arXiv subjects

Johann Rafelski

Publications and source records attributed to Johann Rafelski.

At least 91 records · Page 5Linked to original sources

arXiv2012

Possibility of Electroweak Phase Transition at Low Temperature

We study models of strong first order `low' temperature electroweak phase transition. To achieve this we propose a class of Higgs effective potential models which preserve the known features of the present day massive phase. However, the properties of the symmetry restored massless phase are modified in a way that for a large parameter domain we find a strong first order transition occurring at a temperature hundreds of times lower than previously considered possible.

hep-ph↗

arXiv2012

Electron-Positron Plasma Drop Formed by Ultra-Intense Laser Pulses

We study the initial properties and positron annihilation within a small electron-positron plasma drop formed by intense laser pulse. Such QED cascade initiated plasma is, in general, far below the chemical (particle yield) equilibrium. We find that the available electrons and positrons equilibrate kinetically, yet despite relatively high particle density, the electron-positron annihilation is very slow, suggesting a rather long lifespan of the plasma drop.

physics.plasm-ph↗

arXiv2012

Critical Acceleration and Quantum Vacuum

Little is known about the physics frontier of strong acceleration; both classical and quantum physics need further development in order to be able to address this newly accessible area of physics. In this lecture we discuss what strong acceleration means and possible experiments using electron-laser collisions and, data available from ultra-relativistic heavy ion collisions. We review the foundations of the current understanding of charged particle dynamics in presence of critical forces and discuss the radiation reaction inconsistency in electromagnetic theory and the apparent relation with quantum physics and strong field particle production phenomena. The role of the quantum vacuum as an inertial reference frame is emphasized, as well as the absence of such a `Machian' reference frame in the conventional classical limit of quantum field theory.

hep-ph↗

arXiv2012

Temperature of Electron Fluctuations in an Accelerated Vacuum

The electron vacuum fluctuations measured by $\cond$ do not vanish in an externally applied electric field $\calE$. For an exactly constant field, that is for vacuum fluctuations in presence of a constant accelerating force, we show that $\cond$ has a Boson-like structure with spectral state density $\tanh^{-1}(E/m)$ and temperature $\TEH = e\calE/mπ= a_v/π$. Considering the vacuum fluctuations of `classical' gyromagnetic ratio $g=1$ particles we find Fermi-like structure with the same spectral state density at a smaller temperature $T_1=a_v/2π$ which corresponds to the Unruh temperature of an accelerated observer.

hep-ph↗

arXiv2012

Properties of Gravitationally Bound Dark Compact Ultra Dense Objects

We consider compact astrophysical objects formed from dark matter fermions of mass 250 GeV to 100 TeV or from massless fermions hidden by vacuum structure of similar energy scale. These macroscopic objects have maximum stable masses of sub-planetary scale (asteroids) and radii of micron to centimeter scale. We describe the surface gravity and tidal forces near these compact ultra dense objects, as pertinent to signatures of their collisions with visible matter objects.

astro-ph.CO↗

arXiv2011

Spectra of Particles from Laser-Induced Vacuum Decay

The spectrum of electrons and positrons originating from vacuum decay occurring in the collision of two non-colinear laser pulses is obtained. It displays high energy, highly-collimated particle bunches traveling in a direction separate from the laser beams. This result provides an unmistakable signature of the vacuum decay phenomenon and could suggest a new avenue for development of high energy electron and/or positron beams.

hep-ph↗

arXiv2011

Pair Production from Asymmetric Head-on Laser Collisions

We evaluate particle production in highly asymmetric head-on collisions of lasers pulses due to non-perturbative coherent action of many photons. We obtain the yield of electron-positron pairs, which is controlled by the photon content of the weaker pulse, and show that the wavelength of the weaker pulse and the momentum asymmetry determine laboratory energy of the produced particles.

hep-ph↗

arXiv2011

Particle Production in s_NN = 2.76 TeV Heavy Ion Collisions

We obtain within the statistical hadronization model the hadron yields $dh/dy$ in heavy ion reactions at $\sqrt{s_{NN}} = 2.76$ TeV. We discuss the dependence both on hadronization temperature $T$, and on critical hadronization pressure $P$. We consider observables distinguishing the hadronization models and conditions.

hep-ph↗

arXiv2010

Vacuum Structure and Dark Energy

We consider that the universe is trapped in an excited vacuum state and the resulting excitation energy provides the observed dark energy. We explore the conditions under which this situation can arise from physics already known. Considering the example of how macroscopic QED fields alter the vacuum structure, we find that the energy scale 1 meV --- 1 eV is particularly interesting. We discuss how dark energy of this form is accessible to laboratory experiments.

hep-ph↗

arXiv2010

Unstable Hadrons in Hot Hadron Gas in Laboratory and in the Early Universe

We study kinetic master equations for chemical reactions involving the formation and the natural decay of unstable particles in a thermal bath. We consider the decay channel of one into two particles, and the inverse process, fusion of two thermal particles into one. We present the master equations the evolution of the density of the unstable particles in the early Universe. We obtain the thermal invariant reaction rate using as an input the free space (vacuum) decay time and show the medium quantum effects on $π+π\leftrightarrow ρ$ reaction relaxation time. As another laboratory example we describe the $K+K \leftrightarrow ϕ$ process in thermal hadronic gas in heavy-ion collisions. A particularly interesting application of our formalism is the $π^{0}\leftrightarrow γ+γ$ process in the early Universe. We also explore the physics of $π^{\pm}$ and $μ^{\pm}$ freeze-out in the Universe.

hep-th↗

arXiv2010

Multistrange Particle Production and the Statistical Hadronization Model

We consider the chemical freeze-out of $Ξ$, $\overlineΞ$ and $ϕ$ multistrange hadrons within a Statistical Hadronization Model inspired approach. We study particle yields across a wide range of reaction energy and centrality from NA49 at SPS and STAR at RHIC experiments. We constrain the physical conditions present in the fireball source of strange hadrons, and anticipate results expected at LHC.

hep-ph↗

arXiv2010

Thermal reaction processes in a relativistic QED plasma drop

The equilibrium size and temperature limits of thermally and chemically equilibrated $e^+e^-γ$ plasma drops are investigated at a given energy content. For a plasma to be equilibrated it must be opaque to electron and photon interactions. The opaqueness condition is determined by comparing plasma size with the mean free electron and photon paths. We calculate those paths using thermal Lorentz-invariant reaction rates for pair production and electron(positron) and photon scattering. The range of the corresponding plasma temperature and size is evaluated numerically. Considering the energy and size we find that the opaque and equilibrated plasma drop may be experimentally attainable.

physics.plasm-ph↗

arXiv2010

QED Energy-Momentum Trace as a Force in Astrophysics

We study the properties of the trace $\Tmm$ of the QED energy-momentum tensor in the presence of quasi-constant external electromagnetic fields. We exhibit the origin of $\Tmm$ in the quantum nonlinearity of the electromagnetic theory. We obtain the quantum vacuum fluctuation-induced interaction of a particle with the field of a strongly magnetized compact stellar object.

hep-ph↗

arXiv2009

Horizons of Strong Field Physics

Discussing the limitations on the validity of classical electrodynamics, we show that present day laser pulse technology applied to head-on-collisions with relativistic electrons generates fields strong enough to permit experimentation at the limits of validity of the Lorentz force, and the development of experimental tests of Mach's principle. We also discuss more distant opportunities for exploring the nature of laws of physics and the vacuum structure. We then conclude that the predictions of quantum electrodynamics in the presence of critical fields are not completely satisfactory and argue that the study of Laser materialization into particle pairs opens a new domain of quantum electrodynamics.

physics.acc-ph↗

arXiv2009

Quantum Vacuum Structure and Cosmology

Short review of riddles that lie at the intersection of quantum theory, particle physics and cosmology; dark energy as false vacuum; discussion of a possible detection experiment.

gr-qc↗

arXiv2009

Dark Energy Content of Nonlinear Electromagnetism

Quasi-constant external fields in nonlinear electromagnetism generate a contribution to the energy-momentum tensor with the form of dark energy. To provide a thorough understanding of the origin and strength of the effects, we undertake a complete theoretical and numerical study of the energy-momentum tensor $T^{μν}$ for nonlinear electromagnetism. The Euler-Heisenberg nonlinearity due to quantum fluctuations of spinor and scalar matter fields is considered and contrasted with the properties of classical nonlinear Born-Infeld electromagnetism. We also address modifications of charged particle kinematics by strong background fields.

hep-th↗

arXiv2009

Critical Hadronization Pressure

We discuss the bulk properties of QGP produced at RHIC obtained at time of hadronization. We argue that hadronization of quark--gluon plasma occurs at a critical pressure of 82 MeV/fm3, obtained for SPS energy range.

hep-ph↗

arXiv2009

Particle Production and Deconfinement Threshold

We present a detailed analysis of the NA49 experimental particle yield results, and discuss the physical properties of the particle source. We explain in depth how our analysis differs from the work of other groups, what advance this implies in terms of our understanding, and what new physics about the deconfined particle source this allows us to recognize. We answer several frequently asked questions, presenting a transcript of a discussion regarding our data analysis. We show that the final NA49 data at 40, 80, 158 AGeV lead to a remarkably constant extensive thermal chemical-freeze-out properties of the fireball. We discuss briefly the importance of thermal hadronization pressure.

hep-ph↗