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Johann Rafelski

Publications and source records attributed to Johann Rafelski.

At least 55 records · Page 3Linked to original sources

Discovery of Quark-Gluon-Plasma: Strangeness Diaries

We look from a theoretical perspective at the new phase of matter, quark-gluon plasma (QGP), the new form of nuclear matter created at high temperature and pressure. Here I retrace the path to QGP discovery and its exploration in terms of strangeness production and strange particle signatures. We will see the theoretical arguments that have been advanced to create interest in this determining signature of QGP. We explore the procedure used by several experimental groups making strangeness production an important tool in the search and discovery of this primordial state of matter present in the Universe before matter in its present form was formed. We close by looking at both the ongoing research that increases the reach of this observable to LHC energy scale $pp$ collisions, and propose an interpretation of these unexpected results.

hep-ph↗

Classical neutral point particle in linearly polarized EM plane wave field

We study a covariant classical model of neutral point particles with magnetic moment interacting with external electromagnetic fields. Classical dynamical equations which reproduce a correct behavior in the non-relativistic limit are introduced. We also discuss the non-uniqueness of the covariant torque equation. The focus of this work is on Dirac neutrino beam control. We present a full analytical solution of the dynamical equations for a neutral point particle motion in the presence of an external linearly polarized EM plane wave (laser) fields. Neutrino beam control using extremely intense laser fields could possibly demonstrate Dirac nature of the neutrino. However, for linearly polarized ideal laser waves we show cancellation of all leading beam control effects.

hep-ph↗

Magnetic Dipole Moment in Relativistic Quantum Mechanics

We investigate relativistic quantum mechanics (RQM) for particles with arbitrary magnetic moment. We compare two well known RQM models: a) Dirac equation supplemented with an incremental Pauli term (DP); b) Klein-Gordon equations with full Pauli EM dipole moment term (KGP). We compare exact solutions to the external field cases in the limit of weak and strong (critical) fields for: i) homogeneous magnetic field, and ii) the Coulomb $1/r$-potential. For i) we consider the Landau energies and the Landau states as a function of the gyromagnetic factor ($g$-factor). For ii) we investigate contribution to the Lamb shift and the fine structure splitting. For both we address the limit of strong binding and show that these two formulations grossly disagree. We discuss possible experiments capable of distinguishing between KGP and DP models in laboratory. We describe impact of our considerations in astrophysical context (magnetars). We introduce novel RQM models of magnetic moments which can be further explored.

hep-ph↗

Lepton Number and Expansion of the Universe

We show that the non-integer effective number of neutrinos $N^{\mathrm{eff}}_ν$ can be understood as an effect of lepton $L$ asymmetry in the early Universe carried by the Dirac neutrino cosmic background. We show that $N_ν^{\mathrm{eff}}=3.36\pm0.34$ (CMB only) and $N_ν^{\mathrm{eff}}= 3.62\pm0.25$ (CMB and $H_0$) require a ratio between baryon number $B$ and lepton number to be $1.16 \times 10^{-9}\leqslant B/|L|\leqslant 1.51 \times 10^{-9}$. These values are close to the baryon-to-photon ratio $0.57\times 10^{-9}\leqslant B/N_γ\leqslant 0.67\times10^{-9}$. Thus instead of the usual $|L|\ll N_γ$ and $B\simeq |L|$, we propose to use $0.4 \leqslant |L|/N_γ\leqslant 0.52$ and $B\ll|L|$ as another natural choice, which resolves the tension between Planck-CMB and $H_0$ and leads to a non-integer value of $N_ν^{\mathrm{eff}}>3$.

hep-ph↗

Virtual axion-like particle complement to Euler-Heisenberg-Schwinger action

We modify action in an external electromagnetic field to include effects of virtual axion-like particle (ALP) excitations. A measurable addition to QED-Euler-Heisenberg-Schwinger (EHS) action is obtained and incorporated into experimental constraints placed on ALP mass and coupling to two photons. The regime of these constraints in which the ALP vacuum effect surpasses the EHS effect is characterized. We show that probing of the virtual vacuum effect offers an alternative method in search for physics related to ALPs.

hep-ph↗

Vacuum stabilized by anomalous magnetic moment

An analytical result for Euler-Heisenberg effective action, valid for electron spin $g-$factor $|g|<2$, was extended to the domain $|g|>2$ via discovered periodicity of the effective action. This allows for a simplified computation of vacuum instability modified by the electrons measured $g=2.002319$. We find a strong suppression of vacuum decay into electron positron pairs when magnetic fields are dominant. The result is reminiscent of mass catalysis by magnetic fields.

hep-ph↗

Temperature Dependence of the Neutron Lifespan

Current precision big bang nucleosynthesis (BBN) studies motivate us to revisit the neutron lifespan in the plasma medium of the early universe. The mechanism we explore is the Fermi-blocking of decay electrons and neutrinos by plasma. As result, neutrons live longer and we find a significant 6.4\% modification of neutron abundance in the BBN era arising from in plasma modification of the neutron lifetime. This effect can influence the final abundances of the light elements in BBN.

nucl-th↗

Strong fields and neutral particle magnetic moment dynamics

Interaction of magnetic moment of point particles with external electromagnetic fields experiences unresolved theoretical and experimental discrepancies. In this work we point out several issues within the relativistic quantum mechanics and the QED and we describe effects related to a new covariant classical model of magnetic moment dynamics. Using this framework we explore the invariant acceleration experienced by neutral particles coupled to an external plane wave field through the magnetic moment: we study the case of ultra relativistic Dirac neutrinos with magnetic moment in the range of $10^{-11}$ to $10^{-20}$ $μ_\mathrm{B}$; and we address the case of slowly moving neutrons. We explore how critical accelerations for neutrinos can be experimentally achieved in laser-pulse interactions. The radiation of accelerated neutrinos can serve as an important test distinguishing between Majorana and Dirac nature of neutrinos.

hep-ph↗

Die Erste Stunde (The first hour)

I recall my "first hour" events following on my meeting in Fall 1968 in the classroom with my academic teacher and thesis mentor Prof. Dr. Dr. h.c. multiple Walter Greiner. My comments focus on the creation of the new "strong fields" domain of physics in Frankfurt. I argue that this was the research field closest to Walter's heart during his lustrous academic career. I will describe the events that lead on to Greiner's course books, Walters actions leading to the rise of Frankfurt School of Theoretical Physics, and show how a stability principle defined his science.

physics.hist-ph↗

Relativistic Dynamics of Point Magnetic Moment

The covariant motion of a classical point particle with magnetic moment in the presence of (external) electromagnetic fields is revisited. We are interested in understanding Lorentz force extension involving point particle magnetic moment (Stern-Gerlach force) and how the spin precession dynamics is modified for consistency. We introduce spin as a classical particle property inherent to Poincareé symmetry of space-time. We propose a covariant formulation of the magnetic force based on a \lq magnetic\rq\ 4-potential and show how the point particle magnetic moment relates to the Amperian (current loop) and Gilbertian (magnetic monopole) description. We show that covariant spin precession lacks a unique form and discuss connection to $g-2$ anomaly. We consider variational action principle and find that a consistent extension of Lorentz force to include magnetic spin force is not straightforward. We look at non-covariant particle dynamics, and present a short introduction to dynamics of (neutral) particles hit by a laser pulse of arbitrary shape.

physics.class-ph↗

From Strangeness Enhancement to Quark-Gluon Plasma Discovery

This is a short survey of signatures and characteristics of the quark-gluon plasma in the light of experimental results that have been obtained over the past three decades. In particular, we present an in-depth discussion of the strangeness observable, including a chronology of the experimental effort to detect QGP at CERN-SPS, BNL-RHIC, and CERN-LHC.

nucl-th↗

Measurement of the Lorentz-FitzGerald Body Contraction

A complete foundational discussion of acceleration in context of Special Relativity is presented. Acceleration allows the measurement of a Lorentz-FitzGerald body contraction created. It is argued that in the back scattering of a probing laser beam from a relativistic flying electron cloud mirror generated by an ultra-intense laser pulse, a first measurement of a Lorentz-FitzGerald body contraction is feasible.

physics.hist-ph↗

Classification of exoplanets according to density

Considering probability distribution as a function of the average density $\barρ$ computed for 424 extrasolar planets we identify three log-normal Gaussian population components. The two most populous components at $\barρ\simeq0.7$ g/cc and $\barρ\simeq7$ g/cc are the ice/gas giants and iron/rock super-Earths, respectively. A third component at $\barρ\simeq30$ g/cc is consistent with brown dwarfs, i.e., electron degeneracy supported objects. We note presence of several extreme density planetary objects.

astro-ph.EP↗

The hot Hagedorn Universe

In the context of the half-centenary of Hagedorn temperature and the statistical bootstrap model (SBM) we present a short account of how these insights coincided with the establishment of the hot big-bang model (BBM) and helped resolve some of the early philosophical difficulties. We then turn attention to the present day context and show the dominance of strong interaction quark and gluon degrees of freedom in the early stage, helping to characterize the properties of the hot Universe. We focus attention on the current experimental insights about cosmic microwave background (CMB) temperature fluctuation, and develop a much improved understanding of the neutrino freeze-out, in this way paving the path to the opening of a direct connection of quark-gluon plasma (QGP) physics in the early Universe with the QCD-lattice, and the study of the properties of QGP formed in the laboratory.

hep-ph↗

Probing QED Vacuum with Heavy Ions

We recall how nearly half a century ago the proposal was made to explore the structure of the quantum vacuum using slow heavy-ion collisions. Pursuing this topic we review the foundational concept of spontaneous vacuum decay accompanied by observable positron emission in heavy-ion collisions and describe the related theoretical developments in strong fields QED.

nucl-th↗

Hagedorn legacy

These remarks open the one-day session "50 years of Hagedorn's Temperature and the Statistical Bootstrap Model". These developments set the path at CERN towards the discovery of Quark-Gluon Plasma in the year 2000.

physics.hist-ph↗

Dynamical Emergence of the Universe into the False Vacuum

We study how the hot Universe evolves and acquires the prevailing vacuum state, demonstrating that in specific conditions which are believed to apply, the Universe becomes frozen into the state with the smallest value of Higgs vacuum field $v=\langle h\rangle$, even if this is not the state of lowest energy. This supports the false vacuum dark energy $Λ$-model. Under several likely hypotheses we determine the temperature in the evolution of the Universe at which two vacuua $v_1, v_2$ can swap between being true and false. We evaluate the dynamical surface pressure on domain walls between low and high mass vaccua due to the presence of matter and show that the low mass state remains the preferred vacuum of the Universe.

astro-ph.CO↗