Relativistic interactions for meson-nucleon systems in the clothed particle representation

The method of unitary clothing transformations (see [1–3] and references therein) enables one to represent the initial Hamiltonian H for interacting fields in terms of the creation (destruction) operators for the so-called clothed (physical) particles and their relativistic interactions. Using this clothed particle representation (CPR) of H and starting from the Yukawa-type couplings between fermions (nucleons and antinucleons) and bosons (π-, η-, ρ-, ω-mesons, etc.), we have derived a new family of the Hermitian and energy-independent interactions for physical processes πN → πN, NN → NN, NN ? πNN and NNN → NNN. Each of the obtained analytic expressions in momentum space is the sum of a Feynman-like part and some off-energy-shell correction term. The latter cannot appear when calculating the corresponding S-matrix elements by Feynman rules.     

Structural evolution of electroless Ni-P coating on Al-12 wt.% Si alloy during heat treatment at high temperatures

The work is concerned with the high-temperature heat treatment of an Al-12 wt.% Si alloy coated by an electroless Ni-P layer. The electroless deposition took place on a pre-treated substrate in a bath containing nickel hypophosphite, nickel lactate and lactic acid. Resulting Ni-P deposit showed a thickness of about 8 μm. The coated samples were heat-treated at 200-550 °C/1-24 h. LM, SEM, EDS and XRD were used to investigate phase transformations. Adherence to the substrate was estimated from the scratch test and microhardness of the heat-treated layers was also measured. It is found that various phase transformations occur, as both temperature and annealing time increase. These include (1) amorphous Ni-P → Ni + Ni₃P, (2) Al + Ni → Al₃Ni, (3) Ni₃P → Ni₁₂P₅ + Ni, (4) Ni₁₂P₅ → Ni₂P + Ni, and (5) Al₃Ni + Ni → Al₃Ni₂. The formation of intermetallic phases, particularly Al₃Ni₂, leads to significant surface hardening, however, too thick layers of intermetallics reduce the adherence to the substrate. Based on the growth kinetics of the intermetallic phases, diffusion coefficients of Ni in Al₃Ni and Al₃Ni₂ at 450-550 °C are estimated as follows: D(Al₃Ni, 450 °C) ≈ 6 × 10⁻¹² cm² s⁻¹, D(Al₃Ni, 550 °C) ≈ 4 × 10⁻¹¹ cm² s⁻¹, D(Al₃Ni₂, 450 °C) ≈ 1 × 10⁻¹² cm² s⁻¹ and D(Al₃Ni₂, 550 °C) ≈ 1 × 10⁻¹¹ cm² s⁻¹. Mechanisms of phase transformations are discussed in relation to the elemental diffusion.     

Hidden symmetry of the CKM and neutrino-mapping matrices

We propose that the smallness of the light quark masses is related to the smallness of the T (i.e. CP) violation in hadronic weak interactions. Accordingly, for each of the two quark sectors (“upper” and “lower”) we construct a 3 × 3 mass matrix in a bases of unobserved quark states, such that the “upper” and “lower” basis states correspond exactly via the W^± transitions in the weak interaction. In the zeroth approximation of our formulation, we assume T conservation by making all matrix elements real. In addition, we impose a “hidden symmetry” (invariance under simultaneous translations of all three basis quark states in each sector), which ensures a zero mass eigenstate in each sector.Next, we simultaneously break the hidden symmetry and T invariance by introducing a phase factor e^iχ in the interaction for each sector. The Jarlskog invariant J_CKM, as well as the light quark masses are evaluated in terms of the parameters of the model. Comparing formulas, we find that most unknown factors drop out, resulting in a simple relation with , to leading order in χ and m_s/m_b, with A, λ the Wolfenstein parameters. (Because of the large top quark mass, the contribution from upper quark sector can be neglected.) Setting J_CKM = 3.08 × 10⁻⁵, m_b = 4.7 GeV (1s mass), m_s = 95 MeV, A = 0.818, and λ = 0.227, we find , consistent with the accepted value m_d = 3 − 7 MeV.We make a parallel proposal for the lepton sectors. With the hidden symmetry and in the approximation of T invariance, both the masses of e and ν₁ are zero. The neutrino-mapping matrix V_ν is shown to be of the same Harrison-Perkins-Scott form which is in agreement with experiments. We also examine the correction due to T violation, and evaluate the corresponding Jarlskog invariant J_ν.     

Does the ϱ-ω mixing make possible an anomalous violation of the isotopic symmetry in the reactions πN → ω (N, Δ)?

The influence of electromagnetic ?⁰-ω-mixing on the reactions πN → ω(N, Δ) is analysed. It is pointed out that “strong” violation of the isotopic symmetry is possible in these reactions if one assumes that the ?⁰-ω interference in π^±N → π⁺π⁻ (N, Δ) occurs predominantly between the ?⁰ and ω production amplitudes with the π- and B-meson quantum numbers in the t-channel, respectively.     

Phantom Friedmann cosmologies and higher-order characteristics of expansion

We discuss a more general class of phantom (p < −?) cosmologies with various forms of both phantom (w < −1), and standard (w > −1) matter. We show that many types of evolution which include both Big-Bang and Big-Rip singularities are admitted and give explicit examples. Among some interesting models, there exist non-singular oscillating (or “bounce”) cosmologies, which appear due to a competition between positive and negative pressure of variety of matter content. From the point of view of the current observations the most interesting cosmologies are the ones which start with a Big-Bang and terminate at a Big-Rip. A related consequence of having a possibility of two types of singularities is that there exists an unstable static universe approached by the two asymptotic models—one of them reaches Big-Bang, and another reaches Big-Rip. We also give explicit relations between density parameters Ω and the dynamical characteristics for these generalized phantom models, including higher-order observational characteristics such as jerk and “kerk.” Finally, we discuss the observational quantities such as luminosity distance, angular diameter, and source counts, both in series expansion and explicitly, for phantom models. Our series expansion formulas for the luminosity distance and the apparent magnitude go as far as to the fourth-order in redshift z term, which includes explicitly not only the jerk, but also the “kerk” (or “snap”) which may serve as an indicator of the curvature of the universe.     

The analytical treatment of magnetic properties of three-layer ferrimagnetic superlattice

The Hamiltonian of the magnetic superlattice with three-layer unit cell was treated within the Boson formalism. The Boson Green’s functions (BGFs) were derived and it was shown that the system for BGFs splits into two sets which lead to the energies with opposite signs, although the energies of elementary excitations are strictly only the positive ones. However, when corresponding energies are used, the correlation functions calculated from both sets are the same. All the physically relevant quantities: total energy of the system, ground state energy, layer magnetization and zero-point (quantum) fluctuations are derived analytically by using both sets, showing that they lead to the same expressions. The Hamiltonian was also diagonalized by the so-called “u-v” transformation of the operators. It is shown that in spite of formal independence of the approaches, there exists a close relationship between BGF and “u-v” transformations.     

High resolution study of AsHD2: Ground state and the three bending fundamental bands ν3, ν4, and ν6

For the first time the infrared spectrum of the AsHD₂ molecule has been measured in the region of the bending fundamental bands ν₃, ν₄, and ν₆ on a Fourier transform spectrometer with a resolution of 0.0024 cm⁻¹ and analyzed. More than 5500 transitions with J^max = 26 have been assigned and used both to obtain “ground state combination differences” and for the determination of upper state ro-vibrational energies of the triad (001000), (000100), and (000001). Rotational parameters including centrifugal distortion coefficients up to octic terms of the ground vibrational state were calculated by fitting more than 500 “ground state combination differences” with J^max and . The obtained set of 24 parameters provides a rms-deviation of 0.00011 cm⁻¹. The upper energies were fitted with 52 parameters of an effective Hamiltonian which takes into account strong resonance interactions between all vibrational states of the triad (001000), (000100), and (000001). The rms-deviation for the energy levels considered in the fit is 0.00014 cm⁻¹.     

Systematic analysis of the Fourier transform spectrum of CH3OH between 400 and 950 cm

We have investigated a high-resolution Fourier transform (FT) absorption spectrum of the ¹³CH₃OH isotopomer of methanol from 400 to 950 cm⁻¹ with the “Ritz” program. We present the assignments of 7160 transitions, 3021 of which belong to A-symmetry, and 4139 to E-symmetry. These transitions occur between states labeled by K quantum numbers up to 14, and by torsional quantum numbers n up to 4. The “Ritz” program evaluated the energies of the 4684 involved levels with an accuracy of the order of 10⁻⁴ cm⁻¹. All of the assigned lines correspond to transitions involving torsionally excited levels within the ground small-amplitude vibrational state.     

Investigation of the optical anisotropy of PET and PEN films by VIS-FUV to IR spectroscopic ellipsometry

In the last years, a significant amount of research is being performed in the field of polymer research for novel applications, such as flexible electronic devices, photovoltaic cells, high performance optics, data storage, etc. Toward this direction, in this work, the optical anisotropy of biaxially stretched poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN) films has been extensively investigated. The optical properties of the films have been studied in terms of their optical, electronic and vibrational response, by Fourier transform IR spectroscopic ellipsometry (FTIRSE) (900-3500 cm⁻¹) and Vis-fUV variable angle SE (1.5-6.5 eV) techniques. The films optical anisotropy is the result of the stretching procedure during their fabrication, which results to the structural rearrangement of the macromolecular chains parallel to the stretching direction and to a higher structural symmetry. During the SE spectra analysis, the films have been approximated as uniaxial materials with their optic axis parallel to the sample/ambient interface leading to the accurate determination of the principal components ?_||(ω) and ?_⊥(ω) of the dielectric function ?(ω). The detailed study of the electronic transitions has been performed in the Vis-fUV region, where the characteristic features corresponding to the n → π* electronic transitions of the carbonyl -CO group and the ¹A_1g → ¹B_1u transition due to the π → π* excitation of the π-electron structures have been identified and analysed. Furthermore, the FTIRSE spectra allowed the accurate identification and assignment of the features of ?(ω) to the vibrational modes of the various bonding structures characteristic of the PET and PEN macromolecular chains.     

Exact solution of a model for πd induced reactions and its application to pion-nucleus reactions

Reduction techniques are applied to πd elastic scattering and π-absorption in a theory without anti-nucleons. In a one-pion approximation we derive two sets of exact coupled-channel equations for respectively the amplitudes T_πd,NN, T_{Nδ, NN} and T_{πd, πd}, T_{d, NΔ}- Alternatively we express in terms of the absorption amplitude T_{πd, NN} available solutions for a three-body problem restricted to the πd and NΔ channels. We explicitly demonstrate that our model (which comes close to the one of Thomas, Mizutani and Koltun) strictly respects the Pauli principle and avoids double-counting. Using the same technique we determine amplitudes for the (π, 2N) reaction and for π (in)elastic scattering on general nuclei in terms of amplitudes amongst the NN, NNπ channels. Both the elastic amplitude and the πA optical potential are shown to decompose into a multiple scattering part based on an input πN amplitude without the P₁₁ partial wave and calculable absorption corrections.     

High frequency shear ultrasonic properties of water/sorbitol solutions

Dynamic viscoelastic properties (G′ and G′′), ultrasonic shear velocity and attenuation were measured for aqueous solutions of sorbitol at 5 MHz. For pure sorbitol, the shear ultrasonic velocity reached 1470 m s⁻¹ with a density of 1500 kg m⁻³, consequently leading to a high acoustical impedance compared with “classical” polymers (polystyrene, nylon, polyethylene, Teflon, etc.). We demonstrate that this surprisingly high shear ultrasonic velocity for a viscoelastic material was due to the fact that the glass transition begins at a concentration above 85% of sorbitol in water. Hence, pure sorbitol is an ideal coupling material for high frequency shear experiments.     

The nano-structural properties of hydrogenated a-Si and Si-C thin films alloys by GISAXS and vibrational spectroscopy

Amorphous hydrogenated silicon (a-Si:H) with high hydrogen content (10-40 at.%), and non-stehiometric silicon-carbon (Si_1−xC_x) thin films with a variation of the carbon to silicon ratio up to 0.3, were deposited by using a magnetron sputtering source. The Si_1−xC_x thin films were partially crystallised after deposition by thermal annealing up to 1050 °C.The GISAXS (Grazing Incidence Small Angle X-ray Scattering) spectra of all of the prepared specimens indicate the presence of “particles” in the “bulk” of the films. For the a-Si:H samples, “particles” are most probably voids agglomerates with a variation in size between 3 and 6 nm. The mean value of the size distribution of the “particles” increases while its width slightly decreases with the hydrogen content in the film. This indicates a better structural ordering which is consistent with the results of Raman spectroscopy that show a decrease of the ratio between intensities of transversal acoustic (TA) and transversal optic (TO) phonon peaks, I_TA/I_TO, and a narrowing of the TO peak with increasing hydrogen content. These results are discussed as a consequence of the beneficial influence of hydrogen bombardment during the film growth.For Si_1−xC_x thin films, the “particles” are assumed to be SiC nano-crystals with a size between 2 and 14 nm and they are larger in films with a higher carbon concentration. Inside each of the films, the crystals are larger closer to surface and they grow faster in the direction parallel to the surface than in that which is perpendicular to it.     

Coherent π Electroproduction on the Deuteron

A general analysis of polarization phenomena for coherent pion electroproduction on deuterons is presented. The spin and isospin structures of the γ*+d→d+P⁰ amplitudes (where γ* is a virtual photon) are established and relationships between meson electroproduction on deuterons and on nucleons are given in the framework of the impulse approximation. The reaction e+d→e+d+π⁰ is investigated in detail, for a relatively large value of momentum transfer, 0.5 GeV²≤−k²≤2 GeV², both at threshold and in the region of Δ-isobar excitation. Special attention is devoted to the sensitivity of different contributions to the exclusive cross section for d(e, eπ⁰)d, as the γ*πω form factor or the NN-potential. The predicted k²-dependence of the cross section agrees well with the available experimental data.     

ππ production by ee annihilation in the ϱ energy range with the Orsay storage ring

A large solid angle detector has been used to observe two body events produced by electron-positron collisions in the Orsay storage ring. From the π⁺π⁻ excitation curve in the ? region we have deduced the amplitude and the phase of the ω-? interference, and the ? resonance paramaters: M_? = (775.4±7.3) MeV, Γ_? = (149.6 ± 23.2) MeV, √B(ω→π⁺π⁻) = 0.19 ± 0.05, φ = (85.7 ± 15.3)⁰, σ(e⁺e⁻→?) = (1.00 ± 0.13) μb at S = M_?², B(?→e⁺e⁻ = (4.1 ± 0.5) × 10⁻⁵, Γ(?→e⁺e⁻) = (6.1 ± 0.7) keV, (g_?²/4π) = 2.26 ± 0.25, (g_?ππ²/4π) = 2.84 ± 0.50.     

High resolution fourier transform spectrum of PD3 in the region of the stretching overtone bands 2ν1 and ν1+ν3

The infrared spectrum of the PD₃ molecule has been measured in the region of the first stretching overtone bands on a Fourier transform spectrometer with a resolution of 0.0068 cm⁻¹ and analyzed for the first time. More than 800 transitions with J^max=15 have been assigned to the bands 2ν₁ and ν₁+ν₃. An effective Hamiltonian was used which takes into account both the presence of resonance interactions between the states (2 0 0 0) and (1 0 1 0), and interactions of these with the third stretching vibrational state of the v=2 polyad, (0 0 2 0). A set of 44 spectroscopic parameters is obtained from the fit. This reproduces the 305 initial “experimental” upper rovibrational energies with an rms=0.0015 cm⁻¹.     

Magnetic-field-driven quantum critical behavior in graphite and bismuth

We study magnetotransport properties of graphite and rhombohedral bismuth samples and found that in both materials applied magnetic field induces the metal-insulator- (MIT) and reentrant insulator-metal-type (IMT) transformations. The corresponding transition boundaries plotted on the magnetic field-temperature (B − T) plane nearly coincide for these semimetals and can be best described by power laws T ∼ (B − B_c)^κ, where B_c is a critical field at T = 0 and κ = 0.45 ± 0.05. We show that insulator-metal-insulator (I-M-I) transformations take place in the Landau level quantization regime and illustrate how the IMT in quasi-3D graphite transforms into a cascade of I-M-I transitions, related to the quantum Hall effect in quasi-2D graphite samples. We discuss the possible coupling of superconducting and excitonic correlations with the observed phenomena, as well as signatures of quantum phase transitions associated with the M-I and I-M transformations.     

Absence of the fifth force problem in a model with spontaneously broken dilatation symmetry

A scale invariant model containing dilaton ? and dust (as a model of matter) is studied where the shift symmetry ? → ? + const. is spontaneously broken at the classical level due to intrinsic features of the model. The dilaton to matter coupling “constant” f appears to be dependent of the matter density. In normal conditions, i.e. when the matter energy density is many orders of magnitude larger than the dilaton contribution to the dark energy density, f becomes less than the ratio of the “mass of the vacuum” in the volume occupied by the matter to the Planck mass. The model yields this kind of “Archimedes law” without any especial (intended for this) choice of the underlying action and without fine tuning of the parameters. The model not only explains why all attempts to discover a scalar force correction to Newtonian gravity were unsuccessful so far but also predicts that in the near future there is no chance to detect such corrections in the astronomical measurements as well as in the specially designed fifth force experiments on intermediate, short (like millimeter) and even ultrashort (a few nanometer) ranges. This prediction is alternative to predictions of other known models.