Are developed and emerging agricultural futures markets multifractal? A comparative perspective

Although there are many reports on the empirical evidence of the existence of multifractality in various financial or commodity markets in current literature, few can be found to compare the multifractal properties of emerging and developed economies, especially for agricultural futures markets in those countries (regions). We therefore chose China as the representative of the transition and emerging economies, and USA as the representative of developed ones. We attempt to find the answers to the following questions: (1) Are all those different markets multifractal? (2) What are the dynamical causes for multifractality in those markets (if any)? (3) Are the multifractality strengths in those markets of the transition and emerging economies weaker (or stronger) than those of the developed ones? To answer these questions, Multifractal Detrended Fluctuation Analysis (MF-DFA) are applied to study some of the representative agricultural futures markets in China and USA, namely, wheat, soy meal, soybean and corn. Our results suggest that all the markets of China and USA exhibit multifractal properties except US soybean market, which is much closer to mono-fractal comparing with China’s soybean market. To investigate the sources of multifractality, shuffling and phase randomization procedures are applied to destroy the temporal correlations and non-Gaussian distributions respectively. We found that multifractality can be mainly attributed to the non-Gaussian probability distribution and secondarily to the nonlinear temporal correlation mechanism for all the markets, except US soybean and soy meal, which derives from some other unknown factors. Furthermore, the average of τ(q) are applied to obtain the multifractal spectra of the two markets as a whole. The results show that the width of the multifractal spectrum of US agricultural futures markets is significantly narrower than that of China’s. Based on our findings, we proposed a hypothesis that the strength of multifractality in developed economies may be weaker than that in emerging and transition ones.     

Are cerebral cavernomas truly nonenhancing lesions and thereby distinguishable from arteriovenous malformations?: MRI findings and histopathological correlation

PURPOSE: The aim of this study was to determine whether cerebral cavernomas are truly nonenhancing lesions on magnetic resonance imaging (MRI), whether they can be distinguished from arteriovenous malformations (AVM) on that basis and to evaluate the incidence of their association with developmental venous anomalies (DVA). PATIENTS AND METHODS: Thirty-two patients who underwent neurosurgical operation for a cerebral vascular malformation and had a standard MRI conclusive of cerebral cavernoma were retrospectively evaluated for size of the lesions, contrast enhancement of the lesion and the coexistence of DVA. The contrast uptake of these lesions was investigated, and contrast enhancement was classified as none, moderate or marked. The incidence of an associated DVA was also investigated. The radiological findings were subsequently correlated with neurohistopathological findings. RESULTS: No difference was found between the contrast enhancement of cavernomas and AVMs. Cross tables were calculated for contrast enhancement and size, which demonstrated no statistically significant correlation. Cross tables were calculated for contrast enhancement and histopathological diagnosis, which revealed that both entities presented variable degrees of contrast enhancement and were thereby not distinguishable from each other on the basis of contrast enhancement. We found an association of cavernoma with DVA in 30% of cases. CONCLUSION: Neither a correlation between the absence of contrast enhancement and the histopathological diagnosis of cavernoma nor the size and contrast enhancement was found. We conclude that cavernomas present with variable degrees of contrast enhancement on MRI and, thus, are definitely not distinguishable from AVM on the basis of contrast enhanced MRI. We found an association between cavernomas and DVA in approximately one third of patients.     

Are wave mechanics and matrix mechanics equivalent theories?

The Eckart and Schrödinger proofs of 1926 are often described as having established the equivalence of wave mechanics and matrix mechanics as physical theories. The objective of this paper is to show that these “proofs” establish nothing of the kind. The Eckart-Schrödinger “proofs” have to do only with the formal identity of two different calculi. The question is, do the “proofs” establish the mathematical identity ofC ₁ andC ₂? Two views are possible: (1) Eckart and Schrödinger subsumed wave mechanics (C ₁) and matrix mechanics (C ₂) within a more comprehensive theory — which might be called “the operator calculus” (O). From this alone it does not follow thatC ₁ andC ₂ are formally identical. In general, the identity of two theories can never be established just by the fact that they both follow from the same premise. The other view (2) is thatO is simply a logical transformer which converts any statement ofC ₁ into a corresponding statement ofC ₂ — without adding any theoretical content of its own. That this is so could never beproved by an inductive selection of typical problems within microphysics; yet this is the actual procedure of Eckart and Schrödinger. Strictly speaking, one could consistently doubt thatC ₁ andC ₂ are ultimately identical even after sympathetically entertaining the Eckart-Schrödinger “proofs”. The really convincing argument for the equivalence asphysical theories of wave mechanics and matrix mechanics was provided by Born's statistical interpretation of theψ-function. Because here, in a frankly inductive procedure, Bornforces a physical interpretation onto bothC ₁ andC ₂ which at last makes it a matter of indifference which algorithm one chooses to express his predictions.     

Are the Weyl and coherent state descriptions physically equivalent?

We investigate the consistency of coherent state quantization in regard to physical observations in the non-relativistic (or Galilean) regime. We compare this particular type of quantization of the complex plane with the canonical (Weyl) quantization and examine whether they are or not equivalent in their predictions. As far as only usual dynamical observables (position, momentum, energy, …) are concerned, the quantization through coherent states is proved to be a perfectly valid alternative. We successfully put to the test the validity of CS quantization in the case of data obtained from vibrational spectroscopy.     

Are the Elements Elementary? Nineteenth-Century Chemical and Spectroscopical Answers

We analyze the role and influence of a tradition of research linked to the concept of primary matter in nineteenth-century studies on the nature of the elements.The suggestion of William Prout (1785-1850) in 1816 that the atomic weights of pure chemical elements are whole numbers and multiples of the atomic weight of hydrogen, taken as unity, was met with serious confutations,which in turn prompted several attempts to save Prouts hypothesis.We discuss these attempts in detail and the objections raised against them, for instance by Dmitry Ivanovich Mendeleev (1834-1907). We pay particular attention to the use of spectroscopy as a method for proving the existence of elementary forms of matter inside atoms. Leaders in this field of research were two English scientists, the astrophysicist Norman Lockyer (1836-1920) and the chemist William Crookes (1832- 1919). Both of their approaches involved the idea of primary matter. However, while Crookess approach proved to be incorrect, Lockyers ideas survived for several years and supported the discovery of the electron by J.J.Thomson (1856-1940).     

Long memory and volatility clustering: Is the empirical evidence consistent across stock markets?

Long memory and volatility clustering are two stylized facts frequently related to financial markets. Traditionally, these phenomena have been studied based on conditionally heteroscedastic models like ARCH, GARCH, IGARCH and FIGARCH, inter alia. One advantage of these models is their ability to capture nonlinear dynamics. Another interesting manner to study the volatility phenomenon is by using measures based on the concept of entropy. In this paper we investigate the long memory and volatility clustering for the SP 500, NASDAQ 100 and Stoxx 50 indexes in order to compare the US and European Markets. Additionally, we compare the results from conditionally heteroscedastic models with those from the entropy measures. In the latter, we examine Shannon entropy, Renyi entropy and Tsallis entropy. The results corroborate the previous evidence of nonlinear dynamics in the time series considered.     

Are particle and photon tunneling and filling in barriers local or non-local phenomena?

It is shown that particle and photon tunneling exhibits a non-local behaviour. This is also true for the wave filling in a semiclosed barrier with a dead stopper. In this connection, we discuss and define for the first time the penetration time of such a barrier in the wave-packet approach.     

Quark and Gluon Orbital Angular Momentum: Where Are We?

The orbital angular momentum of quarks and gluons contributes significantly to the proton spin budget and attracted a lot of attention in the recent years, both theoretically and experimentally. We summarize the various definitions of parton orbital angular momentum together with their relations with parton distributions functions. In particular, we highlight current theoretical puzzles and give some prospects.     

Are crossings of energy levels and charge exchange really quantum phenomena?

In this Letter a recently proposed gravity dual of noncommutative Yang-Mills theory is derived from the relations between closed string moduli and open string moduli recently suggested by Seiberg and Witten. The only new input one needs is a simple form of the running string tension as a function of energy. This derivation provides convincing evidence that string theory integrates with the holographical principle and demonstrates a direct link between noncommutative Yang-Mills theory and holography.     

How fast do stock prices adjust to market efficiency? Evidence from a detrended fluctuation analysis

In this paper we analyse price fluctuations with the aim of measuring how long the market takes to adjust prices to weak-form efficiency, i.e., how long it takes for prices to adjust to a fractional Brownian motion with a Hurst exponent of 0.5. The Hurst exponent is estimated for different time horizons using detrended fluctuation analysis–a method suitable for non-stationary series with trends–in order to identify at which time scale the Hurst exponent is consistent with the efficient market hypothesis. Using high-frequency share price, exchange rate and stock data, we show how price dynamics exhibited important deviations from efficiency for time periods of up to 15 min; thereafter, price dynamics was consistent with a geometric Brownian motion. The intraday behaviour of the series also indicated that price dynamics at trade opening and close was hardly consistent with efficiency, which would enable investors to exploit price deviations from fundamental values. This result is consistent with intraday volume, volatility and transaction time duration patterns.     

Is Bitcoin’s Carbon Footprint Persistent? Multifractal Evidence and Policy Implications

The Bitcoin mining process is energy intensive, which can hamper the much-desired ecological balance. Given that the persistence of high levels of energy consumption of Bitcoin could have permanent policy implications, we examine the presence of long memory in the daily data of the Bitcoin Energy Consumption Index (BECI) (BECI upper bound, BECI lower bound, and BECI average) covering the period 25 February 2017 to 25 January 2022. Employing fractionally integrated GARCH (FIGARCH) and multifractal detrended fluctuation analysis (MFDFA) models to estimate the order of fractional integrating parameter and compute the Hurst exponent, which measures long memory, this study shows that distant series observations are strongly autocorrelated and long memory exists in most cases, although mean-reversion is observed at the first difference of the data series. Such evidence for the profound presence of long memory suggests the suitability of applying permanent policies regarding the use of alternate energy for mining; otherwise, transitory policy would quickly become obsolete. We also suggest the replacement of ‘proof-of-work’ with ‘proof-of-space’ or ‘proof-of-stake’, although with a trade-off (possible security breach) to reduce the carbon footprint, the implementation of direct tax on mining volume, or the mandatory use of carbon credits to restrict the environmental damage.     

Are Guessing,Source Coding and Tasks Partitioning Birds of A Feather?

This paper establishes a close relationship among the four information theoretic problems, namely Campbell source coding, Arikan guessing, Huleihel et al. memoryless guessing and Bunte and Lapidoth tasks’ partitioning problems in the IID-lossless case. We first show that the aforementioned problems are mathematically related via a general moment minimization problem whose optimum solution is given in terms of Renyi entropy. We then propose a general framework for the mismatched version of these problems and establish all the asymptotic results using this framework. The unified framework further enables us to study a variant of Bunte–Lapidoth’s tasks partitioning problem which is practically more appealing. In addition, this variant turns out to be a generalization of Arıkan’s guessing problem. Finally, with the help of this general framework, we establish an equivalence among all these problems, in the sense that, knowing an asymptotically optimal solution in one problem helps us find the same in all other problems.