Photoproduction of Boson Pairs in a Radiation-Dominated Universe. II

The average number of pairs of scalar massive particles produced by a decaying photon in a radiation-dominated universe is calculated. The dependence of the expression obtained on the energy of the initial photon is investigated. Numerical estimates are found for the formative time t ₀ of the processes of decay of photons in an early universe and for the total number N ^(±) _{out pair} of photoproduced scalar pairs. The estimates are: t ₀ 3 min and N ^(±) _{out pair} 10³¹·N ^(±) ₀(0), where N ^(±) ₀(0) is the total number of pairs produced from the vacuum of a free quantized field.     

The Radiation Spectrum of a Classical Electron Moving in a Radiation-Dominated Universe

The motion and radiation of a classical electron in a conformally flat Robertson–Walker space, which corresponds to the quasi-Euclidean model of a radiation-dominated universe, is considered. The spectral-angular distribution of the energy radiated by the electron is found; the dependence of the spectrum on the momentum of the electron is investigated; estimates for the coherence interval are given. The results obtained show that the radiation spectrum of a classical electron coincides with the quasiclassical limit of the spectral distribution of the photons radiated by a Dirac electron moving in a radiation-dominated universe.     

Photon Decays in the Radiation-Dominated Universe: Scalar Electrodynamics

The effect of the creation of an arbitrary number of massive pairs by a photon in the spatially flat model of the radiation-dominated Universe is considered. The process added-up probability is calculated within the framework of scalar quantum electrodynamics conformally related to the metric of a curved spacetime. The rate of photon decay in the radiation-dominated universe as well as the mean number of the created particles have been found. Comparison of the rate of the pair creation in the photon decays with the rate of the pair creation in the photon-photon collisions which take place in the Minkowski spacetime has been carried out. The estimates having been made show the number density of the particles created in the processes of the photon decays in the radiation-dominated Universe to be by a factor of 10³⁰ higher than the number density of the particles created from the vacuum of the free scalar field by the gravitational background.     

Study of Charged Pion Photoproduction on Deuteron with Tagged Photons

The reactions γd→π~- pp and γd→npπ~+π~- have been studied in an energy range from 0.8 to 1.1 GeV at the tagged photon facility of Laboratory of Nuclear Science,T ohoku University.Charged pions and protons in the final state were measured by using the Neutral Kaon Spectrometer (NKS2).The analysis of the γd→π~- pp was mainly used to check the acceptance of the NKS2 and to calibrate the tagged photon energy.The photoproduction of the Δ~(++)Δ~- was identified in the γd→npπ~+π~- reaction.Since the data analyses are still in progress,we issue an interim report and preliminary results.     

pp和PbPb碰撞中大横动量K和π的光生过程(英文)

基于微扰量子色动力学(pQCD),计算了考虑核遮蔽效应和喷注淬火效应的pp和PbPb碰撞中大横动量K和π的光生过程的产额。在光生过程中可以看到K~+/π~+的增强。数值计算结果表明,所考虑的光生过程对K和π产生是一个很好的修正。     

相对论重离子碰撞中π对相对动量分布

在π源动量分布的高斯分布下,给出了相对论重离子碰撞中非关联π对和关联π对的相对动量分布.用关联π对的相对动量分布得到球形高斯分布π源参数与椭球形高斯分布π源参数的解析关系,与相对论重离子中心碰撞1.8A GeV Ar+Pb的实验结果进行了对比.当π源温度更高时,应当用p₁(p)=N·exp(–m2+p2/T)进行计算.     

Investigation of Vector Perturbations in a Radiation-Dominated Cosmological Plasma

Based on the Maxwell–Einstein equations together with hydrodynamic plasma equations derived with allowance for Compton scattering, vector perturbations are examined for a homogeneous isotropic spatially-flat model of the Universe. The magnetic field strength generated by these vector perturbations in the radiation-dominated stage of evolution of the Universe is calculated.     

Theory of Gravitational-Inertial Field of Universe. I. Gravitational-Inertial Field Equations

In the series of present articles the original proposition is a generalization of the real world tensor by the introduction of a inertial field tensor. From this generalization it follows, particularly, that ?_ig_lm ? g_lm;i ≠ 0. This allows to use as a Lagrangian density of the field the expression A_g = k₁ g_lm;ig^lm _;kg^ik. On the basis of variational equations a system of more general covariant equations of the gravitational-inertial field is obtained. In the Einstein approximation these equations reduce to the field equations of Einstein. The solution of fundamental problems in the general theory of relativity by means of the new equations gives the same results as the solution by means of Einstein's equations. However, application of these equations to the cosmologic problem gives a result different from that obtained by Friedmann's theory. In particular, the solution gives the Hubble law as the law of motion of a free body in the inertial field - in contrast to Galileo-Newton's law.     

Pion–Pion Interaction in a Soluble Two-Level Nambu–Jona-Lasinio Model

We explore the interplay between the few-body aspects of few-pion states and the many-body aspects of their quark structure. We show for a schematic quasispin model similar to the Nambu–Jona-Lasinio model how one can derive rather accurately the pion–pion scattering length from the excitation spectrum in a box.     

Dynamics of Light in Teleparallel Bianchi-Type I Universe

In the present study, using the Fourier analysis method and considering the Bianchi-type I spacetime, we investigate the dynamics of photon in the torsion gravity, and show that the free-space Maxwell equations give the same results. Furthermore, we also discuss the harmonic oscillator behavior of the solutions.     

Free Probability for Pairs of Faces I

We consider a notion of bi-freeness for systems of non-commutative random variables with two faces, one of left variables and another of right variables. This includes bi-free convolution operations, bi-free cumulants, the bi-free central limit, and bi-freeness with amalgamation over an algebra B.     

Pion parton distributions in a nonlocal Lagrangian

We use phenomenological nonlocal Lagrangians, which lead to nontrivial forms for the quark propagator, to describe the pion. We define a procedure based on previous studies on nonlocal Lagrangians for the calculation of the pion parton distributions at low Q². The obtained parton distributions fulfill all the wishful properties. Using a convolution approach we incorporate the composite character of the constituent quarks. We evolve, using the Renormalization Group, the calculated parton distributions to the experimental scale and compare favorably with the data and draw conclusions.     

Pion polarizability in a chiral quark model

The pion polarizability is calculated in a chiral meson-quark model at the one-loop level. The results are in complete agreement with earlier ones obtained within a chiral meson-baryon theory. A critical discussion of a recent paper by Llanta and Tarrach is given.     

Theory of Gravitational-Inertial Field of Universe. II. On Critical Systems in Universe

Application of the equations of the gravitational-inertial field to the problem of free motion in the inertial field (to the cosmologic problem) leads to results according to which 1. all Galaxies in the Universe “disperse” from each other according to Hubble's law, 2. the “dispersion” of bodies represents a free motion in the inertial field and Hubble's law represents a law of motion of free body in the inertial field, 3. for arbitrary mean distribution densities of space masses different from zero the space is Lobachevskian. All critical systems (with Schwarzschild radius) are specific because they exist in maximalinertial and gravitational potentials. The Universe represents a critical system, it exists under the Schwarzschild radius. In high-potential inertial and gravitational fields the material mass in a static state or in motion with deceleration is subject to an inertial and gravitational “annihilation”. At the maximal value of inertial and gravitational potentials (= c²) the material mass is being completely “evaporated” transforming into radiation mass. The latter is being concentrated in the “horizon” of the critical system. All critical systems-black holes-represent geon systems, i.e. local formations of gravitational-electromagnetic radiations, held together by their own gravitational and inertial fields. The Universe, being a critical system, is “wrapped” in a geon crown.     

Pion condensation in a dense neutrino gas

We argue that using an equilibrated gas of neutrinos it is possible to probe the phase diagram of QCD for finite isospin and small baryon chemical potentials. We discuss this region of the phase diagram in detail and demonstrate that for large enough neutrino densities a Bose–Einstein condensate of positively charged pions arises. Moreover, we show that for non-zero neutrino density the degeneracy in the lifetimes and masses of the charged pions is lifted.     

Pion decay constants in a strong magnetic field

Decay constants of the charged and neutral pions in magnetic field are considered in the framework of the effective quark-antiquark lagrangian respecting Gell-Mann–Oakes–Renner (GOR) relations at zero field. The \(\sqrt {\frac{{{e_q}B}}{\sigma }} \) dependence is found in strong fields e_qB ? σ for the neutral pion, while the charged pion constant decreases as \(\sqrt {\frac{\sigma }{{{e_q}B}}} \).     

Wormholes in a Brane Universe

In this work, wormholes are discussed for the case where the classical brane action contains a 4-curvature. Equations of motion are obtained for R = 0 and R 0. Numerical solutions of these equations are found for special boundary conditions.     

The Evolution of Primordial Black Hole Masses in the Radiation-Dominated Era

We discuss in this work the behaviour of primordial black holes (PBHs) in the radiation era. Taking into account the Hawking evaporation and the absorption of energy we revisit the complete differential equation for the evolution of the mass of a PBH. We show that the mass can grow in this cosmological phase in a very slow fashion (even when considering the very high temperature of the radiation) if at all, and give a strong upper limit to the maximum accretion of mass. We evaluate relativistic effects due to the peculiar motion relative to the CMBR and show that the existence of relativistic black holes with very high mass absorption is highly unlikely. Finally we demonstrate that thermodynamic equilibrium between black holes and the cosmic radiation can not exist for finite times, and therefore initially non-evaporating PBHs must jump to the evaporating regime. This analysis supports the several efforts performed to look for signatures of evaporating holes.