[SeqFan] final : summary on "charged necklaces"
Wouter Meeussen
w.meeussen.vdmcc at vandemoortele.be
Thu Aug 13 17:51:27 CEST 1998
since I sent mail while the issue was still foggy in my head, I would like
to close my interventions on the subject with a clean summary.
to Neil J.A. Sloane : I'll format them & send 'm in, and signal where my
descriptions sofar might have been misleading or plain wrong (:-(
It turns out to be necessary to distinguish between counting "equivalent
states under given symmetry operations" and "counting energy levels".
This difference is what I called "accidental degeneracies" in analogy with
Quantum Theory usage.
**** the summary ****
L I N E (string)
I found for n positive and n negative "charges" on a line : (not in EIS)
n levels states (k1*d1+k2*d2+...)
1 1 1 1*1
2 3 3 3*1
3 7 10 4*1+3*2
4 23 35 11*1+12*2
5 71 126 16*1+55*2
6 252 462 42*1+210*2
7 890 1716 64*1+826*2
8 3299 6435 163*1+3136*2
9**** 12274 24310 256*1+12009*2+9*4
for the permutations of n "1" s and n "-1" s on a line,
with sign change and reversal :
(already in EIS, correct as it stands)
n levels states degen=1 degen=2
1 1 1 1 0
2 3 3 3 0
3 7 10 4 3
4 23 35 11 12
5 71 126 16 55
6 252 462 42 210
7 890 1716 64 826
8 3299 6435 163 3136
9**** 12283 24310 256 12027
10 46508 92378 638 45870
states = Binomial[2n,n]/2
degen1 = Table[2^(n) +Mod[n,2]Binomial[ n,n/2-1/2],{n,0,10}]
degen2 = (Table[Binomial[2n,n]/2 -(2^(n-1)
+Mod[n+1,2]Binomial[n-1,n/2-1]),{n,10}])/2
Difference is caused by the last bin for n=9:
I found nine pairs of "accidental degeneracies"
These states are in no way symmetric, but give the same energy levels
on the adjacency matrix.
This causes the last bin of "18*2" to be a contraction of "9*4",
changing the nr of levels to be 12274 in stead of 12283.
acci1
{-1,-1,-1,-1,1,1,1,1,1,1,-1,-1,1,-1,1,-1,-1,1}
{-1,-1,1,1,1,1,1,1,-1,-1,-1,-1,1,-1,-1,1,-1,1}
acci2
{-1,-1,1,-1,-1,1,1,1,-1,1,1,-1,1,1,-1,-1,-1,1}
{-1,-1,1,1,1,-1,1,1,-1,1,1,-1,-1,-1,1,-1,-1,1}
acci3
{-1,-1,1,1,1,-1,-1,-1,1,1,1,-1,1,1,-1,-1,-1,1}
{-1,-1,1,1,1,-1,1,1,-1,-1,-1,1,1,1,-1,-1,-1,1}
acci4
{-1,1,-1,-1,1,-1,1,-1,1,1,1,-1,1,1,-1,-1,-1,1}
{-1,1,-1,1,-1,1,1,-1,1,1,1,-1,-1,-1,1,-1,-1,1}
acci5
{-1,1,-1,1,1,-1,-1,1,-1,1,1,-1,1,-1,1,-1,-1,1}
{-1,1,-1,1,1,-1,1,-1,1,-1,-1,1,1,-1,1,-1,-1,1}
acci6
{-1,-1,1,-1,-1,1,1,1,-1,1,1,-1,-1,-1,1,1,1,-1}
{-1,-1,1,1,1,-1,-1,-1,1,-1,-1,1,1,1,-1,1,1,-1}
acci7
{-1,-1,-1,-1,1,1,1,1,1,1,-1,-1,-1,1,-1,1,1,-1}
{-1,-1,1,1,1,1,1,1,-1,-1,-1,-1,-1,1,1,-1,1,-1}
acci8
{-1,-1,1,-1,-1,1,1,1,-1,1,-1,1,1,-1,1,-1,1,-1}
{-1,-1,1,1,1,-1,1,1,-1,1,-1,1,-1,1,-1,-1,1,-1}
acci9
{-1,-1,1,1,-1,1,-1,-1,1,1,-1,1,1,1,-1,-1,1,-1}
{-1,-1,1,1,-1,1,1,1,-1,-1,1,-1,1,1,-1,-1,1,-1}
R I N G S (necklaces)
number of energy levels of n positive and n negative charges equally spaced
on a ring (already in EIS, description MUST refer to charges & energy-levels)
(count k of E-levels with degeneracy d)
n levels states (k1*d1+k2*d2+...)
1 1 1 1*1
2 2 3 1*1+1*2
3 3 10 1*1+1*3+1*6
4 7 35 1*1+1*2+2*4+3*8
5 13 126 1*1+3*5+7*10+2*20
6 35 462 1*1+1*2+1*3+4*6+20*12+8*24
7 85 1716 1*1+7*7+35*14+42*28
8**** 254 6435 1*1+1*2+2*4+11*8+88*16+148*32+3*64
9 701 24310 1*1+1*3+1*6+14*9+136*18+488*36+9*54+51*72
10 2337 92378 1*1+1*2+3*5+22*10+362*20+1855*40+1*60+130*80+2*120
for the permutations of n 1's and n -1's on a ring,
rotation, sign change and reversal turn out as
n # distinct states count*degeneracy
1 1 1 1*1
2 2 6 1*2+1*4
3 3 20 1*2+1*6+1*12
4 7 70 1*2+1*4+2*8+3*16
5 13 252 1*2+3*10+7*20+2*40
6 35 924 1*2+1*4+1*6+4*12+20*24+8*48
7 85 3432 1*2+7*14+35*28+42*56
8**** 257 12870 1*2+1*4+2*8+11*16+88*32+154*64
This is (most likely) :
%I A006840 M0837
%S A006840 1,2,3,7,13,35,85,257,765,2518
%N A006840 Binary sequences of period 2n with n 1's per period.
%R A006840 JAuMS A33 14 1982. CN 40 89 1983.
%O A006840 1,2
%A A006840 njas
%K A006840 nonn
The difference is caused by the last bin for n=8:
I found three pairs of "accidental degeneracies"
These states are in no way symmetric, but give the same energy levels
on the adjacency matrix.
This causes the last bin of "3*64" to be a contraction of "6*32",
changing the nr of levels to be 254 in stead of 257.
acci1=
{-1,-1,-1,-1,1,-1,1,1,-1,1,1,-1,-1,1,1,1}
{-1,-1,-1,-1,1,1,-1,1,-1,-1,1,1,1,-1,1,1}
acci2=
{-1,-1,-1,-1,-1,1,1,-1,1,-1,1,1,-1,1,1,1}}
{-1,-1,-1,-1,1,-1,1,1,-1,-1,1,1,1,1,-1,1}}
acci3=
{-1,-1,-1,1,-1,-1,1,1,-1,1,-1,1,-1,1,1,1}}
{-1,-1,-1,1,-1,1,-1,1,1,-1,-1,1,1,1,-1,1}}
WITHOUT REVERSALS: (turning necklace over)
symmetry conditions of necklace, n "1"'s and n "0"'s,
with rotation but no reversals,
but with (1) <--> (0) exchange as symmetry operation
new to EIS : 1,2,3,7,15,44,128,415,1367
n # distinct tot count*degeneracy
1 1 2 1*2
2 2 6 1*2+1*4
3 3 20 1*2+1*6+1*12
4 7 70 1*2+1*4+2*8+3*16
5 15 252 1*2+3*10+11*20
6 44 924 1*2+1*4+1*6+6*12+35*24
7 128 3432 1*2+9*14+118*28
8 415 12870 1*2+1*4+2*8+19*16+392*32
9 1367 48620 1*2+1*6+1*12+28*18+1336*36
TWO NECKLACES
two facing necklaces, one above the other, each n positive and n negative
charges.
Count the number of energy levels (inter, not intra).
new to EIS : 2,5,18,71,538
n E levs states (level_count*degeneracy+...)
1 2 4 {{2,2}}
2 5 36 {{2,2},{2,4},{1,24}}
3 18 400 {{2,2},{2,6},{4,12},{4,24},{4,36},{2,48}}
4 71 4900
{{2,2},{2,4},{4,8},{14,16},{12,32},{4,48},{18,64},{2,96},{8,128},{2,160},{2,
320},{1,728}}
5 538 63504
{{2,2},{6,10},{34,20},{92,40},{8,60},{268,80},{2,100},{4,120},{56,160},{4,24
0},{16,280},{16,320},{4,380},{2,400},{2,440},{12,480},{4,640},{4,720},{2,1280}}
wouter.
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Oils & Fats Applied Research
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