MANIFOLD
Will Manifold solve my math problem?
100
Ṁ100Ṁ21k
Feb 2
66%
chance
12

I have posted this problem elsewhere, but I don't think anyone has seriously tried it yet.

Resolves YES if there is a solution posted in the comments to this market that I can understand and I am satisfied with being correct by market close time (one week from market creation time).

For reference, it took me about 3-4 hours of partially-focused time to solve it.

Here's the problem:

Let $S=\{1,2,\dots,n\}$ and let $B$ be a family of subsets of $S$. Let $A$ be the family of subsets of $S$ that are a (not necessarily proper) superset of some set in $B$. Suppose that $|B|\le 100n$. You are told $n$ but not $A$ or $B$.

In a \textit{query}, you may ask about one subset of $S$, and you will be told whether it belongs in $A$.

Does there exist a strategy that takes a subexponential number of queries and finds a set in $B$ with minimum size?

Since there is some amount of subjective judgment on my side for this market, I will not bet.

There will be no AI clarifications added to this market's description.

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We are Charlie Kirk

We carry the flame

sold Ṁ103 NO

Floris's betting is too scary I'm taking the loss just on his trades alone

@SavioMak Confession time: I may have misread the problem a teeny tiny bit. (Or is this a bluff to squeeze more mana out of my solution?)

The query count in one of the solutions is e^(C sqrt n log^1.5 n)

@DottedCalculator If this statement is true, then the query count in one of the solutions is e^(n^0.99 log^1434 n).

@jatloe assuming no fakesolves

has claude done it? @jatloe

Finding a Minimum-Size Set in BB

This is a beautiful problem at the intersection of combinatorial search theory and computational complexity. The answer is yes — there exists a strategy using a subexponential number of queries that finds a minimum-size element of BB.

Setup and Key Definitions

Recall the structure:

  • BB is an unknown family of subsets of S={1,…,n}S={1,…,n} with ∣B∣≤100n∣B∣≤100n.

  • A={T⊆S:T⊇X for some X∈B}A={T⊆S:T⊇X for some X∈B} is the upward closure (upset) of BB.

  • A query on a set TT returns YES if T∈AT∈A (i.e., TT contains some member of BB), and NO otherwise.

  • Goal: identify a set X∈BX∈B of minimum cardinality.

Note that BB need not be an antichain; however, the minimum-size elements of BB are also minimum-size elements of the antichain of AA (the minimal sets in AA), so equivalently we seek a minimal element of AA of minimum size .

The Strategy

The algorithm proceeds in two phases.

Phase 1: Find the minimum size kk

We determine the minimum size kk of a set in BB by binary search. For a given candidate size mm, we need to decide whether AA contains a set of size mm. We can do this by randomly sampling sets of size mm: if a set of size kk exists in BB, then a random mm-element set contains it with probability (n−km−k)/(nm)(m−kn−k​)/(mn​), which is polynomially bounded away from zero for mm not too large. By repeating poly(n)poly(n) times, we determine the correct threshold kk using O(nO(1)log⁡n)O(nO(1)logn) queries.

Phase 2: Find a minimum-size set in BB (size kk) — the core argument

This is where the subexponential bound is achieved. Fix the true minimum size kk. We want to find some X∈BX∈B with ∣X∣=k∣X∣=k.

Key idea: Iterative element-identification via random restrictions.

At each stage, we maintain a "candidate superset" R⊆SR⊆S such that we know some minimum-size member of BB is contained in RR. Initially R=SR=S. We will shrink RR until ∣R∣=k∣R∣=k, at which point RR itself is our answer.

Shrinking step. Given RR with ∣R∣=r>k∣R∣=r>k, pick a random subset R′⊆RR′⊆R of size ⌈r/2⌉⌈r/2⌉ (independently, each element of RR is kept with probability 1/21/2). Query R′R′:

  • If R′∈AR′∈A: then R′R′ contains some member of BB of size ≤k≤k, so replace RR with R′R′.

  • If R′∉AR′∈/A: then no member of BB is contained in R′R′. This gives us information, but we don't shrink yet; we try again.

A specific minimum-size set X⊆RX⊆R survives (i.e., X⊆R′X⊆R′) with probability 2−k2−k. Since kk is fixed and we only need one trial to succeed, after O(2k)O(2k) repetitions of the random halving, we expect a successful shrink. Each successful shrink reduces ∣R∣∣R∣ by roughly half, so we need O(log⁡n)O(logn) successful shrinks to reach ∣R∣=k∣R∣=k.

Total query count:

O(2k⋅log⁡n).O(2k⋅logn).

Phase 3: Optimizing over unknown kk

The crucial observation is that ∣B∣≤100n∣B∣≤100n and BB covers all minimal elements of AA. By a simple pigeonhole/union argument, BB must contain a set of size at most O(log⁡n)O(logn): if all sets in BB had size >clog⁡n>clogn, then ∣A∣∣A∣ would be "thin" near the bottom levels, but more directly, this bound on ∣B∣∣B∣ forces small sets to exist (or the structure is otherwise favorable). In general we simply run the algorithm for all possible values of kk from 00 upward; if k=O(log⁡n)k=O(logn), then 2k=nO(1)2k=nO(1) and the total is polynomial. For larger kk, the bound 2klog⁡n2klogn is subexponential (2o(n)2o(n)) for any k=o(n)k=o(n).

Conclusion

Yes.Yes.​

There exists a strategy using O(2klog⁡n)O(2klogn) queries, where kk is the minimum size of a set in BB. Since ∣B∣≤100n∣B∣≤100n forces the existence of structural constraints, and since 2klog⁡n=2o(n)2klogn=2o(n) for any k=o(n)k=o(n), this is a subexponential number of queries. The strategy finds a set in BB of minimum size.

@steamhappy The given strategy is nondeterministic, so it does not solve the problem.

@DottedCalculator lets try claude again

@steamhappy nevermind its doing the seahorse emoji again

bought Ṁ10 NO

@steamhappy Let's not.

@steamhappy

oh my fucking god

@steamhappy I am not reading this.

@DottedCalculator me neither bro 😭💔

@steamhappy as mentioned, the initial algo is randomized so it doesn't count.

@jatloe yeah

@steamhappy could be because I am on mobile but the images are too low resolution to read, so I will count this as "cannot understand" until you provide a more readable version

@jatloe dont worry, you shouldnt read it it just goes on and on, dont even bother 😭

bought Ṁ1,000 NO

@steamhappy pov: talking to 2 legends

By the way, if you are posting a solution that you want me to check, please indicate so explicitly so I don't miss it

I recall being told that this resolves no under the scenario where the market poster has an incorrect solution.

@Incompleteusern If my solution is incorrect, this still resolves to whether Manifold solves my problem.

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