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第7回ＣＯＥ(自己組織系物理)ワークショップ ［通算第13回］
| COE若手研究者（PD）発表会 |
| 日 時 |
2005年2月26日(土) 10:30-17:00 |
| 場 所 |
〒169-0072 東京都新宿区大久保3-4-1 [地図] |
| 会 場 |
早稲田大学理工学部55号館S棟2階第3会議室 |
| 発表者 |
鳥居 隆（COE研究員）、吉田 至順（COE研究員）、湯浅 一哉(COE研究員）
松本 崇（COE研究員）、大瀧 昌子COE研究員）、鄭 美紅（COE研究員）
佐藤 高彰COE研究員）、春山 慎（COE研究員）、加藤徳剛（COE研究員）
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| [プログラム] |
| 10：30-11：00 |
鳥居 隆
「High Energy Corrections to Brane Cosmology」
Our universe is composed of a container and matters. The container is space-time which has 1-dimensionl (1-d) time and 3-d space. In general relativity, space-time can be variable and has dynamical degrees of freedom. Its dynamics is determined by solving the Einstein equations and equation of motions of the matters simultaneously. In words of Wheeler, matters tell space-time how to curve, and space-time tells matters how to move. >> abstract [word]
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| 11：00-11：30 |
吉田 至順
「Relativistic r-modes of rapidly rotating barotropic stars」
We develop a numerical scheme for obtaining the r-mode
oscillations of rapidly rotating relativistic stars. In the
present scheme, we neglect all metric perturbations and only
take account of the dynamics of the fluid in the background
spacetime of the unperturbed star (the relativistic Cowling
approximation). We also assume the star is barotropic, i.e.
neutrally stable against convection under the assumption of
adiabatic oscillations. Our numerical scheme is based on the
Yoshida-Eriguchi formulation for the analysis of the general
relativistic f-mode oscillations in the Cowling approximation
and a general relativistic generalization of
the Karino-Yoshida-Yoshida-Eriguchi's numerical scheme for
obtaining oscillations of rapidly rotating Newtonian stars.
By this new numerical scheme, frequencies of the r-mode
oscillations are obtained as functions of the ratio of the
rotational energy to the absolute value of the gravitational
energy T/|W| along sequences of polytropic equilibrium stars
whose ratio of the pressure to the total energy density at the
center of the star and the polytropic index are kept constant.
It is found that the dimensionless oscillation frequency
$\sigma/\Omega$ is a linearly decreasing function of T/|W|,
where $\sigma$ and $\Omega$ are the oscillation frequency and
the angular velocity of the star measured in an inertial frame
at spatial infinity. We also find that oscillation frequencies
of the r-modes are highly dependent on the relativistic factor
M/R of the star as already found in previous studies in which
the slow rotation approximation has been used. Here M and R
denote the mass and radius of the star, respectively.
|
| 11：30-12：00 |
湯浅 一哉
「Distillation of Quantum States through Zeno-like Measurements」
It has been realized that quantum features such as the superposition
principle and the nonlocality in quantum mechanics afford us with new
ideas to go beyond classical ones, and the so-called quantum information
is now one of the hottest topics in quantum physics. Recent astonishing
advances in nanotechnology are driving experimental physicists to
various attempts to run the ideas into reality, but still more ideas are
needed. For example, such an elementary and fundamental problem as how
to prepare a desired quantum state is one of the significant issues to
be tackled, since typical quantum states necessary for quantum
information, like entangled states with high quantum coherence, are
fragile against environmental perturbation and are not naturally found
in laboratory. >> abstract [pdf]
|
| − Lunch − |
| 13：30-14：00 |
松本 崇
「Characteristic Response of Brownian Motors Driven by Non-Stationary Effect」
Brownian motor is the theoretical model that describes the motion of Brownian particles in asymmetric periodic potential. The main consequence is that
unidirectional movement is induced in spite of unbiased driving force or
potential modulation which is either periodic in time or stochastic process. This phenomenon is called“ratchet effect”.
In the last decade, Brownian motors have drawn much attention as the model
of molecular motors. Recent experimental studies by means of one-molecular
measurement technique suggest qualitative agreement with the perspectives
according to Brownian motors, although the efficiency of Brownian motors is
much smaller than those of actual molecular motors.
In this presentation, we discuss the extension of the so-called “on-off
ratchet
”. On-off ratchet is one of archetypes of Brownian motors, in which
periodic potential takes two states alternatively. In
“on” state, potential has non-zero height, whereas potential is flat in
“off” state. Switches from one state to the other take place
stochastically. Mean velocity of the Brownian particle depends on the time
scale of switching, and it is maximized at a certain switching probability.
We consider the case that the switching processes are non-stationary. In
this case, residence time in each state (
“on” or “off”) has broad (power law) distribution. We find that mean
velocity of the particle becomes independent of mean residence time (time
scale of switching) at the stationary/non-stationary transition point. As a
result, on-off ratchet driven by non-stationary processes (NS ratchet)
shows larger velocity than that of conventional on-off ratchet (S ratchets)
at the fast switching regime, although maximum velocity is smaller than
that of S ratchet. NS ratchet also shows larger velocity at the low
temperature regime than that of S ratchet. We discuss that these behaviors
can be explained from the residence time distribution.
In the end of the presentation, we shortly discuss the implication of the
behaviors of NS ratchet in the study of molecular motors, and possible
direction to improve the efficiency of Brownian motors, especially based on
the residence time statistics.
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| 14：00-14：30 |
大瀧 昌子
「A mathematical model of spontaneous oscillatory contraction of muscle」
In general the muscle is in one of the two state possible states, relaxation or contraction. These contractions result from relative sliding of myosin and actin in the sarcomere,(Fig.1) which is the contraction structure unit of skeletal muscle. The switching between two states is depending on the Ca2+ concentrations. However another state has been detected between these two states. In the third state, that is SPontaneous Oscillatory Contraction (SPOC), sarcomere repeats contraction and extension spontaneously. A peculiarly interesting point is that SPOC is observed even if there is absence of the Ca2+. SPOC, the oscillating cycle of sarcomere length shows the saw tooth waveform that slow shortening and quick lengthening repeatedly occur every sarcomere through the transition between the two states (Fig.2). This wave is often spread over a long distance along muscle fiber. Muscle fibers is composed of hundreds of sarcomeres in series and one sarcomea also is composed of hundreds of myosin. In microscopic, the force generated by actin and myosin interaction occurs stochastically. SPOC is macroscopically observable, but how does this occur? >> abstract [word]
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| 14：30-15：00 |
鄭 美紅
「Self-Organized Collective Behaviors of Fish and an Attempt to Understand the Alternation Mechanism of Multi Interpretations of Ambiguous Figures」
The fish schooling is a typical animal social behavior. A fish school shows its high order collective behavior either when it is swimming in no risk circumstance or when it has been attacked by predators. To generate this high order collective behavior, every fish in the school contributes equally, there is no a leader in a fish school. Each fish in the school acts only based on the local information acquiring by its eye and its lateral line, it does not know the global situation. A main function of a fish school is to protect members through reducing predator’s successful kill when attacked by predators. Considering mentioned features of a fish school, we present an integration action model to investigate how fish generate schooling behavior and how fish schooling behavior protects members when a fish school attacked by predators. In this model the action of a fish consisting of three components of allemomimesis, avoidance and evading. Each fish determines its moving directions taking into account simultaneously three kinds of elemental actions mimicking its neighbors, avoiding collisions with its nearest neighbors, and evading from an approaching predator. The weights of three elemental actions are changed depending on situation. The results show the present model can adequately represent fish schooling either when it is swimming in no risk circumstance or when it has been attacked by predators. The results also manifest the highest order fish schooling behavior the largest ability protecting members of a fish school. >> abstract [word]
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| −休憩 − |
| 15：30-16:00 |
佐藤 高彰
「Dynamics and static structure of highly-functionalized nano-structured liquids」
I am currently working on dynamics and static structures in pure H-bond liquids, aqueous solutions of alcohol, amino acids, functionalized proteins, and nano-structured self-assembly systems including aqueous micellar solutions and liquid crystalline phases, employing spectroscopic and scattering techniques. |
| 16:00-16:30 |
晴山 慎
「Study of the galactic cosmic rays by heavy and ultra heavy nuclei」
The observed results in the galactic cosmic ray (GCR) source
composition are shown in Fig.1, in which these nuclei enhanced
in the source composition are identified as ultra-heavy (UH)
ones. This enhancement relates to the origin and the acceleration
mechanism of GCRs. As clearly seen in Fig.1, the condensation
temperature of refractory elements is usually higher than about
1000 K. These nuclei synthesized in massive stars and
supernovae (SNe) was ejected by stellar wind and SN explosion
(SNE) and cooled into the state of such a low temperature as
1000 K or so. Then, these were effectively condensed into the
matter identified as dust grains. In fact, the observations
identified that refractory elements deplete in galactic cool gas
and dust grains have been made after SNE within several months.
It seems to suggest the 」possibility of GCRs acceleration from
dust grains. However, UH nuclei must have been synthesized in
the s-process initiated with AGB stars and the r-process initiated
with the SNE. Therefore, if we discuss this serious problem in
more deeply, we must observe the UH isotopes of GCRs
precisely. >> abstract [pdf]
|
| 16:30-17:00 |
加藤徳剛
「Thermochromic Phase Transition on 2 dimensional organic dye crystallites」
When organic dye molecules form crystals or aggregates, visible absorption bands generally split or shift
from those of isolated (monomeric) dye molecules. Such spectral changes are described under the concept of
molecular excitons in the crystals or the aggregates, i.e., optical transition moment and electric dipole
moment interactions among the molecules induce shifts and splits of the bands, and the interactions depend
on the molecular arrangement in the crystal or the aggregate. [1] When the absorption band shifts to a lower
energy, such an aggregate and the shifted band are called J-aggregate and J-band, respectively. [2]
J-aggregates have been utilized as spectral sensitizers for silver halides in conventional photography, and
they are attracting much attention as candidates for nonlinear optical materials for ultra-fast optical devices
and sensitizers for solar cells. >> abstract [pdf]
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