2,496 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
Orbital and Pauli limiting effects in heavily doped BaKFeAs
We investigated the thermodynamic properties of the Fe-based lightly
disordered superconductor BaKFeAs in external
magnetic field H applied along the FeAs layers (H//ab planes). The
superconducting (SC) transition temperature for this doping level is T =
6.6 K. Our analysis of the specific heat C(T,H) measured for T < T implies
a sign change of the superconducting order parameter across different Fermi
pockets. We provide experimental evidence for the three components
superconducting order parameter. We find that all three components have values
which are comparable with the previously reported ones for the stochiometric
compound KFeAs. Our data for C(T,H) and resistivity rho(T,H) can be
interpreted in favor of the dominant orbital contribution to the pair-breaking
mechanism at low fields, while Pauli limiting effect dominates at high fields,
giving rise to a gapless superconducting state with only the leading non-zero
gap.Comment: 7 pages, 5 figure
Performance models of access latency in cloud storage systems
Access latency is a key performance metric for cloud storage systems and has great impact on user experience, but most papers focus on other performance metrics such as storage overhead, repair cost and so on. Only recently do some models argue that coding can reduce access latency. However, they are developed for special scenarios, which may not reflect reality. To fill the gaps between existing work and practice, in this paper, we propose a more practical model to measure access latency. This model can also be used to compare access latency of different codes used by different companies. To the best of our knowledge, this model is the first to provide a general method to compare access latencies of different erasure codes.postprin
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