3,558 research outputs found
Non-perturbative Approach to Equation of State and Collective Modes of the QGP
We discuss a non-perturbative -matrix approach to investigate the
microscopic structure of the quark-gluon plasma (QGP). Utilizing an effective
Hamiltonian which includes both light- and heavy-parton degrees of freedoms.
The basic two-body interaction includes color-Coulomb and confining
contributions in all available color channels, and is constrained by
lattice-QCD data for the heavy-quark free energy. The in-medium -matrices
and parton spectral functions are computed selfconsistently with full account
of off-shell properties encoded in large scattering widths. We apply the
-matrices to calculate the equation of state (EoS) for the QGP, including a
ladder resummation of the Luttinger-Ward functional using a matrix-log
technique to account for the dynamical formation of bound states. It turns out
that the latter become the dominant degrees of freedom in the EoS at low QGP
temperatures indicating a transition from parton to hadron degrees of freedom.
The calculated spectral properties of one- and two-body states confirm this
picture, where large parton scattering rates dissolve the parton quasiparticle
structures while broad resonances start to form as the pseudocritical
temperature is approached from above. Further calculations of transport
coefficients reveal a small viscosity and heavy-quark diffusion coefficient.Comment: 10 pages, 8 figures, proceedings of XLVII International Symposium on
Multiparticle Dynamics (ISMD2017
Spin-transfer torques in anti-ferromagnetic metals from first principles
In spite of the absence of a macroscopic magnetic moment, an anti-ferromagnet
is spin-polarized on an atomic scale. The electric current passing through a
conducting anti-ferromagnet is polarized as well, leading to spin-transfer
torques when the order parameter is textured, such as in anti-ferromagnetic
non-collinear spin valves and domain walls. We report a first principles study
on the electronic transport properties of anti-ferromagnetic systems. The
current-induced spin torques acting on the magnetic moments are comparable with
those in conventional ferromagnetic materials, leading to measurable angular
resistances and current-induced magnetization dynamics. In contrast to
ferromagnets, spin torques in anti-ferromagnets are very nonlocal. The torques
acting far away from the center of an anti-ferromagnetic domain wall should
facilitate current-induced domain wall motion.Comment: The paper has substantially been rewritten, 4 pages, 5 figure
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