Berry’s paradox

News
22 Apr, 2016. The slide file was uploaded

Title
Berry’s paradox

Type
Freshman seminar at math department of Meiji University

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Slide in Japanese

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Random numbers

News
22 Apr, 2016. The slide file was uploaded

Title
Random numbers

Type
A talk at a high school

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Slide (in Japanese)

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Can one compute a more random set uniformly?

News
24 Mar, 2016. The slide file was uploaded

Title
Can one compute a more random set uniformly?

Type
A talk at a meeting of Mathematical Society of Japan

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mathsoc

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An Introduction to statistics

News
24 Mar, 2016. The slide file was uploaded

Title
An Introduction to statistics

Type
A talk to junior-high students

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junior

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Randomness of randomness deficiency

News
26 Feb, 2016. The slide file was uploaded

Title
Randomness of randomness deficiency

Type
A talk in a seminar with Suzuki lab

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slide

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Randomness notions in Muchnik and Medvedev degrees

News
26 Feb, 2016. The slide file was uploaded

Title
Randomness notions in Muchnik and Medvedev degrees

Type
A talk in Dagstuhl seminar on “Computability Theory”

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slide

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Coherence of reducibilities with randomness notions

News
1 Feb 2016, accepted by TOCS

Title
Coherence of reducibilities with randomness notions

Type
Full paper

Journal
TOCS, post proceedings of CCR2016

Abstract
Loosely speaking, when $A$ is “more random” than $B$ and $B$ is “random”,
then $A$ should be random.
The theory of algorithmic randomness has some formulations of “random” sets
and “more random” sets.
In this paper, we study which pairs $(R,r)$ of randomness notions $R$
and reducibilities $r$ have the follwing property:
if $A$ is $r$-reducible to $B$ and $A$ is $R$-random,
then $B$ should be $R$-random.
The answer depends on the notions $R$ and $r$.
The implications hold for most pairs, but not for some.
We also give characterizations of $n$-randomness via complexity.

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preprint

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A way to judge using probability

News
13 Dec, 2016 the slide file was uploaded

Title
A way to judge using probability

Type
A lecture in a high school

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slide in Japanese

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Using Almost-Everywhere Theorems from Analysis to Study Randomness

News
10 Oct 2016, published online
29 Feb 2016, Accepted by BSL
May 2015, Resubmitted.
3 Nov 2014. Submitted

Title
Using Almost-Everywhere Theorems from Analysis to Study Randomness
(with Jing Zhang and Andre Nies)

Type
Full paper

Journal
The Bulletin of Symbolic Logic, Volume 22, Issue 3
September 2016, pp. 305-331
arXiv
The latest version is here.

Abstract
We study algorithmic randomness notions via effective versions of almost-everywhere theorems from analysis and ergodic theory. The effectivization is in terms of objects described by a computably enumerable set, such as lower semicomputable functions. The corresponding randomness notions are slightly stronger than Martin-Lo ̈f (ML) randomness. We establish several equivalences. Given a ML-random real z, the additional randomness strengths needed for the following are equivalent.
(1) all effectively closed classes containing z have density 1 at z.
(2) all nondecreasing functions with uniformly left-c.e. increments are differentiable at z.
(3) z is a Lebesgue point of each lower semicomputable integrable function.
We also consider convergence of left-c.e. martingales, and convergence in the sense of Birkhoff’s pointwise ergodic theorem. Lastly we study randomness notions for density of $\Pi^0_n$ and $\Sigma^1_1$ classes.

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Randomness notions in Muchnik and Medvedev degrees

News
20 Sep, 2016, the slide file was uploaded

Title
Randomness notions in Muchnik and Medvedev degrees

Type
Talk at a meeting of CTFM2016

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abstract
slide

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