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BEGIN:VEVENT
SUMMARY:Juan Aguilera (Ghent University)
DTSTART;VALUE=DATE-TIME:20211215T163000Z
DTEND;VALUE=DATE-TIME:20211215T173000Z
DTSTAMP;VALUE=DATE-TIME:20240222T185743Z
UID:Bristol-logic-and-set-theory/1
DESCRIPTION:Title: The Pi12 Consequences of a Theory\nby Juan Aguile
ra (Ghent University) as part of Bristol Logic and Set Theory Seminar\n\n\
nAbstract\nWe define the \\Pi^1_2-norm |T| of a theory T\, an analogue of
the proof-theoretic ordinal of T for statements of complexity \\Pi^1_2. We
go over the basic theory of |T| and use it to define the \\Pi^1_2-soundne
ss ordinal of T. Then\, we characterise the recursive and admissible ordin
als which are \\Pi^1_2-soundness ordinals of some recursively enumerable e
xtension of Arithmetical Comprehension. This is joint work with Fedor Pakh
omov.\n
LOCATION:https://researchseminars.org/talk/Bristol-logic-and-set-theory/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tanmay Inamdar (Bar-Ilan University)
DTSTART;VALUE=DATE-TIME:20220616T140000Z
DTEND;VALUE=DATE-TIME:20220616T153000Z
DTSTAMP;VALUE=DATE-TIME:20240222T185743Z
UID:Bristol-logic-and-set-theory/2
DESCRIPTION:Title: From Sierpinski-type colourings to Ulam-type matrices
\nby Tanmay Inamdar (Bar-Ilan University) as part of Bristol Logic and
Set Theory Seminar\n\n\nAbstract\nUlam matrices were introduced by Ulam i
n his study of the measure problem. Ulam's construction applies to all suc
cessor cardinals Kappa\, and later Hajnal extended the construction to app
ly to some limit cardinals as well. In my talk I will show how a colouring
principle introduced by Sierpinski can be used to construct matrices with
similar applications as the matrices of Ulam and Hajnal. I will also show
how such colouring principles can be obtained from the existence of a non
-trivial C-sequence on Kappa using walks on ordinals. As a consequence\, t
he resulting matrices are more readily available than the matrices of Ulam
and Hajnal. The results I present are joint work with Assaf Rinot.\n
LOCATION:https://researchseminars.org/talk/Bristol-logic-and-set-theory/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Will Stafford (University of Bristol)
DTSTART;VALUE=DATE-TIME:20220929T113000Z
DTEND;VALUE=DATE-TIME:20220929T123000Z
DTSTAMP;VALUE=DATE-TIME:20240222T185743Z
UID:Bristol-logic-and-set-theory/3
DESCRIPTION:Title: Is the Proof-Theoretically Valid Logic Intuitionistic
?\nby Will Stafford (University of Bristol) as part of Bristol Logic a
nd Set Theory Seminar\n\n\nAbstract\nSeveral recent results bring into foc
us the superintuitionistic nature of most notions of proof-theoretic valid
ity\, but little work has been done evaluating the consequences of these r
esults. Proof-theoretic validity claims to offer a formal explication of h
ow inferences follow from the definitions of logic connectives (which are
defined by their introduction rules). This paper explores whether the new
results undermine this claim. It is argued that\, while the formal results
are worrying\, superintuitionistic inferences are valid because the treat
ments of atomic formulas are insufficiently general\, and a resolution to
this issue is proposed.\n
LOCATION:https://researchseminars.org/talk/Bristol-logic-and-set-theory/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Frank Stephan (National University of Singapore)
DTSTART;VALUE=DATE-TIME:20221020T093000Z
DTEND;VALUE=DATE-TIME:20221020T103000Z
DTSTAMP;VALUE=DATE-TIME:20240222T185743Z
UID:Bristol-logic-and-set-theory/4
DESCRIPTION:Title: Initial Segment Complexity for Measures\nby Frank
Stephan (National University of Singapore) as part of Bristol Logic and S
et Theory Seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Bristol-logic-and-set-theory/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sean Cox (Virginia Commonwealth University)
DTSTART;VALUE=DATE-TIME:20221101T123000Z
DTEND;VALUE=DATE-TIME:20221101T133000Z
DTSTAMP;VALUE=DATE-TIME:20240222T185743Z
UID:Bristol-logic-and-set-theory/5
DESCRIPTION:Title: Homological algebra\, elementary submodels\, and stat
ionary logic\nby Sean Cox (Virginia Commonwealth University) as part o
f Bristol Logic and Set Theory Seminar\n\n\nAbstract\nThe talk will focus
on the use of set-theoretic elementary submodel techniques to solve\, or p
artially solve\, some problems from homological algebra (independence of S
alce's Problem about cotorsion pairs\, and the precovering problem in Gore
nstein Homological Algebra).\n
LOCATION:https://researchseminars.org/talk/Bristol-logic-and-set-theory/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sam Coskey (Boise State University)
DTSTART;VALUE=DATE-TIME:20221115T123000Z
DTEND;VALUE=DATE-TIME:20221115T133000Z
DTSTAMP;VALUE=DATE-TIME:20240222T185743Z
UID:Bristol-logic-and-set-theory/6
DESCRIPTION:Title: Jumps in the Borel complexity hierarchy\nby Sam C
oskey (Boise State University) as part of Bristol Logic and Set Theory Sem
inar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/Bristol-logic-and-set-theory/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Minh Tran (National University of Singapore)
DTSTART;VALUE=DATE-TIME:20230308T163000Z
DTEND;VALUE=DATE-TIME:20230308T173000Z
DTSTAMP;VALUE=DATE-TIME:20240222T185743Z
UID:Bristol-logic-and-set-theory/7
DESCRIPTION:Title: Toward classifying the reducts of the complex fields<
/a>\nby Minh Tran (National University of Singapore) as part of Bristol Lo
gic and Set Theory Seminar\n\n\nAbstract\nWe will discuss some recent prog
ress on the problem of classifying the reducts of the complex field (with
named parameters and up to interdefinability). The tools we use include th
e recent solutions of the Restricted Trichotomy Conjecture in characterist
ic 0 and a generalized sumproduct result from additive combinatorics. (Joi
nt with Benjamin Castle)\n
LOCATION:https://researchseminars.org/talk/Bristol-logic-and-set-theory/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Juan Aguilera (University og Ghent)
DTSTART;VALUE=DATE-TIME:20230322T140000Z
DTEND;VALUE=DATE-TIME:20230322T153000Z
DTSTAMP;VALUE=DATE-TIME:20240222T185743Z
UID:Bristol-logic-and-set-theory/8
DESCRIPTION:Title: A generalization of Borel determinacy\nby Juan Ag
uilera (University og Ghent) as part of Bristol Logic and Set Theory Semin
ar\n\n\nAbstract\nWe present a theorem which is\, in some sense\, the prov
ably optimal generalization of Martin's Borel determinacy for infinite gam
es on integers. \n\nPlease see below or the seminar webpage https://www.br
istolmathsresearch.org/seminar/juan-aguilera-3 for the zoom link.\n
LOCATION:https://researchseminars.org/talk/Bristol-logic-and-set-theory/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Beatrice Pitton (University of Lausanne)
DTSTART;VALUE=DATE-TIME:20230523T123000Z
DTEND;VALUE=DATE-TIME:20230523T133000Z
DTSTAMP;VALUE=DATE-TIME:20240222T185743Z
UID:Bristol-logic-and-set-theory/9
DESCRIPTION:Title: Definable subsets of the generalized Cantor and Baire
spaces\nby Beatrice Pitton (University of Lausanne) as part of Bristo
l Logic and Set Theory Seminar\n\n\nAbstract\nGeneralized descriptive set
theory (GDST) aims at developing a higher analogue of classical descriptiv
e set theory in which $\\omega$ is replaced with an uncountable cardinal $
\\kappa$ in all definitions and relevant notions. In the literature on GDS
T it is often required that $\\kappa^{<\\kappa}=\\kappa$\, a condition equ
ivalent to κ regular and $2^{<\\kappa}=\\kappa$. In contrast\, in this pa
per we use a more general approach and develop in a uniform way the basics
of GDST for cardinals $\\kappa$ still satisfying $2^{<\\kappa}=\\kappa$ b
ut independently of whether they are regular or singular. This allows us t
o retrieve as a special case the known results for regular $\\kappa$\, but
it also uncovers their analogues when $\\kappa$ is singular. We also disc
uss some new phenomena specifically arising in the singular context (such
as the existence of two distinct yet related Borel hierarchies)\, and obta
in some results which are new also in the setup of regular cardinals\, suc
h as the existence of unfair Borel∗ codes for all Borel∗ sets. This is
joint work with Luca Motto Ros.\n\nThe zoom link for this talk is https:/
/bristol-ac-uk.zoom.us/j/93185058773.\n
LOCATION:https://researchseminars.org/talk/Bristol-logic-and-set-theory/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bokai Yao (University of Notre Dame)
DTSTART;VALUE=DATE-TIME:20230523T140000Z
DTEND;VALUE=DATE-TIME:20230523T150000Z
DTSTAMP;VALUE=DATE-TIME:20240222T185743Z
UID:Bristol-logic-and-set-theory/10
DESCRIPTION:Title: Forcing with Urelements\nby Bokai Yao (Universit
y of Notre Dame) as part of Bristol Logic and Set Theory Seminar\n\n\nAbst
ract\nI will begin by isolating a hierarchy of axioms based on ZFCU_R\, wh
ich is ZFC set theory (with Replacement) modified to allow a class of urel
ements. For example\, the Collection Principle is equivalent to the Reflec
tion Principle over ZFCU_R\, while it is folklore that neither of them is
provable in ZFCU_R.\n\nI then turn to forcing over countable transitive mo
dels of ZFU_R. A forcing relation is full just in case whenever a forcing
condition p forces an existential statement\, p also forces some instance
of that statement. According to the existing approach\, forcing relations
are almost never full when there are urelements. I introduce a new forcing
machinery to address this problem. I show that over ZFCU_R\, the principl
e that every new forcing relation is full is equivalent to the Collection
Principle. Furthermore\, I show how forcing is able to preserve\, destroy
and resurrect the axioms in the hierarchy I introduced. In particular\, th
e Reflection Principle is “necessarily forceble” in certain models of
ZFCU_R. In the end\, I will consider how the ground model definability can
fail when the ground model contains a proper class of urelements.\n\nThe
zoom link for this talk is https://bristol-ac-uk.zoom.us/j/93185058773.\n
LOCATION:https://researchseminars.org/talk/Bristol-logic-and-set-theory/10
/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Shay Logan (Kansas State University)
DTSTART;VALUE=DATE-TIME:20231004T150000Z
DTEND;VALUE=DATE-TIME:20231004T160000Z
DTSTAMP;VALUE=DATE-TIME:20240222T185743Z
UID:Bristol-logic-and-set-theory/11
DESCRIPTION:Title: Varieties of Variable Sharing or: How I Stopped Worr
ying and Learned to Love Nonuniform Substitutions\nby Shay Logan (Kans
as State University) as part of Bristol Logic and Set Theory Seminar\n\nAb
stract: TBA\n
LOCATION:https://researchseminars.org/talk/Bristol-logic-and-set-theory/11
/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jonathan Schilhan (University of Leeds)
DTSTART;VALUE=DATE-TIME:20231129T153000Z
DTEND;VALUE=DATE-TIME:20231129T170000Z
DTSTAMP;VALUE=DATE-TIME:20240222T185743Z
UID:Bristol-logic-and-set-theory/12
DESCRIPTION:Title: A geometric condition for Dependent Choice\nby J
onathan Schilhan (University of Leeds) as part of Bristol Logic and Set Th
eory Seminar\n\nLecture held in G.06 Fry Building.\n\nAbstract\nThe method
of permutation models is used to prove basic independence results related
to the Axiom of Choice over set theory with atoms. While it is already mo
re than 100 years old (introduced in 1922)\, arguments that show whether D
C holds in a permutation model have always been either ad-hoc or relied si
mply on the filter of groups being countably closed. We have succeeded in
crystallising a condition which characterizes precisely when DC holds or n
ot. Under some circumstances\, the same characterization still holds for s
ymmetric extensions.\n
LOCATION:https://researchseminars.org/talk/Bristol-logic-and-set-theory/12
/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Merlin Carl (Europa-Universität Flensburg)
DTSTART;VALUE=DATE-TIME:20231206T153000Z
DTEND;VALUE=DATE-TIME:20231206T163000Z
DTSTAMP;VALUE=DATE-TIME:20240222T185743Z
UID:Bristol-logic-and-set-theory/13
DESCRIPTION:Title: Space and time complexity for Infinite Time Turing M
achines\nby Merlin Carl (Europa-Universität Flensburg) as part of Bri
stol Logic and Set Theory Seminar\n\n\nAbstract\nInfinite Time Turing Mach
ines (ITTMs)\, defined in the classical paper by Hamkins and Lewis\, allow
Turing machines to run for transfinite ordinal time. One can then general
ize notions of time (Schindler) and space (Löwe) complexity to this setti
ng. Löwe's "bold conjecture" was whether the two notions are non-triviall
y connected\, i.e.\, whether low space complexity implies low time complex
ity. In our talk\, we will show that this conjecture fails. Showing this w
ill\, however\, leads naturally to a systematic study of decision and semi
-decision times on ITTMs\, which was done in joint work with Philipp Schli
cht and Philip Welch and led to connections with descriptive set theory an
d generalizations to the theory of ranks.\n
LOCATION:https://researchseminars.org/talk/Bristol-logic-and-set-theory/13
/
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