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Page 1: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Perspectives in Low-Energy Nuclear Physics

Robert Roth

Page 2: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

A Kind Request...

Dear Robert,

David and I would like to ask you if you are willing to give a colloquium at TRIUMF on February 19th 2016.

This is the week before the Nuclear Theory workshop, during which we will have another colloquium by Thomas Papenbrock on "Recent Advances in Nuclear Theory".

In the light of this, we thought that having a preparatory talk where the big questions in nuclear physics are introduced in a very simple manner would be useful…

We feel this will help to communicate the importance of nuclear physics and nuclear theory to the general laboratory…

Please let us know if you are interested in this.

Thanks a lot, Sonia

2

Page 3: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

The Big Picture

Page 4: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Low-Energy Nuclear Physics

4

Diversity• structure emerging

from microscopic dynamics

• thousands of isotopes, many very special

• zoo of phenomena: shell structure, clustering, deformation, stability, excitations, resonances, transitions, decays, reactions,…

Complexity• multi-physics:

strong, weak and el.mag. interactions

• multi-scale: from keV to GeV

• multi-process: structure, decays and reactions

• multi-observable: energies, el.mag.,…

Impact• key input for under-

standing the evolution of the universe

• tiny things have huge implications: deuteron, Hoyle state,…

• foundation for atomic and molecular physics, chemistry, solid state,…

• direct applications

…a multi-faceted lab connecting fundamental

physics with daily life

Page 5: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Low-Energy Nuclear Theory

5

the most challenging quantum many-body problem…

…try a non-relativistic quantum description with nucleons as relevant degrees of freedom

self-bound system

competition of large energy contributions

bound and continuum

states

translational & rotational symmetry

significant three-body

forces

residual van der Waals interaction

nucleons are composite themselves

range of different

observables

dominated by correlations

interaction inherits

complexity of QCD

systems of 2 - 300 nucleons

weak binding and threshold physics

Page 6: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

The Problem

6

H |i = E |i

…we need additional models to construct a nuclear interaction

to start with

We do not know the interaction…

…we need truncations or approximations to make the

problem tractable

We do not know how to solve the equation…

Page 7: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Strategy I: Phenomenology

§ pick a simple approximation scheme for the Schrödinger equation tailored for the observables of interest

§ construct a computationally convenient model for the nuclear interaction compatible with this approximation

§ fit the parameters of the interaction model to observables within the chosen approximation scheme

7

H |i = E |i

Skyrme-Hartree-Fock

approximate many-body state by single Slater determinant and

parameterize interaction with contact terms

Valence-Space Shell Model

freeze core nucleons and treat a few valence nucleons in small

valence space with fitted interaction matrix elements

Page 8: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Strategy II: Ab Initio

§ construct realistic nuclear interactions based on as much QCD input as possible and fit to few-nucleon properties in exact calculations

§ solve the Schrödinger equation using systematic truncations with controlled uncertainties

8

H |i = E |i

different many-body methods can employ the

same interaction

different interactions can be tested in one many-body

approach

interactions are independent of many-body

framework

Page 9: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Interactions

Page 10: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Nature of the Nuclear Interaction

§ nuclear interaction is not fundamental

§ residual force analogous to van der Waals interaction between neutral atoms

§ based on QCD and induced via polarization of quark and gluon distributions of nucleons

§ encapsulates all the complications of the QCD dynamics and the structure of nucleons

§ acts only if the nucleons overlap, i.e. at short ranges

§ irreducible three-nucleon interactions are important

10

Nature of the Nuclear Interaction

∼ 1.6fm

ρ−1/30 = 1.8fm

NN-interaction is not fundamental

analogous to van der Waals interac-tion between neutral atoms

induced via mutual polarization ofquark & gluon distributions

acts only if the nucleons overlap, i.e. atshort ranges

genuine 3N-interaction is important

9

Page 11: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Hatsuda, Aoki, Ishii, Beane, Savage, Bedaque,...

Tomorrow... from Lattice QCD

§ first attempts towards construction of nuclear interactions directly from lattice QCD simulations

§ compute relative two-nucleon wave function on the lattice

§ invert Schrödinger equation to extract effective two-nucleon potential

§ only schematic results so far (unphysical masses and mass dependence, model dependence,…)

§ alternatives: phase-shifts or low-energy constants from lattice QCD

11

Nuclear Interaction from Lattice QCD

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 0.5 1.0 1.5 2.0

NN

wa

ve f

un

ctio

n φ

(r)

r [fm]

1S03S1

-2 -1 0 1 2 -2-1

01

20.5

1.0

1.5

φ(x,y,z=0;1S0)

x[fm] y[fm]

φ(x,y,z=0;1S0)

0

100

200

300

400

500

600

0.0 0.5 1.0 1.5 2.0

VC

(r)

[Me

V]

r [fm]

-50

0

50

100

0.0 0.5 1.0 1.5 2.0

1S03S1 N.Ishiietal.,PRL99,022001(2007)

first steps towards constructionof a nuclear interaction throughlattice QCD simulations

compute relative two-nucleonwavefunction on the lattice

invert Schrödinger equation toobtain local ‘effective’ two-nucleon potential

schematic results so far (un-physical quark masses, S-waveinteractions only,...)

10

Page 12: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Beane et al., PRD87, 034506 (2013), PRC88, 024003 (2013)

Tomorrow... from Lattice QCD

12

d nn 3He 4He nS L3 H L

3 He S3He L

4 He H-dib nX LL4 He

1+0+

12

+

0+

1+

12

+

32

+

12

+

32

+

0+

0+

0+

1+

0+

0+

s=0 s=-1 s=-2

2-Body 3-Body 4-Body

-160

-140

-120

-100

-80

-60

-40

-20

0

DEHMe

VL

mπ ~ 800 MeV

(Hyper)Nuclei from QCD

Extensive study of s-shell nuclei and hypernuclei, and baryon-baryon interactions at SU(3) symmetric point

Beane et al, Phys.Rev. D87 (2013) 3, 034506, Phys.Rev. C88 (2013) 2, 024003

Page 13: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Today... from Chiral EFT

13

§ low-energy effective field theory for relevant degrees of freedom (π,N) based on symmetries of QCD

§ explicit long-range pion dynamics

§ unresolved short-range physics absorbed in contact terms, low-energy constants fit to experiment

§ systematic expansion in a small parameter with power counting enable controlled improvements and error quantification

§ hierarchy of consistent NN, 3N, 4N,... interactions

§ consistent electromagnetic and weak operators can be constructed in the same framework

Weinberg, van Kolck, Machleidt, Entem, Meißner, Epelbaum, Krebs, Bernard,...

Ä Ç ´

É

¼

£

¼

µ

Æ Ä Ç ´

É

¾

£

¾

µ

Æ

¾

Ä Ç ´

É

¿

£

¿

µ

Æ

¿

Ä Ç ´

É

NN 3N 4N

LO

NLO

N2LO

N3LO

£

µ

Page 14: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Many Options

§ standard chiral NN+3N • NN: N3LO, Entem&Machleidt, nonlocal, cutoff 500 MeV • 3N: N2LO, Navratil, local, cutoff 500 (400) MeV

§ nonlocal LO…N3LO • NN: LO…N3LO, Epelbaum, nonlocal, cutoff 450…600 MeV • 3N: N2LO, Nogga, nonlocal, cutoff 450…600 MeV

§N2LO-opt, N2LO-sat, … • NN: N2LO, Ekström et al., nonlocal, cutoff 500 MeV • 3N: N2LO, Ekström et al., nonlocal, cutoff 500 MeV

§ local N2LO • NN: N2LO, Gezerlis et al., local, cutoff 1.0…1.2 fm • 3N: N2LO, Gezerlis et al., local, cutoff 1.0…1.2 fm

§ semilocal LO…N4LO • NN: LO…N4LO, Epelbaum, semilocal, cutoff 0.8…1.2 fm • 3N: N2LO…N3LO, LENPIC, semilocal, cutoff 0.8…1.2 fm

14

first generation, most widely used up to now

also first generation, but scarcely used

improved fitting, also many-body inputs

designed specifically for QMC applications

order-by-order uncertainty estimates

all these interactions are

equally valid, use them all

to study uncertainties

Page 15: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Many-Body Solution - Eigenvalue Problem -

Page 16: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

0BBBBBBBBBBBBBB@

...

... h|H |0 i ...

...

1CCCCCCCCCCCCCCA

0BBBBBBBBBBBBBB@

...

C(n)0

...

1CCCCCCCCCCCCCCA

= En

0BBBBBBBBBBBBBB@

...

C(n)

...

1CCCCCCCCCCCCCCA

Robert Roth - TU Darmstadt

Eigenvalue Problem

§ start from many-body Schrödinger equation

16

§ define an many-body basis and expand eigenstates in this basis

§ convert Schrödinger equation into a matrix eigenvalue problem

|ni =X

C(n) |i

H |ni = En |ni

numerically solve large-scale

matrix eigenvalue problem for few

low-lying eigenvalues

up to 1010 x 1010

Page 17: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Configuration Interaction

§ have to introduce truncations of the basis to make the Hamilton matrix finite and numerically tractable

• single-particle truncation (full CI): truncate the underlying single-particle basis, e.g., at a maximum single-particle energy emax, and construct all possible Slater determinants

• many-body truncation (NCSM): truncate the many-body Slater-determinant basis at a maximum number of harmonic-oscillator excitation quanta Nmax

17

one has to demonstrate convergence with respect to the

model-space truncation for accurate results

incomplete convergence as only source of uncertainties in

the many-body treatment

model space dimension grows dramatically with

truncation parameter emax or Nmax and particle number

Page 18: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Convergence

18

0+

1+

2+

3+

E@MeVD

-32

-30

-28

-26

-24

-22

-20

-18

0+

1+

2+

3+

Nmax

E x@MeVD

2 4 6 8 10 12 14

0

1

2

3

4

5

6

0+

0+

0+

1+

2+

E@MeVD

-95

-90

-85

-80

-75

-70

0+

0+

0+

1+

2+

Nmax

E x@MeVD

2 4 6 8 10 120

5

10

15

Exp.Exp.

IT-NCSM

chiral NN+3N EM, 500 MeV

α = 0.08 fm4

ħΩ = 20 MeV

6Li 12C

convergence depends very much on

observable

extrapolation techniques and softening of

Hamiltonian help

convergence defines range of applicability of

CI methods

Page 19: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

0+1

1+0

2+0

3+0E X@MeVD

0

1

2

3

4

5

Robert Roth - TU Darmstadt

Calci, Roth; arXiv:1601.07209

p-Shell Spectroscopy: Sensitivity

§ of course, spectra depend on choice of initial chiral NN+3N interaction, but the dependence is not dramatic

§ important contribution to the total theory uncertainty 19

EM N2LOopt 450/500 600/500 550/600 450/700 600/700 BandEGM N2LO

NN +3N NN +3N NN +3N NN +3N NN +3N NN +3N NN +3N NN +3N

6Liα = 0.08 fm4 ħΩ =16 MeV Nmax = 10

Page 20: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

0+0

0+0

0+0

1+0

1+1

2+0

2+0

4+0

E X@MeVD

0

2

4

6

8

10

12

14

16

Robert Roth - TU Darmstadt

p-Shell Spectroscopy: Sensitivity

20

12C

NN +3N NN +3N NN +3N NN +3N NN +3N NN +3N NN +3N NN +3N

EM N2LOopt 450/500 600/500 550/600 450/700 600/700 BandEGM N2LO

Calci, Roth; arXiv:1601.07209

§ individual states show systematic disagreement with experiment: § second 0+: Hoyle state, cluster structure not captured in HO basis § first 1+: systematic problem with N2LO-3N interaction ?

α = 0.08 fm4 ħΩ =16 MeV

Nmax = 8

Page 21: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

p-Shell Spectroscopy: Correlations

21

QH2+L @e fm2D

BHE2,2+->0+L@e

2fm4D

3 4 5 6 7 8 9

5

6

7

8

Calci, Roth; arXiv:1601.07209

12C§ electric quadrupole (E2)

observables involving 0+ ground state & first excited 2+

§model-space convergence is terrible, E2 operator sensitive to long-range wave functions

Nmax NN/3N2 /

4 /

6 /

8 /

Exp.

ħΩ =16 MeV

Page 22: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

p-Shell Spectroscopy: Correlations

§ electric quadrupole (E2) observables involving 0+ ground state & first excited 2+

§model-space convergence is terrible, E2 operator sensitive to long-range wave functions

§ extremely robust correlation predicted by NCSM for all interactions and model spaces

22

QH2+L @e fm2D

BHE2,2+->0+L@e

2fm4D

3 4 5 6 7 8 9

5

6

7

8

Calci, Roth; arXiv:1601.07209

Nmax NN/3N2 /

4 /

6 /

8 /

Exp.

12C

ħΩ =16 MeV

Page 23: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

p-Shell Spectroscopy: Correlations

§ electric quadrupole (E2) observables involving 0+ ground state & first excited 2+

§model-space convergence is terrible, E2 operator sensitive to long-range wave functions

§ extremely robust correlation predicted by NCSM for all interactions and model spaces

§ predict Q(2+) with very high accuracy based on experimental datum for B(E2)

23

QH2+L @e fm2D

BHE2,2+->0+L@e

2fm4D

3 4 5 6 7 8 9

5

6

7

8

Calci, Roth; arXiv:1601.07209

Exp.

Nmax NN/3N2 /

4 /

6 /

8 /

12C

new way to exploit

ab initio calculations and to

bridge to effective models

ħΩ =16 MeV

Page 24: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

p-Shell Spectroscopy: Precision

24

mH1+L @mND

BHM1,0+->1+L@m

N2D

0.82 0.83 0.84 0.85 0.86

15

15.2

15.4

15.6

15.8

Calci, Roth; arXiv:1601.07209

§magnetic dipole (M1) observables involving 1+ ground state & 0+ excited state

§ dipole moment and B(M1) are very robust (few % changes)

§mild systematic model-space dependence of B(M1)

§ dipole moment affected by 3N interaction and in slight disagreement with experiment

Exp.

6Li

Nmax NN/3N4 /

6 /

8 /

10 /

ready for precision studies,

e.g., on electromagnetic

two-body currents

ħΩ =16 MeV

Page 25: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Many-Body Solution - Unitary Transformation -

Page 26: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

0BBBBBBBBBBBBBB@

...

... h|H |0 i ...

...

1CCCCCCCCCCCCCCA

Robert Roth - TU Darmstadt

Unitary Transformations

§ partially diagonalize Hamilton matrix through a unitary transformation and read-off eigenvalues from the diagonal

26

§ continuous unitary transformation of many-body Hamiltonian

0BBBBBBBBBBBBBB@

...

... h|H |0 i ...

...

1CCCCCCCCCCCCCCA

morphs the initial Hamilton matrix ( ) to diagonal form ( )

H = U† H U

= 0 !

U

Page 27: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Glazek, Wilson, Wegner, Perry, Bogner, Furnstahl, Hergert, Roth,...

Similarity Renormalization Group

§ consistent unitary transformation of Hamiltonian and observables

27

continuous unitary transformation to pre-diagonalize the Hamiltonian with respect

to a given basis

H = U†H U O = U

†O U

d

dH = [,H]

d

dO = [,O]

d

dU = U

§ the physics of the transformation is governed by the dynamic generator ηα

§ design generator for desired diagonalization or decoupling pattern

§ flow equations for Hα and Uα with continuous flow parameter α

Free-Space SRG

well established for softening

the Hamiltonian in two- and

three-body space

Page 28: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Tsukiyama, Bogner, Schwenk, Hergert,…

In-Medium SRG

§ flow equation for Hamiltonian and Wegner-type generator

§write everything in normal ordered form with respect to a single- or multi-determinantal reference state

28

use SRG flow equations for normal-ordered Hamiltonian to decouple

many-body reference state from excitations

0p-0h 1p-1h 2p-2h 3p-3h

3p-3h

2p-2h

1p-1h

0p-0h

0p-0h 1p-1h 2p-2h 3p-3h

3p-3h

2p-2h

1p-1h

0p-0h

d

dsH(s) =(s), H(s)

(s) =H(s), Hoff-diag(s)

H(s) = E(s) +X

jƒ j (s) A

j +

1

4

X

jkjk(s) A

jk +

1

36

X

jkmnWjk

mn(s) Ajkmn

additional truncation that causes

uncertainties

discard normal-ordered three-body

terms

Page 29: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Flowing Energy

29

16O chiral NN+3N Λ3N=400 MeV α=0.08 fm4

ħΩ=20 MeV emax=12

Nmax=0reference state

E(s)

IT-NCSM

Hamilton matrix in Nmax=2 space

Page 30: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt 30

Ground States of Oxygen IsotopesGround States of Oxygen IsotopesHergert et al., PRL 110, 242501 (2013)

NN+3Nind(chiral NN)

12 14 16 18 20 22 24 26A

-180

-160

-140

-120

-100

-80

-60

-40

.

E[M

eV]

NN+3Nfull(chiral NN+3N)

12 14 16 18 20 22 24 26A

AO

experiment

! IT-NCSM

Λ3N = 400 MeV, α = 0.08 fm4, E3mx = 14, optimal hΩ

24

Hergert et al., PRL 110, 242501 (2013)

chiral NN chiral NN+3N

Page 31: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt 31

Ground States of Oxygen IsotopesGround States of Oxygen IsotopesHergert et al., PRL 110, 242501 (2013)

NN+3Nind(chiral NN)

12 14 16 18 20 22 24 26A

-180

-160

-140

-120

-100

-80

-60

-40

.

E[M

eV]

NN+3Nfull(chiral NN+3N)

12 14 16 18 20 22 24 26A

AO

experiment

! IT-NCSM

MR-IM-SRG

Λ3N = 400 MeV, α = 0.08 fm4, E3mx = 14, optimal hΩ

31

Hergert et al., PRL 110, 242501 (2013)

chiral NN chiral NN+3N

Page 32: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Hergert et al., PRL 110, 242501 (2013)

32

Ground States of Oxygen IsotopesGround States of Oxygen IsotopesHergert et al., PRL 110, 242501 (2013)

NN+3Nind(chiral NN)

12 14 16 18 20 22 24 26A

-180

-160

-140

-120

-100

-80

-60

-40

.

E[M

eV]

NN+3Nfull(chiral NN+3N)

12 14 16 18 20 22 24 26A

AO

experiment

! IT-NCSM

MR-IM-SRG

CCSD Λ-CCSD(T)

Λ3N = 400 MeV, α = 0.08 fm4, E3mx = 14, optimal hΩ

32

different many-bodyapproaches using the same

chiral NN+3N interaction giveconsistent results minor differences are

understood in terms of uncertainties due to truncations

chiral NN chiral NN+3N

Page 33: Perspectives in Low-Energy Nuclear Physicsadmin.triumf.ca/docs/seminars/Sem0122546988-225-1.rroth_triumf_… · Calci, Roth; arXiv:1601.07209 § individual states show systematic

Robert Roth - TU Darmstadt

Merging CI and IM-SRG

§ combine CI/NCSM with IM-SRG to get the best aspects of both methods

33

§ solve NCSM problem in small Nmax

§ extract reference state

§ solve MR-IM-SRG flow equations

§ decoupling of particle-hole excitations in many-body space

§ solve CI problem with IM-SRG evolved Hamiltonian

§ extract ground and excitation energies and other observables

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Robert Roth - TU Darmstadt

Gebrerufael et al.; in prep.

CI-IM-SRG: Ground State

§ instead of using the zero-body piece of the normal-ordered Hamiltonian, we can use the complete flowing Hamiltonian in a CI calculation

34

12C chiral NN+3N Λ3N=400 MeV α=0.08 fm4

ħΩ=20 MeV emax=12

Nmax=0reference state

Nmax

0 2 4 68

10

E(s)

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Robert Roth - TU Darmstadt

CI-IM-SRG: Ground State

35

12C chiral NN+3N Λ3N=400 MeV α=0.08 fm4

ħΩ=20 MeV emax=12

Nmax=0reference state

Gebrerufael et al.; in prep.

Nmax

0 2 4 68

10

§ instead of using the zero-body piece of the normal-ordered Hamiltonian, we can use the complete flowing Hamiltonian in a CI calculation

§ decoupling though the IM-SRG transformation causes ridiculously fast convergence of CI calculation

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Robert Roth - TU Darmstadt

CI-IM-SRG: Ground State

36

12C chiral NN+3N Λ3N=400 MeV α=0.08 fm4

ħΩ=20 MeV emax=12

Nmax=0reference state

Gebrerufael et al.; in prep.

Nmax

0 2 4 68

10

Hamilton matrix in Nmax=2 space

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Robert Roth - TU Darmstadt

CI-IM-SRG: Ground State

37

12C chiral NN+3N Λ3N=400 MeV α=0.08 fm4

ħΩ=20 MeV emax=12

Nmax=0reference state

Gebrerufael et al.; in prep.

Nmax

0 2 4 68

10

effects of IM-SRG truncation at the normal-ordered two-body level

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Robert Roth - TU Darmstadt

CI-IM-SRG: Excited States

38

12C chiral NN+3N Λ3N=400 MeV α=0.08 fm4

ħΩ=20 MeV emax=12

Nmax=0reference state

Gebrerufael et al.; in prep.

2+

1+

§ from the same CI calculation we get the excited states

Nmax

0 2 4

0+

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Robert Roth - TU Darmstadt

CI-IM-SRG: Excited States

39

12C chiral NN+3N Λ3N=400 MeV α=0.08 fm4

ħΩ=20 MeV emax=12

Nmax=0reference state

Gebrerufael et al.; in prep.

2+

1+

§ from the same CI calculation we get the excited states

§ excitation energies only show subtle changes with IM-SRG flow…

Nmax

0 2 4 6

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Robert Roth - TU Darmstadt

CI-IM-SRG: Excited States

40

12C chiral NN+3N Λ3N=400 MeV α=0.08 fm4

ħΩ=20 MeV emax=12

Nmax=0reference state

Gebrerufael et al.; in prep.

2+

0+

§ from the same CI calculation we get the excited states

§ excitation energies only show subtle changes with IM-SRG flow… …but there are notable exceptions… Hoyle state?

1+

Nmax

0 2 4 6

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Robert Roth - TU Darmstadt

CI-IM-SRG: Spectrum

41

12C chiral NN+3N Λ3N=400 MeV α=0.08 fm4

ħΩ=20 MeV emax=12

Nmax=0reference state s=0.2 MeV-1

Gebrerufael et al.; in prep.

§ promising starting point for ab initio studies of arbitrary open-shell nuclei

CI-IM-SRG IT-NCSM

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Robert Roth - TU Darmstadt

Tsukiyama, et al., PRC 85, 061304(R) (2012); Bogner el al.; PRL 113, 142501 (2014)…

Back to Phenomenology

§ the decoupling concept can also be used to connect ab initio methods to traditional phenomenological approaches

§ valence-space shell model: construct a valence-space interaction by decoupling core and excluded space from valence space though IM-SRG or Lee-Suzuki transformation

§ unification of nuclear structure approaches and their interpretation

42

4

MBPT IM-SRG NN+3N-ind

IM-SRG NN+3N(400)

Expt. IM-SRG NN+3N(500)

0

1

2

3

4

5

6

7

8

9

10

Ener

gy (M

eV)

0+

2+

2+ 2+

0+ 0+

(2+)2+

2+

(0+)0+

0+

4+

4+ (4+)

4+

2+

0+

2+

0+

3+

3+ 3+

3+

0+ 0+

2+

3+

2+

4+

0+

22O

FIG. 3. Excited state spectrum for 22O as in Fig. 2, withexperimental values from [48, 49].

gence at the IM-SRG(2) level.Turning to excitation spectra, since NN forces give a

reasonable description of low-lying spectra near 16O [29],we focus on the region of the new N = 14, 16 magic num-bers, and the limit of stability by considering 21−26O. Asshown in Ref. [24], microscopic valence-space Hamiltoni-ans from MBPT, calculated in the standard sd-shell, donot adequately reproduce experimental data, even with3N forces. With the inclusion of the f7/2 and p3/2 or-bitals, spectroscopy improves, indicating that a pertur-bative treatment of these orbitals may be insufficient.Given the nonperturbative character of IM-SRG, we ex-pect similar improvements already in the sd shell.We first consider the spectrum of 21O in Fig. 2. While

no calculation fully reproduces experiment, MBPT andIM-SRG correctly predict the ordering of the first twoexcited states with an initial 3N force, but the 1/2+ levellies too low in MBPT and too high in IM-SRG. Since theMBPT results are obtained with a softened N3LO inter-action with a re-fit 3N interaction [1, 2], disagreementsare both due to the different input Hamiltonians and thenonperturbative IM-SRG approach. We note that thetentative 7/2+ and 5/2+ assignments are reproduced inboth calculations, but the ordering is reversed in IM-SRGcompared to MBPT.The calculated IM-SRG spectra of 22O are compared

with MBPT [24] and experiment [48, 49] in Fig. 3. With-out initial 3N forces, the spectrum is too compressed.The 2+1 state, in particular, is 1.0MeV too low, contra-dicting the doubly magic nature of 22O. Unlike MBPT orthe phenomenological USDb Hamiltonian, the IM-SRGreproduces the correct ordering of the 3+1 and 0+2 states.Inclusion of initial 3N forces leads to significant improve-ment, and the final spectrum is very close to experiment.The extended-space MBPT calculations reproduce thehigh 2+1 state but have too uniform spacing and incor-rect 3+1 − 0+2 ordering.There are no bound excited states in 23O, only two

MBPT IM-SRG NN+3N-ind

IM-SRG NN+3N(400)

Expt. IM-SRG NN+3N(500)

0

1

2

3

4

5

6

7

Ener

gy (M

eV)

1/2+

5/2+

5/2+

1/2+

3/2+3/2+

1/2+

5/2+

3/2+

(5/2+)

1/2+

(3/2+)

1/2+

5/2+

3/2+

23O

FIG. 4. Excited state spectrum of 23O as in Fig. 2, withexperimental values from [50, 51].

3N(400) 3N(500) Expt. 3N(400) 3N(500) 3N(400) 3N(500)0

1

2

3

4

5

6

7

8

9

Ener

gy (M

eV)

0+

2+

0+

2+1+

3/2+

1/2+

5/2+

0+

1+

2+1+

3/2+0+ 0+

2+ 2+

1/2+

5/2+

24O 25O 26O

FIG. 5. Excited state spectra of 24−26O for Λ3N =400, 500MeV NN+3N-full Hamiltonians with !ω = 20MeV(dotted), !ω = 24MeV (solid), and λSRG dependence as inFig. 2, compared to experiment for 24O [52, 53].

higher-lying states, tentatively identified as 5/2+ and3/2+, indicating the sizes of the d5/2−s1/2 and d3/2−s1/2gaps, respectively [50, 51]. We show the calculated andexperimental spectra in Fig. 4. Again, the IM-SRGdoes not reproduce this spectrum without initial 3Nforces: the 5/2+ state is nearly 1MeV too low, but the5/2+ − 3/2+ gap close to experiment. Similar to MBPTwith initial 3N forces, the 5/2+ energy is almost exactlythat of experiment, only the 3/2+ is 1MeV too high. Dueto its position 2MeV above threshold, it is expected thatcontinuum effects will lower this state, bringing it closerto the experimental value.

As expected from the high 3/2+ state in 23O, wealso predict 24O to be doubly magic, but with a 2+1 en-ergy 1.2MeV higher than experiment, as seen in Fig. 5.Nonetheless, the 2+ − 1+ spacing is very close to ex-periment, and with continuum effects included, thesestates will be lowered. Finally, we present predictionsfor excited-state energies in the unbound 25,26O isotopes.

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Robert Roth - TU Darmstadt

New Era of Nuclear Structure Physics

43

§nuclear structure physics has evolved rapidly over the past few years

§many new ideas have emerged for nuclear interactions and many-body approaches… and more is coming

§moving towards a comprehensive theory of nuclear structure and reactions with quantified theory uncertainties

§ it’s fun to be part of it…

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Robert Roth - TU Darmstadt

J. Braun, E. Gebrerufael, T. Hüther, J. Langhammer,S. Schulz, H. Spiess, C. Stumpf, A. Tichai, R. Trippel, K. Vobig, R. WirthTechnische Universität Darmstadt

P. Navrátil, A. Calci TRIUMF, Vancouver

S. BinderOak Ridge National Laboratory

H. HergertNSCL / Michigan State University

J. Vary, P. MarisIowa State University

S. Quaglioni Lawrence Livermore National Laboratory

E. Epelbaum, H. Krebs & the LENPIC CollaborationUniversität Bochum, …

Epilogue

§ thanks to my group and my collaborators

44

Epilogue

thanks to my group & my collaborators

S. Binder, J. Braun, A. Calci, S. Fischer,E. Gebrerufael, H. Spiess, J. Langhammer, S. Schulz,C. Stumpf, A. Tichai, R. Trippel, R. Wirth, K. VobigInstitut für Kernphysik, TU Darmstadt

P. NavrátilTRIUMF Vancouver, Canada

J. Vary, P. MarisIowa State University, USA

S. Quaglioni, G. HupinLLNL Livermore, USA

P. PiecuchMichigan State University, USA

H. HergertOhio State University, USA

P. PapakonstantinouIBS/RISP, Korea

C. ForssénChalmers University, Sweden

H. Feldmeier, T. NeffGSI Helmholtzzentrum

JUROPA LOEWE-CSC EDISON

COMPUTING TIME

46