Time-dependent Basis Func1on (tBF) approach to scaering
Transcript of Time-dependent Basis Func1on (tBF) approach to scaering
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Time-dependent Basis Func1on (tBF) approach to sca7ering
JamesP.Varywithcollaborators:
WeijieDu(杜伟杰),PengYin(尹鹏),YangLi(李阳),GuangyaoChen(陈光耀),WeiZuo(左维),XingboZhao(赵行波)andPieterMaris
arXiv:1804.01156;Phys.Rev.C(inpress)
DepartmentofPhysics&AstronomyIowaStateUniversity
Ins9tuteofModernPhysics,ChineseAcademyofSciences
MSU,June15,2018
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Mo1va1ons
ChallengesinpredicSngnuclearstructureandreacSons,e.g.,
• ExoScnuclei,FRIB• Astrophysics,radiaSvecapture• Fusionenergy,ITERandNIF
ThesepropeldevelopmentoftheorieswithpredicSvepower:
• Fundamental,unifiedabini&onucleartheoryfornuclearstructureandreacSons
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Background
ExisSngmethods,e.g.,• No-coreShellModelwithConSnuum• No-coreShellModel/ResonaSngGroupMethod• GamowShellModel• HarmonicOscillatorRepresentaSonofScaberingEquaSons• Green’sFuncSonApproaches• NuclearLaeceEffecSveFieldTheory• Manyothers
However,thesesuccessfulmethodsmaybechallengedtoretainfullquantalcoherenceofallrelevantnuclearprocesses
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We introduce the 1me-dependent Basis Func1on (tBF) Method
! Abini&oapproach! Non-perturbaSve! Retainsfullquantalinterference! Enablessnapshotsofdynamics! SupercompuSngdirectlyapplicable
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Idea of tBF Method 1.Abini&ostructurecalculaSon 2.Scaberingproblem
• Scaberingstate=Sme-dependentsuperposiSonofeigen-bases• Operatorsbecomematricesineigen-basisrepresentaSon
1. Solveforthe“target”system’seigen-basisviaabini&ocalculaSon2. Definethescaberingstatewithinthiseigen-basisandevaluateH(t)inthisbasis3. SolvetheequaSonofmoSoninthiseigen-basis
+V(t)
H0 βi = Ei βi
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• Hamiltonianofthedeuteron
with
• IntrinsickineScenergy
• RealisScinter-nucleoninteracSon
Ab ini&o Structure Calcula1on of Deuteron
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3DHO Basis for NN Nuclear Structure Calcula1on • NuclearinteracSonconservestotalangularmomentum
• ExcitaSonquantaforbasisspacetruncaSon:
• 3DHObasiswavefuncSonincoordinatespace
• Why3DHObasis?• Respectsthesymmetriesofthenuclearsystem
• e.g.,rotaSonalandtranslaSonalsymmetries• ThecenterofmassmoSoncanbeeasilyremoved
βi → {SJMJTz}i = anl
i
n,l∑ nlSJMJTz
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JISP16 interac1on adopted for the ini1al applica1on
• ConstructedbyJ-matrixinversescaberingtheory• ReproducesNNscaberingdata
• “16”meanstheinteracSonisfibedtoreproducesomeoftheproperSesfor16O
• ReproducesselectedproperSesoflightnuclei• e.g.,2H,3H,4He
• Includestwo-nucleon(NN)interacSononly
• Non-localinteracSon
• TheinteracSonin3DHOrepresentaSon(matrixelements)
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Simplify the “con1nuum” => add a HO confining interac1on Hamiltonian for Quasi-deuteron in 3DHO Representa1on
+ +
=
Trel VNN Utrap
FullHamiltonian
DiagonalizaSon
Eigen-energiesonthediagonal
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Results: Ground State Energies for Natural and Quasi-Deuteron
! Nmax=60;! Basisstrength=5MeV;
! Asthebasisspaceincreasesindimension,theoreScalgsenergyofdeuteronconvergestotheexperimentalvalue.
=max(2n+l)
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Time-Dependent Schrödinger Equa1on
• Time-dependentfullHamiltonian
• EquaSonofmoSon• Schrödinger picture
• InteracSonpicture
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Solve Time-dependent Schrödinger Equa1on
• EquaSonofmoSonininteracSonpicture
• FormalsoluSon
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Transi1on Amplitudes of States WiththebasisrepresentaSon
thestatevectorforthesystemunderscaberingbecomes
wherethetransiSonamplitudeis
H0 βi = Ei βi
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Numerical Method 1: Euler Method
• DirectevaluaSonoftheSme-evoluSonoperator
with
• Fast in calculation • Accurate up to (𝛿𝑡)↑2 • Hence poor numerical stability
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Numerical Method 2: Mul1-Step Differencing
• Multi-step differencing (MSD2) for the evolution:
T.Iitaka,Phys.Rev.E494684(1994)WeijieDuetal.,inpreparaSon
• MSD is an explicit method – it does not evaluate matrix inversions • MSD2 is accurate up to (δt)3 • MSD4 is accurate up to (δt)4, however less efficient • We employ MSD2 for better numerical stability and efficiency
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For Comparison: First-Order Perturba1on Theory
Purposesforthiscomparison• tBFmethodisnon-perturbaSve• tBFmethodevaluatesallthehigher-ordereffects
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First Model Problem: Coulomb Excita1on of Deuterium System by Peripheral Sca7ering
with Heavy Ion
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Setup: Coulomb Excita1on of Deuterium System
H0:targetHamiltonianϕ:Coulombfieldfromheavyionρ:ChargedensitydistribuSonofdeuteron
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Treatment of 1me-varying Coulomb field
! InthebasisrepresentaSon,theoperatorfortheCoulombinteracSonbecomesamatrix
! WetakeamulSpoledecomposiSonfortheCoulombfieldandkeeponlytheE1mulSpolecomponent
K.Alderetal.,Rev.Mod.Phys.28,432(1956)
E1transiSonbetweenbases
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E1 Matrix Element in Basis Representa1on E1transiSonmatrixelementinthebasisrepresentaSonisevaluatedby
• BasisfuncSonsfromtheabini&ostructurecalculaSon
• AndtheanalyScformoftheE1operatorin3DHOrepresentaSon βi → {SJMJTz}i = anl
i
n,l∑ nlSJMJTz
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Basis Set for Deuteron in Current Calcula1on ! 7basisstatesaresolvedviaabini&omethod
NTSEproceeding,WeijieDuetal.2017
! IniSalstate! PolarizaSonanSparalleltoz-axis! E1radiaSvetransiSons
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Transi1on Probabili1es
Weakfieldlimit:b=5fmZ=10v/c=0.1
Validity:WhentheCoulombfieldisweak,tBFmethodmatcheswithfirstorderperturbaSontheory(1PT)
(3S1,3D1),M=-1
tBF
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Higher-Order Effects
Strongfieldlimitb=5fmZ=92v/c=0.1
ForbiddentransiSons
! Revealedbynon-perturbaSvetBF
tBFPert
(3S1,3D1),M=-1
(3S1,3D1),M=+1
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Excita1on of Intrinsic Energy
! ObservablesasfuncSonsofSme
! QuantumfluctuaSonaretakencareattheamplitudelevel
b=5fmZ=92
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Excita1on of Orbital Angular Momentum
Observable’sdependenceon
! Sme! incidentspeed
b=5fmZ=92
v/cMethod
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Expansion of r.m.s. Point Charge Radius
r.m.s.radiusofthedeuteriumsystemduringthescaberingasafuncSonof
! Sme! incidentspeed
b=5fmZ=92
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Dynamics: Charge Density Distribu1on of Ini1al np system
! TheIniSalpolarizaSonisanS-paralleltothez-axisx[fm]
y[fm
]
z[fm
]
x[fm]
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Change in Charge Density Distribu1on of Sca7ered np System (x-z plane) at T= 0.23 MeV-1
! ThedifferenceinchargedensitydistribuSonsbetweentheevolvedandtheiniSalnpsystem
! NotethepolarizaSonofthechargedensitydistribuSon
x[fm]
z[fm
]
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! DensityfluctuaSon
! ExcitaSonoforbitalangularmomentum
x[fm]
y[fm
]
Change in Charge Density Distribu1on of Sca7ered np System (x-y plane) at T= 1.975 MeV-1
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Dynamics Revealed by Anima1on (x-y Plane) Howtointerpret?! ThepolarizaSonofcharge
distribuSonwhenHIapproaches
! TheexcitaSonofrotaSonal
degreeoffreedom! TheexcitaSonof
oscillaSonaldegreeoffreedom
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Recent Progress Peng Yin, et al., in prepara1on
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Implement Rutherford Trajectories
EquaSonofMoSon IniSalCondiSon
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51 States Implemen1ng Daejeon16 NN-interac1on
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Popula1on in 51 States Aier Sca7ering ! RutherfordScabering! FirstOrder
PerturbaSontheoryvs.MSD2
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Inelas1c Cross Sec1on and Average Excita1on Energy
! CrosssecSonandaverageexcitaSonenergyincreaseswithincidentvelocity! BothcrosssecSonandaverageexcitaSonenergyreachsaturaSonat
sufficientlyhighincidentvelocity
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• Time-dependent Basis Function (tBF) is motivated by progress both in experimental nuclear physics and in supercomputing techniques
• tBF is a non-perturbative ab initio method for time-dependent problems • tBF is particularly suitable for strong, time-dependent, field problems • tBF evaluates at the amplitude level - full quantal coherence is retained • tBF is aimed to provide insights into fundamental structure/reaction
issues in a detailed and differentiated manner for nuclear reactions
Summary
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• Observables: differential cross sections with polarization, inclusive non-linear inelastic response, contributions of 2-body currents, higher-order electromagnetic couplings, . . .
• Perform calculation in larger basis space and study convergence with respect to density of states in the continuum
• Study the sensitivity with respect to the nuclear Hamiltonian • Include strong force in the background field • More realistic center of mass motion
• Trajectory from QMD • Direct computation of relative motion of the two nuclei (e.g. RGM)
• Extend investigations on constraints for the symmetry energy from scattering
Announcement
Outlook
New faculty position in Nuclear Theory at Iowa State University with support from the DOE Fundamental Interactions Topical Collaboration
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https://indico.ibs.re.kr/event/216/
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Thank you!