Cross-sections of large-angle hadron production in proton– and pion–nucleus interactions II: beryllium nuclei and beam momenta from ±3 GeV/c to ±15 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons and charged pions, in the interactions with a 5% λ _abs thick stationary beryllium target, of proton and pion beams with momentum from ±3 GeV/c to ±15 GeV/c. Results are given for secondary particles with production angles 20° <θ<125°.     

Nucleon electromagnetic form factors in a quark–gluon core model

We study the nucleon electromagnetic form factors in a quark–gluon core model framework, which can be viewed as an extension of the Isgur–Karl model of baryons. Using this picture we derive nucleon electromagnetic dipole form factors at low Q ² and the deviation from the dipole form at high Q ², that are consistent with the existing experimental data.     

Suppression of forward dilepton production from an anisotropic quark–gluon plasma

We calculate the rapidity dependence of leading-order medium dilepton yields resulting from a quark–gluon plasma which has a local time-dependent anisotropy in momentum space. We present a phenomenological model which includes the temporal evolution of the plasma anisotropy parameter, ξ, and the hard momentum scale, p _hard. Our model interpolates between a 1+1 dimensional collisionally broadened expansion at early times and a 1+1 dimensional ideal hydrodynamic expansion at late times. Using our model, we find that at LHC energies, forward high-energy medium dilepton production would be suppressed by a factor of up to 3 if one assumes an isotropization/thermalization time of 2 fm/c. Therefore, it may be possible to use forward dilepton yields to experimentally determine the time of the onset of locally isotropic hydrodynamic expansion of the quark–gluon plasma as produced in ultrarelativistic heavy-ion collisions.     

Corrections to Hawking-like radiation for a Friedmann–Robertson–Walker universe

Recently, a Hamilton–Jacobi method beyond the semiclassical approximation in black hole physics was developed by Banerjee and Majhi. We generalize their analysis of black holes to the case of a Friedmann–Robertson–Walker (FRW) universe. It is shown that all the higher order quantum corrections in the single particle action are proportional to the usual semiclassical contribution. The corrections to the Hawking-like temperature and entropy of the apparent horizon for the FRW universe are also obtained. In the corrected entropy, the area law involves a logarithmic area correction together with the standard term with the inverse power of the area.     

Modeling erbium–thulium-co-doped fiber amplifier for 1400–1650 nm band

We present numerical models of tri-valence erbium ion and thulium ion-co-doped fiber amplifiers pumped by 800-nm and 980-nm lasers. The rate and power propagation equations of the models are numerically solved to analyze the gain as a function of co-doping concentrations, fiber length and signal wavelength. The results reveal that with 800-nm or 980-nm pump, gain competition exists between 1470- and 1530-nm bands, which may arise from the pump absorption competition and complicated energy transfer between the two types of active ions, and the results further show that the gain spectra may cover 305 nm (1375–1680 nm) for 800-nm pump and 160 nm (1400–1560 nm) for 980-nm pump. The doping concentrations and fiber length may be tuned to reduce the ripple of the gain spectra.     

Limits on a nucleon–nucleon monopole–dipole coupling from spin relaxation of polarized ultra-cold neutrons in traps

A new limit is presented on the axion-like monopole–dipole P, T-non-invariant interaction in a range (10⁻⁴–1) cm. The spin-dependent nucleon–nucleon potential between neutrons and nucleons of the walls of the cavity containing ultra-cold neutrons should affect the neutron depolarization probability at their reflection from the walls. The limit is obtained from existing data on the ultra-cold neutron depolarization probability per one collision with the walls.     

Photon motion in Kerr–de Sitter spacetimes

We study the general motion of photons in the Kerr–de Sitter black-hole and naked singularity spacetimes. The motion is governed by the impact parameters X, related to the axial symmetry of the spacetime, and q, related to its hidden symmetry. Appropriate ‘effective potentials’ governing the latitudinal and radial motion are introduced and their behavior is examined by the ‘Chinese boxes’ technique giving regions allowed for the motion in terms of the impact parameters. Restrictions on the impact parameters X and q are established in dependence on the spacetime parameters \(M, \Lambda , a\). The motion can be of orbital type (crossing the equatorial plane, \(q>0\)) and vortical type (tied above or below the equatorial plane, \(q<0\)). It is shown that for negative values of q, the reality conditions imposed on the latitudinal motion yield stronger constraints on the parameter X than that following from the reality condition of the radial motion, excluding the existence of vortical motion of constant radius. The properties of the spherical photon orbits of the orbital type are determined and used along with the properties of the effective potentials as criteria of classification of the KdS spacetimes according to the properties of the motion of the photon.     

Sum-of-Squares Results for Polynomials Related to the Bessis–Moussa–Villani Conjecture

We show that the polynomial S _m,k (A,B), that is the sum of all words in noncommuting variables A and B having length m and exactly k letters equal to B, is not equal to a sum of commutators and Hermitian squares in the algebra R〈X,Y〉, where X ²=A and Y ²=B, for all even values of m and k with 6≤k≤m−10, and also for (m,k)=(12,6). This leaves only the case (m,k)=(16,8) open. This topic is of interest in connection with the Lieb–Seiringer formulation of the Bessis–Moussa–Villani conjecture, which asks whether Tr (S _m,k (A,B))≥0 holds for all positive semidefinite matrices A and B. These results eliminate the possibility of using “descent + sum-of-squares” to prove the BMV conjecture.     

Cross-sections of large-angle hadron production in proton–and pion–nucleus interactions V: lead nuclei and beam momenta from ±3 GeV/c to ±15 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons, charged pions, and deuterons, in the interactions with a 5% λ _int thick stationary lead target, of proton and pion beams with momentum from ±3 GeV/c to ±15 GeV/c. Results are given for secondary particles with production angles 20°<θ<125°. Cross-sections on lead nuclei are compared with cross-sections on beryllium, copper, and tantalum nuclei.     

40 Gbps–80 GHz PSK-MDM based Ro-FSO transmission system

Bandwidth shortage of wireless carriers is a global issue that has further led to investigating the use of millimeter wave (mm-wave) in broadband cellular communication infrastructure. Radio over free space (Ro-FSO) optical system provides seamless integration of radio and optical platforms and makes it suitable for millimeter applications. This work is focused on transmission of two phase shift key encoded independent radio channels, each carrying 20 Gbps–40 GHz data, by mode division multiplexing of two modes: Laguarre Gaussian (LG) 00 and Hermite Gaussian (HG) 01. Furthermore, the modal decomposition of both channels is reported in terms of power coupling coefficient.     

Multi-Line Geometry of Qubit–Qutrit and Higher-Order Pauli Operators

The commutation relations of the generalized Pauli operators of a qubit–qutrit system are discussed in the newly established graph-theoretic and finite-geometrical settings. The dual of the Pauli graph of this system is found to be isomorphic to the projective line over the product ring . A “peculiar” feature in comparison with two-qubits is that two distinct points/operators can be joined by more than one line. The multi-line property is shown to be also present in the graphs/geometries characterizing two-qutrit and three-qubit Pauli operators’ space and surmised to be exhibited by any other higher-level quantum system. This work was partially supported by the Science and Technology Assistance Agency under the contract # APVT–51–012704, the VEGA grant agency projects # 2/6070/26 and # 7012 (all from Slovak Republic), the trans-national ECO-NET project # 12651NJ “Geometries over Finite Rings and the Properties of Mutually Unbiased Bases” (France) and by the CNRS–SAV Project # 20246 “Projective and Related Geometries for Quantum Information” (France/Slovakia).     

Liouville-like solutions in dilaton gravity with Gauss–Bonnet modifications

We investigate non-perturbative dilatonic solutions of the wide class of the modified gravity models that include Gauss–Bonnet terms with a general F(G) Lagrangian. We show that the presence of Liouville-like solutions is a characteristic feature of these models.     

Cross-sections of large-angle hadron production in proton– and pion–nucleus interactions VI: carbon nuclei and beam momenta from ±3 GeV/c to ±15 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons, charged pions, and deuterons, in the interactions with a 5% λ _int thick stationary carbon target, of proton and pion beams with momentum from ±3 GeV/c to ±15 GeV/c. Results are given for secondary particles with production angles 20°<θ<125°. Cross-sections on carbon nuclei are compared with cross-sections on beryllium, copper, tantalum and lead nuclei.     

ZnO–CuO core–shell nanorods and CuO-nanoparticle–ZnO-nanorod integrated structures

ZnO–CuO core–shell nanorods and CuO-nanoparticle–ZnO-nanorod integrated structures were synthesized for the first time by a two-stage solution process. Scanning electron microscopy and high-resolution transmission electron microscopy show that the diameter and the length of the nanorods are around 60 and 800 nm, respectively. The morphologies of outer CuO could be varied from nanoparticles to nanoshells by adjusting the solvent and dipping processes of copper (II) nitrate solution. The CuO nanoparticles are single-crystalline or highly textured structures with size of around 30 nm. The CuO shell with thickness of around 10 nm is constructed of nanocrystals with sizes in the range of 3–10 nm embedded in an amorphous matrix. Room-temperature cathodoluminescence measurements of the CuO–ZnO nanocomposites exhibit relatively sharp ultraviolet emissions at 380 nm as well as broad green and yellow emissions at 500 and 585 nm. The p-CuO/n-ZnO one-dimensional nanocomposites are promising for optoelectronic nanodevice applications.     

Reaction of Pentanol isomers with OH radical – A theoretical perspective

The stability of all the three isomeric forms of Pentanol has been examined with relative energy analysis. Even though 2-Pentanol is predicted to be most stable isomeric form, all the three isomeric forms undergo hydrogen atom abstraction reaction with OH radical. Among the proposed 18 different hydrogen atom abstraction reaction, the abstraction from CH₂ and CH functional group is found to be a favourable reactive site with low energy barrier in M06-2X/6-311+G(d,p) level of theory. Wiberg bond order analysis shows all the abstraction reactions are concreted but not synchronic in nature. Using force analysis, the calculated work done of individual reaction regions illustrates that structural rearrangements drive the reaction with higher contribution to the energy barrier. The rate constant calculated at M06-2X method for the most favourable reaction is well matched with available experimental data. Using the reported atmospheric OH concentration (1 × 10⁶ molecules/cm³), the life time of 1-Pentanol, 2-Pentanol and 3-Pentanol has calculated to be 18.66, 0.36 and 2.86 days, respectively.     

Evaluation of hybrid ytterbium–neodymium laser amplification at 1053 nm

We present here the modeling of a hybrid neodymium/ytterbium laser chain. The laser chain is modeled in energy, spectrum and gain for a relevant choice of ytterbium host materials. Special attention is given to spectral matching of both technologies. The model performance is benchmarked by an experimental setup of a Yb:glass regenerative-amplifier. Results indicate Yb:CaF₂ to be the best material for Nd:glass coupling.     

Stranski–Krastanov growth of InGaN quantum dots emitting in green spectra

Self-assembled InGaN quantum dots (QDs) were grown on GaN templates by metalorganic chemical vapor deposition. 2D–3D growth mode transition through Stranski–Krastanov mode was observed via atomic force microscopy. The critical thickness for In_0.67Ga_0.33N QDs was determined to be four monolayers. The effects of growth temperature, deposition thickness, and V/III ratio on QD formation were examined. The capping of InGaN QDs with GaN was analyzed. Optimized InGaN quantum dots emitted in green spectra at room temperature.     

Role of bare propagator poles in phenomenological Dyson–Schwinger type models

The generation of dressed meson–nucleon scattering-matrix poles is presented. A possible scenario for the interrelation of bare and dressed baryon poles is shown by using a particular version of coupled-channel Dyson–Schwinger type model. These findings are then applied to the Roper resonance, and the conclusion is drawn that it is dynamic in nature. A possible correlation between bare and dressed propagator poles on one side and the quantities of constituent quark-model calculations on the other side are discussed.     

Quenching effects on pulsed photoacoustic signals in NO2–air samples

A theoretical expression for the pulsed photoacoustic signal amplitude from NO₂–air mixtures is deduced based on a two-level system and the inhomogeneous wave equation, in the limit where the V-T relaxation time is longer than the laser pulse width (low buffer pressure). In this time limit, the photoacoustic signal from NO₂, at constant pressure, after excitation by pulses from a Nd:YAG laser at 532 nm, is measured at different buffer pressures. The relaxation rates are obtained by measuring the quenching of visible fluorescence induced by the same laser. The experimental dependence of the photoacoustic signal amplitude on air pressure shows a very good agreement with the model, where the measured relaxation rates are included.