報告人：肖明，中國科學技術大學
時間：11月1日（周四）15:30
單位：北京師範大學
地點：物理樓106
半導體工業中的摩爾定律似乎正在逼近極限。量子計算吸引了越來越多的注意。本報告將介紹我們在利用半導體器件中單個電子的電荷、自旋、以及電荷-自旋混合態來實現量子比特體系的實驗進展。電荷量子比特可以由皮秒極的電壓脈衝來相干操控，因此其工作頻率很快。我們在砷化鎵材料中實現了一個到三個電荷量子比特。矽材料中的自旋量子比特具有超長的相干時間。我們將介紹多年來開發多層電極的單電子矽器件，並實現自旋量子比特的工作。我們還實現了一種電荷-自旋混合態構成的量子比特，能同時擁有電荷比特超快的工作頻率和自旋比特超長的相干時間。
報告人：鄒旭東，中國科學院電子學研究所
時間：10月30日（周二）10:00
單位：中科院物理研究所
地點：M樓255會議室
This talk will introduce the working principle and design methodology of MEMS based resonant sensor and giving a high resolution accelerometer design as example. A MEMS resonant sensor consists of one or more micromachined resonators and other functional components. Resonators are normally driven into resonance when the sensor in operation. Depending on different sensor designs and applications, the stiffness, mass and/or damping factor of micromachined resonators can be perturbed by the measurand and result in the change of resonant status which can be detected in the format of phase/frequency shift or amplitude/eigenstate variance. The resonant sensing principle scales well with miniaturization and may offer unprecedented sensitivity, large dynamic range with excellent linearity and natural rejection to low frequency noise, which makes it suitable for high precision sensor’s application. In addition, this talk will discuss the fabrication processes required by resonant sensors and how to improve the sensor’s performance by introduce nonlinearity into resonator’s design and operation.
報告人：鄭泉水
時間：10月30日（周二）10:00
單位：中科院物理研究所
地點：M樓253報告廳
Structural superlubricity (SSL), a state of nearly zero friction and wear between two contacted solid surfaces, is one of the most fascinating phenomena of modern tribology. It was theoretically predicted in 1983 and experimentally verified twenty years later in 2004. However, researchers had long believed that larger scale SSL would be impractical until the experimental observation of SSL in microscale graphite in 2012. In this lecture, we shall give a brief review of the state-of-the-arts of SSL. The main part of the lecture will focus on some very promising applications of SSL in technologies.
報告人：Jubee Sohn，CFA
時間：10月30日（周二）12:00
單位：北京大學
地點：KIAA, 1st meeting room
A rich spectroscopic survey provides a unique opportunity to study galaxy clusters and its galaxy populations with a clean sample of spectroscopically identified members. Based on the intensive redshift survey, we explore the structure of local massive cluster Abell 2029 and its surroundings along with X-ray and weak lensing observations. We also investigate A2029 galaxy populations including active galactic nuclei (AGN), star-forming galaxies, E+A galaxies, and quiescent galaxies. In this talk, I will discuss how a dense spectroscopic survey extends our understanding of the evolution of a galaxy cluster.
報告人：Ekkes Brück，Delft University of Technology, Netherlands
時間：10月30日（周二）14:00
單位：中科院物理研究所
地點： M樓238
Magneto-caloric power conversion can be used to convert heat into electricity that up to now was considered as waste. This new technology therefore has the potential to significantly contribute to the energy transition on a global scale.
With the advent of giant magneto-caloric effects (MCE) that occur in conjunction with magneto-elastic or magneto-structural phase transition of first order (FOT), room temperature heat-pump applications became feasible. In this context the MnFe(P,X) system is of particular interest as it contains earth abundant ingredients that are not toxic. This material family derives from the Fe2P compound, a prototypical example known since a long time to exhibit a sharp but weak FOT at 210 K (-63°C).
Magneto-caloric power-conversion calls for a somewhat different combination of properties, in particular a large latent heat that is favourable for a heat-pump, is detrimental for power conversion as a lot of heat is needed to change the temperature. Yet a large change of magnetization is required, which suggests one should either employ materials exhibiting exchange inversion or second order materials. Magnetically highly responsive materials in combination with the field generated by a permanent magnet open the way to new technology for magnetic refrigeration, heat pumps and power generation. Employing the highly efficient coupling between the degrees of freedom of magnetic spins and lattice vibrations in a solid, will render energy conversion and energy generation technologies that get close to the theoretical limits.
報告人：Haipeng An，Tsinghua University
時間：10月30日（周二）14:30
單位：中科院理論物理研究所
地點：Conference Room 6420, ITP new building
Cold dark matter model (CDM) is an extremely successful model to explain the large scale structure of the Universe, corresponding to distances greater than O(Mpc) today. However, some numerical simulations indicate that observations connected with small scales might be in tension with this framework. In particular, simulations based on CDM show that the mass density profile of CDM halo increases as 1/r toward the center, whereas many observed rotation curves of disk galaxies prefer a constant cored density profile. CDM also predicts a greater number of galactic satellites than observed. Observations also show that galactic clusters have mass deficit in the inner O(10) kpc region. In this talk I will present a model in which the dark matter particle is a fermion with a mass around 100 eV, the relic density is generated from the freeze-in mechanism. I will show that in this model the above small scale anomalies can be automatically solved.
報告人：Ying-Cheng Lai，ISS Endowed Professor of Electrical Engineering, ASU
時間：10月30日（周二）15:30
單位：北京師範大學
地點：物理樓106
In this talk, two recently discovered phenomena in Relativistic Quantum Chaos will be discussed: (1) a relativistic quantum chimera in pseudospin-1/2 Dirac material systems and (2) quantum chaotic scattering that defies Q-spoiling and Klein tunneling in pseudospin-1 Dirac-Weyl systems. The first phenomenon is the simultaneous emergence of classically integrable and chaotic dynamics and their quantum manifestations. The distinct relativistic quantum fingerprints associated with different electron spin states are due to a physical mechanism analogous to the chiroptical effect in the presence of degeneracy breaking. The phenomenon mimics a chimera state in classical complex dynamical systems but here in a relativistic quantum setting - henceforth the term 「relativistic or Dirac quantum chimera.」 Potential applications include enhancement of spin polarization, unusual coexisting quasi-bound states associated with distinct spin configurations, and spin selective caustics. The second phenomenon is the surprising occurrence of a class of surface plasmon-like modes in pseudospin-1 chaotic cavities, which maintain high-Q values in spite of fully developed chaos and super-Klein tunneling. This type of boundary modes absolutely has no counterpart in nonrelativistic quantum or even in pseudospin-1/2 systems. Experimental observations of the two phenomena are possible through, e.g., optical realizations of ballistic Dirac or Dirac-Weyl material systems.
報告人：Vladimir Lipunov，Lomonosov Moscow State University
時間：10月30日（周二）16:00
單位：清華大學
地點：物理系理科樓C302
The Advanced LIGO observatory recently reported the first direct detection of gravitational waves predicted by Einstein (1916). The detection of this event was predicted in 1997 on the basis of the Scenario Machine population synthesis calculations (Lipunov et al., 1997). The proximity of the masses of the components of GW150914 is in good agreement with the observed initial mass ratio distribution in massive binary systems, as is used in Scenario Machine calculations for massive binaries.The Multimessenger GW170817/ GRB170817A discovery of the merger of two neutron stars on 17th August 2017 accompanied by a gamma-ray burst and an optical kilonova event is a triumph of the ideas about the evolution of the baryon component in the Universe. Despite the current uniqueness of this observation, the variety of the experimental data obtained makes it possible right now to draw important theoretical conclusions about the origin of the double neutron star, its merger, and the subsequent flare-up of electromagnetic radiation. We demonstrate that the discovery of the merger at a distance of 40 Mpc is entirely consistent with the very first calculations of the Scenario Machine (Lipunov et al. 1987). In modern terms, the predicted rate is ~10000 Gpc-3. Following the discovery of the gravitational-wave source GW170817 by three Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo antennae (Abbott et al., 2017a), the MASTER Global Robotic Net telescopes obtained the first image of the NGC 4993 host galaxy. An optical transient, MASTER OTJ130948.10-232253.3/SSS17a was later found, which appears to be a kilonova resulting from the merger of two neutron stars (NSs). Here we describe this independent detection and photometry of the kilonova made in white light, and in B, V, and R filters.
報告人：Qiwen Zhan，University of Dayton
時間：10月31日（周三）10:00
單位：中科院物理研究所
地點：M樓236會議室
Charge and spin are the two intrinsic attributes of electrons, which pave the way for electronic devices in our daily life. In this talk, I would like to focus on how the interfaces between strongly correlated oxide materials can magically modulate charge and spins of electrons, leading to various exotic physical phenomena. Moreover, by virtue of interfacial coupling in multiferroic heterostructures, we have been able to electrically control electronic properties of intermetallic alloys, which is potential for super low energy-consuming memory applications.
報告人：Simon Blyth
時間：10月31日（周三）10:00
單位：中科院高能物理所
地點：高能所化學樓305會議室
Opticks replaces Geant4 optical photon simulation on the CPU with an equivalent GPU implementation using the NVIDIA OptiX ray tracing engine, resulting in a drastic speedup in optical photon simulation extrapolated to exceed 1000x Geant4 with workstation GPU machines. Generation steps of photons are collected from Geant4 and copied to the GPU allowing optical photons to become fully GPU resident, being generated and propagated entirely on the GPU with only detected photons requiring memory allocation on the CPU. GPU development of the Opticks optical photon simulation has required a first principals approach to techniques such as ray geometry intersection and Monte Carlo sampling and has necessitated the use of uncommon tools such as NumPy, CUDA and Thrust. The presentation will highlight these tools and techniques as well as covering Opticks itself, with the aim of providing an introduction to the power and ease of an alternative NumPy based toolset that can be directly useful for any data analysis.
If you wish to apply GPU acceleration to speedup any algorithm or to simply analyse C++ generated data from the comfort of python then my presentation will provide much to interest you.
報告人：Diogo Buarque Franzosi，Chalmers University of Technology
時間：10月31日（周三）15:00
單位：中科院高能物理所
地點：319 Theoretical Physics Division
Electroweak precision observables as well as more recent LHC measurements push Composite Higgs model into unnatural region, with the vacuum misalignment angle Sinq =v/f \lesssim 0.2. Such values are difficult to achieve from the typical interactions that determine the vacuum alignment. The speaker will show how the techni-sigma scalar excitation might alleviate this problem in a theory of Composite Higgs with a partially composite top quark. He will use unitarity arguments to estimate mass and couplings of this scalar state and discuss the possibility to observe it at the LHC. The work is based on arXiv:1809.09146.
報告人：李田軍
時間：11月1日（周四）12:00
單位：中科院理論物理所
地點：理論物理所322報告廳
Supersymmetry provides an elegant solution to gauge hierarchy problem as well as a partial solution to cosmological constant problem. In the Supersymmetric Standard Models (SSMs), gauge coupling unification can be realized, the lightest supersymmetric particle can be a dark matter candidate if R-parity is conserved, and the electroweak symmetry can be broken radiatively, etc. In addition, gauge coupling unification strongly implies the Grand Unified Theories (GUTs), which are consistent with string model building. Thus, supersymmetry is a bridge between the promising new physics beyond the Standard Model and the fundamental physics. However, the current LHC supersymmetry searches give strong constraints on the viable parameter space of the SSMs, which leads to the supersymmetry electroweak fine-tuning problem. The natural supersymmetry and the super-natural supersymmetry have been proposed to solve this problem, and we shall briefly comment on their collider searches.
報告人：Jason Xavier Prochaska，UCSC
時間：11月1日（周四）14:00
單位：清華大學
地點：蒙民偉科技南樓S727
I will review our series of successful programs to dissect the interstellar medium of distant, star-forming galaxies with the Atacama Large Millimeter Array (ALMA). In particular, I will discuss surveys of the set of HI-selected galaxies known as the damped Lya systems (DLAs). We resolve, in part, a decades old struggle to identify the galactic counterparts of these DLAs and thereby place them firmly in the modern picture of galaxy formation. I will also highlight high spectral and spatial resolution observations of the Wolfe Disk, a z~4 galaxy with a Milky Way-like rotation curve.
報告人：Hui Li，Los Alamos National Laboratory
時間：11月1日（周四）16:00
單位：北京大學
地點：KIAA-PKU Auditorium
In the recent years, high spatial resolution observations of such disks by ALMA have revealed many details that are providing interesting constraints on the disk physics as well as dust dynamics, both of which are essential for understanding planet formation. We carry out high-resolution, 2D and 3D hydrodynamic simulations of global disks, including the effects of dust feedback. We find that a variety of instabilities can occur in PPDs which lead to both the quasi-axisymmetric rings and non-asymmetric dust traps. In particular, we find that quasi-axisymmetric dust rings can be subject to a new instability due to dust-gas interactions and this could provide several observational signatures that can be tested. These effects are providing additional understanding of dust dynamics in PPDs. We also produce synthetic dust emission images using our simulation results and discuss the comparison between simulations and observations.
報告人：Dirk H. Rischke，德國法蘭克福大學
時間：11月1日（周四）16:00
單位：清華大學
地點：理科樓鄭裕彤講堂
Relativistic hydrodynamics has been successfully applied to describe the collective evolution of hot and dense matter created in collisions of heavy atomic nuclei at particle accelerator facilities such as the Relativistic Heavy Ion Collider at Brookhaven National Laboratory and the Large Hadron Collider at CERN. In this talk, I will try to summarize the main achievements, but also potential problems in applying a theory valid at macroscopic length scales to systems which consist only of several thousand particles.
報告人：James Aird，University of Leicester
時間：11月2日（周五）12:00
單位：北京大學
地點：KIAA, 1st meeting room
Determining how the evolution of galaxies is related to the growth of their central black holes – seen as Active Galactic Nuclei (AGN) – remains a major challenge. Variability in AGN activity on short timescales compared to changes across the host galaxy can wash out underlying correlations between galaxy and AGN properties, resulting in a complex and biased observational picture. I will present work that addresses these issues, starting from near-infrared selected samples of galaxies and measuring the distribution of AGN accretion rates within such samples using deep Chandra X-ray data. We thus trace the incidence of AGN as a function of stellar mass and star formation rate over a broad range in cosmic time (z~0.1-4). We first consider star-forming galaxies that lie along the main sequence and show that the incidence of AGN (quantified in terms of the AGN fraction or average specific accretion rates) is correlated with the SFR, indicating that AGN activity is primarily related to the amount of cold gas in a galaxy. We also consider galaxies with a broader range of SFRs relative to the main sequence, finding evidence for an enhanced incidence of AGN and indicating that a broader range of mechanisms are responsible for the triggering and fuelling of AGN across the galaxy population.
報告人：韓愈，信陽師範學院
時間：11月2日（周五）13:30
單位：北京大學
地點：科技樓C區602
To search for the observational effects of loop quantum gravity， a powerful approach called 「anomaly-free algebra」 in loop quantum cosmology has been systematically constructed during the past decade. In this talk, I will give a concise introduction of the basic idea and talk about the recent developments of this approach.
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