The birth and death of a universe

This letter is meant to be a brief survey of several recent publications providing a simple, sequential explanation of dark energy, inflation, and dark matter. These paragraphs lead to an intuitive and qualitative picture of the why and the how of the Big Bang, and thence to a possible understanding of the birth and death of a universe.     

The direction of time

The meaning of the phrase “the direction of time” and the physical problems involved are considered. These problems are discussed and plausibility arguments are given to show that all clocks run in the same direction (almost always), that the most probable development of the Universe during the early stages of the expansion would result in the introduction of some internal organization, and that the expansion of the Universe and the increase in entropy define time directions that have the same sense. The question of what properties of the laws governing the Universe lead to these results is studied.     

时间的沙漏

时间是什么？它是无限的还是轮回的？是没有开始的还是起源于一次大爆炸？是一维的还是半维的？是实数还是虚数？该取实数值还是整数值？是参数还是变量？所有这些关于时间的模棱两可的认识都表明物理学需要一个角色普适的时间．     

The arrow of time

Dispersive Fourier transform spectroscopy (DFTS) is a technique for determining the optical constants of solids, liquids and gases from direct measurements of both the amplitude and phase of either their reyection or transmission coeficients. Measurements are usually made at normal incidence with the specimen in one arm of a Michelson interferometer. The technique has been widely used for measurements in the far-infrared region of the spectrum, where the phase measurement is comparatively straightforward. Recent developments have established the feasibility of extending the spectral range to the visible and ultraviolet. In this article the principles of DFTS are briefly reviewed, and a selection of results presented to illustrate the scope and potential of the technique.     

The birth of scientific thought at the Aegean shores

The origin of our present scientific thought in the 6^th Century at the Aegean Shores is described. The etymological explanation of the word “ion” is given. Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15–21, 2002.     

The logic of time reversal

Active time reversal in the sense of object reversal and passive time reversal in the sense of a frame reversal of time are discussed separately and then together so as to bring out their dual nature. An understanding of that duality makes it unavoidable to contrast symmetry properties of matter with symmetry properties to be assigned to antimatter. Only frame reversal of time can see all conceivable active time reversals relevant to physical objects. Only frame reversal of time can be used for a meaningful extension of the Neumann principle to the time domain.     

The analysis of time: Is the relativistic time unique?

Time is analyzed by considering the actual setup of clock system within the four-dimensional framework. We find that both relativistic time and universal time can be embedded in such a symmetry framework. Although Poincaré and Einstein both understood the meaning of Lorentz's local time in terms of sending light signals to calibrate clocks, they differed on a basic point: Einstein believed local time to be the necessary and unique time, while Poincaré admitted flexibility in the definitions of time and regarded local time as only a convention. The results of our analysis shed light on Poincaré's original idea concerning conventions of time and provide the conceptual basis for the formulation of a new four-dimensional symmetry with a universal time. We demonstrate that the one-way speeds of light measured by stable atomic clocks in rockets may not be isotropic, in contrast to the two-way speeds of light. Furthermore, atomic clocks can be used to set up a clock system which reads a universal (but not absolute) time.I dedicate this paper to the memory of my beloved father Hsu Mau-Yuen (1903–1977), whose understanding helped me to choose to work on physical problems. Part of the research was accomplished while I held an NRC Senior Resident Research Associateship.     

激光50华诞

2010年是激光诞生50周年.文章回忆了激光发明的历史沿革,简要讨论了受激光发射的物理模型、激光的特性,详细回顾了激光发明后50年间激光器件、技术、应用和产业的发展大事记,介绍了对激光和光电子学作出重大贡献的先驱和科学家,并对一些相关学科和重要应用做了概述.     

激光50华诞

2010年是激光诞生50周年.文章回忆了激光发明的历史沿革,简要讨论了受激光发射的物理模型、激光的特性,详细回顾了激光发明后50年间激光器件、技术、应用和产业的发展大事记,介绍了对激光和光电子学作出重大贡献的先驱和科学家,并对一些相关学科和重要应用做了概述.     

The universe: A birth far from equilibrium?

The scientific world is, as I have often repeated, a shadow world, shadowing a world familiar to our consciousness. Just how much do we expect it to shadow? We do not expect it to shadow all that is in our mind, emotions, memory, etc. In the main we expect it to shadow impressions which can be traced to external sense organs. But time makes a dual entry and thus forms an intermediate link between the internal and the external. This is shadowed partially by the scientific world of primary physics (which excludes time's arrow), but fully when we enlarge the scheme to include entropy. Therefore by the momentous departure in the nineteenth century the scientific world is not confined to a static extension around which the mind may spin a romance of activity and evolution; it shadows that dynamic quality of the familiar world which cannot be parted from it without disaster to its significance.—Arthur Eddington,The Nature of the Physical World.     

The spectral property of time delay

This paper discusses the spectral property of time delay. If one considers the scattering by a potential v, then the spectral property is the statement that the trace of the time-delay operator is proportional to the change in state density produced by the interaction v. We give a new and elementary proof of this result. As a consequence it is shown that Levinson's theorem is implied by the spectral property.     

测量时间的热力学成本

精确测量时间之能力已对社会产生了巨大影响,从海洋航行计时器(在十八世纪推进航海),到星载原子钟(今天全球定位系统(GPS)之基础设备)。但是,物理学对我们测量时间的能力有什么基本的限制呢？在一篇新论文中,来自西班牙巴塞罗那Autonomous 大学的Paul Erker 和他的同事认为,在这样的限制中热力学起关键作用。考虑一个简单的量子钟模型,他们在准确性和分辨率两个特性之间建立了定量关系,并借助于模型钟的热耗散和熵增,计算了运行模型钟的“热力学成本”。时间无情地流逝,从过去流向未来,就我们的感知而言,热力学占据核心地位。因此,这些结果将我们测量时间的能力与时间流逝本身联系起来。     

The time fractional diffusion-wave equation

The time fractional diffusion-wave equation is obtained from the classical diffusion or wave equation by replacing the first- or second-order time derivative by a fractional derivative of order 2β with 0<β≤1/2 or 1/2<β≤1, respectively. Using the method of the Laplace transform, it is shown that the fundamental solutions of the basic Cauchy and signalling problems can be expressed in terms of an auxiliary function M (z; β), where z is the similarity variable. Such function, which reduces to the well-known Gaussian function for β=1/2 (ordinary diffusion), is proved to be an entire function of Wright type.