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Deriving necessary and sufficient conditions for a scalar potential to be bounded from below (BFB) is a difficult task beyond the simplest cases. Recently, a set of BFB conditions was proposed for the $A_4$-invariant three-Higgs-doublet model (3HDM). However, that set of conditions relied on numerical scan, and a complete analytic proof was lacking. Here, we fill this gap. We prove that the conjectured BFB conditions are indeed necessary and sufficient within the neutral Higgs subspace. We bypass technically challenging direct algebraic computations with a novel technique that relies on an auxiliary function, which is related to the Higgs potential but which is easier to analyze. This technique may finally be sufficient to tackle the more involved case of the original Weinberg's 3HDM model., 17 pages, 3 figures

The advantages and limitations of methods and tools for monitoring the main parameters of the sea surface by HF radars are discussed. Methods and technical tools used in the HF range and for monitoring natural environments, including both the marine environment and the ionosphere, are compared. Their main parameters and significant differences of methods, instruments and mathematical data processing are noted. The main characteristics of the WERA and CODAR marine HF radars are given. The results of a two-point trial experiment in the vicinity of Gelendzhik were used to substantiate the methodology and instrumental solutions in order to create a domestic complex of observations in the water area of Novorossiysk. Based on the experiments carried out with both foreign and domestic radars, methods of increasing the efficiency of such radars due to their operation in the entire sounding frequency range are considered. Tests of the prototype of the multi-frequency locator confirmed the possibility of its functioning both in autonomous operation and as part of a geophysical complex, while solving a wide range of problems. In contrast to radars of the WERA and CODAR types, operating at one of the given sounding frequency, measurements can be carried out in a wide frequency range, which makes it possible to construct the fields of current velocities and sea surface waves in an extended range of distances at an appropriate resolution and determine the vertical profile of flows.

We report investigations of the nanosecond surface sliding discharge in supersonic airflows with the oblique shock wave at Mach numbers of the flow 1.30-1.60 in shock tube. We show that the surface sliding discharge developed in flows as a single channel located near a zone of interaction of the oblique shock with the boundary layer on the wall of the channel. A pulse voltage of 25 kV powered the discharge; the electric current was of 1 kA. The electron concentration in the localized discharge channel was (0.7-1.4).1015 cm-3 and the electron energy was of 1.8-2.2 eV from the analysis the emission spectra. High-speed flow field shadowgraphy after the surface sliding discharge showed that the localized discharge channel generates a strong shock wave, leading to restructuring the shock-wave structure of the flow within ∼100 μs and subsequent relaxation to a stationary configuration.

The purpose of the work is to study the effect of a pulsed surface discharge (plasma sheet) on the transverse flow upon its initiation in an unsteady gas-dynamic flow in a channel with an obstacle on the wall. Also a comparison with the effect of a pulsed volume discharge under similar conditions was studied. The dynamics of the blast waves propagating from the separation zone behind the obstacle after self-localization of the discharge plasma there is investigated.

Numerical simulations were performed of the nanosecond high-voltage breakdown in nitrogen at a voltage of 25–35 kV in the sub-centimeter discharge gaps. The streamer configurations were studied at two constant pressures, as well as at the radially varying pressure, simulating the pressure distribution in the axial region of the vortex “columnar” gas-dynamic flow. In each case, the characteristic parameters and propagation velocities of the primary and secondary streamers were calculated. It was ascertained that the law of pressure change in the radial direction strongly affects the spatial structure of the negative streamer.

The article presents a numerical study of vapor condensation appearing in an ejector. The ejector is a part of a device developed by the authors and used to purify air emissions. The article considers condensation of pure water vapor and condensation of vapor in a mixture of vapor and carrier gas. The system of axisymmetric Navier-Stokes equations and the system of moment equations are considered as a mathematical model for describing two-dimensional non-stationary gas-dynamic processes and processes of phase transitions in the device. The general system of equations is numerically solved using the finite volume method.

Analysis of plasma energy redistribution was conducted on the basis of experimental study of combined volume discharge of submicrosecond duration at its initiation in a gas-dynamic flow in rectangular channel with an obstacle. Shock wave diffraction on the obstacle (parallelepiped) on the channel wall was visualized. Effects of plasma localization at upward facing step and backward facing step were experimentally discovered and studied. CFD simulation patterns of the gas dynamic non stationary flow were compared to instant flow glow images.

The paper studies the process of cluster formation, condensation and evaporation in a viscous flow of a two-phase gas-droplet mixture in nozzles and free jets. The simulation results obtained using the gas-kinetic scheme and the method of moments are presented. The system of equations is solved with the second order accuracy finite volume method and using the approximate AUSM+up or HLL methods for solution of the Riemann problem.

The evolution of a shock wave interaction with a boundary layer on the surface of a shock tube channel after its reflection from a thin wedge is investigated. Visualization of the incident plane shock wave, the bow detached shock wave and flow behind the wedge in 48x24 mm channel was performed using the shadow method based on high-speed recording. The zone of boundary layer separation that occurs when the plane attached bow shock intersects with the channel wall is visualized on the basis of the pulse discharge glow recording. The flow evolution at incident shock wave Mach number of 2.3÷3.8 for the time interval up to 5 ms after the diffraction is investigated. The obtained data is compared with the corresponding CFD results: a numerical simulation based on the Euler equations of a nonstationary two-dimensional flow was performed under experimental conditions.

The numerical simulation of influence of viscous effects on flow inside shock tubes are described. We considered three shock tubes with different length-to-height ratio: 1 to 1 (Daru & Tenaud [6] case), 8 to 1 (extended Daru & Tenaud case) and 116 to 1 (HAST-1 [10-11] tube). Some details of different stages of the shock wave-boundary layer interaction are discussed.

Extended Higgs sectors offer rich opportunities for various forms of CP-violation. Here, we describe a new form of CP-conservation and discuss its consequences. We give a concrete example of a three-Higgs-doublet model dubbed CP4-3HDM with a CP-symmetry of order 4 and no other other accidental symmetries. If the vacuum conserves this symmetry, the model is CP-conserving with pairwise mass-degenerate extra neutral Higgs bosons. These fields cannot be classified as CP-even or CP-odd but they can be combined into complex physical fields which are CP-half-odd, that is, they pick up the $i$ factor upon CP transformation. These CP-half-odd scalars can be Yukawa-coupled to the fermion bilinears in a CP-conserving way. We discuss fundamental and phenomenological features of the model, and stress a peculiar clash between the CP-symmetry and any convention for the particle-antiparticle assignment., Comment: 9 pages, talk given at DISCRETE 2016: Fifth Symposium on Prospects in the Physics of Discrete Symmetries, Warsaw, 28 Nov - 3 Dec, 2016

Synopsis We present an intensity dependent study of transverse electron momentum distribution obtained from strong field ionization of argon using linearly polarized few-cycle (6 fs) laser pulses in the intensity range 1015W/cm2-1016W/cm2.

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'.

The two-Higgs doublet model (2HDM) can have two electroweak breaking, CP-conserving, minima. The possibility arises that the minimum which corresponds to the known elementary particle spectrum is metastable, a possibility we call the panic vacuum. We present analytical bounds on the parameters of the softly broken Peccei-Quinn 2HDM which are necessary and sufficient conditions to avoid this possibility. We also show that, for this particular model, the current LHC data already tell us that we are necessarily in the global minimum of the theory, regardless of any cosmological considerations about the lifetime of the false vacua.