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Large values of characters of the symmetric group

Posted on 2/20/2023
UQ ID:171
Science
MathOverflow
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For an element of a group and an irreducible character, there are two easy bounds for the character value : First, the bound by the dimension of the representation and, second, the bound by the centralizer arising from the formula .

I am interested on upper bounds for characters of the symmetric group that improve slightly on the second bound.

More specifically, fix small. I want to know for which there exists an irreducible character with .

Recall that for a permutation with cycles of size for all , so that , we have .

For example, known upper bounds for the dimension of representations of the symmetric group imply there does not exist such a character for the identity. On the other hand, such a character does exist if is an -cycle, since the right side is less than . I suspect and hope that this can only happen for containing some relatively large cycles.

I found works in the literature giving bounds for that improve on the by a multiplicative factor (Asymptotics of characters of symmetric groups related to Stanley character formula by Féray and Śniady) or a power (Characters of symmetric groups: sharp bounds and applications by Michael Larsen and Aner Shalev) but it's not obvious if it's possible to transform them into a bound of the form I need.

Keywords & Tags
co.combinatorics
rt.representation-theory
symmetric-groups
characters
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K2-Think

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Qwen2.5-32B
Sep 18, 2025, 01:50 PM

To address the question of identifying elements ( g \in S_n ) for which there exists an irreducible character ( \chi ) with ( |\chi(g)| > \sqrt{|Z(g)|} e^{-\delta \sqrt{n}} ) (where ( \delta > 0 ) is small), we analyze the structure of permutations, their centralizers, and character bounds from representation theory.

Key Observations:

  1. Centralizer Size: For a permutation ( g )...
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GPT-5

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Sep 2, 2025, 06:56 AM

Write n = ∑k k mk, where mk is the number of k-cycles of g, so |Z(g)| = ∏k (kmk mk!).

Your inequality asks for those g for which there exists some irreducible χ of Sn with |χ(g)| > √|Z(g)| e−δ√n.

There are three simple regimes to keep in mind, which together already give a reasonably sharp picture.

  1. What averaging already guarantees (for every g) By column orthogonality, ∑χ |χ(g)|^2 = |Z(g)|,...
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o3 Pro

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Aug 1, 2025, 12:00 AM

The whole problem turns on the size of the centraliser of the permutation
and on the observation that

  ∑χ |χ(g)|² = |Z(g)|  (orthogonality of characters).

Write p(n) for the number of partitions of n ( = the number of irreducible characters of S n ), and fix a constant δ>0. Put

  M(g) := maxχ |χ(g)| .

Of course M(g) ≤ √{|Z(g)|}; the question is when we can have

  M(g) > √{|Z(g)|} eˉ ...

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Gemini 2.5 Pro

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Google
Aug 1, 2025, 12:00 AM

This is an excellent question that touches upon some deep results in the asymptotic representation theory of symmetric groups. Your intuition that such characters exist only when has large cycles is spot on. We can make this intuition precise using a powerful asymptotic formula for the maximum character value on a given conjugacy class.

Summary of the Answer

The condition $|\chi(g...

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o4 mini

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OpenAI
Aug 1, 2025, 12:00 AM

Here is a fairly complete picture, which shows that nothing “mystical’’ is hiding here – the only time one can beat the naïve central‐​izer bound by even as little as a factor is when has so few cycles that its centralizer is itself of size at most . Equivalently one shows:

  1. **(Larsen–Shalev and Féray–Śniady boun...
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o3

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Aug 1, 2025, 12:00 AM

Throughout let
Z(g)=∏k k^{m_k }m_k ! be the order of the centraliser of the permutation
g=1^{m_1 }2^{m_2 }⋯ in S_n (so ∑k km_k =n) and fix a positive constant δ.
We want to know when there is an irreducible character χ of S_n such that

          |χ(g)| > √Z(g)·e^{-δ√n}.               (1)
  1. A very useful elementary observation

The number c(g)=∑k m_k of cycles of g controls ...

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Claude 3.7 Sonnet

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Anthropic
Aug 1, 2025, 12:00 AM

Analysis of Large Character Values in the Symmetric Group

The question asks when there exists an irreducible character of such that for a given permutation and small fixed .

Understanding the Condition

This condition is closely related to the formula , which sums over all irreduci...

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DeepSeek R1

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DeepSeek
deepseek-ai/DeepSeek-R1
Aug 1, 2025, 12:00 AM
<think> Okay, the user is asking about large values of characters in the symmetric group. Specifically, they want to know for which elements \( g \in S_n \) there exists an irreducible character \( \chi \) such that \( |\chi(g)| > \sqrt{|Z(g)|} e^{-\delta \sqrt{n}} \) for some small \( \delta > 0 \).

First, I need to recall some basics. For a permutation ( g ) with cycle type ( (m_1, m_2, \ld...

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Claude Opus 4

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Anthropic
Aug 1, 2025, 12:00 AM

This is an interesting question about character bounds for symmetric groups. Let me analyze what's known and what can be said about your specific bound.

The question asks: for which does there exist an irreducible character such that ?

Key Observations

  1. The bound is sharp for regular elements: When is an -cycle, w...
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