shell model a unified view of nuclear structure · 2015-09-02 · the nuclear shell model heyde k....
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![Page 1: Shell Model A Unified View of Nuclear Structure · 2015-09-02 · The nuclear shell model Heyde K. Springer-Verlag 1994 The nuclear shell model A. Poves and F. Nowacki Lecture Notes](https://reader034.vdocument.in/reader034/viewer/2022042303/5ecec9e269da9b61c35fd5da/html5/thumbnails/1.jpg)
Shell Model
A Unified View of Nuclear Structure
Frederic Nowacki1
18th STFC UK Postgraduate Summer School
Lancaster, August 24th-September 5th-2015
1Strasbourg-Madrid Shell-Model collaboration
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Bibliography
Basic ideas and concepts in nuclear physicsan introductory approachHeyde K.IOP Publishing 1994
Shell model applications in nuclear spectroscopyBrussaard P.J., Glaudemans P.W.M.North-Holland 1977
The nuclear shell modelHeyde K.Springer-Verlag 1994
The nuclear shell modelA. Poves and F. NowackiLecture Notes in Physics 581 (2001) 70ff
The shell model as a unified view of nuclear structureE. Caurier, G. Martinez-Pinedo, F. Nowacki, A. Poves, A. P. ZukerRev. Mod. Phys. 77, 427 (2005)
Shell structure evolution and effective in-medium NN interactionN. SmirnovaEcole Joliot-Curie 2009
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Outline
Lecture 1: Introduction, basic notions, shell model codes
and calculations
Lecture 2: Lanczos structure functions, Effective
Interactions for SM calculations
Lecture 3: Shell model applications to nuclear
spectroscopy
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Lecture 1
Introduction and basic notions
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Basic Notions
First insights on nuclear structure:
liquid-drop model (Bethe and Bacher, 1936; von
Weizsacker, 1935): drops of charged, incompressible,
liquid nuclear matter
compound nucleus model of nuclear reactions (Bohr,
1936): incident neutron’s energy dissipate totally via
collisions
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Basic Notions
Experimental evidences for shell structure in nuclei:
magic numbers
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α lines systematics
15
20
25
30
35
40
45
0 20 40 60 80 100 120 140 160
BE
(Z+
2,N
+2)
-BE
(Z,N
)
N
α lines
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α lines systematics
15
20
25
30
35
40
45
0 20 40 60 80 100 120 140 160
BE
(Z+
2,N
+2)
-BE
(Z,N
)
N
α lines
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α lines systematics
15
20
25
30
35
40
45
0 20 40 60 80 100 120 140 160
BE
(Z+
2,N
+2)
-BE
(Z,N
)
N
α lines
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Basic Notions
Experimental evidences for shell structure in nuclei:
magic numbers
single particle states
magnetic moments
BUT strong successes of liquid-drop and compound-nucleus
models as evidence against collisionless single-particle motion
assumed in the shell model
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Basic Notions
Soon it was realized that for fermions:
compound-nucleus reactions occur at relatively high
excitations energies where many collisions are not Pauli
blocked
at low energy, suppression of collisions by Pauli exclusion
Single Particle Motion can persist
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Independant Particle Model
Interaction of a nucleon with ALL the other particles is
approximated by a central potential:
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Basic Notions
Empirical construction by M. Goeppert Mayer and H. Jensen
of a harmonic oscillator mean field plus a spin-orbit term to
reproduce the magic numbers:
U(r) =1
2mω2r2 + D~l2 - C~l .~s
Such a term does not commute with Lz and sz but DOES
commute with~j2= (~l + ~s)2 and jz = lz + sz ,~j2, ~s2:
-~l .~s = -1
2(~j2 −~l2 − ~s2) = -
1
2(j(j + 1)− l(l + 1)−
3
4)
=l + 1 for j=l-1
2
−l for j=l+12
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Basic Notions
With spin-orbit coupling, the solutions are:
φnljm(r , σ) = Rnl(r) [Yl(θ, φ) χ 12(σ)]mj
where the orbital and spin wave functions coupling is
φnljm(r , σ) = Rnl(r)∑
ml ,ms
〈lml1
2ms|jm〉Y ml
l (θ, φ)χms12
(σ)
the corresponding energies being
ǫnljm = ~ω
[
N +3
2+ Dl(l + 1) + C
l + 1 j = l − 1
2
−l j = l + 12
]
with N = 2(n − 1) + l
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Basic Notions
0
1s (2) 2
1p(8)(6)
8
1g7/2
1f2p
1d2s 2
3s
(38)(40)(50)
1g
1h
1h11/2
2d
3p
2d3/2
2p1/2
2s
1p3/21p1/2
1s
2p3/2
1h9/2
3s1/2
2d5/2
2f7/22f5/2 3p3/23p1/2
(64)
(82)
2f
1g9/2
1f5/2
1f7/2
1d3/2
1d5/2
(8)
(6)(4)(2)
(10)
(8)(6)
(4)(2)
(12)
(2)(6)(4)
(12)
(8)
(6)(2)(4)
(2)
(2)
(4)
(126)
(20)(14)
1i13/2 (14)
N=5
N=4
N=3
N=2
N=1
N=0
(28) 28
82
126
50
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Hartree Fock
Link between nucleon-nucleon effective interaction and
mean-field : Hartree-Fock approximation
H =
A∑
i=1
ti +1
2
A∑
i 6= j
j = 1
vij
two body term replaced by a one body potential (mean field) U
H(0) =
A∑
i=1
ti + Ui
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Single Particle in potential:
h(0)φa(r) = T (k) + U(r)φa(r) = ǫaφa(r)
System of A independant particles:
H(0) =A∑
k=1
T (k) + U(r(k))
The eigenfunctions of H(0) are
Φa1a2...aA(1,2, ...,A) =
A∏
k=1
φak(r(k))
with the eigenvalues E (0) =A∑
k=1
ǫak.
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System of identical particles
For a system of identical particles, one needs to take into
account that the particles are indistinguishable
total wave function is (anti)symmetric
with exchange of two particles
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System of identical particles
in quantum mechanics, particle exchange degeneracy:
(1)
(2)
(1)
(2)
D
(1)
(2)
D
(1)
(2)
there exist two possible distinct final states (orthogonal) but
associated to a single physical state (no possible measurement
to distinguish them)
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System of identical particles
symmetrisation postulate
For a system of identical particles, only some (N-body)
eigenfunctions describe physical states: they are antisymmetric
(with respect to permutations of particles) for fermions and
symmetric for bosons
If |u〉 is a physical ket, Pα|u〉 is also a physical ket
For fermions, the physical kets are those obtained by
antisymmetrization :
A|u〉 avec A=√
1N!
∑
αǫαPα
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System of identical particles
example with two particles:
|u〉 = φa(1)φb(2) and Eu = φa(1)φb(2), φa(2)φb(1)
A|u〉 =√
12(φa(1)φb(2) − φa(2)φb(1))
Pauli principle: if φa = φb, A|u〉 = 0
antisymmetry in all particle coordinates
Generalized Pauli principle (in nuclear physics): the wave
function reverses its sign upon odd permutation of all
coordinates space, spin and isospin
For two particles in the same orbit:symmetric in space-spin and antisymmetric in isospin
antisymmetric in space-spin and symmetric in isospin
J + T = odd
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System of identical particles
example with three particles:
|u〉 = φa(1)φb(2)φc(3) and
Eu = φa(1)φb(2)φc(3), φa(2)φb(3)φc(1), φa(2)φb(1)φc(3),φa(3)φb(1)φc(2), φa(3)φb(2)φc(1), φa(1)φb(3)φc(2)
A|u〉 =√
16 ( φa(1)φb(2)φc(3) + φa(2)φb(3)φc(1) + φa(3)φb(1)φc(2)
−φa(2)φb(1)φc(3)− φa(3)φb(2)φc(1)− φa(1)φb(3)φc(2))
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System of identical particles
two particles case:
Φab(1, 2) =
√
1
2φa(1)φb(2) − φa(2)φb(1) =
√
1
2
∣∣∣∣
φa(1) φa(2)φb(1) φb(2)
∣∣∣∣
i. e. a Slater Determinant
three particles case:
Φabc(1,2,3) =
√
1
6
∣∣∣∣∣∣
φa(1) φa(2) φa(3)φb(1) φb(2) φb(3)φc(1) φc(2) φc(3)
∣∣∣∣∣∣
developped with the Sarrus rule
Φabc(1, 2, 3) =√
16
φa(1)φb(2)φc(3) + φa(3)φb(1)φc(2) + φa(2)φb(3)φc(1)
−φa(3)φb(2)φc(1) − φa(2)φb(1)φc(3)− φa(1)φb(3)φc(2)
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System of identical particles
A particles case:
Φaα1a
α2...aαA(1, 2, ...,A) =
√
1
A!
∣∣∣∣∣∣∣
φaα1
(r(1)) φaα1
(r(2)) ... φaα1
(r(A))φa
α2(r(1)) φa
α2(r(2)) ... φa
α2(r(A))
: : : :φa
αA(r(1)) φa
αA(r(2)) ... φa
αA(r(A))
∣∣∣∣∣∣∣
The global phase is determined by the order of the indices: α1,α2, ...αA withαi ≡ ni li jimi
Occupation number formalism to simplify such expressions:
Φaα1a
α2...aαA(1, 2, ..., A) = a
†aα1...a
†aαA|0〉
only occupation numbers of the single particle orbits are necessary (no
labelling of the particles)
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Second quantization
Creation and annihilation operators:
a†i |0〉 = |i〉 ai |i〉 = |0〉 vacuum |0〉 such ai |0〉 = 0
For fermions, antisymmetry ensured by anti-commutation rules:
a†i ,a
†j = ai ,aj= 0
a†i ,aj=δi ,j
One body operators:
O(1) =A∑
i=1
O(r(i)),
whose matrix elements are 〈i |O|j〉 =∫
φ∗i (r)Oφj (r)dr
will write in second quantization as
O =∑
i ,j
〈i |o|j〉a†i aj
ex: n =∑
i
ni =∑
i
a†i ai
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Second quantization
Two body operators:
O(2) =A∑
1=j<k
O(r(i), r(j)),
whose matrix elements are 〈ij |O|kl〉 =
∫
φ∗i (r(1))φ
∗j (r(2))(1 − P12)Oφk (r(1))φl (r(2))dr(1)dr(2)
will write in second quantization as
O = 14
∑
i ,j ,k ,l
〈ij |O|kl〉a†ia†jalak
ex: H, ββ operator
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Hartree Fock
H(0) eigenfunctions are:
Ψa1a2...aA(1,2, ...,A) = det(
A∏
k=1
φak(r(k)))
=A∏
k=1
a†k |0〉
φak(r(k)) obtained by minimisation of the total energy
E =〈Ψ|H|Ψ〉
〈Ψ|Ψ〉
masses, radii, charge density distribution ...
magic numbers, single particle energies, individual wave
functions ...
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Correlations in nuclei
for the description of nuclei, mean field is only the starting
point
the two body residual interaction (correlations) is
reponsable for the detailled structure of nuclei
in particular, correlations can induce coherent phenomena
i. e. collectivity
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Correlations in nuclei
V. R. Pandharipande, I. Sick and P. K. A. deWitt
Huberts, Rev. mod. Phys. 69 (1997) 981
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Correlations in nuclei
Example in 160:
νΠ
h ω
h ω
h ω
h ω
1d3/22s1/2
1d5/2
1s1/2
1p3/2
1p1/2
12 MeV
0
0 ...4
0 ...
+
+
− −
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Correlations in nuclei
Example in 160:
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Correlations in nuclei
Example in 160:
νΠ
1p3/2
1p1/2
1d5/22s1/2
1d3/2
νΠ
1p3/2
1p1/2
1d5/22s1/2
1d3/2
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Correlations in nuclei
In order to incorporate the correlations, one has to go beyond
mean-field
Spherical mean-field
breaking symmetries
of the system
mixing
different mean-field configurations
• Hartree-Fock Bogoliubov
• Nilsson
• Deformed Hartree-Fock
• Tamm-Dancoff
• RPA
• Interacting shell-model
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Basic notions
The succes of the independent particle model strongly suggest
that the very singular free NN interaction can be regularized in
the nuclear medium.
For a given number of protons and neutrons the mean field
orbitals can be grouped in three blocks.
Inert core: orbits that are always full.
Valence space: orbits that contain the physical degrees of
freedom relevants to a given property. The distribution of
the valence particles among these orbitals is governed by
the interaction.
External space: all the remaining orbits that are always
empty.
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Basic notions
Starting with a regularized interaction, the exact solution of the
secular problem, in the (infinite) Hilbert space built on the mean
field orbits, is approximated in the large scale shell model
calculations by the solution of the Schrodinger equation in the
valence space, using an effective interaction such that:
HΨ = EΨ −→ Heff .Ψeff . = EΨeff .
In general, effective operators have to be introduced to account
for the restrictions of the Hilbert space
〈Ψ|O|Ψ〉 = 〈Ψeff .|Oeff .|Ψeff .〉
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Basic notions
The microscopic description of the nucleus we adopt is that of a
non-(explicitely)-relativistic quantum many body system.
Therefore we assume:
nucleon velocities small enough to justify the use of
non-relativistic kinematics
hidden meson and quark-gluon degrees of freedom
two body interactions
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Shell model
A shell model calculation needs the following ingredients:
A valence space
An effective interaction
A code to build and diagonalize the secular matrix
Obviously the last two points limit the choice of the valence
space
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Valence space
The choice of the valence space:
In light nuclei the harmonic oscillator closures determine
the natural valence spaces.
4He −→ 16O −→ 40Ca −→ 80Zrp shell sd shell pf shell ↑Cohen/ Brown/ DeformedKurath Wildenthal
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Valence space
0~ω
1~ω
2~ω
3~ω
4~ω
5~ω
...
1s
1p
1d2s
1f
2p
1g
2d
3s
1h
2f
3p
1s1/2 (2) 2
1p3/2 (6)1p1/2 (8) 8
1d5/2 (14)2s1/2 (16)
1d3/2 (20) 20
1f7/2 (28) 28
2p3/21f5/2 (38)
2p1/2 (40)1g9/2 (50) 50
1g7/22d5/2 (64)
2d3/23s1/2
1h11/2 (82) 82
1h9/22f7/22f5/2
3p3/23p1/2
1i13/2 (126) 126
Valence space
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Valence space
0~ω
1~ω
2~ω
3~ω
4~ω
5~ω
...
1s
1p
1d2s
1f
2p
1g
2d
3s
1h
2f
3p
1s1/2 (2) 2
1p3/2 (6)1p1/2 (8) 8
1d5/2 (14)2s1/2 (16)
1d3/2 (20) 20
1f7/2 (28) 28
2p3/21f5/2 (38)
2p1/2 (40)1g9/2 (50) 50
1g7/22d5/2 (64)
2d3/23s1/2
1h11/2 (82) 82
1h9/22f7/22f5/2
3p3/23p1/2
1i13/2 (126) 126
Valence space
4 ≤ A ≤ 16 p shell
Cohen-Kurath interaction
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Valence space
0~ω
1~ω
2~ω
3~ω
4~ω
5~ω
...
1s
1p
1d2s
1f
2p
1g
2d
3s
1h
2f
3p
1s1/2 (2) 2
1p3/2 (6)1p1/2 (8) 8
1d5/2 (14)2s1/2 (16)
1d3/2 (20) 20
1f7/2 (28) 28
2p3/21f5/2 (38)
2p1/2 (40)1g9/2 (50) 50
1g7/22d5/2 (64)
2d3/23s1/2
1h11/2 (82) 82
1h9/22f7/22f5/2
3p3/23p1/2
1i13/2 (126) 126
Valence space
4 ≤ A ≤ 16 p shell
Cohen-Kurath interaction
16 ≤ A ≤ 40 sd shell
USD interaction
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Valence space
0~ω
1~ω
2~ω
3~ω
4~ω
5~ω
...
1s
1p
1d2s
1f
2p
1g
2d
3s
1h
2f
3p
1s1/2 (2) 2
1p3/2 (6)1p1/2 (8) 8
1d5/2 (14)2s1/2 (16)
1d3/2 (20) 20
1f7/2 (28) 28
2p3/21f5/2 (38)
2p1/2 (40)1g9/2 (50) 50
1g7/22d5/2 (64)
2d3/23s1/2
1h11/2 (82) 82
1h9/22f7/22f5/2
3p3/23p1/2
1i13/2 (126) 126
Valence space
4 ≤ A ≤ 16 p shell
Cohen-Kurath interaction
16 ≤ A ≤ 40 sd shell
USD interaction
40 ≤ A ≤ 80 pf shell
KB3, GXPF1 interactions
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Valence space
In heavier nuclei:
−→ jj closures due to the spin-orbit term show up
N=28, 50, 82, 126
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Valence space
In heavier nuclei:
−→ jj closures due to the spin-orbit term show up
N=28, 50, 82, 126
the transition HO −→ jj : occurs between 40Ca and 100Sn
where the protagonism shifts from the 1f7/2 to the 1g9/2
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Valence space
0~ω
1~ω
2~ω
3~ω
4~ω
5~ω
...
1s
1p
1d2s
1f
2p
1g
2d
3s
1h
2f
3p
1s1/2 (2) 2
1p3/2 (6)1p1/2 (8) 8
1d5/2 (14)2s1/2 (16)
1d3/2 (20) 20
1f7/2 (28) 28
2p3/21f5/2 (38)
2p1/2 (40)1g9/2 (50) 50
1g7/22d5/2 (64)
2d3/23s1/2
1h11/2 (82) 82
1h9/22f7/22f5/2
3p3/23p1/2
1i13/2 (126) 126
Valence space
4 ≤ A ≤ 16 p shell
Cohen-Kurath interaction
16 ≤ A ≤ 40 sd shell
USD interaction
40 ≤ A ≤ 80 pf shell
KB3, GXPF1 interactions
Heavier nuclei :Spin-orbite shell closures
28, 50, 82, 126
Transition between 40Ca and 100Sn
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Valence space
0~ω
1~ω
2~ω
3~ω
4~ω
5~ω
...
1s
1p
1d2s
1f
2p
1g
2d
3s
1h
2f
3p
1s1/2 (2) 2
1p3/2 (6)1p1/2 (8) 8
1d5/2 (14)2s1/2 (16)
1d3/2 (20) 20
1f7/2 (28) 28
2p3/21f5/2 (38)
2p1/2 (40)1g9/2 (50) 50
1g7/22d5/2 (64)
2d3/23s1/2
1h11/2 (82) 82
1h9/22f7/22f5/2
3p3/23p1/2
1i13/2 (126) 126
Valence space
4 ≤ A ≤ 16 p shell
Cohen-Kurath interaction
16 ≤ A ≤ 40 sd shell
USD interaction
40 ≤ A ≤ 80 pf shell
KB3, GXPF1 interactions
Heavier nuclei :Spin-orbite shell closures
28, 50, 82, 126
Transition between 40Ca and 100Sn
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Valence space
0~ω
1~ω
2~ω
3~ω
4~ω
5~ω
...
1s
1p
1d2s
1f
2p
1g
2d
3s
1h
2f
3p
1s1/2 (2) 2
1p3/2 (6)1p1/2 (8) 8
1d5/2 (14)2s1/2 (16)
1d3/2 (20) 20
1f7/2 (28) 28
2p3/21f5/2 (38)
2p1/2 (40)1g9/2 (50) 50
1g7/22d5/2 (64)
2d3/23s1/2
1h11/2 (82) 82
1h9/22f7/22f5/2
3p3/23p1/2
1i13/2 (126) 126
Valence space
4 ≤ A ≤ 16 p shell
Cohen-Kurath interaction
16 ≤ A ≤ 40 sd shell
USD interaction
40 ≤ A ≤ 80 pf shell
KB3, GXPF1 interactions
Heavier nuclei :Spin-orbite shell closures
28, 50, 82, 126
Transition between 40Ca and 100Sn
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Valence space
A valence space can be adequate to describe some
properties and completely wrong for others
48Cr (f 72)8 (f 7
2p 3
2)8 (fp)8
Q(2+) (e.fm2) 0.0 -23.3 -23.8E(2+) (MeV ) 0.63 0.44 0.80E(4+)/E(2+) 1.94 2.52 2.26
BE2(2+ → 0+) (e2.fm4) 77 150 216
B(GT) 0.90 0.95 3.88
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Valence space
For the quadrupole properties f 72p 3
2
is a good space whereas for magnetic and Gamow-Teller
processes the presence of the spin orbit partners is
compulsory.
In the tin isotopes
the natural valence space consists in a 100Sn core and
valence orbits:
(d 52g 7
2s 1
2d 3
2h 11
2)ν
However, numerous E1 transitions have been measured
that are forbidden in this space because:
(a†11/2
.aj)λ6=1,
it is then necessary to incorporate the 1g9/2 orbit.
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Intruder states
normal states intruder states
Ca42
νΠ
2s1/21d5/2
1d3/2
1f7/2
2p1/21f5/2
2p3/2
Ca42
νΠ
1f7/22p3/2
2p1/21f5/2
1d5/22s1/2
1d3/2
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Physics Goals
Precision Spectroscopy towards larger masses
Description of the nuclear correlations in the laboratory frame
Changing Magic Numbers far from Stability: The competing
roles of spherical mean field and correlations
Double β decay, the key to the nature of the neutrinos, the
absolute scale of their masses and their hierarchy
No core shell model for light nuclei. Ab initio description of the
low-lying intruder states and of the origin of the Gamow-Teller
quenching
Nuclear Structure and Nuclear Astrophysics
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The most popular “flaws” of the standard SM
description
Not all the regions of the nuclear chart are amenable to a
SM description yet
Quadrupole effective charges are needed (But their value
is universal and rather well understood)
Spin operators are quenched by another universal factor
which relates to the regularization of the interaction (also
known as short range correlation). Indeed, BMF
approaches share this shortcoming
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Accessible Regions
Ν→
Ζ↑
*
* *
*
*
*
* *
*
*
* *
* ** **
* * *
**
*
* **
*
**
**
** ***
**
*
*** **
***
**
*
**
***
*
** ***** *
**
***
*
* **** **
*******
***** **** *
*
****
*
*** **** *
****
*****
*** ***** ** ***** *
**
***
*
*** *** *
**
***
*
**
****
*
*** *** *
***
*
***
**
***
*
***
**
****** ****** ****** ******* *
*****
*****
*
***** ***
**
****
*****
***
*****
**** *******
*
*
*****
****** *
*****
*****
**
*** *****
*
**
**
****
****
****
**
****
*
*** ******
*
**** ***
****
*
*** **** ****
********
**
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*
***** **** **
***
*** *
****
*
**** ** * * *
n 0 H 1
He 2 Li 3
Be 4 B 5 C 6
N 7 O 8
F 9 Ne 10
Na 11 Mg 12 Al 13 Si 14
P 15 S 16
Cl 17 Ar 18
K 19 Ca 20
Sc 21 Ti 22
V 23 Cr 24
Mn 25 Fe 26
Co 27 Ni 28
Cu 29 Zn 30
Ga 31 Ge 32
As 33 Se 34
Br 35 Kr 36
Rb 37 Sr 38
Y 39 Zr 40
Nb 41 Mo 42
Tc 43 Ru 44
Rh 45 Pd 46
Ag 47 Cd 48
In 49 Sn 50
Sb 51 Te 52
I 53 Xe 54
Cs 55 Ba 56
La 57 Ce 58
Pr 59 Nd 60
Pm 61 Sm 62
Eu 63 Gd 64
Tb 65 Dy 66
2 4 6
8 10
12 14 16
18 20
22 24
26
28 30 32
34
36 38
40 42
44 46 48 50
52
54
56 58
60 62 64
66
68 70
72
74 76 78 80 82
84
86 88
90 92 94 96
98
100
*** **
**
** **
*
****
* ** *** * *
*
*
*
*** *** ***** ****** *
*
*
*****
* ***** *
**
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*
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****
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***
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****** ******** **
*****
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*
***** ******* ***** ***** **
*****
*******
***
** *** **
***********
*
*** ********************
Ho 67 Er 68
Tm 69 Yb 70
Lu 71 Hf 72
Ta 73 W 74
Re 75 Os 76
Ir 77 Pt 78
Au 79 Hg 80
Tl 81 Pb 82
Bi 83 Po 84
At 85 Rn 86
Fr 87 Ra 88
Ac 89 Th 90
Pa 91 U 92
Np 93 Pu 94
Am 95 Cm 96 Bk 97
Cf 98 Es 99
Fm 100Md 101
No 102Lr 103Rf 104
Ha 105Sg 106Ns 107
Hs 108Mt 109
10 11011 111
80 82 84 86 88 90 92 94 96 98 100 102 104106
108110
112
114 116
118 120
122124
126128
130 132
134136 138
140142 144
146
148 150
152
154 156
158
160
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Shell Model Problem
CORE
Define a valence space
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Shell Model Problem
CORE
Define a valence space
Derive an effective interaction
HΨ = EΨ → HeffΨeff = EΨeff
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Shell Model Problem
CORE
Define a valence space
Derive an effective interaction
HΨ = EΨ → HeffΨeff = EΨeff
Build and diagonalize the
Hamiltonian matrix.
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Shell Model Problem
CORE
Define a valence space
Derive an effective interaction
HΨ = EΨ → HeffΨeff = EΨeff
Build and diagonalize the
Hamiltonian matrix.
In principle, all the spectroscopic properties are described
simultaneously (Rotational band AND β decay half-life).
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The interaction in second quantization
The hamiltonian can be written as:
H =A∑
k=1
T (k) +A∑
k<l
W (k , l)
and in second quantization
H =A∑
ij
〈i |T |j〉a†i aj +1
4
A∑
ijkl
〈ij |W |kl〉a†i a
†j alak
Introducing a mean fieldA∑
k
U(k), it can be written as:
H =
A∑
k=1
T (k) + U(k)
︸ ︷︷ ︸
H(0)
+ A∑
k<l
W (k , l) −A∑
k=1
U(k)
︸ ︷︷ ︸
V
The basis states are eigenvectors of the mean field and the two
body hamiltonian is diagonalized in this basis.
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m scheme
Choice of the basis:
a) m-scheme : The symmetries of the hamiltonian are not
explicit. The basis is composed of Slater determinants made
from the valence orbits a†i|0〉
|Φα〉 =∏
i=nljmτ
a†i |0〉 = a
†i1...a
†iA|0〉
The physical states come out of the diagonalization of the
Hamiltonian matrix
〈Φα|Heff .|Φα′〉
The drawback is that the size of the matrices is maximal:
D ∼(
dπ
p
).(
dν
n
)
The advantage is that the Hamiltonian matrix is sparse and ...
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Computing the matrix elements
The matrix elements are very easy to compute. We represent a
Slater determinant by a machine word, where each state is a bit
(0 empty 1 occupied)
Example : 12C in the p-shell
1/2 3/2 1/2- 1/2 -1/2 -3/2 1/2 3/2 1/2- 1/2 -1/2 -3/2
0 0 1 1 1 1 1 1 1 10 0
12 11 10 9 8 7 6 5 4 3 2 1
Mn
i=
Mp
0p1/2 0p3/2 0p1/2 0p3/2
≡ a†10a
†9a
†8a
†7 b
†4b
†3b
†2b
†1 |0〉
In this example the Slater determinant is a 12 bits word.
The action of the Hamiltonian on such an object is very simple:
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Computing the matrix elements
Let |I〉 be a basis function; the action of a two body term |I〉,
a†i a
†j akal |I〉 carries
an amplitude ±Vijkl ,
if k and l are occupied and i and j are empty or equal to k , l
or zero amplitude otherwise
If the result is not zero it produces another state |J〉
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Computing the matrix elements
Back to 12C
a†12b
†6a9b1 0 0 1 1 1 1 0 0 1 1 1 1
= 1 0 1 0 1 1 1 0 1 1 1 0
= a†12a
†10a
†8a
†7 b
†6b
†4b
†3b
†2 |0〉
In practice,
all the machine words corresponding to all the basis states
are generated |I〉 I=1, ...N
and a loop is made on all the two body operators a†ia†jakal
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Computing matrix elements
The resulting states |J〉 are clasified (identified) in the list of
Slater determinants and the matrix element HIJ is
〈J|H|I〉 = ±Vijkl
This is the Glasgow method (Whitehead, (1977))
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Computing matrix elements
The search of |J〉 can be done by the bisection method:
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Computing matrix elements
The search of |J〉 can be done by the bisection method:
1
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Computing matrix elements
The search of |J〉 can be done by the bisection method:
1
2
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Computing matrix elements
The search of |J〉 can be done by the bisection method:
1
2
3
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Computing matrix elements
The search of |J〉 can be done by the bisection method:
1
2
3
nop ∼ ln(N)
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Phases
Example
|I〉 ≡ a†6a
†5a
†4a
†2 |0〉8 ≡ 1 1 1 0 1 0
Action of :
a†3a
†1a4a2 |I〉 ≡ 1 1 0 1 0 1
Phase:
a†3a
†1a4a2 (a†
6a†5a
†4a
†2) |0〉
= −a†3a
†1a4 a
†6a
†5a
†4 |0〉
= −a†3a
†1 a
†6a
†5 |0〉
= −a†6a
†5 a
†3a
†1 |0〉
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Coupled scheme
Choice of the basis:
b) coupled basis (J or JT ):
The wave function is written as successive coupling of one shell
wave functions (c. f. p. ’s) defined by |(ji )ni viγixi〉 :
[ [|(j1)
n1v1γ1x1〉 |(j2)n2v2γ2x2〉
]Γ2 ... |(jk )nk vkγkxk 〉
]Γk
~Γk = ~Γk−1 + ~γk
vi ≡ seniority i. e. number of particles non coupled by pairs
to J = 0
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The interaction in second quantization
H =
A∑
ij
ǫia†i aj +
1
4
A∑
ijkl
〈ij|V res.|kl〉a†i a
†i al ak
= H(0) + V
Introducing the operators: ajm = (−1)j+m aj−m and defining thecoupling of tensors as:
[a†j1a†j2]JM =
∑
m1m2
〈j1m1j2m2|JM〉a†j1m1
a†j2m2
we obtain:
V = − 14
∑
j1 j2 j3 j4
〈j1j2|V |j3 j4〉JT ×
√
(2J + 1)(2T + 1)(1 + δ12)(1 + δ34)
×[
[a†
j1a†
j2]JT × [aj3 aj4]
JT]00
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Matrix elements in coupled basis
Two body interaction can always be recoupled as:
V =[
[ Oω1Oω2
]Ω2 ... Oωk
]0
with
Oωi = (1,a†j , aj , (a
†j a
†j )
λ, (aj aj)λ, (a†
j aj)λ
[
(a†j a
†j )
λaj
]µ,[
a†j (aj aj)
λ]µ
,[
(a†j a
†j )
λ(aj aj)λ]0)
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Matrix elements in coupled basis
〈nγΓx‖V ||n′γ′Γ′x ′〉 = (−1)
∑
i=2
ni (Ni−1−N′
i−1)
〈n1v1γ1x1||Oω1 ||n′
1v ′1γ
′1x ′
1〉
×∏
i=2
√(2Γi + 1).(2Γ′
i + 1).(2Ωi + 1)× 〈niγixi ||Oωi ||n′
i γ′i x
′i 〉
Γi−1 γi Γi
Γ′i−1 γ
′i Γ′
iΩi−1 ωi Ωi
n = (n1, ..., nk): number of particles in each orbital ji ,
γ = (γ1, ..., γk ): angular momentum of each state (ji)ni ,
x = (x1, ..., xk ): additional quantum numbers (e. g. seniority) for eachstate (ji)
ni ,
Γ = (Γ1, ..., Γk ): successive intermediate couplings
Ni =i∑
r=1
nr : total number of particules in the orbits j1, ..., jk
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42Ca normal states
For “normal” 0+ states, one needs to
diagonalize the 4×4 matrix:
(f 72
)2 (p 32
)2 (p 12
)2 (f 52
)2
0.0 × 2 −0.783 −0.714 −2.788+(−1.920)
2.0 × 2 −1.465 −0.777+(−1.206)
4.0 × 2 −0.392+(−0.249)
6.5 × 2+(−1.687)
42Ca
0+ 0
2+ 1386
4+ 2384
2+ 4071
0+ 5292
0+ 0
2+ 1524
0+ 1837
2+ 2424
4+ 2752
3– 3447
shell model exp.
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Diagonalization of the Hamiltonian
pf -shell valence space: 1f7/2,2p3/2,2p1/2,1f5/2
nucleus m-scheme jj-scheme(ANTOINE) (NATHAN)
48Cr 1,963,461 41,35554Fe 345,400,174 5,220,62156Fe 501,113,392 7,413,48856Ni 1,087,455,228 15,443,684
Impossible to store Hamiltonian matrix!
Still possible to compute HΨ.
Diagonalization using an iterative algorithm.
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Choice of the basis
• m scheme
|Φα〉 =∏
i=nljmτ
a†i|0〉 = a
†i1...a†
iA|0〉
Simple HIJ but Maximal size:
D ∼(
dπp
).(
dνn
)
Huge dimensions of the matrices (109)
storage of Lanczos vectors on diskAMD Opteron 64bits 2.2 GHz / 8 Gb RAM
56Ni: D=109 1h30/it.
Very large cases:splitting of the initial and final vectors
Ψi,f =⋃
mΨm
i,f
Ψ(m)f
=∑
nH(m,n)Ψ
(n)i
• Coupled scheme
[ [
|(j1)n1 v1γ1x1〉 |(j2)
n2 v2γ2x2〉]Γ2
...|(jk )nk vkγk xk 〉
]Γk
Reduced dimensions BUT complicated andmuch more non zero termsSmall dimensions of the matrices (107)Parallelization : each processor has the ini-tial and a final vector and final vectors areadded
Ψ(k)f
= H(k)Ψi ; Ψf =∑
k
Ψ(k)f
ImaBIO Cluster 24 nodes Xeon 2.8 GHzNuc Theo Cluster 10 nodes Xeon 2.7 GHz
128Xe GS: D=70 106 (DM=0=1010)
400 Gb precalculation storage
1014 non zero terms !!! 8h/it.(34 procs)
2+ out of reach
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Choice of the basis
• m scheme
|Φα〉 =∏
i=nljmτ
a†i|0〉 = a
†i1...a†
iA|0〉
Simple HIJ but Maximal size:
D ∼(
dπp
).(
dνn
)
Huge dimensions of the matrices (109)
storage of Lanczos vectors on diskAMD Opteron 64bits 2.2 GHz / 8 Gb RAM
56Ni: D=109 1h30/it.
Very large cases:splitting of the initial and final vectors
Ψi,f =⋃
mΨm
i,f
Ψ(m)f
=∑
nH(m,n)Ψ
(n)i
• Coupled scheme
[ [
|(j1)n1 v1γ1x1〉 |(j2)
n2 v2γ2x2〉]Γ2
...|(jk )nk vkγk xk 〉
]Γk
Reduced dimensions BUT complicated andmuch more non zero termsSmall dimensions of the matrices (107)Parallelization : each processor has the ini-tial and a final vector and final vectors areadded
Ψ(k)f
= H(k)Ψi ; Ψf =∑
k
Ψ(k)f
ImaBIO Cluster 24 nodes Xeon 2.8 GHzNuc Theo Cluster 10 nodes Xeon 2.7 GHz
128Xe GS: D=70 106 (DM=0=1010)
400 Gb precalculation storage
1014 non zero terms !!! 8h/it.(34 procs)
2+ out of reach
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Comparison m-scheme/coupled scheme
Coupled scheme is preferable for:
the calculation of 0+ states
the calculation of a large number of states (structure
function)
seniority truncation
In all other cases, m-scheme, because more simple, is more
efficient:
Yrast band calculation
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Limitations
For m-scheme, the size of the basis is THE limitation
For coupled scheme, the number of non-zero terms is THE
limitation
Dimensions HIJ 6= 0
M=0(M=0)(J=0)
(M=0)(J=4)
M=0(J=0)(M=0)
(J=4)(M=0)
48Cr 1.9 106 47.5 7.9 0.8 109 0.6 16.752Fe 1.1 108 61.9 9.4 7.4 1010 2.4 83.256Ni 1.1 109 70.4 10.3 9.6 1011 5.3 19460Zn 2.3 109 73.3 10.6 2.2 1012 6.8 254
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Lanczos algorithm
The Lanczos algorithm consist in the construction of an
orthonormal basis by orthogonalization of the states Hn|1〉,obtained by the repeated action of the hamiltonian H, on a
basis state |1〉 called pivot. From this procedure results a
tridiagonal matrix. In the first step we write:
H|1〉 = E11|1〉 + E12|2〉
where E11 is just 〈1|H|1〉 = 〈H〉,the mean value of H.
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Lanczos Algorithm
E12 is obtained by normalization :
E12|2〉 = H|1〉 - E11|1〉 = (H − E11)|1〉
In the second step:
H|2〉 = E21|1〉 + E22|2〉 + E23|3〉
The hermiticity of H implies E21 = E12
E22 is just 〈2|H|2〉and E23 is obtained by normalization :
E23|3〉 = (H− E22) |2〉 - E21|1〉
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Lanczos Algorithm
At rank N, the following relations hold:
H|N〉 = ENN−1|N − 1〉 + ENN|N〉 + ENN+1|N + 1〉
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Lanczos Algorithm
At rank N, the following relations hold:
H|N〉 = ENN−1|N − 1〉 + ENN|N〉 + ENN+1|N + 1〉
EN−1N = ENN−1, ENN = 〈N|H|N〉
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Lanczos Algorithm
At rank N, the following relations hold:
H|N〉 = ENN−1|N − 1〉 + ENN|N〉 + ENN+1|N + 1〉
EN−1N = ENN−1, ENN = 〈N|H|N〉
and ENN+1|N + 1〉 = (H − ENN)|N〉 - ENN−1|N − 1〉
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Lanczos Algorithm
It is explicit that we have built a tridiagonal matrix
〈I|H|J〉 = 〈J|H|I〉 = 0 if |I − J| > 1
E11 E12 0 0 0 0
E12 E22 E23 0 0 0
0 E32 E33 E34 0 0
0 0 E43 E44 E45 0
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Lanczos convergence
RANDOM STARTING VECTOR3
-6.345165 11.335118 29.1206876
-21.344259 -7.802025 4.637278 16.927858 29.3083099
-30.092574 -19.653950 -9.343311 0.467972 10.26573112
-32.722076 -24.462806 -17.104890 -9.353111 -1.62885715
-32.930624 -26.709841 -22.335011 -15.957805 -9.40164518
-32.952147 -28.028244 -24.233122 -19.625844 -14.77267921
-32.953570 -28.413699 -25.350732 -22.676041 -18.18035624
-32.953655 -28.537584 -26.244093 -23.883982 -20.53429827
-32.953658 -28.559930 -26.542899 -24.362551 -22.19786630
-32.953658 -28.563001 -26.646165 -24.887184 -23.55979933
-32.953658 -28.564277 -26.912739 -26.199181 -24.29916536
-32.953658 -28.564535 -27.102898 -26.382496 -24.40935739
-32.953658 -28.564567 -27.148522 -26.416873 -24.52905542
-32.953658 -28.564570 -27.156735 -26.425250 -24.72407845
-32.953658 -28.564570 -27.158085 -26.427319 -24.91091548
-32.953658 -28.564570 -27.158371 -26.428021 -25.107898
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Lanczos convergence
RANDOM STARTING VECTOR3
-6.345165 11.335118 29.1206876
-21.344259 -7.802025 4.637278 16.927858 29.3083099
-30.092574 -19.653950 -9.343311 0.467972 10.26573112
-32.722076 -24.462806 -17.104890 -9.353111 -1.62885715
-32.930624 -26.709841 -22.335011 -15.957805 -9.40164518
-32.952147 -28.028244 -24.233122 -19.625844 -14.77267921
-32.953570 -28.413699 -25.350732 -22.676041 -18.18035624
-32.953655 -28.537584 -26.244093 -23.883982 -20.53429827
-32.953658 -28.559930 -26.542899 -24.362551 -22.19786630
-32.953658 -28.563001 -26.646165 -24.887184 -23.55979933
-32.953658 -28.564277 -26.912739 -26.199181 -24.29916536
-32.953658 -28.564535 -27.102898 -26.382496 -24.40935739
-32.953658 -28.564567 -27.148522 -26.416873 -24.52905542
-32.953658 -28.564570 -27.156735 -26.425250 -24.72407845
-32.953658 -28.564570 -27.158085 -26.427319 -24.91091548
-32.953658 -28.564570 -27.158371 -26.428021 -25.107898
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Lanczos convergence
RANDOM STARTING VECTOR3
-6.345165 11.335118 29.1206876
-21.344259 -7.802025 4.637278 16.927858 29.3083099
-30.092574 -19.653950 -9.343311 0.467972 10.26573112
-32.722076 -24.462806 -17.104890 -9.353111 -1.62885715
-32.930624 -26.709841 -22.335011 -15.957805 -9.40164518
-32.952147 -28.028244 -24.233122 -19.625844 -14.77267921
-32.953570 -28.413699 -25.350732 -22.676041 -18.18035624
-32.953655 -28.537584 -26.244093 -23.883982 -20.53429827
-32.953658 -28.559930 -26.542899 -24.362551 -22.19786630
-32.953658 -28.563001 -26.646165 -24.887184 -23.55979933
-32.953658 -28.564277 -26.912739 -26.199181 -24.29916536
-32.953658 -28.564535 -27.102898 -26.382496 -24.40935739
-32.953658 -28.564567 -27.148522 -26.416873 -24.52905542
-32.953658 -28.564570 -27.156735 -26.425250 -24.72407845
-32.953658 -28.564570 -27.158085 -26.427319 -24.91091548
-32.953658 -28.564570 -27.158371 -26.428021 -25.107898
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Lanczos convergence
RANDOM STARTING VECTOR3
-6.345165 11.335118 29.1206876
-21.344259 -7.802025 4.637278 16.927858 29.3083099
-30.092574 -19.653950 -9.343311 0.467972 10.26573112
-32.722076 -24.462806 -17.104890 -9.353111 -1.62885715
-32.930624 -26.709841 -22.335011 -15.957805 -9.40164518
-32.952147 -28.028244 -24.233122 -19.625844 -14.77267921
-32.953570 -28.413699 -25.350732 -22.676041 -18.18035624
-32.953655 -28.537584 -26.244093 -23.883982 -20.53429827
-32.953658 -28.559930 -26.542899 -24.362551 -22.19786630
-32.953658 -28.563001 -26.646165 -24.887184 -23.55979933
-32.953658 -28.564277 -26.912739 -26.199181 -24.29916536
-32.953658 -28.564535 -27.102898 -26.382496 -24.40935739
-32.953658 -28.564567 -27.148522 -26.416873 -24.52905542
-32.953658 -28.564570 -27.156735 -26.425250 -24.72407845
-32.953658 -28.564570 -27.158085 -26.427319 -24.91091548
-32.953658 -28.564570 -27.158371 -26.428021 -25.107898
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Lanczos convergence
48Cr
Dim (t=2) = 6.105
Dim (full space) = 2.106
Ca40
f7/2 f7/2
Π ν
f5/2p1/2p3/2
f5/2p1/2p3/2
STARTING VECTOR :EIGENVECTOR OF A SMALLER SPACEITER= 1 DIA= -31.105920 NONDIA= 4.642871
3-32.578285 -21.260843 5.090417
6-32.929531 -27.208522 -16.116780 -1.200061 14.816894
9-32.952149 -28.024347 -22.702052 -13.782511 -3.514506
12-32.953553 -28.345536 -25.965169 -20.636169 -12.806719
15-32.953655 -28.528301 -26.951521 -22.532438 -18.004439
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Numerical instabilities
STATE 2*J= 4 LANCZOS UNTIL CONVERGENCE OF THE EIGENVALUE N= 6
21 -18.887126 -16.682989 -15.490861 -13.688336 -12.096178 -9.739625CONVERGENCE DELTA E= 0.001230 0.303215 0.650853 0.985329 1.914066 2.536821
36 -18.887244 -17.161904 -16.549737 -15.522718 -14.138934 -13.409580CONVERGENCE DELTA E= 0.000000 0.000101 0.000148 0.000470 0.016596 0.449186
54 -18.887244 -17.161909 -16.549748 -15.522805 -15.130465 -14.294037CONVERGENCE DELTA E= 0.000000 0.000000 0.000000 0.000000 0.079796 0.017144
57 -18.887244 -18.322405 -17.161909 -16.549748 -15.522805 -15.125042-14.292844 -14.099706 -13.401536 -13.052378 -12.605377 -11.799747
CONVERGENCE DELTA E= 0.000000 1.160496 0.612161 1.026942 0.392340 0.831005
60 -19.860305 -18.887244 -17.161909 -16.549748 -15.522805 -15.135225CONVERGENCE DELTA E= 0.973061 0.564839 0.000000 0.000000 0.000000 0.010184
6666 -19.877245 -18.887244 -17.161909 -16.549748 -15.522805 -15.136157
CONVERGENCE DELTA E= 0.000144 0.000000 0.000000 0.000000 0.000000 0.000082
GROUND-STATE (AMONG THE READ STATES) ENERGY= -19.87724
N,Z= 4 2 2*J= 0 P=0 N= 1 2*M= 0 C= 4 EXC = 0.00000 E= -19.87724N,Z= 4 2 2*J= 4 P=0 N= 1 2*M= 0 C= 4 EXC = 0.00000 E= -19.87724N,Z= 4 2 2*J= 4 P=0 N= 2 2*M= 0 C= 4 EXC = 0.99000 E= -18.88724
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Computing session
This afternoon:
you will calcule m-scheme dimensions with paper and
pencil
you will start to use Antoine code to set up basis, valence
space etc ...
you will check your basis calculations with the code
you will learn start to perform the first diagonalisations