File size: 13,430 Bytes
b317718
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
import OAI.Probability.FreeIsing.Estimates.ProgressivePrimitiveFubini
import OAI.Probability.FreeIsing.Estimates.SharedInnovationBounds
import OAI.Probability.FreeIsing.Posterior.FieldMoments
import OAI.Probability.FreeIsing.Posterior.ProgressiveIsingPosterior

namespace OAI

noncomputable section

open MeasureTheory ProbabilityTheory Set
open scoped NNReal

namespace Problem367

open PlantedSymmetry

theorem ae_observation_sub_bound_of_shared_progressive_innovation
    {Ω : Type*} [mΩ : MeasurableSpace Ω] {P : Measure Ω} [IsFiniteMeasure P]
    {F G : Filtration ℝ≥0 mΩ} {m m' : ℝ≥0 → Ω → ℝ}
    (hm : IsStronglyProgressive F m) (hm' : IsStronglyProgressive G m')
    (hb : ∀ t, ∀ᵐ ω ∂P, |m t ω| ≤ 1)
    (hb' : ∀ t, ∀ᵐ ω ∂P, |m' t ω| ≤ 1)
    {x x' w : Ω → ℝ} (t : ℝ≥0)
    (hx : ∀ᵐ ω ∂P, x ω = w ω + nnrealTimePrimitive m t ω)
    (hx' : ∀ᵐ ω ∂P, x' ω = w ω + nnrealTimePrimitive m' t ω) :
    ∀ᵐ ω ∂P, |x ω - x' ω| ≤ 2 * (t : ℝ) := by
  have hL := ae_lipschitzWith_nnrealTimePrimitive hm (C := 1) hb
  have hL' := ae_lipschitzWith_nnrealTimePrimitive hm' (C := 1) hb'
  filter_upwards [hL, hL', hx, hx'] with ω hω hω' hxω hxω'
  have h1 : |nnrealTimePrimitive m t ω| ≤ (t : ℝ) := by
    simpa only [Real.dist_eq, nnrealTimePrimitive, NNReal.coe_zero,
      intervalIntegral.integral_same, sub_zero, NNReal.coe_one, one_mul,
      NNReal.dist_eq, abs_of_nonneg t.coe_nonneg] using hω.dist_le_mul t 0
  have h2 : |nnrealTimePrimitive m' t ω| ≤ (t : ℝ) := by
    simpa only [Real.dist_eq, nnrealTimePrimitive, NNReal.coe_zero,
      intervalIntegral.integral_same, sub_zero, NNReal.coe_one, one_mul,
      NNReal.dist_eq, abs_of_nonneg t.coe_nonneg] using hω'.dist_le_mul t 0
  rw [hxω, hxω']
  have heq : (w ω + nnrealTimePrimitive m t ω) -
      (w ω + nnrealTimePrimitive m' t ω) =
      nnrealTimePrimitive m t ω - nnrealTimePrimitive m' t ω := by ring
  rw [heq]
  exact (abs_sub _ _).trans (by linarith)

theorem HasFreeIsingLaw.gaussianPosteriorField_copy_bound
    {Ω : Type*} [mΩ : MeasurableSpace Ω] {P : Measure Ω} [IsProbabilityMeasure P]
    {d : ℕ} {beta : ℝ} {μ : Measure (TreeVertex d → IsingSpin)}
    (hμ : HasFreeIsingLaw (Real.tanh beta) μ) (hbeta : 0 ≤ beta)
    (t : ℝ≥0) (v : TreeVertex d)
    {q q' : Ω → (TreeVertex d → IsingSpin) × (TreeVertex d → ℝ)}
    (hq : MeasurePreserving q P (μ.prod (gaussianNoiseLaw (TreeVertex d) t)))
    (hq' : MeasurePreserving q' P (μ.prod (gaussianNoiseLaw (TreeVertex d) t)))
    {F G : Filtration ℝ≥0 mΩ} {m m' : ℝ≥0 → Ω → ℝ}
    (hm : IsStronglyProgressive F m) (hm' : IsStronglyProgressive G m')
    (hb : ∀ s, ∀ᵐ ω ∂P, |m s ω| ≤ 1)
    (hb' : ∀ s, ∀ᵐ ω ∂P, |m' s ω| ≤ 1)
    {w : Ω → ℝ}
    (hx : ∀ᵐ ω ∂P, observation t (q ω) v = w ω + nnrealTimePrimitive m t ω)
    (hx' : ∀ᵐ ω ∂P, observation t (q' ω) v = w ω + nnrealTimePrimitive m' t ω) :
    ∀ᵐ ω ∂P, |gaussianPosteriorField μ t v (q ω) -
      gaussianPosteriorField μ t v (q' ω)| ≤ 2 * (t : ℝ) + 2 * (d : ℝ) * beta := by
  have hobs := ae_observation_sub_bound_of_shared_progressive_innovation
    hm hm' hb hb' t hx hx'
  have hfield := hμ.gaussian_posterior_field_bound hbeta t v
  have hleft := hq.quasiMeasurePreserving.ae hfield
  have hright := hq'.quasiMeasurePreserving.ae hfield
  filter_upwards [hobs, hleft, hright] with ω hobsω hl hr
  have hlb := hl.2
  have hrb := hr.2
  change |gaussianPosteriorField μ t v (q ω) - observation t (q ω) v| ≤
    (d : ℝ) * beta at hlb
  change |gaussianPosteriorField μ t v (q' ω) - observation t (q' ω) v| ≤
    (d : ℝ) * beta at hrb
  have htriangle := abs_sub_le (gaussianPosteriorField μ t v (q ω))
    (observation t (q ω) v) (gaussianPosteriorField μ t v (q' ω))
  have htriangle' := abs_sub_le (observation t (q ω) v)
    (observation t (q' ω) v) (gaussianPosteriorField μ t v (q' ω))
  rw [abs_sub_comm (observation t (q' ω) v)] at htriangle'
  linarith

theorem HasFreeIsingLaw.gibbsField_bound_of_observation_identDistrib
    {Ω : Type*} [MeasurableSpace Ω] {P : Measure Ω}
    {d : ℕ} {beta : ℝ} {μ : Measure (TreeVertex d → IsingSpin)}
    (hμ : HasFreeIsingLaw (Real.tanh beta) μ) (hbeta : 0 ≤ beta)
    (t : ℝ≥0) (v : TreeVertex d) {X : Ω → TreeVertex d → ℝ}
    (hX : IdentDistrib X (observation t) P
      (μ.prod (gaussianNoiseLaw (TreeVertex d) t))) :
    ∀ᵐ ω ∂P, |Real.artanh (infiniteGibbsSpinMean beta v (X ω)) - X ω v| ≤
      (d : ℝ) * beta := by
  have ha : Measurable Real.artanh := by unfold Real.artanh; fun_prop
  have hmeas := (ha.comp (measurable_infiniteGibbsSpinMean beta v)).sub
    (measurable_pi_apply v)
  apply hX.symm.ae_snd (measurableSet_le hmeas.abs measurable_const)
  filter_upwards [hμ.infiniteGibbsSpinMean_eq_posterior t v,
    hμ.gaussian_posterior_field_bound hbeta t v] with p heq hp
  simp only [Pi.sub_apply, Function.comp_apply]
  rw [heq]
  exact hp.2

theorem HasFreeIsingLaw.gibbsField_copy_bound_of_shared_innovation
    {Ω : Type*} [mΩ : MeasurableSpace Ω] {P : Measure Ω} [IsFiniteMeasure P]
    {d : ℕ} {beta : ℝ} {μ : Measure (TreeVertex d → IsingSpin)}
    (hμ : HasFreeIsingLaw (Real.tanh beta) μ) (hbeta : 0 ≤ beta)
    {F G : Filtration ℝ≥0 mΩ}
    {X X' : TreeVertex d → ℝ≥0 → Ω → ℝ}
    (hX : ∀ i, IsStronglyProgressive F (X i))
    (hX' : ∀ i, IsStronglyProgressive G (X' i))
    (t : ℝ≥0) (v : TreeVertex d)
    (hlaw : IdentDistrib (fun ω i => X i t ω) (observation t) P
      (μ.prod (gaussianNoiseLaw (TreeVertex d) t)))
    (hlaw' : IdentDistrib (fun ω i => X' i t ω) (observation t) P
      (μ.prod (gaussianNoiseLaw (TreeVertex d) t)))
    {w : Ω → ℝ}
    (hx : ∀ᵐ ω ∂P, X v t ω = w ω + nnrealTimePrimitive
      (fun s p => infiniteGibbsSpinMean beta v (fun i => X i s p)) t ω)
    (hx' : ∀ᵐ ω ∂P, X' v t ω = w ω + nnrealTimePrimitive
      (fun s p => infiniteGibbsSpinMean beta v (fun i => X' i s p)) t ω) :
    ∀ᵐ ω ∂P,
      |Real.artanh (infiniteGibbsSpinMean beta v (fun i => X i t ω)) -
        Real.artanh (infiniteGibbsSpinMean beta v (fun i => X' i t ω))| ≤
          2 * (t : ℝ) + 2 * (d : ℝ) * beta := by
  have hm := isStronglyProgressive_infiniteGibbsSpinMean F beta v X hX
  have hm' := isStronglyProgressive_infiniteGibbsSpinMean G beta v X' hX'
  have hobs := ae_observation_sub_bound_of_shared_progressive_innovation hm hm'
    (fun s => Filter.Eventually.of_forall
      (fun p => infiniteGibbsSpinMean_abs_le_one beta v _))
    (fun s => Filter.Eventually.of_forall
      (fun p => infiniteGibbsSpinMean_abs_le_one beta v _)) t hx hx'
  have hl := hμ.gibbsField_bound_of_observation_identDistrib hbeta t v hlaw
  have hr := hμ.gibbsField_bound_of_observation_identDistrib hbeta t v hlaw'
  filter_upwards [hobs, hl, hr] with ω hobsω hlω hrω
  have htriangle := abs_sub_le
    (Real.artanh (infiniteGibbsSpinMean beta v (fun i => X i t ω)))
    (X v t ω)
    (Real.artanh (infiniteGibbsSpinMean beta v (fun i => X' i t ω)))
  have htriangle' := abs_sub_le (X v t ω) (X' v t ω)
    (Real.artanh (infiniteGibbsSpinMean beta v (fun i => X' i t ω)))
  rw [abs_sub_comm (X' v t ω)] at htriangle'
  linarith

theorem HasFreeIsingLaw.gibbsField_copy_secondMoment_bounds
    {Ω : Type*} [mΩ : MeasurableSpace Ω] {P : Measure Ω} [IsProbabilityMeasure P]
    {d : ℕ} {beta : ℝ} {μ : Measure (TreeVertex d → IsingSpin)}
    (hμ : HasFreeIsingLaw (Real.tanh beta) μ) (hbeta : 0 ≤ beta)
    {F G : Filtration ℝ≥0 mΩ}
    {X X' : TreeVertex d → ℝ≥0 → Ω → ℝ}
    (hX : ∀ i, IsStronglyProgressive F (X i))
    (hX' : ∀ i, IsStronglyProgressive G (X' i))
    (t : ℝ≥0) (v : TreeVertex d)
    (hlaw : IdentDistrib (fun ω i => X i t ω) (observation t) P
      (μ.prod (gaussianNoiseLaw (TreeVertex d) t)))
    (hlaw' : IdentDistrib (fun ω i => X' i t ω) (observation t) P
      (μ.prod (gaussianNoiseLaw (TreeVertex d) t)))
    {w : Ω → ℝ}
    (hx : ∀ᵐ ω ∂P, X v t ω = w ω + nnrealTimePrimitive
      (fun s p => infiniteGibbsSpinMean beta v (fun i => X i s p)) t ω)
    (hx' : ∀ᵐ ω ∂P, X' v t ω = w ω + nnrealTimePrimitive
      (fun s p => infiniteGibbsSpinMean beta v (fun i => X' i s p)) t ω) :
    let U := fun ω =>
      Real.artanh (infiniteGibbsSpinMean beta v (fun i => X i t ω)) -
        Real.artanh (infiniteGibbsSpinMean beta v (fun i => X' i t ω))
    MemLp U 2 P ∧ 0 ≤ (∫ ω, (U ω) ^ 2 ∂P) ∧
      (∫ ω, (U ω) ^ 2 ∂P) ≤ (2 * (t : ℝ) + 2 * (d : ℝ) * beta) ^ 2 := by
  dsimp only
  have hb := hμ.gibbsField_copy_bound_of_shared_innovation hbeta hX hX'
    t v hlaw hlaw' hx hx'
  have ha : Measurable Real.artanh := by unfold Real.artanh; fun_prop
  have hm := isStronglyProgressive_infiniteGibbsSpinMean F beta v X hX
  have hm' := isStronglyProgressive_infiniteGibbsSpinMean G beta v X' hX'
  have hmeas := (ha.comp (((hm.stronglyAdapted t).mono (F.le t)).measurable)).sub
    (ha.comp (((hm'.stronglyAdapted t).mono (G.le t)).measurable))
  exact discrepancy_secondMoment_bounds hmeas.aestronglyMeasurable hb

theorem progressive_memLp_two_on_horizon
    {Ω : Type*} [mΩ : MeasurableSpace Ω] {P : Measure Ω} [IsFiniteMeasure P]
    {F : Filtration ℝ≥0 mΩ} {U : ℝ≥0 → Ω → ℝ}
    (hU : IsStronglyProgressive F U) (T : ℝ≥0) (C : ℝ)
    (hb : ∀ t ≤ T, ∀ᵐ ω ∂P, |U t ω| ≤ C) :
    (∀ᵐ p ∂(volume.restrict (Ioc (0 : ℝ) (T : ℝ))).prod P,
      |U p.1.toNNReal p.2| ≤ C) ∧
    MemLp (fun p : ℝ × Ω => U p.1.toNNReal p.2) 2
      ((volume.restrict (Ioc (0 : ℝ) (T : ℝ))).prod P) := by
  let ν : Measure ℝ := volume.restrict (Ioc 0 (T : ℝ))
  have hclip : StronglyMeasurable (fun p : ℝ × Ω => U (min p.1.toNNReal T) p.2) :=
    (stronglyMeasurable_clipped_nnreal_process hU T).mono
      (sup_le_sup le_rfl (MeasurableSpace.comap_mono (F.le T)))
  have hbc : ∀ᵐ p ∂ν.prod P, |U (min p.1.toNNReal T) p.2| ≤ C := by
    apply (Measure.ae_prod_iff_ae_ae
      (measurableSet_le hclip.measurable.abs measurable_const)).2
    exact Filter.Eventually.of_forall fun r => hb _ (min_le_right r.toNNReal T)
  have hc : MemLp (fun p : ℝ × Ω => U (min p.1.toNNReal T) p.2) 2 (ν.prod P) :=
    MemLp.of_bound hclip.aestronglyMeasurable C
      (by simpa only [Real.norm_eq_abs] using hbc)
  have heq : (fun p : ℝ × Ω => U (min p.1.toNNReal T) p.2) =ᵐ[ν.prod P]
      (fun p => U p.1.toNNReal p.2) := by
    have hmem : ∀ᵐ p ∂ν.prod P, p.1 ∈ Ioc (0 : ℝ) (T : ℝ) :=
      Measure.quasiMeasurePreserving_fst.ae (ae_restrict_mem measurableSet_Ioc)
    filter_upwards [hmem] with p hp
    have ht : p.1.toNNReal ≤ T := Real.toNNReal_le_iff_le_coe.mpr hp.2
    simp only [min_eq_left ht]
  refine ⟨?_, MemLp.ae_eq heq hc⟩
  filter_upwards [heq, hbc] with p heq hp
  rwa [← heq]

theorem HasFreeIsingLaw.gibbsField_copy_joint_bounds
    {Ω : Type*} [mΩ : MeasurableSpace Ω] {P : Measure Ω} [IsFiniteMeasure P]
    {d : ℕ} {beta : ℝ} {μ : Measure (TreeVertex d → IsingSpin)}
    (hμ : HasFreeIsingLaw (Real.tanh beta) μ) (hbeta : 0 ≤ beta)
    {F : Filtration ℝ≥0 mΩ}
    {X X' : TreeVertex d → ℝ≥0 → Ω → ℝ}
    (hX : ∀ i, IsStronglyProgressive F (X i))
    (hX' : ∀ i, IsStronglyProgressive F (X' i))
    (T : ℝ≥0) (v : TreeVertex d)
    (hlaw : ∀ t ≤ T, IdentDistrib (fun ω i => X i t ω) (observation t) P
      (μ.prod (gaussianNoiseLaw (TreeVertex d) t)))
    (hlaw' : ∀ t ≤ T, IdentDistrib (fun ω i => X' i t ω) (observation t) P
      (μ.prod (gaussianNoiseLaw (TreeVertex d) t)))
    {W : ℝ≥0 → Ω → ℝ}
    (hx : ∀ t ≤ T, ∀ᵐ ω ∂P, X v t ω = W t ω + nnrealTimePrimitive
      (fun s p => infiniteGibbsSpinMean beta v (fun i => X i s p)) t ω)
    (hx' : ∀ t ≤ T, ∀ᵐ ω ∂P, X' v t ω = W t ω + nnrealTimePrimitive
      (fun s p => infiniteGibbsSpinMean beta v (fun i => X' i s p)) t ω) :
    let U := fun t ω =>
      Real.artanh (infiniteGibbsSpinMean beta v (fun i => X i t ω)) -
        Real.artanh (infiniteGibbsSpinMean beta v (fun i => X' i t ω))
    (∀ᵐ p ∂(volume.restrict (Ioc (0 : ℝ) (T : ℝ))).prod P,
      |U p.1.toNNReal p.2| ≤ 2 * (T : ℝ) + 2 * (d : ℝ) * beta) ∧
    MemLp (fun p : ℝ × Ω => U p.1.toNNReal p.2) 2
      ((volume.restrict (Ioc (0 : ℝ) (T : ℝ))).prod P) := by
  dsimp only
  have ha : Measurable Real.artanh := by unfold Real.artanh; fun_prop
  have hm := isStronglyProgressive_infiniteGibbsSpinMean F beta v X hX
  have hm' := isStronglyProgressive_infiniteGibbsSpinMean F beta v X' hX'
  have hU : IsStronglyProgressive F (fun t ω =>
      Real.artanh (infiniteGibbsSpinMean beta v (fun i => X i t ω)) -
        Real.artanh (infiniteGibbsSpinMean beta v (fun i => X' i t ω))) := by
    intro t
    exact ((ha.comp (hm t).measurable).sub
      (ha.comp (hm' t).measurable)).stronglyMeasurable
  apply progressive_memLp_two_on_horizon hU T (2 * (T : ℝ) + 2 * (d : ℝ) * beta)
  intro t ht
  filter_upwards [hμ.gibbsField_copy_bound_of_shared_innovation hbeta
    hX hX' t v (hlaw t ht) (hlaw' t ht) (hx t ht) (hx' t ht)] with ω hω
  exact hω.trans (by have htr : (t : ℝ) ≤ T := ht; linarith)

end Problem367

end

end OAI