇× W and ∇· W aretheusualvectoroperatorswithrespecttothevariables x =(x1,x2,x3). Evenonedimensionalscalarversionofthismodelisverycomplicatedand itsinvestigationhasbeenpossibleyetonlyforspecialcases.The one-dimensionalscalarcaseofthemodel(1.6),(1.7)hasthefollowingform
where a(S) ≥ a0 = const> 0isagainaknownfunctionofits argument.Investigationof(1.6),(1.7),and(1.8)typemodels
CHAPTER1.INTRODUCTION
beganintheworks[138],[187],and[188].Sincethenmany scientificpublicationsweredevotedtotheinvestigationofexistenceanduniquenessoftheirsolutionsundervarioustypesof initialandboundaryconditions.Inthisrespect,especiallysignificantaretheworks[49],[50],[141],[146],[147],[219],[220], [238],[254],[256],[302],[303],[304],[305],[306],[307],[322], [333],[334],andreferencetherein.Authorsofthisbookhave alsomadecontributioninthisdirection,forexample,see[137], [138],[139],[140],[141],[145],[146],[147],[186],[187],[188], [219],[220],[223],[238],[247],[248],[253],[254],[256],[261], andreferencetherein.
Makingcertainphysicalassumptionsinmathematicaldescriptionoftheabove-mentionedprocessofpenetrationofelectromagneticfieldintoasubstance,Laptev[306]hasconstructed anewintegro-differentialmodel,whichrepresentsageneralizationofthesystemintroducedin[187]and[188].Founded onMaxwell’ssystemthefollowingparabolicintegro-differential modelisobtained
Intheworks[303],[305],and[306]forconditionallyclosed operators,anoperatorschemeisconstructed.Thisschemeis usedfor(1.6),(1.7)typemodelstoproveexistenceanduniquenessofsolutionofinitial-boundaryvalueproblems.Intheabovementionedwork[306]Laptevpointsoutthatfortheseso-called averagedintegro-differentialmodels(1.9),itisnecessarytodevelopadifferent,specialapproach.
Insystems(1.6),(1.7),and(1.9), W =(W1,W2,W3)denotes avector,whichisconnectedbyavectorofamagneticfield H = (H1,H2,H3)andisthefunctionofthevariables(x1,x2,x3,t), whichwewillshortento(x,t).
Themultidimensionalscalaranaloguesofsystems(1.6),(1.7), and(1.9)havethefollowingforms: ∂U (x,t)
and
respectively.
Inequations(1.10)and(1.11)wehave x =(x1,...,xn)and thevectoroperator ∇U isgivenby ∇U = gradU =
(x,t)
1 ,...,
(x,t)
n =(D1U,...,DnU ) .
Somegeneralizationsofthemodels(1.6)-(1.11)aregivenin theworks[137],[139],[145],[219],[305],and[306].Onekindof thesemodelshastheforms: ∂U (x,t)
(x,t)
CHAPTER1.INTRODUCTION
and
Themodelsoftype(1.6)-(1.13)arecomplexandhavebeen intensivelystudiedbymanyauthors.Theexistenceanduniquenessofglobalsolutionsofinitial-boundaryvalueproblemsfor equationsandsystemsoftype(1.6)-(1.13)werestudiedin [49],[50],[137],[138],[139],[140],[141],[145],[186],[187],[188], [219],[223],[238],[247],[248],[253],[261],[302],[303],[304], [305],[306],[307],[322],[333],[334],andinanumberofother worksaswell.
Theexistencetheoremsthatareprovedin[137],[138],[139], [140],[141],[145],[187],[188],and[219]arebasedona-priori estimates,modifiedGalerkin’smethodandcompactnessargumentsasin[327],[328],[461],and[462]fornonlinearelliptic andparabolicequations.
Forequation(1.8)withnonhomogeneousright-handsideand a(S)=1+ S,orforequation(1.13)intheone-dimensional casewith q =2,suchtheoremforfirstinitial-boundaryvalue problemisprovedinsection3.6.
Theasymptoticbehavioras t →∞ ofthesolutionsofsuch modelshasbeentheobjectofintensiveresearchinrecentyears, see[28],[29],[31],[32],[33],[34],[35],[139],[141],[145],[146], [147],[217],[218],[219],[220],[223],[227],[228],[229],[231], [232],[233],[234],[235],[236],[237],[238],[239],[240],[241], [242],[243],[245],[246],[247],[248],[251],[252],[253],[254], [256],[257],[261],[276],[277],[278],[280],[282],[283],andreferencetherein.
Anothermodelconsideredinthisbookandstudiedbyone oftheauthorsofthismonograph[376]is
andalsoMSandPhDstudentsoftheappropriatespecializations.
1.1Commentsandbibliographical notes
Mathematicalmodelsofmanynaturalphenomenaandprocesses canbedescribedbytheinitial-boundaryvalueproblemsposed fornonstationarypartialdifferentialandintegro-differentialequationsandsystemsofsuchequations.Investigationandnumericalsolutionoftheseproblemsaretheactualsphereofmathematicalphysicsandnumericalanalysis.Onesuchpartialintegrodifferentialmodeldescribestheprocessofelectromagneticfield penetrationintoasubstance.Inthequasi-stationaryapproximation,thecorrespondingsystemofMaxwell’spartialdifferentialequationscanberewritteninintegro-differentialform(1.6), (1.7)(see[187]and[188]).
Mathematicalmodelsdescribingelectromagneticprocesses andmanyrelativephenomenaaregiveninmanyscientificpapersandbooks,see,forexample,[92],[136],[300],[359],[360], [399],[419],[473],andreferencestherein.
ItiswellknownthatelectromagneticfielddiffusionprocessesandmanyotherimportantpracticalprocessesaresimulatedbyMaxwell’ssystemsofpartialdifferentialequationsand Maxwell’s-typesystemsaswell(see,forexample,[195],[197], [290],[297],[298],[300],[360],[426],[485],[486],[487],[489], [491],andreferencestherein).
Manyscientificworksaredevotedtoinvestigationofvarious problemsforMaxwell’sandMaxwell’s-typesystems,see[4],[5], [56],[60],[101],[106],[120],[121],[124],[131],[139],[144],[145], [152],[158],[194],[195],[197],[208],[224],[225],[226],[247], [253],[275],[276],[290],[362],[365],[367],[397],[409],[427],
[452],[453],[454],[470],[475],[476],[477],[485],[486],[487], [489],[491],andreferencestherein.
Aswehavealreadypointedout,byusingMaxwell’ssystem [300]formathematicalsimulationoftheprocessofelectromagneticfieldpenetratingintoasubstance,newclassofintegrodifferentialmodels(1.6),(1.7),(1.8),and(1.10)arises(see[187] and[188]).
Integro-differentialequationsariseinmanyotherpractical processesaswell,see,forexample,[11],[21],[22],[36],[37], [55],[59],[74],[84],[119],[127],[128],[164],[185],[187],[188], [295],[298],[306],[310],[311],[312],[355],[356],[357],[363], [373],[380],[384],[405],[425],[459],[463],[465],[466],[467], [468],[469],[471],[484],andinanumberofotherworksaswell.
Themotivationforstudyingintegro-differentialproblems comesfromthemanyphysicalmodelsinsuchfieldsaselectromagneticwavepropagation,heattransfer,nuclearreactor dynamics,andthermoelasticity.Besidestheintegro-differential equationsariseinmanyspheresofhumanactivityaswell.For example,thesecondorderfullynonlinearintegro-differential equationsarederivedfromthepricingproblemoffinancialderivativesandoptimalportfolioselectionprobleminamarket[59]. In[84]nonlinearintegro-differentialequationsthatarisefrom stochasticcontrolproblemswithpurelyjumpLevyprocesses areconsidered.
Manyproblemsofmodernscienceandengineeringcanbe describedbypartialintegro-differentialequations.Sincequite alotoftheseproblemsaretime-dependent,mostofthemare evolutionequationsandespeciallynonlinearevolutionparabolic equations,see[93],[177],[179],[180],[191],[216],[310],[311], [312],[322],[332],[345],[346],[358],[451],andreferencestherein).
Manyscientificworksaredevotedtoinvestigationandnumericalsolutionofparabolicintegro-differentialmodels,see[6], [18],[45],[53],[62],[63],[69],[74],[83],[86],[87],[93],[98],[103], 1.1.COMMNETSANDBIBLIOGRAPHICALNOTES
[108],[115],[118],[128],[137],[139],[145],[155],[156],[163], [175],[177],[181],[182],[191],[198],[247],[253],[263],[265], [266],[267],[276],[279],[281],[306],[308],[310],[311],[312], [313],[319],[320],[322],[323],[327],[353],[358],[370],[376], [378],[389],[393],[427],[430],[432],[433],[447],[448],[449], [450],[451],[456],[479],[483],[488],[492],[497],andreferences therein.
Studyofthemodelsoftype(1.6),(1.7),and(1.8)hasbegun intheworks[138],[187]and[188].Intheseworks,inparticular,thetheoremsofexistenceofsolutionoftheinitial-boundary valueproblem(withfirst(Dirichlet)boundaryconditions)for scalarequationwithone-dimensionalspacevariableareproved. Investigationsofhigherspacedimensionsformodel(1.10)carriedoutinitiallyin[137]and[140].
In[306]somegeneralizationofthesystemoftype(1.6),(1.7) wasproposed.Inparticular,assumingthatthetemperature oftheconsideredbodydependsonthetimevariable,butindependentofthespacecoordinates,thenthesameprocessof penetrationofamagneticfieldintothematerialissimulated bytheaveraged(astheauthorof[306]hasnamedit)integrodifferentialmodels(1.9)and(1.11).
Studyofthemodelsoftype(1.9)and(1.11)hasstartedin theworks[217]and[219].
Onemustnotethatsomeworksweredevotedtothestudy ofmodelingofphysicalprocessofelectromagneticfieldpenetrationinthecaseofcylindricalconductors.Inthiscase,the above-mentionedintegro-differentialmodel(1.6),(1.7),written incylindricalcoordinates,wasgivenin[148].Thework[333] isdevotedtotheinvestigationofperiodicproblemforonedimensional(1.8)typemodelincylindricalcoordinates.
Interestintheabove-mentionedintegro-differential(1.6)(1.11)modelsisincreasing.Somegeneralizationsof(1.10)and (1.11)models,whichhavetheforms(1.12)and(1.13)corre-
1.1.COMMNETSANDBIBLIOGRAPHICALNOTES
spondingly,aregivenandstudiedin[219],[305],andinanumberofotherworksaswell.Equation(1.12)isinvestigated,for example,in[145],[219],[305],and[306].Equation(1.13)was investigatedin[145]and[219].Inthescientificliteraturesome moregeneralmodelshavealsoappeared,see[137],[139],[145], [219],[305],[306],and[322].
Manydifferentkindsofinitial-boundaryvalueproblemswith avarietyofboundaryandinitialconditionsareconsideredfor theabove-mentionedintegro-differentialequations.Intheworks [246],[280],[281]investigationandnumericalapproximationof problemswithmixedboundaryconditions,for(1.10)and(1.11) typeone-dimensionalscalarmodels,arestudied.
Letusalsonotethatfirstkindinitial-boundaryvalueproblemswithnonhomogeneousboundaryconditionononesideof lateralboundaryarealsoconsideredandstudiedinmanyworks. Thistypeoftheproblemstatementisdictatedbymathematical simulationofthephysicalprocesses,see,forexample,[148]and problem(2.64),(2.65)givenin”Commentsandbibliographical notes”sectioninChapter2.
Thetheoremsprovedforinvestigatingtheasymptoticbehaviorastimetendstoinfinityinsomecasesshowthedifferencebetweenstabilizationcharacterofsolutionswithhomogeneousand nonhomogeneousboundaryconditionsofthefirstkindinitialboundaryvalueproblems.Moreprecisely,inhomogeneouscase stabilizationhasanexponentialcharacter,whereasinnonhomogeneouscaseithaspower-likeform.
Theworks[49],[50]arealsoworthmentioning,whereinvestigationofinverseproblemsformultidimensionalmodelsof (1.10)typeiscarriedout.
Anotherintegro-differentialmodelstudiedinthismonograph is(1.14).Thismodeldescribesheatflowinmaterialwithmemory[196],[345].Italsoarisesinthetheoryofviscoelasticity [109],[344],and[346].
Asarulewecannotfindexactsolutionsoftheconsidered nonlineardifferentialandintegro-differentialmodels.Therefore, particularattentionshouldbepaidtoconstructionofnumerical solutionsandtotheirimportanceforintegro-differentialmodels. Thefirststepsinthisdirection,forthemodelsstudiedinthis monograph,aremadeintheworks[139],[220],[274],[376],and [378].Nowtheresearchinthisdirectionhasintensified.
Letusnotethatthemodelsbeingconsideredinthismonographhavearisenfrompracticaltasks.Buttheycanbeconsideredasmodels,generalizingknownnonlinearparabolicequations,whicharestudiedinmanyknownscientificpapers,books, andmonographs,see[76],[133],[134],[169],[199],[298],[327], [332],[381],[385],[461],andreferencestherein.
Manyscientificresearchesaredevotedtonumericalsolution ofpartialdifferentialandnonlinearparabolicequationsaswell, see[23],[43],[104],[167],[171],[183],[193],[210],[213],[225], [226],[301],[327],[400],[404],[407],[411],[415],[435],[439], [440],[447],andthereferenceslistedinthesepapersandbooks.
AswehavealreadymentionedthemainpartofintegrodifferentialstructuresconsideredherehasarisenfromMaxwell’s systemsofpartialdifferentialequations.TherearemanyscientificpapersandbooksonthenumericalsolutionofMaxwell’s systemsandMaxwell’s-typesystemsaswell,see[4],[5],[15], [26],[27],[54],[68],[139],[142],[145],[153],[212],[224],[247], [253],[260],[276],[314],[315],[316],[317],[336],[341],[369], [434],[442],[472],[480],[493],[498],andreferencestherein. Theresultsoftheseresearchesveryoftenareusedinconstructionandinvestigationofthenumericalalgorithmsforthecorrespondingintegro-differentialmodels.
Thedetaileddescriptionofinvestigationandnumericalsolutionoftheabove-mentionedmodelsisgiveninChapters2-4. Morecompletereferencesandcommentsaregiveninasection entitled”Commentsandbibliographicalnotes”ineachchapter.