JavaScript が無効化されています。ページを正しく表示するには有効化してくだださい。

OUTAP Colloquium 2014

ホーム > コロキウム & セミナー > 宇宙進化コロキウムのご案内 > 2014年度の宇宙進化コロキウム
・・・・・2014年度の宇宙進化コロキウム・・・・・

----------------------------------------------------------------------

講演者 :Luigi Troiano 氏 (サンニオ大学)、Maria-Carmela Vitelli 氏 (サンニオ大学)/SPEAKER :Prof. Luigi Troiano (University of Sannio), Dr. Maria-Carmela Vitelli (University of Sannio)
TITLE :Enabling Big Data Architectures for KAGRA
DATE :2/17(tue)14:00~
LOCATION:F608

ABSTRACT:
We discuss recent advances in software and hardware technologies which may help advanced gravitational wave observatories, including KAGRA, to face their challenges in data management and analysis. In particular after reviewing the HADOOP ecosystem and FPGA co-processing, we suggest a possible roadmap for seamless upgrade of existing computing infrastructures to the key foreseen innovations in data handling.

----------------------------------------------------------------------

講演者 :Innocenzo M. Pinto 氏 (サンニオ大学) /SPEAKER : Prof. Innocenzo M. Pinto (University of Sannio)
TITLE :Glitchology: an Elementary Perspective
DATE :2/17(tue)16:00~
LOCATION:F608

ABSTRACT:
Idiosyncratic transient disturbances (glitches) of environmental/ instrumental origin could be amenable to a relatively simple and physically motivated description, suggesting that they may indeed results from random superpositions of a limited number of "canonical" waveforms. Recent work aimed at identifying such elementary glitch constituents starting from real noisy data is summarized including a comparison among different tools, and a possible roadmap is outlined.

----------------------------------------------------------------------

講演者 :木内 建太 氏 (京都大学) /SPEAKER : Prof. Kiuchi (Kyoto University)
TITLE :Recent progress of binary neutron star merger simulations in numerical-relativitiy
DATE :2/18(wed)15:00~
LOCATION:F313

ABSTRACT:
We performed numerical relativity-magneto hydrodynamical simulations of binary neutron star merger on the Japanese supercomputer K. The grid resolution of 70 m is highest among the binary neutron star merger simulations done so far and we did an in-depth resolution study to figure out the amplification mechanism of magnetic fields during the binary neutron star merger. We found the Kelvin-Helmholts instability developed in the shear layer at the merger significantly amplifies the magnetic field. A hyper-massive neutron star formed after the merger is subject to the non-axisymmetric magneto-rotational instability. These two amplification mechanisms do not work with an insufficient resolution. The star collapses to a black hole and a formed accretion disk is strongly magnetized a priori. We found a coherent toroidal magnetic field inside the disk and not a coherent poloidal field above the black hole even after 60 ms after the black hole formation.

----------------------------------------------------------------------

講演者 :井上 芳幸 氏 (宇宙航空研究開発機構) /SPEAKER : Dr. Inoue (JAXA)
TITLE :Unveiling the nature of AGN coronae through future sub-mm and X-ray observations
DATE :1/7(wed)15:00~
LOCATION:F313

ABSTRACT:
While the cosmic X-ray background is likely to originate from individual AGNs, the origin of the cosmic MeV gamma-ray background is not fully understood. We proposed that AGNs having non-thermal electrons in a corona may explain the MeV gamma-ray background. Such non-thermal electrons are expected to exist if a corona is heated by magnetic reconnections. However, the sensitivity of current MeV gamma-ray instrument is not sufficiently good to detect the expected power-law tail in the MeV band from individual AGNs. Furthermore, the heating mechanism of a corona in AGNs is still unknown in the first place, although magnetic reconnection heating is one possibility. In this talk, I would like to introduce how we can probe the origin of the cosmic MeV gamma-ray background and the nature of AGN coronae such as magnetic field and non-thermal content through future observations by ALMA and Astro-H. ----------------------------------------------------------------------

講演者 :高部 英明 氏 (大阪大学) /SPEAKER : Prof. Takabe (Osaka Univ)
TITLE :Laser Astrophysics on High-Mach Collisionless Shocks via Self-Organization Physics in Universe
DATE :12/16(tue)15:00~
LOCATION:F313

ABSTRACT:
It is said that the cosmic rays are produced by a variety of shock waves accompanying magnetic turbulence. The acceleration mechanism is believed to be the diffusive shock accelerations[1]. Most of astrophysicists believe that the background magnetic fields help the formation of shocks. We have proposed the self-organizing shock formation scenario via Weibel instability and its nonlinear evolution[2,3]. We found that the model experiment to proof this physics can be done with the biggest laser, NIF at LLNL(USA)[4]. In the presentation, we start with physical mechanism of the shock formation demonstaretd with multi-dimensional PIC simulation, and I explain the physics of the collisonless shock. Then, I would like to introduce the experimental activities done by Prof. Y. Sakawa and his international team, ACSEL[5]. I will come to what we plane as the next step. In addition, I also would like to introduce a new laboratory astrophysics subject producing electro-positron fireball in laboratory[6].
[1] Blandford, R. D., & Ostriker, J. P. 1978, ApJL, 221, L29
[2] H. Takabe et al., Plasma Physics and Controlled Fusion 50, 124057 (2008)
[3] T-N Kato and H. Takabe, Physics of Plasmas 17, 032114 (2010)
[4] https://lasers.llnl.gov/
[5] Hye-Sook Park et al., High Energy Density Physics 8 (2012) 38-45
[6] H. Takabe, T. Moritaka et al, in preparation.

----------------------------------------------------------------------

講演者 :高見 健太郎 氏 (フランクフルト大学) /SPEAKER : Dr. Takami (Goethe University Frankfurt am Main)
TITLE :Binary Neutron Stars in both Fundamental Physics and Astrophysics
DATE :10/21(tue)15:00~
LOCATION:F313

ABSTRACT:
There is no doubt that a binary neutron star is one of the most attractive objects in physics. In fact, behind its complicated nature lie many interesting questions. These can be studied by the two different standpoints of fundamental physics and astrophysics. Under the point of view of fundamental physics, we have studied a head-on collision of two neutron stars boosted at ultrarelativistic speeds. Then we have found non-trivial properties of the criterion for black-hole formations and the critical behavior of the collisions. Moreover our results have showed that proton-proton collisions in LHC and UHECR are unlikely to produce black holes within classical general relativity. On the other hand, under the astrophysical point of view, we have studied the merger of binary neutron stars in circular orbit and the subsequent formation of a hypermassive neutron star. We have found two clear and distinct peaks in the power spectral density of the emitted gravitational waves. Surprisingly, we found that the correlation between the low-frequency peak and the compactness of the stars is essentially universal independently of the equation of state. Furthermore by using this knowledge we have showed that we can significantly constrain the equation of state of compact stars through gravitational observations made by advanced detectors such as LIGO or KAGRA. In this talk, I will present the details of these results.

----------------------------------------------------------------------

講演者 :平下 博之 氏 (中央研究院天文及天文物理研究所) /SPEAKER : Prof. Hirashita (ASIAA)
TITLE :Dust Processing in the Interstellar Medium and Dust Enrichment in Galaxies
DATE :10/1(wed)15:00~
LOCATION:F313

ABSTRACT:
For the evolution of dust in the interstellar medium (ISM), there are two aspects to be considered: the dust amount and the dust properties. Among the dust properties, the grain size distribution is of particular importance, since it reflects dust processing in the ISM. Moreover, to interpret observed extinction curves, the understanding of grain size distributions is crucial. In this talk, we emphasize the importance of various dust processing mechanisms, such as grain growth by accretion and coagulation, grain disruption by shattering, and grain destruction in supernova shocks, in understanding the dust evolution in galaxies. Since dust grains supplied from stellar ejecta has predominantly large sizes, the extinction curve is predicted to be flat if only the stellar sources of dust is taken into account. The extinction curve becomes steep only if we consider interstellar processing, especially, shattering. After a large abundance of small grains are produced by shattering, grain growth by accretion further steepens the extinction curve. Small grain production by shattering significantly activates grain growth by accretion, naturally explaining the high dust abundance in high-redshift quasars. Importance of coagulation is indicated by recent observations of μm-sized grains in molecular cloud cores. Efficient coagulation is also necessary to reproduce the Milky Way extinction curve.

----------------------------------------------------------------------

講演者 :大須賀 健 氏 (国立天文台) /SPEAKER : Prof. Ohsuga (NAOJ)
TITLE :Radiation Magnetohydrodynamics Simulations of Black Hole Accretion Flows and Outflows
DATE :9/17(wed)15:00~
LOCATION:F313

ABSTRACT:
By performing radiation magnetohydrodynamics simulations, we investigate accretion disks, jets, disk winds around the black holes. We will mainly talk about the radiatively-driven outflows. In the case of the super-Eddington mode, the jets and disk winds are launched via the radiation force. The velocity of the jets does not exceed 0.5c, since the radiation flux force balances with the radiation drag force. The disk winds fragments into gas clouds via the radiation R-T instability. The powerful disk winds are also launched from the sub-Eddington disks through the line-force. Such winds might resolve some observed features of ULXs and AGNs. Finally, we will comment about a new method of radiation magnetohydrodynamics.

----------------------------------------------------------------------

講演者 :Enrico Barausse 氏(パリ国立天文台)/SPEAKER : Prof. Enrico Baraussee (Institut d'Astrophysique de Paris)
TITLE : Compact objects as probes of astrophysics, gravity and fundamental physics
DATE : 6/5 (Thr) 14:30 ~
LOCATION: F608

ABSTRACT:
Observations of compact objects such as neutron stars and black holes, in isolation or in binary systems, are not only interesting in themselves, but also constitute an ideal testing ground for galaxy formation models, cosmology, as well as gravitation and fundamental physics. I will discuss examples of these tests that can be performed with existing electromagnetic observations of these objects, as well as with future gravitational-wave detections.

----------------------------------------------------------------------

講演者 : 中野 寛之 氏(京都大学)/SPEAKER : Dr. Nakano (Kyoto Univ)
TITLE : Binary Black Holes in General Relativity
DATE : 5/14 (wed) 15:00 ~
LOCATION: F313

ABSTRACT:
Black holes are fantastic objects in Einstein's general relativity, and binary black hole mergers provide very strong, dynamical gravitational fields. Since the breakthroughs in numerical relativity simulations of binary black hole mergers, various collaborative works have been carried out between numerical and analytical relativity, and gravitational wave data analysis. Here, I will review some works related to gravitational waves radiated from binary black holes. And also, I will discuss a recent progress in studies on a binary black hole spacetime.

-----------------------------------------------------------------------

講演者 : Luca Baiotti 氏(大阪大学)/SPEAKER : Dr. Baiotti (Osaka Univ.)
TITLE : General-relativistic simulations of binary neutron star mergers
DATE : 4/16 (wed) 15:00 ~
LOCATION: F313

ABSTRACT:
Scientific interest in binary neutron star systems stems from two main reasons: they are strong sources of gravitational waves, and they are thought to be the engine powering one type of gamma-ray bursts. I will talk about both topics. In particular, I will present my general-relativistic simulations of binary neutron star mergers and of the evolution of the merged object. I will focus also on how we can get information about the equation of state of ultra-high density matter by measuring the gravitational signal from binary neutron star mergers.

----------------------------------------------------------------------
 
講演者 : 矢島 秀伸 氏(エディンバラ大学)/SPEAKER : Dr. Hidenobu Yajima. (University of Edinburgh)
TITLE : Growth of massive black holes in first galaxies
DATE : 4/4 (Fri) 14:00〜
LOCATION: F313

ABSTRACT:
Recent observation have indicated supermassive black holes existed even at z > 7. However, formation and evolution mechanisms of massive black holes (MBHs) are still not understood. The crucial physical mechanism are the angular momentum transport of gas and star formation near galactic centers and accretion onto BHs. Recent cosmological simulations show some fraction of the first galaxies form extended gas disks. At high redshifts, these disks easily become Toomre unstable and cause gas inflow to galactic centers. In this work, we analytically investigate the evolution of the first disk galaxies with central MBHs. We predict formation rate of very massive stars via through core-collapse of star clusters and formation of MBH seeds. If star clusters form near the BHs, some of them can be close to the BHs due to resonant relaxation process, and accrete onto the BHs via tidal disruption. We also discuss the accretion rate of star clusters. Moreover, the first galaxies can be surrounded by high-density Lyman-alpha. We recently suggested a new mechanism of angular momentum transport of gas clouds due to Lyman-alpha radiation drag. We discuss the effect of Lyman-alpha radiation on time scale of migration of accreted gas clouds.

----------------------------------------------------------------------
 
講演者 : Mitch Begelman 氏(コロラド大学)/SPEAKER : Prof. Mitch Begelman (University of Colorado)
TITLE : What Can Tidal Disruption Events Teach Us About Black Hole
DATE : 4/3 (Thu) 14:00〜
LOCATION: F608

ABSTRACT:
For a year or more after a star is tidally disrupted by a black hole, debris can fall back at a rate that greatly exceeds the Eddington limit. Both observations and theoretical arguments indicate that mass loss is unable to regulate the rate at which matter is actually swallowed by the hole, leading to black hole growth rates and energy outputs that can exceed the Eddington limit by orders of magnitude. I will explain why regulation fails in such a case, and explain how this alternate mode of black hole growth could also be crucial for gamma-ray bursts and the rapid growth of supermassive black holes during the epoch of galaxy formation. I will also suggest that hyperaccreting black holes may be associated with the fastest jets, and that these are propelled by radiation pressure instead of magnetic forces.

----------------------------------------------------------------------
 
講演者 : Junhwan Choi 氏(テキサス大学)/SPEAKER : Dr. Junhwan Choi (Univ. of Texas, Austin)
TITLE : Formation of Primordial Super Massive Black Holes
DATE :4/3 (Thu) 11:00〜
LOCATION: F313

ABSTRACT:
In this talk, I will present our recent numerical study on the direct collapse model for the super massive black hole formation. At the beginning, I will briefly review the current models of the primordial super massive black hole formation and their issues, particularly focus on direct collapse model. One of the main questions on this model is how halo gas of ~1kpc scale collapses to sub-pc scale and this collapse maintains the strong gas accretion on a central object. In order to answer these questions, I implemented numerical simulations for isolated halo simulations and cosmological simulations. The simulation results show that J-transfer by non-axisymmetric feature and turbulent gas flow motion play a key role to facilitate the run-away halo gas collapse.




コロキウムの予定表はこちら/ Schedule of colloquium