vol. 81 | iTHES

Vol. 81, May 25th, 2015


  • Upcoming Events
  • Paper of the week

Paper of the week

Clive Emary, Neill Lambert, and Franco Nori


Leggett-Garg inequalities

From the Office

The office of iTHES assistant, Ms.Chikako Oota is situated at the second floor of the main research building, room # 246. The extension number is 3261. She will be at the office from 10 a.m. to 16 p.m.

Upcoming Events

Prof.Yasuhiro Masuda (Institute of Particle and Nuclear Studies, KEK)
EDM Measurement with Ultracold Neutrons
Fri 29th May 2015 11:00-12:00
Main research building, 5th floor, 535,537
CP violation is one of important issues in particle physics. The CP violation induces an electric dipole moment in the neutron (nEDM). With nEDM, many theories of particle physics have been tested. Although the standard model predicts very small values of nEDM, new physics such as supersymmetric theory as well as multi-Higgs model, which is beyond the standard model, predicts nEDM values in a 10^{-27} e cm region. The present state of the arts nEDM measurement is at Grenoble, which shows the upper limit of 3×10^{-26} e cm. In this measurement, ultracold neutrons (UCN) was used. UCN are very low energy neutrons, which can be confined in a measurement cell. The precision of the measurement was limited by the number of UCN in the cell, but the improvement of the number of UCN was strongly limited by Liouville’s theorem. Many institutes have been developing super thermal UCN sources, which get rid of this limitation. Here, we discuss our approach to this problem. Our UCN source became world competitive. We also discuss the present status and the future direction of our nEDM measurement.

Kazunori Kohri (KEK)
Close Encounters of the Dark Matter
12:30-13:30, May 29.
Room 535-537 in the Main Research Build.
I review the current status of the dark matter research for non-specialists.

June 4 (Thur.) from 2:00 pm
Dr. William Witczak-Krempa (https://www.perimeterinstitute.ca/people/william-witczak-krempa )
Constraining quantum critical dynamics: 2+1D Ising model & beyond
Rm 154&156, Main Research Building, Wako campus, RIKEN
Quantum critical (QC) phase transitions generally lead to the destruction of quasiparticles. The resulting correlated quantum fluid, when thermally excited, displays rich universal dynamics. We establish non-perturbative constraints on the linear-response dynamics of QC systems at finite temperature, in spatial dimensions above one. Specifically, we analyze the large frequency/momentum asymptotics of observables, which we use to derive powerful sum rules. The general results are applied to the O(N) Wilson-Fisher fixed point (CFT), describing the QC Ising and XY models when N=1,2, respectively. We'll contrast the results with Dirac fermions. Our focus will be on the order parameter susceptibility, conductivity, and shear viscosity. Connections to quantum Monte Carlo simulations, experiments and AdS/CFT will be made.
It's based on my recent paper (http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114.177201 ), and other works with Subir Sachdev.

Dr. Tomoyuki Higuchi
(The Institute of Statistical Mathematics)
"Interaction, Integration, and Design: Key elements for success on promoting the interdisciplinary research"
(in Japanese)
June 4 (Thur.) 2015, 10:30-11:30
Main research building 435-437

"Symposium on the Present and Future of iTHES" originally planned on June 15 (Mon), 2015
is postponed until Fall or Winter of this year from various constraints. We will announce the new date as soon as decided. Thanks for your understanding.
Tetsuo Hatsuda

Paper of the week

Leggett Garg inequalities
The question of whether a macroscopic system can display quantum properties has existed since the birth of quantum theory. Some predict that macroscopic quantum behavior is forbidden due to some as yet unknown modification of quantum theory, while others expect it is just a matter of time before a truly macroscopic object is shown to exhibit quantum effects. Leggett and Garg put this argument into a concrete mathematical form with their set of inequalities, which can be applied and tested in real systems. In this review paper we trace the recent progress of experimental implementation of these inequalities, as well as discuss issues such as how to realize them with weak measurements, and how to overcome the 'clumsiness loophole'.
Clive Emary, Neill Lambert, and Franco Nori, 2014 Rep. Prog. Phys. 77 016001 doi:10.1088/0034-4885/77/1/016001
* This work was done in collaboration with Clive Emary from the University of Hull, UK.

This figure illustrates how different versions of the Leggett-Garg inequality are violated as a function of time interval "tau" and system frequency "Omega". Any value greater than one is a violation, and can rule out 'macrorealist' theories.