Kolmogorov turbulence in a random-force-driven Burgers equation: anomalous scaling and probability density functions

High-resolution numerical experiments, described in this work, show that velocity fluctuations governed by the one-dimensional Burgers equation driven by a white-in-time random noise with the spectrum $\overline{|f(k)|^2}\propto k^{-1}$ exhibit a biscaling behavior: All moments of velocity differences $S_{n\le 3}(r)=\overline{|u(x+r)-u(x)|^n}\equiv\overline{|\Delta u|^n}\propto r^{n/3}$, while $S_{n>3}\propto r^{\zeta_n}$ with $\zeta_n\approx 1$ for real $n>0$ (Chekhlov and Yakhot, Phys. Rev. E {\bf 51}, R2739, 1995). The probability density function, which is dominated by coherent shocks in the interval $\Delta u<0$, is ${\cal P}(\Delta u,r)\propto (\Delta u)^{-q}$ with $q\approx 4$.Comment: 12 pages, psfig macro, 4 figs in Postscript, accepted to Phys. Rev. E as a Brief Communicatio

1,4,10,13-Tetra­oxa-7,16-diazo­niacyclo­octadecane bis­[tetra­chloridoaurate(III)] dihydrate

The asymmetric unit of the title compound, (C12H28N2O4)[AuCl4]2·2H2O, contains one half-cation, one anion and one water mol­ecule; the cation is centrosymmetric. The Au ion has a square-planar coordination. In the crystal structure, intra­molecular N—H⋯O and O—H⋯O, and inter­molecular N—H⋯O, O—H⋯Cl and N—H⋯Cl hydrogen bonds link the ions and water mol­ecules, forming a supra­molecular structure

On the maximum drawdown during speculative bubbles

A taxonomy of large financial crashes proposed in the literature locates the burst of speculative bubbles due to endogenous causes in the framework of extreme stock market crashes, defined as falls of market prices that are outlier with respect to the bulk of drawdown price movement distribution. This paper goes on deeper in the analysis providing a further characterization of the rising part of such selected bubbles through the examination of drawdown and maximum drawdown movement of indices prices. The analysis of drawdown duration is also performed and it is the core of the risk measure estimated here.Comment: 15 pages, 7 figure

Direct Numerical Simulation Tests of Eddy Viscosity in Two Dimensions

Two-parametric eddy viscosity (TPEV) and other spectral characteristics of two-dimensional (2D) turbulence in the energy transfer sub-range are calculated from direct numerical simulation (DNS) with 512$^2$ resolution. The DNS-based TPEV is compared with those calculated from the test field model (TFM) and from the renormalization group (RG) theory. Very good agreement between all three results is observed.Comment: 9 pages (RevTeX) and 5 figures, published in Phys. Fluids 6, 2548 (1994

On commutator fully transitive Abelian groups

Abstract There are two rather natural questions which arise in connection with the endomorphism ring of an Abelian group: when is the ring generated by its commutators, and when is the ring additively generated by its commutators? The current work explores these two problems for arbitrary Abelian groups. This leads in a standard way to consideration of two improved versions of Kaplansky's notion of full transitivity, which we call commutator full transitivity and strongly commutator full transitivity. We establish, inter alia, that these notions are strictly stronger than the classical concept of full transitivity, but there are nonetheless many parallels between these things.</jats:p

Turbulence without pressure

We develop exact field theoretic methods to treat turbulence when the effect of pressure is negligible. We find explicit forms of certain probability distributions, demonstrate that the breakdown of Galilean invariance is responsible for intermittency and establish the operator product expansion. We also indicate how the effects of pressure can be turned on perturbatively.Comment: 12 page

Weakly fully and characteristically inert socle-regular Abelian p-groups

In regard to two recent publications in the Mediterranean J. Math. (2021) and Forum Math. (2021) related to fully and characteristically inert socleregularity, respectively, we define and study the so-called weakly characteristically inert socle-regular groups. In that aspect, as a culmination of the investigations of this sort, some more global results are obtained and, moreover, some new concrete results concerning the weakly fully inert socle-regular groups, defined as in the firstly mentioned above paper, are also established. In particular, we prove that all torsion-complete groups are characteristically inert socle-regular, which encompasses an achievement from the secondly mentioned paper and completely settles the problem posed there about this class of groups

Solution to the Uniformly Fully Inert Subgroups Problem for Abelian Groups

A famous conjecture attributed to Dardano-Dikranjan-Rinauro-Salce states that any uniformly fully inert subgroup of a given group is commensurable with a fully invariant subgroup (see, respectively, [5] and [6]). In this short note, we completely settle this problem in the affirmative for an arbitrary Abelian group.Comment: We give a new very short proof of the crucial Proposition 2.2 and also provide more details in the proof of Proposition 2.