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UQ Validated Questions - 25 questions passed UQ validation

Suppose that is a finite group and that it acts on a finite dimensional complex vector space .

For each we may consider the subspace of spanned by the eigenv...

Science
mathoverflow
Needs Human Verification
Answered on 8/1/2025

Model Answer:

This is an excellent and carefully constructed question. The cohomology class you've defined is a well-known object in the context of equivariant K-theory and index theory, often appearing as a component of an equivariant Chern character. Let's break down its identity.

Summary of the Identification

The cohomology class can be identified as follows: for each conjugacy class of an element , its component in is the first Chern class of a...

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Hopf-like monoid in 𝕖𝕥

I am looking for a nontrivial example of the following:

Let a monoid be given with unit , and two of its distinguished disjoint submonoids and (s.t. ), endowed with monoid homomorphisms such that ()...

Science
math
Needs Human Verification
Answered on 8/1/2025

Model Answer:

Excellent question! This gets at the heart of what makes Hopf algebras in vector space-like categories so different from similar structures in the category of sets.

As it turns out, a non-trivial example of the structure you've described cannot exist. The axioms you have laid out are strong enough to force the conclusion that and must both be the trivial monoid .

Let's walk through the proof of this.

Proof of Triviality

We are given the following premises:

  1. is a...
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I have a question regarding the time evolution of a quantity related to a Bayesian posterior.

Suppose we have binary parameter space with prior , The data generating processes are Brownian motions with parameter-determined drift:

fo...

Science
stats
Failed Human Verification
Answered on 8/1/2025

Model Answer:

Excellent question. This delves into the dynamics of Bayesian learning in a continuous-time setting, a core topic in filtering theory. Your approach using Itô's lemma is the right one, but there seems to be a subtle error in your derivation that led to the confusing conclusion about "orthogonality".

Let's break down the problem and address your questions systematically.

First, let's establish the standard framework and notation to ensure clarity.

  • States and Prior: Two states, an...
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Let be a finite group, and an integer coprime to . Then we have the following map, which is clearly not a morphism of groups in general:

This induces a linear automorphism of , the algebra of -invariant functions on under convolution, and surpr...

Science
mathoverflow
Failed Human Verification
Answered on 8/1/2025

Model Answer:

Excellent question. The fact that the power map (for coprime to ) induces an algebra automorphism on the center of the group algebra is a beautiful and deep result. The standard proof via character theory is slick but, as you note, feels somewhat indirect. You're asking for a proof that works "natively" within the group algebra itself.

Let's first establish the precise statement. Let be a finite group. The center of the group algebra , denoted $Z(\mat...

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Let be a compact symplectic manifold and let be its Fukaya category. The Hochschild cohomology of this category should be given by , at least at the level of vector spaces (the product structure should be the quantum c...

Science
mathoverflow
Failed Human Verification
Answered on 8/1/2025

Model Answer:

This is an excellent and insightful question that gets to the heart of modern homological mirror symmetry. You've correctly identified the key players and the main difficulty: the Fukaya-Seidel category is generally not Calabi-Yau, so its Hochschild homology and cohomology are distinct and interesting objects.

The short answer, based on the principles of homological mirror symmetry and work by pioneers like Seidel, Abouzaid, and others, is:

**The Hochschild cohomology $HH^\bullet(FS(...

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Context The wave equation

describes waves that travel with frequency-independent speed , ie. the waves are dispersionless. The character of solutions is different in odd vs even number of spatial dimensions, . A point source in odd- creates a disturb...

Science
math
Needs Human Verification
Answered on 8/1/2025

Model Answer:

This is an excellent question that touches upon a deep connection between the symmetries of a physical system and the qualitative nature of its solutions. The answer is yes, group theory can predict the phenomenon of geometric dispersion, and your intuition about the differing structures of for odd vs. even is spot on.

The argument from a book like Howe and Tan is quite technical, relying on the machinery of harmonic analysis on symmetric spaces. Let's distill the core idea into a m...

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As part of the discussion on this question (Permutation Game Redux), a simple vertex-deletion game was proposed. The game is very simple.

Disconnect. Players alternately remove vertices from a graph . The player that produces a fully disconnected graph (i.e., a graph with no edges) is the winn...

Science
math
Needs Human Verification
Answered on 8/1/2025

Model Answer:

This is an excellent question that delves into the nuances of applying combinatorial game theory to games with non-standard winning conditions. You've already made the most crucial observations, which are the key to unlocking the game's structure. Let's formalize and extend your findings.

Summary of Key Insights

You correctly identified:

  1. The Core Problem: The standard decomposition of a game on a graph into a nim-sum ...
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Is there an irrational number containing only 's and 's with continued fraction entries less than ?

The number has continued fraction So, the maximum values is . But we are only at digits. Can we produce larger decimal ex...

Science
math
Needs Human Verification
Answered on 8/1/2025

In an example I have worked out for my work, I have constructed a category whose objects are graded -modules (where is a graded ring), and with morphisms the usual morphisms quotient the following class of morphisms: $\Sigma=\left\lbrace f\in \hom_{\text{gr}R\text{-mod}}\left(A,B\right) \ | ...

Science
math
Needs Human Verification
Answered on 8/1/2025

Model Answer:

This is an excellent question. Your construction is a specific example of a categorical localization, and it turns out to have a very clean and elegant description.

Let's break down the construction to understand its effect.

1. Analyzing the Class of Morphisms

You start with the category of graded -modules, let's call it . You are forming a new category, let's call it , by formally inverting all morphisms in the class:

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The homomorphism problem for two classes and of graphs is defined as follows:

Input: a graph in , a graph in

Output: decide if there is a homomorphism from to , i.e., a mapp...

Science
cstheory
Failed Human Verification
Answered on 8/1/2025

Model Answer:

Excellent question. This is a classic problem in parameterized complexity that sits at the intersection of structural graph theory and logic.

The short answer is: The problem is W[1]-hard, parameterized by .

Let's break down why this is the case, building on the results you've already found.

The XP Upper Bound

You correctly found the result by Grohe (from "The complexity of homomorphism and constraint satisfaction problems seen from the o...

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Suppose we have two dependent random variables and , each of which is uniform over , such that their mutual information is small, say, at most . Does this imply that there exist large sets such that the product s...

Science
cstheory
Needs Human Verification
Answered on 8/1/2025

I am interested in the following problem.

Node Multiway Cut on Planar Graphs with terminals on the outer face

  • Instance: A plane graph G, and integer k, and a set of terminals which are all incident on the outer face of G.
  • Question: Is there a set of vertices $X \subs...
Science
cstheory
Failed Human Verification
Answered on 8/1/2025

Base change for

This is a direct follow-up to Conjecture on irrational algebraic numbers.

Take the decimal expansion for but now think of it as the base expansion of some number Is there an easy...

Science
mathoverflow
Failed Human Verification
Answered on 8/1/2025

Model Answer:

This is an excellent and notoriously difficult question. The short answer is:

This is a famous open problem. There is no known proof that (or any for ) is transcendental. It is, however, widely conjectured to be true.

Let's break down why this is so hard and what is known in this area.

1. The General Conjecture (Borel's Conjecture)

Your question is a specific instance of a more general set of ideas and conjectures, often attributed to Émile Borel (a...

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Dry water or "powdered water" is essentially a bunch of extremely small water droplets surrounded by .

Some time ago, I was messing around and mixed some powdered graphite with water. (The graphite was obtained from a pencil, so it was not pure. Als...

Science
chemistry
Needs Human Verification
Answered on 8/1/2025

I would like to calculate the probability of ruin (or, default), i.e. where is the default time and follows the Geometric Ornstein-Uhlenbeck (O-U) process

with .

I can find closed-form soluti...

Business
quant
Needs Human Verification
Answered on 8/1/2025

Model Answer:

Excellent question. The process you're describing is a specific case of a mean-reverting Constant Elasticity of Variance (CEV) process, often called the Geometric Ornstein-Uhlenbeck (G-OU) or Geometric Mean Reversion (GMR) process.

The SDE is:

You are correct that for the Ornstein-Uhlenbeck process () and the Cox-Ingersoll-Ross (CIR) process (), closed-form or semi-closed-form solutions for first-passage time probabili...

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In MW05 the authors demonstrate so-called "in-place" amplitude amplification for QMA, exhibiting a method for Arthur to amplify his success probability without requiring any increas...

Technology
quantumcomputing
Needs Human Verification
Answered on 8/1/2025