我的新书《Meaning of the Wave Function: In search of the ontology of quantum mechanics》已经完稿,将由 剑桥大学出版社 于明年初出版。这里是书的前言，目录和推荐语。 Mwf book by Shan Gao preface.pdf A thoughtful survey of the many issues arising from the question: Does the quantum mechanical wave function represent physical reality? Gao's book will provoke stimulating discussions among physicists and philosophers of science. --- Stephen L. Adler, Institute for Advanced Study, Princeton, author of Quantum Theory as an Emergent Phenomenon This book discusses in great detail the fundamental problem of the conceptual and philosophical status of the quantum wavefunction. The remarkable deepness and completeness of the analysis and the appreciable and objective way of the author in discussing divergent positions render the book a useful tool of investigation. I unrestrictedly recommend this work to all people interested in contributing to clarify the most intriguing aspects of the measurement problem and the various obscure and debated aspects of quantum mechanics. --- GianCarlo Ghirardi, University of Trieste and ICTP, Trieste, author of Sneaking a Look at God's Cards A profound book for a deep question. --- Nicolas Gisin, University of Geneva, author of Quantum Chance The meaning of the wave function is a problem encountered by all students of quantum mechanics. The wave function is usually attributed just a probabilistic significance but might it have other characteristics - could it be a physical field? Shan Gao's admirable book is the first to present a comprehensive analysis of this fundamental topic. Drawing upon recent thinking, the author presents a readable up-to-the-minute assessment of the various viewpoints on the significance of the wave function. The book provides an excellent introduction to this key area in the foundations of physics. --- Peter Holland, University of Oxford, author of The Quantum Theory of Motion The reality or unreality of the quantum wave function is a topic of lively debate in the foundations of quantum mechanics. In this thoughtful and thought-provoking book, Shan Gao offers nothing less than a novel realist interpretation of the wave function, as describing the propensities of particles undergoing random discontinuous motion. It is a book that everyone interested in the ongoing debates will want to take a look at. --- Wayne Myrvold, Western University, co-editor of Studies in History and Philosophy of Modern Physics 补记：书的初稿可以从下述链接下载 https://arxiv.org/abs/1611.02738 http://philsci-archive.pitt.edu/12608/ https://gucas.academia.edu/ShanGao
Why am I not buying the story of gravitational wave discovery? Huang Zhixun, Beijing From the beginning of the 20 th century up until now, the scientific knowledge and experience of humankind havebeen increasing exponentially, yet in some areas research work is makingessentially no progress. The searches of gravitational waves and gravitons areapparently such examples, and just a few years ago some European and American physicistshad even complained that “this would constitute an almost impossible task”.However, on February 11, 2016 the National Science Foundation (NSF) of the United Statesannounced the “detection” of gravitational waves, and the news quickly spreadto the whole world. It is recalled that in the year of 1887 H. Hertzdiscovered, by means of experiments, electromagnetic waves which had been predictedby Maxwell, and for the next 130 years since then, this discovery hastremendously impacted human life. Hence it is reasoned that, shouldgravitational waves exist, its discovery would be a major scientific event. Onthe other hand, the Chinese physicist Li Miao ( 李淼)believes the recentannounced discovery is only the beginning of human endeavor to search and studygravitational waves, since multiple wave sources could exist and the source incurrent focus is only one of them and that this source lies so far away that itis even beyond the Milky Way Galaxy. I interpret what he says as, whether theexistence of gravitational waves as a general physical law like that of electromagneticwaves is still a question to be searched and answered. On the November of 1915, A. Einstein presented aseries of four papers to the Prussian Academy, and thus heestablished a new theory called general relativity (GR), which wasfundamentally different from his theory of special relativity (SR) proposed in1905. In GR space and time are unified into one and the same entity calledspacetime, and matter distribution determines the curvature of spacetime. Henceit is believed that, just as an accelerated electric charge source wouldgenerate an electromagnetic wave, the acceleration of matter would create theso-called gravitational wave, and such a wave is actually the propagation of theso-called changing spacetime curvature. On the January of 1918, Einsteinpublished his paper titled “über Gravitationswellen (On GravitationalWaves), where it was proposed that gravitational waves are transverse waves andthat they propagate with the speed of light. 。 In recentyears I have reiterated that there is no such things as gravitational waves.Why is it so? I have consistently objected to the behavior of some Chinesescientists in misleading the government into appropriate huge sum of money ontothese “gigantic projects”, and especially against the manner they blindlyfollow their western counterpart, and I strongly favor the establishment of thefundamental and foundational science subjects with Chinese characteristics.What’s more, I have cited many and widespread evidences to demonstrate that,the number of creative scientific results is not necessarily proportional tothe amount of money that is put into them, and such counterexamples are widelyseen. It is for this reason that I do not support the search of dark matter,dark energy, and gravitational waves. Some time ago China sent a satellite into orbitto detect dark matter, yet a leading scientist responsible for the projectclaimed that no one can guarantee the existence of such dark matter. Regardingto scientific programs in terms of billions of dollars, such a saying is notonly arbitrary but also repugnant. …… And to make things worse, projectseven in tens of billions are in preparation or progress. The development offundamental sciences does indeed need the government put into money into them,and there is nothing wrong about this; yet as to the question of how toproperly or wisely spend these money, scientists in both China and abroadshould exercise judgement and discretion. As for Chinese scientists, it isespecially important that we walk our own way in making our countryscientifically thriving, and it is apparently not appropriate to decorate ourfuture with what others had created in their past. Focusing onthe particular project of gravitational waves detection, I don’t think it isthe right thing for us Chinese physicists to do by simply acting as the pupilsof Western scientists. Let us begin with a simple analysis of this subjectbased on fundamental physics, and it is a well-established fact that theclassical mechanics (CM) founded by Newtonhas clearly formulated the definitions of such fundamental concepts as space,time, and gravity. The SR proposed by Einstein in 1905 does not include theconsideration of gravity, and Minkowski said in 1908 that “from now on, boththe concepts of space and time will disappear, and what only remains is thecombination of the two as a single entity”—here he was refering to the conceptof spacetime. This concept of spacetime immediately made its presence into the GRpublished in 1916, which was then developed into a theory of gravitationalwaves—i.e., matter causes curvature in spacetime, and when an object isaccelerated, it radiates out ripples in the form of curved spacetime which is inturn called gravitational wave and which travels at the speed of light, and itis further believed that the larger the mass of the object, the greater theamplitude of its gravitational wave. Yet nowherein any specialized books or literature on metrology can we find an independentphysical quantity called spacetime (or timespace). In physics, the dimensionfor time is s (second), and the dimension for space is m 3 where mrepresents meter, so the dimension for spacetime is expected to be sm 3 or m 3 s, yet this expression represents neither an independentphysical concept nor does it have an inherent and unambiguous physical meaningor content. Metrology is built on the measurablility of a physical quantity orconcept, yet sm 3 or m 3 s clearly does not satisfy thiscondition, hence what the concept of spacetime tries to convey is not clear atall, and therefore scientifically meaningless. Therefore it is just naturalthat literature on metrology does not deal with this concept of spacetime, andMinkowski’s above saying is unjustifiable. The unification of space and time isthe theoretical foundation of GR, yet this foundation is very questionable. Next, certainstatements in relativistic mechanics are not acceptable to me at all. Firstly,GR does not regard gravity as a force and only uses geometric terms to describeit; further, there is no gravity under (flat) spacetime without curvature, andonly when spacetime is curved does gravity exist. Yet, as for the question ofwhat the essence of gravity is in relativistic mechanics, GR never answers itin an affirmative way; nor can a formula be found in relativistic mechanics soas to calculate the magnitude of gravity, and how can this situation beacceptable?! I believe spacetime is only a concept adopted for the purpose ofmaking physical analysis, and in no way it represents the physical reality.Given these facts, I certainly do not accept the existence of the so-calledgravitational waves. Then,there is the question of the propagation speed of the so-called gravitationalwaves, and travellingat light speed c seems to suggest that they belong to the electromagneticspectrum family, yetnothing is more absurd than this! Gravitational theory has been developed independentof, and parallel to, electromagnetic theory, and the former can certainlyborrow ideas andmethods from the latter, but how can it be that the so-called gravitationalwave is simply assigned the speed c of electromagneticwaves (or light) ? Within the particle family of the Standard Model, elementaryparticles are classified into three basic types: hadron, lepton, andpropagator, and within the category of propagator, there are bosons which actas carrier for weak nuclear force, gluons as carrier of strong nuclear force,and photons as carrier of electromagnetic force. According to GR, the carrierfor gravity force (actually there is no such force as gravity in GR) isgraviton, yet search of graviton in a period of many years has failed to findits trace at all. But this isonly one of many difficulties faced by this theory, for other examples: Ifgravitational wave doesexist and does travel at the speed of light, then gravitons would also travelat the speed of light,i.e., same as photons, which conclusion is far-fetched and ridiculous. In fact,many researchershave pointed out that the propagation speed of gravity is far exceeding thespeed of light(but not infinity), and what is being referred to here by the term of gravity isapparently not gravitationalwaves either. It can be inferred that the existence of gravitational waves,just as that ofgravitons, is very dubious, and at least it needs to be further studied; butwhat obviously is not needed ispropaganda and brainwash. Lastly, we have noticed that the way forthe LIGOs in the United States to find the so-called gravitational waves is to “receivea signal”—two detectors with a separation of around 3000 km both received the samesignal, or waveform, but with a time difference of 7.1 ms, which seems not tobe a reliable and trustworthy way of making a scientific discovery, since youcannot be absolutely certain that it is indeed caused by gravitational waves.The time for the receipt of this signal is 23:50 on September 14, 2014, andalthough the signal-to-noise ratio was relatively high, yet there is still a possibilitythat it was caused by other factors, for example, slightterrestrial quake or vibrating motions between the two detectors. It iswell known that, when collecting scientific evidence or reading data,scientists sometimes tend to regard, whether intentionally or unintentionally,what is unknown as what they are searching for. At least it can be assertedthat, the current discovery regarding gravitational wave, is still somedistance away from the assurance brought about by what Hertz discovered by hiselectromagnetic experiments in 1887, and it certainly needs further work todetermine whether what the LIGOs have found is a scientific truth or just adisturbance or distraction. February 15, 2016; by Huang Zhixun (The author of this note is a professor andPh. D supervisor at the Communication University of China in Beijing) emai : huangzhixun@gmail.com,wellkome to discuss
WavePOD project secures ￡2 million from Wave Energy Scotland 3 Aug 15 The vision of a standardised offshore electricity generator for the wave industry has taken a major step forward with the announcement of ￡2 million new funding for a project run jointly by Aquamarine Power, Bosch Rexroth and Carnegie Wave Energy. The WavePOD (Wave Power Offtake Device) aims to develop a standardised subsea unit which can be attached to a variety of different wave energy devices and converts the movement of such a device into electricity. This is one of the major hurdles facing the industry. A tenth-scale WavePOD prototype has already been built and is undergoing a rigorous test programme at the world-leading Institute for Fluid Power Drives and Controls (IFAS) at RWTH Aachen University, Germany. The project has secured ￡2 million new funding from Wave Energy Scotland, which will enable the team to complete testing of their scale prototype and deliver the design and specification for a full-scale prototype WavePOD. Commenting on the new investment, Aquamarine Power Chief Executive Officer Paddy O'Kane said: The WavePOD project addresses head-on one of the major challenges in the wave energy sector - how to convert the motion of a wave machine into electricity, both reliably and cost effectively. From the outset we have worked with Bosch Rexroth to ensure WavePOD will be applicable to a wide range of technologies. The very welcome involvement of Carnegie Wave Energy and the investment by Wave Energy Scotland means we can now take our plans on to the next stage. We have already generated extremely positive results from our tenth-scale prototype in Germany and we are now in an ideal position to build on this success. Fergus Ewing, Minster for Energy, the Scottish Government commented: Wave Energy Scotland is running the biggest technology programme the wave sector has ever seen. Therefore I am delighted to see the first contracts being awarded to technology developers. Scottish businesses are involved in the overwhelming majority of the projects and this is testament to the number of innovative companies operating in Scotland. The WavePOD tenth-scale prototype comprises a drive train, cylinder frame and power take off and has been developed by Bosch Rexroth and Aquamarine Power with funding support from the Scottish Government's Marine Renewables Commercialisation Fund (MRCF), managed by the Carbon Trust. In addition to the lead project partners, the WavePOD programme has already attracted support from some of Europe's leading wave energy developers, utilities and academic institutions. Commenting on the project to date, Paddy O'Kane said: We have already learned a tremendous amount through the design, build and commissioning of the tenth-scale WavePOD prototype. We have been generating electrical power since October and the drive train is using real-life hydrodynamic data from Oyster 800 to ensure the power take off is experiencing exactly the same loads it would encounter at sea.
Google map 无疑凝聚了许多当代最先进的科学和技术。前一阵子听说有人还用它做出了科学上的重要发现 — 从 googlemap 上他看到有一块绿色的区域没有任何标识，于是他按图索骥找到那个地方，发现了一处不为人知的热带雨林。 我们虽然不期待做出重大发现，但是透过精美的 google map 图片，能够看到其中蕴含的一些物理规律还是非常有趣的。这篇博文要讲的就是 google 的卫星拍下来的船在水面留下的波纹。 如图一所示，在一些港口，河流附近，很容易发现一些非常清晰的行船照片。图一来自上海黄浦江。我们注意到船的后面留下了一个精致的波纹图案。这个被称作兴波（ wake ）的波纹与许多人熟悉的“马赫角”有些关系。 图一：黄浦江上的船波。 当飞机，子弹等以超音速在空气中飞行时，它们所激发起来的声波被落在了身后，如图二所示。子弹在 A 点处激发起来的各种频率的声波向外扩张（图中以 A 为圆心的圆代表了声波的波前），由于各种频率的波具有相同的速度，所以它们齐头并进。当 t 时刻，子弹到达 B 点时，声波的波前到达了 O 点。 BO 两点的连线与 AB 的夹角满足 , 即声波速度与子弹速度之比。此角为马赫角。容易证明， AB 连线上其他点所发出的声波的波前在 t 时刻也到达了 BO 连线上。所以所有声波的能量都被局限在了马赫角内。通过测量马赫角的大小，以及对声波速度的了解（大约三百多米每秒），我们就能推断出子弹的速度来。图三上图显示了子弹的马赫角，而图三下图则显示了飞机的速度刚刚超过声速时，突破所谓“音障”，此时马赫角 度（图片来自网站 http://www.acs.psu.edu/drussell/Demos/doppler/doppler.html ）。 图二：马赫角。 图三：马赫角的实例。 那么我们能否通过测量船身后的波纹所形成的夹角来推算出船的速度呢？一百多年前，伟大的开尔文勋爵告诉我们这是不可能的。他的计算显示，不论船的速度大小，其波纹形成的夹角始终为 39 度多一点。因此船的波纹被称为 Kelvinwave 。 那么船在水面的波纹与子弹在空气中的“波纹”为什么会有如此大的差别呢？这完全来自于空气和水的不同色散关系。空气中所有声波，不论波长的长短（在一定的波长范围内），都有相同的声速，这被称为没有色散的介质；而水面上的波纹，波长越长的速度越大（适用于深水区），这被称为有色散的介质。 图四显示了这两种介质的不同。图四上图是空气中的情形 ，下图是水面的情形。空气中，由于各种声波的速度都一样，在某一时刻， O 点处接收到的声波都是从 A 点发出的，从其他点发出的声波无法达到 O 点（如图中的红色圆圈代表从 C 点发出的声波），所以 BO 连线上的点总是能接收到单一波源发出的很强的声波，不会由于不同波源之间的干涉而减弱。而水面的情况就不一样了。因为任何一点发出的水波的波长有长有短，波速也有快有慢，所以从 A 点发出的某一种波长的水波和从 C 点发出的更长波长的水波可以在 O 点相遇形成干涉。实际上， AB 连线上的各点发出的波都有可能在 O 点相遇，通常情况下由于这些波的相位，波长和波速千差万别，它们会在那里干涉相消，从而看不到波纹。 图四：无色散与有色散的介质。 可以计算表明（见参考资料 1 ， 2 ），水面上从 A 点发出的各种波长的波，与其他点发出的波干涉之后，只在一个有限的区域内不会干涉相消，这个区域如图五所示，它是一个圆， A 是圆周上的一点，圆的直径 AC 等于船行驶距离 AB 的一半。这样，所有的水波都被局限在了一个夹角内，其角度 满足 ，即 约为 19 度，也就是说 BO 和 BO’ 之间的角度为 38 度左右。图一中黄浦江上的船后面形成的波纹夹角就为 35 度左右，考虑到一些测量和照片的误差，已经非常接近理论预期了。 图五：计算船波夹角。 用某个物理学家的话说，无论是一只鸭子还是一艘万吨巨轮，其身后留下的波纹形状都是类似的。物理之美也许就体现在这里了吧！ 参考资料： 1：Scientific American 1988 年的相关文章 http://jesseenterprises.net/amsci/1988/02/1988-02-fs.html 2：H. D. Keith, Simplified Theory of Ship Waves, American Journal of Physics, 25, 466(1957)
http://cpb.iphy.ac.cn/EN/abstract/abstract52170.shtml Simulating regular wave propagation over a submerged bar by boundary element method model and Boussinesq equation model Li Shuang a b , He Hai-Lun c a Department of Ocean Science and Engineering, Zhejiang University, Hangzhou 310058, China; b Key Laboratory of Ocean Circulation and Waves, Chinese Academy of Sciences, Qingdao 266071, China; c State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, SOA, Hangzhou 310012, China Abstract: Numerical models based on boundary element method and Boussinesq equation are used to simulate the wave transform over a submerged bar for the regular waves. In the boundary-element-method model the linear element is used, and the integrals are computed by analytical formulas. The Boussinesq-equation model is the well-known FUNWAVE from the University of Delaware. We compare the numerical free surface displacements with the laboratory data on both gentle slope and steep slope, and find that both the two models simulate the wave transform well. We further compute the agreement indexes between the numerical result and laboratory data, and the results support that the boundary-element-method model has a stable good performance, which is due to the fact that its government equation has no restriction on nonlinearity and dispersion as compared with Boussinesq equation Cite this article: Li Shuang,He Hai-Lun. Simulating regular wave propagation over a submerged bar by boundary element method model and Boussinesq equation model. Chin. Phys. B, 2013, 22(2): 024701.
Function dn4000a,wave,flux,select=select ;+ ;NAME: ; dn4000a ;PURPOSE: ; compute 4000A break ;CALLING SEQUENCE: ; result=dn4000a(wave,flux,select=select) ;INPUT: ; wave --- rest frame wavelength in Unit:A ; flux --- flux ;OUTPUT: ; dn_4000 --- 4000A break ;REVISION HISTORY: ; Original by DL.Wang,Dec-05-2007 ;- if not keyword_set(select) then begin print,'wavelength limit select:' print,'--------------------------------------------' print,' 1: Bruzual 1983' print,' 2: Balogh 1999' print,'--------------------------------------------' read,select endif case select of 1:wavelimit= 2:wavelimit= endcase wave_blue=where(wave ge wavelimit and wave le wavelimit ,blue) wave_red=where(wave ge wavelimit and wave le wavelimit ,red) if blue gt 0 and red gt 0 then begin flux_blue=int_tabulated(wave ,flux *wave *wave ) flux_blue_mean=flux_blue/(wavelimit -wavelimit ) flux_red=int_tabulated(wave ,flux *wave *wave ) flux_red_mean=flux_red/(wavelimit -wavelimit ) dn_4000=flux_red_mean/flux_blue_mean endif else begin dn_4000=-999.9 endelse return,dn_4000 End
Function mag2flux_2mass_cohen, mag, wave=wave, z=z, band=band, $ slope=slope, fd_per_a=fd_per_a, fd_per_hz=fd_per_hz, jy=jy ;+ ;NAME: ; mag2flux_2mass_cohen ;PURPOSE: ; compute 2MASS monochrontic flux from magnitude ;CALLING SEQUENCE: ; result=mag2flux_2mass_cohen(mag,wave=wave,band=band,slope=slope,/A) ;INPUT: ; mag ---- 2MASS magnitude ;OPTION KEYWORD INPUT: ; wave ---- wavelength at which the monochromatic flux to be ; calculated. (Unit:micrometer) ; if z (redshift) keyword is specified then this means ; the wavelength in the rest frame of the object at z ; z ---- redshift; unspecified if only observed frame is ; concerned ; slope ---- spctral slope in wavelength space ; S_nu=A*nu^(-slope) ; band ---- string, one of the following ; 'J','H','Ks' ;OUTPUT: ; flux at given wavelength as lambda*f(lambda) ; in erg/s/cm2 (default) ; If output keyword specified, then ; /fd_per_a: return flux density in erg/s/cm2/A ; /fd_per_hz: return flux density in erg/s/cm2/Hz ; /jy: return flux density in Jy ;METHOD: ; see Cohen Martin, Wheaton Wm.A, Megeath S.T ; Astronomical Journal, Volume 126,1090 ; 'Spectral Irradiance Calibration in the Infrared. ; XIV. The Absolute Calibration of 2MASS ' ;REVISION HISTORY: ; Original by DL.Wang,Oct-12-2007,Fri ;- if not keyword_set(z) then z=0. ; default no redshift ;transform wavelength from micrometer to A waveA=wave*1.0D+4 ;transform wavelength from observation frame to rest frame wave_z=waveA*(1.0+z) ;light velocity in vcaurme(A/s) lightspeed=2.998D+18 ;effective wavelengths of J, H, Ks in Unit (A) effwave = ; zero point offset zpoff = ;0mag Flux in Jy Flux_nu = ;0mag Flux in W*(cm^-2)*(micrometer^-1) Flux_lamda = case band of 'J':begin Flux_nu0=Flux_nu Flux_lamda0=Flux_lamda zpoff0=zpoff ewave=effwave end 'H':begin Flux_nu0=Flux_nu Flux_lamda0=Flux_lamda zpoff0=zpoff ewave=effwave end 'Ks':begin Flux_nu0=Flux_nu Flux_lamda0=Flux_lamda zpoff0=zpoff ewave=effwave end endcase flux_hz=Flux_nu0*10.0D0^(-0.4*(mag+zpoff0)) flux_A=Flux_lamda0*10.0D0^(-0.4*(mag+zpoff0)) flux_A_z=flux_A*(wave_z/ewave)^(-2.0+slope) flux_hz_z=flux_hz*(wave_z/ewave)^(-slope) if keyword_set(jy) then C00=1.0D-23 else C00=1.0D0 flux=wave_z*flux_A_z*1.0D3 flux0=(lightspeed/wave_z)*flux_hz_z*1.0D-23 print,'flux A :',flux print,'flux Hz:',flux0 if keyword_set(fd_per_a) then begin return,flux/waveA endif else begin if keyword_set(fd_per_hz) then begin freq = lightspeed/waveA return,flux0/freq/C00 endif else return, flux endelse End
Doppler instability of antispiral waves in discrete oscillatory reaction-diffusion media 2010 Chinese Phys. B 19 050513 Qian Yu(钱郁), Huang Xiao-Dong(黄晓东), Liao Xu-Hong(廖旭红), and Hu Gang(胡岗) This paper investigates antispiral wave breakup phenomena in coupled two-dimensional FitzHughNagumo cells with self-sustained oscillation via Hopf bifurcation. When the coupling strength of the active variable decreases to a critical value, wave breakup phenomenon first occurs in the antispiral core region where waves collide with each other and spontaneously break into spatiotemporal turbulence. Measurements reveal for the first time that this breakup phenomenon is due to the mechanism of antispiral Doppler instability. 这是一起在篮球场上疯过的兄弟写的一篇文章，今天才读了读，图文并茂，比起PRE的有些文章，也差不了哪去。有如下感觉： 1.反螺旋波的多普勒不稳定性，或称之为失稳，的确是第一次见有人讨论。不仅如此，振荡介质中正常螺旋波的多普勒失稳也是鲜有文献讨论。常见的这方面讨论都是基于可激发体系。然而可激发体系的螺旋波失稳与振荡的都一样吗？从机理到现象的对比，目前还没见报导，我也正在这方面做点东西。 2.因为是离散的模型，所以其找波尖或称波头，就是tip，不可能找出个空间准连续的轨迹来，推测（已通过讨论证实）是用的类似Ezspiral中所用的方法，即插值。关于波头的定义讨论，我也将写入工作总结之中，尽管简单，但却是讨论这类问题的基础。 3.为何其图2的后两个图出现了方形的包络，而且这个轨迹图是最终结果的叠加，如果给出随时间的变化来，可能那猪耳朵不是近乎连续变动的。这图没有给出轨迹的总体大小，也许只在一个相邻距离之内吧？ 4.给出了图4螺旋波失稳的机理：多普勒效应，也用一维模拟予以证实。但仍然没有给出为何会失去稳定性。对应Eckhause失稳，那是长波扰动造成的，这里多普勒失稳是什么机理呢？可激发介质中，Barkley给出了稳定性分析方法，但这也正是我的困惑所在，能直接推广到振荡介质吗？ 5.对应模型的连续介质会不会也出现这样的情况呢？这里反螺旋波与正螺旋波，我感觉对失稳没有什么影响，当然我也是想当然，没有验证。
http://pre.aps.org/abstract/PRE/v81/i6/e066202 Computation of the drift velocity of spiral waves using response functions Abstract: Rotating spiral waves are a form of self-organization observed in spatially extended systems of chysical,chemical, and biological nature. In the presence of a small perturbation, the spiral waves center of rotation and fiducial phase may change over time, i.e., the spiral wave drifts. In linear approximation, the velocity of the drift is proportional to the convolution of the perturbation with the spirals response functions, which are the eigenfunctions of the adjoint linearized operator corresponding to the critical eigenvalues =0, +-omega. Here, we demonstrate that the response functions give quantitatively accurate prediction of the drift velocities due to a variety of perturbations: a time dependent, periodic perturbation inducing resonant drift; a rotational symmetry-breaking perturbation inducing electrophoretic drift; and a translational symmetry-breaking perturbation inhomogeneity induced drift including drift due to a gradient, stepwise, and localized inhomogeneity. We predict the drift velocities using the response functions in FitzHugh-Nagumo and Barkley models, and compare them with the velocities obtained in direct numerical simulations. In all cases good quantitative agreement is demonstrated. 这是作者所在研究组一系列文章的一个总结类文献，理论基石仍然是第二作者，D. Barkley在上世纪九十年代发展的稳定性分析。 如其所言，计算response 函数的复杂性让一般，习惯于直接模拟的研究者有点发怵，别人我不敢说，对于我是这样的。 我感兴趣的是其中的resonant drift.
Citation: Cavaleri L., Alves J.-H.G.M., Ardhuin F., Babanin A., Banner M., Belibassakis K., Benoit M., (...), Young I. Wave modelling - The state of the art (2007) Progress in Oceanography ,75(4),pp.603-674. Abstract This paper is the product of the wave modelling community and it tries to make a picture of the present situation in this branch of science, exploring the previous and the most recent results and looking ahead towards the solution of the problems we presently face. Both theory and applications are considered. The many faces of the subject imply separate discussions. This is reflected into the single sections, seven of them, each dealing with a specific topic, the whole providing a broad and solid overview of the present state of the art. After an introduction framing the problem and the approach we followed, we deal in sequence with the following subjects: (Section) 2, generation by wind; 3, nonlinear interactions in deep water; 4, white-capping dissipation; 5, nonlinear interactions in shallow water; 6, dissipation at the sea bottom; 7, wave propagation; 8, numerics. The two final sections, 9 and 10, summarize the present situation from a general point of view and try to look at the future developments. Keywords: Wind waves; Windwave generation; Wavewave interaction; Wave propagation; Wave dissipation; Wavecurrent interaction; Numerics Article Outline 1. Introduction 2. Brief review of windwave generation 2.1. Linear theory 2.2. Nonlinear effects 2.3. Gustiness 2.4. Open issues 2.4.1. Damping of low-frequency swells 2.4.2. Momentum transfer for high wind speeds 2.4.3. Quality of modelled wind fields 3. Modelling nonlinear four-wave interactions in discrete spectral wave models 3.1. Theory 3.2. Solution methods 3.3. Properties 3.4. Development in computational methods 3.5. Inter-comparison of computational methods 3.6. Questions and actions 4. Spectral dissipation in deep water 4.1. Theoretical and experimental research of physics of the spectral dissipation 4.1.1. Spectral dissipation due to wave breaking 4.1.2. Waveturbulence interactions 4.1.3. Wavewave modulations 4.2. Modelling the spectral dissipation function 5. Nonlinear interactions in shallow water waves 5.1. Nonlinearity in shallow water 5.2. Deterministic models: time-domain and spectral-domain 5.3. Stochastic models 5.4. Dissipation and wave breaking in shallow water 5.5. Open problems 6. Bottom dissipation 6.1. Wave energy dissipation due to bottom friction 6.1.1. Common formulations for spectral wave models: waves only 6.1.2. Common formulations for spectral wave models: waves and currents 6.1.3. Bottom roughness models for movable beds 6.2. Energy dissipation due to wavebottom interaction 6.3. Discussion and outstanding problems 7. Wave propagation 7.1. Dispersion, geometrical optics and the wave action equation 7.2. Limitations of geometrical optics: diffraction, reflection and random scattering 7.3. Waves over varying currents, nonlinear wave effects and the advection velocity 7.4. Waves blocking 7.5. Unsteady water depths and currents 7.6. Waves in the real ocean 8. Numerics and resolution in large-scale wave modelling 8.1. A description of the problem 8.1.1. Error due to the numerical scheme for geographic propagation on a grid 8.1.2. Diffusion 8.1.3. Numerical dispersion 8.1.4. Combined effect of diffusion and dispersion 8.1.5. Error due to the numerical scheme for spectral propagation 8.1.6. Error due to coarse geographic resolution 8.1.7. Error due to coarse spectral resolution 8.1.8. Errors in source term integration 8.2. Existing solutions 8.2.1. Improved numerical schemes for propagation on a grid 8.2.2. Alternatives to the finite difference schemes on a grid 8.2.3. Addressing error due to coarse geographic resolution 8.2.4. Garden sprinkler effect correction methods 8.2.5. Errors in source term integration 8.3. Relative importance of problem 8.3.1. Error due to the numerical scheme for geographic propagation 8.3.2. Argument 8.3.3. Counter-argument 8.3.4. Error due to the numerical scheme for spectral propagation 8.3.5. Geographic resolution 8.3.6. Spectral resolution 8.3.7. Source term integration 8.4. Future solutions 8.4.1. The numerical scheme for geographic propagation 8.4.2. Geographic resolution 8.4.3. Spectral resolution 8.4.4. Errors in source term integration 8.5. Numerics and resolution: problems particular to finite depth and high resolution applications 9. Where we are 10. Where to go Acknowledgements References
Google Wave在大多数人都还没有见识过之时，就已经too hot to be ignored。 Google Wave中， 用户能直观他人打字全过程，即便所输入内容过后被删除了。 （Ref: http://www.yeeyan.com/articles/view/36520/63177）突然想起当年在MSRA面试的时候，一位老兄问过，如果提高用户输入错误时的更正提示正确性。我回答了一个，记录用户修改自己输入的pattern，因为输入时，由于键盘位置的布局，由于我们手指的运动习惯，敲错字母是有规律性的。当时考官兄有些意外，说没人回答过这个答案。不知道现在有人做出了这样的产品没。
Nerve signals may be shock wave riders: Wired has a good break down of theory that says that nerve cells don't work on electricity as we assume, but instead transmit signals using pressure waves, and crucially, this might explain how anaesthetics work. The idea that nerve cells send their signals as pressure waves is not brand new. Known as the Soliton model , it was first published in 2005 by Drs Andrew Jackson and Thomas Heimburg and was thought a bit of a curiosity. It challenges the model of nerve cell functioning that was developed by Alan Hodgkin and Andrew Huxley, both of whom won the Nobel prize for their work. Their discovery was that nerve cells can be understood as electrical circuits and that the transmission of nerve signals or action potentials can be described using a simple elegant mathematical formula. This formula describes how nerve cells work remarkably well and is still the basis of much modern neuroscience. So suggesting that the Hodgkin-Huxley model is wrong is likely to piss a lot of people off, and that's exactly what the Soliton model has done. However, this new paper suggests it could explain how anaesthetics work, which is one of the mysteries of modern neuroscience. It's a totally left-field idea, but if it works out, it would be a revolution in both neuroscience and medicine. Quantum model of nerve pulse I: Soliton model of nerve pulse In the first part of series I will briefly summarize soliton model of nerve pulse proposed by Danish researchers . The temperature of the axon is slightly above the critical temperature T c for the phase transition leading from crystal like state of the lipid layers to a liquid crystal state. Near criticality the elastic constants and heat capacity of the membrane vary strongly and have maxima at criticality so that also sound velocity varies strongly near criticality. Also the relaxation times are long. There is also dispersion present meaning that the frequency of sound wave depends nonlinearly on wave vector. Non-linearity and dispersion are prerequisites for the presence of solitons which by definition do not dissipate energy. Variations of temperature, volume, area, and thickness and also other mechanical effects are known to accompany nerve pulse propagation. It is also known that the heat density and temperature of the cell membrane increases slightly first and is then reduced. This suggests adiabaticity in average sense. These findings motivate the assumption that nerve pulse actually corresponds to acoustic soliton . Soliton model reproduces correctly the velocity of nerve pulse inside myelin sheaths but it is not clear to me how well the much lower conduction velocity in non-myelin sheathed regions is reproduced. It is not clear how the lower values of the conduction velocity and its proportionality to the axonal radius in non-myelinated regions can be understood. Intuitively it however seems clear that the lower velocity is due to the feedback from the interaction of ions with the region exterior to cell membrane. In the case of myelin sheaths the conduction of nerve pulse is usually believed to take place via saltation : the depolarization induced at Ranvier node is believed to be enough to take the membrane potential below critical value in the next node so that nerve pulse hops between the nodes. Insulation would improve the insulation and make this process possible. The reversible heat transfer process is however known to be present also in the myelinated portions of axon so that there must be a pulse propagating also in these regions . It is not clear how the myelin sheet can increase the velocity in the soliton model but the reduction of the feedback inducing friction suggests itself. Soliton property predicts adiabaticity. Ordinary ionic currents however dissipate so that adiabaticity assumption is questionable in standard physics context. The model does not predict the growth of entropy followed by its reduction. This behavior is consistent with adiabaticity in a time resolution of order millisecond. The estimate for the capacitor energy density during the nerve pulse is considerably smaller than the energy density is many times magnitude smaller than that of the acoustic wave. This might allow to demonstrate that Hodgkin-Huxley model is not a complete description of the situation. Authors notice that the shapes curves representing solitonic energy density and the capacitor energy density as a function of time are essentially identical. Same applies to the experimentally deduced heat change release curve and capacitor energy density for garfish axon. Also heat release and the deviation of the membrane potential from its resting value are in exact phase. These similarities could reflect a control signal responsible for the nerve pulse originating somewhere else, perhaps at microtubuli. This could explain why secondary nerve pulse is not generated immediately after the first one although the temperature is slightly lower after the pulse than before it. This could of course be also due to the exhaustion of the metabolic resources. For background see that chapter Quantum Model of Nerve Pulse of TGD and EEG. References Soliton model . T. Heimburg and A. D. Jackson (2005), On soliton propagation in biomembranes and nerves , PNAS vol. 102, no. 28, p.9790-9795. T. Heimburg and A. D. Jackson (2005), On the action potential as a propagating density pulse and the role of anesthetics , arXiv : physics/0610117 . K. Graesboll (2006), Function of Nerves-Action of Anesthetics , Gamma 143, An elementary Introduction . Physicists challenge notion of electric nerve impulses; say sound more likely . Saltation . Quantum model of nerve pulse II: Basic inputs of TGD based model of nerve pulse The model of nerve pulse whose inputs are summarized below can be motivated by the observed adiabaticity of the nerve pulse and by the strange findings about ionic currents associated with the cell membrane and by the model of Danish researchers for the nerve pulse . The model involves also a fusion of various ideas of earlier models. In particular, Josephson currents and solitons are in a key role in the model but with the necessary flexibility brought in by the hierarchy of Planck constants. The basic inputs of the model are following. The presence of acoustic soliton or density pulse proposed by Danish researchers looks plausible but a a more fundamental quantum control mechanism inducing the acoustic soliton cannot be excluded. Among other things this should explain why acoustic solitons propagate always in the same direction. In particular, one can consider a soliton like excitation (say breather for Sine-Gordon equation) associated with the electronic or ionic Josephson currents running along magnetic flux tubes. The strange effects associated with the ionic currents through the cell membrane suggest quite generally that at least weak ionic currents through normal cell membrane are non-dissipative quantal currents. The adiabaticity of the nerve pulse suggests that also strong ionic currents are quantal. Strong ionic currents generating nerve pulse through axonal membrane are absent in the resting state. The naive explanation is simple: the life time of the magnetic flux tubes connecting the axonal interior to the exterior is short or the flux tubes are altogether absent. The observation that Josephson currents in constant voltage are automatically periodic suggests a less naive explanation allowing the flux tubes to be present all the time. The presence of ionic Josephson currents predicts a small amplitude oscillation of membrane potential for which 1 kHz synchronous oscillation is a natural identification. Josephson oscillation correspond naturally to propagating soliton sequences for Sine-Gordon equation . The dynamics of the simplest modes is equivalent to the rotational motion of gravitational pendulum: the oscillation of membrane potential corresponds to the variation of d/dt propto V. Note that if axon is above the melting temperature, the lipid layer is in gel phase and fluid motion is impossible. The surface density of lipids is dramatically reduced at criticality so that lipid layers behave like fluids . This means that tqc is not possible by the braiding of lipids. Nerve pulse is generated when the magnitude of the negative membrane potential is reduced below the critical value. Generation of the nerve pulse is like a kick to a rotating gravitational pendulum changing the sign of = d/dt so that rotational motion is transformed to oscillatory motion lasting for about the period of rotation. An opposite but slightly stronger kick must reduce the situation to the original one but with a slightly higher value of . These kicks could correspond to voltage pulse between microtubules and inner lipid layer of cell membrane induced by the addition of small positive (negative) charge on lipid layer. This pulse would induce electronic DC Josephson current inducing the kick and thus reducing V. The exchange of scaled variants of W bosons (assignable to W MEs) could mediate the transfer of charge through the cell membrane and reduce the membrane potential below the critical value but one can consider also other mechanisms. The conservative option would be that ordinary ionic currents take care of the rest and Hogkin-Huxley model applies. This was assumed in the earliest model in which soliton sequence for Josephson current was assumed to induce nerve pulse sequence: in the recent model this assumption does not make sense. The findings of Danish researchers do not however support the conservative option . Nerve pulse could be due to dark ionic (possibly supra -) currents with large hbar with a low dissipation rate. Their flow would be made possible by the presence of magnetic flux tubes connecting cell interior and exterior. For background see that chapter Quantum Model of Nerve Pulse of TGD and EEG. References Soliton model . T. Heimburg and A. D. Jackson (2005), On soliton propagation in biomembranes and nerves , PNAS vol. 102, no. 28, p.9790-9795. T. Heimburg and A. D. Jackson (2005), On the action potential as a propagating density pulse and the role of anesthetics , arXiv : physics/0610117 . K. Graesboll (2006), Function of Nerves-Action of Anesthetics , Gamma 143, An elementary Introduction . Physicists challenge notion of electric nerve impulses; say sound more likely . Saltation . Sine-Gordon The chapter DNA as Topological Quantum Computer of Genes and Memes.
标签: wave
