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The Graduate Logic Seminar is an informal space where graduate student and professors present topics related to logic which are not necessarily original or completed work. This is a space focused principally on practicing presentation skills or learning materials that are not usually presented in a class.
The Graduate Logic Seminar is an informal space where graduate students and professors present topics related to logic which are not necessarily original or completed work. This is a space focused principally on practicing presentation skills or learning materials that are not usually presented in a class.


* '''When:''' Mondays 4p-5p
* '''When:''' Tuesdays 4-5 PM
* '''Where:''' on line (ask for code).
* '''Where:''' Van Vleck 901
* '''Organizers:''' [https://www.math.wisc.edu/~jgoh/ Jun Le Goh]
* '''Organizers:''' [https://www.math.wisc.edu/~jgoh/ Jun Le Goh]


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Sign up for the graduate logic seminar mailing list:  join-grad-logic-sem@lists.wisc.edu
Sign up for the graduate logic seminar mailing list:  join-grad-logic-sem@lists.wisc.edu


== Fall 2020 - Tentative schedule ==
== Spring 2022 ==


=== September 21 - Alice Vidrine ===
The graduate logic seminar this semester will be run as MATH 975. Please enroll if you wish to participate.


Title, abstract TBA
We plan to cover the first 9 parts of [https://blog.nus.edu.sg/matwong/teach/modelarith/ Tin Lok Wong's notes], as well as a few other relevant topics which are not covered in the notes:
* Properness of the induction/bounding hierarchy (chapter 10 of Models of Peano Arithmetic by Kaye is a good source)
* Tennenbaum's theorem (this is a quick consequence of the main theorem of part 4, so it should be combined with part 4 or part 5)
* Other facts found in chapter 1 of [http://homepages.math.uic.edu/~marker/marker-thesis.pdf David Marker's thesis].


== Spring 2020 - Tentative schedule ==
=== January 25 - organizational meeting ===


=== January 28 - Talk by visitor - No seminar ===
We will meet to assign speakers to dates.
=== February 3 - Talk by visitor - No seminar ===
=== February 10 - No seminar (speaker was sick) ===


=== February 17 - James Hanson ===
=== February 1 - Steffen Lempp ===


Title: The Topology of Definable Sets in Continuous Logic
I will give an overview of the topics we will cover:  


Abstract: We will look at the topology of certain special subsets of type spaces in continuous logic, such as definable sets. In the process we will characterize those type spaces which have 'enough definable sets' and look at some counterexamples to things which would have been nice.
1. the base theory PA^- and the induction and bounding axioms for Sigma_n-formulas, and how they relate to each other,


=== February 24 - Two short talks - Tejas Bhojraj and Josiah Jacobsen-Grocott ===
2. the equivalence of Sigma_n-induction with a version of Sigma_n-separation (proved by H. Friedman),


'''Tejas Bhojraj''' - Quantum Kolmogorov Complexity.
3. the Grzegorczyk hierarchy of fast-growing functions,


Abstract: We define a notion of quantum Kolmogorov complexity and relate it to quantum Solovay and quantum Schnorr randomness.
4. end extensions and cofinal extensions,


'''Josiah Jacobsen-Grocott''' - A Characterization of Strongly $\eta$-Representable Degrees.
5. recursive saturation and resplendency,


Abstract:
6. standard systems and coded types,
$\eta$-representations are a way of coding sets in computable linear orders that were first
introduced by Fellner in his PhD thesis. Limitwise monotonic functions have been used to
characterize the sets with $\eta$-representations as well as the sets with subclasses of
$\eta$-representations except for the case of sets with strong $\eta$-representations, the only
class where the order type of the representation is unique.


We introduce the notion of a connected approximation of a set, a variation on $\Sigma^0_2$
7. the McDowell-Specker Theorem that every model of PA has a proper elementary end extension, and
approximations. We use connected approximations to
give a characterization of the degrees with strong $\eta$-representations as well new
characterizations of the subclasses of $\eta$-representations with known characterizations.


=== March 2 - Patrick Nicodemus ===
8. Gaifman's theorem that every model of PA has a minimal elementary end extension.


Title: A Sheaf-theoretic generalization of Los's theorem
I will sketch the basic definitions and state the main theorems, in a form that one can appreciate without too much
background.


Abstract: Sheaf theory deals in part with the behavior of functions on a small open neighborhood of a point. As one chooses smaller and smaller open neighborhoods around a point, one gets closer to the limit - the "germ" of the function of the point. The relationship between the "finite approximation" (the function's behavior on a small, but not infinitesimal, neighborhood) and the "limit" (its infinitesimal behavior) is akin to the concept of reasoning with finite approximations that underlies forcing. Indeed, there is a natural forcing language that arises in sheaf theory - this is somewhat unsurprising as at a purely formal level, a sheaf is almost identical as a data structure to a Kripke model. We will demonstrate the applicability of this forcing language by giving a Los's theorem for sheaves of models.
=== February 8 - Karthik Ravishankar ===


=== March 9 - Noah Schweber ===
Title: Collection axioms


Title: Algebraic logic and algebraizable logics
We will discuss parts 1 and 2 of Wong's notes.


Abstract: Arguably the oldest theme in what we would recognize as "mathematical logic" is the algebraic interpretation of logic, the most famous example of this being the connection between (classical) propositional logic and Boolean algebras. But underlying the subject of algebraic logic is the implicit assumption that many logical systems are "satisfyingly" interpreted as algebraic structures. This naturally hints at a question, which to my knowledge went unasked for a surprisingly long time: when does a logic admit a "nice algebraic interpretation?"
=== February 15 - Karthik Ravishankar, Yunting Zhang ===


Perhaps surprisingly, this is actually a question which can be made precise enough to treat with interesting results. I'll sketch what is probably the first serious result along these lines, due to Blok and Pigozzi, and then say a bit about where this aspect of algebraic logic has gone from there.
Title: Collection axioms/The Weak König Lemma


=== March 16 - Spring break - No seminar ===
Karthik will finish part 2 of Wong's notes. Then Yunting will start on part 3 of Wong's notes.


=== '''Due to the cancellation of face-to-face instruction in UW-Madison through at least April 10, the seminar is suspended until further notice''' ===
=== February 22 - Yunting Zhang ===


Title: The Weak König Lemma


We will finish part 3 of Wong's notes.


== Fall 2019 ==
=== March 22 - Ang Li ===


=== September 5 - Organizational meeting ===
Title: The Arithmetized Completeness Theorem


=== September 9 - No seminar ===
We will discuss part 4 of Wong's notes.


=== September 16 - Daniel Belin ===
=== March 29 - Ang Li ===
Title: Lattice Embeddings of the m-Degrees and Second Order Arithmetic


Abstract: Lachlan, in a result later refined and clarified by Odifreddi, proved in 1970 that initial segments of the m-degrees can be embedded as an upper semilattice formed as the limit of finite distributive lattices. This allows us to show that the many-one degrees codes satisfiability in second-order arithmetic, due to a later result of Nerode and Shore. We will take a journey through Lachlan's rather complicated construction which sheds a great deal of light on the order-theoretic properties of many-one reducibility.
Title: The Arithmetized Completeness Theorem


=== September 23 - Daniel Belin ===
We will finish part 4 of Wong's notes.


Title: Lattice Embeddings of the m-Degrees and Second Order Arithmetic - Continued
=== April 5 - Antonio Nákid Cordero ===


=== September 30 - Josiah Jacobsen-Grocott ===
Title: Semiregular cuts


Title: Scott Rank of Computable Models
We will start on part 5 of Wong's notes.


Abstract: Infinatary logic extends the notions of first order logic by allowing infinite formulas. Scott's Isomorphism Theorem states that any countable structure can be characterized up to isomorphism by a single countable sentence. Closely related to the complexity of this sentence is what is known as the Scott Rank of the structure. In this talk we restrict our attention to computable models and look at an upper bound on the Scott Rank of such structures.
=== April 12 - Antonio Nákid Cordero/Alice Vidrine ===


=== October 7 - Josiah Jacobsen-Grocott ===
Title: Semiregular cuts/End and cofinal extensions


Title: Scott Rank of Computable Codels - Continued
We will finish part 5 of Wong's notes and then start on part 6.


=== October 14 - Tejas Bhojraj ===
=== April 19 - Alice Vidrine ===


Title: Solovay and Schnorr randomness for infinite sequences of qubits.
Title: End and cofinal extensions


Abstract : We define Solovay and Schnorr randomness in the quantum setting. We then prove quantum versions of the law of large numbers and of the Shannon McMillan Breiman theorem (only for the iid case) for quantum Schnorr randoms.
We will finish part 6 of Wong's notes.


=== October 23 - Tejas Bhojraj ===
=== May 3 - No seminar today ===


Title: Solovay and Schnorr randomness for infinite sequences of qubits - continued
== Previous Years ==
 
Unusual time and place: Wednesday October 23, 4:30pm, Van Vleck B321.
 
=== October 28 - Two short talks ===
 
'''Iván Ongay Valverde''' - Exploring different versions of the Semi-Open Coloring Axiom (SOCA)
 
In 1985, Avraham, Rubin and Shelah published an article where they introduced different coloring axioms. The weakest of them, the Semi-Open Coloring Axiom (SOCA), states that given an uncountable second countable metric space, $E$, and $W\subseteq E^{\dagger}:=E\times E\setminus \{(x, x) :x \in E\}$ open and symmetric, there is an uncountable subset $H\subseteq E$ such that either $H^{\dagger}\subseteq W$ or $H^{\dagger}\cap W=\emptyset$. We say that $W$ is an open coloring and $H$ is a homogeneous subset of $E$. This statement contradicts CH but, as shown also by Avraham, Rubin and Shelah, it is compatible with the continuum taking any other size. This classic paper leaves some questions open (either in an implicit or an explicit way):
 
- Is the axiom weaker if we demand that $W$ is clopen?
- If the continuum is bigger than $\aleph_2$, can we ask that $H$ has the same size as $E$?
- Can we expand this axiom to spaces that are not second countable and metric?
 
These questions lead to different versions of SOCA. In this talk, we will analyze how they relate to the original axiom.
 
'''James Earnest Hanson''' - Strongly minimal sets in continuous logic
 
The precise structural understanding of uncountably categorical theories given by the proof of the Baldwin-Lachlan theorem is known to fail in continuous logic in the context of inseparably categorical theories. The primary obstacle is the absence of strongly minimal sets in some inseparably categorical theories. We will develop the concept of strongly minimal sets in continuous logic and discuss some common conditions under which they are present in an $\omega$-stable theory. Finally, we will examine the extent to which we recover a Baldwin-Lachlan style characterization in the presence of strongly minimal sets.
 
=== November 4 - Two short talks ===
 
'''Manlio Valenti''' - The complexity of closed Salem sets (20 minutes version)
 
A central notion in geometric measure theory is the one of Hausdorff dimension. As a consequence of Frostman's lemma, the Hausdorff dimension of a Borel subset A of the Euclidean n-dimensional space can be determined by looking at the behaviour of probability measures with support in A. The possibility to apply methods from Fourier analysis to estimate the Hausdorff dimension gives birth to the notion of Fourier dimension. It is known that, for Borel sets, the Fourier dimension is less than or equal to the Hausdorff dimension. The sets for which the two notions agree are called Salem sets.
<br/>
In this talk we will study the descriptive complexity of the family of closed Salem subsets of the real line.
 
'''Patrick Nicodemus''' - Proof theory of Second Order Arithmetic and System F
 
A central theme in proof theory is to show that some formal system has the property that whenever A is provable, there is a proof of A in "normal form" - a direct proof without any detours. Such results have numerous and immediate consequences - often consistency follows as an easy corollary. The Curry Howard correspondence describes of equivalences between normalization of proofs and program termination in typed lambda calculi. We present an instance of this equivalence, between the proof theory of intuitionistic second order arithmetic and the second order polymorphic lambda calculus of Girard and Reynolds, aka system F.
 
=== November 11 - Manlio Valenti ===
 
Title: The complexity of closed Salem sets (full length)
 
Abstract:
A central notion in geometric measure theory is the one of Hausdorff dimension. As a consequence of Frostman's lemma, the Hausdorff dimension of a Borel subset A of the Euclidean n-dimensional space can be determined by looking at the behaviour of probability measures with support in A. The possibility to apply methods from Fourier analysis to estimate the Hausdorff dimension gives birth to the notion of Fourier dimension. It is known that, for Borel sets, the Fourier dimension is less than or equal to the Hausdorff dimension. The sets for which the two notions agree are called Salem sets.
<br/>
In this talk we will study the descriptive complexity of the family of closed Salem subsets of the real line.
 
=== November 18 - Iván Ongay Valverde ===
 
Title: A couple of summer results
 
Abstract: Lately, I have been studying how subsets of reals closed under Turing equivalence behave through the lenses of algebra, measure theory and orders.
 
In this talk I will classify which subsets of reals closed under Turing equivalence generate subfields or $\mathbb{Q}$-vector spaces of $\mathbb{R}$. We will show that there is a non-measurable set whose Turing closure becomes measurable (and one that stays non-measurable) and, if we have enough time, we will see a model where there are 5 possible order types for $\aleph_1$ dense subsets of reals, but just 1 for $\aleph_1$ dense subsets of reals closed under Turing equivalence.
 
=== November 25 - Anniversary of the signing of the Treaty of Granada - No seminar ===
 
=== December 2 - Anniversary of the Battle of Austerlitz - No seminar ===
 
=== December 9 - Anniversary of the death of Pope Pius IV - No seminar  ===
 
==Previous Years==


The schedule of talks from past semesters can be found [[Graduate Logic Seminar, previous semesters|here]].
The schedule of talks from past semesters can be found [[Graduate Logic Seminar, previous semesters|here]].

Revision as of 17:44, 2 May 2022

The Graduate Logic Seminar is an informal space where graduate students and professors present topics related to logic which are not necessarily original or completed work. This is a space focused principally on practicing presentation skills or learning materials that are not usually presented in a class.

  • When: Tuesdays 4-5 PM
  • Where: Van Vleck 901
  • Organizers: Jun Le Goh

The talk schedule is arranged at the beginning of each semester. If you would like to participate, please contact one of the organizers.

Sign up for the graduate logic seminar mailing list: join-grad-logic-sem@lists.wisc.edu

Spring 2022

The graduate logic seminar this semester will be run as MATH 975. Please enroll if you wish to participate.

We plan to cover the first 9 parts of Tin Lok Wong's notes, as well as a few other relevant topics which are not covered in the notes:

  • Properness of the induction/bounding hierarchy (chapter 10 of Models of Peano Arithmetic by Kaye is a good source)
  • Tennenbaum's theorem (this is a quick consequence of the main theorem of part 4, so it should be combined with part 4 or part 5)
  • Other facts found in chapter 1 of David Marker's thesis.

January 25 - organizational meeting

We will meet to assign speakers to dates.

February 1 - Steffen Lempp

I will give an overview of the topics we will cover:

1. the base theory PA^- and the induction and bounding axioms for Sigma_n-formulas, and how they relate to each other,

2. the equivalence of Sigma_n-induction with a version of Sigma_n-separation (proved by H. Friedman),

3. the Grzegorczyk hierarchy of fast-growing functions,

4. end extensions and cofinal extensions,

5. recursive saturation and resplendency,

6. standard systems and coded types,

7. the McDowell-Specker Theorem that every model of PA has a proper elementary end extension, and

8. Gaifman's theorem that every model of PA has a minimal elementary end extension.

I will sketch the basic definitions and state the main theorems, in a form that one can appreciate without too much background.

February 8 - Karthik Ravishankar

Title: Collection axioms

We will discuss parts 1 and 2 of Wong's notes.

February 15 - Karthik Ravishankar, Yunting Zhang

Title: Collection axioms/The Weak König Lemma

Karthik will finish part 2 of Wong's notes. Then Yunting will start on part 3 of Wong's notes.

February 22 - Yunting Zhang

Title: The Weak König Lemma

We will finish part 3 of Wong's notes.

March 22 - Ang Li

Title: The Arithmetized Completeness Theorem

We will discuss part 4 of Wong's notes.

March 29 - Ang Li

Title: The Arithmetized Completeness Theorem

We will finish part 4 of Wong's notes.

April 5 - Antonio Nákid Cordero

Title: Semiregular cuts

We will start on part 5 of Wong's notes.

April 12 - Antonio Nákid Cordero/Alice Vidrine

Title: Semiregular cuts/End and cofinal extensions

We will finish part 5 of Wong's notes and then start on part 6.

April 19 - Alice Vidrine

Title: End and cofinal extensions

We will finish part 6 of Wong's notes.

May 3 - No seminar today

Previous Years

The schedule of talks from past semesters can be found here.