6,221 research outputs found
Dirac equation for quasi-particles in graphene and quantum field theory of their Coulomb interaction
There is evidence for existence of massless Dirac quasi-particles in
graphene, which satisfy Dirac equation in (1+2) dimensions near the so called
Dirac points which lie at the corners at the graphene's brilluoin zone. We
revisit the derivation of Dirac equation in (1+2) dimensions obeyed by
quasiparticles in graphene near the Dirac points. It is shown that parity
operator in (1+2) dimensions play an interesting role and can be used for
defining "conserved" currents resulting from the underlying Lagrangian for
Dirac quasi-particles in graphene which is shown to have U_{A}(1)*U_{B}(1)
symmetry. Further the quantum field theory (QFT) of Coulomb interaction of 2D
graphene is developed and applied to vacuum polarization and electron self
energy and the renormalization of the effective coupling g of this interaction
and Fermi velocity which has important implications in the
renormalization group analysis of g and v_{f}.Comment: 10 pages, some typos have been corrected, some references have been
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Study of shear viscosity of SU (2)-gluodynamics within lattice simulation
This paper is devoted to the study of two-point correlation function of the
energy-momentum tensor T_{12}T_{12} for SU(2)-gluodynamics within lattice
simulation of QCD. Using multilevel algorithm we carried out the measurement of
the correlation function at the temperature T/T_c = 1.2. It is shown that
lattice data can be described by spectral functions which interpolate between
hydrodynamics at low frequencies and asymptotic freedom at high frequencies.
The results of the study of spectral functions allowed us to estimate the ratio
of shear viscosity to the entropy density {\eta}/s = 0.134 +- 0.057.Comment: 7 pages, 3 figure
Lattice field theory simulations of Dirac semimetals
In this paper the observed Dirac semimetals NaBi and CdAs are
studied within lattice simulation. We formulate lattice field theory with
rooted staggered fermions on anisotropic lattice. It is shown that in the limit
of zero temporal lattice spacing this theory reproduces low energy effective
theory of Dirac semimetals. Using this lattice theory we study the phase
diagram of Dirac semimetals in the plane effective coupling constant--Fermi
velocity anisotropy. Within the formulated theory the results are practically
volume independent in contrast with our previous study. Our results confirm our
previous finding that within the Dirac model with bare Coulomb interaction both
NaBi and CdAs lie deep in the insulator phase.Comment: 11 pages, 5 figures, 2 tables, typo in Eq. (20) corrected, Appendix
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