An important first step in the program of hadronization of chiral quark models is the bosonization in meson and diquark channels. This procedure is presented at finite temperatures and chemical potentials for the SU(2) flavor case of the NJL model wi
th special emphasis on the mixing between scalar meson and scalar diquark modes which occurs in the 2SC color superconducting phase. The thermodynamic potential is obtained in the gaussian approximation for the meson and diquark fields and it is given the Beth-Uhlenbeck form. This allows a detailed discussion of bound state dissociation in hot, dense matter (Mott effect) in terms of the in-medium scattering phase shift of two-particle correlations. It is shown for the case without meson-diquark mixing that the phase shift can be separated into a continuum and a resonance part. In the latter, the Mott transition manifests itself by a change of the phase shift at threshold by pi in accordance with Levinsons theorem, when a bound state transforms to a resonance in the scattering continuum. The consequences for the contribution of pionic correlations to the pressure are discussed by evaluating the Beth-Uhlenbeck equation of state in different approximations. A similar discussion is performed for the scalar diquark channel in the normal phase. Further developments and applications of the developed approach are outlined.
In the present work a closed system of kinetic equations is obtained from the truncation of the BBGKY hierarchy for the description of the vacuum creation of an electron - positron plasma and secondary photons due to a strong laser field. This trunca
tion is performed in the Markovian approximation for the one-photon annihilation channel which is accessible due to the presence of the strong external field. Estimates of the photon production rate are obtained for different domains of laser field parameters (frequency nu and field strength E). A huge quantity of optical photons of the quasiclassical laser field is necessary to satisfy the conservation laws of energy and momentum of the constituents (e-, e+, gamma) in this channel. Since the number of these optical photons corresponds to the order of perturbation theory, a vanishingly small photon production rate results for the optical region and strongly subcritical fields E << E_c. In the gamma-ray region nu <~ m the required number of laser photons is small and the production rate of photons from the one-photon annihilation process becomes accessible to observations for subcritical fields E <~ E_c. In the infrared region the photon distribution has a 1/k spectrum typical for flicker noise.
It is well known that in the presence of strong external electromagnetic fields many processes forbidden in standard QED become possible. One example is the one-photon annihilation process considered recently by the present authors in the framework o
f a kinetic approach to the quasiparticle e-e+ gamma plasma created from vacuum in the focal spot of two counter-propagating laser beams. In these works the domain of large values of the adiabaticity parameter gamma >> 1 (corresponding to multiphoton processes) was considered. In the present work we estimate the intensity of the radiation stemming from photon annihilation in the framework of the effective mass model where gamma < 1, corresponding to large electric fields E < E_c=m^2/e and high laser field frequencies (the domain characteristic for X-ray lasers of the next generation). Under such limiting conditions the resulting effect is sufficiently large to be accessible to experimental observation.
We consider vacuum polarization effects in the one-photon annihilation channel within a kinetic description of the e+ e- plasma produced from the vacuum in the focal spot of counter-propagating laser beams. This entails essential changes in the struc
ture of the photon kinetic equation. We investigate the domain of large adiabaticity parameters gamma >> 1 where the photon radiation turns out to be very small. A more thorough examination of the domain gamma < 1 needs separate investigation. However, an exploratory study has shown that the one-photon annihilation channel can lead for some domains of laser field parameters (e.g., for the XFEL) to contributions accessible for observation.
In the present work a closed system of kinetic equations is obtained for the description of the vacuum creation of an electron - positron plasma and secondary photons due to a strong laser field. An estimate for the photon energy distribution is obta
ined. In the Markovian approximation the photon distribution has a 1/k spectrum (flicker noise).
We suggest a scenario where the three light quark flavors are sequentially deconfined under increasing pressure in cold asymmetric nuclear matter as found, e.g., in neutron stars. The basis for our analysis is a chiral quark matter model of Nambu--Jo
na-Lasinio (NJL) type with diquark pairing in the spin-1 single flavor (CSL), spin-0 two flavor (2SC) and three flavor (CFL) channels. We find that nucleon dissociation sets in at about the saturation density, n_0, when the down-quark Fermi sea is populated (d-quark dripline) due to the flavor asymmetry induced by beta-equilibrium and charge neutrality. At about 3n_0 u-quarks appear and a two-flavor color superconducting (2SC) phase is formed. The s-quark Fermi sea is populated only at still higher baryon density, when the quark chemical potential is of the order of the dynamically generated strange quark mass. We construct two different hybrid equations of state (EoS) using the Dirac-Brueckner Hartree-Fock (DBHF) approach and the EoS by Shen et al. in the nuclear matter sector. The corresponding hybrid star sequences have maximum masses of, respectively, 2.1 and 2.0 M_sun. Two- and three-flavor quark-matter phases exist only in gravitationally unstable hybrid star solutions in the DBHF case, while the Shen-based EoS produce stable configurations with a 2SC phase-component in the core of massive stars. Nucleon dissociation via d-quark drip could act as a deep crustal heating process, which apparently is required to explain superbusts and cooling of X-ray transients.
We investigate the effects of Pauli blocking on the properties of hydrogen at high pressures, where recent experiments have shown a transition from insulating behavior to metal-like conductivity. Since the Pauli principle prevents multiple occupation
of electron states (Pauli blocking), atomic states disintegrate subsequently at high densities (Mott effect). We calculate the energy shifts due to Pauli blocking and discuss the Mott effect solving an effective Schroedinger equation for strongly correlated systems. The ionization equilibrium is treated on the basis of a chemical approach. Results for the ionization equilibrium and the pressure in the region 4.000 K < T < 20.000 K are presented. We show that the transition to a highly conducting state is softer than found in earlier work. A first order phase transition is observed at T < 6.450 K, but a diffuse transition appears still up to 20.000 K.
We consider an alternative mechanism for the production of the cosmic microwave background (CMB) radiation. It is basically due to vacuum pair creation (VPC) of vector bosons (W and Z) as a consequence of a rapid W and Z mass generation during the el
ectroweak phase transition in the early Universe. The mechanism is as follows: after their pair crreation, the vector bosons may either annihilate directly into photons or decay into leptons and quarks which subsequently annihilate as lepton-antilepton and quark-antiquark pairs into photons. Preliminary estimates show that the number of CMB photons obtained this way can be sufficient to explain the presently observed CMB photon density. In this contribution we present an exactly soluble model for vacuum pair creation kinetics.
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 10^{20}-10^{22} W/cm^2, achievable with present-day petawatt lasers, and approaching
the Schwinger limit: 10^{29} 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 gamma-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 mu^+mu^- and pi^+pi^- 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.
We discuss an idea for how accreting millisecond pulsars could contribute to the understanding of the QCD phase transition in the high-density nuclear matter equation of state (EoS). It is based on two ingredients, the first one being a ``phase diagr
am of rapidly rotating compact star configurations in the plane of spin frequency and mass, determined with state-of-the-art hybrid equations of state, allowing for a transition to color superconducting quark matter. The second is the study of spin-up and accretion evolution in this phase diagram. We show that the quark matter phase transition leads to a characteristic line in the Omega-M plane, the phase border between neutron stars and hybrid stars with a quark matter core. Along this line a change in the pulsars moment of inertia entails a waiting point phenomenon in the accreting millisecond X-ray pulsar (AMXP) evolution: most of these objects should therefore be found along the phase border in the Omega-M plane, which may be viewed as the AMXP analog of the main sequence in the Hertzsprung-Russell diagram for normal stars. In order to prove the existence of a high-density phase transition in the cores of compact stars we need population statistics for AMXPs with sufficiently accurate determination of their masses and spin frequencies.
