4.2 The spectrum of small components
We prove an analogue of the Kublius fundamental lemma Kubilius, 1964 for quasi-logarithmic structures, and thus extend results of Arratia et al. 1995 and [ABT, Theorem 7.7]; see also the
corresponding result of Manstaviˇcius 2009, proved under different conditions.
Theorem 4.3. For a
n ≤ α , where
α is small enough that min
m ≥1
ǫ
′ 5
n, a, m ≤
1 2
p
θ
1, we have d
TV
L C
n
1
, . . . , C
n
a
, L Z
1
, . . . , Z
a
≤ ǫ
6
n, a , 4.7
where the order of magnitude of ǫ
6
n, a is given in 4.16 below. If QLC holds, then
lim
n →∞
d
TV
L C
n
1
, . . . , C
n
a
n
, L Z
1
, . . . , Z
a
n
= 0 for every non-negative integer sequence a
n
= on. If QLC2 holds, the convergence rate is of order {a + 1n}
η
5
for some η
5
0. Proof. The proof is similar to that of [ABT, Theorem 5.2]. We fix an n with the required properties,
and we set p
k
:= P[T
a,n
= k]. Then the conditioning relation entails d
TV
L C
n
1
, . . . , C
n
a
, L Z
1
, . . . , Z
a
=
n
X
k=1
P [T
0,a
= k] P
[T
0,n
= n] − p
n −k
+
P [T
0,n
= n] ≤
⌊n2⌋
X
k=0 ⌊n2⌋
X
l=0
P [T
0,a
= k]P[T
0,a
= l] p
n −l
− p
n −k
+
P [T
0,n
= n] +
⌊n2⌋
X
k=0 n
X
l= ⌊n2⌋+1
P [T
0,a
= k]P[T
0,a
= l] p
n −l
P [T
0,n
= n] +
n
X
k= ⌊n2⌋+1
P [T
0,a
= k] . 4.8
We now separately bound the three terms in 4.8. The first term is just
X
≤kl≤n2
P [T
0,a
= k]P[T
0,a
= l] p
n −l
− p
n −k
P [T
0,n
= n] .
4.9 Now, from Theorem 3.5, using the bound given in 3.25, we have
|np
n −r
− p
θ
1 − rn| ≤ ǫ
′ 5
n, a, m , ≤ r ≤ n2,
4.10 so that, in 4.9,
n |p
n −l
− p
n −k
| ≤ |p
θ
1 − ln − p
θ
1 − kn| + 2ǫ
′ 5
n, a, m ≤ c
1
θ n
−1
|k − l| + 2ǫ
′ 5
n, a, m, for any choice of m and for some constant c
1
θ . Since also, from Theorem 3.5, nP[T
0,n
= n] is uniformly bounded below whenever
ǫ
′ 5
n, a, m ≤
1 2
p
θ
1, it follows that the first term in 4.8 is of order
O n
−1
E T
0,a
+ min
m ≥1
ǫ
′ 5
n, a, m = O n
−1
a + min
m ≥1
ǫ
′ 5
n, a, m .
4.11 896
For the second term in 4.8, we have two bounds. First,
n
X
l= ⌊n2⌋+1
P [T
0,a
= l] P
[T
a,n
= n − l] P
[T
0,n
= n] ≤
n max
n 2≤l≤n
P [T
0,a
= l] nP[T
0,n
= n] ,
where the denominator is uniformly bounded below whenever ǫ
′ 5
n, a, m ≤
1 2
p
θ
1, and, for n2 ≤ l
≤ n and a ≤ n4, nP[T
0,a
= l] ≤ 2lP[T
0,a
= l] ≤ 2θ
∗
P [T
0,a
≥ n4] + 2ǫ
2
a, 0, m ≤ 8θ
∗ 2
an + 2ǫ
2
a, 0, m , 4.12
from 3.15, with the last step following because ET
0,a
≤ aθ
∗
. The second bound is given by
n
X
l= ⌊n2⌋+1
P [T
0,a
= l] P
[T
a,n
= n − l] P
[T
0,n
= n] ≤ P[T
0,a
≥ n2] sup
j ∈Z
+
P [T
a,n
= j] P
[T
0,n
= n] ≤
2a θ
∗
D
1
T
a,n
nP[T
0,n
= n] ,
4.13
again using Markov’s inequality, and the asymptotically important part is aD
1
T
a,n
. Thus the second term in 4.8 is of order
O n
−1
a + min {min
m ≥1
ǫ
2
a, 0, m, aD
1
T
a,n
} .
4.14 Finally, the third term in 4.8 can be simply bounded from above by
2n
−1
E T
0,a
≤ 2θ
∗
n
−1
a . 4.15
Combining 4.11, 4.14 and 4.15 proves the first part of the theorem, with ǫ
6
n, a = O n
−1
a + min
m ≥1
ǫ
′ 5
n, a, m + min{min
m ≥1
ǫ
2
a, 0, m, aD
1
T
a,n
} .
4.16 The remaining statements follow as usual.
4.3 Additive arithmetic semigroups
Kategori