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D. B. Blaschke

Publications and source records attributed to D. B. Blaschke.

51 records · Page 3Linked to original sources
arXiv2008

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 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 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.

physics.plasm-ph↗
arXiv2007

Color superconducting quark matter in compact stars

Recent indications for high neutron star masses (M \sim 2 M_sun) and large radii (R > 12 km) could rule out soft equations of state and have provoked a debate whether the occurence of quark matter in compact stars can be excluded as well. We show that modern quantum field theoretical approaches to quark matter including color superconductivity and a vector meanfield allow a microscopic description of hybrid stars which fulfill the new, strong constraints. For these objects color superconductivity turns out to be an essential ingredient for a successful description of the cooling phenomenology in accordance with recently developed tests. We discuss the energy release in the neutrino untrapping transition as a new aspect of the problem that hybrid stars masquerade themselves as neutron stars. Quark matter searches in future generations of low-temperature/high-density nucleus-nucleus collision experiments such as low-energy RHIC and CBM @ FAIR might face the same problem of an almost crossover behavior of the deconfinement transition. Therefore, diagnostic tools shall be derived from effects of color superconductivity.

nucl-th↗
arXiv2007

Equation of state for hybrid compact stars with a nonlocal chiral quark model

We study the thermodynamics of two flavor color superconducting (2SC) quark matter within a nonlocal chiral quark model, using both instantaneous and covariant nonlocal interactions. For applications to compact stars, we impose conditions of electric and color charge neutrality as well as beta equilibrium and construct a phase transition to the hadronic matter phase described within the Dirac-Brueckner-Hartree-Fock (DBHF) approach. We obtain mass-radius relations for hybrid star configurations which fulfill modern observational constraints, including compact star masses above 2 M_sun.

hep-ph↗
arXiv2007

Hybrid stars within a covariant, nonlocal chiral quark model

We present a hybrid equation of state (EoS) for dense matter in which a nuclear matter phase is described within the Dirac-Brueckner-Hartree-Fock (DBHF) approach and a two-flavor quark matter phase is modelled according to a recently developed covariant, nonlocal chiral quark model. We show that modern observational constraints for compact star masses (M ~ 2 M_sun) can be satisfied when a small vector-like four quark interaction is taken into account. The corresponding isospin symmetric EoS is consistent with flow data analyses of heavy ion collisions and points to a deconfinement transition at about 0.55 fm^-3.

nucl-th↗
arXiv2007

Laser acceleration of ion beams

We consider methods of charged particle acceleration by means of high-intensity lasers. As an application we discuss a laser booster for heavy ion beams provided, e.g. by the Dubna nuclotron. Simple estimates show that a cascade of crossed laser beams would be necessary to provide additional acceleration to gold ions of the order of GeV/nucleon.

physics.acc-ph↗
arXiv2006

Nonlocality effects on spin-one pairing patterns in two-flavor color superconducting quark matter and compact stars applications

We study the influence of nonlocality in the interaction on two spin one pairing patterns of two-flavor quark matter: the anisotropic blue color paring besides the usual two color superconducting matter (2SCb), in which red and green colors are paired, and the color spin locking phase (CSL). The effect of nonlocality on the gaps is rather large and the pairings exhibit a strong dependence on the form factor of the interaction, especially in the low density region. The application of these small spin-one condensates for compact stars is analyzed: the early onset of quark matter in the nonlocal models may help to stabilize hybrid star configurations. While the anisotropic blue quark pairing does not survive a big asymmetry in flavor space as imposed by the charge neutrality condition, the CSL phase as a flavor independent pairing can be realized as neutral matter in compact star cores. However, smooth form factors and the missmatch between the flavor chemical potential in neutral matter make the effective gaps of the order of magnitude $\simeq 10$ keV, and a more systematic analysis is needed to decide whether such small gaps could be consistent with the cooling phenomenology.

hep-ph↗
arXiv2006

Phase diagram of neutral quark matter in nonlocal chiral quark models

We consider the phase diagram of two-flavor quark matter under neutron star constraints for two nonlocal, covariant quark models within the mean field approximation. In the first case (Model I) the nonlocality arises from the regularization procedure, motivated by the instanton liquid model, whereas in the second one (Model II) a separable approximation of the one-gluon exchange interaction is applied. We find that Model II predicts a larger quark mass gap and a chiral symmetry breaking (CSB) phase transition line which extends 15-20% further into the phase diagram spanned by temperature (T) and chemical potential (mu). The corresponding critical temperature at mu=0, T_c(0)~140 MeV, is in better accordance to recent lattice QCD results than the prediction of the standard local NJL model, which exceeds 200 MeV. For both Model I and Model II we have considered various coupling strengths in the scalar diquark channel, showing that different low-temperature quark matter phases can occur at intermediate densities: a normal quark matter (NQM) phase, a two-flavor superconducting (2SC) quark matter phase and a mixed 2SC-NQM phase. Although in most cases there is also a gapless 2SC phase, this occurs in general in a small region at nonzero temperatures, thus its effect should be negligible for compact star applications.

hep-ph↗
arXiv2005

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 polarisation of the QED vacuum, which may be characterised as a plasma of e^+ e^- quasiparticle pairs with a density of ~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, ν. The density of residual pairs also grows with laser intensity but n_r \propto ν^2. With optical lasers at the forefront of the current generation, these dynamical QED vacuum effects may generate 5-10 observable two-photon annihilation events per laser pulse.

nucl-th↗
arXiv2004

Vacuum creation of massive vector bosons and its application to a conformal cosmological model

In the simple model of a massive vector field in flat space-time, we derive a kinetic equation of non-Markovian type, describing the vacuum pair creation under the action of external fields of different nature. We use for this aim the non-perturbative 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 a conformal-invariant scalar-tensor gravitational theory and its cosmological application. It is indicated that the choice of the equation of state (EoS) of the Universe allows to obtain a number density of the vector bosons that is sufficient to explain the observed number density of photons in the cosmic microwave background radiation. It is shown that the vector boson gas created from the vacuum is in a strong non-equilibrium state and corresponds to a cold dust-like EoS.

hep-ph↗
arXiv2004

Pulsations of the electron-positron plasma in the field of optical lasers

The possibility to observe vacuum electron-positron pair creation due to a powerful optical laser pulse is discussed. We employ a quantum kinetic formulation of the problem with a source term describing the vacuum pair production in a homogeneous electric field with arbitrary time dependence (dynamical Schwinger mechanism). For a periodic field weak in comparison with the critical value E_{cr}=m^2/|e|, the electron-positron plasma density changes approximately periodically with twice the field frequency. Under these conditions, the mean value $ $ for the density per period in the volume lambda^3 is a more appropriate characteristic quantity than the residual density n_r which is taken over an integer number of field periods and calculated using the imaginary time method. The value is proportional to the squared field intensity and does not depend on the frequency. We show that in terms of the parameter an optical laser can be more effective than a X-ray one. We expect that it is possible to observe the vacuum creation effect not only by means of the planned X-ray free electron lasers but already at present-day optical lasers.

physics.plasm-ph↗
arXiv2001

Exploring Quark Matter

These proceedings contain research results presented during the Workshops "Quark Matter in Astro- and Particle Physics" held at the University of Rostock, November 27-29, 2000 and "Dynamical Aspects of the QCD Phase Transition" held at the ECT* in Trento, March 12-15, 2001.

nucl-th↗
arXiv2001

A kinetic approach to eta' production from a CP-odd phase

The production of (eta,eta')- mesons during the decay of a CP-odd phase is studied within an evolution operator approach. We derive a quantum kinetic equation starting from the Witten-DiVecchia-Veneziano Lagrangian for pseudoscalar mesons containing a U_A(1) symmetry breaking term. The non-linear vacuum mean field for the flavour singlet pseudoscalar meson is treated as a classical, self-interacting background field with fluctuations assumed to be small. The numerical solution provides the time evolution of momentum distribution function of produced eta'- mesons after a quench at the deconfinement phase transition. We show that the time evolution of the momentum distribution of the produced mesons depend strongly on the shape of the effective potential at the end of the quench, exhibiting either parametric or tachyonic resonances. Quantum statistical effects are essential and lead to a pronounced Bose enhancement of the low momentum states.

nucl-th↗
arXiv2000

Dyson-Schwinger Equation Approach to the QCD Deconfinement Transition and J/Psi Dissociation

We consider an extension of the finite-temperature Dyson-Schwinger equation (DSE) approach to heavy mesons and quarkonia and apply it to calculate the cross section for the J/Psi breakup reaction J/Psi + pi --> D + D. We study the effects of chiral symmetry restoration in the light quark sector on this process and obtain a critical enhancement of the reaction rate at the chiral/ deconfinement transition. Implications for the kinetics of charmonium production in ultrarelativistic heavy-ion collisions are discussed with particular emphasis on the recently observed anomalous J/Psi suppression as a possible signal for quark matter formation.

hep-ph↗