2,596 research outputs found
A gauge field theory of fermionic Continuous-Spin Particles
In this letter, we suggest a local covariant action for a gauge field theory
of fermionic Continuous-Spin Particles (CSPs). The action is invariant under
gauge transformations without any constraint on both the gauge field and the
gauge transformation parameter. The Fang-Fronsdal equations for a tower of
massless fields with all half-integer spins arise as a particular limit of the
equation of motion of fermionic CSPs.Comment: 8 pages, no figure. Due to the constructive contribution of X.
Bekaert in this letter, his name is added as a new author. This version of
the paper accepted for publication in PLB(2016
How higher-spin gravity surpasses the spin two barrier: no-go theorems versus yes-go examples
Aiming at non-experts, we explain the key mechanisms of higher-spin
extensions of ordinary gravity. We first overview various no-go theorems for
low-energy scattering of massless particles in flat spacetime. In doing so we
dress a dictionary between the S-matrix and the Lagrangian approaches,
exhibiting their relative advantages and weaknesses, after which we high-light
potential loop-holes for non-trivial massless dynamics. We then review positive
yes-go results for non-abelian cubic higher-derivative vertices in constantly
curved backgrounds. Finally we outline how higher-spin symmetry can be
reconciled with the equivalence principle in the presence of a cosmological
constant leading to the Fradkin--Vasiliev vertices and Vasiliev's higher-spin
gravity with its double perturbative expansion (in terms of numbers of fields
and derivatives).Comment: LaTeX, 50 pages, minor changes, many refs added; version accepted for
publication in Reviews of Modern Physic
Evolution of multi-gap superconductivity in the atomically thin limit: Strain-enhanced three-gap superconductivity in monolayer MgB
Starting from first principles, we show the formation and evolution of
superconducting gaps in MgB at its ultrathin limit. Atomically thin MgB
is distinctly different from bulk MgB in that surface states become
comparable in electronic density to the bulk-like - and -bands.
Combining the ab initio electron-phonon coupling with the anisotropic
Eliashberg equations, we show that monolayer MgB develops three distinct
superconducting gaps, on completely separate parts of the Fermi surface due to
the emergent surface contribution. These gaps hybridize nontrivially with every
extra monolayer added to the film, owing to the opening of additional coupling
channels. Furthermore, we reveal that the three-gap superconductivity in
monolayer MgB is robust over the entire temperature range that stretches up
to a considerably high critical temperature of 20 K. The latter can be boosted
to 50 K under biaxial tensile strain of 4\%, which is an enhancement
stronger than in any other graphene-related superconductor known to date.Comment: To appear in Phys. Re
Strong obstruction of the Berends-Burgers-van Dam spin-3 vertex
In the eighties, Berends, Burgers and van Dam (BBvD) found a nonabelian cubic
vertex for self-interacting massless fields of spin three in flat spacetime.
However, they also found that this deformation is inconsistent at higher order
for any multiplet of spin-three fields. For arbitrary symmetric gauge fields,
we severely constrain the possible nonabelian deformations of the gauge algebra
and, using these results, prove that the BBvD obstruction cannot be cured by
any means, even by introducing fields of spin higher (or lower) than three.Comment: 19 pages, no figur
Tensor gauge fields in arbitrary representations of GL(D,R): II. Quadratic actions
Quadratic, second-order, non-local actions for tensor gauge fields
transforming in arbitrary irreducible representations of the general linear
group in D-dimensional Minkowski space are explicitly written in a compact form
by making use of Levi-Civita tensors. The field equations derived from these
actions ensure the propagation of the correct massless physical degrees of
freedom and are shown to be equivalent to non-Lagrangian local field equations
proposed previously. Moreover, these actions allow a frame-like reformulation a
la MacDowell-Mansouri, without any trace constraint in the tangent indices.Comment: LaTeX, 53 pages, no figure. Accepted for publication in
Communications in Mathematical Physics. Local Fierz-Pauli programme achieved
by completing the analysis of Labastid
Bosonic Massless Higher Spin Fields from Matrix Model
We study matrix models as a new approach to formulate massless higher spin
gauge field theory. As a first step in this direction, we show that the free
equation of motion of bosonic massless higher spin gauge fields can be derived
from that of a matrix model.Comment: 19pages, no figures, one reference adde
Current Exchanges for Reducible Higher Spin Multiplets and Gauge Fixing
We compute the current exchanges between triplets of higher spin fields which
describe reducible representations of the Poincare group. Through this
computation we can extract the propagator of the reducible higher spin fields
which compose the triplet. We show how to decompose the triplet fields into
irreducible HS fields which obey Fronsdal equations, and how to compute the
current-current interaction for the cubic couplings which appear in
ArXiv:0708.1399 [hep-th] using the decomposition into irreducible modes. We
compare this result with the same computation using a gauge fixed (Feynman)
version of the triplet Lagrangian which allows us to write very simple HS
propagators for the triplet fields.Comment: 26 pages, 1 table; v3 some clarifications and references added, typos
corrected. Published versio
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