＜＜＜「@」を「__AT__」に置き換えています＞＞＞

Date: Sat, 27 Jul 2024 00:19:39 +0900
To: sg-l__AT__yukawa.kyoto-u.ac.jp
Subject: [Sg-l:8620] One world IAMP mathematical physics seminar - Robert Wald
From: Takahisa IGATA (Sg-l 経由) 

素粒子論グループのみなさま、

依頼により、セミナー情報を転送します。
よろしくお願いします。

学習院大学
伊形尚久

============　

One world IAMP mathematical physics seminar

Tue July 30, UTC 14:00-15:00, JST 23:00-14:00
Robert Wald (Chicago)

The Memory Effect and Infrared Divergences

The "memory effect" is the permanent relative displacement of test 
particles after the passage of gravitational radiation. It is associated 
with both the propagation of massive bodies out to timelike infinity 
("ordinary memory") or the propagation of radiation out to null infinity 
("null memory"). The memory effect can be characterized by the failure 
of the shear tensor at order 1/r to return to zero at late times, even 
though it is "pure gauge." Closely analogous effects occur in 
electromagnetism, where the vector potential at order 1/r fails to 
return to zero even though it is "pure gauge." In both cases, the 
Fourier transform of the radiative field has divergent behavior at low 
frequencies. This gives rise to infrared divergences (i.e., infinite 
numbers of "soft" gravitons/photons) in the quantum field theory 
description if one attempts to describe these states as vectors in the 
usual Fock Hilbert space representation. To obtain a mathematically 
sensible quantum scattering theory, one must allow states with 
nonvanishing memory in the "in" and "out" Hilbert spaces. An elegant 
solution to this problem in massive quantum electrodynamics was given by 
Kulish and Fadeev, who constructed a Hilbert space of incoming/outgoing 
charged particle states that are "dressed" with radiative fields of 
corresponding memory, so as to yield vanishing large gauge charges at 
spatial infinity. However, we show that this type of construction fails 
in quantum gravity. The primary underlying reason is that the 
``dressing'' contributes to null memory, thereby invalidating the 
construction of eigenstates of large gauge charges. In quantum gravity, 
there does not appear to be any choice of (separable) Hilbert space of 
incoming/outgoing states that can accommodate all scattering 
states.etermining the set of all Wigner-positive states and of all 
Kirkwood-Dirac positive states.

The zoom link will appear here 15 min before the talk:
https://researchseminars.org/talk/IAMP_seminars/160/


-- 
Takahisa IGATA
Gakushuin University
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Date: Sat, 25 Jan 2025 01:03:15 +0900
To: sg-l__AT__yukawa.kyoto-u.ac.jp
Subject: [Sg-l:9064] One World IAMP Mathematical Physics Seminar - 白石直人 - Tue Jan 28
From: Takahisa IGATA (Sg-l 経由) 

素粒子論グループの皆様、

依頼により、セミナー情報を転送します。
よろしくお願いします。

学習院大学
伊形尚久

=====

学習院大学の田崎です。
1月28日の日本時間の夜 11 時から以下のように東大の白石直人さんのオンラインセミナーがあります。
白石さんが2019年の論文で開拓した量子スピン系が非可積分であることを厳密に示す一連の研究について話してもらいます。素粒子理論や場の量子論とは（今の段階では）直接の関係はありませんが、量子多体問題における重要な新しい研究の流れだと考えています（実は私も関連する研究を最近、少し始めました）。
ご興味のある方は（夜、遅いですが）ぜひご参加ください。また、興味を持ちそうな方がいればご遠慮なく情報を転送してください。

============
IAMP One World mathematical physics seminar

Tue Jan 28, UTC 14:00-15:00, JST 23:00-24:00
Naoto Shiraishi (Tokyo)

Proving non-integrability of quantum spin systems

In mathematical physics, integrable systems have been studied
intensively, and various quantum spin models have been revealed to be
integrable. In contrast, few studies in mathematical physics have
tackled quantum non-integrability. Here we characterize
non-integrability by the absence of local conserved quantity as a
working definition. The hardness of analyzing non-integrability comes
from the fact that there is no good method to treat all possible local
conserved quantities. For this reason, non-integrability is sometimes
even considered to be out of the scope of rigorous mathematical
physics.
Contrary to this pessimistic view, a method to prove quantum
non-integrability was recently discovered. In this seminar, I will
talk about the recent progress in proving non-integrability of quantum
spin systems. In the first part, I will provide the proof of
non-integrability of S=1/2 XYZ chain with z magnetic field, where the
basic proof ideas and techniques can be seen. In the second part, I
will prove the classification of integrability/non-integrability for
all S=1/2 spin chains with symmetric nearest-neighbor interaction.
This classification theorem confirms that there is no missing
integrable models in this class. My talk is based on a series of
papers including collaborated works with M. Yamaguchi and Y. Chiba.

The zoom link will appear here 15 min before the talk:
https://researchseminars.org/talk/IAMP_seminars/168/
=================


One World Mathematical Physics Seminar は
IAMP（国際数理物理学連合）が企画しているオンラインのセミナーシリーズです。私も世話人をつとめています。
http://www.iamp.org/page.php?page=page_seminar
これまでのセミナーは全て録画され以下で公開されています。
https://www.youtube.com/__AT__iamp_seminars
また、セミナーの案内を定期的に受け取るには、
IAMPseminars__AT__gmail.com
に件名を "subscribe” としてメールを出してください。
また数理物理に興味のある方は、ぜひ IAMP への加入をご検討ください（私も理事をつとめています）。
http://www.iamp.org/page.php?page=page_membership

-- 
Takahisa IGATA
Gakushuin University