# Hot Topic

## iTHEMS-CEMS Joint Colloquium was held on July 19

2018-07-23

iTHEMS-CEMS Joint Colloquium was held on July 19 at Okochi hall with a distinguished speaker, Prof. A. J. Leggett (Univ. Illinois at Urbana-Champaign).

The hall was packed with full of audience (more than 150 participants) to listen the talk by the world's leading theorist in quantum physics.

Prof. Leggett started his lecture with elementary considerations on classical radiation. Then he moves on to describe two photons emitted back-to-back in atomic transition and subsequent observation of the photon polarizations. In the "objective local theory" in which (i) local causality, (ii) induction and (iii) microscopic realism are assumed, one can prove an inequality for certain correlation measurement (Bell's theorem). Since quantum mechanics violates the inequality, the natural consequence is that (iii) is not satisfied in quantum mechanics. The key idea behind is the "entanglement" in which information is stored in non-local manner in quantum mechanics. Then, he talked about the notions of quantum teleportation, quantum cryptography and quantum computer where entanglement plays the essential role. The audience listened his lecture attentively and was fascinated by the interesting aspect of quantum mechanics and its applications.

Bell's Theorem, Entanglement, Quantum Teleportation and All That

July 19 at 16:00 - 17:30, 2018

# Upcoming Events

## Seminar

### Number Theory Seminar

July 24 at 10:00 - 12:35, 2018

Dr. Masataka Ono (Keio University)

Dr. Shingo Sugiyama (Nihon University)

Mr. Yoshinosuke Hirakawa (Keio University)

This seminar is aimed at scientists in general, not only to mathematicians.

10:00-10:45 "Multiple zeta functions associated with 2-colored rooted trees" Masataka Ono

10:55-11:40 "Modular forms and trace formulas with applications to equidistributions of their Fourier coefficients" Shingo Sugiyama

11:50-12:35 "On a generalization of Dobinski's formula" Yoshinosuke Hirakawa

Venue: Seminar Room #160, 1F Main Research Building, RIKEN

Event Official Language: English

## Symposium

### International Symposium on Quantum Fluids and Solids (QFS)

July 25 - 31, 2018

The International Symposium on Quantum Fluids and Solids (QFS) will be held at Ito International Research Center (IIRC) on Hongo campus of the University of Tokyo, Japan, from July 25 through 31, 2018. One of the sponsors of this conference is iTHEMS.

The QFS series started forty-three years ago making it one of the oldest series of international conferences in the field of low temperature physics. It has historically been focusing on physics of liquid and solid helium and hydrogen. But in this century its scope is expanding widely from laser cooled cold atoms to topological matters. At QFS2018 in Tokyo, this trend will be continued and with even more interdisciplinary aspects emphasized between the traditional subjects and those in broader physical systems.

Venue: Ito International Research Center (IIRC), Hongo Campus, The University of Tokyo

Event Official Language: English

# Paper of the Week

## Hilbert schemes of two points on K3 surfaces and certain rational cubic fourfolds

2018-07-23

The goal of birational geometry is the classification of algebraic varieties up to birational equivalence. An algebraic variety is called rational if it is birationally equivalent to the projective space. In this paper, Genki Ouchi studied the rationality problem of (complex) cubic fourfolds, that is four dimensional complex hypersurface defined by a polynomial of degree 3. Conjecturelly, very general cubic fourfolds are irrational. However, no cubic fourfold has been proven to be irrational so far. On the other hand, there are five known examples of rational cubic fourfolds. They expect that the mysterious relation between rational cubic fourfolds and K3 surfaces is a key to solve the rationality problem. There are two inconsistent conjectures about it. So they should modify one of them at least. Together with previous works, he proved that known rational cubic fourfolds satisfy both conjectures. To modify the conjectures, we have to find a new rational cubic fourfold.

Reference:

Genki Ouchi

"Hilbert schemes of two points on K3 surfaces and certain rational cubic
fourfolds"

arXiv: 1805.05176

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