Kinetic description of vacuum creation of massive vector bosons

In the simple model of massive vector field in a flat spacetime, we derive the kinetic equation of non-Markovian type describing the vacuum pair creation under action of external fields of different nature. We use for this aim the nonperturbative methods of kinetic theory in combination with a new element when the transition of the instantaneous quasiparticle representation is realized within the oscillator (holomorphic) representation. We study in detail the process of vacuum creation of vector bosons generated by a time-dependent boson mass in accordance with the framework of a conformal-invariant scalar-tensor gravitational theory and its cosmological application. It is indicated that the choice of the equation of state allows one to obtain a number density of vector bosons that is sufficient to explain the observed number density of photons in the cosmic microwave background radiation.     

A generalized quantum kinetic equation for models of relativistic nuclear dynamics

Zubarev’s method of non-equilibrium statistical operator is applied to problems of relativistic kinetic theory. Within this method, a generalized relativistic quantum kinetic equation for the relativistic Wigner function is derived with taking into account the drift term of the Vlasov type and the collision integral of the second order in particle interaction. It is shown that this result holds as well for gauge invariant theories in the case of slowly changing fields. An advantage of the developed approach is exemplified by the consideration of relativistic nuclear matter within the Walecka and Nambu-Jona-Lasinio models. Typical relativistic effects like retardation, spin degrees of freedom and antiparticle evolution are taken into consideration.     

Low momentum π-meson production from evolvable quark condensate

The pion production by sigma decay in hot and dense matter in the framework of the Nambu-Jona-Lasinio model [1] is investigated. The kinetic equation for joint evolution of pions and sigmas is constructed. The pion enhancement due to additional sigma creation via inertial mechanism is calculated. The text was submitted by the authors in English.     

Electrical transport and magnetic ordering in R 2Ti3Ge4 (R=Dy, Ho and Er) compounds

New R ₂Ti₃Ge₄ (R=Dy, Ho and Er) intermetallic compounds have been synthesized and characterized by X-ray diffraction and low temperature ac magnetic susceptibility, electrical resistivity and thermoelectric power measurements were carried out. The compounds crystallize in the parent, Sm₅Ge₄-type orthorhombic structure (space group Pnma) and lanthanide contraction is observed as one moves along the rare-earth series. The changeover from paramagnetic to antiferromagnetic phase happens at low temperatures and the ordering temperature scales with the de Gennes factor. The electrical resistivity is metallic with a negative curvature above 100 K. Thermopower displays a weak maximum at temperatures less than 50 K signifying the possible phonon and magnon drag effects.     

Vacuum particle creation under action of a strong external field: an example of irreversible behavior of a system with time reversal symmetry

On the basis of a kinetic equation (KE) of the Vlasov type, which is a strong non-perturbative consequence of the QED equations of motion in the quasiparticle representation, we investigate the irreversible behavior of the electron-positron plasma (EPP) created from vacuum under action of a pulsed external quasiclassical field. The basic KE is upon time reversal. Nevertheless the EPP reveals some features characteristic for irreversible processes. The nondecreasing entropy principle is introduced for the asymptotic in- and out-states: S _out ?? S _in . Some features of the entropy evolution are investigated for different excitation levels of the EPP.     

Dynamical Schwinger effect and high-intensity lasers. Realising nonperturbative QED

We consider the possibility of experimental verification of vacuum e⁺e^- pair creation at the focus of two counter-propagating optical laser beams with intensities 10²⁰–10²² W/cm²^{22}~{\rm W/cm}^2, achievable with present-day petawatt lasers, and approaching the Schwinger limit: 10²⁹ W/cm²^{29}~{\rm W/cm}^2 to be reached at ELI. Our approach is based on the collisionless kinetic equation for the evolution of the e⁺ and e^- distribution functions governed by a non-Markovian source term for pair production. As possible experimental signals of vacuum pair production we consider e⁺e^- annihilation into γ-pairs and the refraction of a high-frequency probe laser beam by the produced e⁺e^- plasma. We discuss the dependence of the dynamical pair production process on laser wavelength, with special emphasis on applications in the X-ray domain (X-FEL), as well as the prospects for μ⁺μ^- and π⁺π^- pair creation at high-intensity lasers. We investigate perspectives for using high-intensity lasers as “boosters” of ion beams in the few-GeV per nucleon range, which is relevant, e.g., to the exploration of the QCD phase transition in laboratory experiments.     

Pair production and optical lasers

Electron-positron pair creation in a standing wave is explored using a parameter-free quantum kinetic equation. Field strengths and frequencies corresponding to modern optical lasers induce a material polarization of the QED vacuum, which may be characterized as a plasma of e+e- quasiparticle pairs with a density of approximately 10(20) cm-3. The plasma vanishes almost completely when the laser field is zero, leaving a very small residual pair density n(r) which is the true manifestation of vacuum decay. The average pair density per period is proportional to the laser intensity but independent of the frequency nu. The density of residual pairs also grows with laser intensity but n(r) proportional to nu(2). With optical lasers at the forefront of the current generation, these dynamical QED vacuum effects can plausibly generate 5-10 observable two-photon annihilation events per laser pulse.