Progress in Anisotropic Plasma Physics (original) (raw)

Strongly and weakly unstable anisotropic quark-gluon plasma

Physical Review D, 2005

Using explicit solutions of the QCD transport equations, we derive an effective potential for an anisotropic quark-gluon plasma which under plausible assumptions holds beyond the Hard Loop approximation. The configurations, which are unstable in the linear response approach, are characterized by a negative quadratic term of the effective potential. The signs of higher order terms can be either negative or positive, depending on the parton momentum distribution. In the case of a Gaussian momentum distribution, the potential is negative and unbound from below. Therefore, the modes, which are unstable for gauge fields of small amplitude, remain unstable for arbitrary large amplitudes. We also present an example of a momentum distribution which gives a negative quadratic term of the effective potential but the whole potential has a minimum and it grows for sufficiently large gauge fields. Then, the system is weakly unstable. The character of the instability is important for the dynamical evolution of the plasma system. * Electronic address: cristina.manuel@ific.uv.es † Electronic address: mrow@fuw.edu.pl 1 The term 'parton' is used to denote a fermionic (quark) or bosonic (gluon) excitation of the quark-gluon plasma. 2 Although we consider anisotropic systems, the characteristic momentum in all directions is assumed to be of the same order.

Dynamics of quark-gluon-plasma instabilities in discretized hard-loop approximation

Journal of High Energy Physics, 2005

Non-Abelian plasma instabilities have been proposed as a possible explanation for fast isotropization of the quark-gluon plasma produced in relativistic heavy-ion collisions. We study the real-time evolution of these instabilities in non-Abelian plasmas with a momentum-space anisotropy using a hard-loop effective theory that is discretized in the velocities of hard particles. We extend our previous results on the evolution of the most unstable modes, which are constant in directions transverse to the direction of anisotropy, from gauge group SU(2) to SU(3). We also present first full 3+1-dimensional simulation results based on velocity-discretized hard loops. In contrast to the effectively 1+1-dimensional transversely constant modes we find subexponential behavior at late times.

QCD plasma instabilities and isotropization

Physics Letters B, 2005

We solve the coupled Wong Yang-Mills equations for both U (1) and SU (2) gauge groups and anisotropic particle momentum distributions numerically on a lattice. For weak fields with initial energy density much smaller than that of the particles we confirm the existence of plasma instabilities and of exponential growth of the fields which has been discussed previously. Also, the SU (2) case is qualitatively similar to U (1), and we do find significant "abelianization" of the non-Abelian fields during the period of exponential growth. However, the effect nearly disappears when the fields are strong. This is because of the very rapid isotropization of the particle momenta by deflection in a strong field on time scales comparable to that for the development of Yang-Mills instabilities. This mechanism for isotropization may lead to smaller entropy increase than collisions and multiplication of hard gluons, which is interesting for the phenomenology of high-energy heavy-ion collisions.

The quark–gluon plasma: collective dynamics and hard thermal loops

Physics Reports, 2002

We present a unified description of the high temperature phase of QCD, the so-called quark-gluon plasma, in a regime where the effective gauge coupling g is sufficiently small to allow for weak coupling calculations. The main focuss is the construction of the effective theory for the collective excitations which develop at a typical scale gT , which is well separated from the typical energy of single particle excitations which is the temperature T. We show that the short wavelength thermal fluctuations, i.e., the plasma particles, provide a source for long wavelength oscillations of average fields which carry the quantum numbers of the plasma constituents, the quarks and the gluons. To leading order in g, the plasma particles obey simple gauge-covariant kinetic equations, whose derivation from the general Dyson-Schwinger equations is outlined. By solving these equations, we effectively integrate out the hard degrees of freedom, and are left with an effective theory for the soft collective excitations. As a by-product, the "hard thermal loops" emerge naturally in a physically transparent framework. We show that the collective excitations can be described in terms of classical fields, and develop for these a Hamiltonian formalism. This can be used to estimate the effect of the soft thermal fluctuations on the correlation functions. The effect of collisions among the hard particles is also studied. In particular we discuss how the collisions affect the lifetimes of quasiparticle excitations in a regime where the mean free path is comparable with the range of the relevant interactions. Collisions play also a decisive role in the construction a Member of CNRS.

QCD plasma instabilities and bottom-up thermalization

Journal of High Energy Physics, 2003

We study the role of QCD plasma instabilities in non-equilibrium quark-gluon plasmas. First, we argue that such instabilities must drastically modify the "bottom-up" thermalization scenario for heavy-ion collisions. Second, we discuss conditions for the existence of instabilities in a more general context than previously treated in the QCD literature. We also give a thorough qualitative review of the origin of instabilities. We discuss some mechanisms whereby the growth of plasma instabilities saturates. Finally, we solve explicitly for instabilities and their growth rates for two extreme cases of anisotropic non-equilibrium plasmas that can be treated relatively simply and analytically: f (p) = F (p ⊥ ) δ(p z ) and f (p) = F (p z ) δ (2) (p ⊥ ), where f (p) is the distribution of particles in momentum space.

Hard-loop dynamics of non-abelian plasma instabilities

Nuclear Physics A, 2006

I discuss recent advances in the understanding of non-equilibrium gauge field dynamics in plasmas which have particle distributions which are locally anisotropic in momentum space. In contrast to locally isotropic plasmas such anisotropic plasmas have a spectrum of soft unstable modes which are characterized by exponential growth of transverse (chromo)-magnetic fields at short times. The long-time behavior of such instabilities depends on whether or not the gauge group is abelian or non-abelian. Here I will report on recent numerical simulations which attempt to determine the long-time behavior of an anisotropic non-abelian plasma within hardloop effective theory.

Non-Abelian plasma instabilities for extreme anisotropy

Physical Review D, 2007

Thermalization of quark-gluon plasmas in heavy-ion collisions is a difficult theoretical problem. One theoretical goal has been to understand the physics of thermalization in the relatively simplifying limit of arbitrarily high energy collisions, where the running coupling α s is weak. One of the current roadblocks to achieving this goal is lack of knowledge about the behavior of plasma instabilities when particle distributions are highly anisotropic. In particular, it has not been known how the magnetic fields generated by plasma instabilities scale with anisotropy. In this paper, we use numerical simulations in a first attempt to determine this scaling.

Magnetic field-induced anisotropic interaction in heavy quark bound states

arXiv: High Energy Physics - Phenomenology, 2020

We have investigated how a strong magnetic field (B) could decipher the anisotropic interaction in heavy quark ($Q$) and antiquark ($\bar Q$) bound states through the perturbative thermal QCD in real-time formalism. So we thermalize Schwinger propagator for quarks in LLL and the Feynman propagator for gluons to calculate the gluon self-energy. For the quark-loop contribution to the self-energy, the medium does not have any temperature correction and the vacuum term gives rise an anisotropic term whereas the gluon-loop yields temperature correction. This finding in quark-loop contribution corroborates the equivalence of a massless QED in (1+1)-dimension with the massless thermal QCD in strong B, which (quark sector) is reduced to (1+1)-dimension (longitudinal). Thus the permittivity of the medium behaves like as a tensor. Thus the permittivity of medium makes the QbarQQ \bar QQbarQ potential anisotropic, which resembles with a contemporary results found in lattice studies. As a result, poten...

Metastable States in Quark-Gluon Plasma

2010

We study the meta-stable states in high temperature phase of QCD characterised by nonzero expectation values for the imaginary part of the Polyakov loop. We consider Nf=2,3N_f= 2, 3Nf=2,3 dynamical staggered quarks, and carry out simulations at various values of the coupling beta\betabeta to observe these states. In particular, we find the value of the coupling ($\beta_m$) above which the meta-stable states appear. The resulting value of betam\beta_mbetam corresponds to temperature Tmgtrsim750T_m \gtrsim 750Tmgtrsim750MeV for Nf=2N_f=2Nf=2.