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We present the results of attosecond angular streaking of atomic Hydrogen using elliptically polarized, 5.5 fs pulses that are centered around 770 nm, within the intensity range of 1.65 to 4 × 1014 W/cm2. We measure angular offsets in the photo-electron momentum distribution relative to the peak of the electric field of light in the polarization plane. We find a strong agreement in these results with the solutions of complete 3D-TDSE simulations. Further, we compute the contribution of coulomb effects (between the ionized electron-parent ion) to the measured angular offsets using Yukawa potential, subtracting which yields the real 'tunneling delays'.

To study a flavour model with a non-minimal Higgs sector one must first define the symmetries of the fields; then identify what types of vacua exist and how they may break the symmetries; and finally determine whether the remnant symmetries are compatible with the experimental data. Here we address all these issues in the context of flavour models with any number of Higgs doublets. We stress the importance of analysing the Higgs vacuum expectation values that are pseudo-invariant under the generators of all subgroups. It is shown that the only way of obtaining a physical CKM mixing matrix and, simultaneously, non-degenerate and non-zero quark masses is requiring the vacuum expectation values of the Higgs fields to break completely the full flavour group, except possibly for some symmetry belonging to baryon number. The application of this technique to some illustrative examples, such as the flavour groups Delta(27), A4 and S3, is also presented., 13 pages, 3 figures, title and abstract changed, comments and references added; matches version to appear in The European Physical Journal C

This study is devoted to the comparison of continuous and kinetic approaches for two-dimensional numerical simulation of the gas flow transition regime. Regularized 13-moment Grad’s set of equations (R13) is used as continuum mathematical model and Unified Gas-Kinetic Scheme (UGKS) is used as kinetic method. The variant of explicit high resolution Godunov scheme with linear flow parameter reconstruction is chosen for numerical solution of the R13 set of equations. Five so-called kinetic boundary conditions are taken as a base of mathematical model of isothermal solid wall. The complete set of the wall boundary conditions is obtained by an approximation of the selected subset of the R13 bulk equations. The resulted set of nonlinear equations for the wall is solved with Newton’s numerical method. Our implementation of the UGKS follows in the basic details, and allows calculating continuous and rarefied flows in geometrically complex regions. Except well-known test cases, some complex shape micro device gas ...

We derive a unitarity relationship between the spin structure function gLT(x,Q2)=g1(x,Q2)+g2(x,Q2), the LT interference diffractive structure function and the spin-flip coupling of the pomeron to nucleons. Our diffractive mechanism gives rise to a dramatic small-x rise g LT (x,Q 2 )∼g 2 (x, Q 2 )∼(1/x) 2(1+δ g ) , where δg is an exponent of small-x rise of the unpolarized gluon density in the proton g(x, Q 2 ) at a moderate hard scale Q 2 for light flavour contribution and large hard scale Q 2 ∼m f 2 for heavy flavour contribution. It invalidates the Burkhardt–Cottingham sum rule. The found small-x rise of diffraction driven gLT(x,Q2) is steeper than given by the Wandzura–Wilczek relation under conventional assumptions on small-x behaviour of g1(x,Q2).

A relativistic plasma microwave amplifier tunable in a frequency range from 2 to 3 GHz has been studied. The output radiation spectrum and the electric field phase difference between the input and output signals have been measured for the first time. The output power reaches 30–70 MW and the amplifier gain is up to ≈30 dB.

We investigate finite abelian groups which can represent symmetries of the N-Higgs-doublet models with quarks. We build a general formalism based on the powerful method of the Smith normal form and obtain an analytic upper bound on the order of abelian symmetry groups for any N. We investigate in detail the case N=2 and rederive known results in a more compact and intuitive fashion. We also study the NHDM with the maximal finite abelian symmetry for all small N cases up to N=5, and show that in each case all Yukawa textures compatible with such symmetry originate from a unique basic structure. This work opens the way to a systematic exploration of phenomenology of the NHDM with a desired symmetry, and illustrates the power of the Smith normal form technique., Comment: 31 pages, no figures; v2: extra references, matches published version

Vortex electrons, - freely propagating electrons whose wavefunction has helical wavefronts, - could become a novel tool in the physics of electromagnetic radiation. They carry a non-zero intrinsic orbital angular momentum (OAM) $\ell$ with respect to the propagation axis and, for \ell \gg 1, a large OAM-induced magnetic moment, \mu ~ \ell \mu_B (\mu_B is the Bohr magneton), which influences the radiation of electromagnetic waves. Here, we consider in detail the OAM-induced effects by such electrons in two forms of polarization radiation, namely in Cherenkov radiation and transition radiation. Thanks to the large \ell, we can neglect quantum or spin-induced effects, which are of the order of \hbar \omega/E_e \ll 1, but retain the magnetic moment contribution \ell \hbar \omega/E_e \lesssim 1, which makes the quasiclassical approach to polarization radiation applicable. We discuss the magnetic moment contribution to polarization radiation, which has never been experimentally observed, and study how its visibility depends on the kinematical parameters and the medium permittivity. In particular, it is shown that this contribution can, in principle, be detected in azimuthally non-symmetrical problems, for example when vortex electrons obliquely cross a metallic screen (transition radiation) or move nearby it (diffraction radiation). We predict a left-right angular asymmetry of the transition radiation (in the plane where the charge radiation distributions would stay symmetric), which appears due to an effective interference between the charge radiation field and the magnetic moment one. Numerical values of this asymmetry for vortex electrons with E_e = 300keV and \ell = O(100-1000) are O(0.1-1%), and we argue that this effect could be detected with existing technology. The finite conductivity of the target and frequency dispersion play the crucial roles in these predictions., Comment: v2: 20 pages, 10 figures, 1 table; additional figure, table, explanations, and various text improvements, results unchanged

Electromagnetic radiation can be emitted not only by particle charges but also by magnetic moments and higher electric and magnetic multipoles. However experimental proofs of this fundamental fact are extremely scarce. In particular, the magnetic moment contribution has never been observed in any form of polarization radiation. Here, we propose to detect it using vortex electrons carrying large orbital angular momentum (OAM) \ell. The relative contribution of the OAM-induced magnetic moment, \ell \hbar \omega/E_e, becomes much larger than the spin-induced contribution \hbar \omega/E_e, and it can be observed experimentally. As a particular example, we consider transition radiation from vortex electrons obliquely incident on an interface between a vacuum and a dispersive medium, in which the magnetic moment contribution manifests itself via a left-right angular asymmetry. For electrons with E_e = 300 keV and \ell = 100-1000, we predict an asymmetry of the order of 0.1%-1%, which could be measured with existing technology. Thus, vortex electrons emerge as a new tool in the physics of electromagnetic radiation., Comment: 5 pages, 3 figures; v2: various language improvements, expanded discussion and references, results unchanged, matches the published version

Accurate knowledge of the intensity of focused ultrashort laser pulses is crucial to the correct interpretation of experimental results in strong-field physics. We have developed a technique to measure laser intensities approaching ${10}^{15}\phantom{\rule{0.28em}{0ex}}\text{W}/{\text{cm}}^{2}$ with an accuracy of 1$%$. This accuracy is achieved by comparing experimental photoelectron yields from atomic hydrogen with predictions from exact numerical solutions of the three-dimensional time-dependent Schr\"odinger equation. Our method can be extended to relativistic intensities and to the use of other atomic species.

In non-minimal Higgs mechanisms, one often needs to minimize highly symmetric Higgs potentials. Here we propose a geometric way of doing it, which, surprisingly, is often much more efficient than the usual method. By construction, it gives the global minimum for any set of free parameters of the potential, thus offering an intuitive understanding of how they affect the vacuum expectation values. For illustration, we apply this method to the S_4 and A_4-symmetric three-Higgs-doublet models. We find that at least three recent phenomenological analyses of the A_4-symmetric model used a local, not the global minimum. We discuss coexistence of minima of different types, and comment on the mathematical origin of geometrical CP-violation and on a new symmetry linking different minima., Comment: 18 pages, 3 figures; v2: corrected comments on Ref.[7]; v3: minor modifications, matches the published version

In the two Higgs doublet model, there is the possibility that the vacuum where the universe resides in is metastable. We present the tree-level bounds on the scalar potential parameters which have to be obeyed to prevent that situation. Analytical expressions for those bounds are shown for the most used potential, that with a softly broken $Z_2$ symmetry. The impact of those bounds on the model's phenomenology is discussed in detail, as well as the importance of the current Large Hadron Collider results in determining whether the vacuum we live in is or is not stable. We demonstrate how the vacuum stability bounds can be obtained for the most generic CP-conserving potential, and provide a simple method to implement them., Comment: 22 pages, 10 figures

We show that colliding vortex proton beams instead of (approximate) plane waves can lead to a direct measurement of how the overall phase of the scattering amplitude changes with the scattering angle. In elastic pp scattering, this will open a novel way to measure the parameter ρ(t) and probe the real part of the Pomeron.

The interaction of electrons of various energies with helium and cadmium atoms in a hollow-cathode discharge is analyzed. On the basis of the results of this analysis the conclusion is made that helium is ionized predominantly by electrons moving from the cathode wall to the cavity axis and having energies 70

In the Standard Model, the Higgs potential allows only one minimum at tree-level. But the open possibility that there might be two scalar doublets enriches the vacuum structure, allowing for the risk that we might now be in a metastable state, which we dub the panic vacuum. Current experiments at the LHC are probing the Higgs particle predicted as a result of the spontaneous symmetry breaking. Remarkably, in the two Higgs model with a softly broken U(1) symmetry, the LHC experiments already preclude panic vacuum solutions., 7 pages, 4 figures

N-Higgs-doublet models (NHDM) are among the most popular examples of electroweak symmetry breaking mechanisms beyond the Standard Model. Discrete symmetries imposed on the NHDM scalar potential play a pivotal role in shaping the phenomenology of the model, and various symmetry groups have been studied so far. However, in spite of all efforts, the classification of finite Higgs-family symmetry groups realizable in NHDM for any N>2 is still missing. Here, we solve this problem for the three-Higgs-doublet model by making use of Burnside's theorem and other results from pure finite group theory which are rarely exploited in physics. Our method and results can be also used beyond high-energy physics, for example, in study of possible symmetries in three-band superconductors., 5 pages; v2: expanded introduction, some minor corrections, matches the published version

In many models, stability of dark matter particles is protected by a conserved Z_2 quantum number. However dark matter can be stabilized by other discrete symmetry groups, and examples of such models with custom-tailored field content have been proposed. Here we show that electroweak symmetry breaking models with N Higgs doublets can readily accommodate scalar dark matter candidates stabilized by groups Z_p with any $p \le 2^{N-1}$, leading to a variety of kinds of microscopic dynamics in the dark sector. We give examples in which semi-annihilation or multiple semi-annihilation processes are allowed or forbidden, which can be especially interesting in the case of asymmetric dark matter., 10 pages

This study is devoted to the analysis of applicability of moment equations to the shock wave structure problem in a wide range of Mach numbers. A modification of original Grad's 13-moment set of equations, so-called regularized Grad's set of equations (R13), is taken as a mathematical model. The numerical method for this set is formulated as a variant of the explicit high-order Godunov scheme with linear reconstruction of flow parameters. The degree of applicability of moment equations is determined by comparisons with Direct Simulation Monte Carlo (DSMC) predictions. Numerical results for hard sphere molecules show that the R13 set of equations describes well the internal structure of the shock wave in a wide range of Mach numbers. Nevertheless, R13 set significantly overpredicts the overall temperature overshoot (about 3 times for M=8), which is apparently related to nonlinearity of the dependence of the product of the transverse temperature component and density on normalized density.

Shock waves have traditionally been studied and characterized by their movement through media. And alternatively, the parameters of a medium have been successfully diagnosed by its influence on a shock-wavesmotion. The propagation of shock waves through media with various types of inhomogeneity has always been of particular interest for a wide range of application in different fields of physics, like astrophysics, laser physics, aerodynamics and many others. There are lots of experimental, theoretical and numerical studies concerning interactions of shock waves with turbulence [1], vortices [2], near-wall fine particle or dust layers [3], preshock inhomogeneities induced by non-uniform energy deposition [4], isolated bubbles [5], thermal layers [6, 7], plasma formations [8, 9], etc. These interactions are apparently mutual - not only are the dynamics and the structure of waves altered but also the properties of the medium are changed in a post shock flow. The present work studies the structure of the gas-dynamic flow resulting from the propagation of a plain shock wave along a near-wall expanding layer of the gas excited by a high-current sliding surface discharge (“plasma sheet”).

This study is devoted to the two-dimensional numerical simulation of gas flow in the transition regime with solid wall interaction. The regularized 13-moment Grad's set of equations (R13) [1,2] was chosen as a mathematical model. A variant of explicit high order Godunov-type scheme with linear flow parameter reconstruction is used for the numerical solution of this set of equations. Numerical method for wall boundary conditions is based on Newton's iterative method suggested here. Couette and Poiseuille flows and lid-driven cavity flow were solved as test examples with this numerical scheme.

We show that colliding vortex beams instead of (approximate) plane waves can lead to a direct measurement of how the overall phase of the plane wave scattering amplitude changes with the scattering angle. Since vortex beams are coherent superpositions of plane waves with different momenta, their scattering amplitude receives contributions from plane wave amplitudes with distinct kinematics. These contributions interfere, leading to the measurement of their phase difference. Although interference exists for any generic wave packet collision, we show that using vortex beams dramatically enhances sensitivity to the phase in comparison with non-vortex beams. Since the overall phase is inaccessible in a plane wave collision, this measurement would be of great importance for a number of topics in hadronic physics, for example, meson production in the resonance region, physics of nucleon resonances, and small angle elastic hadron scattering., Comment: 18 pages, 5 figures; v2: introduction rewritten and expanded, matches the published version

High-energy photons and other particles carrying nonzero orbital angular momentum (OAM) emerge as a new tool in high-energy physics. Recently, it was suggested to generate high-energy photons with nonzero OAM (twisted photons) by the Compton backscattering of twisted optical photons on relativistic electron beams. Twisted electrons in the intermediate energy range have also been demonstrated experimentally; twisted protons and other particles can, in principle, be created in a similar way. Collisions of energetic twisted states can offer a new look at particle properties and interactions. A theoretical description of twisted particle scattering developed previously treated them as pure Bessel states and ran into difficulty when describing the OAM of the final twisted particle at nonzero scattering angles. Here we develop further this formalism by incorporating two additional important features. First, we treat the initial OAM state as a wave packet of a finite transverse size rather than a pure Bessel state. This realistic assumption allows us to resolve the existing controversy between two theoretical analyses for nonforward scattering. Second, we describe the final twisted particle in terms of the orbital helicity: the OAM projection on its average direction of propagation rather than on the fixed reaction axis. Using this formalism, we determine to what extent the twisted state is transferred from the initial to final OAM particle in a generic scattering kinematics. As a particular application, we prove that in the Compton backscattering the orbital helicity of the final photon stays close to the OAM projection of the initial photon.

Photons carrying non-zero orbital angular momentum (twisted photons) are well-known in optics. Recently, it was suggested to use Compton backscattering to boost optical twisted photons to high energies. Twisted electrons in the intermediate energy range have also been produced recently. Thus, collisions involving energetic twisted particles seem to be feasible and represent a new tool in high-energy physics. Here we discuss some generic features of scattering processes involving twisted particles in the initial and/or final state. In order to avoid additional complications arising from non-trivial polarization states, we focus here on scalar fields only. We show that processes involving twisted particles allow one to perform a Fourier analysis of the plane wave cross section with respect to the azimuthal angles of the initial particles. In addition, using twisted states one can probe the autocorrelation function of the amplitude, which is inaccessible in the plane wave collisions. Finally, we discuss prospects for experimental study of these effects., v2: 24 pages, 2 figures; merged with arXiv:1101.1630 and matches the published version

Physics of photons and electrons carrying orbital angular momentum (OAM) is an exciting field of research in quantum optics and electron microscopy. Usually, one considers propagation of these vortex beams in a medium or external fields and their absorption or scattering on fixed targets. Here we consider instead a beam-beam collision. We show that elastic scattering of a Bessel vortex beam with a counterpropagating plane wave naturally leads to two vortex-entangled outgoing beams. The vortex entanglement implies that the two final particles are entangled not only in their orbital helicities but also in opening angles of their momentum cones. Our results are driven by kinematics of vortex-beam scattering and apply to particle pairs of any nature: e-gamma, e^+e^-, ep, etc. This collisional vortex entanglement can be used to create pairs of OAM-entangled particles of different nature, and to transfer a phase vortex, for example, from low-energy electrons to high-energy protons., Comment: 4 pages, 2 figures; v2: title modified, introduction rewritten and expanded, results unchanged

N-Higgs doublet models (NHDM) are a popular framework to construct electroweak symmetry breaking mechanisms beyond the Standard model. Usually, one builds an NHDM scalar sector which is invariant under a certain symmetry group. Although several such groups have been used, no general analysis of symmetries possible in the NHDM scalar sector exists. Here, we make the first step towards this goal by classifying the elementary building blocks, namely the abelian symmetry groups, with a special emphasis on finite groups. We describe a strategy that identifies all abelian groups which are realizable as symmetry groups of the NHDM Higgs potential. We consider both the groups of Higgs-family transformations only and the groups which also contain generalized CP transformations. We illustrate this strategy with the examples of 3HDM and 4HDM and prove several statements for arbitrary N., Comment: 33 pages, 2 figures; v2: conjecture 3 is proved and becomes theorem 3, more explanations of the main strategy are added, matches the published version

A vacuum arc deposition technique for the production of multilayer structures is described. In the preliminary work described here, we used carbon as the low Z element and a heavy metal such as W or Pt as the high Z species to obtain periodic multilayers which can be used for X-ray reflectors. The plasma necessary for the deposition was produced by two vacuum arc plasma sources, each coupled to magnetic filters to prevent macroparticle transport to and contamination of the films. The multilayer structures were investigated by Auger spectroscopy and Rutherford backscattering spectrometry, and several multilayer samples were tested by measuring the specular reflectance and off-specular scattering, and by comparing these data with calculations using a Fresnel reflectance model. Analysis of X-ray results indicate that smooth, well defined layers are formed with reasonably small interface widths. With improvements in layer thickness reproducibility, it appears that vacuum arc deposition could produce useful multilayer X-ray interference mirrors.

A method for the plasma synthesis of metallic and composite thin films with atomically mixed interfaces is described. A large number of metal species can be applied and surface structures can be fabricated including films of metals and alloys, compounds including ceramics, and tailored multilayers. The added species can be energetically implanted below the surface or built up as a surface film with an atomically mixed interface with the substrate. A vacuum are produced metal plasma is used, and by adding a gas to the plasma region compound films can also be formed. The process parameters can be varied to fabricate a wide range of surface structures at the atomic level. We have demonstrated the method by synthesizing a number of metallic films as well as oxide and nitride films, including those described here: an yttrium film on silicon with an atomically mixed transition zone; a quarter-micron thick film of Pt on and mixed into Al; an Y/Ti multilayer structure in which the first and last layers were ion stitched to the material below; and an Al2O3 film on steel with a mixed bonding layer about 1000 A thick. Here we describe the background of the technique and the experimental results that we have obtained.

We study the scalar sector of the general N-Higgs-doublet model via geometric constructions in the space of gauge orbits. We give a detailed description of the shape of the orbit space both for general N and, in more detail, for N = 3. We also comment on remarkable analogies between NHDM and quantum information theory.

We consider the evolution of the ground state in the two Higgs doublet model during cooling down of the Universe after the big bang. Different regions in the space of free parameters of this model correspond to different sequences of thermal phase transitions. We discuss different paths of thermal evolution and corresponding evolution of physical properties of the system for different modern values of the parameters.

We continue our analysis of the general N-Higgs-doublet model and focus of the Higgs potential description in the space of gauge orbits. We develop a geometric technique that allows us to study the global minimum of the potential without explicitly finding its position. We discuss symmetry patterns of the NHDM potential, and illustrate the general discussion with various specific variants of the three-Higgs-doublet model., 28 pages, 9 figures; v2: introduction rewritten, matches the published version

We study the masses of the Higgs bosons in the most general two-Higgs-doublet model in a basis-independent approach. We adapt the recently developed Minkowski-space formalism to this problem and calculate traces of any power of the mass matrix in a compact and reparametrization-invariant form. Our results can be used to gain insight into the dynamics of the scalar sector of the general two-Higgs-doublet model.

Discontinuity breakdown conditions were realized experimentally by instant homogenous energy input in front of shock wave. Energy deposition was conducted using nanosecond gas discharges in spatial and surface area. A shock tube and special type of nanosecond electric discharge with plasma electrodes were used for this research. One and two-dimensional numerical simulation under experimental conditions has been undertaken. Pressure, density, temperature and velocity fields have been examined. Comparison of numerical data and schleiren images of shock wave after its interaction with discharge area was conducted. The configuration of disturbed shock wave was found to be in a good correspondence with one from numerical calculations. Numerical results showed possibility to achieve Richtmyer-Meshkov type instability without membrane.

Ginzburg-Landau model with two order parameters appears in many condensed-matter problems. However, even for scalar order parameters, the most general U(1)-symmetric Landau potential with all quadratic and quartic terms contains 13 independent coefficients and cannot be minimized with straightforward algebra. Here, we develop a geometric approach that circumvents this computational difficulty and allows one to study properties of the model without knowing the exact position of the minimum. In particular, we find the number of minima of the potential, classify explicit symmetries possible in this model, establish conditions when and how these symmetries are spontaneously broken, and explicitly describe the phase diagram., 36 pages, 7 figures; v2: added additional clarifications and a discussion on how this method differs from the MIB-approach

We continue to explore the consequences of the recently discovered Minkowski space structure of the Higgs potential in the two-Higgs-doublet model. Here, we focus on the vacuum properties. The search for extrema of the Higgs potential is reformulated in terms of 3-quadrics in the $3+1$-dimensional Minkowski space. We prove that 2HDM cannot have more than two local minima in the orbit space and that a twice-degenerate minimum can arise only via spontaneous violation of a discrete symmetry of the Higgs potential. Investigating topology of the 3-quadrics, we give concise criteria for existence of noncontractible paths in the Higgs orbit space. We also study explicit symmetries of the Higgs potential/Lagrangian and their spontaneous violation from a wider perspective than usual.

In view of the recent diffractive dijet data from CDF run II, we critically re-evaluate the standard approach to the calculation of central production of dijets in quasi-elastic hadronic collisions. We find that the process is dominated by the non-perturbative region, and that even perturbative ingredients, such as the Sudakov form factor, are not under theoretical control. Comparison with data allows us to fix some of the uncertainties. Although we focus on dijets, our arguments apply to other high-mass central systems, such as the Higgs boson., Comment: 37 pages, 18 figures. Two new appendices, and a discussion of the upper scale of the Sudakov form factor are introduced. The text about the calculation of the uncertainties has been rewritten

We calculate the amplitudes of J^{PC}=3^{--} meson production in diffractive DIS within the k_t-factorization approach, with a particular attention paid to the rho_3(1690) meson. We find that at all Q^2 the rho_3(1690) production cross section is 2-5 times smaller than the rho(1700) production cross section, which is assumed to be a pure D-wave state. Studying sigma_L and sigma_T separately, we observe domination of rho_3 in sigma_L and domination of rho(1700) in sigma_T and offer an explanation of this behavior in simple terms. We also find very strong contributions -- sometimes even domination -- of the s-channel helicity violating amplitudes. The typical color dipole sizes probed in rho_3 production are shown to be larger than those in the ground state rho production, and the energy dependence of rho_3 cross section turns out to be much flatter than the rho production cross section. All the conclusions about the relative behavior of rho_3(1690) and rho(1700) mesons are numerically stable against variations of input parameters.

The Higgs potential of 2HDM keeps its generic form under the group of transformation $GL(2,C)$, which is larger than the usually considered reparametrization group $SU(2)$. This reparametrization symmetry induces the Minkowski space structure in the orbit space of 2HDM. Exploiting this property, we present a geometric analysis of the number and properties of stationary points of the most general 2HDM potential. In particular, we prove that charge-breaking and neutral vacua never coexist in 2HDM and establish conditions when the most general explicitly $CP$-conserving Higgs potential has spontaneously $CP$-violating minima. We also define the prototypical model of a given 2HDM, which has six free parameters less than the original one but still contains all the essential physics. Our analysis avoids manipulation with high-order algebraic equations.

In this work, we continue to study the possibility of applying moment equations for strongly nonequilibrium flows by an example of the problem of the shock wave structure in a monatomic gas in a wide range of Mach numbers for various models of molecular interaction. The object of the study is the so-called regularized 13-moment Grad’s system (R13). First time, both linear and nonlinear versions of this system of equations were considered for the problem at such wide range of parameters. The Godunov method with increased accuracy is used as a numerical tool for solving the R13 system. The numerical results for the R13 system are analyzed by using data obtained by the Direct Simulation Monte Carlo (DSMC) method, experimental data, and analytical results. As a whole, the R13 system provides an adequate description of the shock wave structure in a wide range of Mach numbers. For Mach numbers around 2, good agreement with experimental and DSMC results is observed for both linear and nonlinear versions of the system. For high Mach numbers, the result strongly depends on the molecular interaction model used: shock wave structure predictions of the nonlinear R13 system are better for Maxwell molecules and worse for hard spheres as compared to the linear version. Particular attention in this work is paid to studying nonmonotonicity of the total temperature profile (temperature overshoot) in the structure of a strong shock wave. It is shown that the moment equations correctly predict the existence of the temperature overshoot. At the same time, the solution of the moment equations overpredicts the temperature overshoot at least two-fold for Mach number M = 8, and the nonlinear version of the R13 system yields a better result for this parameter than the linear version.

[Abstract] The paper is devoted to assessment of weight-ballistic efficiency of launch vehicles powered by propulsion system including nozzle of slot type with altitude compensation. Such slot nozzles possess property of gasdynamic regulation of altitude performances by means of creation of circular slot at the nozzle divergent part. Specific impulse increase at ascent in atmosphere with use of high-altitude slot nozzle is considered. Navier-Stokes equations with use of k–e turbulence model and the “near-wall” functions are numerically solved for viscous turbulent flows simulation. Regulators and compound computational grids are applied for flow simulation near areas of complex shapes. Results of computation of separated flows in slot nozzle and their comparison with experimental data are presented. It is shown that crisis of flow occurring during nozzle operation at high altitudes restricts gas leakages up to some 0.2%, and therefore their role is minor. Slot nozzles can be applied for launch vehicles operating within a wide range of ambient pressure.

Problem of tetrahedral meshing of three-dimensional domains whose boundaries are curved surfaces is wide open. Traditional approach consists in an approximation of curved boundaries by piecewise linear boundaries before mesh generation. As the result mesh quality may deteriorate. This paper presents a technique for Delaunay-based tetrahedralization in which a set of constrained facets is formed dynamically during face recovery and mechanisms for mutual retriangulation of the curved faces and the tetrahedralization are suggested. The proposed algorithm is constructed in such a way that a facet that was once added in the set of constrained facets is never split into small triangles. It allows retaining the high quality of surface mesh in the tetrahedralization, because during boundary recovery the surface mesh on the curved faces and the tetrahedralization are refined conjointly.

The thermal oxidation of Co alloy and Ni alloy thin films on top of Cu, has been studied as a function of film composition. Four different alloys were studied; CoWP, CoWB, CoMoB, and NiMoB. For the Co alloys, significant oxidation is observed after an air anneal above 350C, accompanied by Cu diffusion through the film to the surface. In contrast, for the NiMoB films, there is minimal oxidation of the surface even after a 400C anneal in air, and Cu diffusion through the film is greatly reduced. These results indicate that Ni-based barriers may be desirable in applications where self-aligned metal layers are used on top of Cu interconnects as a replacement for dielectric caps such as SiN and SiCN.

We obtain tree-level unitarity constraints for the most general Two-Higgs-Doublet Model (2HDM) with explicit $CP$-violation. We briefly discuss correspondence between possible violation of tree-level unitarity limitation and physical content of the theory.

In the two-Higgs-doublet model, different Higgs doublets can be viewed as components of a generic "hyperspinor". We decompose the Higgs potential of this model into irreducible representations of the SU(2) group of transformations of this hyperspinor. We discuss invariant combinations of the Higgs potential parameters lambda_i that arise in this decomposition and provide simple and concise sets of conditions for the hidden Z_2-symmetry, Peccei-Quinn symmetry, and explicit CP-conservation in 2HDM. We show that some results obtained previously by brute-force calculations are reduced to simple linear algebraic statements in our approach., 10 pages; v3: expanded section on consequences, added subsections on CP-conservation, PQ symmetry, RG evolution; v4: misprints corrected; to appear in Physics Letters B

Within the k_t-factorization framework, we study diffractive production of orbitally excited vector mesons and compare it with the production of radial excitations, focusing on the rho(1450)/rho(1700) case. At small Q^2, orbital excitation of light quarkonia is found to dominate over radial excitations in diffractive production. We predict strong suppression of the production of orbital excitations by longitudinal photons, which leads to very small sigma_L/sigma_T ratio. At small Q^2, the s-channel helicity violating transitions contribute \sim 10-15% of the transverse cross section and \sim 50% of the longitudinal cross section. We also study mixing between radial and orbital excitations and determine strategies towards clarification of S-wave/D-wave assignment to rho(1450) and rho(1700) mesons. The results are compared with the experimental data available, and predictions for future experiments are given., 9 pages, 5 figures

Experimental results from HERA on diffractive vector meson production and their theoretical interpretation within microscopic QCD are reviewed with an emphasis on the BFKL color dipole and kt-factorization approaches., Comment: 178 pages including 78 figures