Dear all,

Today Shay Logan  will give a Zoom talk entitled 'Varieties of
Variable Sharing or: How I Stopped Worrying and Learned to Love
Nonuniform Substitutions' at the Bristol Logic and Set Theory Seminar at 
4pm. Details below.

Best,

Johannes






---------- Forwarded message ---------
From: Philipp Schlicht <[log in to unmask]>
Date: Sun, Oct 1, 2023 at 5:06 PM
Subject: [Bristol-Logic-and-Set-Theory-Seminar] Logic and Set Theory
Seminar next Wednesday
To: [log in to unmask]
<[log in to unmask]>


Dear all,

The next talk in the Bristol Logic and Set Theory Seminar will take
place online next Wednesday, 4 October at 4:00-5:00pm.

Zoom: https://bristol-ac-uk.zoom.us/j/99309500789, Meeting ID: 993 0950 
0789.

Shay Logan (Kansas State University) will speak about 'Varieties of
Variable Sharing or: How I Stopped Worrying and Learned to Love
Nonuniform Substitutions'.

Abstract: Relevance and variable sharing have gone hand-in-hand since
the very start. The relationship in fact predates the seminal texts of
the movement, as one can see by comparing the publication dates of [1]
and [2].
But both both parties to this marriage have changed over the decades,
and the marriage looks quite different now than it did when it first
began. In particular, variable sharing results no longer play at being
quite so hard to get. This is the result of a novel way to prove
strong variable sharing results. The key bit (introduced in [3]; [4])
is the use of nonuniform substitutions. It turns out that this key bit
is key in more than one way: not only does it unlock easy proofs of
strong variable sharing results, it also opens a door behind which
hide a plethora of novel and quite unanticipated forms of variable
sharing as well. For each of these forms of variable sharing, a proof
that is not interestingly different from the proof of the main result
in [3] shows that weak-enough logics exhibit that form of variable
sharing.
Given all this, the goal of this talk is twofold. First, I’ll survey
the state of the art in order to show you how to use nonuniform
substitutions to achieve profit and fame. After that, I’ll try to
convince you that you shouldn’t feel bad about doing so.

References:
[1] Nuel D. Belnap, Entailment and relevance, Journal of Symbolic Logic,
vol. 25 (1960), no. 2, pp. 144–146.
[2] Alan Ross Anderson and Nuel D. Belnap, Entailment: The Logic of 
Relevance
and Neccessity, Vol. I, Princeton, Princeton University Press (1975).,
[3] Shay Allen Logan, Depth Relevance and Hyperformalism, Journal of
Philosophical
Logic, vol. 51 (2022), no. 4, pp. 721–737.
[4] Shay Allen Logan, Correction to: Depth Relevance and Hyperformalism,
Journal of Philosophical Logic, vol. 52 (2023), no. 4, p. 1235.

Upcoming Logic and Set Theory seminars will be announced at
https://www.bristolmathsresearch.org/events/logic-and-set-theory.

With best wishes, Philipp Schlicht, Kentaro Fujimoto and Philip Welch

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