Are There Dynamical Laws?

The nature of a physical law is examined, and it is suggested that there may not be any fundamental dynamical laws. This explains the intrinsic indeterminism of quantum theory. The probabilities for transition from a given initial state to a final state then depends on the quantum geometry that is determined by symmetries, which may exist as relations between states in the absence of dynamical laws. This enables the experimentally well-confirmed quantum probabilities to be derived from the geometry of Hilbert space and gives rise to effective probabilistic laws. An arrow of time which is consistent with the one given by the second law of thermodynamics, regarded as an effective law, is obtained. Symmetries are used as the basis for a new proposed paradigm of physics. This naturally gives rise to the gravitational and gauge fields from the symmetry group of the standard model and a general procedure for obtaining interactions from any symmetry group.     

Beam-Plasma Emission near the Plasma Frequency

This paper presents detailed spectra for electromagnetic emission from a strong relativistic beam-plasma instability. Some emission appears early in the beam voltage pulse, apparently from reflexing. This subsides as beam propagation improves, and emission moves to high frequencies. This is compatible with a collective emission process from electrostatic waves built up in the chamber by reflection from the walls. Noise levels suggest about 100 emitting sites switching on and off randomly. The emitters comprise about 1 percent of the plasma volume and survive a time comparable to the lifetime of solitons subject to ion damping.     

Total fluence influence on the detected magnitude of neutron burst using proportional detectors

The measurement of very short neutron bursts, when individual neutrons cannot be counted in the usual manner, is possible with proportional detectors (such as ³He) taking the integration of the total electric charge due to many overlapped interactions, as the measure of the amount of the neutron signal. This method requires a correction related to the total amount of neutrons that interacted with the detector. This correction originates in the well-known build-up of positive electric charge too slow to be dislodged from the detection volume during the neutron burst. This causes self-shielding of the applied electric field with the ensuing reduction of the charge multiplication process in the gas, described in the literature.Short neutron bursts from a plasma focus device and a conventional isotopic neutron source were employed in the experimental phase and the known theory was applied in the analysis, which justifies assigning the observed effects to the space-charge shielding of the externally applied electric field.This work introduces a correction to the neutron yield derived from the registered electric charge, through a model of collected charge reduction as a function of total neutrons measured.     

On particles tunneling from the Taub-NUT-AdS black hole

This paper discusses tunneling of scalar particles and Dirac particles from the Taub-NUT-AdS black hole by the Hamilton--Jacobi equation, initially used by Angheben et al, and the Dirac equation, recently proposed by Kerner and Mann. This is performed in the dragging coordinate frame so as to avoid the ergosphere dragging effect. A general form is obtained for the temperature of scalar and Dirac particles tunneling from the Taub-NUT-Ads black hole, which is commensurate with other methods as expected.     

电声学科的跨越特点和应用进展

本文综述了电声学科由于具有跨越科学与艺术两大领域和跨越多种学科的性质所带来的研究和应用特点,提出了几项近些年值得重视的应用领域和可能发展趋势,希望引起同仁讨论。鉴于我国在其中有些方面有突出成绩,本文将特别加以介绍,也希望得到大家的关心。本文还有一个附带的期望：促进非电声学科的声学工作者了解和关心电声学科的核心。     

同步辐射X射线荧光对双柏恐龙化石的分析

首次使用同步辐射X射线荧光法（SXRF）测试了双柏县安龙堡的恐龙化石,在其截面上原位获得了Ca,Fe,Mn,Cu,Zn,As,Y和Sr等八种元素的分布图。测试结果表明,各种元素在化石中的分布是非均匀的,与一般的矿物岩石元素的分布不同。元素分布图表明,在双柏恐龙化石中未检测到As元素,与四川自贡恐龙由于As元素高的非正常死亡相比,双柏恐龙属正常死亡情形。在分布图中容易看出,化石中的Fe和Mn元素是共生的;Sr和Y两种元素也是共生的,显示化石在成岩过程中,所含Fe,Mn,Sr,Y的化合物胶体均为带异种电荷的颗粒,据此可推知当时这些元素所属化合物的可能形式。同步X射线荧光显微探测法研究恐龙化石元素分布具有原位、快速、准确、直观等优势,它可以将共生元素分离开来,这是XRD和等离子光谱等测试手段不能实现的。恐龙化石微量元素的分布,揭示了化石微区矿物结构的相关信息,这对于挖掘化石蕴涵的古地质特征,恢复古地理、古地质研究的潜力具有重要意义。     

Computational modelling of thermophysical processes in the light metals industry

This survey focuses on the aluminium industry, mostly on process aspects as opposed to metallurgical aspects. It covers recent work on process models involving fluid flow and heat transfer, and extends to all important categories of processes encountered in the primary aluminium industry, from raw materials and reduction to cast shop and recycling. This includes a wide variety of processes from precipitators, calciners, rotary kilns, baking furnaces, reduction cells, casting and mixing furnaces to recycling furnaces and metal filtration. A review is carried out on the modelling work, the applications, and the needs expressed not only in analysis and design but also in process control, optimization and supervision, as well as operator training. A summary is given of the problems perceived, mainly in the field of model parameters and model validation. Indications on future trends are also given. Conclusions are drawn from the survey of this fast-expanding body of knowledge that suggests tough challenges as well as unprecedented opportunities. Suggestions are made as to how some of those challenges could be met.     

Linear response theory for thermodynamic properties

A fluctuation-dissipation theorem, connecting all thermodynamic response functions to equilibrium fluctuations in the microcanonical ensemble, is derived from classical mechanics. This particular problem is not included in the usual linear response scheme, since the relevant perturbations cannot be stated as additional terms in the Hamiltonian. In experiments where the only control parameter is the heat flow, dissipation is present in terms of an entropy flow from the system to the surroundings. As an example, the full frequency-dependent thermodynamic response matrix is extracted from simulations of a supercooled binary Lennard-Jones fluid. This fluid shows rather high relaxation strength of all response functions, except of the adiabatic compressibility. The low frequency limit of all thermodynamic susceptibilities increases as temperature is decreased along an isocore.     

High-efficiency, single-stage 7-kHz high-average-power ultrafast laser system

We demonstrate a simple and practical single-stage ultrafast laser amplifier system that operates at a repetition frequency from 1 to 10 kHz, with millijoule pulse energy and as much as 13 W of average power. The repetition rate can be adjusted continuously from 1 to 10 kHz by new all-solid-state pump laser technology. This is to our knowledge the highest average power ever obtained from a single-stage ultrafast laser amplifier system. This laser will significantly increase the average power and the repetition rate that is easily accessible for high-field experiments such as coherent x-ray generation or for laser-synchrotron studies.     

Equilibrium-based iterative tomography technique for soft X-ray instellarators

A method to deduce local values of plasma emissivity from chord measurements has been developed and tested using data from a 30 detector soft X-ray array in the Wendelstein 7A stellarator. This technique, based on the calculated distribution of toroidal magnetic flux as the initial guess for the plasma emissivity, uses an iterative scheme to algebraically determine the distribution of the detector signals, and solves some drawbacks of the currently available tomography techniques. This method is especially suited for stellarator devices in which plasma cross sections are markedly noncircular and change as a function of the toroidal angle     

Accurate state and parameter estimation in nonlinear systems with sparse observations

Transferring information from observations to models of complex systems may meet impediments when the number of observations at any observation time is not sufficient. This is especially so when chaotic behavior is expressed. We show how to use time-delay embedding, familiar from nonlinear dynamics, to provide the information required to obtain accurate state and parameter estimates. Good estimates of parameters and unobserved states are necessary for good predictions of the future state of a model system. This method may be critical in allowing the understanding of prediction in complex systems as varied as nervous systems and weather prediction where insufficient measurements are typical.     

From Faraday rotation to “Faraday oscillation”: Coherence effect between real and virtual excitons

This work provides the microscopic mechanisms responsible for circular birefringence changed into linear birefringence when the polarization of the excitons present in a semiconductor sample goes from circular to linear. This change shows up as Faraday rotation turning to “Faraday oscillation”: The probe polarization plane oscillates instead of rotates while the polarization goes from linear to elliptical and linear again. This oscillation, which reduces to zero when the probe polarization is parallel or perpendicular to the exciton polarization, comes from a non trivial coherence effect between real excitons present in the sample and virtual excitons coupled to unabsorbed photons. While Faraday rotation mainly follows from one single carrier exchange between composite excitons in the absence of Coulomb interaction, Faraday oscillation requires two Coulomb interactions plus a double carrier exchange, the virtual excitons coupled to the unabsorbed “in” and “out” photons being made with different electrons and holes, as nicely revealed by Shiva diagrams which visualize the many-body physics taking place in composite-exciton systems.     

金属冲击温度测量中金属/窗口界面表观光谱辐亮度的再研究

 在冲击压缩下，理想接触的金属/窗口界面温度历史是时间无关的，因而一般认为界面的表观光谱辐亮度也是时间无关的。研究表明：（1）在冲击压缩下，将伴随金属对光的吸收系数减小和光学厚度增大。因此，在考虑辐射输运效应后，理想接触的金属/窗口界面处的表现光谱辐亮度是时间相关的。非常明显的时间相关过程自冲击波到达界面后持续约10 ns。（2）若把存在空间温度梯度的金属界面辐射看作是透光厚度内平均温度的等效辐射效应，其结果与辐射输运效应的计算结果是很相近的。     

Ambiguities in the up-quark mass

It has long been known that no physical singularity is encountered as up-quark mass is adjusted from small positive to negative values as long as all other quarks remain massive. This is tied to an additive ambiguity in the definition of the quark mass. This calls into question the acceptability of attempts to solve the strong CP problem via a vanishing mass for the lightest quark.     

The Large Hadron Collider: A Marvel of Technology,edited by Lyndon Evans

Machine learning algorithms learn a desired input-output relation from examples in order to interpret new inputs. This is important for tasks such as image and speech recognition or strategy optimisation, with growing applications in the IT industry. In the last couple of years, researchers investigated if quantum computing can help to improve classical machine learning algorithms. Ideas range from running computationally costly algorithms or their subroutines efficiently on a quantum computer to the translation of stochastic methods into the language of quantum theory. This contribution gives a systematic overview of the emerging field of quantum machine learning. It presents the approaches as well as technical details in an accessible way, and discusses the potential of a future theory of quantum learning.     

A novel approach to the kinetic theory and hydrodynamic turbulence. II

A novel approach to the kinetic theory of gases is suggested through certain correlation functions known as product densities. This approach is shown to be very useful in explaining transitions from gaseous to liquid state as well as laminar to turbulent flows in gas dynamics. For large deviations from the equilibrium configuration, it is shown that the system obeys a set of generalised Navier-Stokes equation where some stochastic features are present.     

Interpretive nonlinear viscoelasticity: Dynamic properties of nylon 6 fibers

A method is developed to analyze the distortion of stress waves resulting. from sinusoidal strains. This distortion can result from two effects: (a) changes in modulus as function of strain (or angle θ) during the cycle, and (b) changes in mechanical loss as function of strain (or angle θ) during the cycle. The determination of the relative contribution of these two effects requires the knowledge of specimen modulus and loss at each instant of the experiment. This can be achieved by superimposing a high frequency small amplitude wave on the high amplitude low frequency wave. This technique is used in the analysis of dynamic responses of nylon 6 fibers. The results show that the energy loss in extension is different from that in contraction. This indicates that, in addition to strain dependence of modulus and loss, the analysis of the hysteresis curve must account also for the reversible strain induced structural change. An analytical procedure is presented to treat the data, and the effects of strain amplitude and temperature on the type of strain-induced structural changes are discussed.     

Envelope-onset asynchrony as a cue to voicing in initial english consonants

An acoustic cue for voicing is proposed based on the underlying processes associated with the production of the voicing contrast. This cue is based on the time asynchrony between the onsets of two amplitude-envelope signals derived from different bands of speech (i.e., envelopes derived from a lowpass-filtered band at 350 Hz and from a highpass-filtered band at 3000 Hz). Acoustic measurements made on the envelope signals of a set of 16 initial consonants represented through multiple tokens of C1VC2 syllables indicate that the onset-timing difference between the low- and high-frequency envelopes (Envelope-Onset Asynchrony or EOA) provides a reliable and robust cue for distinguishing voiced from voiceless consonants. This cue, which is simply derived in real-time, has applications to the design of sensory aids for persons with profound hearing impairments (e.g., as a supplement to lipreading), as well as to automatic speech recognition.     

A new spin test for the equivalence principle

The existing impressive tests for the strong equivalence principle are reviewed and their classical nature is emphasized. The possibility is raised here that intrinsic quantum spins may behave differently from orbital angular momentum in gravitational fields. The techniques developed to measure the electric dipole moment of the neutron are shown to offer hopes of testing this hypothesis. Einstein's theory predicts a null result for this experiment. This would constitute the first quantum test for the strong equivalence principle. Deviation from a null result would invalidate Einstein's theory of gravitation, as well as indicate the failure of the discrete symmetries (P, T) in gravitation.This essay received an honorable mention (1976) from the Gravity Research Foundation-Ed.     

Study of non-exponential electron capture by the main electron trap in GaAs0.62P0.38

In deep level transient spectroscopy (DLTS) exponentiality of level population changes in thermal emission as well as in capture processes is assumed. This is however, contrary to what is often observed in experiment. In this paper a model for interpretation of DLTS data in the case of non-exponential capture of electrons is proposed. It is assumed that the height of the capture of carrier changes locally according to the Gaussian distribution This model is applied to the case of deep electron trap with thermal activation energy equal to ΔE_B = 0.39 eV, observed in VPE GaAs_0.62P_0.38. Te. This model provides a capture barrier as well as a capture cross-section which are different from the ones predicted by the exponential transient model i.e., the ones derived from the slope of capacitance changes due to the filling pulse versus pulse duration at very short times.