Amorphous solids exhibit quasi-universal low-temperature anomalies whose origin has been ascribed to localized tunneling defects. Using an advanced Monte Carlo procedure, we create {\it in silico} glasses spanning from hyperquenched ultrastable glasses. a multidimensional path-finding protocol, locate defects with energy splittings smaller than $k_{B}T_Q$, $T_Q$ the temperature below which quantum effects are relevant ($T_Q \approx 1 \,$K most experiments). We find that as stability of glass...

Structural defects control the kinetic, thermodynamic and mechanical properties of glasses. For instance, rare quantum tunneling two-level systems (TLS) govern physics glasses at very low temperature. Due to their extremely density, it is hard directly identify them in computer simulations. We introduce a machine learning approach efficiently explore potential energy landscape glass models desired classes defects. focus particular on TLS we design an algorithm that able rapidly predict...

Abstract The frequency scaling exponent of low-frequency excitations in microscopically small glasses, which do not allow for the existence waves (phonons), has been focus recent literature. density states g ( ω ) these modes obeys an s scaling, where , ranging between 2 and 5, depends on quenching protocol. orgin findings remains controversal. Here we show, using heterogeneous-elasticity theory, that a marginally-stable glass sample follows Debye-like = 2), associated (type-I) are...

The quantization of vortex lines in superfluids requires the introduction their density $\mathcal{L}(\mathbit{r},t)$ description quantum turbulence. space homogeneous balance equation for $\mathcal{L}(t)$, proposed by Vinen on basis dimensional and physical considerations, allows a number competing forms production term $\mathcal{P}$. Attempts to choose correct one time-dependent experiments ended inconclusively. To overcome this difficulty we announce here an approach that employs...

Experimental and simulational studies of the dynamics vortex reconnections in quantum fluids showed that distance $d$ between reconnecting vortices is close to a universal time dependence $d=D[\ensuremath{\kappa}|{t}_{0}\ensuremath{-}t|{]}^{\ensuremath{\alpha}}$ with $\ensuremath{\alpha}$ fluctuating around $1/2$ $\ensuremath{\kappa}=h/m$ circulation. Dimensional analysis, based on assumption circulation only relevant parameter problem, predicts $\ensuremath{\alpha}=1/2$. The theoretical...

The statistics of velocity fluctuations in coflowing superfluid ${}^{4}$He are studied by direct numerical simulations. highly non-Gaussian, generally more than classical turbulence, with the maximal non-Gaussianity occurring when super and normal fluid densities comparable.

Three-dimensional anisotropic turbulence in classical fluids tends towards isotropy and homogeneity with decreasing scales, allowing --eventually-- the abstract model of "isotropic homogeneous turbulence" to be relevant. We show here that opposite is true for superfluid $^4$He 3-dimensional counterflow channel geometry. This flow becomes less isotropic upon becoming eventually quasi 2-dimensional. The physical reason this unusual phenomenon elucidated supported by theory simulations.

The low-temperature quasi-universal behavior of amorphous solids has been attributed to the existence spatially localized tunneling defects found in low-energy regions potential energy landscape. Computational models glasses can be studied elucidate microscopic nature these defects. Recent simulation work demonstrated means generating stable glassy configurations for that mimic metallic using swap Monte Carlo algorithm. Building on studies, we present an extensive exploration metabasins...

In mechanically driven superfluid turbulence, the mean velocities of normal- and components are known to coincide: ${\mathbit{U}}_{\text{n}}={\mathbit{U}}_{\text{s}}$. Numerous laboratory, numerical, analytical studies showed that under these conditions, mutual friction between velocity also couples their fluctuations: ${\mathbit{u}}_{\text{n}}^{\ensuremath{'}}(\mathbit{r},t)\ensuremath{\approx}{\mathbit{u}}_{\text{s}}^{\ensuremath{'}}(\mathbit{r},t)$, almost at all scales. We show this is...

Tunneling two-level systems (TLSs) dominate the physics of glasses at low temperatures. Yet TLSs are extremely rare, and it is thus difficult to directly observe them in silico. Developing simple structural predictors, which can provide markers for determining if a TLS present given glass region, crucial more efficient search. It has been speculated that vibrational quasilocalized modes (QLMs) closely related TLSs, one extract information about from QLMs. In this work we address possibility....

Below the phase transition temperature $Tc \simeq 10^{-3}$K He-3B has a mixture of normal and superfluid components. Turbulence in this material is carried predominantly by component. We explore statistical properties quantum turbulence, stressing differences from better known classical counterpart. To aim we study time-honored Hall-Vinen-Bekarevich-Khalatnikov coarse-grained equations turbulence. combine pseudo-spectral direct numerical simulations with analytic considerations based on an...

In classical turbulence the kinematic viscosity $\ensuremath{\nu}$ is involved in two phenomena. The first energy dissipation and second mechanical momentum flux toward wall. superfluid mechanism of different, it determined by an effective which was introduced Vinen denoted as ${\ensuremath{\nu}}^{\ensuremath{'}}$. this paper we show that transfer to wall caused presence a quantum vortex tangle, giving rise another ``momentum'' denote ${\ensuremath{\nu}}_{\text{m}}(T)$. temperature...

We report on a combined theoretical and numerical study of counterflow turbulence in superfluid $^{4}$He wide range parameters. The energy spectra the velocity fluctuations both normal-fluid components are strongly anisotropic. angular dependence correlation between two plays key role. A selective dissipation intensifies as scales decrease, with streamwise becoming dominant. Most flow is concentrated wavevector plane which orthogonal to direction counterflow. phenomenon becomes more...

This is a Reply to Nemirovskii's Comment [Phys. Rev. B 94, 146501 (2016)] on Khomenko et al. 91, 180504 (2015)] in which new form of the production term Vinen's equation for evolution vortex-line density $\mathcal{L}$ thermal counterflow superfluid $^{4}\mathrm{He}$ channel was suggested. To further substantiate suggested questioned Comment, we present physical explanation improvement closure comparison proposed by Vinen. We also discuss flux term, agrees well with numerical results without...

Abstract The previously published calculations of molecular vibrations in trichlorophosphazoperchloroalkyl molecules, Cl3P = NR cl, /1/made it possible to associate the IR absorption range 1300-1500cm−1 and 900-1000cm−1 with asymmetrical symmetrical PNC group ( aPNC sPNC) difference Δ - sPNC value angle.

Describing superfluid turbulence at intermediate scales between the intervortex distance and macroscale requires an acceptable equation of motion for density quantized vortex lines $\mathcal{L}$. The closure such inhomogeneous flows additional inputs besides $\mathcal{L}$ normal velocity fields. In this paper, we offer a minimal using one anisotropy parameter ${I}_{l0}$. Using example counterflow turbulence, derive two coupled equations line ${I}_{l0}$ with input various assumptions...

Abstract Although the vibrational spectra of triphosphonitrilic chloride, (PNCl2)3 (1), have been studied by numerous investigators1–8, there is no general agreement about frequency completely inactive A2 ring vibration. Besides, assignment some overtones and combination bands doubtful.

Abstract Recently the IR spectra of trichlorophosphazoperhaloalkyls, CI3P[dbnd]NRHal, were studied,1and position P[dbnd]N frequencies in range 1300-1500cm−1 and those C-N within 900-1000cm−1 found to depend a great extent upon nature groups attached nitrogen atom.

Structural defects control the kinetic, thermodynamic and mechanical properties of glasses. For instance, rare quantum tunneling two-level systems (TLS) govern physics glasses at very low temperature. Because their extremely density, it is hard to directly identify them in computer simulations. We introduce a machine learning approach efficiently explore potential energy landscape glass models desired classes defects. focus particular on TLS we design an algorithm that able rapidly predict...

Using heterogeneous-elasticity theory (HET) and a generalisation of HET (GHET), obtained by applying newly developed procedure for obtaining the continuum limit glass's Hessian, we investigate nature vibrational excitations, which are present in small systems, do not allow low-frequency phonons. We identify two types such non-phononic excitations. In marginally stable can be prepared quenching from rather high parental temperature, regime is dominated random-matrix wavefunctions (type-I)...

The low-temperature quasi-universal behavior of amorphous solids has been attributed to the existence spatially-localized tunneling defects found in low-energy regions potential energy landscape. Computational models glasses can be studied elucidate microscopic nature these defects. Recent simulation work demonstrated means generating stable glassy configurations for that mimic metallic using swap Monte Carlo algorithm. Building on studies, we present an extensive exploration metabasins...