77,829 research outputs found
Marginal Fermi liquid behavior from 2d Coulomb interaction
A full, nonperturbative renormalization group analysis of interacting
electrons in a graphite layer is performed, in order to investigate the
deviations from Fermi liquid theory that have been observed in the experimental
measures of a linear quasiparticle decay rate in graphite. The electrons are
coupled through Coulomb interactions, which remain unscreened due to the
semimetallic character of the layer. We show that the model flows towards the
noninteracting fixed-point for the whole range of couplings, with logarithmic
corrections which signal the marginal character of the interaction separating
Fermi liquid and non-Fermi liquid regimes.Comment: 7 pages, 2 Postscript figure
Herschel-ATLAS: Blazars in the science demonstration phase field
To investigate the poorly constrained sub-mm counts and spectral properties of blazars we searched for these in the Herschel-ATLAS (H-ATLAS) science demonstration phase (SDP) survey catalog.
We cross-matched 500 μm sources brighter than 50 mJy with the FIRST radio catalogue. We found two blazars, both previously known. Our study is among the first blind blazar searches at sub-mm wavelengths, i.e., in the spectral regime where little is still known about the blazar SEDs, but where the synchrotron peak of the most luminous blazars is expected to occur. Our early results are consistent with educated extrapolations of lower frequency counts and question indications of substantial spectral curvature downwards and of spectral upturns at mm wavelengths. One of the two blazars is identified with a Fermi/LAT γ-ray source and a WMAP source. The physical parameters of the two blazars are briefly discussed. These observations demonstrate that the H-ATLAS survey will provide key information about the physics of blazars and their contribution to sub-mm counts
Reflection formulas for order derivatives of Bessel functions
From new integral representations of the -th derivative of Bessel
functions with respect to the order, we derive some reflection formulas for the
first and second order derivative of and % Y_{\nu
}\left( t\right) for integral order, and for the -th order derivative of
and for arbitrary real
order. As an application of the reflection formulas obtained for the first
order derivative, we extend some formulas given in the literature to negative
integral order. Also, as a by-product, we calculate an integral which does not
seem to be reported in the literature.Comment: arXiv admin note: text overlap with arXiv:1808.0560
Renormalization group approach to chiral symmetry breaking in graphene
We investigate the development of a gapped phase in the field theory of Dirac
fermions in graphene with long-range Coulomb interaction. In the large-N
approximation, we show that the chiral symmetry is only broken below a critical
number of two-component Dirac fermions , that is exactly half
the value found in quantum electrodynamics in 2+1 dimensions. Adopting
otherwise a ladder approximation, we give evidence of the existence of a
critical coupling at which the anomalous dimension of the order parameter of
the transition diverges. This result is consistent with the observation that
chiral symmetry breaking may be driven by the long-range Coulomb interaction in
the Dirac field theory, despite the divergent scaling of the Fermi velocity in
the low-energy limit.Comment: 6 pages, 4 figures, extended version with technical detail
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