arXiv subjects
Publications and source records attributed to B. Muller.
We argue that the quantized non-Abelian gauge theory can be obtained as the infrared limit of the corresponding classical gauge theory in a higher dimension. We show how the transformation from classical to quantum field theory emerges, and calculate Planck's constant from quantities defined in the underlying classical gauge theory.
We discuss characteristic experimental signatures related to the mechanism of DCC formation triggered by the chiral U(1) anomaly in relativistic heavy ion collisions. We predict an enhancement of the fraction of neutral pions compared with all pions in the direction perpendicular to the scattering plane. To quantify the effect on the angular distribution of neutral pions, we compute the elliptic flow parameter $v_2$ as a function of the transverse momentum. We find values of order -0.05 at small momenta for neutral pions. We also compute the $v_2$ parameter for inclusive photons, which is easier to measure, and confirmed that the negative a few percent effect prevails in this observable.
We discuss characteristic experimental signatures related to the formation of domains of disoriented chiral condensate (DCC) triggered by the axial anomaly in relativistic heavy ion collisions. We predict that the enhancement of the fraction of neutral pions compared to all pions depends on the angle of emission with respect to the scattering plane and is concentrated at small transverse momentum and small rapidity in the center-of-mass frame. The anisotropy with respect to the reaction plane is also observable in the inclusive photon distribution.
The magnitude of the local fluctuations of the net baryon number and electric charge differs widely between the confined and deconfined phases, and the difference is partially frozen at an early stage in relativistic heavy ion collisions. These fluctuations may thus be useful probes of the temporary formation of a deconfined state in such collisions.
We argue that higher dimensional classical, nonabelian gauge theory may lead to a lower dimensional quantum field theory due to its inherent chaotic dynamics which acts like stohastic quantization. The dimensional reduction is based upon magnetic screening effects analagous to that in nonabelian plasmas.
Different treatments for the inclusion of higher-order perturbative QCD corrections in parton based transport models of relativistic heavy-ion collisions are studied and their influence on experimental observables is investigated. At RHIC, particle multiplicities may vary by more than 30%, depending on the correction scheme. A detailed analysis of the squared relative momentum transfers to be expected in parton (re)scatterings at RHIC casts doubt on the applicability of pQCD based transport approaches at the SPS and rules out the application of higher-order correction schemes based on a rescaling of the relative squared momentum transfers in the running coupling constant at all energies.
We discuss the effect of chiral anomaly as a possible mechanism for triggering formation of domains of disoriented chiral condensate (DCC) in relativistic heavy ion collisions. The anomalous $π^0 \to 2 γ$ coupling and the strong, Lorentz contracted electromagnetic fields of the heavy ions combine to produce the ``anomaly kick'' to the field configuration of the neutral pion field. We implement the effect of anomaly kick in our numerical simulation of the linear sigma model in a schematic way which preserves its characteristic features: the effect is coherent over a large region of space but is opposite in sign above and below the ion scattering plane. We demonstrate by detailed simulations with longitudinal expansion that the DCC domain formation is dramatically enhanced by the anomaly kick in spite of its small absolute magnitude. We examine the behavior of various physical quantities such as pion fields, the axial vector currents, and their correlation functions. Our results also provide useful insight into the mechanism and properties of DCC domain formation, in general. Finally, we discuss some experimental observables which can signal the anomaly induced formation of DCC.
We give two reasons why we believe that non-central ultrarelativistic heavy ion collisions are the place to look for the disoriented chiral condensates (DCC). First, we argue that the most probable quench scenario for the formation of DCC requires non-central collisions. Second, we show by numerical simulations that strong electromagnetic fields of heavy ions can exert a surprisingly large effect on the DCC domain formation through the chiral anomaly. The effect again requires non-central collisions. Interestingly, the result of simulations is consistent with the formation of correlated two domains of the chiral condensate, which are aligned in space, perpendicular to the scattering plane, but misaligned in isospin space.
We propose a formulation of the long-distance dynamics of gauge theories at finite temperature on a lattice in Minkowski space, including the effects of hard thermal loops on the dynamics of the long wavelength modes. Our approach is based on the dual classical limits of quantum fields as waves and particles in the infrared and ultraviolet limits, respectively. It exhibits manifest invariance under space-dependent lattice gauge transformations and conserves Gauss' law.
We investigate thermalization processes occurring at different time scales in the Yang-Mills-Higgs system at high temperatures. We determine the largest Lyapunov exponent associated with the gauge fields and verify its relation to the perturbatively calculated damping rate of a static gauge boson.
We investigate the restoration of spontaneously broken gauge symmetry in collisions of gauge boson wave packets in the SU(2) Higgs model.
We present numerical simulations of colliding wave packets in spontaneously broken SU(2) Yang-Mills-Higgs theory. Compared with pure Yang-Mills theory, introducing the Higgs field leads to new aspects in the dynamics of the system. The evolution of the gauge field and the Higgs field is investigated as a function of the amplitude of the wave packets and of the mass ratio of the Higgs and the gauge boson. We find regions in our parameter space in which initial wave packets scatter into final configurations with dramatically different momentum distributions.
The chirally symmetric quark-gluon plasma produced in energetic heavy-ion collisions is predicted to supercool at the late stages of its evolution. The thermal energy is then transformed into the potential energy associated with an energetically unfavorable field configuration. Since the system is in an unstable state it eventually rolls down to the true minimum of the effective chiral potential. When this motion is described in terms of the sigma-model, we find that the energy of the coherent $σ-$field is very efficiently converted into pionic excitations due to anharmonic oscillations around this minimum. The system is expected to partially thermalize before its disintegration.
We argue on a basis of a simple few mode model of SU(2) Yang-Mills theory that the color off-diagonal coupling of the soft plasmon to hard thermal excitations of the gauge field drives the collective plasma oscillations into chaotic motion despite the presence of the plasmon mass.
We discuss the results of numerical simulations of colliding wavepackets in $SU(2)$ Yang--Mills theory. We investigate their behavior as a function of amplitude and momentum distribution. We find regions in our parameter space in which initial wave packets scatter into final configurations with dramatically different momentum distributions. These results constitute new classical trajectories with multiparticle boundary conditions. We explain their relevance for the calculation of scattering amplitudes in the semiclassical approximation. Finally, we give directions for future work.