5,230 research outputs found
Dynamic RKKY interaction in graphene
The growing interest in carbon-based spintronics has stimulated a number of
recent theoretical studies on the RKKY interaction in graphene, based on which
the energetically favourable alignment between magnetic moments embedded in
this material can be calculated. The general consensus is that the strength of
the RKKY interaction in graphene decays as 1/D3 or faster, where D is the
separation between magnetic moments. Such an unusually fast decay for a
2-dimensional system suggests that the RKKY interaction may be too short ranged
to be experimentally observed in graphene. Here we show in a mathematically
transparent form that a far more long ranged interaction arises when the
magnetic moments are taken out of their equilibrium positions and set in
motion. We not only show that this dynamic version of the RKKY interaction in
graphene decays far more slowly but also propose how it can be observed with
currently available experimental methods.Comment: 7 pages, 2 figures, submitte
An all-order proof of the equivalence between Gribov's no-pole and Zwanziger's horizon conditions
The quantization of non-Abelian gauge theories is known to be plagued by
Gribov copies. Typical examples are the copies related to zero modes of the
Faddeev-Popov operator, which give rise to singularities in the ghost
propagator. In this work we present an exact and compact expression for the
ghost propagator as a function of external gauge fields, in SU(N) Yang-Mills
theory in the Landau gauge. It is shown, to all orders, that the condition for
the ghost propagator not to have a pole, the so-called Gribov's no-pole
condition, can be implemented by demanding a nonvanishing expectation value for
a functional of the gauge fields that turns out to be Zwanziger's horizon
function. The action allowing to implement this condition is the
Gribov-Zwanziger action. This establishes in a precise way the equivalence
between Gribov's no-pole condition and Zwanziger's horizon condition.Comment: 11 pages, typos corrected, version accepted for publication in Phys.
Lett.
A study of the Higgs and confining phases in Euclidean SU(2) Yang-Mills theories in 3d by taking into account the Gribov horizon
We study SU(2) three-dimensional Yang-Mills theories in presence of Higgs
fields in the light of the Gribov phenomenon. By restricting the domain of
integration in the functional integral to the first Gribov horizon, we are able
to discuss a kind of transition between the Higgs and the confining phase in a
semi-classical approximation. Both adjoint and fundamental representation for
the Higgs field are considered, leading to a different phase structure.Comment: 12 pages. Version accepted for publication in the EPJ
Implementing the Gribov-Zwanziger framework in N=1 Super Yang-Mills in the Landau gauge
The Gribov-Zwanziger framework accounting for the existence of Gribov copies
is extended to N=1 Super Yang--Mills theories quantized in the Landau gauge. We
show that the restriction of the domain of integration in the Euclidean
functional integral to the first Gribov horizon can be implemented in a way to
recover non-perturbative features of N=1 Super Yang--Mills theories, namely:
the existence of the gluino condensate as well as the vanishing of the vacuum
energy.Comment: 19 pages, no figure
Renormalization aspects of N=1 Super Yang-Mills theory in the Wess-Zumino gauge
The renormalization of N=1 Super Yang-Mills theory is analysed in the
Wess-Zumino gauge, employing the Landau condition. An all orders proof of the
renormalizability of the theory is given by means of the Algebraic
Renormalization procedure. Only three renormalization constants are needed,
which can be identified with the coupling constant, gauge field and gluino
renormalization. The non-renormalization theorem of the gluon-ghost-antighost
vertex in the Landau gauge is shown to remain valid in N=1 Super Yang-Mills.
Moreover, due to the non-linear realization of the supersymmetry in the
Wess-Zumino gauge, the renormalization factor of the gauge field turns out to
be different from that of the gluino. These features are explicitly checked
through a three loop calculation.Comment: 15 pages, minor text improvements, references added. Version accepted
for publication in the EPJ
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