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4ee1feb6907a205a6746e81d2a23ec3d779c225a
subsection
36
223
The Rising Sun Lemma, and [PR:LPO]LPO and [PR:WLPO]WLPO
Since [PR:LPO]LPO implies that f is uniformly continuous (see REF ) and therefore S_x = \sup _{[x,1]} f exists, we can decide whether f(x) = S_x, or f(x) < S_x. In the second case, using Proposition REF .REF , we can find b_x = \inf \mbox{$\left\lbrace \,z \geqslant x \, | \, f(z) = S_x \,\right\rbrace $}. Using Propos...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.024241965264081955, 0.02045844867825508, -0.013638965785503387, 0.011731951497495174, -0.026988064870238304, -0.0028433583211153746, 0.006659293547272682, 0.034051645547151566, 0.02598116174340248, 0.027140626683831215, -0.015149321407079697, 0.003266715444624424, -0.014691637828946114, ...
5cb2f531c4eeaad70cd360bd5a2945dd9f77a75d
subsection
37
223
The Rising Sun Lemma, and [PR:LPO]LPO and [PR:WLPO]WLPO
If we had followed Tao's formulation more closely we get an equivalence to [PR:WLPO]WLPO. Luckily, we can reuse most of the proof above.Proposition 3.9 [PR:WLPO]WLPO is equivalent to the following statement.Consider a continuous function f:[0,1] \rightarrow \mathbb {R}. Then one can find a, at most countableThis is on...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.01875813864171505, 0.02518383041024208, -0.026664333418011665, 0.01139377523213625, -0.0003920664603356272, 0.02483278326690197, 0.0060021462850272655, 0.00191549735609442, 0.007223180495202541, 0.04902452230453491, -0.01848340593278408, -0.016102388501167297, -0.0033807384315878153, 0....
f1ba8f76e5d1f2852840169e4efea9d4e7a85765
subsection
38
223
[PR:LLPO]LLPO and [PR:WKL]WKL
The final limited omniscience principle is the lesser limited principle of omniscience. [leftmargin=2em,rightmargin=3em,skipabove=1em,skipbelow=1em, innerleftmargin=-1em,innerrightmargin=0em, nobreak=true, linecolor=blueish, linewidth=5pt, bottomline=false, topline=false, rightline=false, backgroundcolor=blueish!10]([P...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.07780548185110092, 0.010885139927268028, -0.0033296169713139534, -0.027948951348662376, -0.02012263424694538, -0.003493618918582797, -0.02128208801150322, 0.025919904932379723, 0.006426580715924501, 0.01853601261973381, -0.04982602223753929, 0.015050021931529045, 0.00913070235401392, 0....
77b9ef4d2922289353d96636952b015046c318f7
subsection
39
223
Completeness of Finite Sets
In Proposition REF we cited a paper by Mandelkern that among many other insights shows that [PR:LLPO]LLPO is equivalent to every two-element set of reals being closed. That is constructively we cannot show that for any two reals a,b\overline{\left\lbrace a,b \right\rbrace } = \left\lbrace a,b \right\rbrace \ .Analysing...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.03065687231719494, 0.01629743166267872, -0.004738157615065575, 0.007278908975422382, -0.014443369582295418, 0.019395163282752037, 0.023545820266008377, 0.004928904585540295, 0.011780540458858013, 0.012894502840936184, -0.03808837756514549, 0.002205036347731948, 0.01631269045174122, 0.01...
e4f0bd191fde6f74d3a9536394c2d07506e887f1
subsection
40
223
Completeness of Finite Sets
Now if z_\infty \in \left\lbrace a,b, \inf \left\lbrace a,b \right\rbrace , \sup \left\lbrace a, b \right\rbrace \right\rbrace we can make the following decisions:z_\infty = 0: there cannot be an even m such that a_m = 1, since in that case a \ne 0 and z_n \rightarrow a. z_\infty = a: there cannot be an odd m such that...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.008322994224727154, 0.01371653750538826, -0.002317240461707115, -0.0014294417342171073, -0.021970871835947037, -0.010832861065864563, 0.020689237862825394, 0.007045174017548561, -0.0028379044961184263, -0.0141895217821002, -0.023145703598856926, 0.017958136275410652, -0.005183752626180649...
30a0f6c2ab4b3db7e1bb518e4a2a2b9835771dff
subsection
41
223
Completeness of Finite Sets
Notice that there exists a realisability model (based on infinite time Turing machines) in which there is a surjection \mathbb {N}\rightarrow \mathbb {N}^{\mathbb {N}} , which means that the closure of \left\lbrace a,b \right\rbrace is countable, but that in that model also [PR:LPO]LPO and therefore [PR:LLPO]LLPO holds...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.023810042068362236, 0.02339794486761093, -0.016911234706640244, 0.04691799357533455, -0.035745587199926376, -0.007936680689454079, -0.008600614964962006, 0.02933519333600998, -0.0007860366604290903, 0.02022327296435833, -0.010180319659411907, -0.010065848007798195, 0.04136231541633606, ...
f2533a3ecae565f7806256f91ab378b78012abb6
subsection
42
223
[PR:WKL]WKL, Minima, and Fixed Points
The one principle in Constructive Reverse Mathematics that is possibly best known by non-constructivists is Weak Kőnig's Lemma. [leftmargin=2em,rightmargin=3em,skipabove=1em,skipbelow=1em, innerleftmargin=-1em,innerrightmargin=0em, nobreak=true, linecolor=blueish, linewidth=5pt, bottomline=false, topline=false, rightli...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.07373210787773132, 0.02938908152282238, -0.014442765153944492, 0.030945511534810066, -0.01090264692902565, -0.0274359118193388, 0.0437936969101429, 0.008896071463823318, -0.003610691288486123, 0.03567584231495857, -0.02813783288002014, -0.018249917775392532, -0.011841083876788616, 0.009...
4124d4697c93a46a09e4ecf4c21ff3a73f4a53ef
subsection
43
223
[PR:WKL]WKL, Minima, and Fixed Points
Thus we can, using dependent choice, iteratively define a sequence \alpha \in 2^{\mathbb {N}} such that T_{\overline{\alpha }n} is a infinite, decidable tree for all n \in \mathbb {N}. In particular \overline{\alpha }n \in T.Remark 4.6Analysing the above proof we can see that [PR:WLPO]WLPO implies [PR:WKL]WKL, only ass...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.03085586056113243, 0.02826164849102497, -0.010193726979196072, 0.021562479436397552, 0.0009685375262051821, -0.0028879682067781687, 0.020265372470021248, 0.0093544228002429, -0.003378198016434908, 0.04391847923398018, 0.004818366840481758, -0.005718711297959089, -0.008408298715949059, 0...
99b7db858211ea6a3458c0ebef13ad24d507c558
subsection
44
223
[PR:WKL]WKL, Minima, and Fixed Points
Finally the equivalence of REF and [PR:WKL]WKL can be found in (and relies on the equivalence of [PR:WKL]WKL and REF ).Remark 4.8 Using Proposition REF we can replace uniform by point-wise continuity in the above proposition.This last proposition above also allows the following heuristic.Heuristic 4.9 Many fix point th...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.019979283213615417, 0.03418914973735809, -0.004170618485659361, -0.006185336038470268, -0.0036402286496013403, -0.021215587854385376, -0.009661487303674221, 0.008860179223120213, 0.010172798298299313, 0.0236271433532238, -0.020330334082245827, -0.0014852819731459022, 0.0015959388110786676...
95f7f564f846dfbf8c929a590c6375f61237a20a
subsection
45
223
Space-filling curves
The content of this section might well be folklore among some constructivists. We do not claim to be the first to prove these results, but we are also not aware that they have been written down anywhere else.One of the stranger objects in (classical) analysis are space-filling curves, which are continuous functions [0,...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.0788571834564209, 0.05621321126818657, -0.010162322781980038, 0.019195498898625374, 0.030242830514907837, -0.018096869811415672, 0.01267238613218069, 0.02494804561138153, 0.022705011069774628, -0.0016164731932803988, 0.007526375353336334, -0.02342217229306698, 0.02528373897075653, -0.02...
3d1dfa401541ca99a893b65957876a3a35d4302a
subsection
46
223
Space-filling curves
The question of whether we can prove a stronger version of non-injectiveness for an arbitrary space-filling curve constructively appears to be a tricky one. quQuestion 2Is every space-filling curve non-injective? More precise: if f is a space-filling curve, then does there exist x \ne y with f(x) = f(y)?It seems feasib...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.0713973194360733, 0.01591183803975582, 0.00858140829950571, 0.002282654633745551, 0.03844470903277397, -0.03969568759202957, 0.005694241262972355, 0.05092398449778557, 0.04848305135965347, 0.021358171477913857, 0.022227754816412926, -0.025995947420597076, 0.01765100471675396, -0.0008242...
2d8e1675b0b5193e2476bb9bfae5f17d2070b97c
subsection
47
223
Space-filling curves
Without loss of generality we may assume that f([0,1]) \subset [-1,1] and that f(0)=-1 and f(1) = 1. Now define h,g:[0,1] \rightarrow [0,1]^2 piecewise linearly byh(x) = {\left\lbrace \begin{array}{ll} -\frac{3}{2}x+1 & \text{ if } 0 \leqslant x \leqslant \frac{1}{3} \\ \frac{1}{2} & \text{ if } \frac{1}{3} \leqslant x...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.05999672785401344, -0.0011138762347400188, -0.0175473652780056, -0.0178220197558403, 0.05090261623263359, 0.008193856105208397, 0.014602459035813808, 0.0172421932220459, 0.008712648414075375, -0.012618844397366047, -0.025649670511484146, -0.03851265087723732, 0.010925142094492912, 0.007...
ff1b605e16406cec1af2f6c8ae0aebc80573cc20
subsection
48
223
The Greedy Algorithm
A matroid (E, \mathcal {F}) consists of a finite set E together with a collection \mathcal {F} of subsets E, such that\emptyset \in \mathcal {F} A \in \mathcal {F} \wedge B \subset A \Rightarrow B \in \mathcal {F} A,B \in \mathcal {F} \wedge {B}={A}+1 \Rightarrow \exists {x \in B} : { A \cup \left\lbrace x \right\rbr...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.02135639637708664, -0.002488401485607028, -0.04195006191730499, -0.008191702887415886, 0.019937720149755478, -0.036549944430589676, 0.01829022727906704, 0.02948708087205887, 0.009023076854646206, 0.0249564740806818, -0.054916445165872574, 0.0006359248072840273, -0.007772202603518963, 0....
2923b1d4940f34254ff482dd68ebbdb909d8466b
subsection
49
223
The Greedy Algorithm
Z_{i} = \emptyset terminate and return F_{i} .  choose y \in Z_{i} such that w(y) \leqslant w(z_{i}) for all z_{i} \in Z_{i} let F_{i+1} = F_{i} \cup \left\lbrace y \right\rbraceNotice, that in step 6 we need (REF ). For (\ref {greedy3}) \Rightarrow (\ref {greedy1}) let x,y \in \mathbb {R}. Then\mathcal {M} = \left(\le...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.01325365249067545, 0.005425070412456989, -0.0052152397111058235, -0.043400563299655914, 0.008942591026425362, -0.015100160613656044, 0.03638077899813652, -0.01979273185133934, -0.00754626514390111, 0.03061235137283802, -0.06470407545566559, 0.010430479422211647, -0.00016214168863371015, ...
49ef1901dce4e2761d20ea1111ea6fb8c02cba2d
subsection
50
223
Sharkovskii's Theorem
Sharkovskii'sThere are various alternative ways of spelling Sharkovskii. Among them Sharkovsky , Sarkovskii , Sarkovski . Theorem from 1964 is, in our opinion, one of the most entertaining results in mathematics: simple to state yet utterly surprising. It concerns itself with a very rudimentary type of dynamical system...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ 0.008898417465388775, 0.0036784193944185972, -0.06477681547403336, -0.02295577898621559, 0.0004595639475155622, 0.03510524705052376, 0.04353050887584686, 0.005326839629560709, 0.016133150085806847, 0.025565778836607933, -0.03794419392943382, -0.0033502618316560984, 0.0038787482772022486, 0...
61c76c0a79f9583353982f8872682a8c2b52fa9f
subsection
51
223
Sharkovskii's Theorem
\\ \end{array}\right.} [Figure: We think of a as being very small. Depending on a f crosses the lines y = 0 and y=1 or misses both.]As f([0,\frac{1}{3}]) \supset [0, \frac{2}{3}] and f([\frac{2}{3},1]) \supset [\frac{1}{3},1] we see that f([0,1]) \supset [0,1]. So assume there exists an interval [c,d] \subset [0,1] su...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ 0.0049314554780721664, 0.019619030877947807, -0.02782667987048626, 0.008138999342918396, 0.02407374046742916, 0.018108701333403587, 0.001865028403699398, 0.00406568543985486, 0.010991844348609447, 0.001472190022468567, -0.05528721958398819, 0.0002170383813790977, 0.0005549317575059831, 0.0...
ef22bed1886357b841cd670cfc2e446c6b2c3ef4
subsection
52
223
Sharkovskii's Theorem
As we assume [PR:LLPO]LLPO either\sup \left\lbrace f *{a_0, \frac{1}{2} (a_n + b_n)} \right\rbrace \geqslant b \text{ or } \sup \left\lbrace f \left(*{a_0, \frac{1}{2} (a_n + b_n)} \right) \right\rbrace \leqslant b \ .In the first case set a_{n+1} = a_n and as we assumed [PR:LLPO]LLPO the minimum principle holds and so...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.027119876816868782, 0.011324113234877586, -0.03732989355921745, -0.006596830207854509, 0.0047806985676288605, 0.020130060613155365, 0.025212176144123077, 0.005490363575518131, 0.008889886550605297, 0.0056239026598632336, -0.044533371925354004, -0.0009748352458700538, 0.009591920301318169,...
789edc5b87c2f48a20adb0029ab1b406c6665106
subsection
53
223
Sharkovskii's Theorem
\\ \end{array}\right.} [Figure: We cannot decide whether the graph of f between \frac{2}{4} and \frac{3}{4} lies above or below the diagonal.]f(0) = \frac{1}{4}, f(\frac{1}{4}) = 1 and f(1)=0 so f has a 3–periodic point. If f has a fixed point x, then either x < \frac{3}{4} or x > \frac{2}{4}. In the first case a \leq...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.021419430151581764, -0.014249108731746674, -0.042686302214860916, -0.005850677844136953, 0.022914519533514977, 0.012189547531306744, 0.027155688032507896, 0.010801251046359539, 0.008009402081370354, 0.00045386614510789514, -0.013913475908339024, 0.004264053422957659, 0.011678471229970455,...
fdf8fd02509e552bf3299a97b924fe595f27b29d
subsection
54
223
Graph colourings
We assume that the reader is familiar with basic graph theoretic definitions. A nice little theorem by Erdős and Bruijn *Theorem 8.1.3, reminiscent of the compactness theorem in logic. is [leftmargin=2em,rightmargin=3em,skipabove=1em,skipbelow=1em, innerleftmargin=-1em,innerrightmargin=0em, nobreak=true, linecolor=blue...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.030398104339838028, 0.007031087763607502, 0.022859618067741394, -0.018937774002552032, -0.007233283948153257, -0.034457288682460785, -0.030428623780608177, -0.01812898926436901, -0.0009079754818230867, 0.05225055664777756, -0.009415477514266968, -0.0018912977539002895, 0.02421776764094829...
63a7cc4ddf05a89770f5f6f3b25fb7af5d16bc3b
subsection
55
223
Graph colourings
If all of G can be coloured, then if the vertices 1 and 2 get the same colour there cannot be an even n with a_n=1, which means \forall {n \in \mathbb {N}} : {a_{2n}=0}. Similarly if 1 and 2 are coloured with different colours, then \forall {n \in \mathbb {N}} : {a_{2n+1}=0}. For an arbitrary k>2 we simply add one copy...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.025768909603357315, 0.010801887139678001, -0.0013244899455457926, -0.009558449499309063, -0.00030084705213084817, -0.04250572994351387, 0.00018475156684871763, -0.01859816536307335, -0.013990580104291439, 0.04897465929389, 0.000876795151270926, 0.014501686207950115, 0.01844559609889984, ...
6b8d82d4f373e3b4858c09f7f38995f2c1a810e3
subsection
56
223
Graph colourings
In particular \overline{\alpha }n \in T for all n \in \mathbb {N}, which means we have found a path through T.
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ 0.03804532811045647, 0.006357414182275534, -0.03142477199435234, 0.0520186722278595, 0.018763333559036255, -0.0061133382841944695, -0.012287694960832596, 0.018839607015252113, 0.010945278219878674, 0.022165141999721527, 0.022317688912153244, -0.0024808025918900967, -0.01388181559741497, 0....
ff7f6ecd41b846e5b7d6be8d02e899ce777cec5b
subsection
57
223
Variations of [PR:WKL]WKL
Reminiscent of the way [PR:WWKL]WWKL (Section ) is a weakening of [PR:FAN]FAN_{\Delta } is the following weakening of [PR:WKL]WKL.This version was communicated to us by M. Hendtlass by Email. We do not know who deserves credit for proposing it. Let k<1. We now require that for each n our tree not only have at least one...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.059906378388404846, 0.022537371143698692, -0.02330031618475914, -0.002660767873749137, -0.004611997399479151, 0.010459965094923973, 0.045105259865522385, 0.00584415253251791, -0.007720995228737593, 0.05419955402612686, -0.014526457525789738, -0.0195924062281847, -0.01924145221710205, 0....
9d984e4de011ee4f9e2c1cf98d75dd6dba309277
subsection
58
223
Variations of [PR:WKL]WKL
It remains an open question whether the same holds for k \geqslant \frac{1}{2}. quQuestion 3To what principle is [PR:WKLp]\textrm {WKL}^{\prime }(k) equivalent to for k > \frac{1}{2}?Notice that this question seems to be related to the question whether [PR:LLPOn]\textrm {LLPO}_{n} (which will be introduced in Section )...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.040402356535196304, 0.03509267792105675, 0.010657493956387043, -0.015684902667999268, -0.032407328486442566, -0.02082674205303192, 0.04751243814826012, 0.005958126857876778, -0.015333975665271282, -0.0142430504783988, -0.019972311332821846, 0.00326895946636796, -0.025663429871201515, 0....
875431497e111fc1603e14bc84a3b55057e897a7
subsection
59
223
Compactness of Propositional logic
The language of first order logic is, as usual, defined inductively viaEvery proposition symbol A_{0},A_{1},A_{2}, \dots is a formula. If \alpha , \beta are formulas, then so is \lnot \alpha , \alpha \wedge \beta , \alpha \vee \beta , \alpha \rightarrow \beta .It is straightforward to show that an truth assignment \ma...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.0034819331485778093, 0.01161661371588707, -0.010205535218119621, -0.007085905876010656, -0.004889198578894138, -0.0761525109410286, 0.027870720252394676, 0.010403848253190517, 0.03533037006855011, 0.015682047232985497, -0.012364104390144348, 0.011540339328348637, -0.012325967662036419, ...
4777dce68eaa18f7014b4d5577803d074613b902
subsection
60
223
Compactness of Propositional logic
\end{array}\right.}For all j \leqslant i \leqslant m, sinceT is a tree \overline{u}i \in T, and therefore we have that \mathcal {B^{\prime }}\left(B_{\overline{u}i,j} \right) = \mathbf {t}. Hence \mathcal {B^{\prime }}(\alpha _{i}) = \mathbf {t} for all i \leqslant m, which means that \mathcal {B^{\prime }} is a model ...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.019580012187361717, -0.01359002385288477, -0.035527877509593964, -0.019946279004216194, 0.022128617390990257, -0.02588285319507122, -0.002369288355112076, 0.01825229451060295, -0.0058602686040103436, 0.025974418967962265, -0.016634617000818253, 0.01009522844105959, 0.004379940219223499, ...
153c3039c52bbcb0001e7c635f687ae3dd635095
subsection
61
223
[PR:MP]MP and Below
We will start this chapter by introducing some notation. If a number x \in \mathbb {R} is such that \lnot \lnot (0 < x) we say that x is almost positive and write 0 \lessdot x. Furthermore, we write y \lessdot x instead of 0\lessdot x - y and x \gtrdot y interchangeably with y \lessdot x. Note that since x \leqslant y ...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.05689402297139168, 0.01593276858329773, -0.020648501813411713, 0.02722610905766487, 0.02276981808245182, -0.035345107316970825, -0.0034433244727551937, -0.003452862845733762, 0.015871724113821983, 0.010774458758533001, -0.05091160535812378, 0.005616148468106985, -0.03629130497574806, 0....
4e492e8376e49102077b7c0f262a0d11277ce758
subsection
62
223
[PR:MP]MP
Markov's principle is a weak form of double negation elimination. [leftmargin=2em,rightmargin=3em,skipabove=1em,skipbelow=1em, innerleftmargin=-1em,innerrightmargin=0em, nobreak=true, linecolor=blueish, linewidth=5pt, bottomline=false, topline=false, rightline=false, backgroundcolor=blueish!10]([PR:MP]MP)     Every al...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.07115337252616882, -0.020976819097995758, 0.01131985429674387, -0.036614082753658295, 0.008848403580486774, -0.003756757592782378, 0.04576760530471802, 0.028025029227137566, 0.04241131246089935, 0.031182995066046715, -0.08390727639198303, -0.003081685397773981, -0.007833888754248619, 0....
ef0dda117966899a226bf417cef8208b2a4e8475
subsection
63
223
[PR:MP]MP
Given m \in \mathbb {N} we can consider the following binary sequence c_n defined byc_n = {\left\lbrace \begin{array}{ll} 0 & \text{if } m \notin \left\lbrace a_1, b_1, \dots , a_n,b_n \right\rbrace \\ 1 & \text{otherwise} \ . \end{array}\right.}Now we have \lnot \forall {n \in \mathbb {N}} : {c_n =0}, since the assump...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.047206420451402664, 0.001487597357481718, -0.02625799924135208, -0.017454475164413452, 0.041072942316532135, -0.0173629317432642, -0.00963505357503891, 0.03564130514860153, 0.050471507012844086, 0.02386258728802204, -0.03155232220888138, -0.0066827451810240746, -0.0016621039249002934, -...
aad4e4940bc29265503ef174ddf7607a60506246
subsection
64
223
[PR:WMP]WMP
Weak Markov's Principle states that every pseudo-positive number is positive: [leftmargin=2em,rightmargin=3em,skipabove=1em,skipbelow=1em, innerleftmargin=-1em,innerrightmargin=0em, nobreak=true, linecolor=blueish, linewidth=5pt, bottomline=false, topline=false, rightline=false, backgroundcolor=blueish!10]([PR:WMP]WMP)...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.06290988624095917, -0.015246951952576637, -0.0060331858694553375, -0.031912580132484436, 0.016215616837143898, -0.02474292740225792, 0.030646448954939842, 0.02213439531624317, 0.01879364252090454, 0.02510903775691986, -0.06589978188276291, 0.008695109747350216, -0.019159751012921333, -0...
3e070df464f617d7096a06795142f47b63b0a9bf
subsection
65
223
[PR:WMP]WMP
Consider a x^{\prime } = \min \left\lbrace x,y \right\rbrace \in (- \infty , x]. With the previous step we know that either x^{\prime } \gtrdot 0 or x^{\prime } \lessdot x. In the first case, since y \geqslant x^{\prime }, by part REF of Lemma REF , we have y \gtrdot 0. In the second case, by part REF of Lemma REF , we...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.05872160941362381, 0.03042902611196041, -0.01788506470620632, 0.021181287243962288, -0.010888219811022282, -0.011124754324555397, -0.002840322209522128, 0.02974231168627739, 0.018983805552124977, 0.027392227202653885, -0.04651337489485741, 0.00453612208366394, -0.04062290117144585, 0.01...
2bd13b3c37c21c37b6b4b71e46b98d48ba74d9ae
subsection
66
223
[PR:WMP]WMP
Define a sequence (y_n)_{n \geqslant 1}y_n = {\left\lbrace \begin{array}{ll} x & \text{if } \forall {i \leqslant n} : {\alpha (i) = \beta (i) } \\ 0 & \text{otherwise} \end{array}\right.} \ .It is easy to see that (y_n)_{n \geqslant 1} is a Cauchy sequence converging to a limit y. Since x is pseudo-positive by Lemma RE...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.06469865888357162, -0.001689947210252285, -0.0333564318716526, 0.003528670873492956, 0.008888435550034046, -0.03939904272556305, -0.00397118553519249, -0.0046196975745260715, 0.02920594997704029, 0.032074663788080215, -0.04956161230802536, 0.01174951996654272, -0.0054551344364881516, 0....
41bb62aea77fd0bd4b48c61701995bc9cdf7e4bf
subsection
67
223
[PR:WMP]WMP
Define a sequence (x_n)_{n \geqslant 1} in \left\lbrace a,b \right\rbrace by the following algorithm. As long as \lambda _n=0 set x_n=a. If \lambda _n=1 for the first time we can decide whether x > p d(a,b) or x < q d(a,b) . In the first case we set x_n=a from then on, in the second case we set x_n = b from then on. It...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.06117529422044754, -0.016354093328118324, -0.03679671138525009, -0.005244141444563866, -0.015133638866245747, -0.024836255237460136, 0.04656035080552101, -0.013562303967773914, 0.021952930837869644, 0.022181766107678413, -0.037559494376182556, -0.00845927745103836, 0.010305214673280716, ...
021b171fa8ee778931820c1a8e6819b23103aa6b
subsection
68
223
[PR:WMP]WMP
If X= \overline{ \left\lbrace a,b \right\rbrace }, then any function f:X \rightarrow \mathbb {R} is strongly extensional.Obviously REF implies REF .Assume f:2^{\mathbb {N}}\rightarrow \mathbb {R} is a function with f(\alpha ) \ne f(\beta ) If \gamma \in \mathbb {N}^{\mathbb {N}}, then let \gamma ^{01} \in 2^{\mathbb {N...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.048197757452726364, 0.022969482466578484, -0.017826149240136147, 0.0012991874245926738, -0.020817523822188377, -0.012637030333280563, 0.010538489557802677, 0.04056669771671295, 0.0161320548504591, 0.013934310525655746, -0.037850040942430496, 0.02647976763546467, -0.028357008472085, 0.02...
98fc1e79478c7632684a1ae26498d244e1581114
subsection
69
223
[PR:WMP]WMP
Now we can consider the function g:\mathbb {N}_{\infty }\rightarrow \mathbb {R} defined by g(\alpha ) = f(x^\alpha _\infty ). Furthermore, it is easy to see that x^{(000\ldots )}_\infty = a and x^{\lambda }_\infty = b. Hence \lambda \ne 000\ldots and thus a \ne b.Next, we will show that REF implies REF . So let f:Y \ri...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.040061090141534805, 0.035026755183935165, -0.019267765805125237, 0.005205958150327206, 0.0010316569823771715, 0.005762786138802767, 0.0376812219619751, 0.023569833487272263, 0.04219686612486839, -0.0018287596758455038, -0.009473700076341629, -0.0035240333527326584, -0.011556083336472511, ...
f4f0341b1b034a6b3c847bb8430edf62ba36679a
subsection
70
223
Body
The disjunctive version of Markov's principle [PR:MPv]{\textrm {MP}^{\vee }} can be seen as an instance of de'Morgan's laws (see Section ) as well as another weakening of [PR:MP]MP. It states that every almost positive number is pseudo-positive.[leftmargin=2em,rightmargin=3em,skipabove=1em,skipbelow=1em, innerleftmargi...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.06577718257904053, -0.00595686212182045, -0.014895969070494175, -0.017420580610632896, -0.016642604023218155, -0.040820904076099396, 0.0238274484872818, 0.012569665908813477, 0.024208810180425644, 0.0302190613001585, -0.08774358779191971, -0.01017471682280302, -0.029593629762530327, 0.0...
7c7515447b2e0aa9cfb4b7a0feaf726117110ecb
subsection
71
223
Body
If \alpha is a binary sequence such that \lnot \forall {n \in \mathbb {N}} : {\alpha (n)=0}, then for any \beta we have \forall {\beta \in 2^{\mathbb {N}}} : {\lnot (\alpha = \beta ) \vee \lnot (\beta = 0)} For \alpha ,\beta \in 2^{\mathbb {N}} \lnot (\forall {n \in \mathbb {N}} : {\alpha _n =0} \wedge \forall {n ...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.038356978446245193, 0.020887313410639763, -0.04394116997718811, 0.0026833864394575357, 0.01386893168091774, 0.0030533771496266127, 0.015013232827186584, 0.020490622147917747, 0.01670679822564125, 0.019117459654808044, -0.04592462629079819, 0.004954824689775705, -0.034054405987262726, 0....
23609059ef607e95787dfb39a6514b41dac6758b
subsection
72
223
Body
To see that \ref {MPo:3} \Rightarrow \ref {MPo:4} let \alpha be a binary sequence such that \lnot \forall {n \in \mathbb {N}} : {\alpha _n=0}, and \beta \in 2^{\mathbb {N}} be arbitrary. Now define \gamma \in 2^{\mathbb {N}} by\gamma _{2n}=1 & \Rightarrow \alpha _n \ne \beta _n \ , \\ \gamma _{2n+1}=1 & \Rightarrow \be...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.047103606164455414, 0.01698843576014042, -0.03913598507642746, -0.01613367162644863, -0.009829787537455559, -0.004170790780335665, -0.008051572367548943, 0.016652636229991913, 0.00834158156067133, 0.013722016476094723, -0.04166974872350693, 0.039319150149822235, -0.02962673455476761, 0....
a3b752d95211949b082e7fffe47dd510be8d5fbc
subsection
73
223
Body
So we have decided\lnot (\alpha = \beta ) \vee \lnot (\beta = 000\ldots ) \ .To see that \ref {MPo:4} \Rightarrow \ref {MPo:8} let \alpha , \beta be a binary sequences such that\lnot (\forall {n \in \mathbb {N}} : {\alpha _n =0} \wedge \forall {n \in \mathbb {N}} : {\beta _n =0}) \ .Now consider the sequences\gamma = \...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.0664193406701088, 0.011171635240316391, -0.033118098974227905, -0.0042275176383554935, -0.002678445540368557, 0.03229396417737007, 0.017749469727277756, 0.02173279970884323, 0.01100375596433878, 0.010591687634587288, -0.04456444829702377, 0.020435547456145287, -0.0039871446788311005, 0....
8e3af1ed961b8fd6709dede6a55b5dc7de8ef192
subsection
74
223
Body
Because of the similarity of [PR:LLPO]LLPO and [PR:MPv]{\textrm {MP}^{\vee }} it is not surprising that we can find a weakening of [PR:WKL]WKL that is equivalent to the latter. [leftmargin=2em,rightmargin=3em,skipabove=1em,skipbelow=1em, innerleftmargin=-1em,innerrightmargin=0em, nobreak=true, linecolor=blueish, linewi...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.07037020474672318, 0.01698222942650318, -0.016097260639071465, 0.010642501525580883, 0.0013036110904067755, -0.0043943230994045734, 0.036558330059051514, 0.019667647778987885, -0.009337936528027058, 0.047788266092538834, -0.01487661525607109, -0.020339002832770348, -0.011062098667025566, ...
c2a67539ae7e9adec2a04069ea0cff5b5e4a9df0
subsection
75
223
Body
In particular \overline{\alpha }n \in T.Conversely consider a binary sequence (a_n)_{n \geqslant 1} with at most one 1 and such that \lnot \forall {n \in \mathbb {N}} : {a_n = 0}. Now consider the decidable tree T defined byu \in T \iff \exists {n \in \mathbb {N}} : {u = 0^n \wedge \forall {i \leqslant n} : {a_{2i} = 0...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.010557047091424465, 0.02712489850819111, -0.02776564471423626, 0.018947763368487358, 0.022029444575309753, 0.0018154459539800882, 0.013081889599561691, 0.02085474506020546, 0.008688205853104591, 0.05010020732879639, -0.025202661752700806, -0.018307017162442207, -0.013020866550505161, 0....
6047ae48ec85e4b5d97c0c7dce009d96a7da23be
subsection
76
223
Body
Finally, it is also easy to see that T has at most one path. However if T actually admits a path \alpha we can check whether \alpha (1)=0, in which case \lnot \forall {n \in \mathbb {N}} : {a_n=0}, or \alpha (1)=1, in which case \forall {n \in \mathbb {N}} : {a_n=0}. Thus [PR:WLPO]WLPO holds, which contradicts the exis...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.024868043139576912, 0.03682911396026611, -0.03710373118519783, -0.005210083909332752, -0.009931961074471474, -0.007597721181809902, 0.005812714342027903, 0.04634914919734001, -0.015218326821923256, 0.0429622158408165, -0.008017274551093578, -0.007818940095603466, 0.012868830934166908, 0...
48ffaf2969c02426bcd514fadfb182e89c59ea37
subsection
77
223
Body
\forall { x,y \in \mathbb {R}} : { (x > 0 \iff y = 0) \Rightarrow \lnot (x = 0) \vee y=0}.There are no other, more interesting, equivalences known, at this stage.tocsection1½ [PR:BD]BD At the same time as investigating [PR:BDN]BD-N H. Ishihara also introduced the stronger principle [PR:BD]BD which does not require a co...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.03385353088378906, 0.0014948288444429636, -0.03186932951211929, -0.012515733018517494, 0.0019441359909251332, -0.04444611817598343, 0.039592452347278595, 0.017048871144652367, 0.07283546030521393, 0.01683518849313259, -0.05717553198337555, -0.004304191097617149, -0.027061456814408302, 0...
06b456cd1c38bbe0ec182f5b6ee2b380726d199d
subsection
78
223
Body
Notice that \Pi _{1}^0 statements are stable, that is we can eliminate preceding double negations.The equivalencies for the restricted versions of [Pr:DGP]DGP are non-trivial, and the proofs are entertaining: First assume that [PR:LLPO]LLPO holds. And consider two binary sequences a_n and b_n. Now let \alpha be the seq...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.038703806698322296, 0.015673821792006493, -0.026036551222205162, 0.01040851604193449, -0.015658559277653694, -0.0486544705927372, 0.0084244878962636, 0.03604826331138611, 0.008058206178247929, 0.019779233261942863, -0.05424027144908905, 0.005879590753465891, -0.001314418506808579, 0.016...
843f08c90411670f244e9d8cd1dfccbd256270a3
subsection
79
223
Body
Similarly in the second case we can show that \forall {n \in \mathbb {N}} : {a_{2n+1} =0}. Thus we have shown that \Sigma _1^0-[Pr:DGP]DGP implies [PR:LLPO]LLPO.Next, let a_n and b_n be binary sequences and construct \alpha and \alpha ^\prime as above. Using [PR:LLPO]LLPO we can, again, make the decision in Equation (R...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.022683948278427124, 0.03856423869729042, -0.0009300686069764197, -0.027870595455169678, -0.026070524007081985, -0.020166900008916855, 0.013744612224400043, 0.031211404129862785, -0.0023225494660437107, 0.008229986764490604, -0.033713199198246, 0.03310300409793854, 0.005060793366283178, ...
265602cbe1b88a80e9bc3f877fbed44f6f28f00c
subsection
80
223
Body
In the first case, also \exists {n \in \mathbb {N}} : {b_n =1} \Rightarrow \forall {n \in \mathbb {N}} : {a_n =0}. In the second case \forall {n \in \mathbb {N}} : {a_n =0} \Rightarrow \exists {n \in \mathbb {N}} : {b_n =1}, since the antecedent contradicts our assumption.Conversely, let a_n be an arbitrary binary sequ...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.031045489013195038, 0.011350291781127453, -0.02788754366338253, 0.020976681262254715, 0.0027250617276877165, -0.03679691255092621, 0.0023169699124991894, 0.028040101751685143, 0.03585105389356613, 0.025492388755083084, -0.02938261069357395, -0.025416109710931778, -0.03240325301885605, 0...
340b7a49c850717c3bfddeac927402de26a2012b
subsection
81
223
Body
Every searchable subset of \mathbb {N} is bounded.Assume \lnot \textrm {LPO} and let S \subset \mathbb {N} be searchable. Assume furthermore that S is unbounded, that is, with a bit of work, there exists an bijection s: \mathbb {N}\rightarrow S. Then, if a_n is an arbitrary binary sequence consider p: S \rightarrow 2 d...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.03189654275774956, 0.00946213211864233, -0.008386196568608284, 0.01988573931157589, -0.03116399049758911, -0.014063475653529167, 0.0139566445723176, -0.008096227422356606, 0.00044425282976590097, 0.009889454580843449, -0.03186601772904396, -0.004166390281170607, -0.02014518529176712, 0....
e4dd5d744e83de7f28b14fafcd656faa3dc3b761
subsection
82
223
The Fan Theorems
As a way to re-capture the unit interval's compactness—that is cover compactness—which was lost when rejecting the law of excluded middle, L.E.J. Brouwer made generous use of the fan theorem. Since he also made free use of the principle of continuous choice the complexity of the sets involved did not make a difference ...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.01762363687157631, 0.0318598747253418, -0.0480644628405571, 0.062010787427425385, -0.010772543027997017, -0.04330379143357277, 0.0022449155803769827, -0.000020324878278188407, -0.003818454686552286, 0.04724050313234329, -0.026153171434998512, -0.00901017989963293, -0.012344175018370152, ...
3f57c55c0ca48f8c1fb4bbfa7f9325b41065eb14
subsection
83
223
The Fan Theorems
We can now formally state the four versions of the fan theorem, that are going to be of interest to us. [leftmargin=2em,rightmargin=3em,skipabove=1em,skipbelow=1em, innerleftmargin=-1em,innerrightmargin=0em, nobreak=true, linecolor=blueish, linewidth=5pt, bottomline=false, topline=false, rightline=false, backgroundcolo...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.004430084954947233, 0.03437227010726929, -0.04359111934900284, 0.03846275061368942, -0.013156702741980553, -0.03611224889755249, -0.015156155452132225, 0.009165429510176182, 0.030113892629742622, 0.045911092311143875, -0.034311216324567795, -0.0026366827078163624, 0.02829759567975998, 0...
5a4caa91b8c9657b8953c364926a132d3ea39b7f
subsection
84
223
The Fan Theorems
Since \overline{\alpha }M \in B, in particular, \overline{\alpha }M \in B_{M+{w}}. Since {w} \leqslant (M + {w}) - M, we have \overline{\alpha }M \ast w \in C^\prime , and since w was arbitrary that means that \overline{\alpha }M \in C. Thus C is a uniform bar.[PR:FAN]FAN_{\Delta }, and therefore all of the fan theorem...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ 0.009844415821135044, 0.013690605759620667, -0.051526740193367004, -0.0077839563600718975, 0.00012567845988087356, -0.02786961756646633, 0.0024305786937475204, -0.006387423258274794, 0.036996688693761826, 0.026877544820308685, -0.04523852467536926, -0.008203679695725441, 0.01593421772122383,...
c814d612ea237831c669e3780478042fced61be1
subsection
85
223
The Fan Theorems
Notice that some early papers on the topic have used a more refined notation: what is labeled [PR:AS]\textrm {AS}_{}^{\, } there is what we label [PR:AS]\textrm {AS}_{[0,1]}^{\, \mathbb {R}}, and which is equivalent to [PR:AS]\textrm {AS}_{[0,1]}^{\, 1}.
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ 0.0005711219855584204, 0.033836353570222855, -0.02822238765656948, 0.025567958131432533, -0.004893151577562094, -0.04970191419124603, 0.0010735949035733938, 0.04808484762907028, 0.012883138842880726, 0.02457636035978794, 0.0069716926664114, -0.02701721526682377, -0.010442283004522324, 0.00...
aae1cdd6536c1a68916a1cd75e6953ca80991731
subsection
86
223
Linking
In the following we want to establish strong links between 2^{\mathbb {N}} and [0,1]. We will first adapt Cantor's middle third set construction for our purposes. First consider a fixed p \in (0,1). LetI^{p}_{u} = [a^{p}_{u},b^{p}_{u}] = *{ (1-p) \sum _{n \leqslant {u}} p^{n-1}u(n), (1-p) \sum _{n \leqslant {u}} p^{n-1...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.02088448964059353, -0.0009558391757309437, -0.04240970313549042, 0.005945748649537563, 0.013607717119157314, -0.021189594641327858, -0.015041714534163475, 0.05781754106283188, 0.018977578729391098, 0.03347010165452957, -0.009206566959619522, 0.029061324894428253, -0.03490410000085831, -...
fa86825a9bec2afb0ae5bb8bd17397564b0ac14a
subsection
87
223
Linking
Then *{F^{p}(\alpha ) - F^{p}(\beta )} & \leqslant (1-p) \sum _{i \geqslant 1} p^{i-1}*{\alpha (i) - \beta (i)} \\ & \leqslant (1-p) \sum _{i > n} p^{i} \\ & = (1-p) p^n \sum _{i \geqslant 0} p^{i} \\ & = \frac{1-p}{1-p} p^n = p^n \ . Consider 0< p <\frac{1}{2}. We will define subsets J^{p}_{u} and positive numbers ...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ 0.00011223419278394431, -0.009658697061240673, -0.07141027599573135, 0.01107774768024683, 0.0037650607991963625, 0.008743180893361568, 0.04388374835252762, 0.010803092271089554, -0.02648893930017948, 0.005195555277168751, -0.05773856118321419, 0.010726799257099628, -0.033141691237688065, -...
5ea5a529777b12f022d8a3cc877f434c6e6f6b51
subsection
88
223
Linking
Since F(\beta ) \in I^{p}_{\overline{\beta }n} and x \in I^{p}_{\overline{\alpha }n}, by REF we have F(\beta )< x. The case \alpha <\beta can be treated analogously. To see that F^{p} is injective let \gamma \ne \beta . Now let \alpha be as constructed above for x=F^{p}(\beta ). Then the assumption that \alpha \ne \bet...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.028210632503032684, 0.01190827414393425, -0.016843989491462708, 0.024472609162330627, -0.0038238451816141605, -0.03255894407629967, 0.0429033525288105, 0.04024859145283699, 0.03481701761484146, 0.00831519439816475, -0.028500519692897797, 0.0014408553251996636, -0.04665663093328476, -0.0...
5920b8ced069a696730883e4cebcc373cde70f48
subsection
89
223
Linking
It is easy to see that therefore F^{p}(\alpha ) = x, which means we have shown surjectivity.Remark 1.2 Notice that for p=\frac{1}{2} the function F^{p} cannot be shown to be surjective, constructively, since that would be a restatement of the fact that every real number x\in [0,1] has a binary expansion and therefore e...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.04238983988761902, 0.03016728162765503, -0.014969198033213615, 0.015838967636227608, 0.018112577497959137, -0.07116854190826416, 0.0164951104670763, 0.029266994446516037, 0.011375674977898598, 0.013313583098351955, 0.007942372933030128, -0.012611663900315762, -0.039307497441768646, -0.0...
286c662415eacb87652ae0667d14923f3a3a72d3
subsection
90
223
Linking
Below, we need a slightly stronger version of this result.Definition 1.4 A map g:X \rightarrow Y between to metric spaces X and Y is called uniformly surjective if\forall {\varepsilon >0} : {\exists { \delta >0} : { \forall {x,y \in Y} : {d(x,y)<\delta \Rightarrow \exists {\alpha ,\beta \in Y } : { d(\alpha ,\beta )<\v...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.08720707148313522, 0.022091645747423172, -0.03405286744236946, 0.006949409376829863, 0.058097366243600845, -0.07567303627729416, -0.02119150198996067, 0.0063200718723237514, 0.029216505587100983, 0.02241203561425209, 0.008833606727421284, -0.008459818549454212, -0.007738941349089146, 0....
08edfb073079462beee932f55c71cd4c36af9389
subsection
91
223
Linking
But the situation is actually much worse since even a function as well behaved and canonical as F^p with p > {1}{2} doesn't have the property of mapping complete sets to complete sets.Lemma 1.7 If, for p > {1}{2}, the function F^p:2^{\mathbb {N}}\rightarrow [0,1] maps complete sets to complete sets (i.e. is a closed ma...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.04450168088078499, 0.032323237508535385, -0.05228489637374878, 0.05216280370950699, -0.009210138581693172, -0.046424590051174164, 0.019137553870677948, 0.03812249377369881, -0.02080102451145649, -0.028004314750432968, -0.014284489676356316, 0.003990805707871914, 0.009889261797070503, -0...
e45147e1f88368803dc35fe069ed57e922b6f779
subsection
92
223
Linking
The above example suggests that connectedness may play a role.Definition 1.8 We call a sequence (x_n)_{n \geqslant 1} tail-located if the distances d(x,\left\lbrace x_n, x_{n+1}, \dots \right\rbrace ) exist for every n \geqslant 1 and x \in \mathbb {R}.Lemma 1.9 If (x_n)_{n \geqslant 1} is a sequence of real numbers t...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.012936299666762352, 0.010739569552242756, -0.014377903193235397, 0.0044697355479002, -0.017253484576940536, 0.0008194833062589169, 0.005957104731351137, 0.004412529058754444, -0.022516483440995216, 0.042073484510183334, -0.026559077203273773, -0.011410792358219624, -0.010632784105837345, ...
640123fc34e33a18af5434ef53b76850ac2c8657
subsection
93
223
Linking
Hencew_n \in 2^{\ast }\Rightarrow *{F^{{1}{2}}(v_n) - x_n} < 2^{-n+1} \for all n \in \mathbb {N}. Since *{v_n} = n for all n, the set D=\left\lbrace v_{1}, v_{2}, \dots \right\rbrace \cap 2^{\ast } is decidable. Therefore the setB = \mbox{$\left\lbrace \,u \in 2^{\ast } \, | \,\lnot \exists {w \in 2^{\ast }} : {u \ast ...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ 0.00012317253276705742, 0.025595083832740784, -0.03904128074645996, 0.024129891768097878, -0.009386390447616577, -0.010966051369905472, -0.021306343376636505, 0.03275316208600998, 0.015521884895861149, 0.015483728609979153, -0.011370505206286907, 0.000009717870852909982, 0.009111667051911354...
a75b6083329088090e1dcae2c5c7eb9fddc837f0
subsection
94
223
Linking
Assume that (x_n)_{n \geqslant 1} is tail-located, and let u \in 2^{\ast } be arbitrary. Let a,b be the endpoints of F^{{1}{2}}(B_u) that is a = F^{{1}{2}}(u) and b =F^{{1}{2}}(u\ast 1 \ast 1 \ast \dots ).That is with the notation of Section a=a^{{1}{2}}_u and b=b^{{1}{2}}_u. Choose N and \delta >0 such that x_n is bou...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.014595651999115944, 0.006054182071238756, -0.010605309158563614, -0.004810537677258253, -0.005062318406999111, 0.004463385324925184, 0.0004232109640724957, 0.002668494125828147, 0.0003850623616017401, 0.05087496340274811, -0.017212646082043648, -0.013840310275554657, 0.013199413195252419,...
ced109ef6b355b03e08947b1341f067e05d2d16e
subsection
95
223
Linking
Let \eta : \mathbb {N}\rightarrow 2^{\ast } be a bijection. In particular, that means that we have\forall {n \in \mathbb {N}} : {\exists {m \in \mathbb {N}} : {i \geqslant m \Rightarrow *{\eta (i)} \geqslant n}} \ .We may also assume that i \leqslant j \Rightarrow *{\eta (i)} \leqslant *{\eta (j)}.The function mapping ...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.015477639622986317, 0.03179438039660454, -0.03074168786406517, -0.02073347568511963, -0.009718339890241623, -0.013532445766031742, 0.0035433038137853146, -0.02135898917913437, 0.020977579057216644, 0.01013789139688015, -0.031916432082653046, 0.010176032781600952, -0.0226405281573534, -0...
84cf6f6240ef411517527d70f1f407df6a5d62e6
subsection
96
223
Linking
In both cases *{x_{i} - x} > \min \left\lbrace \delta , 3^{-(n+2)} \right\rbrace for all i \geqslant m, so (x_n)_{n \geqslant 1} is eventually bounded away from every x \in [0,1].So let us tackle the three numbered assertions.Assume that (x_n)_{n \geqslant 1} is eventually bounded away from the entire set [0,1]; say x_...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.044827885925769806, 0.03201119974255562, -0.0578276664018631, -0.006633398123085499, -0.015853019431233406, -0.00646174605935812, -0.014105984009802341, 0.0008797167101874948, 0.009406532160937786, 0.010535621084272861, -0.01595982536673546, 0.003871707245707512, -0.0008210689411498606, ...
7183db219ecc33a0d38267442d013abe4626b9e9
subsection
97
223
Linking
The sets F_{n,m} are, for m \geqslant M, a finite 2^{-m}-approximation of A_n: for let i \geqslant n with \eta (i) \notin B and let j be such that \eta (j) = \overline{\eta (i)} m. By REF and REF we have n \leqslant j \leqslant k_{m}. Since B is closed under extensions \eta (j) \notin B. Hence \eta (j) \in F_{n,M} and ...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.017589176073670387, 0.01411863137036562, -0.023828526958823204, -0.014172024093568325, -0.009595482610166073, -0.03551396355032921, -0.007864024490118027, 0.029732266440987587, -0.015819579362869263, 0.005785511340945959, -0.03270701691508293, 0.0288474690169096, -0.006708447355777025, ...
8e7fddf22cc793bf4859eac32fef53d451e4ef0a
subsection
98
223
[PR:WWKL]WWKL
We start with a principle that is a weakening of [PR:FAN]FAN_{\Delta }. The so called weak weak König's lemma ([PR:WWKL]WWKL) plays a role in Simpson style reverse mathematics . The name is somewhat misleading since it is not resembling weak König's lemma (see Section ) but rather its contrapositive i.e. the fan theore...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.07365446537733078, 0.027719585224986076, -0.015682848170399666, -0.00250193290412426, 0.018871286883950233, -0.026300806552171707, 0.025202397257089615, 0.018795007839798927, 0.011068002320826054, 0.04024450480937958, -0.0220597255975008, 0.022944554686546326, -0.023829385638237, 0.0159...
6d3ff4e0f5223a9bb95bfb7e8f0fd98550b9627f
subsection
99
223
[PR:WWKL]WWKL
It seems reasonable to conjecture that WWKL has more equivalents in measure theory, which at the moment has not received much attention in constructive analysis.Proposition 2.2 [PR:WWKL]WWKL is equivalent to the following “weaker” version for every k>0 [leftmargin=2em,rightmargin=3em,skipabove=1em,skipbelow=1em, innerl...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.046510882675647736, 0.04083435609936714, -0.04132265970110893, -0.018402928486466408, -0.000005007015261071501, -0.004642695654183626, 0.020127248018980026, 0.005714673548936844, -0.00028301560087129474, 0.05096665024757385, -0.035768210887908936, 0.0007796638528816402, 0.0062144217081367...
66e7ad627b6346e9de0f97bd4d47b8a025f17310
subsection
100
223
[PR:WWKL]WWKL
Hence*{\mbox{$\left\lbrace \,u \in 2^{N+M} \, | \, u \notin B \,\right\rbrace $}} & = *{ \bigcup _{i=1}^{m} \mbox{$\left\lbrace \, u_{i}w \in 2^{N+M} \, | \, w \notin B^{(i)} \,\right\rbrace $}} \\ & = \sum _{i=1}^{m}*{\mbox{$\left\lbrace \, w \in 2^{M} \, | \, w \notin B^{(i)} \,\right\rbrace $}} \\ & < m k2^{M} < k2^...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.03629447892308235, 0.01994822546839714, -0.04209426790475845, 0.002651877934113145, -0.00997411273419857, -0.013080053962767124, -0.013721083290874958, 0.020665569230914116, -0.012355079874396324, 0.036355528980493546, -0.04017117992043495, 0.00972991157323122, 0.0028827248606830835, 0....
c250b7512204d04ca6d13ed187f97ba28e94a3f1
subsection
101
223
[PR:FAN]FAN
As mentioned in the introduction [PR:FAN]FAN_{\Delta } deserves the prominence of being involved in the first “proper” equivalence of constructive reverse mathematics. It is also a fairly robust statement, as the next lemma shows.Lemma 3.1 If B is decidable bar, then there exists a decidable bar B^{\prime } that is cl...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.02395367994904518, 0.039332859218120575, -0.032253555953502655, 0.012556610628962517, -0.010946984402835369, -0.027081390842795372, 0.0037265517748892307, 0.009055101312696934, 0.024029966443777084, 0.05187421292066574, -0.03969902917742729, 0.029064815491437912, 0.0018184580840170383, ...
791897f224053831c386588689c30e457e6dd164
subsection
102
223
[PR:FAN]FAN
To see that REF implies REF let A,B be subsets such that d(a,b)>0 for all a \in A and b \in B. By *Chapter 7 Corollary 4.4 there exists surjective, uniformly continuous functions g_1:2^{\mathbb {N}}\rightarrow A and g_2:2^{\mathbb {N}}\rightarrow B. Then the function h: 2^{\mathbb {N}}\rightarrow \mathbb {R} defined by...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.06932754814624786, 0.01803370751440525, -0.03301602602005005, 0.003581567434594035, -0.011633419431746006, 0.015050974674522877, 0.006251532584428787, 0.002345754997804761, 0.02119189314544201, 0.0270200464874506, -0.047327037900686264, -0.009543217718601227, -0.004542754963040352, 0.04...
b65e7c969edef8dace3a8fe8ca557c681ae0a65d
subsection
103
223
[PR:FAN]FAN
Notice that either u_n = 0 \ast \dots \ast 0 or we can find its immediate “left” neighbour u_{L(n)} that is there exists w such that u_n=w\ast 1 \ast 0^k and u_{L(n)} = w \ast 0 \ast 1^\ell for some k,\ell \geqslant 0. We may assume that u_1 = 1 \ast \dots \ast 1. Now define a function f(0,1) \rightarrow \mathbb {R} by...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.05906721577048302, 0.042949650436639786, -0.04197282716631889, -0.030388327315449715, -0.005010029301047325, 0.040599171072244644, -0.010714517906308174, 0.004201098345220089, 0.006215794011950493, 0.010577152483165264, -0.015270478092133999, 0.04319385439157486, 0.023443732410669327, 0...
9201db591ca30a4c17582831668a3ef5940460c0
subsection
104
223
[PR:FAN]FAN
First we need a lemma, whose proof idea is based on the proof of the main result in the paper mentioned.Lemma 3.6 For every f:2^{\mathbb {N}}\rightarrow \mathbb {R} that has a continuous (functional) modulus of continuity and for every e \in \mathbb {N}, there exists a decidable bar B that is uniform only if there exi...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.013422171585261822, 0.03534479811787605, -0.02421942725777626, 0.016466768458485603, -0.00880567729473114, -0.05155212804675102, -0.038793813437223434, 0.02171660028398037, 0.011796860024333, 0.05570315569639206, -0.025562407448887825, 0.005585576873272657, -0.008530976250767708, 0.0093...
55fa5e37565db3a1bd90189264a240c95475cf54
subsection
105
223
[PR:FAN]FAN
So there exists N \in \mathbb {N} such that\forall {\alpha \in 2^{\mathbb {N}}} : { \exists {n \leqslant N} : {\overline{\alpha }n \in B} } \ .So for any \alpha \in 2^{\mathbb {N}} there is n \leqslant N such that \mu (\overline{\alpha }n\ast 000\ldots ,e ) \leqslant n \leqslant N, and hence for all \beta \in 2^{\mathb...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.03894227370619774, 0.01586989127099514, -0.03027486987411976, 0.00949904602020979, -0.0010853327112272382, 0.003791988594457507, -0.009491415694355965, 0.03277742862701416, 0.016007227823138237, 0.0410480834543705, -0.01436682976782322, 0.016175081953406334, -0.0029908642172813416, 0.02...
bfa5318e937d170fa39864d0ff8340d3affaeac4
subsection
106
223
[PR:FAN]FAN
Using countable choice we can therefore construct \tau : \mathbb {N}\rightarrow \mathbb {N} such that\forall {\alpha , \beta \in 2^{\mathbb {N}}} : {\forall {n \in \mathbb {N}} : {\overline{\alpha }\tau (n) = \overline{\beta }\tau (n) \Rightarrow d(g(\alpha ),g(\beta )) < 2^{-n}}} \ .Furthermore, for \alpha \in 2^{\mat...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.0037920631002634764, 0.01947151869535446, -0.00040319282561540604, 0.01466467883437872, -0.005142556503415108, -0.0022107651457190514, -0.011261740699410439, 0.06268730759620667, -0.013611751608550549, 0.06830291450023651, -0.017106248065829277, 0.007275115232914686, -0.02496505156159401,...
f726489baea792caf8335274c3285c0f47a29852
subsection
107
223
[PR:FAN]FAN
Furthermore \overline{\gamma }n = \overline{\tau }n, and hence\varepsilon & > *{h(\gamma ) - h(\tau )} \\ & = *{ d(f(h(\gamma ^{e})),f(h(\gamma ^{o}))) - d(f(h(\tau ^{e})),f(h(\tau ^{o})))} \\ & = *{ d(f(h(\alpha )),f(h(\beta ))) - d(f(h(\alpha )),f(h(\alpha )))} \\ & = d(f(h(\alpha )),f(h(\beta ))) = d(f(x),f(y)) \ .T...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.020934365689754486, 0.011207208968698978, -0.00877351313829422, 0.002000742359086871, 0.016372138634324074, -0.04000721871852875, 0.01283984538167715, 0.01757754199206829, 0.05465517193078995, 0.045774850994348526, -0.019164403900504112, 0.012336322106420994, -0.0007524241227656603, 0.0...
757a542172565b0b2e24b14942a276a1f13c3003
subsection
108
223
[PR:FAN]FAN
Straightforward.Lemma 3.10 For every decidable bar B there exists a point-wise continuous, fully located function f:[0,1] \rightarrow \mathbb {R} such that f is bounded if and only if B is uniform; and vice versa.First, start with a decidable bar B that is without loss of generality closed under extension. We are goin...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.018216464668512344, 0.02999461442232132, -0.02425810508430004, 0.03890451043844223, 0.024349644780158997, -0.04659387096762657, -0.006537483073771, 0.008047893643379211, 0.032893382012844086, 0.04964520409703255, -0.026653403416275978, -0.012335018254816532, 0.011274679563939571, 0.0174...
bc93ddd4e7cc889b02f668a9a752d54a94521e69
subsection
109
223
[PR:FAN]FAN
Since F^{{2}{3}} is surjective on I_{\overline{\alpha }M} (Lemma REF ) there exists \beta \in 2^{\mathbb {N}} such that F^{{2}{3}}(\beta ) = y and \overline{\beta }M = \overline{\alpha }M. But that means thatf \circ F^{{2}{3}}(\alpha )+ *{f \circ F^{{2}{3}}(\alpha ) - f \circ F^{{2}{3}}(\beta )} > f \circ F^{{2}{3}}(\b...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.05631740763783455, 0.010569052770733833, -0.045633889734745026, 0.013415447436273098, 0.013339136727154255, -0.028692880645394325, -0.03446198254823685, 0.028265539556741714, 0.03092115744948387, 0.022496439516544342, -0.03577452898025513, 0.005536352284252644, -0.026708798483014107, 0....
d0d7c04a75dbd6c511ae12ff0efbd5e0cbcd4e91
subsection
110
223
[PR:FAN]FAN
Every point-wise continuous mapping of [0, 1] into a metric space is uniformly sequentially continuous.Even though the equivalence {[PR:FAN]{\textrm {FAN}_{c}} \iff [PR:AS]{\textrm {AS}_{[0,1]}^{\, \mathbb {R}}}} has been shown in it also follows from Lemmas REF and REF . For the equivalence between [PR:AS]\textrm {AS}...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.03331971913576126, 0.033228181302547455, -0.037347376346588135, -0.029490390792489052, 0.028407195582985878, -0.019390733912587166, 0.007502276450395584, 0.005789758637547493, 0.03914761543273926, 0.0442127026617527, -0.026134010404348373, -0.020870592445135117, 0.0002743746736086905, 0...
0e4689008e04da2479ce4abaf9cee317a2297830
subsection
111
223
[PR:FAN]FAN
But by the choice of M, also for any \beta we have g(\overline{\alpha }(2M) \ast \beta ) = g(\alpha ), and hence g is point-wise continuous. By our assumption it is therefore uniformly continuous, which means we can find an M as above which is independent of \alpha , which immediately gives us uniform continuity of f.F...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.01985146850347519, 0.03976397216320038, -0.025222504511475563, -0.0042647854425013065, -0.01230608019977808, -0.018340865150094032, 0.002454731147736311, 0.0220334529876709, 0.043181903660297394, 0.03933672979474068, -0.04870552569627762, 0.0023116813972592354, -0.0012845853343605995, 0...
96d734afbc2c18abe90ae299350b897d86fe16f0
subsection
112
223
[PR:FAN]FAN
Then the convergence is uniform.One direction follows from the fact that [PR:FAN]FAN_{c} implies [PR:FAN]FAN_{\Delta }, that [PR:FAN]FAN_{c} implies that a point-wise continuous function is uniformly continuous (see REF of REF ), so we can use Proposition REF .REF .For the other direction, by the previous proposition, ...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.021256493404507637, 0.05447643995285034, -0.04471035301685333, 0.01641923002898693, 0.006920186337083578, -0.02879468910396099, -0.021302271634340286, 0.024842476472258568, 0.030503753572702408, 0.0618925578892231, -0.027436593547463417, 0.013283400796353817, 0.006096173077821732, 0.023...
da24d8cf927ca3b66e91b60521e060e6244f1e5d
subsection
113
223
[PR:FAN]FAN
The unproven (and probably false) assumption that [PR:FANst]FAN_{\textrm {stable}}  and [PR:FAN]FAN_{\smash{\Pi ^{0}_{1}}} are equivalent can be explained by Lemma REF taken together with the following observation.Proposition 6.1 If a stable bar B is closed under extensions, then B is a \Pi _{1}^{0}-bar.This proof is b...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.010500287637114525, 0.019337013363838196, -0.03809406980872154, -0.0014327246462926269, 0.02509080432355404, -0.026296505704522133, 0.02531973458826542, 0.014697350561618805, 0.038521405309438705, 0.028280572965741158, -0.02348829060792923, 0.021382126957178116, -0.014109762385487556, 0...
dc0699bfb6db75fe0a39a04e052f6fab7888a9bc
subsection
114
223
[PR:FAN]FAN
Notice that it would be enough to show that the closure (under extensions) of a stable bar is stable.Our first [PR:FAN]FAN_{\smash{\Pi ^{0}_{1}}}-equivalence is a sequential version of REF .REF .Proposition 6.2 [PR:FAN]FAN_{\smash{\Pi ^{0}_{1}}} is equivalent to the following statement:Every equi-continuous, and equi-...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.03649285435676575, 0.033289048820734024, -0.032312653958797455, 0.008490080945193768, -0.00012199008779134601, -0.03612670674920082, 0.02892577461898327, 0.019283849745988846, 0.016080046072602272, 0.050131905823946, -0.011076008901000023, 0.017803996801376343, -0.01411199476569891, 0.0...
a71293c63a8176650dbf5ad6d6f50323c4c36763
subsection
115
223
[PR:FAN]FAN
For any k \in \mathbb {N} and w \in 2^{\ast } we get thatf_{k}(\overline{\alpha }K \ast w ) & > f_{k}(\alpha ) - *{f_{k}(\overline{\alpha }K \ast w) - f_{k}(\alpha )} \ , \\ & > 2^{-(N-1)} - 2^{- N} \\ & > 2^{-N} > 2^{-K} \ .Hence \overline{\alpha }K \in B_{n,k}, since case REF is ruled out. Therefore B is a bar. By co...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.018612051382660866, 0.028314726427197456, -0.01099178846925497, -0.011060439981520176, -0.016537263989448547, 0.0010497883195057511, 0.025339849293231964, 0.031365882605314255, 0.005186964757740498, 0.03710205480456352, -0.03170150890946388, 0.04149571806192398, -0.017650935798883438, 0...
37ce189eb56dd34db78f42493873e971d526da78
subsection
116
223
[PR:FAN]FAN
Since the sets B_{k} are closed under extensions also \overline{\alpha }N \in B_{k} for all n \in \mathbb {N} and \alpha \in 2^{\mathbb {N}}. Therefore \overline{\alpha }N \in B for all \alpha \in 2^{\mathbb {N}}, which means B is uniform.Proposition 6.3 The following are equivalent to [PR:FAN]FAN_{\smash{\Pi ^{0}_{1}}...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.032164037227630615, 0.025267383083701134, -0.02931077405810356, -0.01715008355677128, -0.00384122203104198, -0.0365278460085392, 0.01774514839053154, 0.009902494959533215, 0.03283539041876793, 0.018477536737918854, -0.03744333237409592, 0.03439171612262726, -0.0008048638119362295, 0.034...
74961807b4f3fce181b89371cfe3524b41ec5ee7
subsection
117
223
[PR:FAN]FAN
A proof can be found in .Proposition 6.5 [PR:FAN]FAN_{\smash{\Pi ^{0}_{1}}} is equivalent to the statement that every equi-continous sequence of functions [0,1] \rightarrow \mathbb {R} is uniformly equi-continuous.It seems feasible to also prove this theorem for functions functions of type 2^{\mathbb {N}}\rightarrow \m...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.06293049454689026, 0.010033171623945236, -0.022324761375784874, -0.004097196273505688, 0.009331231005489826, -0.0328080914914608, -0.028932157903909683, 0.00988820567727089, 0.023301374167203903, 0.04403913766145706, 0.009773759171366692, 0.005104328505694866, -0.028489630669355392, 0.0...
9e560db5ac5de487b875fb7affe878a49557f291
subsection
118
223
[PR:FAN]FAN
Since g^{-1}(U_i) is open there exists n such that \overline{\alpha }n \ast \beta \in g^{-1}(U_i) for all \beta \in 2^{\mathbb {N}}. So B is a bar. Applying [PR:FAN]FAN_{\textrm {full}} yields n such that u \in B for all u \in 2^n. That means we can find finitely many i_u such that (g^{-1}(U_{i_u}))_{u \in 2^n} covers ...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.03653567656874657, 0.04279283061623573, -0.02653948962688446, -0.0005160244763828814, 0.0317130871117115, -0.040595196187496185, -0.013636017218232155, 0.02493704855442047, 0.0013181992108002305, 0.02452499233186245, -0.011301030404865742, 0.0032602061983197927, -0.020267074927687645, 0...
97ca13aa38c5657d1dbbc0970ba7689fc1c16028
subsection
119
223
[PR:UCT]UCT
The uniform continuity theorem is the standard first step in numerous theorems of classical analysis. It states: [leftmargin=2em,rightmargin=3em,skipabove=1em,skipbelow=1em, innerleftmargin=-1em,innerrightmargin=0em, nobreak=true, linecolor=blueish, linewidth=5pt, bottomline=false, topline=false, rightline=false, backg...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.04619259014725685, 0.028374575078487396, -0.05857976898550987, 0.024011602625250816, 0.00887849647551775, -0.03905317932367325, -0.0054994807578623295, 0.0029881021473556757, 0.021753842011094093, 0.04640616104006767, -0.013638102449476719, 0.013531317003071308, 0.01836719922721386, 0.0...
9d7892144e111a03a8449b08018d55b4a2a507f4
subsection
120
223
[PR:UCT]UCT
Somehow, just the fact that there are countably many of them suffices.Proposition 5.4 [PR:UCT]UCT is equivalent to C([0,1]) being separable.More precise: [PR:UCT]UCT is equivalent to the statement that there exists a sequence of point-wise continuous functions f_n:[0,1] \rightarrow \mathbb {R} such that for all \varep...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.001168942777439952, 0.013432353734970093, -0.030953146517276764, 0.024805231019854546, 0.0026124820578843355, -0.034538157284259796, -0.038290977478027344, 0.005564396269619465, 0.0007942327065393329, 0.032890576869249344, -0.010510950349271297, -0.01858104020357132, 0.010213470086455345,...
f545174b796d6c08cf69f0f2b2798b66dd2848b7
subsection
121
223
[PR:UCT]UCT
It is not too surprising that we can also prove the following version.Proposition (5.5½ version of Dini's theorem) [PR:UCT]UCT is equivalent to the statement that if (f_n)_{n \geqslant 1}:[0,1] \rightarrow \mathbb {R} is a decreasing sequence of point-wise continuous functions converging point-wise to a point-wise cont...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.037960510700941086, 0.04738960787653923, -0.023771090433001518, 0.008246646262705326, -0.015448157675564289, -0.013670666143298149, -0.015127751044929028, 0.004153837915509939, 0.028958620503544807, 0.04583334922790527, -0.034329239279031754, -0.0009435772662982345, -0.017378224059939384,...
9f3d54521ce04ddbad38d99eec09a3c63a15ef38
subsection
122
223
Comparing the Fan Theorems
The differences between the fan theorems are overall very subtle and often confusingly minute. Since many of the results in this section are variations of each other, we hope that the following table might highlight some of the differences.1mylightgray [Table: NO_CAPTION]The following abbreviations are used: 2pwc: poin...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.05558645352721214, -0.00033463991712778807, -0.0495457760989666, -0.01255424041301012, -0.02251525968313217, -0.11416274309158325, 0.0010096400510519743, 0.017649156972765923, 0.02193559892475605, 0.03444407507777214, -0.0067423745058476925, -0.02817458286881447, -0.019464410841464996, ...
d417fd4e59c22af566983b221cd5e81595d34954
subsection
123
223
[PR:BDN]BD-N and Below
Future work: include Together with Weak Markov's principle (Section ), [PR:BDN]BD-N occupies a special and rare place in constructive mathematics: it is accepted in CLASS, in INT, as well as in RUSS. However, it is not accepted in BISH. One might think that after reading Proposition REF , which says that [PR:BDN]BD-N ...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.024852298200130463, 0.0003082222829107195, -0.0023818693589419127, -0.011121747083961964, -0.0005458847736008465, 0.007094118278473616, 0.020977230742573738, 0.02945966087281704, 0.009191841818392277, 0.040276285260915756, -0.042351122945547104, -0.010526755824685097, 0.018520988523960114...
9270fbd162b343597f1b4bcb7bcf755ba9b9f69c
subsection
124
223
[PR:BDN]BD-N
A subset S of \mathbb {N} is pseudobounded if\lim _{n \rightarrow \infty } \frac{s_n}{n} = 0for each sequence (s_n)_{n \geqslant 1} in S. This is equivalent to assuming that for every sequence (s_n)_{n \geqslant 1} in S we haves_n < neventually.Trivially, every bounded set is pseudobounded, but the converse is more sub...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.03756332024931908, 0.0038581739645451307, -0.0380515493452549, 0.012068474665284157, -0.008994141593575478, -0.032742030918598175, 0.0037361159920692444, -0.0074798609130084515, 0.04330004006624222, 0.058038532733917236, -0.06057123467326164, 0.013861200772225857, -0.009627317078411579, ...
5afdabf212ac4e21286c715c1114bcdcccc19974
subsection
125
223
[PR:BDN]BD-N
Every sequentially continuous map f:\mathbb {N}^{\mathbb {N}}\rightarrow \mathbb {N} is locally bounded.[PR:BDN]{\textrm {BD-N}} \iff \ref {BDNequiv2} is shown in . Moreover, it is clear that REF \Rightarrow REF , and that REF \Rightarrow REF , so it remains to show that REF \Rightarrow [PR:BDN]BD-N. Let A =\left\lbrac...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.05746623873710632, 0.01401559729129076, -0.03068629838526249, -0.014343670569360256, 0.00934627465903759, -0.0053903209045529366, -0.013786708936095238, 0.009949013590812683, 0.02391120418906212, 0.020813580602407455, -0.05877853184938431, 0.019012993201613426, -0.05343780294060707, 0.0...
ea5ef6340221bf37da1215f4d60ca03adfb77f37
subsection
126
223
[PR:BDN]BD-N
That means that \max \left\lbrace a_1, \dots , a_M, M+1 \right\rbrace is an upper bound of A and therefore [PR:BDN]BD-N holds.Proposition 1.2 The following are equivalent to [PR:BDN]BD-N.Every uniformly sequentially continuous mapping of a separable metric space into a metric space is uniformly continuous. Every unif...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.04597153887152672, 0.002566057490184903, -0.028541427105665207, -0.0359896719455719, -0.004697125405073166, -0.006402742583304644, 0.004044640809297562, 0.01052369736135006, 0.04273582622408867, 0.026526737958192825, -0.06581317633390427, 0.03736332431435585, -0.024969933554530144, 0.01...
9421e8d5ff6f8fe1c4f001380b26328e3bccde89
subsection
127
223
[PR:BDN]BD-N
But that means that for all n \geqslant N we cannot be in the first case, which means that we must have f(\alpha _n) = f(\beta _n). So f is uniformly sequentially continuous.That means that if can apply REF to get that f is locally bounded, and continue as in the proof of Proposition REF .We can also show that \ref {BD...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.06603806465864182, 0.048765629529953, -0.0017957149539142847, -0.010780012235045433, -0.003026871709153056, -0.015853406861424446, -0.009826365858316422, 0.008064028806984425, 0.022826464846730232, 0.03485003113746643, -0.035216230899095535, 0.027312414720654488, -0.03988528251647949, 0...
849c830d08d5764e313014f00c81bd398db18597
subsection
128
223
[PR:BDN]BD-N
Given \gamma \in \mathbb {N}^{\mathbb {N}}, we can slice up \gamma into countably many sequences and turn it into a double sequence (\gamma ) : \mathbb {N}\times \mathbb {N}\rightarrow \mathbb {N} defined by(\gamma ) (m,n) = \gamma (\varphi (m,n)) \ .We can also zip a double indexed sequence \sigma :\mathbb {N}\times \...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.04671117663383484, 0.017985785380005836, -0.006048654671758413, 0.026299824938178062, 0.029640696942806244, -0.02103680931031704, -0.007574166636914015, 0.031578097492456436, 0.015331394970417023, 0.03209676966071129, -0.034171465784311295, 0.005777876358479261, -0.03804626688361168, 0....
78909f9a2969c76473dbeac05ce18813fca644c3
subsection
129
223
[PR:BDN]BD-N
Let \mu , \eta such that \overline{\mu }(L) = \overline{\eta }(L) , but f(\mu ) \ne f(\eta ). Now consider the following sequence of sequences:\underbrace{000\ldots ,000\ldots , \dots , 000\ldots }_{2M}, \underbrace{\mu , \eta , \mu , \eta , \dots , \mu , \eta }_{2K}, 000\ldots , 000\ldots , \dots \ .If we combine thes...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.029387488961219788, 0.045134056359529495, -0.02873138152062893, -0.014670857228338718, -0.004348616115748882, -0.003129859222099185, 0.01397660467773676, 0.03579597547650337, 0.03469737619161606, 0.049681030213832855, -0.053495604544878006, 0.011077526956796646, 0.005554021801799536, 0....
f639b600eacef8440c5321ff60d6feaa3ed633b5
subsection
130
223
Below [PR:BDN]BD-N
Between, approximately, 2007 and 2010 a couple of statements were considered by researchers working in CRM for which a proof in BISH could not be found, but that were all implied by [PR:BDN]BD-N. Naturally a considerable amount of time was spent trying to prove that they were in fact equivalent to [PR:BDN]BD-N. As it t...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.024483833461999893, -0.0029098386876285076, -0.05006600543856621, 0.006914203986525536, -0.0067959800362586975, -0.04854053258895874, 0.030570467934012413, -0.0014873356558382511, 0.01617000810801983, 0.055313631892204285, -0.020212510600686073, 0.005789168179035187, -0.009328263811767101...
e580d5f55e619dd90fd36dda6509ff1bd71f4596
subsection
131
223
Below [PR:BDN]BD-N
Now define the setA= \mbox{$\left\lbrace \,n \in \mathbb {N} \, | \,\exists {i,j \geqslant n} : {d(z_i,x_j) < 2^{-n}} \,\right\rbrace $} \cup \left\lbrace 0 \right\rbrace \ .The set A is easily seen to be countable; and, unsurprisingly, we are going to show that it is also pseudobounded. To this end let a_n be a sequen...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ 0.0035897991620004177, 0.04989859089255333, -0.024872997775673866, 0.0016051094280555844, -0.0018692896701395512, -0.027055107057094574, -0.03488323464989662, 0.014267639257013798, 0.020951304584741592, 0.03946108743548393, -0.028016455471515656, -0.014466012828052044, -0.0115743363276124, ...
380c907aafb817c124891a45eca88392a548d007
subsection
132
223
Below [PR:BDN]BD-N
Now there cannot be an x \in X and i \geqslant M with d(x,z_i) < 2^{-(M+2)}, since otherwise by the density we can find j \geqslant M with d(x_j,x) < 2^{-(M+2)}, which would imply that d(x_i,x_j) < 2^{-(M+1)} and therefore M+1 \in A, which is a contradiction. So for all x \in X and i \geqslant M we have d(x,z_i) \geqsl...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.020172802731394768, 0.017593979835510254, -0.03451655060052872, -0.014694711193442345, -0.00429549440741539, -0.010910403914749622, -0.028306011110544205, -0.011413960717618465, 0.013100113719701767, 0.016266420483589172, -0.04669347405433655, -0.030472833663225174, -0.019562430679798126,...
87700b8f210fadef466ecc5f6aba21898ed6ae33
subsection
133
223
Below [PR:BDN]BD-N
For the other direction notice that if f:X \rightarrow \mathbb {R} is point-wise continuous, then f(X) is also separable and that [PR:AS]{\textrm {AS}_{f(X)}^{\, 1}} follows from [PR:AS]{\textrm {AS}_{X}^{\, 1}}, whence f(X) is totally bounded and therefore, in particular, bounded (also see *Theorem 11).To see that REF...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.01201077364385128, 0.02597501501441002, -0.010606719180941582, 0.003578813746571541, -0.00035149065661244094, -0.022754846140742302, 0.0077947936952114105, 0.008271714672446251, 0.023807886987924576, 0.03357522562146187, -0.031530190259218216, -0.0018666681135073304, -0.015200420282781124...
c565bb8a87d179a8e5c211d5b585ff24116b3be0
subsection
134
223
Below [PR:BDN]BD-N
In it is shown that it cannot be proved in BISH. That REF , REF , and REF are strength-wise also between [PR:BDN]BD-N and unadorned BISH was shown in . It is unknown, whether this also holds for REF and REF , but it seems likely.Another natural principle which falls into the same category is [leftmargin=2em,rightmargin...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.07618129253387451, 0.02330305241048336, -0.0018541720928624272, -0.03290201723575592, -0.01663413643836975, 0.004711733665317297, 0.007775314152240753, 0.012567166239023209, 0.018450157716870308, 0.01805337890982628, -0.049658238887786865, 0.0067871855571866035, -0.027881253510713577, 0...
1144425cc93cf43ed767eae8bc003ceabc852bb0
subsection
135
223
Below [PR:BDN]BD-N
Moreover, it even seems impossible to get an equivalence analogous to the one of Proposition REF .Proposition 2.4 [PR:wBDN]wBD-N implies that every uniformly sequentially continuous mapping f:2^{\mathbb {N}}\rightarrow \mathbb {N} is uniformly continuous.This follows easily from the next lemma, or alternatively, from ...
{ "cite_spans": [] }
1804.05495
Constructive Reverse Mathematics
[ "Hannes Diener" ]
[ "math.LO" ]
2,018
en
Mathematics
[ -0.04150804877281189, 0.03821181878447533, -0.04080607369542122, -0.010346490889787674, -0.0012570681283250451, -0.00048117671394720674, -0.015626559033989906, 0.009415612556040287, 0.007675936911255121, 0.0363805815577507, -0.027956891804933548, 0.026613984256982803, 0.004826073534786701, ...