What does logic have to do with AI/ML for computational science? (Part 2)

Speaker: 

Eric Mjolsness

Institution: 

UC Irvine

Time: 

Monday, April 26, 2021 - 4:00pm to 5:50pm

Location: 

Zoom

Progress in artificial intelligence (AI), including machine learning (ML),
is having a large effect on many scientific fields at the moment, with much more to come.
Most of this effect is from machine learning or "numerical AI", 
but I'll argue that the mathematical portions of "symbolic AI" 
- logic and computer algebra - have a strong and novel roles to play
that are synergistic to ML. First, applications to complex biological systems
can be formalized in part through the use of dynamical graph grammars.
Graph grammars comprise rewrite rules that locally alter the structure of
a labelled graph. The operator product of two labelled graph
rewrite rules involves finding the general substitution 
of the output of one into the input of the next - a form of variable binding 
similar to unification in logical inference algorithms. The resulting models
blend aspects of symbolic, logical representation and numerical simulation.
Second, I have proposed an architecture of scientific modeling languages
for complex systems that requires conditionally valid translations of
one high level formal language into another, e.g. to access different
back-end simulation and analyses systems. The obvious toolkit to reach for
is modern interactive theorem verification (ITV) systems e.g. those
based on dependent type theory (historical origins include Russell and Whitehead).
ML is of course being combined with ITV, bidirectionally.
Much work remains to be done, by logical people.

Part II: Current and planned work.
Operator algebra semantics (and the relevant Fock spaces)
for scientific modeling languages based on rewrite rules,
derivation of simulation algorithms,
semantics-approximating transformations using ML;
semantics-preserving transformations using ITV ?,
relation to graph grammar pushout semantics,
verbs vs. nouns vs. expressions and logic of "eclectic types",
compositional and specialization hierarchies,
"Tchicoma" conceptual architecture.

 

What does logic have to do with AI/ML for computational science?

Speaker: 

Eric Mjolsness

Institution: 

UC Irvine

Time: 

Monday, April 19, 2021 - 4:00pm to 5:50pm

Location: 

Zoom

Progress in artificial intelligence (AI), including machine learning (ML),
is having a large effect on many scientific fields at the moment, with much more to come.
Most of this effect is from machine learning or "numerical AI", 
but I'll argue that the mathematical portions of "symbolic AI" 
- logic and computer algebra - have a strong and novel roles to play
that are synergistic to ML. First, applications to complex biological systems
can be formalized in part through the use of dynamical graph grammars.
Graph grammars comprise rewrite rules that locally alter the structure of
a labelled graph. The operator product of two labelled graph
rewrite rules involves finding the general substitution 
of the output of one into the input of the next - a form of variable binding 
similar to unification in logical inference algorithms. The resulting models
blend aspects of symbolic, logical representation and numerical simulation.
Second, I have proposed an architecture of scientific modeling languages
for complex systems that requires conditionally valid translations of
one high level formal language into another, e.g. to access different
back-end simulation and analyses systems. The obvious toolkit to reach for
is modern interactive theorem verification (ITV) systems e.g. those
based on dependent type theory (historical origins include Russell and Whitehead).
ML is of course being combined with ITV, bidirectionally.
Much work remains to be done, by logical people.
 

This is part 1 of a 2 part talk. It will cover background on:
Sketch of background knowledge in typed formal languages, 
Curry-Howard-Lambek correspondence, 
current computerized theorem verification, ML/ITV connections;
scientific modeling languages based on rewrite rules
(including dynamical graph grammars),
with some biological examples.

Iteration, reflection, and singular cardinals

Speaker: 

Dima Sinapova

Institution: 

University of Illinois, Chicago

Time: 

Monday, March 29, 2021 - 4:00pm to 5:30pm

Location: 

Zoom

Two classical results of Magidor are: 

 

(1) from large cardinals it is consistent to have reflection at $\aleph_{\omega+1}$, and

(2) from large cardinals it is consistent to have the failure of SCH at $\aleph_\omega$.

 

These principles are at odds with each other. The former is a compactness type principle. (Compactness is the phenomenon where if a certain property holds for every smaller substructure of an object, then it holds for the entire object.) In contrast, failure of SCH is an instance of incompactness. The natural question is whether we can have both of these simultaneously. We show the answer is yes

 

We describe a Prikry style iteration, and use it to force stationary reflection in the presence of not SCH.  Then we obtain this situation at $\aleph_\omega$. This is joint work with Alejandro Poveda and Assaf Rinot.

Model theory of large fields

Speaker: 

Erik Walsberg

Institution: 

UC Irvine

Time: 

Monday, February 1, 2021 - 4:00am to 5:30am

Location: 

Ether

Model theory of fields is a very successful topic. I believe it is fair to say that most of this subject consists of detailed studies to particular fields (the reals, complex, p-adic, etc...). Largeness is a field-theoretic notion introduced by Pop in the nineties. This notion now plays a very important role in Galois theory and is increasingly being studied for other purposes. A number of people, including myself, have long believed that largeness should play an important role in the model theory of fields. This is mainly because all known model-theoretically tame fields are large, so one hopes that a general model-theoretic study of large fields might have a unifying effect on the model theory of fields. Over the past year we have begun to develop a model theory of large fields and in particular we have proven the stable fields conjecture for large fields. The key tool is a new topology on the K-points of a variety over a large field K.

This talk will involve a little algebraic geometry, but I will try to make it accessible to those with minimal background.

Ideals and determinacy (Cont.)

Speaker: 

Nam Trang

Institution: 

University of North Texas

Time: 

Monday, January 25, 2021 - 4:00pm to 5:30pm

Location: 

Zoom

We present some ideas involved in the proof of the equiconsistency
of AD_\reals + Theta is regular and the existence of a strong,
pseudo-homogeneous ideal on P_{\omega_1}(\reals). Some variations of this
hypothesis are also shown to be equiconsistent with AD_\reals + Theta is
regular. This work is related to and partially answers a long-standing
conjecture of Woodin regarding the equiconsistency of AD_\reals + Theta is
regular and CH + the nonstationary ideal on \omega_1 is \omega_1-dense. We
put this result in a broader context of the general program of understanding
connections between canonical models of large cardinals, models of
determinacy, and strong forcing axioms (e.g. PFA, MM). This is joint work with G. Sargsyan and T. Wilson.

Kurepa trees and almost disjoint families under determinacy

Speaker: 

Nam Trang

Institution: 

UN Texas

Time: 

Monday, March 9, 2020 - 4:00pm to 5:30pm

Location: 

RH 440R

We formulate the Kurepa hypothesis (KH) and its generalizations in determinacy and prove KH fails there. More generally, we show that if $\kappa < \Theta$ and $cof(\kappa) > \omega$, then the set of branches through a  $\kappa$-tree must be well-orderable and has cardinality less than or equal to \kappa. We also show there are no maximal almost disjoint families at $\omega_1$ and its appropriate generalizations at regular cardinals $\kappa < \Theta$. This is joint work with William Chan and Steve Jackson.

What you can define from a Cantor Set

Speaker: 

Erik Walsber

Institution: 

UCI

Time: 

Monday, March 2, 2020 - 4:00pm to 4:50pm

Location: 

RH 440R

This talk concerns a connection between fractals and an interesting tame structure. If K is a Cantor subset of the real line (compact nowhere dense perfect subset) then (R,<,+,K) defines an isomorphic copy of the monadic second order theory of the successor function. This result is sharp as the monadic second order theory of the successor defines an isomorphic copy of (R,<,+,C) where C is the classical middle-thirds Cantor set. One can also show that if X is essentially any fractal subset of Euclidean space then (R,<,+,X) defines a Cantor subset of the real line, but I probably won't have time to say much about this. Joint work with Philipp Hieronymi.

Connected Component in n-dependent groups

Speaker: 

Nadja Hempel

Institution: 

UCLA

Time: 

Monday, February 24, 2020 - 4:00pm to 5:30pm

Location: 

RH 440R

1-dependent theories better known as NIP theories are the first class of the hierarchy of n-dependent structures. The random n-hypergraph is the canonical object which is n-dependent but not (n-1)-dependent. Thus the hierarchy is strict. Recently, in a joint work with Chernikov, we proved the existence of strictly n-dependent groups for all natural numbers n and we started studying their properties. The connected component over A, inspired by the definition of the connected component of algebraic group, is the intersection of all A-type definable subgroups of bounded index. A crucial fact about (type)definable groups in 1-dependent theories is the absoluteness of their connected components: Namely given a definable group G and a small set of parameters A, we have that the connected component of G over A coincides with the one over the empty set. A
 
We will give examples of n-dependent groups and discuss a generalization of absoluteness of the connected component to n-dependent theories.

 

From Finite to Infinite Combinatorics (Continued)

Speaker: 

Asaf Ferber

Institution: 

UC Irvine

Time: 

Monday, February 10, 2020 - 4:00pm to 5:30pm
<p>In this talk we will sketch some combinatorial statements which are quite trivial in the finite case and discuss their infinite analogs, which are quite often way harder (or mabye even false...). After giving some interesting examples in various subareas, we will turn our focus into one specific open problem which is known as the ``unfriendly partition conjecture''. More specifically, given a graph $G=(V,E)$, a partition $V=V_0\cup V_1$ is said to be ``unfriendly'' if every vertex $v\in V_i$ has at least as many neighbors in $V_{i+1}$ rather in $V_i$ (the computation $i+1$ is done mod 2). The statement ``every finite graph has an unfriendly partition'' is trivial. We will see that for the infinite case, this statement can be wrong as was shown by Shelah and Milner, and basically the only unknown case is when $G$ is a graph of an infinite but countable size.</p>

<p>The talk is based on few papers by other researchers (among other: a paper by Soukup, the Shelah-Milner paper, a paper by Thomassen, and more).</p>

 

From finite to infinite combinatorics

Speaker: 

Asaf Ferber

Institution: 

UC Irvine

Time: 

Monday, February 3, 2020 - 4:00pm to 5:30pm

Location: 

RH 440R

In this talk we will sketch some combinatorial statements which are quite trivial in the finite case and discuss their infinite analogs, which are quite often way harder (or mabye even false...). After giving some interesting examples in various subareas, we will turn our focus into one specific open problem which is known as the ``unfriendly partition conjecture''. More specifically, given a graph $G=(V,E)$, a partition $V=V_0\cup V_1$ is said to be ``unfriendly'' if every vertex $v\in V_i$ has at least as many neighbors in $V_{i+1}$ rather in $V_i$ (the computation $i+1$ is done mod 2). The statement ``every finite graph has an unfriendly partition'' is trivial. We will see that for the infinite case, this statement can be wrong as was shown by Shelah and Milner, and basically the only unknown case is when $G$ is a graph of an infinite but countable size.

The talk is based on few papers by other researchers (among other: a paper by Soukup, the Shelah-Milner paper, a paper by Thomassen, and more).

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