A new study of the transition to uniform nuclear matter in neutron stars and supernovae

A comprehensive microscopic study of the properties of bulk matter at densities just below nuclear saturation ρ _s = 2.5 ∼ 10¹⁴ g cm⁻³, zero and finite temperature, and high neutron fraction, is outlined, and preliminary results presented. Such matter is expected to exist in the inner crust of neutron stars and during the core collapse of massive stars with M ≳ 8M _⊙. The text was submitted by the author in English.     

Gravitational wave background from neutron star phase transition

We study the generation of a stochastic gravitational wave (GW) background produced by a population of neutron stars (NSs) which go over a hadron-quark phase transition in its inner shells. We obtain, for example, that the NS phase transition, in cold dark matter scenarios, could generate a stochastic GW background with a maximum amplitude of h _BG ~ 10⁻²⁴, in the frequency band ν _obs ≃ 20–2,000 Hz for stars forming at redshifts of up to z ≃ 20. We study the possibility of detection of this isotropic GW background by correlating signals of a pair of Advanced LIGO observatories.     

Contribution of the massive photon decay channel to neutrino cooling of neutron stars

We consider massive photon decay reactions via intermediate states of electron-electron-holes and proton-proton-holes into neutrino-antineutrino pairs in the course of neutron star cooling. These reactions may become operative in hot neutron stars in the region of proton pairing where the photon due to the Higgs-Meissner effect acquires an effective mass m _γ that is small compared to the corresponding plasma frequency. The contribution of these reactions to neutrino emissivity is calculated; it varies with the temperature and the photon mass as T ^3/2 m _γ ^7/2 exp(−m _γ /T) for T<m ^γ . Estimates show that these processes appear as extra efficient cooling channels of neutron stars at temperatures T≅10⁹–10¹⁰ K. Zh. éksp. Teor. Fiz. 114, 385–397 (August 1998) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

A Class of Charged Relativistic Superdense Star Models

In this article we obtain a new class of well behaved charged solutions by using particular forms of the metric potential g ₄₄ and electric intensity, which involves a parameter K. The metric describing the superdense stars joins smoothly with the Reissner-Nordstrom metric at the pressure free boundary. This class of solutions describes well behaved charged fluid balls. The class of solutions gives range of parameter K (0.13≤K≤1.9999) for which the solution is well behaved hence, suitable for modeling of super dense star. The interior of the stars possess there energy density, pressure, pressure-density ratio and velocity of sound to be monotonically decreasing towards the pressure free interface. In view of the surface density 2×10¹⁴ gm/cm³, the maximum mass of the charged fluid balls and corresponding radius are 0.4711M _Θ and 7.0122 km. The red shift at the centre and boundary are found to be 0.1640 and 0.1100 respectively.     

Propagation of axions in a strongly magnetized medium

The polarization operator of an axion in a degenerate gas of electrons occupying the ground-state Landau level in superstrong magnetic fields H≫H ₀=m _e ² c ³/eℏ=4.41×10¹³ G is investigated in a model with a tree-level axion-electron coupling. It is shown that a dynamic axion mass, which can fall within the allowed range of values 10⁻⁵ eV≲m _a≲10² eV, is generated under the conditions of strongly magnetized neutron stars. As a result, the dispersion relation for axions is appreciably different from that in a vacuum. Zh. éksp. Teor. Fiz. 115, 3–11 (January 1999)     

Phase transition to color-flavor-locked matter and condensation of Goldstone bosons in neutron star matter

Deconfinement phase transition and condensation of Goldstone bosons in neutron star matter are investigated in a chiral hadronic model (also referred as to the FST model) for the hadronic phase (HP) and in the color-flavor-locked (CFL) quark model for the deconfined quark phase. It is shown that the hadronic-CFL mixed phase (MP) exists in the center of neutron stars with a small bag constant, while the CFL quark matter cannot appear in neutron stars when a large bag constant is taken. Color superconductivity softens the equation of state (EOS) and decreases the maximum mass of neutron stars compared with the unpaired quark matter. The K⁰ condensation in the CFL phase has no remarkable contribution to the EOS and properties of neutron star matter. The EOS and the properties of neutron star matter are sensitive to the bag constant B, the strange quark mass m_s and the color superconducting gap Δ. Increasing B and m_s or decreasing Δ can stiffen the EOS which results in the larger maximum masses of neutron stars.     

A lithium experiment in the program of solar neutrino research

Experiments sensitive to pp neutrinos from the Sun are very promising for precise measurement of the mixing angle ϑ ₁₂. A νe ⁻ scattering experiment (XMASS) and/or a charged-current experiment (indium detector) can measure the flux of electron pp neutrinos. One can find the total flux of pp neutrinos from a luminosity constraint after the contributions of ⁷Be and CNO neutrinos to the total luminosity of the Sun are measured. A radiochemical experiment utilizing a lithium target has high sensitivity to the CNO neutrinos; thus, it has a good promise for precise measurement of the mixing angle and for a test of the current theory of evolution of the stars. The text was submitted by the authors in English.     

Capacitance-voltage behaviour inp-type ɛ-GaSe single crystal ∥c at different temperatures

Summary  Capacitance-voltage measurements have been carried out onp-type ɛ-GaSe single crystal ∥c in the temperature range 300 to 360 K, with applied voltages of -1, 0 and +1 V. TheC-V measurements in this temperature range have shown a shift in capacitanceC and conductanceG to the higher values with an increase in temperature. The depletion layer widthW, the Debye length L_D and the doping densityN _α have been worked out and plots ofN _α vs. W have shown a decrease inW with an increase in temperature. The plots of L_D vs. N _α vary as 1/N_α^1/2, which gives N_αL_D ⋍ 3.3 × 10¹¹ charges/m² for doping density of 10¹⁶m⁻³. The values ofG at different temperatures have been used to obtain the activation energies, which are found to be ΔE ⋍ 0.11 eV for -1 and +1 V applied voltages, and ΔE ⋍ 0.06 eV for zero volt. The authors of this paper have agreed to not receive the proofs for correction.     

Tunable near-infrared optical properties of three-layered gold–silica–gold nanoparticles

The absorption spectra of gold–silica–gold nanoshells have been investigated by using Mie theory with variation of the geometry. With an increase in core radius the plasmon resonance for the lower energy mode ω ₋⁻ shows a distinct redshift while for the high-energy mode ω ₋⁺ shows a blueshift. It is surprising that with increasing middle layer thickness the resonance of ω ₋⁻ mode blueshifts first and then redshifts. In addition, an increase of the dielectric constant of the middle layer is found to reduce the resonance energies of the particle. The tunable near-infrared optical properties are discussed in terms of plasmon hybridization theory.     

Characteristics of high energy interactions II. Production spectra of Gamma-rays in graphite

Twenty high energy nuclear interactions produced in the graphite units of an emulsion chamber were recorded. The emulsion chamber was exposed to cosmic rays at an atmospheric depth of 10 g cm⁻² for about 7 hr over Hyderabad, India. Fourteen interactions which radiated energyΣ E _r⩾1000 GeV in the form ofγ-rays were analysed in detail. The median energy 〈Σ E _r〉 of the interactions was 1600 GeV. Results concerning the multiplicity, the transverse and longitudinal momentum distributions, and the fractional energy distribution ofγ-rays in these interactions are presented. The average transverse momentum ofπ ⁰—mesons <pt _π ⁰> is found to increase very slowly with the primary energyE ₀ and it can be approximated by the function <pt _π ⁰>=0·238E ₀ ^0.06 .     

Well Behaved Charged Generalization of Buchdahl’s Fluid Spheres

In the present article, we have obtained a class of well behaved charged analogues of Buchdahl (Phys. Rev. 116:1027–1034, 1959) neutral perfect fluid solution, which reduces to its neutral counter part in the absence of charge. The solutions so obtained are utilized to depict the super-dense stars models such as models for neutron stars and strange star. It is observed that the models are well behaved for restricted range of the parameter K (1<K≤1.64). Over all the maximum mass and corresponding radius is 2.4495M _Θ and 16.7289 respectively and moment of inertia . Also the pulsars character of the super-dense stars so obtained and has been analyzed with the help of moment of inertia. The analysis of the models reveals both vela and crab pulsars.     

Spectroscopy of quasiparticle excitations of superconducting bismuth cuprate at high pressures

We study the energy spectrum of Bi2223 (Bi_1.6Pb_0.4Sr_1.8Ca_2.2Cu₃O_x) at high hydrostatic pressures by Andreev-and tunneling-spectroscopy methods. We determine the gap anisotropy in the basal ab plane and find the following values for the parameters Δ(ϕ): Δ_max=42 mV, and Δ_min=19.5 mV (T _c =110 K and dT _c /dP=0.16 K/kbar). We detect an increase in the ratio R=2Δ_max/kT _c with pressure P; for Bi2223 cuprate, dR/dP≈0.017 kbar⁻¹. In the phonon-frequency region we detect a “softening,” due to pressure, of the high-frequency part of the phonon spectrum corresponding to “breathing” modes of oxygen, as well as other optical modes of Cu-O. The characteristic frequencies of the spectrum for ℏΩ>60 mV are found to decrease, with increasing pressure, at a rate d ln(ℏΩ)/dP≈−6.5±0.5×10⁻³ kbar⁻¹. This result explains the observed increase in the ratio 2Δ/kT _c (P) in the model of strong electron-phonon interaction. Zh. éksp. Teor. Fiz. 113, 1397–1410 (April 1998)     

“Quasi-Planck” spectra of capillary turbulence on the surface of liquid hydrogen

We report the first observation of “quasi-Planck” spectra of capillary turbulence on the surface of liquid hydrogen in the dissipation domain. Capillary waves have been driven by low-frequency random force. We have observed that the frequency spectrum of surface elevation changes its dependence from power-like 〈|η_ω²|〉 ∼ ω^−2,8 at middle-frequency domain to “quasi-Planck” distribution ∼e ^ω/ω _d at higher frequencies. The frequency ω _d is proportional to the boundary frequency between inertial interval and dissipation domain and it is scaled up with the increase of driving force.     

Level statistics inside the core of a superconductive vortex

A microscopic theory of the Efetov supermatrix sigma-model type is constructed for the low-lying electron states in a mixed superconductive-normal system with disorder. This technique is used for the study of the localized states in the core of a vortex in a moderately clean superconductor with τ ⁻¹≫ω ₀∼Δ²/E _F . At low energies ε≪ω _Th∼ (ω ₀/τ)^1/2, the energy level statistics is described by the “zero-dimensional” limit of this supermatrix theory, and the result for the density of states is equivalent to that obtained within Altland-Zirnbauer random matrix model. Nonzero modes of the sigma model increase the mean interlevel distance by the relative amount [2 ln (1/ω ₀ τ)]⁻¹. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 1, 78–83 (10 July 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Rare t-quark decays t → clj+lk? and t → c?jvk induced by doublets of scalar leptoquarks within the minimal four-color-symmetry model

The rare t-quark decays t → cl _j ⁺ l _k ⁻ and t → cṽ _j k _k induced by scalar-leptoquark doublets are considered within the minimal model involving four-color quark-lepton symmetry and the Higgs mechanism of quark and lepton mass splitting. The partial widths with respect to the decays being considered and the total widths Γ(t → cl ⁺′l ⁻) = Σ_j,k Γ(t → cl _j ⁺ l _k ⁻ ) and Γ(t → cl ⁺′l ⁻) = Σ_j,kΓ(t → cṽ _j v _k ) with respect to, respectively, the charged leptonic and neutrino modes are calculated. It is shown that, at scalar-leptoquark masses higher than the t-quark mass (m _S > m _t), the branching ratios for these modes are Br(t → cl ⁺′l ⁻) ≈ (3.5−0.4) × 10⁻⁵ and Br(t → cṽ′v) ≈ (7.1−0.8) × 10⁻⁵ at m _s = 180–250 GeV and an appropriate value of the leptoquark-mixing angle (sin β ≈ 0.2) and can increase for m _S < m _t to Br(t → cl ⁺′l ⁻) ≈ 0.03−0.002 and Br(t → cl ⁺′l ⁻) ≈ 0.46−0.05 for the charged mode at m _S = 150–170 GeV for sin β ≈ 1 and sin β ≈ 0.2, respectively. In the cases being considered, t-quark decays to pairs of charged leptons can be accessible to detection at LHC. In the last case, these decays could manifest themselves (for example, in dilepton events) at the Tevatron as well. Original Russian Text ? P.Yu. Popov, A.D. Smirnov, 2006, published in Yadernaya Fizika, 2006, Vol. 69, No. 6, pp. 1006–1016.     

Axion emission from a magnetized neutron gas

By using the polarization density matrix for a neutron in a magnetic field, the axion luminosity of magnetic neutron stars that is associated with the flip of the anomalous magnetic moment of degenerate nonrelativistic neutrons is calculated. It is shown that, at values of the magnetic-field induction in the region B ≳ 10¹⁸ G, this mechanism of axion emission is dominant in “young” neutron stars of temperature about a few tens of MeV units. At B ∼ 10¹⁷ G, it is one of the basic mechanisms. The Fermi energy of a degenerate neutron gas in a magnetic field is found, and it is shown that there is no such mechanism of axion emission in the degenerate case.     

Polyaniline-poly(vinyl alcohol) IPN-composite prepared from potassium dichromate embedded PVA film: a material for humidity sensing application

Polyaniline-polyvinyl alcohol (PANI-PVA) interpenetrating network composite film is successfully prepared by in situ polymerization of aniline within PVA film embedded with different concentrations of potassium dichromate (K₂Cr₂O₇). The resulted composite is characterized by UV-Visible spectroscopy, SEM and XRD, TGA techniques and confirmed the formation of interpenetrating network formation of PANI within PVA matrix. Electrical conductivity of the composite films increase from 10⁻⁶ to 10⁻² S/cm with the increase in the loading of dichromate from 10⁻⁴ to 10⁻² M. Further, exposing in humidity environment, the conductivity of the composite films increases from 14 to 100% with the increase in humidity conditions from 11.3 to 84.3%.     

New perovskite oxides LaBa<Emphasis Type="Italic">M</Emphasis>CoO<Subscript>5 + δ</Subscript> (<Emphasis Type="Italic">M</Emphasis> = Fe,Cu): Synthesis,structure, and properties

The electrical resistivity ρ and the thermopower S of ceramic materials LnBaCuFeO_{5 + δ} (Ln= La, Pr, Nd, Sm, Gd-Lu) are measured in air at temperatures in the range from 300 to 1100 K. All the studied ferrocuprates are p-type semiconductors. The electrical resistivity ρ and the thermopower S of these compounds increase with a decrease in the radius of the Ln ³⁺ cation (with an increase in the number of 4f electrons n in Ln ³⁺). The nonmonotonic behavior of the dependences ρ=f(n) and S=f(n) indicates that the electrical properties of the layered ferrocuprates LnBaCuFeO_{5 + δ} depend on the electronic configuration of the Ln ³⁺ cation. The power factors P calculated for the LnBaCuFeO_{5 + δ} ceramic materials from the experimental values of ρ and S increase with increasing temperature and, at T = 1000 K, reach the maximum values P = 102.0 and 54.1 μW m⁻¹ K⁻² for Ln = Pr(4f ²) and Sm(4f ⁵), respectively, and become close to each other and equal to 30–35 μW m⁻¹ K⁻² for Ln = Gd(4f ⁷), Dy(4f ⁹), and Ho(4f ¹⁰).     

A microscopic study of deformation systematics in <Superscript>154–166</Superscript>Dy isotopes

The Hartree-Bogoliubov (HB) framework of calculations has been applied for calculating various nuclear structure quantities for ^154–166Dy mass chains. In this framework, the intrinsic quadrupole moments, the low-lying yrast states (E ₂⁺ and E ₄⁺) and occupation numbers for various shell model orbits have been obtained. The calculated results indicate that the observed onset of deformation in going from ¹⁵⁴Dy to ¹⁶⁶Dy arises due to enhanced occupation of (h _11/2)_π orbit, increased polarization of (d _5/2)_π orbit and increase in the occupation of down-slopping ‘k’ components of (i _13/2)_υ and (h _9/2)_υ orbits.