regular and chaotic nuclear vibrations ( m onodromy, bifurcations, regular islands…)
DESCRIPTION
Regular and chaotic nuclear vibrations ( m onodromy, bifurcations, regular islands…). Pavel Cejnar , Michal Macek, Pavel Str ánský, Matúš Kurian Institute of Particle & Nuclear Physics, Charles University, Prague, Czech Rep. Thanks to: J. Jolie, S. Heinze (K öln ), R. Casten (Yale), - PowerPoint PPT PresentationTRANSCRIPT
Regular andRegular and chaotic chaotic nuclearnuclear vibrationsvibrations
((mmonodromy, bifurcations, regular islands…)onodromy, bifurcations, regular islands…)
Pavel CejnarPavel Cejnar, Michal Macek, , Michal Macek, Pavel StrPavel Stránský, Matúš Kurianánský, Matúš Kurian
Institute of Particle & Nuclear Physics, Charles University, Prague, Czech Rep.
CGS12, Notre Dame, 2005 A.D.
Thanks to: J. Jolie, S. HeinzeJ. Jolie, S. Heinze (Köln), R. CastenR. Casten (Yale),
J. DobeJ. Dobešš, Z. Pluha, Z. Pluhařř (Prague).
classical ↔ quantum correspondence level density spectral correlations
• bunching/antibunching of levels (Gutzwiller, Berry-Tabor formulas) • long-range correlations…
trajectories in the phase space of quadrupole deformation parameters visual insight into essential dynamical features
Classical limit ! Why classical ?
description of nuclear collective degrees of freedom (vibrations, rotations)
connected with quadrupole deformations
►
►
Geometric Collective Model (GCM)
Interacting Boson Model (IBM)
classical ↔ quantum correspondence level density spectral correlations
• bunching/antibunching of levels (Gutzwiller, Berry-Tabor formulas) • long-range correlations…
trajectories in the phase space of quadrupole deformation parameters visual insight into essential dynamical features
Classical limit ! Why classical ?
description of nuclear collective degrees of freedom (vibrations, rotations)
connected with quadrupole deformations
►
►
Geometric Collective Model (GCM)
Interacting Boson Model (IBM)
y
x
classical ↔ quantum correspondence level density spectral correlations
• bunching/antibunching of levels (Gutzwiller, Berry-Tabor formulas) • long-range correlations…
trajectories in the phase space of quadrupole deformation parameters visual insight into essential dynamical features
Classical limit ! Why classical ?
description of nuclear collective degrees of freedom (vibrations, rotations)
connected with quadrupole deformations
►
►
Geometric Collective Model (GCM)
Interacting Boson Model (IBM)
E
η
y
x
Order / chaos defined most transparently on the classical level
Important issue in nuclear physics – nuclear motions exhibit an interplay of regular and chaotic components even at low energies. What is the principal source of chaos?
• Lyapunov exponets (sensitivity of motions to initial conditions)• Poincaré sections (organization of trajectories in the phase space)
regular chaotic
IBM: η=0.4, χ=-0.99 (“arc of regularity”) η=0.4, χ=-0.77 min114
min )2( VVVE
(plane y=0 in the phase space: 30 000 passages of 120 trajectories)
GCM classical Hamiltonian
.....][5][2
35][5.....][
2
5 2)2()0()2()0()0( CBAK
H
…corresponding tensor of momenta
neglect higher-order terms neglect …
A
B
spherical
oblate
prolate
quadrupole tensor of collective coordinates (2 shape param’s, 3 Euler angles )
GCM classical Hamiltonian
.....][5][2
35][5.....][
25 2)2()0()2()0()0( CBAK
H
222232222 )()3()()(2
1yxCxyxByxA
KH yx
432 3cos CBAV
)3(3
1)(
2
1)( 232222 xyxyxH yx
quadrupole tensor of collective coordinates (2 shape param’s, 3 Euler angles )
…corresponding tensor of momenta
With angular momentum
neglect higher-order terms neglect …
)1(*][10 iJ = 0
For comparison: Hénon-Heiles Hamiltonian
motion in principal coordinate frame
sinRe2
cosRe
2
y
x
A
B
2D system
... an archetypal system with competing regular and chaotic features
_________________________________________________
oblate
prolate
spherical
A=1, B=1.09, C=1
Hénon-Heiles system
exhibits rather smooth
energy dependence
of chaotic measures.
Not so the GCM...
E
completely regular
completely chaotic
transitional
Motions near the potential minimum are always regular (oscillator approximation).
At some “critical” energy chaos sets in. This happens approx. when the boundary
of the accessible area in the x × y plane becomes partly concave:
convex
concave
Low energy
Regular fraction
B=C=1
A variable
of the Poincaré section
tot
regreg S
Sf
(similar to reg. fraction
of entire phase space)
E
IBM classical limit
Method by Hatch, Levit [PRC 25, 614 (1982)] Alhassid, Whelan [PRC 43, 2637 (1991)]___________________________________________________________
● use of Glauber coherent states
HH cl
● classical Hamiltonian
22s ||||NN
● boson number conservation (only in average)
complex variables contain coordinates & momenta
● classical limit:
ipq
N)(
21
2
qp
N
fixed 10 real variables:
(2 quadrupole deformation
parameters, 3 Euler angles,
5 associated momenta)
0)exp( s|| 2
21
dse
● angular momentum J=0 Euler angles irrelevant only 4D phase space
(12 real variables)
2 coordinates (x,y) or (β,γ)
restricted phase-space domain
)()(
1),(
2d QQN
nN
H
ddn~
d
)2(]~
[~
)( dddssdQ
Consistent-Q Hamiltonian
d-boson number operator
quadrupole operator
mean field interactions
scaling constant ħω=1 MeV
control parameters η, χ
SU(3)
O(6) U(5)
χ
η0 10
-√7 ⁄ 2
symmetry triangle
deformed
spherical
Measures of chaos (Lyapunov exponents)
inside the triangle:
Alhassid et al. [e.g. NP A556, 42 (1993)]
SU(3)
O(6) U(5)
η=½, χ=0
η=½, χ=- 0.68
η=½, χ=- 0.46
η=½, χ=- 0.91
η=½, χ=- 0.23
η=½, χ=-1.16
pβ
β
“arc of regularity”
IBM Poincaré sections
across the triangle
(J=0, E=0)
SU(3)
O(6) U(5)
η=½, χ=0
η=½, χ=- 0.68
η=½, χ=- 0.46
η=½, χ=- 0.91
η=½, χ=- 0.23
η=½, χ=-1.16
pβ
β
“arc of regularity”
IBM Poincaré sections
across the triangle
(J=0, E=0)
More info:• CGS12 poster: M. Macek, P. Cejnar
• http://www-ucjf.troja.mff.cuni.cz/~geometric/
O(6)-U(5) transition (χ=0)η=0.6
42222 )1(2
45)1(
2 H
kinetic energy Tcl potential energy Vcl
2
2222
yx
222 yx
J=0
… the system is integrable !
2 compatible integrals of motions: • energy• J=0 projected O(5) “angular momentum”
xy yx
2clas.limit335
12 2)(2)()5(O TTJJC
0
T
TR
Classification of trajectories
by the ratio
of periods associated with
oscillations in β and γ
directions. For rational
the trajectory is periodic:
R
R
E
E=0
Spectrum of orbits(obtained in a numerical simulation
involving ≈ 50000 randomly selected
trajectories)
η=0.6
R
E
E=0
Spectrum of orbits(obtained in a numerical simulation
involving ≈ 50000 randomly selected
trajectories)
η=0.6
The mechanism responsible
for narrowing of the band:
inverse bifurcations
(2 separate branches of orbit
with the same R “annihilate”)
R
E
R>3
“flower-like orbits”
(Mexican-hat potential)
R≈2
“bouncing-ball orbits” (like in spherical oscillator)
E=0
Spectrum of orbits(obtained in a numerical simulation
involving ≈ 50000 randomly selected
trajectories)
η=0.6
At E=0 the motions change their
character from O(6)- to U(5)-like
type of trajectories
O(6) transitional U(5)
→seniority
ener
gy
Lattice of J=0 states(energy vs. seniority)
N=40
What about the
quantum case ?
U(5) limit
Analogy with standard isotropic
2D harmonic oscillator:
_________________________n1=nrad+v/3
n2=nrad+2v/32212
21 H
radial quantum number nrad
principal quantum number N=2nrad+m
angular-momentum quantum number m0 2 341
0
01
1
2
2
3
3
4
4… yes, but only for nd=3k
differences between the O(2) and J=0 projected O(5) angular momenta
*
*
O(5) quantum number: seniority v
O(6) quantum number: σ
O(6) limit
422422 H
Transitional case
O(6)-like
type of cells
U(5)-like
type of cells
Redistribution of levels
between O(6) and U(5)
multiplets
E=0
Transitional case
O(6)-like
type of cells
U(5)-like
type of cells
Μονοδρoμια
(monodromy)Singular bundle of E=v=0
orbits connected with the
unstable equilibrium at β=0
Redistribution of levels
between O(6) and U(5)
multiplets
E=0
E=0
J=0 level dynamics across the O(6)-U(5) transition
N=40
(all v’s)
E=0
U(5)-like
O(6)-like
N=40
most probably a real
phase transitioninvolving excited states
(nonzero temperatures)
J=0 level dynamics across the O(6)-U(5) transition
PhysicPhysicumum
Magia Magia MaximaMaxima
Conclusions:
IBM & GCM hide extremely rich variety
of behaviors. Here we discussed:
• nontrivial dependence of chaos on energy & control parameters (unexpected islands of regularity)
• emergence / decay of various types of regular orbits (consequences for level bunching patterns)
• abrupt changes of dynamics with energy & control parameters (signatures of structural phase transitions)
More info:• CGS12 poster: M. Macek, P. Cejnar• http://www-ucjf.troja.mff.cuni.cz/~geometric/• nucl-th/0504016, nucl-th/0504017 (to be published)
GC
M: A
=-1
, B=
0.6
2, C
=K
=1
, E=
3.6
*
*
“…it’s kin
d o
f magic!”
APPENDICES
B=C=K=1
A= -1, C=K=1
E=0A= -1/B2
Scaling properties of the classical GCM
ttt
b
hHHH
~
~
~
432222 3cos21 CBAβK
H
4 parameters – 3 scaling constants = 1 essential parameter
2BAC
R
Relevant combination
of parameters
A=-0.842
A=0
A=0.25 (phase transition)
A=-5.05
Energy dependence of freg
Dependence of Freg on angular momentum
Regular fraction of the
available phase-space volume
),(max BEJJ
j
Phase-transitional region
421
1,,3
2
1fluct cos
rESrgr
TE
r E
Berry-Tabor trace formula(an analog of the Gutzwiller formula, but for 2D integrable systems)
Efluct
T
IES 2
21,
2
1
2
1
… fluctuating part of level density
…pair of integers characterizing periodic orbit with
ratio of frequencies
…period of the primitive orbit
r…number of repetitions
…action per period
1IgE 2
1,21,
EE gEgIIH…function defined by
…Maslov index of the primitive orbit
Bifurcations
Monodromy
The simplest example: spherical pendulum
Discovered: Duistermaat (1980)
Elaborated: Cushman, Bates: Global Aspects of Classical Integrable
Systems (1997)
unstable equilibrium
Figures taken from:
Other examples of monodromy:• Mexican-hat (Champagne bottle) potentials• two-center potentials• coupled rotators• hydrogen in orthogonal E/M fields• ……………