HIRFL -RIBLL - PowerPoint Presentation

Slide1

HIRFL -RIBLL

合作会议，上海，

2013.1Slide2

Contents

Motivation: physics of weakly bound deformed nuclei

Method: deformed coordinate-space HFB approachResults: surface deformations and continuum effectsSummary

HFB solvers and Continuum effects-------J.C. Pei

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Motivation: Physics

of

drip-line nuclei

RNB

facilities offer unprecedented opportunities to access unstable

nuclei

Challenging theoretical approaches

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From J.

Erler et al., Nature, 486, 509(2012)

HFB solvers and Continuum effects-------J.C. Pei

From

B. Sherrill’s talk at NS2012Slide4

Motivation: Physics of drip-line nuclei

Weakly-bound quantum systems

: density diffuse, halo structuresPairing induced continuum couplings

become important; BEC and BCS pairing coexistedNovel collective excitation modes: pygmy modes and etc.

Nuclear astrophysics: e.g

., neutron stars, symmetry energy

Testing ground for new effective interactions: UNEDF, 3-body forces

HFB solvers and Continuum effects-------J.C. Pei

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Motivation: Physics of deformed halos

New insights from spherical halo

core-halo decoupling I. Tanihata

, J. Phys. G 22, 157(1996) pairing anti-halo

K.

Bennaceur

et al., PLB 2000

continuum coupling

M. Yamagami

, PRC 72, 064308 (2005). shell quenching J. Dobaczewski

et al., PRL, 1994

BEC-BCS pairing K

. Hagino et al., PRL 99, 022506 (2007).Expected new insights from deformed halo/skin core-halo deformation decoupling: exotic structures neutron-proton

isovector

deformation:

isovector

quadrupole

modes

deformation of pairing densities:

?

by pair transfer experiments Mechanism of deformed halos: low Ω states with negative parity T. Misu, W. Nazarewicz, S. Aberg, NPA (1997) S.G. Zhou, PRC 82, 011301(R)(2010).

HFB solvers and Continuum effects-------J.C. Pei

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Continuum coupling in HFB

t

heory HFB solvers and Continuum effects-------J.C. Pei

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HFB

is superior to

BCS

for describing weakly-bound systems where continuum coupling becomes

essential

One visible difference: deep bound single-particle states become HFB resonances

HFB

G.S.:

BCS

G.S.:

The general HFB

equation

(or

BdG

)

Hartree-Fock-Bogoliubov

includes generalized quasi-particle correlations; while BCS is a

special

quasiparticle

transformation

only

on

conjugate states

.

JP et al. PRC, 2011Slide7

HFB

solving approaches

The difficulty: HFB resonances are embedded in the continuum

Coordinate-space HFB takes an unique opportunity for describing weakly-bound

systems and large deformations

HFB solvers and Continuum effects-------J.C. Pei

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Diagonalization on single-particle basis Direct diagonalization on coordinate-space latticeOutgoing boundary condition:

difficult for deformed cases※H. Oba, M. Matsuo, PRC, 2009,

made progress in deformed Green function HFB approach, but self-consistent calculations are still missing

The HO basis has a Gaussian form exp

(-ar

2

)

that decays too fast, while the density distribution decays exponentially

exp

(-

kr

).

Bound

states, continuum and embedded resonances are treated on an equal footing; L2 discretization leads to a very large configuration space Providing better inputs for QRPA, for describing excited states Computing resources and capabilities are increasing exponentiallySlide8

Deformed coordinate-space HFB

Development issues: very expensive, therefore parallel is essential

2D HFB based on B-splines, finite-difference method

3D MADNESS-HFB with Multi-wavelets

techniques and

sophisticated parallel techniques

HFB solvers and Continuum effects-------J.C. Pei

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V. E. Oberacker, A. S. Umar, E. Terán, and A. Blazkiewicz, PRC, 2003

J. P., M. V. Stoitsov, G. I. Fann, W. Nazarewicz, N. Schunck, and F. R. Xu, PRC, 2008 (

HFB-AX: Much faster and be able to calculate heavy nuclei and cold atoms

)H. Oba, M. Masto, Prog.Theor.Phys., 2008

J.P.,

G.I.

Fann

, R.J. Harrison, W.

Nazarewicz

, J. Hill, D. Galindo, J.

Jia

,

JPCS, 2012Slide9

Hybrid parallel

calculations

for large boxes HFB solvers and Continuum effects-------J.C. Pei

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MPI+OpenMP

(400 cores for one nucleus takes 1 hour)

Computing different blocks on different nodes (MPI)

Multi-thread computing within a node(

OpenMP

)

Works well in

Tianhe-1A

and Cray systems

J.P. et al., JPCS 402, 012035(2012)

Large boxes calculations are crucial for describing density diffuseness and discretized continuum

From 20

fm

to 30

fm

, the estimated computing cost increased by 40 times.Slide10

Deformations of

drip-line

nuclei Extensive studies on light drip-line nuclei Controversial about spherical halos in heavy nuclei, giant or collective halo?

HFB solvers and Continuum effects-------J.C. Pei

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J.

Erler

et al., Nature, 486, 509(2012)

N/Z=2.3Slide11

Systematics of deformed neutron

h

alo/skinNew exotic “egg”-like halo structureHalo hindered by deformed cores?

F.M. Nunes, NPA, 2005

HFB solvers and Continuum effects-------J.C. Pei

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J.C. Pei, Y.N. Zhang, F.R.

Xu

,

arXiv:1301.1461, 2013 Slide12

Development of resonances

in light nuclei

Levels near Fermi surface are sparse in light nucleiNear threshold quasiparticle

resonances (especially negative parity states) below 2 MeV are mainly responsible for the halo structures and surface deformations

No halo is obtained since pairing is missed in Mg40

HFB solvers and Continuum effects-------J.C. Pei

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Smoothed neutron

quasiparticle spectrum Ω=1/2Slide13

Development of resonances in heavy nuclei

Low-

halo resonances gradually grows and decouples in heavy nuclei

Bound states move away from the Fermi surface collectively;

larger level

density

D

ensity distribution decoupling is related to the phase space decoupling

  HFB solvers and Continuum effects-------J.C. Pei

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Isovector

deformations

Neutron skin/halo: pygmy dipole resonances (two humps)Isovector deformations: pygmy

quardpole resonances

HFB solvers and Continuum effects-------J.C. Pei

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From J.

Erler

et al., Nature, 486, 509(2012)Slide15

Development of surface deformations

S

lightly larger isovector deformations obtained, except for the egg-like structure

Deformation of pairing density are very sensitive to pairing Hamiltonian; non-resonant continuum plays an important role

HFB solvers and Continuum effects-------J.C. Pei

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Abnormal

isovector

deformation of 0.24 in theegg-like structure!Slide16

Continuum effects in excited states

It will be more interesting, however, it is not easy for

deformed nuclei. Finite-amplitude-method QRPA is a promising solution to avoid computing tremendously large QRPA matrix

HFB solvers and Continuum effects-------J.C. Pei

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In progress:

monopole strength calculated by FAM-QRPA with SLy4 and mixed pairingSlide17

Summary

Coordinate-space

HFB takes an unique opportunity for describing weakly bound nuclei in large boxes by using hybrid parallel computing.Deformed coordinate-space HFB is accurate not only for density diffuse structures but also for

continuum effects

New

exotic deformed halo structure of spherical core plus deformed halo is found

Surface deformations of pairing densities also shows decoupling effects

To be done:It will be interesting to

looking for continuum effects in excited states, such as Pygmy dipole and quardpole resonances based on deformed coordinate-space QRPA, and its in progress

HFB solvers and Continuum effects-------J.C. Pei-17-

C

ollaborators: F.R. Xu, Y.N. Zhang, W. NazarewiczSlide18

Thanks for your attention!

HFB solvers and Continuum effects-------J.C. Pei

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