セミナー・特別講義
2012年度
GCOE・基研セミナー
- title
- The equilibrium dynamics of the Dean-Kawasaki model for colloids: the standard MCT and beyond
- author
-
Bongsoo Kim
Changwon National University
- date
- 2013年 3月21日(水) 16:00〜
- place
- 基礎物理学研究所 研究棟・講義室K202
- abstract
-
This talk aims to communicate our recent results on the
dynamics of equilibrium density fluctuations of colloids. The
Dean-Kawasakiequation, a stochastic model equation for the density
fluctuations of colloidal dispersions, poses a theoretical challenge of
developing a systematic perturbation theory which preserves the
fluctuation-dissipation relation order by order, mainly due to its
multiplicative noise nature. A beautiful idea of time-reversal symmetry of
the corresponding action offers a solution to the challenge: a loop
expansion method applied to the new dynamic action incorporating a new set
of auxiliary variables is guaranteed to preserve the fluctuation-dissipation
relation (FDR) order by order. Our previous work along this line made an
error of overlooking a delta function in one of the FDRs between the
response and correlation functions. Restoring this missing contribution
cries out for the distinct scenario from that in previous work. Instead of
obtaining a single closed equation for the density-density correlation
function, we now face with the simultaneous equations of the three
independent correlation functions. The standard MCT equation is retrieved
from this coupled set of equations after a further approximation to get an
equation for the density-density correlation alone. The full one-loop theory
is analytically shown to remove the ergodic-nonergodic transition via
dynamic coupling to the auxiliary variable, making the dynamics always ergodic.
- contact
- 早川尚男(7024)
- note
-
このセミナーは京都大学基礎物理学研究所と京都大学理学研究科グローバルCOEプログラム「普遍性と創発性から紡ぐ次世代物理学」の共催で行われます。
*参照 基研HP:http://www.yukawa.kyoto-u.ac.jp/contents/seminar/detail.php?SNUM=51506
GCOE・基研セミナー
- title
- 量子古典対応の情報幾何学的解析
- author
-
松枝 宏明
仙台高等専門学校
- date
- 2013年 3月14日(木) 16:00〜
- place
- 基礎物理学研究所 研究棟・講義室K202
- abstract
-
量子多体系を古典系に変換する方法は,鈴木・トロッター変換等に代表されるように,量子系の数値解析手法において非常に重要である.
一方,超弦理論のAdS/CFT対応のように,基礎物理的に興味のある量子古典変換も発見されて久しい.
更には,エンタングルメントくりこみ仮説(MERA)と呼ばれる最先端の変分理論も,エンタングルメント・エントロピーのスケール性の議論から,量子古典変換の物理を内包していると考えられている.
AdS/CFTにおける古典サイドは,双曲(AdS)計量を持っており,それが元々の量子臨界系のスケール不変性を特徴づけている.
古典サイドの幾何学構造の物理的意味を調べることは,一連の物理のより深い理解につながると考えられる.
本研究では,古典サイドを具体的なモデルで表現するのではなく,抽象的な「情報」と捉え,情報がAdS空間に適切に格納できる場合に,その情報の物理的な意味は何か,
また元の量子系がどのような性質を持つべきかを情報幾何学的に考察する[1].
察する対象として,相対Tsallisエントロピーを距離として持つ情報空間を導入する(Tsallisの非加法性を与える因子qは全体の係数としてしか働かないので,基本的には相対vonNeumannエントロピーと同じ意味である).
このとき,最大限エンタングルした量子臨界系のデータは,AdS計量を持つ一次元高い古典情報空間に埋め込まれることが証明できる.
余剰の次元はエネルギー或いは長さスケールに相当する.
少なくとも空間一次元系では,中心電荷cが∞のときに量子系は最大限エンタングルするということが理論的に示せるが,この条件はAdS/CFTのlarge-N極限と同じものになっている.
また,元の量子系の密度行列の古典表示は,ホログラフィックな相関関数と見なせるが,それが指数関数的に減衰し,確かに量子臨界的な長距離相関が消えていることが分かる.
物理的には,元の量子系が臨界状態のときには全ての長さスケールの競合を含んでいるので,それをスケールごとに分解すれば量子相関の弱い系としてAdS空間に適切にデータを格納できるということだと考えられる.
関連する研究として文献[2]が挙げられる.ここでは自由ボソン場(c=1)に対する情報空間が議論されている.このときは,c→∞でなくとも情報空間はAdSになる.
Brown-Heneaux電荷の意味ではcはTsallisのqに含まれており,large-Nの仮定を緩めても相対エントロピーの構造は不変であることを示唆している.
[1] Hiroaki. Matsueda, arXiv:1208.5103.[2] Masahiro Nozaki, Shinsei Ryu, and Tadashi Takayanagi, arXiv:1208.3469
- contact
- note
-
このセミナーは京都大学基礎物理学研究所と京都大学理学研究科グローバルCOEプログラム「普遍性と創発性から紡ぐ次世代物理学」の共催で行われます。
*参照 基研HP:http://www.yukawa.kyoto-u.ac.jp/contents/seminar/detail.php?SNUM=51501
GCOE・基研セミナー
- title
- 重力波望遠鏡が拓く新しい天文学
- author
-
安東正樹
国立天文台
- date
- 2013年 3月8日(金) 16:00〜
- place
- 基礎物理学研究所 研究棟・講義室K202
- abstract
-
重力波の存在は、一般相対性理論によって理論的に存在が予言され、連星パルサーの軌道周期変化の観測から間接的に証明されている。
その一方、非常に微弱な信号であるため、直接検出は未だなされていない。
しかし、重力波を観測することができれば、連星合体や超新星爆発などの極限天体現象の中心部やブラックホールに関連する現象、晴れ上がり以前の初期宇宙など、これまでの電磁波による観測では得られない情報をもたらしてくれることが期待できる。
「かぐら」 (KAGRA)は日本が中心となって建設を進めている大型干渉計型重力波望遠鏡である。
KAGRAは、約200Mpc遠方の連星中性子星を観測できるだけの性能を持つ計画であり、実現されれば重力波の直接検出と、それによる新い天文学の創成を成し遂げることが期待できる。
本講演では、重力波天文学の可能性とその創成に向けたこれまでの取り組み、KAGRA計画の概要と建設の現状、さらに、将来の展望を紹介する。
- contact
- note
-
このセミナーは京都大学基礎物理学研究所と京都大学理学研究科グローバルCOEプログラム「普遍性と創発性から紡ぐ次世代物理学」の共催で行われます。
*参照 基研HP:http://www.yukawa.kyoto-u.ac.jp/contents/seminar/detail.php?SNUM=51494
GCOE・基研セミナー(物性)
- title
- 水面を浮遊する粉体の動的不均一性
- author
-
齊藤 国靖
University of Twente, the Netherlands
- date
- 2013年 2月25日(月) 16:00〜
- place
- 基礎物理学研究所 研究棟・講義室K202
- abstract
-
湖沼に発生したアオコや海を浮かぶ廃棄物など、水面を漂う浮遊物は時に厄介であり、その集団運動を理解することは環境を守るという観点からも重要である。
そこで、本実験では、浮遊物の集団的な振舞いを理解するため、水面に浮かぶ粉体の動的不均一性と被覆率との関係を調べた。
まず、水面に多数の粉体を浮かべ、水の入った容器を加振することで粉体を駆動する。
加振の強さは固定するため、粉体の被覆率が唯一のパラメータである。
この時、粉体同士は毛管力(capillary force)を介して複雑に相互作用し、水面に生じる対流によって運ばれる。
個々の粉体の変位の内訳は、対流による輸送分がほとんどだが、その輸送分を差し引いた「ゆらぎ」に注目すると、驚くほど空間的に不均一であることが解った。
そこで、浮遊する粉体の易動度及びその分散を調べることで動的不均一性の時間スケールを見積もり、4点相関関数から動的相関長を測定した結果、ジャミング転移点の近傍で冪的な発散を示すことが解った。
また、本実験で得られた動的臨界指数の値は、異なる駆動力を用いた先行研究の結果とほぼ一致している。
本実験の重要な結論は、流れがある中にも動的不均一性を見出した点と、動的臨界指数が駆動力に依らない普遍性を持つことを示唆した点である [1]。
[1] C. Sanli, K. Saitoh, S. Luding, and D. van der Meer,
“Denseheterogeneous flow of cohesive floaters on capillary ripples: A comparativestudy on morphological and conventional approaches to understand dynamicheterogeneities”, in preparation
- contact
- 基礎物理学研究所 教授 早川尚男(内線:7024)
- note
-
このセミナーは京都大学基礎物理学研究所と京都大学理学研究科グローバルCOEプログラム「普遍性と創発性から紡ぐ次世代物理学」の共催で行われます。
*参照 基研HP:http://www.yukawa.kyoto-u.ac.jp/contents/seminar/detail.php?SNUM=51485
GCOE・基研セミナー(素粒子)
- title
- Matrix models for irregular conformal blocks
- author
-
Chaiho Rim
Sogang University
- date
- 2013年 2月15日(金曜日) 16:00
- place
- 基礎物理学研究所 湯川記念館・会議室Y306
- abstract
-
Irregular conformal block is a new tool to study
Argyres-Douglas theory, whose irregular vector is represented as a
simultaneous eigenstate of a set of positive Virasoro generators. We
describe how to find the irregular conformal block using the partition
function of the beta-ensemble of hermitian matrix model.
- contact
- 基礎物理学研究所 細道和夫(内線7077)
- note
-
このセミナーは京都大学基礎物理学研究所と京都大学理学研究科グローバルCOEプログラム「普遍性と創発性から紡ぐ次世代物理学」の共催で行われます。
*参照 基研HP:http://www.yukawa.kyoto-u.ac.jp/contents/seminar/detail.php?SNUM=51483
GCOEセミナー
- title
- New features of broken time reversal symmetry in unconventional superconductors
- author
-
Professor Manfred Sigrist
(ETH Zurich)
- date
- 2013年 2月15日(金曜日) 10:00-11:30
- place
- 理5号館(物理学教室)第4講義室(5階525号室)
- abstract
-
Spontaneously broken time reversal symmetry (TRS) has been a fascinating feature
of unconventional superconductivity every its discovery. In this talk I will discuss
two phenomena in unconventional superconductors, one motived by recent experiments
on the 3-Kelvin phase of Sr2RuO4 and the other representing a prediction of a novel
state in non-centrosymmetric superconductors.
(1) The Josephson effect coupling Pb to Sr2RuO4 through Ru-metal inclusions shows a pronounced anomaly
in the Josephson critical current at the transition to bulk superconductivity in Sr2RuO4. We will
argue that this behavior may result from the TRS breaking chiral p-wave phase introducing topologically
frustrated Josephson junction with a new limiting effect on the Josephson current.
(2) It was shown a few years ago that non-centrosymmetric superconductors could produce a TRS breaking
phase locally at twin boundaries. However, this phase does not produce any magnetic features unlike other
TRS breaking superconducting phases. We will show that in combination with spin magnetism the twin boundary
state can undergo a secondary transition to a phase producing spin and orbital magnetism.
This phase may be considered as spontaneous spin Hall effect.
- contact
- Y. Maeno(3783)
- note
-
GCOE・基研セミナー(物性)
- title
- Nonequilibrium thermodynamics theory describing heat working at maxmum power
- author
-
泉田 勇輝
お茶の水女子大学 シミュレーション科学教育研究センター
- date
- 2013年 2月6日(水曜日) 16:00
- place
- 基礎物理学研究所 研究棟・講義室K202
- abstract
-
In recent years, there have been renewed interests in the
efficiency at the maximum power (EMP) of heat engines among theoretical
physicists since the so-called Curzon-Ahlborn (CA) efficiency [1] has been
generally proved to be the upper bound of EMP for the linear irreversible
systems in 2005 [2]. In this talk, I would like to introduce some recent
theoretical advances on this new and old problem, especially focusing on
our work. First I study a molecular kinetic model of a finite-time Carnot
cycle working in the linear irreversible regime in detail [3, 4]. I show
that the model satisfies a special condition to attain the bound (CA
efficiency) by analyzing its transport coefficients explicitly. Then I
propose a minimal model of general nonlinear irreversible heat engines
[5], extending the results of the linear irreversible systems [2]. I
derive an upper bound of EMP for these systems, which turns out be higher
than the CA efficiency. If time permitted, I would also like to discuss
physical significance of the size dependence of EMP by a molecular
dynamics computer simulation of a heat engine model [6].
[1] F. Curzon and B. Ahlborn, Am. J. Phys. 43, 22 (1975).
[2] C. Van den Broeck, Phys. Rev. Lett. 95, 190602 (2005).
[3] Y. Izumida and K. Okuda, EPL. 83, 60003 (2008).
[4] Y. Izumida and K. Okuda, Phys. Rev. E 80, 021121 (2009).
[5] Y. Izumida and K. Okuda, EPL. 97, 10004 (2012).
[6] Y. Izumida and N. Ito, submitted
- contact
- 基礎物理学研究所 教授 早川尚男(内線:7024)
- note
-
このセミナーは京都大学基礎物理学研究所と京都大学理学研究科グローバルCOEプログラム「普遍性と創発性から紡ぐ次世代物理学」の共催で行われます。
*参照 基研HP:http://www.yukawa.kyoto-u.ac.jp/contents/seminar/detail.php?SNUM=51478
GCOE・基研セミナー(物性)
- title
- Nonequilibrium Equation of States for a Confined Quantum Gas: Effects due to a Moving Piston
- author
-
中村 勝弘
(ウズベキスタン国立大学(タシケント))
- date
- 2013年 2月4日(月曜日) 16:00
- place
- 基礎物理学研究所 研究棟・講義室K202
- abstract
-
We study a nonequilibrium equation of states for an ideal
quantum gas confined in the cavity under a moving piston with a small but
finite velocity [1], [2]. Confining to the thermally-isolated process, the
quantum nonadiabatic (QNA) contribution to Poisson’s adiabatic equation
and to Bernoulli’s formula which bridges the pressure and internal energy
is elucidated. We carry out a statistical mean of the pressure operator in
both the low-temperature quantum-mechanical and high temperature
quasi-classical regimes. The QNA contributions are quadratic in the piston’s
velocity and therefore time-reversal symmetric, in marked contrast to the
conventional belief, and they are positive, which means that the moving
piston gives rise to the apparently repulsive interaction among
non-interacting Fermi particles, for both expansion and contraction of the
cavity. The QNA contributions are inversely proportional to the
longitudinal size of the cavity, and thereby play a nontrivial role in
nano-scale heat engines based on quantum dots. The investigation is done
for a unidirectionally-expanding 3-d rectangular parallelepiped cavity as
well as its 1-d version. Its relevance in a realistic nano-scale heat
engine is discussed.
[1] K. Nakamura, et al: Phys. Rev. E 83, 041133 (2011);
[2] K. Nakamura, et al: Phys. Rev. E 86, 061128 (2012).
- contact
- 基礎物理学研究所 教授 早川尚男(内線:7024)
- note
-
このセミナーは京都大学基礎物理学研究所と京都大学理学研究科グローバルCOEプログラム普遍性と創発性から紡ぐ次世代物理学」の共催で行われます。
基研HP:http://www.yukawa.kyoto-u.ac.jp/contents/seminar/detail.php?SNUM=51477
GCOE セミナー
- title
- High Field NMR in Cuprates and Quantum Spin Systems
- author
-
Prof. Claude Berthier
(LNCMI, CNRS (UPR 3228) UJF, UPS, INSA,
CNRS, BP 166, 38042 Grenoble Cedex, France)
- date
- 2012年 11月8日(木曜日) 16:00−17:00
- place
- 物理学教室 (理学部5号館) 401号室
- abstract
-
After a short presentation of the Grenoble High Field magnetic facility, I’ll first describe recent
experimental results on detwinned ultra-pure single crystals of underdoped YBaCuO6+x. In the ortho II
and the ortho VIII phases, it is shown that above threshold field and below some threshold temperature,
the magnetic field H induces a charge ordering which is compatible with stripe order of period 4a [1],
providing a natural explanation for a reconstruction of the Fermi surface and the quantum oscillations
observed in these sample. I’ll also discuss the particular case of YBaCuO6.45 on which neutron
experiments have shown an increase “magnetic ordering” with the magnetic field [2]. NMR experiments
show that this corresponds to a progressive freezing of AF fluctuations, with a huge increase of their
average amplitude of the with H. The underdoped part of the phase diagram of the cuprate is
re-discussed on this basis [3].
In the second part, I’ll illustrate the physics of weakly coupled dimers by NMR experiments in two quasi 2D systems,
SrCu2(BO3) [4] and BaCuSi2O6 [5] . The first one is a frustrated system which is the archetype of the physics of
magnetization plateaus. The second one undergoes a Bose Einstein Condensation triplet of excitations[6], but presents
very unconventional properties[7] , namely an apparent 2D BEC due to the frustration between adjacent planes and
different spin-gaps every second plane [5].
[1] T. Wu et al., Nature 477 191 (2011)
[2] D. Haug et al., Phys. Rev. Lett. 103 017001 (2009) ; New. J. Phys. 12 105006 (2010)
[3] T. Wu et al., submitted to PRL.
[4] K. Kodama et al., Science 202 (2000) ; M. Takigawa et al, arXiv : 1209.0069
[5] S. Kramer et al., Phys. Rev. B 76 100406 (2007) and unpublished
[6] M. Jaime et al., Phys. Rev. Lett. 93 087203 (2004)
[7] S.E. Sebastian et al., Nature 441 617 (2006)
- contact
- 石田 憲二(kishida@scphys.kyoto-u.ac.jp), 内線3752
- note
-
GCOE Lecture
- title
- Quantum Spin Systems under high magnetic field
- author
-
Prof. Claude Berthier
(LNCMI, CNRS (UPR 3228) UJF, UPS, INSA,
CNRS, BP 166, 38042 Grenoble Cedex, France)
- date
- I: 2012年 10月 26日(金曜日) 16:00−17:30
II: 2012年 11月 2日(金曜日) 10:00−12:30
- place
- I: 物理学教室 理学部5号館北館 363号室
II: 物理学教室 理学部5号館 525号室
- abstract
-
Lecture 1
・Introduction to general concepts
1. Quasi-1D systems:
Introduction to Jordan Wigner transformation, and Tomonaga-Luttinger Liquid
・The XXZ spin chain
・Alternated spin chains, J1-J2 Frustrated spin chains, spin-Peierls case.
・Spin-ladders
・Others
Lecture 2
2. Quasi-2D systems
・Bipartite systems
(square lattice, J1-J2 frustrated square lattice and geometrically)
・Frustrated systems (Triangular, Kagome lattice)
・Weakly coupled dimers
・Bose Einstein Condensation
・Magnetization plateaus
Purpose of The Lectures
Although a spin is by essence a quantum object, the denomination quantum spin system is usually
dedicated to low-dimensional systems including localized electronic spins of small values
(1/2, 1..), dominantly coupled by anti-ferromagnetic (AF) exchange interaction. These
conditions enhance thermal and quantum fluctuations, and can destabilize the “semi-classical”
long range order ground states, of Neel type.
The interest for quantum spin systems has appeared very early from the theoretical point of view with the
introduction of the Ising model, the Heisenberg model, the Jordan Wigner transformation, and the Bethe ansatz
for spin 1/2 chains, all of them between 1925 and 1931. The excitations of the Heisenberg spin 1/2 chains were
calculated in 1962, and notions like fractional excitations (the spinons), predictions in the framework of
the Luttinger-Tomonaga paradigm, the Haldane conjecture that spin chains of integer spin should have gaped
excitations have appeared well before any experimental support. For example, the first experimental evidence
of spinons came only in 1995.
The purpose of these two lectures is not to review that enormous field, but simply to present an experimentalist
point of view the general concepts used in the study of quantum spin systems, the development of this area
in the last few decade, as well as unanswered questions. I’ll focus on the important role the magnetic field
in the physics of quantum systems which has the capability to induce quantum critical points and new exotic
ground states, like for example Bose-Einstein condensate or Wigner crystals of triplet excitations.
This will be illustrated by examples based on experiments using NMR technique, which is presently (with EPR)
the only technique allowing microscopic investigation above 17 T.
- contact
- Kenji Ishida (kishida@scphys.kyoto-u.ac.jp), 内線3752
- note
-
GCOE seminar
- title
- Stochastic differential equations and a review of their applications
- author
-
Professor Petr Lansky
(Academy of Sciences of the Czech Republic)
- date
- 2012年 11月 1日(木曜日) 13:30−14:30
- place
- 物理学教室 413号室
- abstract
-
Differential equations played a unique role in physics over centuries and
later on this also held for other branches of research as engineering, biology,
chemistry and recently economics. In the first part of this lecture, the concept
of stochastic differential equations will be introduced and illustrated on the
simplest stochastic functions, namely Poisson and Wiener stochastic processes.
In the next part, several applications to the real world problems will be
mentioned, including population modeling and mathematical finance applications.
Further, questions about the identification of the parameters of the stochastic
differential equations will be shortly reviewed. Finally, a summary of our own
results, including numerical techniques and search for the first passage time
as a functional of random functions will be given. These results will be presented
together with their implications for neuronal coding.
- contact
- 篠本 滋, shinomoto@scphys.kyoto-u.ac.jp
- note
-
GCOEセミナー
- title
- Fate of long wavelength fluctuations and initial states of inflationary universe
- author
-
Dr. Yuko Urakawa
(University of Barcelona)
- date
- 2012年 10月26日(金曜日) 17:30−18:30
- place
- 基礎物理学研究所研究棟K206
- abstract
-
The infrared(IR) behavior of fluctuations in (a quasi) de Sitter spacetime has been an
issue of debate for more than decade. A key to the IR issue is to remove influences
from an unobservable region in the universe, which can be interpreted also as gauge
artifacts in the local observable universe. In this talk, we will adress the regularity
of IR contributions in a general single field mode of inflation without employing the
slow-roll approximation. We will show that the IR regularity of primordial perturbations
strictly constrains the allowed quantum state. We will also reveal the connection
between the IR regularity and the gauge invariance in the local universe.
- contact
- Takahiro Tanaka, tanaka@yukawa.kyoto-u.ac.jp・宇治 7018)
- note
-
GCOEセミナー
- title
- Trapped Anti-hydrogen : A new frontier in fundamental physics・
トラップされた反水素:基礎物理の新たな最先端
- author
-
Prof. Dr. Niels Madsen氏
(Swansea University, Department of Physics)
(京都大学招へい外国人学者 受入先:化学研究所)
- date
- 2012年10月4日(木曜日) 15:00−16:30
- place
- 物理学教室 北館 第2講義室
- abstract
-
Detailed comparisons of anti-hydrogen with hydrogen promise to be a fruitful test bed
of fundamental symmetries such as the CPT Theorem for quantum field theory or studies
of gravitational influence on antimatter. With a string of recent successes, starting
with the first trapped anti-hydrogen and recently resulting in the first measurement
of a quantum transition in anti-hydrogen, the ALPHA collaboration is well on its way
to perform such precision comparisons. The presentation will discuss the key innovative
steps that has made these feats possible and in particular focus on the detailed work
on positron and antiproton preparation to achieve anti-hydrogen cold enough to trap as
well as the unique features of the ALPHA apparatus that has allowed the first quantum
transitions in anti-hydrogen to be measured with only a single trapped anti-hydrogen
atom per experiment. We will also look at how ALPHA plans to step from here towards
more precise comparisons of matter and antimatter and what we could possibly learn from such comparisons.
- contact
- 野田 章(Akira Noda、noda@kyticr.kuicr.kyoto-u.ac.jp・宇治(17)内線3281)
- note
-
GCOEセミナー
- title
- Dissipation through dispersion
- author
-
Professor Avraham Soffer
(Rutgers University)
- date
- 2012年6月27日(木曜日) 16:30−
- place
- 物理学教室 5号館北棟第一講義室(265号室)
- abstract
-
We consider systems coupled to a dispersive medium, in particular,
Hamiltonian systems, both linear and nonlinear. The prime examples
are the Nonlinear Klein-Gordon equation, the NLS with multibound state
linear part, and the resonance problem in Quantum Mechanics. We show
how the coupled modulation equations to the internal degrees of freedom
of the localized system, leads to dissipation, through the dispersion
of waves to infinity, and to, in general, non linear Master quations.
In particular, this approach was used to derive rigorously the phenomena
of “Selection of the Ground State” for NLS, which was later observed
experimentally.
- contact
- 太田隆夫(Takao Ohta, ext 3740)
- note
-
GCOEセミナー
- title
- Asymptotic Stability of Solutions-Modulation Equations
- author
-
Professor Avraham Soffer
(Rutgers University)
- date
- 2012年6月20日(木曜日) 16:30−
- place
- 物理学教室 5号館北棟第一講義室(265号室)
- abstract
-
I will describe a general theory to study the dynamics of soliton type solutions
of Dispersive equations, under small perturbations. The solution equations are
nonintegrebale in general, and the dynamics for large times of such systems is
very rich and complicated. The approach I will use allows the control of the
dynamics for all times, the scattering theory included, for small perturbations
of such solitons.
- contact
- 太田隆夫(Takao Ohta, ext 3740)
- note
-
GCOE・基研セミナー
- title
- Particle Acceleration in Relativistic Shocks
- author
-
Dr. Donald Ellison
(North Carolina State University)
- date
- 2012年4月26日(木曜日) 15:00−
- place
- 京都大学基礎物理学研究所 研究棟・会議室K206
- abstract
-
The first-order Fermi mechanism for particle acceleration in collisionless
shocks has been studied extensively for over 30 years. Nevertheless,
important problems remain, particularly when the shock speed approaches the
speed of light. Nonrelativistic shock acceleration has been applied in many
astrophysical environments, and relativistic shocks may be important for
pulsar winds and for gamma-ray bursts, two of the most exotic of all
phenomena. I will discuss the Fermi mechanism in general, and show new Monte
Carlo results for relativistic shocks both in the test-particle limit and
when accelerated particles make up a sizable fraction of the total energy. I
will emphasize trans-relativistic shocks, a regime that is particularly
difficult to address analytically but one that may be important for
gamma-ray burst afterglows.
- contact
- note
-
このセミナーは京都大学基礎物理学研究所と京都大学理学研究科グローバルCOEプログラム「普遍性と創発性から紡ぐ次世代物理学」の共催で行われます。
GCOEセミナー
- title
- The Surprising Story of Collisionless Shocks in Astrophysics
- author
-
Dr. Donald Ellison
(North Carolina State University)
- date
- 2012年4月12日(木曜日) 11:00−
- place
- 京都大学基礎物理学研究所 研究棟・会議室K206
- abstract
- For more than 30 years, first-order Fermi particle acceleration in collisionless shocks
(i.e., diffusive shock acceleration, DSA) has remained the mechanism of choice for
producing cosmic rays and other superthermal particle populations in various astrophysical
environments. The nonlinear nature of the mechanism, a result of the
intrinsic high acceleration efficiency, has presented challenges and surprises for modelers
over the years. I will briefly describe some of the surprising aspects of DSA
and, in particular, focus on magnetic field amplification and particle escape; two
phenomena that highlight the difficult plasma physics involved and which are undergoing
active current research. While collisionless shocks, with associated particle
acceleration, are believed to exist on scales from the Earth bow shock to galaxy
clusters, supernova remnants (SNRs) offer our best chance to study the mechanism.
This is the case because SNRs occur in varying environments including dense molecular
clouds and several SNRs show extremely broadband continuum emission from
radio to TeV gamma rays, sometimes accompanied with thermal X-ray emission.
Other aspects, such as the morphology of some young remnants, offer unique clues
to fundamental properties of the underlying plasma physics of both the remnant
and the coupled acceleration mechanism.
- contact
- 長瀧 重博
( nagataki@yukawa.kyoto-u.ac.jp)
- note
-
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